Data from: Operating length and velocity of human M. vastus lateralis fascicles during vertical jumping

Humans achieve greater jump height during a counter-movement jump (CMJ)
than in a squat jump (SJ). However, the crucial difference is the mean
mechanical power output during the propulsion phase, which could be
determined by intrinsic neuro-muscular mechanisms for power production. We
measured M. vastus lateralis (VL) fascicle length changes and activation
patterns and assessed the force–length, force–velocity and power–velocity
potentials during the jumps. Compared with the SJ, the VL fascicles
operated on a more favourable portion of the force–length curve (7%
greater force potential, i.e. fraction of VL maximum force according to
the force–length relationship) and more disadvantageous portion of the
force–velocity curve (11% lower force potential, i.e. fraction of VL
maximum force according to the force–velocity relationship) in the CMJ,
indicating a reciprocal effect of force–length and force–velocity
potentials for force generation. The higher muscle activation (15%) could
therefore explain the moderately greater jump height (5%) in the CMJ. The
mean fascicle-shortening velocity in the CMJ was closer to the plateau of
the power–velocity curve, which resulted in a greater (15%) power–velocity
potential (i.e. fraction of VL maximum power according to the
power–velocity relationship). Our findings provide evidence for a
cumulative effect of three different mechanisms—i.e. greater force–length
potential, greater power–velocity potential and greater muscle
activity—for an advantaged power production in the CMJ contributing to the
marked difference in mean mechanical power (56%) compared with SJ.