Stimulation of muscle fibers at a rate of 20 to 40 stimuli per second produces no relaxation of the muscle before the next stimulatory event. this type of muscle stimulation is referred to as what?

Wave Summation.

Explanation:

Wave summation may be defined as the increase in the muscle frequency by which the muscle has been stimulated and increase the contraction strength.

Wave summation occurs because of muscle stimulation before it has released the previous stimuli. The new stimulation arises 20 to 40 stimuli per second and the previous stimuli continues. This produces the wave like pattern known as tetanus.

Thus, the answer is wave summation.

i think its pulmonary not sure tho