In moderately trained men, bench press protocols involving 3, 15, and 24 repetitions at 70% one-repetition maximum, with individualized inter-repetition rest, produce equivalent increases in blood lactate concentration post-exercise, indicating that metabolic stress is determined by fatigue accumulation rather than total repetitions performed.

When people do bench presses with short breaks between each rep, their muscles get time to clear out waste products like lactic acid and hydrogen ions before they build up too much. This keeps the muscle from getting too tired too fast, so even if they do more reps, the amount of lactic acid in the blood ends up the same as when they do fewer reps. The key is how tired the muscle gets, not how many reps they do.