TRT in the UK
Scientific Recommendations for Strength and Hypertrophy Training from 150+ Studies (part 1 of 3
Training a muscle group 2-3 times per week seems to be better than 1 time per week for hypertrophy 1. In terms of strength, the picture is more unclear. More training days allow you to do more volume.
According to volume-unmatched research 2, training a muscle group 2-3 times per week is superior to once a week for strength development (given that higher frequency = more volume). Remember that this recommendation doesn’t account for periodization. Several research teams think that sticking to one frequency year round is suboptimal.
Isolation vs. compound exercise
Isolation exercise has its uses in rehab, injury prevention, muscle imbalance correction, recovery, programming, and bodybuilding. There isn't much evidence that isolation exercise is required to maximize gains. At least not in “mirror muscles”. Yet, it is possible that a muscle group needs to be hit by different compound exercises to maximize growth (i.e. the bench press suboptimally stimulates triceps growth compared to the pectorals). Isolation exercise is particularly useful for certain muscle groups like calves, rotator cuff, etc.
You can order exercises based on how important they are to you and what your strengths/weaknesses are. The most important exercise(s) should be done first in the session if you want to maximize the amount of reps you can do. Debates are raging about what’s ideal for hypertrophy and strength. There’s a slight trend for better gains in the exercises you do first in a training session. However, we can’t say this is highly probable, because there’s not enough studies. Remember that science deals with probabilities rather than certainties.
Going to failure early in an exercise decreases the number of reps you can do in later sets and limits volume. Excessive use of failure can lead to overuse injuries, fatigue, overreaching, etc. Some researchers recommend going to failure occasionally, but the evidence is mixed and we don’t know what’s ideal for the long-term. You can make good gains without going to failure, but as always, it depends on other factors like frequency, intensity, volume, rest durations, and so on.
Rest between sets
Generally speaking, short rest periods reduce the amount of reps you can do in subsequent sets. Longer rests 3 are better for developing strength and when you're training at high intensities to failure. For hypertrophy, you are free to choose your rest interval. You can choose shorter rests, but you have to account for things like: Did you go to failure? How many reps are you doing the exercise for? At what intensity? How important is it for you to hit your target reps per set?
Range of motion (ROM)
Full range of motion generally causes more muscle hypertrophy, but partial ROM can cause site-specific hypertrophy. Strength is specific to the ROM you are using, but you can gain strength 20-30 degrees outside of the ROM you train with. Partial ROM lifts can be used in addition to full ROM to break through sticking points or weak points. Trained and advanced lifters might want to periodically include partial ROM training into their programs.
There is no cookie-cutter program that will be ideal for everyone, however some programs are better than others
More frequency/failure/intensity isn’t necessarily better
Individual variability (genetics, epigenetics) affects how your body adapts to exercise. If a program doesn’t work after months of trying, you might want to switch to something with different movements, frequencies, more/less volume, intensity, etc. This principle applies even if you’re doing something that is “ideal”, on paper.
Many studies use untrained college-aged men as participants, study durations are short (6-12 weeks), there is little ecological validity, and several of the studies have methodological issues.