Originally Posted by constant struggle
Kinda hard to do until you're well-accustomed to traiing theory, but basically different muscles respond differently to different workloads. It's why walking doesn't give you huge thighs and all that but someone who starts running might increase the size of their legs slightly. Someone who does bodyweight squats can increase it even more. There's a ton of shit that goes on, but basically for most muscles the easiest way to figure out how much hypertrophy will result is the total workload per week at 50-60%+ of your current 1 rep maximum. Essentially, think of it this way: you're doing squats. Your 1 rep maximum is 100lbs. The total workload per week is the number of sets done per week with at least 50lbs on the bar. Say your workouts are like this: Monday: 3 sets of 8 with 50lbs. Wednesday: 1 set of 2 with 90lbs. Friday: 5 sets of 5 with 70lbs. Monday's workload is 1200 (3x8x50), Wednesday's is 180 (2x90), and Friday's is 1750 (5x5x70). Now imagine you changed the Friday workout to be 5 sets of 8 with 50lbs. The weight is lower, but the total workload then becomes 2000lbs. That's kinda the reason workouts go in sets. If you were to try and do a 2000 workload with 1 set you'd end up trying to do 40 squats at a time with 50lbs. or 20 squats of your 1 rep maximum (100lbs.). Well, that obviously doesn't work, so you break them up into sets. So why squat three times per week? Frequency factors into the total workload as well -- imagine doing 1 set of 2 with 80lbs, then 3 sets of 8 with 50lbs, then 5 sets of 5 with 70lbs. You just did the week's workout in one day. Basically, this isn't possible. Your legs will be fried halfway through and you can't complete the week's workload. By getting a day of rest in between you'll allow a higher total workload per week. (Digression: this is one reason why drugs are so potent -- a quicker recovery time means a higher workload can be achieved) Anyway, the reason why doing 15 reps of something will still produce more size is simply mathematics. If you were doing 50lb. squats and started off doing a set of 5, working up to 8, then eventually doing 15 the total workload rises as well. Set of 5: 250 Set of 8: 400 Set of 15: 750 It doesn't work this way forever because of the way muscles function (your total 1 rep maximum will rise, and eventually the 50lbs. will be too light to produce more growth is an easy way to look at it). The cutoff for 1rm and percentages changes with the muscle as well -- smaller muscles tend to get stronger or grow in size more based on lower 1rm percentages than larger muscles. The rectus femoris (big quadricep muscle) might need an intensity of at least 50% of the 1rm to produce growth whereas the brachialis (tiny forearm muscle) might grow from a 20% intensity. It's probably all discombobulated, but I hope this helped.