Range of Motion and Long Muscle Length: "Full ROM Isn't Always Better"

For years, the rule taught to every coach was clear: "Do every rep with full range of motion." That rule still largely holds; but meta-analyses published between 2023 and 2025 added an important nuance. The question isn't "full or partial"; it's which region the partial is done in.

What does the science say?

Wolf and colleagues' 2023 meta-analysis (IJSC) found a small advantage in favor of full ROM (SMD 0.12). But the striking finding in the same analysis is this: partial ROM at a long muscle length can produce slightly more hypertrophy than full ROM (SMD −0.28).

Havers and colleagues (2025) trained 13 trained individuals on preacher curls for 8 weeks. When long-muscle-length partials (0–70°) were compared with full ROM (0–140°), similar thickening was seen at the muscle's midpoint; in the distal (near the end) region, the long position partial had a slight edge.

Zabaleta-Korta and colleagues (2023) showed that movements applying tension at a long muscle length, such as the preacher curl, produced more distal growth.

The critical nuance: which partial?

We need to highlight the most common mistake made here. The same studies show that partial ROM at a short muscle length (i.e., lockout, top-range reps) produces less hypertrophy than full ROM. So it's not "partial reps are good"; it's "partial reps at a long muscle length are good." Conflating the two leads to training the client inefficiently.

The mechanism makes sense too: at a long muscle length, both active (titin) and passive tension are high, and this can trigger the addition of sarcomeres in series.

Practical rules for the coach

1. Full ROM is still the standard. For beginners, with a mobility goal, and for movement learning, this is the default.
2. At an advanced level, make one exercise a "long-position partial": the bottom half of the RDL, the bottom half of the preacher curl, the bottom half of the hack squat, the long-position half of the leg curl.
3. If you're targeting distal muscle growth, bring long-muscle-length variations to the front.
4. Don't expect hypertrophy from lockout-only reps. Their place is strength/neural adaptation, not mass.
5. Periodize: 4 weeks full ROM → 2–3 weeks long-position partials → return to full ROM.

In conclusion, it's more accurate to update the rigid rule "full ROM is always better" to "full ROM is the safe foundation, long-position partials are a powerful tool, and short-position partials are usually a waste."