Muscle Damage Is Not What Builds Muscle

Opener

Soreness feels like proof. The first hard week back in the gym leaves you stiff, weaker on the lifts, and sure that something important must be happening. A 2016 study in The Journal of Physiology by Felipe Damas and colleagues tested that feeling directly. They measured muscle damage, muscle protein synthesis, and actual fibre growth in the same people across a training programme. The week with the most damage and the biggest protein-synthesis response produced no relationship to growth. Growth showed up later, after the damage response had settled down.

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1. What the study asked

Does the large rise in myofibrillar protein synthesis after early training sessions actually build muscle, or is that rise mostly spent repairing damage? Earlier work often treated a protein-synthesis spike as a stand-in for growth. This study checked whether the spike and the growth were the same event.

2. How the evidence was built

• Design. Ten healthy young men who had trained before but had been detrained for at least six months completed a supervised 10-week leg programme: leg press and leg extension, three sets of 9–12 reps to volitional fatigue, twice per week.
• Measurements at week 1, week 3, and week 10. After a training session at each of those points, the researchers measured integrated myofibrillar protein synthesis (deuterium-oxide tracer), muscle damage (electron-microscope Z-band streaming, plus soreness, strength loss, and creatine kinase), and hypertrophy (fibre cross-sectional area from biopsy).
• Why that matters. Damage, protein synthesis, and growth were tracked together in the same subjects across the same programme, instead of inferring growth from synthesis alone.