Below is something I saw on Reddit (lots of crap there but useful stuff too) one of the better summaries I've seen of the research
- The goal of resistance training is to apply tension to muscle. Provided tension is applied, the modality used to do so does not make any difference. This is well established in the scientific literature, experimentally, and is also congruent with our mechanistic understanding of resistance training. People can build muscle with barbells, dumbbells, machines, calisthenics etc. This should be non-controversial
- The "hypertrophy rep range" is actually quite large. Research has shown equal hypertrophy from low load and high load training, provided the sets are taken to, or close to failure. This has been demonstrated from about 5 to 35 reps. Reps higher than 35 still promote hypertrophy (iv'e seen sets in the 70's result in hypertrophy in research), but with a less robust responses, probably because central factors limit the set, and not muscular failure. Again, this is WELL established in the literature at this point, and is not considered controversial in exercise science. It has been replicated over and over again, is congruent with out understanding of the size principle, motor unit recruitment, etc., as well as supported by probably 100+ years of anecdotal experience by bodybuilders. Plenty of old school guys trained with high reps, well before steroids were available. Premise 2 should also be non-controversial at this point.
- Training volume drives gains... to a point. Research looking at how volume impacts hypertrophy pretty reliably shows a dose response, albeit with diminishing returns. The more volume (as in sets close to failure) that you can accumulate AND RECOVER FROM, the better gains, on average, you can experience. ON AVERAGE, more weekly sets is better than fewer sets. Eventually you will likely encounter your maximum recoverable volume (MRV), which varies from individual and WITHIN the individual based on lifestyle factors. It's the point where additional volume will likely have deleterious effects. This is probably quite high for many people, and probably not usually limited my muscular capacity, but rather connective tissue, motivation, etc. This is also well established in the exercise science literature at this point. Your exercise selection has HUGE impacts on how much volume you can recover from each week.
- Frequency is just a function of volume distribution. Weekly volume, regardless of the distribution, has a much greater correlation with hypertrophy than frequency. If anything, some research shows a trend for improved gains with high frequency, but I think this could be an artifact of a new training stimulus, and not due to frequency itself. The meta's on the subject don't support strong independent effects for frequency. There is research showing that distributing a given volume over more sessions reduces the perceived effort to complete the same volume. But ultimately, frequency is simple a function of volume distribution.
When we consider these points, it starts to make sense how a push up, or pull up, can provide enough tension on the muscle to elicit a growth response. As long as an effort threshold is met, ie a set is taken to, or close to failure, repetition range is not particularly important. While you do not have to train to failure to get a growth response, if an exercise it so easy that you are literally unable to hit failure with it even if you tried, then it probably does not have a lot of potential as a hypertrophic stimulus. As long as you can achieve failure with it, and that failure is the result of achieving muscular failure, then the movement still has potential to stimulate growth. As for progressive overload, our ability to do more is the result of the adaptions we experience from crossing this effort threshold- not the other way around. Doing more reps, doing them with better form, doing them weighted, doing more volume, doing them with better mind/muscle connection is a function of getting stronger.
For my personal history... I've been training since I was a kid. Calisthenics have always been a huge part of my training, even when I was lifting. It's difficult to attribute what development was from what modality, and I don't think of it like this. I look at
all exercise as a tool to apply mechanical tension, and I don't consider a push up to be, in that respect, fundamentally different than a bench press insofar as they are both tools to apply tension to the pushing musculature. To me, the question of trying to figure out what exercises account for what gains is really the wrong question to ask. It's all the same. Certainly deadlifts train
more of the bodies musculature than pull ups, but they both can build pretty awesome backs.