Changes in muscle force-length properties affect the early rise of force in vivo.
Computing, Health and Science
Exercise, Biomedical and Health Science, Centre for Exercise and Sports Science Research
Changes in contractile rate of force development (RFD), measured within a short time interval from contraction initiation, were measured after a period of strength training that led to increases in muscle fascicle length but no measurable change in neuromuscular activity. The relationship between training-induced shifts in the moment–angle relation and changes in RFD measured to 30 ms (i.e., early) and 200 ms (i.e., late) from the onset of isometric knee extension force were examined; shifts in the moment–angle relation were used as an overall measure of changes in quadriceps muscle fascicle length. A significant proportion of the variance in RFD measured only in the initial contraction phase (0–30 ms) could be explained by shifts in the moment–angle relation (r = −0.66–0.71; R2 = 0.44–0.50). Training-induced increases in muscle fascicle length may lead to a reduced or complete lack of adaptive gains in contractile RFD, especially in the early contraction phase. Muscle Nerve 39: 512–520, 2009