Keywords
paralympic powerlifting - muscle strength - fatigue - bench press - movement velocity
Introduction
Athletic performance in certain disciplines necessitates ongoing enhancement of
muscle strength and power, and various training methods can be employed for this
purpose [1]. While extensive research has
focused on strength training in sports involving individuals “without physical
disabilities” [2], limited attention has been
given to parasports, particularly Paralympic Powerlifting (PP). PP is a sport
heavily reliant on maximal strength for achieving athletic success [3].
It is well established that fatigue serves as a limiting factor in the progressive
improvement of performance. Place et al. [4],
have reported that prolonged dynamic exercises induce muscle fatigue, resulting in a
decline in the capacity for maximum voluntary contraction. Enoka and Duchateau [5], have also highlighted that muscle fatigue
can arise from various mechanisms and is initiated when the capacity for maximum
strength or power diminishes, which may not necessarily be the limiting factor in an
individual’s task performance ability.
From a mechanical perspective, Jones [6],
suggests that muscle fatigue can be identified by an increase in the slope of the
force-velocity curve, as identifying the specific metabolic causes for these
alterations can be challenging. In 2011, Sánchez-Medina and González-Badillo [7] proposed that the reduction in mean
propulsive velocity (MPV) can serve as an indicator of neuromuscular fatigue because
it is associated with increased levels of metabolites in the bloodstream, such as
lactate and ammonia. They also argued that velocity-based training (VBT) would be
more adequate to control training, however, in the study [7], no changes were observed in the velocity
profile after performing a low number of repetitions, (3×4 [8]) repetitions at 80% 1RM; (3×4 [6]), (3×3 [6]) repetitions at 85% 1RM and (3×2 [4]) repetitions at 90% 1RM. This low number of repetitions is
characteristic of PP training [8] and it is
possible that, for training methodologies where small numbers of repetitions are
used, the VBT may not be reliable for the analysis of neuromuscular fatigue as well
as for training control. Thus, there are uncertainties regarding the ideal method
[9], particularly in the context of PP,
where most studies examining PP have used methods based on zones of one repetition
maximum (1RM) (PBT) to control training [8].
Therefore, the objective of this study was to evaluate the neuromuscular fatigue
indicators in Paralympic weightlifting athletes using two different training
methods: the inertial method (traditional denominated - TRAD) and the
eccentric/concentric training method (ECC) incorporating loads supramaximal in the
eccentric phase of the adapted bench press. The following hypotheses were formulated
for this study: I) Within a TRAD training session consisting of five sets of five
repetitions at 80% of 1RM, there will be no significant loss in velocity; II) ECC
training will result in a greater reduction in velocity between sessions compared to
TRAD training; III) Neuromuscular fatigue indicators will be adversely affected
24 hours after both training methods, and only the ECC method will continue to
exhibit negative alterations in neuromuscular fatigue indicators after 48 hours.
Materials and methods
Research design
This study is characterized as a non-randomized crossover study carried out over
a period of three weeks ([Fig. 1]).
During the first week, participants provided informed consent (ICF) and
underwent a one-repetition maximum (1RM) test. Twenty-four hours later, they
received a verbal explanation of the ECC training method, specifically regarding
the controlled bar repetitions. No additional familiarization was provided as
the athletes were already accustomed to both TRAD and ECC training. The sample
comprised highly skilled Paralympic powerlifting (PP) competitors, including
three Brazilian champions in their respective categories for the year 2022, with
one athlete having participated in the Tokyo Paralympics (2020/2021) and
achieving an eighth place.
Fig. 1 Experimental design. TRAD: Traditional Training; ECC:
Eccentric training; MPV: Mean propulsive velocity.
To assess neuromuscular fatigue, the methodology proposed by Sánchez-Medina and
González-Badillo [7] was employed at
five-time points: pre-intervention, intervention, post-intervention, 24 hours
after the training session, and 48 hours after the training session. Both
training methods utilized five sets of five repetitions during the intervention
phase. TRAD training was conducted in the second week, followed by ECC training
in the third week. This sequencing was based on previous research suggesting
that ECC training may impact recovery time [10].
Sample
The sample consisted of eleven male Paralympic Powerlifting athletes ([Table 1]). The types of physical
disability are as follows: four athletes have congenital arthrogryposis
multiplex; three have polio sequelae; two athletes are affected by spinal cord
injuries and two athletes suffered lower limb amputation. We emphasize that
despite different disabilities, athletes are evaluated based on their functional
capacity to guarantee a fair competition [11]. For inclusion criteria in the study, athletes would have to be
ranked among the top 10 in their respective weight categories at the national
level. Having a minimum experience of 3 years of practice in the modality,
athletes would be excluded from the research if they had pain or any physical
problem that made it impossible to carry out the intervention and voluntarily
withdraw. All athletes included in this research met the eligibility criteria
established by the Brazilian Paralympic Committee and had the necessary
qualifications to participate in the sport [11]. They voluntarily enrolled in the study and provided informed
consent by signing the required documents. The research protocol received
approval from the Research Ethics Committee, with technical advice number
2.637.882.
Table 1 Sample Characterization.
|
Variables
|
(Mean±SD)
|
|
Age (years)
|
31.54±9.72
|
|
body mass (kg)
|
73.63±17.55
|
|
1RM Bench Press Test (kg)
|
121.63±40.94
|
|
1RM/Body mass
|
1.63±0.38
|
|
Time Experience (years)
|
4±1.18
|
MPV - Mean propulsive velocity, TRAD - Traditional training, ECC -
Eccentric training, ICF - Informed consent form, 1RM - Maximum load, SD
- Standard deviation.
The sampling power was calculated a priori using the open-source software GPower
(Version 3.0; Berlin, Germany), choosing a “F family statistics (ANOVA)”
considering a standard α<0.05, β=0.80 and the effect size of 1.33 found for
the force indicator in Paralympic powerlifting athletes [12]. Thus, it was possible to estimate a
sample power of 0.80 (F (2.0): 4.73) for a minimum sample of eight subjects per
group, suggesting that the sample size of the present study has statistical
strength to respond to the research approach.
Instruments
A linear position encoder (encoder) manufactured by Vitruve (Madrid, Spain) was
utilized to evaluate neuromuscular fatigue [13]. The mean propulsive velocity (MPV) obtained from the encoder was
used to determine the changes in velocity loss before, after, 24 hours, and
48 hours following the training session, as well as the velocity loss decline
during the five sets of five repetitions.
Procedures
Traditional training (TRAD): This training protocol involved using inertial loads
set at 80% of 1RM for both concentric and eccentric movements. Athletes were
instructed to perform at their usual training speed. Additionally, participants
were advised to maintain a consistent grip width for both training methods, as
this variable has the potential to influence movement kinetics [14].
ECC training: In this training method, the load used during the eccentric phase
exceeded that of the concentric phase. Specifically, a load of 110% was applied
during the eccentric phase, while the concentric phase utilized 80% of 1RM [15]. To introduce the supramaximal load,
two devices called Berenice were affixed to the bar. As the bar touched the
athlete’s sternum during the bench press movement, the equipment made contact
with the ground and disconnected from the bar, releasing 30% of the total load.
This allowed the athlete to perform the concentric phase with 80% of their
1RM.
For both training methods, a mechanical pause of approximately 1.5 seconds [7], was implemented between the eccentric
and concentric actions to minimize the rebound effect of the movement.
Additionally, in the ECC method, a pause of approximately 1 second was observed
at the end of each concentric action to facilitate the re-coupling of the
Berenice devices.
Maximum Load Determination
The bench press 1RM test followed the protocol proposed by Brown & Weir [16]. Prior to the test, a five-minute
period of light activities involving the tested muscle group (using an arm cycle
ergometer) was performed, followed by specific stretching targeting the chest,
triceps, and shoulder muscles. Subsequently, the specific warm-up for the test
commenced, which included eight repetitions at 50% of the estimated 1RM,
followed by an additional set of three repetitions at 70% of the estimated
1RM.
During the bench press 1RM test, weight increments were uniformly added based on
the weight lifted during the sets at 70% of the estimated 1RM. Each successful
attempt resulted in a 5% increase in weight. This approach aimed to ensure that
at least two attempts at 1RM could be performed. In the event of concentric
failure, the load was reduced by 2.5%. The test protocol included a maximum of
five attempts, with a five-minute rest interval provided between each
attempt.
Neuromuscular Fatigue Evaluation
As per the methodology proposed by Sánchez-Medina & González-Badillo [7], the mean propulsive velocity (MPV) was
utilized to determine the percentage change in the loss of velocity at a load of
45% of 1RM for three repetitions at four different time points: pre-training,
immediately post-training, 24 hours post-training, and 48 hours post-training.
The calculation employed the following equation provided by the authors: 100 x
(average MPV post − average MPV pre)/average MPV pre. This calculation was used
to assess neuromuscular fatigue at the 24-hour and 48-hour time points following
training.
To analyze the percentage loss of mean propulsive velocity in each set, the
velocity decline across the repetitions within the five consecutive sets of the
exercise was evaluated. This calculation involved considering the fastest and
slowest repetition (typically the first and last repetition) within each set,
and the average of these values was computed across the five sets.
However, in order to account for the observed discrepancy in the velocity of the
first repetition within our sample, both at the load of 45% of 1RM and during
the training sessions, we identified a consistent movement pattern where the
first repetition consistently exhibited lower speed compared to the subsequent
repetitions. Therefore, in our analysis of velocity during training as well as
in the pre-training, post-training, 24-hour, and 48-hour assessments, we
excluded the data associated with the first repetition. Instead, we calculated
the average velocity of the subsequent repetitions for each evaluation ([Fig. 2]).
Fig. 2 Quantification of neuromuscular fatigue during traditional
training at the respective times: Pre (45% 1RM), intervention (80% 1RM)
and post (45% 1RM).
Statistical Analysis
Descriptive statistics were conducted using measures of central tendency,
specifically mean (X), along with Standard Deviation (SD). The Shapiro-Wilk test
was employed to assess the normality of the variables, taking into account the
sample size. To examine the performance differences across the various moments,
a Two-Way repeated measures ANOVA (Condition x Moment) was conducted, followed
by Bonferroni’s Post Hoc test. Effect size in the ANOVA was evaluated using
partial square eta (η2p), with values categorized as low effect (≤0.05), medium
effect (0.05 to 0.25), high effect (0.25 to 0.50), and very high effect
(>0.50) [17]. The variation coefficient
(CV%) was calculated by the formula: CV%=(standard deviation (SD)/mean)×100,
Where a variation between 10 to 15% is acceptable [18]
[19].
Statistical analysis was performed using the Statistical Package for the Social
Sciences (SPSS), version 22.0, (IBM, New York, USA). The significance level was
set at p<0.05.
Results
No significant differences were observed for TRAD training in any of the evaluations,
as illustrated in [Fig. 2]. However, a
significant reduction in the loss of mean propulsive velocity was noted in the pre x
after ECC training (0.95 m/s±0.24), 95%CI 0.84–1.06, CV=6% vs. (0.83 m/s±0.24),
95%CI 0.72–0.94, CV=8.05% respectively, p=0.001, F(3.63)=8.866, η2p=0.297 - high
effect) and pre x 24 h (0.95 m/s±0.24), 95%CI 0.84–1.06, CV=6% vs. (0.85 m/s±0.21),
95%CI 0.75–0.94, CV=5.32%, p=0.004, F(1.21)=8.866, η2p=0.297 - high effect ([Fig. 3]
[4]). A significant difference was also observed between the
post-intervention moments between TRAD x ECC (0.95 m/s±0.22), 95%CI 0.85–1.05,
CV=4.67% vs. (0.83 m/s±0.24), 95%CI 0.72–0.94, CV=8.05%, p=0.003, F(1.21)=12.158,
η2p=0.367 - high effect ([Fig. 4]).
Fig. 3 Quantification of neuromuscular fatigue during eccentric
training at the respective times: Pre (45% 1RM), intervention (110/80% 1RM)
and post (45% 1RM).
Fig. 4 Analysis of neuromuscular fatigue at a load of 45% of 1 RM
between pre, post, 24 and 48 h post-intervention. TRAD: Traditional
Training, ECC: Eccentric Training.
There was a significant difference (CV=set 1 Trad [6.52%] x set 1 Ecc [12.38%]; set 2
Trad [6.50%] x set 2 Ecc [10.08%]; set 3 Trad [7.54%] x set 3 Ecc [11.66%]; set 4
Trad [10.61%] x set 4 Ecc [12.08%]; set 5 Trad [8.69%] x set 5 Ecc [11.10%],
p<0.001) between the percentage of mean propulsive velocity between all series
when comparing TRAD x ECC. Both comparisons produced a value of F(4.172), 12.222,
η2p=0.221, indicating a medium effect size ([Fig.
5]).
Fig. 5 Analysis of neuromuscular fatigue during five sets of five
repetitions between traditional and eccentric training. TRAD: Traditional
Training, ECC: Eccentric Training.
Discussion
The main objective of this study was to evaluate indicators of neuromuscular fatigue
and compare them between traditional (TRAD) and eccentric (ECC) training methods.
The main finding of this study reveals that there was no significant percentage loss
in average propulsive velocity (MPV) during the series, and there were no
significant differences in the variation in the percentage loss of MPV in the pre,
post, 24 h and 48 h moments for TRAD Training, as illustrated in [Fig. 2]
[4]. On the other hand, for ECC training, there was a reduction in MPV
variation between pre x post-intervention and pre x 24 h as shown in [Fig. 3]
[4], but no significant percentage loss was observed during the sets of
training.
The use of MPV as a reliable indicator for strength analysis has been well-documented
in the literature since 2010 [20], including
its application for assessing neuromuscular fatigue. However, most of these analyses
have focused on specific interventions targeting muscular endurance and 1RM
prediction [21]
[22]. Our findings do not align with the results
reported by Sánchez-Medina & González-Badillo [7], as the traditional training did not lead to a loss of mean propulsive
velocity within each set or in the pre, post, 24 h, and 48 h assessments, using a
load of 45% 1RM ([Fig. 2]).
It is important to consider certain specificities when interpreting these data, such
as the type of training employed in this particular sample. This study is the first
to analyze MPV as an indicator of mechanical fatigue in strength training for
Paralympic Powerlifting athletes. Strength training for these athletes typically
involves submaximal to maximal loads ranging from 60% to 100% of 1RM, with sets
ranging from 5 to 8 and repetitions from 1 to 12 [23].
In 2006, Izquierdo et al. [18], identified that
the mean velocity of the bench press starts to decline when reaching approximately
one-third of the total repetitions performed until failure, within the range of 60
to 75% of 1RM. However, it is possible that this relationship does not hold for
higher loads, as the time under tension is directly linked to oxidative stress
levels, which can directly impact muscle fatigue [24]. A recent study by Aidar et al. [25], revealed that a training session consisting of five sets of five
repetitions at intensities between 80% and 90% of 1RM in Paralympic Powerlifting
athletes did not result in significant oxidative stress. Furthermore, João et al.
[24], demonstrated that performing 15
repetitions at 60% of 1RM or 10 repetitions at 75% of 1RM led to greater caloric
expenditure compared to performing 5 repetitions at 90% of 1RM, and there were no
significant differences in lactate concentrations among these conditions. When
exercises are performed to exhaustion, high levels of oxidative stress are observed,
which subsequently impairs the ability to sustain physical activity [26].
Velocity-based training (VBT) has gained significant attention in recent years;
however, there is still ongoing debate regarding its practicality. Suchomel et al.
[9], reported that using VBT for training
monitoring can be advantageous for novice athletes, but its ability to accurately
track absolute load variations may diminish over extended periods. Conversely,
monitoring based on percentage zones of the one-repetition maximum (1RM) tends to
yield greater variability in strength and power adaptations. However, this method
fails to capture daily performance changes in athletes. According to Jaric [27], there exists a negative correlation
between force and velocity, meaning that as force increases, velocity decreases.
Based on this assertion, it is hypothesized that VBT may be more effective when
combined with controlling training volume based on predefined 1RM loads [28].
Dorrell et al. [29], conducted a study
comparing VBT methods with training based on 1RM zones and found no significant
difference in muscle strength gains between the two methods. However, they observed
a 6% reduction in the total volume of bench press repetitions performed in the VBT
method compared to the 1RM zone-based training. Furthermore, in the study by
Sánchez-Medina & González-Badillo [7], it
was demonstrated that with a lower number of repetitions per set (e. g., 4 reps of 8
possible at 80% 1RM, 4 reps of 6 possible at 85% 1RM, 3 reps of 6 possible at 85%
1RM, and 2 reps of 4 possible at 90% 1RM), there was no significant loss of speed.
In our present study, using 5 repetitions, we did not observe differences in speed
loss during the training sets, and there was no significant speed loss with a load
of 45% 1RM between the pre, post, 24-hour, and 48-hour time points (as shown in
[Fig. 2]
[4]).
Another noteworthy aspect of our study is that irrespective of the load (45% or 80%
1RM) during the concentric phase of the movement, the Mean Propulsive Velocity (MPV)
was consistently lower in the first repetition. This finding contradicts the lifting
profile reported in the study by Sánchez-Medina & González-Badillo [7], where the authors state that the first
repetition is typically the fastest within a set of repetitions. We hypothesize that
the characteristics of our sample may have influenced this profile. The participants
in the study by Sánchez-Medina & González-Badillo were “able-bodied”
individuals, without physical disabilities and with their feet in contact with the
ground [7]. In contrast, our sample comprised
Paralympic Powerlifting athletes who do not utilize their lower limbs for support on
the ground. It has been previously documented that these athletes exhibit lower bar
speeds compared to non-injured competitors [30]. The support provided by the legs on the ground can induce changes in
the kinematics of the movement, thereby influencing the vertical displacement of the
bar [31]. Therefore, it is plausible that the
first repetition, regardless of the load used, is associated with postural
stabilization and adjustment of the body to the adapted flat bench press, resulting
in percentage loss of MPV between for these Paralympic powerlifting athletes.
When comparing the percentage loss of Mean Propulsive Velocity (MPV) between the TRAD
and ECC training methods, it became apparent that the ECC method induced a more
pronounced MPV reduction, as anticipated. This disparity was evident when evaluating
the impact at a 45% 1RM load for both methods (refer to [Fig. 4]
[5]). Surprisingly, after a 48-hour period, when we conducted a
mechanistic assessment of neuromuscular fatigue via MPV at 45% 1RM, these initial
discrepancies ceased to hold statistical significance. Initially, our hypothesis
centered around the notion that ECC training would lead to a heightened level of
neuromuscular fatigue compared to TRAD training, especially after the 48-hour mark.
However, it turns out that this hypothesis did not align with the actual
outcomes.
Bartolomei et al. [32], conducted a study where
participants performed 6 sets of 5 repetitions in the bench press at loads ranging
from 120% to 80% of their 1RM in the ECC training. They found that even after
48 hours, individuals still exhibited impaired performance for power at a load of
30% of their 1RM. In our sample, however, no loss of velocity was observed at
48 hours post-intervention. Although the evaluation methods differed, our study
focused on MPV while Bartolomei et al. [32]
assessed power. The velocity values measured between repetitions during the sets in
both studies were consistently lower compared to the 80% 1RM load (TRAD). Hence,
acute recovery was significantly more negatively affected by the ECC protocol, as
depicted in [Fig. 4].
In another study, both mean velocity and power were evaluated. The 120/80% load of
1RM did not increase speed or power significantly. However, when analyzing a load
range from 120% to 65% of 1RM, there was an increase in speed and power. This
suggests that the eccentric load exceeding the maximum capacity is sensitive to the
load used during the concentric phase of the movement [33].
However, despite yielding relevant results, our study has certain limitations. The
small number of athletes included in the study prevents us from making broad
generalizations. It is also crucial to consider the potential impact of the
athletes’ impairments in order to explain why the first repetition consistently
exhibited inferior performance compared to subsequent repetitions.
Moreover, it is essential to examine the variables’ behavior within specific movement
conditions, particularly during the stick point region of the bench press, to gain a
more comprehensive understanding of the utilization of the leg/bench interface in
Paralympic weightlifting. Therefore, future studies should incorporate additional
morphological, biodynamic, and functional variables that could potentially influence
the performance of Paralympic weightlifting athletes.
In summary, the outcomes of this study indicate that the mechanical indicators of
neuromuscular fatigue, specifically the “Mean Propulsive Velocity,” do not
demonstrate effectiveness within the scope of this particular sample or training
modality. While there existed a notable disparity in MPV for eccentric training
across the pre-training, post-training, and 24-hour intervals, no substantial
decline in MPV was noted for either traditional (TRAD) or eccentric (ECC) training
during the sets, even extending to the 48-hour post-training phase. These findings
corroborate our initial hypothesis while simultaneously refuting the validity of our
second and third hypotheses.
Practical Applications
Bibliographical Record
Márcio Getirana-Mota, Felipe J. Aidar, Frederico Ribeiro Neto, Taísa Pereira Santos, Paulo Francisco de Almeida-Neto, Breno Guilherme de Araújo Tinôco Cabral, Lucio Marques Vieira-Souza, Nuno D. Garrido, Victor M. Reis, Raphael Fabricio Souza. Comparison of Neuromuscular Fatigue in Powerlifting Paralympics in
Different Training Methods. Sports Med Int Open 2024; 08: a22077922.
DOI: 10.1055/a-2207-7922
