Fatigue envelopes for different stimulation protocols. Hind limb muscles are stimulated with trains of either 100 or 200 ms at either 1 or 2 s intervals. Each stimulation protocol generates different peak forces, plateau force durations, and fatiguing slopes. Both 200 ms protocols showed the highest maximum force, but no sustainable plateau. The 100 ms at 1 s interval protocol was chosen, because it showed a sustained force plateau and fatigued the muscles in less than 4 minutes. Error bars are mean ± SEM.