Combined effect of sprint interval training and post-exercise blood flow restriction on muscle deoxygenation responses during ramp incremental cycling.

Purpose: This study investigated the effect of sprint-interval training combined with post-exercise blood flow restriction (i.e., SIT + BFR) on pulmonary gas exchange and microvascular deoxygenation responses during ramp incremental (RI) cycling.

Methods: Nineteen healthy, untrained males (mean ± SD age: 24 ± 5 years; height: 178 ± 6 cm; body mass: 77.0 ± 10.7 kg) were assigned to receive 4 weeks of SIT or SIT + BFR. Before and after the intervention period, each participant completed a RI cycling test for determination of peak oxygen uptake ( $\dot{\text{V}}{\text{O}}_{\text{2peak}}$ ) and the gas exchange threshold (GET) with deoxygenated heme (Δdeoxy[heme]) and tissue oxygenation index (TOI) measured by near-infrared spectroscopy (NIRS) in vastus lateralis (VL) muscle.

Results: Relative $\dot{\text{V}}{\text{O}}_{\text{2peak}}$ increased by 7% following both interventions (P ≤ 0.03). SIT + BFR increased peak Δdeoxy[heme] when normalized relative to leg arterial occlusion (PRE: 57.3 ± 13.0 vs. POST: 62.0 ± 13.2%; P = 0.009) whereas there was no significant difference following SIT (PRE: 64.9 ± 14.3 vs. POST: 71.4 ± 11.7%; P = 0.17). Likewise, TOI nadir decreased at exhaustion following SIT + BFR (PRE: 56.9 ± 9.1 vs. POST: 51.4 ± 9.2%; P = 0.002) but not after SIT (PRE: 58.5 ± 7.1 vs. POST: 56.3 ± 8.2%; P = 0.29). The absolute cycling power at the GET increased following SIT + BFR (PRE: 108 ± 13 vs. POST: 125 ± 17 W, P = 0.001) but was not significantly different following SIT (PRE: 112 ± 7 VS. POST: 116 ± 11 W, P = 0.54).

Conclusion: The addition of post-exercise BFR to SIT alters the mechanism underlying the enhancement in $\dot{\text{V}}{\text{O}}_{\text{2peak}}$ by increasing the peak rate of muscle fractional O₂ extraction in previously untrained males.