Describe the condition in muscles that produces the effect called tetanus. Why do most human movements involve tetanic contractions? Explain why muscles cannot sustain a tetanic contraction for more than a short time. What causes fatigue in muscles?
When the stimulations do not allow the muscle to relax at all between stimuli, individual contractions fuse together into a single sustained contraction called a tetanus. Like the contractions produced during the condition of summation, a tetanic contraction is produced by adding the contractions of the individual stimuli together. A tetanic contraction is a muscle's greatest response, and most human movements involve tetanic responses due to the rapid fire of nerve impulses produced by most stimuli. A muscle cannot sustain a tetanic contraction for more than a short period of time before fatigue sets in. Fatigue is caused by the build up of lactic acid and by the depletion of the muscle's energy reserves.
