How to Use Lengthened Partials for Maximum Muscle Growth

When it comes to building strength and muscle, most people are told to “use a full range of motion.” While that’s sound advice, research in recent years has shown that training in the stretched position, using what’s known as lengthened partials, can be just as effective, and sometimes even better for certain muscle groups.

Here’s what the science says:

• “Lengthened partial repetitions and full range of motion resistance training … resulted in similar muscle thickness and 10-repetition-maximum improvements … suggesting that trainees seeking to maximize muscle size should likely emphasize the stretched position, either by using a full ROM or lengthened partials.” (ResearchGate)

• “Partial ROM training in the initial phase of the knee extension exercise promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations.” (PubMed)

• “Our results suggest that using a full or long ROM may enhance results for most outcomes… however, differences in adaptations are trivial to small. As such, partial ROM resistance training might present an efficacious alternative … or where injury prevents full-ROM resistance training.” (IUSCA Journal)

Research Summary & Key Takeaways

Overall, the research on lengthened partials suggests they can provide meaningful benefits for muscle growth, especially because training in the stretched position seems to stimulate muscle fibers in a way that full range of motion alone may not fully match.

Most of the current studies have been conducted on untrained individuals, which means we can’t say with certainty that the exact same results apply to experienced lifters. That said, there’s no evidence to suggest that incorporating lengthened partials will harm your progress. They may even give your training an extra edge.

If you’re already following a solid strength program, experimenting with a few sets of lengthened partials could help:

• Increase time under tension in a muscle’s most stretched position

• Potentially boost hypertrophy without needing to add more total training volume

• Reduce joint strain compared to full-range lifting in some exercises

Bottom line: You can’t go wrong by trying them. Just start light, focus on control, and pay attention to how your muscles (and joints) respond.

How to Use Lengthened Partials in Your Training

If you want to try lengthened partials, here are some tips:

1. Choose the Right Movements
   Focus on exercises where the stretched position is challenging. For example, incline dumbbell curls (stretch at the bottom), Romanian deadlifts (stretch at the bottom), or cable chest flys with a deep stretch.

2. Keep the Tension
   Avoid bouncing or using momentum in the stretched position. The point is to keep tension on the muscle fibers while they are elongated. You can try adding a 1-2 seconds pause before shortening the muscle.

3. Use Moderate Loads
   Heavier weights can compromise form and range. Aim for a load you can control for 5-50* quality reps working close to failure.

   * Research suggests hypertrophy can be achieved across a broad rep range (anywhere from 5 to 50 reps) as long as you work close to failure (Schoenfeld et al., 2017).
   For lengthened partials, choose a rep range that matches your goal and equipment. Heavier loads (5–8 reps) for strength focus, moderate loads (8–15) for balanced size and strength, or higher reps (15–30+) for more metabolic stress.

4. Combine with Full ROM Training
   While lengthened partials can stand alone, most lifters see the best results by combining them with traditional full range movements over the course of a training block.

In short, while lengthened partials aren’t a magic bullet, they’re a low-risk, potentially high-reward tweak that could help you unlock new muscle growth and keep your training fresh.