Purpose: Muscle power is a component of muscular fitness and is proportional to its volume. Reduced muscular fitness in children is linked to negative health outcomes. Associations between muscle volume (MV) and power have not been examined in young children and could reveal important insights into early neuromuscular development.
Method: Forty-four children (2-8 y) completed 3 tests of short-term muscular power: repeated anaerobic sprint test, vertical jump, and horizontal jump. MV was assessed using 3D ultrasound for 3 lower limb muscles (rectus femoris, medial gastrocnemius, and tibialis anterior) and summed for across legs. Associations between muscular power and summed MV were assessed using Pearson correlation (r). Sex-based differences in muscular power and MV were assessed using 1-way analysis of covariance.
Results: Moderate-strong associations (r = .57 - .87) were found between muscular power and summed MV. No differences were found between boys and girls for height, weight, MV, or muscular power.
Conclusions: Young children who have larger lower limb muscles perform better at tasks dependent on short-term muscular power, such as running and jumping, compared with children with smaller muscles. Sex-based differences in short-term muscular power do not exist in young children and reflect similar anthropometry, including lower limb MV.
Keywords: growth; jumping; muscular fitness; speed; ultrasound.