Abstract
Marathon running involves complex mechanisms that cannot be measured with
objective metrics or laboratory equipment. The emergence of wearable sensors
introduced new opportunities, allowing the continuous recording of relevant
parameters. The present study aimed to assess the evolution of stride-by-stride
spatio-temporal parameters, stiffness, and foot strike angle during a marathon
and determine possible abrupt changes in running patterns. Twelve recreational
runners were equipped with a Global Navigation Satellite System watch, and two
inertial measurement units clamped on each foot during a marathon race. Data
were split into eight 5-km sections and only level parts were analyzed. We
observed gradual increases in contact time and duty factor as well as decreases
in flight time, swing time, stride length, speed, maximal vertical force and
stiffness during the race. Surprisingly, the average foot strike angle
decreased during the race, but each participant maintained a rearfoot strike
until the end. Two abrupt changes were also detected around km 25 and km 35.
These two breaks are possibly due to the alteration of the stretch-shortening
cycle combined with physiological limits. This study highlights new measurable
phenomena that can only be analyzed through continuous monitoring of runners
over a long period of time.
Key words
biomechanics - temporal parameters - foot strike - stiffness, fatigue