Abstract
We assessed the time course of running mechanical alterations during an 800-m. On
a 200-m indoor track, 18 physical education students performed an 800-m self-paced
run. Once per lap, ground reaction forces were measured by a 5-m-long force platform
system, and used to determine running kinetics/kinematics and spring-mass characteristics.
Compared with 100 m (19.4±1.8 km.h−1) running velocity progressively decreased at 300, 500 m but levelled-off at 700 m
marks (−5.7±4.6, −10.4±8.3, and −9.1±13.5%, respectively; P<0.001). Stride length
(−8.5±2.3%, P<0.01) and frequency (−1.0±1.5%, P=0.05) along with peak braking (−7.5±4.4%,
P<0.05) and push-off forces (−5.1±7.2%, P<0.05) decreased from 100 m to 700 m. Peak
vertical forces (−3.0±2.7%; P>0.05) and leg compression (+2.8±3.9%; P>0.05) remained
unchanged, whereas centre of mass vertical displacement (+24.0±7.0%; P<0.001) increased
during the run. Vertical stiffness decreased (−18.1±4.4%; P<0.001), whereas leg stiffness
was unchanged (−3.2±4.6%; P>0.05). During an 800 m by physical education students,
highest running velocity was achieved early during the run, with a progressive decrease
in the second half of the trial. While vertical ground force characteristics remained
unchanged, non-specialist runners produced lower peak braking and push-off forces,
in turn leading to shorter stride length. Spring-mass model characteristics changed
toward lower vertical stiffness values, whereas leg stiffness did not change.
Key words
leg spring behaviour - stride parameters - stiffness - pacing strategy - middle distance
running
