Twitch contractions: All data were 15Hz low pass filtered and peak torque and rise-time were calculated before and after the tetanic stimulation period. For each 10-twitch series peak torque and rise-time (the slope between 30% and 70% of the twitch peak force, Nm/s) was calculated for the individual twitches. Both peak torque and rise-time were then expressed as the average values of all twitches before and after the tetanic contraction.