5.3.2: Practical Rep Range Selection

• Heavy compounds (4–8 reps): On stable, multi‑joint exercises like the leg press, squat, or bench press, low‑rep work allows very high loads to be used with full motor unit recruitment from rep one. The exercise is supported by a large muscle mass and external stability, so form can be maintained even at near‑maximal loads.

• Moderate‑range isolation (6-10 reps): For the vast majority of isolation exercises—lateral raises, bicep curls, tricep pushdowns, leg extensions, hamstring curls—moderate rep ranges are the sweet spot. Going too heavy (e.g., a 4RM lateral raise) forces excessive momentum and compromises isolation. Staying in the 6-10 range provides a balance of sufficient load for early recruitment and enough reps for the target muscle to approach failure before stabilisers fail or technique breaks down. This is where the majority of hypertrophy work should land.

Training above 12 reps is often practically inefficient; the systemic fatigue and discomfort outpace the hypertrophic benefit compared to moderate rep ranges. Once you cross that threshold, the compound interest paid in fatigue, discomfort, and set duration buys you nothing you could not have achieved more efficiently with a heavier load in the 6-10 range. The few exceptions—side delts, calves, maybe rear delts—are muscles so small and fatigue‑resistant that the practical drawbacks of high‑rep work are less pronounced, but even there, moderate rep work with heavier loads works just as well and takes half the time.

As always, the rep range is a tool, not a rule. If you enjoy high‑rep pump work as a finisher, it is not harmful. But if you are relying on 20‑rep sets as a primary growth driver because you believe they somehow target different fibers, you are making your training harder for no good reason.