Training with blood flow restriction increases femoral artery diameter and thigh oxygen delivery during knee‐extensor exercise in recreationally trained men

Abstract

Key points Endurance‐type training with blood flow restriction (BFR) increases maximum oxygen uptake (V̇O2max) and exercise endurance of humans. However, the physiological mechanisms behind this phenomenon remain uncertain. In the present study, we show that BFR‐interval training reduces the peripheral resistance to oxygen transport during dynamic, submaximal exercise in recreationally‐trained men, mainly by increasing convective oxygen delivery to contracting muscles. Accordingly, BFR‐training increased oxygen uptake by, and concomitantly reduced net lactate release from, the contracting muscles during relative‐intensity‐matched exercise, at the same time as invoking a similar increase in diffusional oxygen conductance compared to the training control. Only BFR‐training increased resting femoral artery diameter, whereas increases in oxygen transport and uptake were dissociated from changes in the skeletal muscle content of mitochondrial electron‐transport proteins. Thus, physically trained men benefit from BFR‐interval training by increasing leg convective oxygen transport and reducing lactate release, thereby improving the potential for increasing the percentage of V̇O2max that can be sustained throughout exercise. Abstract In the present study, we investigated the effect of training with blood flow restriction (BFR) on thigh oxygen transport and uptake, and lactate release, during exercise. Ten recreationally‐trained men (50 ± 5 mL kg−1 min−1) completed 6 weeks of interval cycling with one leg under BFR (BFR‐leg; pressure: ∼180 mmHg) and the other leg without BFR (CON‐leg). Before and after the training intervention (INT), thigh oxygen delivery, extraction, uptake, diffusion capacity and lactate release were determined during knee‐extensor exercise at 25% incremental peak power output (iPPO) (Ex1), followed by exercise to exhaustion at 90% pre‐training iPPO (Ex2), by measurement of femoral‐artery blood flow and femoral‐arterial and ‐venous blood sampling. A muscle biopsy was obtained from legs before and after INT to determine mitochondrial electron‐transport protein content. Femoral‐artery diameter was also measured. In the BFR‐leg, after INT, oxygen delivery and uptake were higher, and net lactate release was lower, during Ex1 (vs. CON‐leg; P < 0.05), with an 11% larger increase in workload (vs. CON‐leg; P < 0.05). During Ex2, after INT, oxygen delivery was higher, and oxygen extraction was lower, in the BFR‐leg compared to the CON‐leg (P < 0.05), resulting in an unaltered oxygen uptake (vs. CON‐leg; P > 0.05). In the CON‐leg, at both intensities, oxygen delivery, extraction, uptake and lactate release remained unchanged (P > 0.05). Resting femoral artery diameter increased with INT only in the BFR‐leg (∼4%; P < 0.05). Oxygen diffusion capacity was similarly raised in legs (P < 0.05). Mitochondrial protein content remained unchanged in legs (P > 0.05). Thus, BFR‐interval training enhances oxygen utilization by, and lowers lactate release from, submaximally‐exercising muscles of recreationally‐trained men m...

Blood flow restriction training: You can occlude your veins, but not your oxygen transport

“…Post training, a higher O 2 convective reserve greatly reduced the total net lactate release in the BFR-leg compared to the CON-leg at submaximal intensity. Enhanced O 2 transport and consequently delayed onset of lactate accumulation improved post-training PO in the BFR-leg (11%) (Christiansen et al 2020). This result demonstrates an important impact of BFR on improvement of endurance performance, similar to those reported in previous studies (Sundberg, 1994;Bennett & Slattery, 2019).…”

“…Early studies have demonstrated that aerobic training with a blunted O 2 supply improved aerobic performance and invoked mitochondrial and vascular adaptations (Sundberg, 1994), thus allowing efficient convective and diffusional transport of O 2 to the exercising muscles (Wagner, 1996). In the present study, BFR-training led to a greater increase in thigh O 2 transport and a difference between O 2 delivery and uptake in BFR-leg compared to CON-leg at both exercise intensities (Christiansen et al 2020). By contrast, when performing high intensity knee extensor exercise, O 2 uptake remained unchanged, whereas O 2 delivery increased.…”

“…Surprisingly, the content of mitochondrial electron transport proteins remained unaltered after BFR-training, despite the aforementioned oxidative adaptations. It was suggested that the small sample size and high variability in the western blotting methods may have markedly influenced the outcomes with respect to assessing the mitochondrial function (Christiansen et al 2020).…”

“…However, the effects of other underlying factors (e.g. sympathetic and vasodilatation activity) can not be excluded (Poole, Behnke, & Musch, 2020), despite not being assessed within the scope of the study (Christiansen et al 2020). For example, previous studies have demonstrated that an increase in plasma nitrate levels may contribute to a higher bioavailability of nitric oxide post aerobic BFR training (Sundberg, 1994).…”

“…For example, previous studies have demonstrated that an increase in plasma nitrate levels may contribute to a higher bioavailability of nitric oxide post aerobic BFR training (Sundberg, 1994). This may therefore explain the superior effects of vasodilatation biomarkers over resting morphological changes in blood vessel diameter on increased blood flow to exercising muscles during submaximal BFR exercise (Christiansen et al 2020).…”