Rethinking Muscle Growth: The Science Beyond 'No Pain, No Gain'
For decades, the mantra of bodybuilding has been 'no pain, no gain', with traditional advice pushing workouts to failure and celebrating soreness as a sign of effectiveness. However, emerging scientific evidence is challenging this long-held belief, revealing a more nuanced understanding of how muscles actually grow.
The Shift from Damage to Tension
The conventional 'tear and repair' model suggested that microtears in muscle fibres during exercise triggered repair processes, leading to bigger, stronger muscles. This philosophy justified extreme training methods and the pursuit of maximum muscle trauma. While this approach has worked for many lifters, particularly those using performance enhancers, current research points toward a different primary mechanism.
'The best evidence now suggests that the primary driver of muscle hypertrophy is mechanical tension,' explains Dr Anne Brady, a kinesiology professor specialising in muscle quality and body composition. 'Muscle damage certainly contributes, but it's not the main factor. Typically, it's more of a side-effect.'
How Mechanical Tension Works
When you lift sufficiently heavy weights or perform enough repetitions to approach failure, the resulting physical tension stretches the membrane surrounding muscle cells. Specialised sensors called mechanoreceptors detect this stretch and activate the mTOR pathway, a master regulator that determines whether the body should build new tissue. This pathway then initiates muscle protein synthesis, adding new protein to muscle fibres to make them thicker and stronger.
A third factor, metabolic stress, creates the familiar 'burn' during lifting. 'You can think of that as an amplifier to mechanical tension,' says Brady. 'It creates a favourable environment for muscle growth.' However, this burn alone doesn't guarantee growth – you might feel it while doing biceps curls with a pencil, but without sufficient tension, muscle development remains minimal.
Two Types of Hypertrophy
Understanding muscle growth requires recognising two distinct types of hypertrophy:
- Myofibrillar hypertrophy increases the number of myofibrils – the bundles that contract to lift weights – resulting in greater strength
- Sarcoplasmic hypertrophy expands the fluid volume inside muscles, creating larger size without additional strength
This explains why Olympic weightlifters can move enormous weights without significantly increasing bodyweight, and why gymnasts often demonstrate greater strength in specific movements than bodybuilders focused purely on aesthetics. While both types typically occur together, different training approaches can emphasise one over the other.
Practical Implications for Training
This new understanding has significant implications for how we approach strength training:
- Pain isn't a reliable indicator – muscles can grow with minimal soreness, while activities like downhill running can cause substantial damage without promoting growth
- Near-failure suffices – working to near failure across various repetition ranges proves effective without requiring maximum trauma
- Progressive overload remains key – gradually increasing workload through heavier weights, more repetitions, or reduced rest periods drives adaptation
'I coach women in midlife, and always tell them not to major in the minor,' advises Brady, emphasising the importance of focusing on fundamental principles rather than obsessing over trivial details.
A Balanced Approach to Strength
The most effective muscle growth appears to occur when combining both types of hypertrophy – using weights heavy enough to create substantial tension while performing sufficient repetitions to generate metabolic stress. This balanced approach allows for strength development and modest size increases, though dramatic muscle growth without pharmaceutical assistance remains challenging for most individuals.
This evolving scientific perspective encourages a more sustainable approach to strength training, moving beyond the pain-centric models of traditional bodybuilding toward methods grounded in physiological understanding rather than gym mythology.
