“Some people notice that not all endurance exercise affects their legs the same. Cycling makes their pants fit tighter and running doesn’t, even if they work out just as hard for both. So, does cycling really make your legs bigger?
A recent study in the Journal of Strength and Conditioning Research gives us some clues as to where the answer may lie. The study examined “concurrent training”, which is when endurance training and strength training are done together. It turns out that when running is added to strength training, muscles show decreases in growth and strength. In contrast, when cycling is added, muscle growth continues to occur as it would with strength training alone. One theory as to why this might happen is that cycling requires mostly “concentric” contractions (the muscle shorten as they contract) while running requires a greater percentage of “eccentric” contractions (the muscles lengthen as they contract). Eccentric contractions cause more muscle damage than concentric ones and might make it more difficult for muscle growth to occur.
So the observation that cycling makes legs stronger and bigger than running is probably a good one! But before you avoid the bike like the plague out of a fear of developing “thunder thighs”, remember that stronger leg muscles prevent injuries. Cycling is also a low impact activity that is gentle on your leg joints.”- Dr. Lomas
Dr. Guillem Gonzalez-Lomas is an Assistant Professor of Orthopaedic Surgery at NYU – Hospital for Joint Diseases in New York. He specializes in arthroscopic surgery, ligament and tendon reconstructions and sports related injuries.