Gastrocnemius medialis neuromechanics during cycling at various exercise intensities.

The aim of this study was to examine triceps surae neuromechanical function during cycling at a range of exercise intensities in endurance populations with different loading regimes, and to quantify differences in morphological properties. Kinematic and neuromuscular data were collected from 29 participants (10 cyclists, nine triathletes, and 10 controls) during cycling at four intensities (150, 200, 250, 300 W). Resting muscle and tendon morphology was assessed with ultrasound. During cycling, there were no differences between groups, despite triathletes possessing thicker Achilles' tendons. At higher intensities, ankle dorsiflexion increased (p < 0.001), leading to higher gastrocnemius medialis muscle-tendon unit range (p < 0.001), but no change in fascicle range or shortening velocity (p ≥ 0.919). Therefore, although there is evidence of some stretch-shortening cycle-like mechanism in the triceps surae during cycling, this does not happen at the muscle level, suggesting that energy storage and return could occur predominantly in the non-contractile series-elastic elements. Despite this, there were no differences detected between trained and untrained individuals in gastrocnemius medialis neuromechanical behavior at the exercise intensities tested, even though triathletes possessed a higher Achilles' tendon thickness.