After a 5 min recovery period the sequence was repeated. Comparison was made between the fatigued and recovered state in each preparation in order to allow for any change in the preparation during the course of the experiment. After 15 s contraction the fatigued muscles showed a marked reduction in all parameters measured. In fatigued muscles the isometric force fell to 48 +/- 15% (mean +/- SD) and there was a decrease in maximum velocity of shortening to 66%. These changes in the force-velocity relationship were accompanied by slowing of relaxation so that the half time of relaxation nearly doubled. The consequence of these changes was that the maximum power output was reduced by a much greater extent than was the isometric force (75% vs. 52%). It is suggested that the changes in force-velocity characteristics reflect a reduction in cross-bridge cycling in fatigued muscle
The data for this research was collected in the Academic Medical Centre of the University of Amsterdam using an experimental model developed by Arnold de Haan who was a PhD student of Professor Anthony Sargeant. The collaboration with Professor David A Jones was central to the design and interpretations of this study.
Changes in velocity of shortening, power output and relaxation rate during fatigue of rat medial gastrocnemius muscle
Pflugers Arch. 1989 Feb;413(4):422-8