Exercise speed and workload effects on muscle hypoxia in vastus lateralis muscle during squatting exercises

Abstract

Background: The study aimed to examine the effects of varying exercise speed and joint motion range (opting for either full knee extension or sustained knee flexion) on the intramuscular hypoxic environment, a key factor in muscle hypertrophy, during squat exercises. Methods: The participants were 17 healthy male and female students from Kibi International University, without back or knee pain at the time of evaluation. Two squat variations were performed: squats with full knee extension (Locked group; L group) and squats without full knee extension (non-locked group; NL group). The exercises were conducted in the following sequence with intervals: 12 s of non-locking (NL12), 12 s of locking (L12), 8 s of non-locking (NL8), 8 s of locking (L8), 4 s of non-locking (NL4), and 4 s of locking (L4). Tissue Oxygen Saturation (StO2) in the right vastus lateralis muscle, under blood flow restriction during squat exercises, was measured using near-infrared spectroscopy. Results: The minimum StO2 for NL12 was significantly lower than the resting StO2 values. Similarly, the minimum StO2 values for L12 and L8 were also significantly lower than the resting StO2 values. The minimum StO2 value for 8 s was significantly lower than at rest only in group L. Conclusion: When performing squat exercises, it is beneficial to reduce the exercise speed and increase the knee joint’s range of motion. This adjustment enhances the work of the quadriceps muscles, thereby creating an intramuscular hypoxic environment and promoting muscle hypertrophy.