Introduction
Collision sports such as rugby union and rugby league (i. e. rugby) have
different demands compared to many other team sports (e. g. soccer, hockey,
cricket) due to multiple contact/collision game events [1 ]. Athletes require well-developed specific physical qualities to perform
optimally [2 ] and mitigate the risk of injury. These
physical qualities are typically developed through well-planned, periodized training
programs [3 ]. The preparation, maintenance and recovery of
athletes is relatively well understood within a typical season [4 ]
[5 ], and practitioners have a wealth of
experience in supporting athletes under normal circumstances.
In 2020, the spread of a coronavirus disease (COVID-19) resulted in a worldwide
pandemic. As a consequence social measures have been implemented that preclude sports
competition and many aspects of team sports training. A primary concern, and the motive
for this review, is that development and maintenance of key physical qualities
(e. g. strength, power, high-speed running ability, acceleration, deceleration
and change of direction), game-specific contact skills (e. g. tackling) and
decision-making ability, is challenged during physical distancing and movement
restriction measures as a consequence of COVID-19. Players are unlikely to be able
to
train together as teams in any form, access training facilities or public gymnasiums,
nor have routine access to coaching, conditioning and medical staff. Indeed, the
majority of elite athletes will be attempting to train at home within the constraints
of
the equipment and space that they have available to them. Some players will have access
to excellent training facilities in their home, some will have access to limited
facilities, and some might have no access to equipment or adequate space at all. The
variation in training activities that athletes can undertake during a period of
restriction will likely present additional challenges when planning the resumption
of
team training. As such, the specific needs of each individual athlete will require
consideration upon the return of training and competition.
Although the likely impact of the COVID-19 pandemic is unprecedented in scale, there
are
examples of the consequences of enforced restriction of access to training on returning
to sport. For example, following a 20-week lockout in the National Football League
in
2011, on returning to competition, there were more frequent soft tissue injuries [6 ]
[7 ]. Therefore, with a focus
on rugby league and rugby union, the purpose of this review is to examine the available
evidence related to the following: potential changes to physical qualities and function
during the period of modified training, strategies to mitigate this decline in function,
and the time taken to return players and teams to “game ready” status.
It is anticipated that many of the principles outlined in this review will be applicable
to a broader range of collision sports (e. g. American football, Australian
football). The final section provides practical recommendations that focus on restarting
these sports after an extended break from training.
Physical qualities for rugby
The demands of rugby require athletes to have high levels of lower-body and
upper-body strength and power [8 ]. Rugby players have
high levels of lean mass [9 ], in comparison to other
sports (e. g. soccer) [10 ], in addition to
well-developed aerobic and anaerobic running capacities [11 ]
[12 ]. Strength and power are related to
general athletic qualities (e. g. speed, acceleration and change of
direction) [13 ] and rugby-specific ones (e. g.
tackling) [14 ]
[15 ]. The
tackle and other contact events (e. g. ruck, maul, scrum) require high levels
of strength and power to overcome resistant forces from opposition players.
Within rugby league and rugby union, strength and power have been shown to vary
between age [16 ]
[17 ] and
playing position [2 ]
[18 ].
Professional rugby league players have been shown to have greater strength and power
than semi-professional or amateur players [17 ].
Strength appears similar for professional and semi-professional rugby union players,
whereas professional players have greater power [8 ].
Furthermore, stronger players with higher levels of aerobic fitness have been shown
to recover more quickly following rugby league match play [19 ].
Considerations for injury in relation to enforced modified training
There are numerous conceptual models that identify risk factors for injury
(e. g. strength, training load, competition schedule, previous injury)
[(e. g. [20 ]
[21 ]). However, the evidence for proposed risk factors for injury in elite
sports settings is often not as clear as might be expected, perhaps because athletes
who are competing have usually reached an explicit or implicit minimum physical
requirement for participation at a given level of play.
There is evidence of an association between the strength of specific muscle groups
and overuse shoulder injuries in throwing sports [(e. g. [22 ]) as well as groin injuries in a range of sports
[(e. g. [23 ]). In the case of hamstring injury
risk, evidence of an association between strength and injury is mixed (for detailed
review see [24 ]), although a combination of performing
eccentric Nordic hamstring exercises [25 ] and regular
exposure to high-speed running [26 ]
[27 ]
[28 ] appears to be
protective against hamstring injuries.
A high proportion of injuries in collision sports is associated with contact
mechanisms, for example, the tackle is associated with ~50% of all
injuries in professional rugby union [29 ]
[30 ]. Even in a training environment, the greatest
incidence of injury is in full contact training [31 ].
Therefore the ability of tissues to withstand substantial acute external forces may
be key. In a prospective cohort study of professional rugby league players, those
with poorly developed high-speed running ability (hazard ratio (HR): 2.9, 95%
confidence interval (CI)=1.7–4.0) and upper-body strength (HR: 2.2,
95% CI=1.3–3.7) had a higher incidence of contact injury
[32 ].
A systematic literature review and meta-analysis [33 ]
identified six studies that have examined the effect of strength training
interventions on injury outcomes in military [34 ] and
elite [35 ]
[36 ], amateur
[36 ]
[37 ] and youth
[38 ]
[39 ] soccer. All
of the interventions reduced injuries, with 95% certainty of more than
halving injury risk (average reduction, 66%, 95% CI
52–6%). These findings provide compelling evidence of a role for
development of strength in injury prevention, although none of the studies were in
professional collision sports settings. Similarly, rugby-specific injury prevention
exercise programs that focus on strength, balance and proprioception [40 ] substantially reduced injury and concussion incidence
in cluster randomized controlled trials in youth [41 ]
and community adult [42 ] cohorts. Of particular
interest in the context of these studies is the potential importance of neck strength
in protecting against concussion [43 ].
A key concern arising from a period of enforced modified training due to COVID-19
is
that athletes cannot maintain physical qualities that likely protect against injury.
A twenty-week shutdown of the National Football League in 2011 was associated with
a
four-fold increase in Achilles tendon ruptures in the first 29 days of a condensed
return to competition period [6 ]. Over the subsequent
season, soft tissue injuries (considered to be conditioning-related injuries) were
higher than preceding or subsequent seasons [7 ]. In
professional rugby union, even after a short off-season typically lasting 4–5
weeks during which athletes have opportunities to train (e. g. access to gym
and other training facilities), there is a greater frequency and burden of training
injuries in the early, compared with later, period of pre-season ([Fig. 1 ]). This highlights one of the challenges when
athletes return following an extended period of enforced modified training.
Fig. 1 Incidence (a injuries per 1000 hours) and burden (b
days lost per 1000 hours) of training injuries during the pre-season and early
competition period in the English Premiership (2014–15 to
2018–19 seasons).
On resumption of competition, it is possible that multiple games per week are
scheduled to make up for the time lost. Limited time between matches during periods
of fixture congestion has been shown to be associated with more injuries in soccer
[44 ]. Clearly, the timing and structure of
reconditioning, and fixture scheduling upon resumption of the competitive season,
have the potential to impact on injury outcomes.
The concept of preparedness for training and/or competition has been
investigated in professional rugby union, with intermediate cumulative load over four
weeks showing a likely beneficial reduction in injury risk compared with low or high
four-week loads [45 ]. In the same study, sudden
increases (or spikes) in training load were shown to increase the risk of injury
[45 ]. Exposure to competitive matches also appears
to influence injury risk in professional rugby union, with involvement in less than
15 or more than 35 games over a 12-month period associated with a greater injury risk
than being involved in between 15 and 35 games [46 ]. An
extended period without competition will result in more players having played a low
number of games in 12 months, potentially increasing injury risk.
In returning players to competition, standard considerations around individual risk
factors will be important to consider. A potential positive related to a period of
modified training practices and no matches is that it may allow for prolonged rest,
which is rarely afforded to professional rugby players. Previous injury has
consistently been shown to increase subsequent injury risk [47 ], and there may be opportunity to focus on full recovery and
rehabilitation from previous injuries, although restricted access to appropriate
rehabilitation modalities might limit any positive impact. Considering that some
subsequent injuries are, in part, related to inadequate rehabilitation [47 ], individual management of athletes when returning to
full training is required. The Strategic Assessment of Risk and Risk Tolerance
(StARRT) framework may be helpful in this respect [48 ].
Some athletes may even have developed injuries during the period of restricted
training due to enforced changes in training type, timing, load and surface. A
further consideration is that athlete anxiety may be elevated by a number of facets
of an extended period of modified training due to COVID-19, which might impact on
injury risk when returning to play [49 ].
Under normal circumstances, most elite collision sports players will be conditioned
to a level that is protective against injury. However, a sustained period of enforced
modified training is likely to impact upon this conditioning, and is likely to result
in increased injury risk. It is important to consider strategies to mitigate losses
in physical function and to develop appropriate reconditioning strategies. These
should be considered on an athlete-by-athlete basis (e. g. training status
and injury history), sport-by-sport (e. g. the stage of the season), and
country-by-country (e. g. local government COVID-19 guidelines).
Potential changes in physiological characteristics in response to reductions in
training
Athletes’ musculoskeletal, respiratory and cardiovascular systems are
accustomed to a large volume and intensity of training stimulus, and any considerable
reduction in habitual stimuli will lead to a degree of physiological system and
tissue deconditioning, in turn reducing physical performance. There is limited
evidence regarding detraining in elite athletic populations, but principles of
deconditioning can be translated from human laboratory studies using extreme
experimental models such as limb immobilization (local disuse), bed rest (whole body
disuse) or reduced step count (moderate decreases in physical activity) in previously
‘healthy’ individuals [50 ]. Regardless
of the model, such studies reliably show that deconditioning is rapid and profound
[50 ].
Physical inactivity quickly leads to a myriad of interrelated cardiovascular
deconditioning responses. Experimental bedrest [51 ] and
short-term detraining in trained individuals [52 ]
decreases plasma volume, reduces baroreflex sensitivity, impairs the sensitivity with
which the vasculature can appropriately redistribute blood volume, interferes with
heart rate and blood pressure regulation, induces cardiac muscle atrophy and impairs
myocardial mechanics and stroke volume. Though the time course and severity of some
of these responses has not been precisely delineated, their integrated nature rapidly
impairs oxygen (and nutrient) delivery and tissue extraction, and can be expected
within < 4 weeks [52 ].
Skeletal muscle appears to be particularly susceptible to disuse-induced
deconditioning, with substantial impairments in markers of metabolic health
(reflecting declining muscle tissue quantity and quality) within just one week [53 ]
[54 ]. Disuse also almost
immediately reduces daily muscle protein synthesis rates [55 ], largely driven by a reduced ability of the inactive tissue to extract
dietary derived amino acids from the circulation following each meal [56 ] and utilize them for the construction of new proteins
[57 ]. The resulting loss of muscle mass can be
nearly 100 g after only two days of limb immobilization [55 ]. This increases to >250 g after one week, while one week of
bed-rest results in ~1.5 kg of whole body muscle loss [53 ]. Strikingly, muscle strength and force generating
capacity of a muscle group subjected to extreme disuse declines by
~1.5–2% per day [58 ], around
3-fold higher than the loss of muscle mass alone [59 ].
Muscles (groups) of a higher ‘training status’ within an
individual (i. e. higher habitual gravitational loading and mechanical
workload) typically decondition more rapidly. For example, the quadriceps atrophy
more rapidly than the hamstrings [60 ], and the large
postural and gross motor movement muscles of the legs, trunk and back atrophy more
quickly than the arms or other smaller muscles more attuned to fine movements [61 ]. In the event that disuse is brought about by any
type of acute injury, which would typically elicit a local and systemic inflammatory
response, muscle loss may be further accelerated over rest alone [62 ]. At the single fiber level, muscle disuse atrophy is
characterized by a decrease in cross-sectional area of all muscle fiber types, though
type II fibers appear particularly susceptible [63 ].
Skeletal muscle fiber atrophy is accompanied by considerable and disproportionately
large declines in function at the level of the muscle fiber. Despite this, some
evidence points towards deconditioning bringing about a ‘faster’
overall muscle phenotype, seemingly due to increased expression in the faster
isoforms of muscle myosin heavy chain across fiber types [64 ] rather than any ‘fiber type switching’.
Bone demineralization also occurs within a week of unloading [65 ], while tendon and connective tissues such as ligaments appear to be
more resistant to short-term muscle disuse [66 ]
[67 ], likely due to considerably lower protein turnover
rates. However, within a month of detraining, impairments in tendon and ligament
tensile strength and functionality can be expected [68 ]. Deconditioning of the tendon and ligament tissue also impacts on
metabolic and functional performance [66 ]
[67 ]. The crucial structural role of these collagen-rich
tissues within the musculoskeletal system (particularly within joint stabilization)
contributes heavily to movement and force generation, and therefore their
deconditioning also contributes to the degeneration of physical performance.
It is clear that the extreme models of disuse described above do not reflect the
experiences of athletes during most periods of training restriction. However,
case-study data on elite footballers suggest that injury induced periods of disuse
(e. g. Anterior cruciate ligament [ACL] surgery) lead to rapid tissue and
performance detriments that reflect the changes seen in laboratory trials
(e. g. loss of muscle mass and function, gain in fat tissue and alterations
in metabolic rate) [69 ]
[70 ]. Such effects are evident despite ‘best practice’ in
terms of nutritional and physical therapy countermeasures being applied. Furthermore,
elite athletes reducing training at the end of their competitive season can expect
rapid (within 5 weeks) declines in function, with the extent being related to the
level of withdrawal from training [71 ]. Such data
brings into stark focus the challenges that those involved in collision sports face,
if athletes undergo enforced periods of reduced or absent training load.
Maintaining muscle mass and function during enforced modified training
Fortunately, even in extreme physiological models of disuse, small amounts of
exercise can mitigate losses in muscle size and function. For example, eighty-four
days of bed rest in healthy men resulted in a 17% reduction in muscle size
and around 40% reduction in muscle strength and power [72 ]. However, when maximal concentric supine squats were
performed every third day, muscle size, strength and power were maintained [72 ]. In 60 days of bed rest, just three minutes of
“supine jumps” on 5–6 days per week maintained leg lean mass
and strength, compared with reductions of around 10% without exercise [73 ]. These examples are important in illustrating the
concept of mitigating losses in muscle mass and function during deconditioning, but
cannot be translated directly into sports settings.
A key question when access to training facilities is limited is whether heavy loads
during resistance training are required for the development, or maintenance, of
muscle mass and strength. During resistance exercise all motor units are recruited
at
momentary muscular failure, regardless of the load used [74 ]. In turn, rates of muscle protein synthesis for up to 24 hours after
exercise were similar when healthy men performed knee extension at 30% of one
repetition maximum (1RM) to failure compared with 90% 1RM to failure [75 ]. Taking this further, 10 weeks of knee-extension
training to failure at 30% 1RM and 80% 1RM in healthy young men
resulted in a similar change in quadriceps volume (hypertrophy), although gains in
strength as assessed by 1RM was significantly higher following training at
80% 1RM [76 ]. Other studies have also reported
similar hypertrophy responses in lower-load and higher-load resistance training, with
smaller gains in strength in lower-load training [77 ]
[78 ]. Furthermore, 12 weeks of whole-body
resistance training at either 30–50% 1RM or 75–90%
1RM in trained individuals resulted in similar changes in whole body lean mass [79 ]. However, in this study, 1RM strength was tested
every third week, essentially allowing a small amount of high load training in both
groups, and the strength outcomes were similar in all tests other than bench press
for which there was a small but significantly superior gain in the
75–90% 1RM group. Incorporating plyometric training might also be
beneficial, given that eccentric muscle actions have the potential to induce neural
adaptations, even in the absence of heavy loads, and that both concentric and
eccentric peak torque were better maintained during detraining following coupled
concentric and eccentric resistance training than concentric training alone [80 ]. Furthermore, although evidence is mixed,
meta-analysis showed small-to-moderate effects of plyometric training on maximal
strength in healthy adults [81 ].
Focusing on elite athletes, bench press and bench pull performance were assessed in
kayakers before and after five weeks of detraining following the World Championships
[71 ]. Seven athletes discontinued all training,
while seven completed a dramatically reduced volume of training that included one
resistance training session per week. In those that discontinued training, bench
press 1RM declined by 8.9% and bench pull by 7.8%, whereas in those
completing one resistance training session per week, declines in strength were much
smaller at 3.9% for bench press and 3.4% for bench pull. In addition,
those that discontinued training suffered a reduction in VO2 max of
11.3%, whereas those that reduced training volume to just two endurance
session per week experienced reductions of 5.6%. As a note of caution, in
athletes for whom strength and power are key attributes, the possible interference
effect of endurance training on strength adaptations should be considered [82 ]
[83 ]. This might be
particularly relevant when running and cycling activities are possible but access
to
resistance training facilities are limited.
From both a performance and injury prevention perspective, incorporating high-speed
running into training is likely to be beneficial. Sprint training has been
demonstrated to have positive impacts on hamstring architecture and sprint
performance [84 ], and regular exposure to maximal
running velocity has the potential to reduce injury risk [26 ]. The addition of both eccentric hamstring training [25 ] and plyometric training [85 ] may also be appropriate.
Practically, strength and power trained athletes may find it difficult to match the
loads needed to maintain size, strength and power. Performing resistance training
to
momentary failure, even with low loads, may mitigate some losses in muscle size, and
if some training with high resistance can be incorporated, even if not at the usual
frequency, it is possible to maintain strength characteristics. Alternatively,
plyometric exercises might provide a sufficient neural stimulus to contribute to the
maintenance of strength. Furthermore, given that neural adaptations might be retained
for longer than 12 weeks in trained individuals [64 ],
and that, even if this is not the case, neural adaptations occur early in response
to
resistance training [86 ], a focus on retaining as much
muscle mass as possible during restricted training is recommended, followed by the
re-introduction of high resistance in training once access to facilities and support
is possible.
Psychological considerations during enforced modified training
The training limitations arising from COVID-19 present a number of psychological
considerations that may influence preparation for, and subsequent return to, rugby
competition. These include the impact of confinement and isolation, deconditioning
effects, deterioration in skill execution/performance, and, the opportunity
for recovery and posttraumatic growth.
In addition to the psychological effects from periods of confinement and isolation
reported in the general public [87 ], such as
post-traumatic stress symptoms (i. e. depression, anxiety, confusion and
anger), athletes may be at further risk due to the impact on their athletic identity.
Athletic identity refers to the extent to which an individual identifies with their
role as an athlete [88 ]. Any challenges to the ability
to reinforce this identity through reduced capacity to train, play and achieve goals
(typically seen in injured or retired athletes) are associated with feelings of loss,
identity crisis and distress [89 ]. While engaging with
social support networks is seen as a key resource to cope with potential threats to
athletic identity arising from the restrictions, it is likely athletes will be
socially isolated from those who contribute most to supporting their sense of
athletic identity (teammates, staff, fan base). An extended period of isolation from
fellow teammates is also likely to impact upon the social and psychological group
process that underpin a team’s effectiveness to work together (i. e.
teamwork [90 ]) and subsequently perform.
In contrast to the physiology literature, limited research has examined the
psychological effects of a period of detraining or rest. While acute bouts of rest
(e. g. 2-week mid-season break) improve subjective perceptions of some
aspects of wellness, such as fatigue and muscle soreness [91 ], there is no evidence examining the chronic effects of deconditioning.
In the professional practice literature, Bompa and Buzzichelli [92 ] suggest that an abrupt cessation of training by
highly trained athletes creates a phenomenon known as detraining syndrome,
characterized by insomnia, anxiety, depression, alterations to cardiovascular
function, and loss of appetite. These symptoms are usually not deemed pathological
and can be reversed, if training is resumed within a short time; however, with
prolonged cessation, symptoms may become more pronounced.
The principle of reversibility dictates that athletes lose the beneficial effects
of
training on cessation of or reduction in such activities [93 ]. A decline in skill execution/performance may therefore be
expected from a lack of deliberate team or individual skill-based practice, and will
vary with the nature and type of skill [94 ]. Offsetting
skill reversibility will rely in part on the ability to assess the relevant elements
of the required skill performances, and utility of the practice-based knowledge
regarding retention or transfer effects that accompany practice of these skills [95 ]. The use of the cognitive technique of imagery,
specifically mental rehearsal of the execution of individual skills/team
strategies, can aid with physical skill learning or refinement [96 ]. However, no research has considered the role of
imagery in skill retention following deconditioning or rest. Video-based observation
(modelling) of existing skill execution or performance can also be used to promote
physical skill learning and refinement, and can enhance both individual and team
confidence in the ability to execute the skill [97 ].
A period of abstinence from sports may also offer athletes an opportunity for mental
rest and recovery, especially where restrictions occur towards the end of a
competitive season. Recent research in professional rugby union [98 ] suggests advanced information regarding the timing
and length of any competition break (i. e. off-season) can determine the
level of autonomy players perceive over their break from the sport, as well as the
subsequent degree of psychological recovery achieved. Given that restrictions
associated with the COVID-19 pandemic have meant a suspension (as opposed to
termination) in the current competition season, athletes are being asked to engage
in
a level of interim individual training that does not align to a designated off-, pre-
or in-season period, without any competition goal or outcome to pursue. This training
‘limbo’ may reduce players’ ability to cognitively
‘detach’ [99 ] and negate any potential
psychological benefit associated with time away from the sport.
In considering the human trauma associated with COVID-19 it is noteworthy that the
consequences for mental health and well-being will not be inherently negative.
Potential exists for growth in response to traumatic life experiences, where growth
involves profound and transformative positive changes in cognitive and emotional life
that are likely to have behavioral implications [100 ].
Research in sports has examined growth in relation to adverse intrapersonal
experiences such as long term injury and sports retirement [101 ], and recently at the interpersonal and organizational level (see [102 ]). Both individual and collective psychological
growth may be derived from the trauma and adversity athletes, teams and their staff
face during the restrictions. The extent to which growth is likely to occur will,
however, be influenced by the amount and nature of the support provided before,
during, and after the restrictions.
Nutritional considerations during enforced modified training and
re-training
The overarching goal during a phase of restricted training is to maintain physical
capacity via preservation of muscle mass, minimization of unwanted body fat increase,
support of immune function and maintenance of cardiovascular capacity. Energy
expenditure may be reduced during a period of reduced training, although other
factors may be increased contributing to overall energy expenditure. For example,
Anderson et al. [103 ]
[104 ]
[105 ] suggests that with injured athletes
who have a reduction in their absolute training intensity, increases in other factors
(e. g. frequency of resistance training and rehabilitation) result in trivial
changes in total daily energy expenditure (estimated reduction of 300
kcal·d-1 ). Therefore nutritionists should consider an
individual’s habitual physical activity level (e. g. dog walking,
living and training logistics, active family) prior to suggesting a reduced total
caloric intake. One of the main challenges for bespoke nutritional intervention
during this period will be the accurate assessment of daily energy expenditure with
a
‘one-size fits all ’ approach being particularly
problematic. Rugby players have large inter-individual differences in daily energy
expenditure when measured via doubly-labelled water, even when the players appear
to
be undertaking similar training sessions ([Table 1 ])
[106 ]
[107 ]
[108 ]
[109 ]. This highlights
the substantial contribution of activities away from the training ground on total
daily energy expenditure, and it is therefore essential that nutritionists attempt
in
some way to quantify the activities of the day during this period of training
restriction.
Table 1 Energy expenditures of professional and elite male rugby
players during various stages of the season, measured via doubly-labelled
water (DLW).
Cohort
Total Energy Expenditure (MJ·day-1 )
Observational Period
Reference
Senior RL (n =6)
22.5±2.7
In season
Morehen et al., [105 ]
Senior RL (n =6)
18.7±6.1
In season
Smith et al., [106 ]
Senior RU (n =6)
21.2±7.3
In season
Smith et al., [106 ]
U20 RL (n =6)
18.7±3.1
In season
Smith et al., [106 ]
U20 RU (n =6)
18.2±3.0
In season
Smith et al., [106 ]
U16 RL (n =6)
17.5±4.0
In season
Smith et al., [106 ]
U16 RU (n =6)
16.1±2.2
In season
Smith et al., [106 ]
U18 RL (n =6)
19.0*
Preseason (incl. contact training)
Costello et al., [108 ]
U18 RL (n =6)
18.1**
Preseason (exc. contact training)
Costello et al., [108 ]
U18 RL (n =6)
18.4±3.1
Preseason period
Costello et al., [107 ]
RL=rugby league, RU=rugby union, *calculated from
reported 5-day energy expenditure (95.1±16.7
MJ·5-day-1 ), ** calculated from
reported 5-day energy expenditure (90.3±17.0
MJ·5-day-1 ).
Research has shown decreased insulin sensitivity, attenuation of postprandial lipid
metabolism, and an increase in fat mass as a consequence of simply reducing step
count (~1300 from ~10 000) for 2–3 weeks [110 ] alongside increases in visceral adiposity [111 ]. If athletes reduce their daily activities, there is
a requirement to reduce calorific intake versus ‘normal’ habitual
competition; however, it is important to maintain habitual protein intake. Although
the majority of research has focused on middle- and older-aged males [112 ]
[113 ], targeted
nutrition, specifically dietary protein intake, has been shown to mitigate the
consequences of reduced activity, even in younger adults [114 ]
[115 ]. One specific essential amino acid
that may play the most pivotal role in the attenuation of anabolic resistance as a
result of disuse is leucine, a potent stimulator of mTOR and thus muscle protein
synthesis [116 ]. It is therefore suggested that
athletes maintain a high protein diet rich in leucine, consuming approximately 0.4
g· kg-1 body of protein regularly (every 4 hours)
throughout the day [117 ]. The reduction in calories
will therefore come from reduced carbohydrate and fat intake, utilizing a periodized
carbohydrate model based on the demands of the training day [118 ]. It is important, however, that sufficient carbohydrates are consumed
during this period and that athletes do not adopt a ketogenic style diet given the
strong links between carbohydrates, stress hormone responses and the immune function
(discussed further in [119 ]
[120 ]
[121 ]). Protein is often used in
conjunction with creatine monohydrate to support maintenance/gains in
strength and lean mass. Supplementation has been shown to attenuate loss of upper
arm
mass and strength, specifically during times of disuse (limb immobilization), as well
as increase muscle hypertrophy following lower limb immobilization [122 ]
[123 ].
From an immune support perspective, research has shown that protein may also have
a
pivotal role in supporting the immune function, specifically antibody response to
infection [124 ]
[125 ]
again highlighting the need to maintain sufficient protein intakes. Other nutritional
factors that may aid with microbe
‘resistance’/‘tolerance’ during this specific
period include supplementation of 500–1000 mg vitamin C [126 ], 1000–4000 iU daily vitamin
D3
[ [127 ]
[128 ] and ~20 billion CFU multistrain probiotic [120 ]
[129 ]
[130 ]
[131 ]. For a full
review of nutrition and immune tolerance, the reader is referred to Walsh [120 ].
Reconditioning considerations on return to training
Extended periods of restricted or modified training create a challenge for athletes
when returning to sports ready to perform and with a low risk of injury. Following
the National Football League “lockout” in 2011, it is not known
whether or not the athletes returned in good physical condition, but the increased
incidence of Achilles tendon injuries [6 ] suggests that
athletes may not have been physically ready for the demands of the game or the return
to play protocols were not thorough and progressive enough.
Some physical qualities are likely easier to maintain (e. g. strength, power,
aerobic and anaerobic capacity and linear speed) with minimal equipment, although
on
return to training, all require consideration. In many cases players have to train
alone without access to equipment, appropriate space or expertise, leading to an
inability to maintain the required intensity of training. This will vary between
countries, given variations in government-enforced physical distancing protocols.
The
most difficult aspect of rugby training to replicate when training individually are
the “intricacies” of the sport. These include the sport-specific
physical and mental demands, such as changes in direction while running at speed,
running with ball in hand, attempting to evade would-be tacklers and then being
tackled, lineout jumping, cutting, tackling, scrummaging, ruck clearance and mauling
[132 ]. In this context, decision-making can only be
practiced when training with others. Under normal circumstances, athletes would
return to structured preparation after a 3- to 6-week off-season and progress to
playing the game over 6–12 weeks.
It is vital that athletes returning to rugby following a period away from team
training undertake a well-planned, progressive return to play program to prepare to
perform and to decrease the risk of injury (see [133 ]).
High-speed (or sprinting) running is one specific consideration on return to
training, given the concurrent benefit to performance (e. g. acceleration and
maximum sprint speed [134 ]) and injury prevention [135 ]. High-speed running exposure should be managed
carefully as an excess or rapid increase in training load may increase soft tissue
injury risk [21 ]. In sprinters, the training phase
(e. g. following the off-season) and transition phase between the preparation
period and competitive season appear to be vulnerable periods for injury [136 ]. That said, high-speed running is paramount for
sprint performance enhancement [137 ], as well as the
morphological and architectural lower limb qualities [84 ], suggesting it should be incorporated into reconditioning training
programs. On return to match play, if the difference between training speed and
competition speed is large, this may also increase injury risk [85 ], although empirical evidence does not exist to
support this.
For athletes that have had limited or reduced exposure to high-speed running, the
initial weeks of training should focus on the re-familiarization of the intensity
and
duration required for training and competition, which should be progressed gradually
[85 ]. No clear recommendations exist on sprint
exposure for rugby players, although general principles such as avoiding high-speed
running on consecutive days do exist [85 ]. These should
be considered alongside other training modalities rugby players are exposed to [138 ] and their potential interaction (e. g.
avoiding high velocity sprinting following fatiguing lower-body resistance training).
As a guide, athletes should be exposed to a range of sprint distances, to allow the
development of acceleration (10–50 m, >98% intensity, total
session volume 100–300 m), maximal velocity from a flying start
(10–30 m and >98% intensity, total session volume
50–150 m) and sprint-specific endurance (80–150 m and
>95% intensity, total session volume 300–900 m) (see [85 ]). Resisted sled sprint training may also be
beneficial (see [139 ]). Given that high-speed running
exposure will be one of a number of qualities practitioners will aim to retrain, it
may be more prudent to focus of the quality of the high-speed running exposure, as
opposed to volume per se . For example, practitioners should end a high-speed
running session when there is a drop-off in performance, and/or technical
error is observed, and 1–2 minutes of recovery can be provided for every
second spent maximal sprinting between repetitions [85 ]
[140 ].
Preparing for the rugby-specific actions is also a key consideration for athletes
and
practitioners. This is best achieved through performing such actions during
‘practice’ involving the performance of the fundamentals of the game
with teammates in either ‘opposed’ or ‘unopposed’
situations. For example, simple skills such as catch and pass, game plan
understanding, tackle progressions, and the changes in direction that occur during
normal practice are part of preparing to play the game.
Another example of how to integrate injury prevention and progressive exposure to
game play is change of direction and agility. These are important facets to evade
tacklers and create an open field of play [141 ]. An
athlete's agility performance is strongly influenced by the ability to
rapidly decelerate and reaccelerate while adjusting his or her momentum to either
pursue or elude opponents [142 ]. While athletes could
be working on change of direction, acceleration, deceleration and agility by
themselves (e. g. practice sharp changes in direction while running at high
speeds, and including rapid acceleration and deceleration), once they return to
training with team members and return to play progressions, the key is to gradually
build in layers of intensity (e. g. speed of run and sharpness of direction
change) and decision-making.
As described previously, the tackle poses the highest injury risk in rugby,
accounting for around 50% of injuries [29 ]
[30 ]. Therefore it is important that athletes have the
required physical and technical skill set to perform safely and effectively. The
development of specific tackle skills have received little attention within the
scientific literature [143 ], but poor tackle technique
has been shown to result in a higher injury risk [144 ]
[145 ], and fatigue has been shown to
alter tackle technique [146 ]
[147 ]. Several frameworks have been proposed on how to train the tackle
[148 ]
[149 ], although
the effectiveness of these is yet to be determined. It is likely that following a
prolonged period of non-contact training, due to the enforced physical distancing
players will require a graded exposure to both the technical and physical components
of the tackle [148 ]. Following a typical 3- to 6-week
off-season and 6–12 week pre-season, athletes will start to engage in contact
and tackle training during weeks 3–6, with progressions over 2–6
weeks. It is likely athletes will need at least 3–4 weeks of progressions and
exposure to tackle and contact skill training to prepare for matches.
The simplest way to prepare for the explosive demands of the game is to ensure all
activities follow well-planned progressions ([Fig.
2 ]). Such progressions are dependent on the sport-specific task in question and
the position demands for each individual. In the specific context of return to
training in relation to COVID-19, local government policy and risk assessments based
on potential for COVID-19 transmission in any given activity or session will impact
upon decisions regarding the choice and rate of progressions.
Fig. 2 Training considerations following return to play after the period
of restricted training due to COVID-19. Reintroduction of group training will
require progressions and structure of training to be developed with reference
to risk of COVID-19 transmission.
Development of strength and power on return to training
Rates of change in power and strength are influenced by the intensity (percentage
of
maximal), volume (sets x repetitions) and frequency of resistance training, with
relatively small changes in maximal strength and power in elite athletes, due to
their previous training status [3 ] ([Tables 2 ] and [3 ]). In a
meta-analysis, maximal strength was reported to increase at a rate of 1.8%
weekly [3 ]. Similarly, Issurin [150 ] reported that elite kayakers improved their maximal strength by
5.9% over the first 3-weeks of a 20-week training cycle, an average
improvement of 1.93% a week. However, during the second 3-week week phase of
training average change in strength was only 0.53% a week, and continuation
of the program resulted in minimal improvements in maximal strength, with the final
14-weeks resulting in a further total increase of only 1.82%. These results
suggest that only the first 6-weeks of a strength training cycle provides positive
adaptations for elite athletes. The changes in strength and power during a
professional rugby season also demonstrated that the majority of strength changes
occur early in a program [5 ]. Improvements in strength
during the first 12-weeks of training were 2.7±1.1%. During the
second 21 weeks of training, strength gains were on average 1.9±1.1%.
These changes are considerably lower than reported by McMaster et al. [3 ]; however, these results reflect changes in force
production during an isometric squat rather than specific lifts (e. g. squat)
that also improve due to familiarity of the exercise task, and technique changes.
It
is worthwhile noting that the greatest changes in strength in professional rugby
players in England coincided with the highest volumes of strength training, during
the second phase average strength loads were 63% of those utilized in the
first phase [5 ].
Table 2 Most effective intensity and volume for strength and power in
collision sports and the expected percentage change in maximal strength and
power per training session conducted (data from McMaster et al. [3 ]).
Intensity (%RM)
Sets
Repetitions
Δ% per Training Session
Maximal strength
77±7
3.4±1.2
6.5±3.3
0.55%
Power
81±2
4.3±0.3
7.0±0.9
0.20%
RM=repetition maximum, Δ%=percentage
change.
Table 3 The impact of training frequency weekly strength and power
changes (data from McMaster et al. [3 ]).
2×weekly
3×weekly
4×weekly
Maximal strength
0.9%
1.8%
1.3%
Power
0.1%
0.3%
0.7%
The potential rate for gains in power for athletes in collision sports appear
relatively low; however, the protocols utilized in studies examining power changes
are more suited to induce changes in maximal strength than power [151 ]
[152 ]. Over a season of
professional rugby, the greatest improvements in power were observed in the early
competition phase, when strength training frequency decreased, training intensity
remained high, and total volume load was reduced [5 ].
Rugby players are typically assessed for strength and power at various stages within
the season. While published data are not available, unpublished data (Bennett,
Unpublished; [Table 4 ]) demonstrate the changes in
strength and power exercises from 26 male Tier 1 International rugby union players
over a 5-week physical training phase following a 5-week break from organized
strength and power training (2-week end-of-season tour and 3-week recovery). These
data provide a reference point for expected strength and power development rates
following extended breaks in training, such as that resulting from the COVID-19
pandemic.
Table 4 Rate of changes in strength and power markers in a tier 1
international rugby union team over 5 weeks (n=26 players).
Start
End
Δ%
Δ% per Week
Squat (kg)
165.4±20.0
206.7±22.26
25.6±9.7%
5.1±1.9%
Bench Press (kg)
139.3±12.6
150.3±11.8
8.1±5.6%
2.6±1.1%
Prone Row (kg)
114.0±10.9
129.3±10.3
13.8±7.1%
3.8±1.4%
Countermovement Jump Height (cm)
61.5±7.6
68.9±7.6
12.1±5.3%
2.4±1.1%
Δ=change; Δ%=percentage change.
[Table 5 ] presents the changes in a male professional
rugby union team (35 players) in the first 4-week training block, after a 4-week
off-season (Bennett, unpublished). Of note in both the data on the professional
players and also the international players, considerably greater changes in lower
body strength are observed in comparison to upper body strength in both instances.
This could be related to the muscle-specific atrophy described in response to extreme
models of disuse [60 ]
[61 ]. Alternatively, it could be related to players' favored training
options when away from an organized environment (e. g. undertaking
unsupervised upper-body, as opposed to lower-body resistance training).
Table 5 Changes in strength markers in a professional rugby union
team over 4 weeks (n=35 players).
Start
End
Δ%
Δ% per Week
Squat (kg)
167.3±26.6
190.4±27.8
14.4±10.6%
3.6±1.9%
Bench Press (kg)
131.7±13.1
137.2±13.1
4.3±3.8%
1.1±1.0%
Prone Row (kg)
112.0±8.9
116.3±8.4
4.0±3.3%
1.0±0.8%
Δ=change; Δ%=percentage change.
Neural adaptations appear to provide a greater contribution to strength increases
than muscular hypertrophy early in training [86 ], but
changes in power and maximal strength that occur from detraining are likely a result
of both neural adaptations and a decrease in cross-sectional area of the muscle [153 ]. That said, there is evidence to suggest that neural
changes from heavy strength training are long lasting and can extend beyond 12-weeks
of detraining [64 ]. These findings suggest that on
return to club training, hypertrophy of muscle fibers should be the primary focus,
especially in those players who have lost significant muscle mass. Some evidence is
present in the literature with regard to “muscle memory” a phenomena
where previously trained musculature retains a considerable proportion of relevant
adaptations and does not return to its pre-trained state, even after a considerable
period of detraining (for review see [154 ]). It has
been shown that individuals with a substantial strength training background can
regain previous muscle fiber hypertrophy and strength levels in a relatively short
period of time, as much as 32-weeks of detraining can be reversed with 6-weeks of
strength and power training [155 ]. This, alongside a
maximal window of 6-weeks before the rate of return on strength training is minimized
[150 ], would suggest a 6-week training block is
sufficient for professional rugby players to regain previous physiological
adaptations.
Considerations for athletes returning to training after suspected or confirmed
COVID-19 infection
Any discussion or guidance regarding re-conditioning in athletes needs to acknowledge
and reflect the general principles informing return to play after acute medical
illness. This is particularly important for athletes with confirmed or suspected
COVID-19 infection. In many cases, an athlete will only have been given a presumptive
diagnosis, based on the presence of typical clinical features (e. g. dry
persistent cough and febrile illness) leading to a 7- or 14-day period of
self-isolation. Many suspected cases will not have undergone formal testing due to
local testing procedures and policies. Indeed, for most young, fit individuals, acute
COVID-19 infection is associated with very few overt systemic features, typically
only very mild upper airway symptoms (e. g. anosmia), and the athlete may
often not feel unwell. A very small number of previously fit young people will
develop moderate to severe disease and may require acute medical care, including in
some cases, the provision of hospital-level support, and possibly ventilatory support
[156 ]. In this latter group, data series indicate an
almost ubiquitous presence of pulmonary infiltrate (on either a chest x-ray [CXR]
or
computerized tomography [CT] scan) and a high prevalence (8–28%) of
elevated markers of cardiac dysfunction (e. g. troponin rise) that may
manifest acutely as myocarditis, heart failure, cardiac arrhythmias and acute
coronary syndrome [157 ]
[158 ]. There also appears to be an increased risk of thromboembolic events,
which need to be considered in the differential diagnosis in any clinical
presentations encountered in athletes recovering from COVID-19 infection;
i. e. consider deep vein thrombosis in an athlete reporting calf pain.
Historically, the most widely adopted return to play approach in athletes recovering
from respiratory tract infection, is based on the ‘neck check’
approach [159 ]. Using this approach, athletes are
advised that they may continue to exercise, if their symptoms and clinical signs are
confined to the upper airway (e. g. only coryzal symptoms) and a short
sub-maximal exercise trial does not exacerbate symptoms. The scientific basis for
this recommendation is weak, and there is long-standing concern of the potential risk
of athletes with respiratory tract infection developing other clinically significant
end-organ complications on their return to vigorous exercise. Of these risks, the
most important is the risk of myocarditis or myocardial damage, which could be highly
relevant in relation to COVID-19. The current COVID-19 pandemic, particularly
challenges the ‘neck check’ approach, in that there is reported
variability and an almost ‘biphasic’ recovery pattern, such that
infected individuals can appear to transiently improve, only to deteriorate at a
later stage, approximately one week after the onset of symptoms. In addition, and
as
outlined above, there is concern from emerging data, that myocardial irritation and
frank myocarditis may be both prevalent and an important manifestation of this novel
infection [157 ]
[158 ]
[160 ]. It is not yet clear if this is the case in those
with clinically mild disease (i. e. in those not hospitalized); however,
given the considerable cardiovascular challenge of participating in elite sport,
consideration of this risk should form a key part of an individual’s return
to play assessment. It is with these considerations in mind that clinicians generally
adopt a more conservative approach in planning a post COVID-19 return to play
strategy for confirmed and suspected cases at the current time. Expert groups
(e. g. in cardiology and respiratory medicine specialties) are starting to
provide guidance for specific follow-up based on small data series of the general
population and expert opinion, and this will undoubtedly evolve as peer-reviewed data
from the athletic population becomes increasingly available.
It is recommended that medical practitioners such as Sports Physicians, overseeing
the return to training, should consider utilizing an approach that incorporates and
considers ‘risk’ stratification. It may also be possible to assess
physiological markers including resting, exercising and recovery heart rates, beat
to
beat variability, ratings of perceived exertion and other indicators of reduced
cardiopulmonary function. In addition, ongoing understanding of the condition may
point to other markers of wider organ involvement that form part of the elite sports
training monitoring such as exaggerated rises in blood creatine kinase [161 ] and lactate concentrations. Furthermore, a graded
return to activity, perhaps akin to that used in under-recovery
unexplained-under-performance syndrome [162 ] could be
employed to guide a careful progression, while our understanding of the most
appropriate post-COVID progression develops. In the meantime, clinicians can use
[Fig. 3 ] to help inform return to play risk
stratification.
Fig. 3 Return to play risk stratification for athletes following
COVID-19 symptoms.
Considerations for at risk groups during enforced modified training and
re-training
As a result of the extended period of training restriction, there will be some
athletes who are at a significantly higher risk of injury when they return to
training. Although specific evidence in this area is limited due to the uncommon
nature of such a period of restriction in elite sports, broader evidence available
concerning predisposition for injury may assist in the identification of these
at-risk groupings. For example, evidence has shown previous injury to be a strong
risk factor for further injury [47 ]. This is
particularly important to consider when the ability to a) rehabilitate and
pro-actively manage any existing injuries and b) continue prehabilitation programs
for injury prevention is reduced during restriction. It is also noteworthy that
following the National Football League lockout in 2011, the Achilles tendon injured
group in the early phase of return to competition were, on average, younger and had
a
lower exposure to the NFL environment than Achilles tendon injured players in other
years, suggesting specific risk [6 ]. Alongside the
physical health of the athlete, their mental well-being may also be affected,
highlighting the need for well-defined and accessible support structures for athletes
and staff both during and after isolation. Furthermore, and as a direct result of
this extraordinary time, the best practice management of athletes who either present
with COVID-19 symptoms or are returning to activity following a suspected or
confirmed case of COVID-19 is clearly of huge importance. Of note is the risk of
long-term effects on the respiratory and cardiovascular systems, if these individuals
are not managed correctly.
[Figure 4 ] summarizes those groups considered
‘at-risk’. It is recommended that athletes that fall into these
groups are given careful consideration when planning their reintegration into normal
training practice. It might be suitable to utilize physical and psychological
screening tools to establish a baseline upon return to the club environment and to
provide practitioners with information upon which to base their periodization and
programming. Overall, an individualized approach to the at-risk groups is
recommended.
Fig. 4 A summary of ‘at risk’ athletes following
modified training due to COVID-19.
Challenges and practical recommendations for collision sports
The COVID-19 pandemic has created a unique scenario for all major sports with respect
to the highly unusual period of training restriction. All sporting national governing
bodies and competition organizers will need to consider how they plan the return of
training activities, and ultimately competition, balancing a range of drivers to
restart sports as quickly as possible with how they best manage the welfare of their
athletes. These will differ between countries (e. g. England versus New
Zealand) and sports (e. g. rugby league versus rugby union) given the varying
level of impact that COVID-19 has had on training restrictions and modification, and
the varying stages of the season athletes were in. In collision sports, the
resumption of training following a period of modified isolated training will arguably
be harder to manage than in other sports. This is due to a number of factors that
include the high-risk nature of participation and the importance of strength and
power, which may be affected by restricted access to training equipment and space.
In
addition, the importance of executing skills in high-risk areas of the game, such
as
the tackle, and the lack of opportunity available to train these skills during a
period of restriction also requires special consideration. Even on the resumption
of
training, factors such as limits on the number of players that can train together
and
limits on the amount of time it is acceptable for players to be in close contact with
other players will influence possible training progressions. That said, the
unprecedented period of non-contact training may provide a positive period for
physical and psychological rest and recovery. With the application of appropriate
and
progressive reconditioning practices on return to training, this may improve an
athletes’ performance and well-being. Athletes may also be afforded the
opportunity to target the development of specific physical weaknesses, without the
challenges of preparing for weekly competitive matches.
Monitoring of athletes’ training during the period of training restriction
may be beneficial when making decisions regarding initial load and progressions when
group-based training resumes. Player load monitoring should be appropriate to capture
the range of stresses (e. g. volume, intensity, resistance training, running)
to which athletes have been exposed [163 ].
Microtechnology is commonly used within rugby to collect objective external load
measures, but access to both hardware and software is likely to be limited when
training away from club environments. Session rating of perceived exertion (sRPE;
[164 ]) offers a practical method of monitoring
player load, regardless of the exercise modality. Remote monitoring of sRPE has been
shown to be valid in comparison to recall with 30 minutes of exercise cessation when
collected 24 to 48 hours [165 ] following an activity,
but not at 72 hours [166 ] or when collected as part of
a weekly self-reported training load diary [167 ]. As
such, athletes should aim to report their sRPE at least every 48 hrs. In addition,
it
might be prudent to capture information about exposure to specific training, such
as
high-speed running. In the absence of regular monitoring during the period of
training restriction, screening prior to the resumption of group-based training
should capture information about the training that has been carried out by each
individual athlete.
It is also logical to think that the risk of infectious transmission in contact
sports is higher than in non-contact sports and so the development of medical policy
to mitigate the risk of transmission alongside suspected case management is critical.
Furthermore, there will be a need to assess the risk of COVID-19 transmission in
close contact elements of training, and to introduce these in a graded fashion that
minimizes risk. [Table 6 ] summarizes the focus areas,
challenges and practical recommendations that have been identified in this review
that the teams and major stakeholders of elite collision sports need to consider when
managing athletes during this unprecedented period of restriction and when planning
the resumption of training and competition.
Table 6 Challenges and practical recommendations for sports during
and following COVID-19.
Focus Area
Challenges as a Result of Training Restriction (COVID-19)
Practical Recommendations
Physical Qualities
Variable access to training facilities (equipment and/or
space)
Variable ability to train under heavy loads
Strength likely to decrease significantly if restrictions last
beyond 12 weeks
Decreased tolerance to specific activities (e. g.
high-speed running)
Continue to undertake periodized and planned training where
possible during restriction
Maintain exposure to high-speed running and sprinting during
restriction
Training to failure with lower loads may have some benefit for
mitigating losses to muscle mass and strength
Performing eccentric muscle actions and plyometric training may
help maintain and improve all neuromuscular indices related to
an athlete’s performance
Identify and correct weaknesses to maximize performance and
reduce risk of injury on return to training
When it is safe to do so, athletes should resume formalized
resistance training as soon as possible within a gym
environment
Focus on building muscle hypertrophy when able to return to
training, if significant losses of muscle mass observed
Individualized approach to nutritional needs (see nutrition
section below for specific considerations)
Skill Execution/Sports Specific Actions
Cognitive-based techniques (mental imagery and video-based
observation) to offset deterioration in skill execution and to
enhance preparedness for return
Ring-fenced practice time available before re-commencing
competition to prioritize fundamental skills, including exposure
to contact/collision training
Due to its high risk of injury, re-familiarization of and
technically focused training on the tackle should be
prioritized
To best prepare for the explosive demands of the game, progress
all key activities from planned/predictable to reactive
drills
Psychological Well-being
Isolation and confinement
Training in ‘limbo’ scenario
Psychological impact of deconditioning
Chronic stress acting as an immunosuppressor
Ensure appropriate support networks are available for athletes
to access to help manage any potential negative psychological
experiences during and after any period of isolation
Seek to maintain/nurture team processes (e. g.
teamwork) through designated team task (e. g. opposition
analysis) and social activities throughout
Utilize the opportunity for ‘reset’ of physical
and mental health away from the stress of formal training and
competition. Build in rest periods within training routines to
manage this and engage in other personal and social activities
via available technology to enhance psychological well-being
Nutrition
Reduced/modified energy expenditure
The necessity for nutrition to support immune function during
COVID-19
Difficult to maintain a sports specific body composition
Attempt to assess changes in daily energy expenditure and make
dietary changes accordingly if required (e. g. tracking
body mass change)
Periodize carbohydrates (and thus calories) not only to training
but also daily lifestyle
Consume a high protein diet rich in leucine, consuming protein
regularly (every 4 hours) throughout the day
Keep protein high aiming at 0.4 g·kg-1 per meal
regularly throughout the day
Seek sunlight, if possible, and if not consider supplementing
1000–4000 iU per day vitamin D3
Consider supplementing with 500–1000 mg vitamin C, as
well as probiotics to aid with immune resistance and
tolerance
Injury Risk Management
Reduction in protective strength qualities and fitness capacity
during restriction
Reduced intensity and volume of training during restriction
Less opportunity for structured and guided prehabilitation and
rehabilitation programs
Athletes should focus on the training of known weaknesses
(physical and/or technical) where possible during the
period of restriction
The use of load monitoring tools (e. g. sRPE during and
after restriction will help manage the transition period from
restriction to training)
An individualized approach should be taken to an
athlete’s return to sport and return to play strength
and conditioning programming. The use of physical and
psychological screening tools may help provide information to
support appropriate planning and programming. This is especially
important for at risk groups (see section below).
Maintain regular exposure to high-speed running during
restriction and afterwards where possible
Training loads should be increased gradually and spikes in load
avoided
A 6-week training block is likely sufficient for professional
rugby players to regain previous physiological adaptations, if
significant detraining has occurred
Suspected Case Management
High risk of person to person transmission
Lack of available scientific evidence and understanding of novel
virus
Myocardial irritation and frank myocarditis may be both
prevalent and an important manifestation of COVID-19
Employ a risk stratification approach to the management of
players and return to play. Undertake an individualized graded
return to activity
Aim to assess and monitor where possible physiological markers
including resting, exercising and recovery heart rates, beat to
beat variability, RPE and other indicators of reduced
cardiopulmonary function
All athletes with either confirmed or suspected COVID-19
infection should be symptom free for 7 days and RTP no sooner
than day 10 of the infection
Medical practitioners should consider a cardiology assessment
for previously symptomatic players with confirmed or suspected
COVID-19 prior to returning to training
Additional data collection of COVID-19 specific illness fields
into sports injury surveillance systems to aid best practice
management and our understanding of the risk of this novel
virus
