Volume or Effort?
What Actually Builds Muscle.

There are two camps. One says volume is king: count your weekly sets per muscle, push them up, grow. The other says it's all about effort: a few sets to absolute failure beat twenty sets of going through the motions. Both camps are quoting real research. Both are describing half of one rule.

What the volume research actually counts

The dose-response studies that found more sets means more growth^[1][2] didn't count any set. They counted sets taken near failure. That's the unit. A set at six reps in reserve isn't in the data, so the finding that twenty sets beat ten says nothing about twenty easy sets. Volume is the dial, and a set only turns it if it's hard.

What the effort research actually says

Closeness to failure matters, with a small, consistent edge for sets taken nearer to it.^[3] A meta-regression of 55 hypertrophy studies found growth rising as sets got closer to failure, while strength did slightly better with a rep or two in the tank.^[4] But the effect is modest. Going from two reps short to zero adds a little. It doesn't replace sets. Four sets to failure don't beat twelve sets at two reps from it.

Effort decides whether a set counts. Volume decides how many count. You need both, and neither replaces the other.

Where each one stops paying

Volume has diminishing returns that are now mapped: growth keeps rising past twenty weekly sets but the extra from each set shrinks, and per session the returns tail off around eleven hard sets for a muscle.^[1][5] Effort has a cost too. Sets to absolute failure take more out of you than sets one or two reps short, which means fewer good sets later in the week. The best place for most lifters is one to three reps from failure on most sets, with the last set of an exercise taken closer, and enough hard sets a week to sit in the productive range.

How the app sets that effort target week to week is in why your plan should tell you when to push.

The catch: people can't tell

Reps in reserve is a skill. Across 12 studies, lifters underestimated how many reps they had left by about one on average, and beginners by four or five.^[6] So "two from failure" means something different to a new lifter than it does after a year. The estimate gets better the closer you are to failure and the more you practise it. That's an argument for occasionally taking a set all the way, to recalibrate, not for always doing it.

What the app does

Coast counts both. Every exercise's sets are tallied per muscle per week, with secondary muscles counted at half, and each muscle is kept inside its productive range. Every set carries a reps-in-reserve target that drops through the block, so a set of 12 in week one is easier than a set of 12 in week four at the same weight. The hard sets are the ones that count. The app makes sure you do enough of them and not more.