When it comes to building muscular arms, the debate between high reps and low reps is a longstanding one. Some argue that high reps with lighter weights are best for muscle endurance and hypertrophy, while others claim that low reps with heavier weights maximise strength and size.
But which method is truly the best for arm growth? This article breaks down the science behind both approaches, analysing their impact on hypertrophy, strength, and muscle fibre recruitment.
Understanding Muscle Growth Mechanisms
Muscle hypertrophy primarily occurs through two pathways: myofibrillar and sarcoplasmic hypertrophy. Myofibrillar hypertrophy involves the growth of contractile proteins in muscle fibres, leading to increased strength. Sarcoplasmic hypertrophy, on the other hand, refers to an increase in muscle glycogen and fluid retention, contributing to muscle size (Schoenfeld, 2010). Different rep ranges target these pathways differently.
The Science Behind Low Reps
Low reps (typically 1-5 per set) involve lifting heavy weights at around 85-100% of one’s one-rep max (1RM). This range primarily stimulates myofibrillar hypertrophy and neural adaptations, increasing strength and power output (Mangine et al., 2015).
Research shows that training with heavier weights leads to greater activation of type II muscle fibres, which have the highest potential for growth (Campos et al., 2002).
Strength Benefits
Low-rep training significantly increases neuromuscular efficiency, improving motor unit recruitment and firing rates. A study by Mangine et al. (2015) found that lifters training with heavy weights and low reps experienced superior increases in maximal strength compared to those using moderate rep ranges.
Hypertrophy Effects
While low-rep training maximises strength gains, its hypertrophic benefits are somewhat limited compared to moderate-to-high rep training. A study by Schoenfeld et al. (2014) found that although low-rep training produced muscle growth, it was not significantly greater than hypertrophy achieved through moderate rep ranges.
The Science Behind High Reps
High-rep training (typically 12-20+ reps per set) involves lifting lighter weights at around 50-70% of 1RM. This rep range primarily stimulates sarcoplasmic hypertrophy, leading to increased muscle volume and endurance (Schoenfeld, 2010).
Muscle Endurance Benefits
A study by Mitchell et al. (2012) demonstrated that high-rep training increases mitochondrial density and capillary networks in muscles, enhancing endurance and fatigue resistance. This is particularly beneficial for athletes who require prolonged muscle performance.
Hypertrophy Effects
Contrary to popular belief, high-rep training can still lead to significant muscle hypertrophy when taken to failure. A study by Morton et al. (2016) found that subjects performing high-rep sets to failure achieved similar muscle growth to those lifting heavier loads with lower reps. This suggests that training intensity, rather than rep count alone, is crucial for hypertrophy.
Comparing High Reps and Low Reps for Arm Growth
Muscle Activation
Low reps with heavy loads recruit more type II fibres, which have greater potential for growth (Campos et al., 2002). High reps with lighter loads, however, recruit a mix of type I and type II fibres, leading to more balanced development (Schoenfeld et al., 2014).
Metabolic Stress and Hormonal Response
High-rep training induces greater metabolic stress, which plays a key role in hypertrophy. Metabolic stress leads to increased production of growth factors such as IGF-1 and human growth hormone (HGH), contributing to muscle size (Schoenfeld, 2013). Low-rep training, while effective for strength, does not produce the same metabolic stress levels.
Recovery and Fatigue
Low-rep training imposes high mechanical stress on muscles and joints, requiring longer recovery periods (Mangine et al., 2015). High-rep training, while causing more metabolic fatigue, allows for faster recovery due to lower mechanical tension per rep.
What’s the Best Approach for Bigger Arms?
Periodisation
To maximise arm hypertrophy, a periodised approach that includes both high and low reps is optimal. A study by Schoenfeld et al. (2016) found that combining different rep ranges led to superior muscle growth compared to sticking with a single rep scheme.
Training to Failure
Regardless of rep range, training to failure is crucial for maximising hypertrophy. A study by Morton et al. (2016) concluded that training to failure, whether with high or low reps, resulted in similar muscle growth outcomes.
Exercise Selection
For comprehensive arm development, include both compound movements (e.g., chin-ups, dips) and isolation exercises (e.g., bicep curls, tricep extensions). Compound movements benefit more from low-rep, heavy training, while isolation exercises can be effectively performed with higher reps (Schoenfeld, 2010).
Conclusion
Both high-rep and low-rep training have their advantages when it comes to building muscular arms. Low-rep training is superior for strength and type II fibre activation, while high-rep training enhances metabolic stress and endurance. The best strategy is a combination of both approaches, periodising rep ranges and ensuring training to failure for maximum hypertrophy.
Key Takeaways
Bibliography
Campos, G. E. R., et al. (2002) ‘Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones’, Journal of Applied Physiology, 88(1), pp. 50-60.
Mangine, G. T., et al. (2015) ‘Resistance training load does not determine training-mediated hypertrophic gains in young men’, Journal of Strength and Conditioning Research, 29(10), pp. 2953-2964.
Mitchell, C. J., et al. (2012) ‘Resistance exercise load does not determine training-mediated hypertrophic gains in young men’, Journal of Applied Physiology, 113(1), pp. 71-77.
Morton, R. W., et al. (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.
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., et al. (2013) ‘Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training’, Sports Medicine, 43(3), pp. 179-194.
Schoenfeld, B. J., et al. (2014) ‘Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men’, Journal of Strength and Conditioning Research, 28(10), pp. 2909-2918.
Schoenfeld, B. J., et al. (2016) ‘Effects of different resistance training frequencies on muscle adaptations in well-trained men’, Journal of Strength and Conditioning Research, 30(7), pp. 1925-1932.
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