Data from: Muscle-tendon unit length changes differ between young and adult sprinters in first stance phase of sprint running

The aim of this study was to compare young and adult sprinters on several
biomechanical parameters that were previously highlighted as
performance-related and to determine the behaviour of several
muscle-tendon units (MTU) in the first stance phase following a block
start in sprint running. The ground reaction force (GRF) and kinematic
data were collected from 16 adult and 21 young well-trained sprinters. No
difference between the groups was found in some of the
previously-highlighted performance-related parameters (ankle joint
stiffness, the range of dorsiflexion and plantar flexor moment).
Interestingly, the young sprinters showed a greater maximal and mean ratio
of horizontal to total GRF, which was mainly attributed to a greater
horizontal GRF relative to body mass and resulted in a greater change in
horizontal centre of mass (COM) velocity during the stance phase in the
young compared to the adult sprinters.. Results from the MTU length
analyses showed that adult sprinters had more MTU shortening and higher
maximal MTU shortening velocities in all plantar flexors and the rectus
femoris. Although previously-highlighted performance-related parameters
could not explain the greater 100 m sprinting times in the adult
sprinters, differences were found in the behaviour of the MTU of the
plantar flexors and rectus femoris during the first stance phase. The
pattern of length changes in these MTUs provide ideal conditions for the
use of elastic energy storage and release for power enhancement.