When it comes to optimizing muscle growth, the debate around using a partial versus full range of motion (ROM) in training remains contentious. Some argue that lifting heavier weights with partial ROM leads to greater gains, while others advocate for a full ROM to engage the muscles fully. Let's break down these arguments and explore the science behind them to see which approach is more effective for building muscle.

Range of motion refers to the distance a joint moves during an exercise. A full ROM means going through the entire movement potential of a joint, while a partial ROM means limiting the movement to a specific portion, such as stopping midway through a squat or a bench press.

The case for Partial Range of Motion

1. Moving heavier weights with partial ROM

One common argument for partial ROM is that it allows you to lift more weight. By cutting down the movement range, you can load the bar heavier than you could with full ROM. However, this doesn’t necessarily translate to greater muscle tension or volume. Training volume, often calculated as sets x reps x weight x distance, takes into account both the load and the distance the weight moves. Therefore, when using heavier weights but reducing the distance of movement, total training volume can actually decrease.

For example, a squat with 225 lbs over a full ROM may generate more training volume than a partial squat with 315 lbs because the shorter distance cancels out the heavier load. As a result, the muscle doesn’t experience greater tension or workload, which limits hypertrophy potential.

2. Constant tension on the muscle

Another argument in favor of partial ROM is maintaining constant tension on the muscle. By keeping the movement in the middle range of an exercise, you avoid the “mini-rests” that occur at the top or bottom of the motion. This theory suggests that keeping muscles constantly engaged could lead to more muscle growth.

A 2017 study on skull crushers supports this idea. Participants who performed the exercise with a restricted mid-range saw greater muscle growth than those using a full ROM. However, it’s worth noting that this advantage is mainly observed in isolation exercises, where the end range of the motion may be easier. For compound exercises like squats or deadlifts, where the entire range of motion is essential, full ROM is likely still more beneficial.

3. Anecdotal evidence from bodybuilders

Many professional bodybuilders use partial ROM in their routines, particularly IFBB pros, which may lead some to believe that partial reps are better for muscle growth. However, while this might be true for some exercises or advanced athletes, these anecdotes lack the rigorous control found in scientific studies. Many factors, including genetics, nutrition, and other training methods, contribute to their success, making it hard to pinpoint the effectiveness of partial ROM alone.

The case for Full Range of Motion

1. Full ROM maximizes muscle activation

Scientific studies generally support full ROM for muscle growth. In exercises like squats and lunges, a full ROM engages the entire muscle, leading to more significant development. For instance, research comparing deep squats to heavier partial squats showed that despite using lighter weights, the full ROM squats resulted in greater hypertrophy, particularly in the quadriceps.

2. More volume, more gains

When using a full ROM, the muscle undergoes a longer time under tension and experiences a larger training volume. This makes full ROM more effective for stimulating hypertrophy in most cases. Studies examining lower body movements consistently find that full ROM outperforms partial ROM for muscle growth, especially in compound lifts.

3. Consistency with scientific evidence

A systematic review of six studies on ROM and hypertrophy reveals that most support the full ROM approach, particularly for lower body exercises. The upper body results are more mixed, with some exercises benefiting from partials, but full ROM still generally produces better overall growth.

When Partial ROM Makes Sense

While full ROM is typically superior for muscle growth, partial ROM can be useful in specific scenarios:

• Isolation exercises: In movements like lateral raises, dumbbell flyes, or skull crushers, the top or bottom of the range often offers little resistance. Skipping these portions can keep constant tension on the muscle, making partial ROM beneficial.
• Advanced training techniques: For experienced lifters, using partial reps after reaching failure with full ROM can help extend a set and further exhaust the muscle. This is particularly effective when targeting stubborn body parts.
• Powerlifting goals: For powerlifters, maximizing weight moved in a competition often takes priority over muscle growth. Techniques like using a bench press arch or a sumo deadlift stance may limit ROM but still focus on hitting the hardest part of the lift.

Conclusion

For most lifters, training with a full range of motion will result in better muscle growth, especially in compound lifts and lower body exercises. Full ROM ensures that the muscle experiences maximum tension across its entire length, leading to more significant hypertrophy over time. However, partial ROM can be an effective advanced technique for isolation exercises or extending sets beyond failure.

Ultimately, combining the best of both worlds—prioritizing full ROM while strategically using partial reps—can provide optimal results for muscle growth.