Acute physiological responses of blood flow restriction between high-intensity interval repetitions in trained cyclists

Abstract

Blood flow restriction (BFR) is increasingly being used to enhance aerobic performance in endurance athletes. This study examined physiological responses to BFR applied in recovery phases within a high-intensity interval training (HIIT) session in trained cyclists. Eleven competitive road cyclists (mean ± SD, age: 28 ± 7 years, body mass: 69 ± 6 kg, peak oxygen uptake: 65 ± 9 mL · kg^-1 · min^-1) completed two randomised crossover conditions: HIIT with (BFR) and without (CON) BFR applied during recovery phases. HIIT consisted of six 30-s cycling bouts at an intensity equivalent to 85% of maximal 30-s power (523 ± 93 W), interspersed with 4.5-min recovery. BFR (200 mmHg, 12 cm cuff width) was applied for 2-min in the early recovery phase between each interval. Pulmonary gas exchange (V̇O₂, V̇CO₂, and V̇E), tissue oxygen saturation index (TSI), heart rate (HR), and serum vascular endothelial growth factor concentration (VEGF) were measured. Compared to CON, BFR increased V̇CO₂ and V̇E during work bouts (both p < 0.05, dz < 0.5), but there was no effect on V̇O₂, TSI, or HR (p > 0.05). In early recovery, BFR decreased TSI, V̇O₂, V̇CO₂, and V̇E (all p < 0.05, dz > 0.8) versus CON, with no change in HR (p > 0.05). In late recovery, when BFR was released, V̇O₂, V̇CO₂, V̇E, and HR increased, but TSI decreased versus CON (all p < 0.05, dz > 0.8). There was a greater increase in VEGF at 3-h post-exercise in BFR compared to CON (p < 0.05, dz > 0.8). Incorporating BFR into HIIT recovery phases altered physiological responses compared to exercise alone.

Keywords: cardiorespiratory; physiology; recovery; stress; training.

FIGURE 1

Mean 5‐s traces of physiological parameters for BFR and CON interventions. Phases are labelled in the first repetition, with consistent shading thereafter. Panels: (A) tissue saturation index (TSI); (B) oxygen uptake (V̇O₂); (C) carbon dioxide production (V̇CO₂); (D) minute ventilation (V̇E); and (E) heart rate (HR) for blood flow restriction (BFR) and control (CON) conditions.

FIGURE 2

Physiological responses during BFR and CON interventions. Phases are labelled in the first repetition, with consistent shading thereafter. Panels: (A) tissue saturation index (TSI); (B) oxygen uptake (V̇O₂); (C) carbon dioxide production (V̇CO₂); (D) minute ventilation (V̇E); and (E) heart rate (HR) for blood flow restriction (BFR) and control (CON) conditions. Values are presented as mean ± 95% confidence intervals. An asterisk (*) indicates a significant (p < 0.05) post‐hoc result between conditions.

FIGURE 3

Acute vascular endothelial growth factor responses for BFR and CON. (A) Serum vascular endothelial growth factor (VEGF) at baseline and 3‐h post‐exercise for blood flow restriction (BFR) and control (CON) conditions. (B) Change in VEGF (post‐baseline) for BFR and CON. Bars are means. Brackets with p‐values show between‐condition comparisons at each timepoint in A. The p‐value in B indicates the condition × time interaction.