Introduction: The mechanisms by which skeletal muscles adapt to restricted blood flow during activity using an inflatable cuff (ischemic exercise) have not yet been thoroughly investigated. However, it is assumed that the key stimulus is localized skeletal muscle hypoxia. Purpose: The aim of this study was to evaluate the effects of ischemic aerobic exercise on oxygen kinetics and blood perfusion in the quadriceps muscle during cycling and during a 10-minute early post-exercise recovery phase. Methods: Healthy participants (n = 21), aged 18–35 years, completed three trials on a stationary bike. First, maximal oxygen consumption (Pmax) was determined using a three-stage test. Participants then performed two separate two-stage tests (at 40% and 60% of Pmax), once with blood flow restriction applied to the quadriceps muscle (ischemic exercise) and once without blood flow restriction (control exercise). During cycling and recovery, changes in total hemoglobin concentration ([tHb]), the difference between oxygenated and deoxygenated hemoglobin ([Hbdiff]), and the tissue saturation index (TSI) were continuously measured in the vastus lateralis and vastus medialis muscles using near-infrared spectroscopy. Results: Analysis of the interaction between time and intervention using ANOVA showed that [tHb] in both muscles increased significantly more (p < 0.05) during ischemic exercise compared to control exercise. During recovery following ischemic exercise, a trend toward elevated [tHb] was also observed; however, the difference compared with control exercise was significant only in the first few minutes. TSI and [Hbdiff] in the vastus lateralis muscle decreased significantly more (p < 0.05) during ischemic exercise than during control exercise, whereas no significant interaction was found in the vastus medialis muscle. Lower [Hbdiff] values in both muscles were also observed during the first 2–6 minutes of recovery following ischemic exercise (p < 0.05) compared to control exercise, after which the differences disappeared. In contrast, no significant interaction was observed for TSI changes in the vastus medialis muscle during or after exercise. Discussion and Conclusion: The findings indicate that the mechanical pressure of the inflatable cuff reduces blood flow and induces tissue hypoxia in the vastus lateralis muscle during cycling. This likely leads to the earlier activation of anaerobic metabolism and, consequently, a greater oxygen deficit during recovery. A similar but less pronounced effect was observed in the vastus medialis muscle. Further studies with a larger sample size are needed.
|
