Abstract
From 24 vertical jumps (eight subjects, three jumps each), calculations of forces,
torques, and power per joint were combined with EMG data of eight leg muscles and
with estimations of their contraction velocities. In the second part of the push-off,
a high power output of 3000-4000 W was delivered in the ankle joints during plantar
flexion. This is attributed to a sequential energy flow from hip to knee and ankle
joints. Through coordinated actions of both the m. gluteus maximus and the m. rectus
femoris as well as the m. vastus med., intermedius and lat. (mm. vasti) and the m.
gastrocnemius, power delivered by the monoarticular extensors of the hip and knee
joints was transported distally via the biarticular muscles to the ankle joints. During
the high plantar flexion velocity at the end of the push-off, hip and knee joints
showed high extension velocities resulting in relatively low contraction velocities
for the biarticular muscles. As a consequence they could deliver high forces, which
allowed them to transport energy in a proximodistal direction and allowed them to
decelerate the angular velocities of the hip and knee joints without losses due to
eccentric contractions.
It is concluded that this power transport is essential in the execution of explosive
movements.
Key words
Polyarticular muscles - countermovement jump - energy flow - explosive movement
