Some thoughts on resistance exercise from my recent reading - factors affecting benefits include the following:

Volume of work done - the more the better, but with lots of provisos.

Sets must be done as close to task failure as possible to obtain maximum benefit.

First sets - to failure - provide as much benefit as the next 3 - 5 sets.

Task failure is a decision - the relevant muscle could do at least 1 more rep, but we decide that the effort involved is not worth it.

It is not necessary to cause muscle soreness to benefit.

Training when muscles are still sore provides little if any benefit.

Training frequency at a given volume: up to a point higher frequency is better as then more first sets are done.

Muscle soreness is not due to tears in the muscle - it is due to Calcium ion movement which in turn incites an inflammatory response and the inflammation is what causes damage - followed by repair.

The benefit of repeating the same number of sets and reps will soon plateau - a change in stimulus is needed.