If you lift lighter weights with only 30 seconds of rest between sets, your body might spike growth hormone and make your muscles look bigger right after the workout—more than if you lift heavier weights and rest for 3 minutes between sets, as long as the total amount of lifting is the same.

A randomized crossover trial in healthy adults comparing two conditions: (1) low-load (20 RM) resistance training with 30-second rest intervals and (2) high-load (8 RM) resistance training with 3-minute rest intervals, matched for total volume. Growth hormone levels and muscle thickness (via ultrasound) are measured immediately after each session. Each participant completes both conditions in random order with a washout period between.

A parallel-group RCT with two arms: one group performs low-load (20 RM) training with 30-second rests, the other high-load (8 RM) with 3-minute rests, both volume-matched. Acute growth hormone and muscle thickness changes are measured after a single session. Participants are randomly assigned and blinded to condition where possible.

A single-group study where healthy adults perform both training protocols (low-load/30s rest and high-load/3min rest) on separate days in randomized order. Growth hormone and muscle thickness are measured pre- and post-exercise on each day to quantify acute changes within individuals.

An observational study tracking healthy adults who self-select either low-load/short-rest or high-load/long-rest training routines. Acute growth hormone and muscle thickness changes are measured after a single training session under controlled conditions to assess naturalistic associations.

A case series reporting acute growth hormone and muscle thickness changes in a small group of healthy adults following both training protocols in sequence, without randomization or control group, to describe patterns of response.