The high energetic cost of rapid force development in muscle

ABSTRACT Muscles consume metabolic energy for active movement, particularly when performing mechanical work or producing force. Less appreciated is the cost activating muscle quickly, which adds considerably to overall of cyclic force production. However, magnitude relative work, features in many movements, unknown. We therefore tested whether fast activation costly compared with isometric hypothesized that would increase a proposed measure termed rate (rate force) tasks, separate from average level. humans (N=9) knee extension torque against an dynamometer (torque 22 N m, waveform frequencies 0.5–2.5 Hz), while also quantifying quadriceps and series elasticity (with ultrasonography), along through respirometry. Net increased by more than four-fold (10.5 46.8 W) frequency. At high frequencies, force-rate accounted nearly half (40%) expenditure. This exceeded (17%) was comparable shortening (43%). The explained additional calcium transport necessary forces at increasing owing rate-limiting dynamics could contribute substantially movements require activation, such as locomotion.