Skeletal Muscle Mitochondrial Protein Synthesis and Respiration Increase With Low-Load Blood Flow Restricted as Well as High-Load Resistance Training

Abstract

Purpose: It is well established that high-load resistance exercise (HLRE) can stimulate myofibrillar accretion. Additionally, recent studies suggest that HLRE can also stimulate mitochondrial biogenesis and respiratory function. However, in several clinical situations, the use of resistance exercise with high loading may not constitute a viable approach. Low-load blood flow restricted resistance exercise (BFRRE) has emerged as a time-effective low-load alternative to stimulate myofibrillar accretion. It is unknown if BFRRE can also stimulate mitochondrial biogenesis and respiratory function. If so, BFRRE could provide a feasible strategy to stimulate muscle metabolic health.Methods: To study this, 34 healthy previously untrained individuals (24 ± 3 years) participated in BFRRE, HLRE, or non-exercise control intervention (CON) 3 times per week for 6 weeks. Skeletal muscle biopsies were collected; (1) before and after the 6-week intervention period to assess mitochondrial biogenesis and respiratory function and; (2) during recovery from single-bout exercise to assess myocellular signaling events involved in transcriptional regulation of mitochondrial biogenesis. During the 6-week intervention period, deuterium oxide (D2O) was continuously administered to the participants to label newly synthesized skeletal muscle mitochondrial proteins. Mitochondrial respiratory function was assessed in permeabilized muscle fibers with high-resolution respirometry. Mitochondrial content was assessed with a citrate synthase activity assay. Myocellular signaling was assessed with immunoblotting.Results: Mitochondrial protein synthesis rate was higher with BFRRE (1.19%/day) and HLRE (1.15%/day) compared to CON (0.92%/day) (P < 0.05) but similar between exercise groups. Mitochondrial respiratory function increased to similar degree with both exercise regimens and did not change with CON. For instance, coupled respiration supported by convergent electron flow from complex I and II increased 38% with BFRRE and 24% with HLRE (P < 0.01). Training did not alter citrate synthase activity compared to CON. BFRRE and HLRE elicited similar myocellular signaling responses.Conclusion: These results support recent findings that resistance exercise can stimulate mitochondrial biogenesis and respiratory function to support healthy skeletal muscle and whole-body metabolism. Intriquingly, BFRRE produces similar mitochondrial adaptations at a markedly lower load, which entail great clinical perspective for populations in whom exercise with high loading is untenable.

Unpacking the mitochondrial bioenergetics of blood flow restricted resistance exercise

“…An improvement to the study design would be to take a more immediate post‐exercise muscle biopsy in addition to the ones taken 2 h post‐exercise, similar to the protocol used by Groennebaek et al . (). That would then allow for the detection of any short‐term mitochondrial bioenergetic responses as well as those reported in the study.…”

“…() and Groennebaek et al . () also used three to four sets to volitional fatigue, while studies by Neto et al . () and Centner et al .…”

“…; Groennebaek et al . ; Petrick et al . ), and others using arbitrarily applied pressures including 20 mmHg below systolic blood pressure (Goldfarb et al .…”

“…However, Groennebaek et al . () recently demonstrated that both HLRT and BFR‐RT may also improve these mitochondrial functions. That BFR‐RT may also elicit these improvements is of particular importance for ageing and various chronic disease populations who are often contraindicated to high‐intensities of aerobic activity or the high mechanical stress associated with HLRT, as they stand to benefit most from the reduced physical demands of BFR‐RT.…”

“…Yet, despite the findings from Groennebaek et al . (), the role of mitochondrial bioenergetics in BFR‐RT adaptations is still poorly understood and evidence underpinning it is often contradictory.…”