Physioex 8.0 exercise 2 review sheet

Hey everyone I'm trying to finish my review sheet but there are a few questions that I don't understand

5) In Activity 4, you looked at the effect of stimulating the muscle multiple times in a short period with complete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus.
6) Describe the chemical changes that are thought to correlate to this change in vivo.
8) Compare and contrast wave summation with recruitment (multiple motor unit summation). How are they similar? How was each achieved in the stimulation?