September 2026; Vol. 15, No. 2: Pages 26-30
Measurement posture influences acute changes in quadriceps muscle thickness following resistance exercise
James R. Russo, Selena L. Gonzalez, Akshita Shah, Caitlin M. Foley, Samuel L. Buckner
Abstract
Objectives: To compare acute exercise-induced changes in anterior and lateral quadriceps muscle thickness (MT) measured in standing and supine positions. Design: Repeated-measures experimental study. Methods: Fifty healthy adults (18–35 years) performed four sets of unilateral knee extensions to task failure at 70% of one-repetition maximum (1RM). B-mode ultrasound was used to measure anterior and lateral quadriceps MT before and immediately after exercise in standing and supine positions. Measurements were obtained from both the exercised and contralateral control limbs. Results: Anterior thigh MT increased by 0.95 cm in the supine position and 0.68 cm in the standing position following exercise (both p < 0.001), with the increase being greater in the supine position (mean difference = 0.26 cm, p < 0.001). Lateral thigh MT increased by 0.32 cm in the supine position and 0.48 cm in the standing position (both p < 0.001), with the increase being greater in the standing position (mean difference = 0.15 cm, p < 0.001). No significant time effects were observed in the control limb for either site (both p > 0.05). Conclusions: Measurement posture influenced both baseline quadriceps MT and the magnitude of acute exercise-induced changes. Anterior thigh MT increased more in the supine position, whereas lateral thigh MT increased more in the standing position. These findings highlight the importance of standardizing measurement posture when interpreting ultrasound-derived changes in quadriceps MT.
Received July 22, 2026; accepted September 2, 2026