Leg muscle growth is a critical goal for many gym-goers, but debates around training protocols, specifically high-rep vs low-rep training, often leave people uncertain about the best approach. Both methods can be effective depending on individual goals, fitness levels, and other factors.
This article will dissect the science behind these strategies, explore their benefits and drawbacks, and provide actionable insights backed by research.
The Basics of Muscle Growth
Muscle growth, or hypertrophy, occurs when muscle fibres are subjected to mechanical tension, metabolic stress, and muscle damage during resistance training. These stimuli activate pathways that lead to protein synthesis and muscle repair, causing an increase in muscle size (Schoenfeld, 2010). Repetition range, volume, intensity, and rest periods all influence how these factors interact to promote hypertrophy.
High Reps vs Low Reps: Defining the Terms
High Reps
High-rep training generally involves performing 12–20 repetitions per set, using lighter weights (typically 50–70% of an individual’s one-repetition maximum, or 1RM). This approach focuses on muscular endurance and metabolic stress, which can contribute to hypertrophy through cell swelling and an increased time under tension (TUT) (Wackerhage et al., 2019).
Low Reps
Low-rep training involves 1–6 repetitions per set, using heavier loads (generally 75–95% of 1RM). This approach primarily targets maximal strength and the recruitment of high-threshold motor units, which play a significant role in hypertrophy due to their larger size and potential for force production (Schoenfeld et al., 2014).
Scientific Comparison: High Reps vs Low Reps for Leg Growth
Mechanical Tension
Mechanical tension is a primary driver of hypertrophy and is maximised when lifting heavy loads, making low-rep training particularly effective for this purpose. Heavy loads increase the recruitment of type II muscle fibres, which have the highest potential for growth (Henneman et al., 1965). However, high-rep training can still produce significant mechanical tension, especially when performed to failure, as this recruits a greater range of muscle fibres over time (Morton et al., 2016).
Metabolic Stress
High-rep training induces greater metabolic stress due to the accumulation of metabolites like lactate and hydrogen ions. This stress triggers hypertrophic signalling pathways such as the mammalian target of rapamycin (mTOR) and increases hormonal responses, including growth hormone release (Schoenfeld, 2013). However, studies suggest that metabolic stress alone is insufficient for maximal hypertrophy and must be combined with mechanical tension (Dankel et al., 2017).
Time Under Tension
High-rep sets naturally create longer TUT, which enhances metabolic stress and can improve muscle protein synthesis rates. Low-rep sets, while shorter in duration, produce high tension per repetition, making them equally important for hypertrophy when integrated into a balanced programme (Schoenfeld et al., 2016).
Training Volume
Total training volume (reps × sets × weight) is a critical determinant of hypertrophy. High-rep training allows for higher total volume due to lighter loads and more repetitions per set. However, low-rep training can achieve similar volumes when higher set numbers are employed (Schoenfeld et al., 2017).
Advantages and Disadvantages of Each Approach
High Reps
Advantages
- Increased Metabolic Stress: Promotes muscle endurance and vascularisation.
- Joint-Friendly: Lower loads reduce the risk of joint strain and injury.
- Accessible for Beginners: Easier to learn and execute with proper form.
Disadvantages
- Limited Strength Gains: Does not maximise neural adaptations for strength.
- Fatigue Accumulation: Higher risk of cardiovascular fatigue impacting performance.
- Less Effective for Type II Fibres: Lower loads may not fully stimulate high-threshold motor units.
Low Reps
Advantages
- Maximal Strength Gains: Enhances neural drive and type II fibre recruitment.
- Efficient for Tension: Fewer reps with heavier weights optimise mechanical tension.
- Time-Efficient: Shorter sets save time without sacrificing effectiveness.
Disadvantages
- Increased Joint Stress: Higher loads can strain joints and connective tissues.
- Risk of Injury: Poor form under heavy loads increases injury potential.
- Lower Training Volume: Fewer reps per set may reduce total metabolic stress.
What Does the Research Say?
Studies consistently demonstrate that both high-rep and low-rep protocols can induce hypertrophy when total volume is matched. A study by Morton et al. (2016) found no significant difference in muscle growth between low-rep (3–5 reps) and high-rep (20–25 reps) training groups when participants trained to failure. Another meta-analysis by Schoenfeld et al. (2017) concluded that hypertrophy is achievable across a broad rep range, with volume being the most critical factor.
However, research also highlights the benefits of combining rep ranges. A study by Ralston et al. (2017) suggests that mixed rep ranges optimise both hypertrophy and strength gains by targeting different fibre types and training adaptations.
Practical Application: How to Structure Your Training
Periodisation
Combining high-rep and low-rep training in a periodised programme can maximise leg growth. For example:
- Weeks 1–4: Focus on high-rep sets (12–15 reps) to build muscular endurance and volume.
- Weeks 5–8: Shift to low-rep sets (4–6 reps) to enhance strength and tension.
- Weeks 9–12: Integrate both strategies by alternating rep ranges within the same week.
Exercise Selection
Incorporate compound lifts like squats, deadlifts, and leg presses, which allow for heavy loading, alongside isolation movements like leg extensions and hamstring curls, which benefit from higher reps.
Training to Failure
While training to failure is not always necessary, it can be an effective strategy for high-rep sets to maximise fibre recruitment. Low-rep sets should prioritise form and avoid failure to minimise injury risk (Schoenfeld, 2010).
Individual Considerations
- Beginners: High-rep training is recommended to build foundational endurance and motor control.
- Advanced Lifters: Low-rep training is essential for pushing strength limits and maximising type II fibre engagement.
- Injury History: High-rep, lower-load training may be safer for individuals with joint or connective tissue concerns.
Conclusion: Finding the Balance
Both high-rep and low-rep training have unique benefits for leg muscle growth. The most effective approach combines the strengths of each, focusing on volume, mechanical tension, and metabolic stress. Tailoring your training programme to include diverse rep ranges, based on your goals and experience level, will ensure optimal results.
Key Takeaways Table
| Key Takeaway | High Reps | Low Reps |
|---|---|---|
| Primary Focus | Muscular endurance, metabolic stress | Maximal strength, mechanical tension |
| Best for Beginners | Suitable due to lighter loads | Challenging, requires good form |
| Volume vs Intensity | Higher volume, lower intensity | Higher intensity, lower volume |
| Type II Fibre Engagement | Moderate, increases with failure | High, recruits high-threshold units |
| Optimal Strategy | Combine both for maximal results | Combine both for maximal results |
References
Dankel, S.J., Counts, B.R., Barnett, B.E., Buckner, S.L., Mattocks, K.T., Jessee, M.B. and Loenneke, J.P., 2017. Muscle adaptations following 21 consecutive days of strength test familiarization compared with traditional training. Physiology & Behavior, 171, pp.100-105.
Henneman, E., Somjen, G. and Carpenter, D.O., 1965. Functional significance of cell size in spinal motoneurons. Journal of Neurophysiology, 28(3), pp.560-580.
Morton, R.W., Oikawa, S.Y., Wavell, C.G., Mazara, N., McGlory, C., Quadrilatero, J., Baechler, B.L. and Phillips, S.M., 2016. Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of Applied Physiology, 121(1), pp.129-138.
Ralston, G.W., Kilgore, L., Wyatt, F.B. and Baker, J.S., 2017. The effect of weekly set volume on strength gain: A meta-analysis. Sports Medicine, 47(12), pp.2585-2601.
Schoenfeld, B.J., 2010. The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research, 24(10), pp.2857-2872.
Schoenfeld, B.J., Contreras, B., Vigotsky, A.D., Peterson, M. and Ogborn, D., 2016. Strength and hypertrophy adaptations between low- vs high-load resistance training: A systematic review and meta-analysis. Journal of Strength and Conditioning Research, 30(12), pp.3508-3523.
Schoenfeld, B.J., Ogborn, D. and Krieger, J.W., 2017. Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. Journal of Sports Sciences, 35(11), pp.1073-1082.
Wackerhage, H., Schoenfeld, B.J., Hamilton, D.L., Lehti, M. and Hulmi, J.J., 2019. Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise. Journal of Applied Physiology, 126(1), pp.30-43.
