Monitoring internal load is essential to understanding fatigue and training adaptation in athletes. This study aimed to evaluate the effect of different knee flexion angles during a 40-s isometric squat on muscle oxygen saturation (SmO2) responses. Seventeen physically active participants (9 males and 8 females: 28 ± 9 years old, 174 ± 12 cm, and 70.1 ± 16.6 kg) performed three randomized squats at 80°, 90°, and 100° knee angles. Muscle excitation (i.e., RMS) was measured using surface electromyography (EMG), and SmO2 was recorded with near-infrared spectroscopy technology. Results indicated that SmO2 differed only between the most extreme angles (80° vs. 100°), with significantly greater deoxygenation at 80°, emerging in the final 20% of the squat (p 2, though differences only emerge toward the end of the task. Thus, using a goniometer for posture control may be sufficient in field settings, offering a practical approach for load monitoring and fatigue assessment during isometric strength testing.
Portilla‐Dorado et al. (Sun,) studied this question.