What reaction must occur to release the energy in atp

respiration

Explanation:

The source of the energy required to regenerate ATP is the chemical energy stored in food (e.g. glucose)

it also supports my hypothesis. if you rest first you can squeeze the clothespin more times. from the data i collected the average of the eight people concluded exercise makes your muscles more fatigued and less able to squeeze the clothespin compared to resting before squeezing.