Key result
Blood flow restriction walking stimulates ~3-fold greater renin release vs normal walking without altering fluid retention.
Why the study?
The study was conducted to characterize the efficacy of altered restriction pressures and the consequences of optimized blood flow restriction on cardiovascular and fluid-regulating responses in humans.
Does blood flow restriction exercise alter central hemodynamics and fluid regulating hormones in humans?
Does blood flow restriction exercise alter central hemodynamics and fluid regulating hormones in humans?
Blood flow restriction exercise at 100% lowest arterial occlusion pressure maximizes cardiovascular effects and stimulates fluid-regulating hormone release without altering 24-hour fluid retention.
BFR walking at 100% LOP heightens acute hemodynamic stress; extends mechanistic evidence on hormone release without fluid retention changes.
PURPOSE: The purpose of this study is to characterize both the efficacy of altered restriction pressures and consequences of optimized blood flow restriction (BFR) for altering the cardiovascular and fluid regulating response in humans. METHODS: This work comprised a series of related trials. Phase 1: during semi-recumbent cycling (5 min, 60 W) with BFR at 0%, 50%, 75%, 100%, and 125% of participants' lowest arterial occlusion pressure (LOP) echocardiographic images were collected alongside continuous heart rate (HR) and blood pressure (BP). In phase 2, 24 h fluid balance (intake-output) and fluid-regulating hormone responses were measured after a practical BFR exercise session (treadmill walking: 5·3 min, 1 min rest, 5 km·h -1 , 5% incline, 100% LOP). Phase 3 examined the magnitude and effect of blood volume distribution following BFR treadmill walking using a modified CO-rebreathe technique. RESULTS: Cardiac ejection fraction remained stable irrespective of cuff pressure and despite a reduction in end-diastolic volume (Δ of 11 ± 9 mL, P = 0.02). HR and BP were highest at 100% LOP (ΔHR = 18 ± 19 bpm, ΔSBP = 51 ± 30 mm Hg, ΔDBP = 33 ± 15 mm Hg, ΔRate Pressure Product = 76 ± 32 bpm·mm Hg·100 -1 ). BFR treadmill walking stimulated a greater release of fluid-regulating hormones than normal walking (Δrenin = BFR: 25.3 ± 24.2 vs CON: 9.1 ± 11.8 ng·L -1 ; Δcopeptin = BFR: 50.1 ± 97.9 vs. CON: 0.43 ± 0.8 pmol·L -1 ), but no difference in fluid retention was observed ( P = 0.2). Approximately 27% of total blood volume was confined to the legs during BFR, but the relative volume trapped in the legs was not related to fluid-regulating hormone release (renin r = -0.04, P = 0.9; copeptin r = 0.27, P = 0.3). CONCLUSIONS: BFR exercise elicits the largest cardiovascular effect using 100% LOP, with evidence of appreciable fluid regulating hormonal response during a typical BFR exercise session. The relative volume of blood sequestered in the limb does not appear to drive this response.
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Thompson et al. (2023) studied this question. Blood flow restriction (BFR) exercise vs. Normal exercise (0% LOP or normal walking) was evaluated on Central hemodynamics and fluid-regulating hormone responses. Blood flow restriction treadmill walking stimulated greater release of fluid-regulating hormones like renin (Δ 25.3 vs 9.1 ng/L) and copeptin than normal walking, without altering fluid retention.
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