Effects of combining forearm postexercise muscle ischemia with inspiratory loading on cardiovascular and muscle oxygenation responses.

PURPOSE: To investigate the effects of adding forearm postexercise muscle ischemia (PEMI) to inspiratory loading (IL) on pressor responses and muscle oxygenation. METHODS: Fourteen healthy adults performed three randomized trials: inspiratory loading (IL; 5 min at 70% maximal inspiratory pressure [MIP] followed by 3 min at 65% MIP), isometric handgrip exercise with post-exercise muscle ischemia (HG; 1 min of handgrip followed by 3 min of PEMI), and combined (ILHG) trials. Mean arterial pressure (MAP) was measured using a sphygmomanometer. Tissue oxygen saturation (StO₂) was measured using near-infrared spectroscopy in the intercostal muscles (IC) and vastus lateralis (VL). RESULTS: The MAP increased during IL in the IL trial (7.2 ± 7.7 mmHg vs. the control period, P < 0.05) and was higher in the ILHG trial than in IL alone (14.1 ± 7.8 mmHg); however, it did not differ from that in the HG trial (+ 12.7 ± 9.4 mmHg). The IC StO₂ decreased during IL in the IL trial (− 4.3 ± 7.6%; P < 0.05), without differing between the IL and ILHG trials. The VL StO₂ decreased during 70% MIP IL in the IL trial (− 3.2 ± 4.1%, P < 0.05), returned toward control levels during subsequent 65% MIP IL, and remained reduced in the ILHG trial (− 4.0 ± 6.4%, P < 0.05). CONCLUSION: Superimposing a limb muscle metaboreflex onto IL augmented the pressor response compared with IL alone; however, it did not further increase arterial pressure compared with PEMI alone. IL induced deoxygenation of the respiratory muscles, which was not exacerbated by additional metaboreflex activation, whereas deoxygenation in inactive limb muscles persisted under combined conditions.