Acute cellular and molecular responses and chronic adaptations to low-load blood flow restriction and high-load resistance exercise in trained individuals

Abstract

Blood flow restriction (BFR) with low-load resistance exercise (RE) is often used as a surrogate to traditional high-load RE to stimulate muscular adaptations, such as hypertrophy and strength. However, it is not clear whether such adaptations are achieved through similar cellular and molecular processes. We compared changes in muscle function, morphology and signaling pathways between these differing training protocols. Twenty-one males and females (mean ± SD: 24.3 ± 3.1 years) experienced with resistance training (4.9 ± 2.6 years) performed nine weeks of resistance training (three times per week) with either high-loads (75-80% 1RM; HL-RT), or low-loads with BFR (30-40% 1RM; LL-BFR). Before and after the training intervention, resting muscle biopsies were collected, and quadricep cross-sectional area (CSA), muscular strength and power were measured. Approximately 5 days following the intervention, the same individuals performed an additional 'acute' exercise session under the same conditions, and serial muscle biopsies were collected to assess hypertrophic- and ribosomal-based signaling stimuli. Quadricep CSA increased with both LL-BFR (7.4±4.3%) and HL-RT (4.6±2.9%), with no significant differences between training groups (p=0.37). Muscular strength also increased in both training groups, but with superior gains in squat 1RM occurring with HL-RT (p<0.01). Acute phosphorylation of several key proteins involved in hypertrophy signaling pathways, and expression of ribosomal RNA transcription factors occurred to a similar degree with LL-BFR and HL-RT (all p>0.05 for between-group comparisons). Together, these findings validate low-load resistance training with continuous BFR as an effective alternative to traditional high-load resistance training for increasing muscle hypertrophy in trained individuals.

Blood Flow Restriction Training

“…Davids et al, compared changes in muscle function, morphology and signaling pathways in twenty-one subjects who performed LIBFR or over the course of 9-weeks. 5 In this study it was found that muscle strength was superior in the HIRT group as expected given the specificity of training. However, acute phosphorylation of key proteins involved in hypertrophic pathways as well as expression of ribosomal RNA transcription factors were relatively comparable between the groups, suggesting the mechanisms for hypertrophy may be stimulated by LIRT when augmented with BFR.…”

“…A body of evidence suggests that low intensity resistance training (LIRT) with BFR (LIBFR) has the ability to produce hypertrophy based outcomes that exceed LIRT without BFR, and are similar to moderate to high intensity resistance training (MHIRT). [5][6][7] Explanations for these outcomes likely reside in the molecular and cellular benefits of applying a BFR tourniquet during training, which by way of a hypoxic effect and the accumulation of metabolites and cell swelling mimics a high intensity environment. While MHIRT possesses a specificity to sports or activities that require greater muscle activation that lower intensity training does not, it is clear that adding LIBFR is a desirable option for those individuals with a low exercise tolerance such as patient populations and those undergoing surgical and orthobiologic procedures.…”

“…The benefits of LIBFR range from acute hormonal responses and acute phosphorylation of proteins involved in hypertrophy signaling pathways (e.g., mammalian target of rapamycin pathway [mTOR]) to the expression of ribosomal RNA transcription factors, increases in biomarkers associated with satellite cell activity, and mRNA expression of genes related to skeletal muscle mass regulation (e.g., MuRF1). 5,6,[8][9][10][11][12][13][14][15] Moreover decreased bone resorption markers, increased interleukin-6 (which may assist with skeletal muscle remodeling) and vascular endothelial growth factor (VEGF), and increased blood lactate occur from LIBFR. 11,13,15,16 A majority of the evidence for acute hormonal secretions following LIBFR is related to growth hormone secretions.…”

Acute hypoxia attenuates resistance exercise‐induced ribosome signaling but does not impact satellite cell pool expansion in human skeletal muscle

“…Two micrograms of isolated RNA were reverse transcribed using iScript cDNA synthesis kit (Bio-Rad Laboratories) to produce 20 μL of complementary DNA (cDNA) for gene expression analysis. After performing standard curves from pooled cDNA, as recently described, 32,33 the cDNA was diluted 1:5 for most gene targets, but for 45 S pre-rRNA, c-MYC, POL1RA and TAF-1A the cDNA was diluted 1:25.…”

Effects of blood flow restriction training on anthropometric and blood lipids in overweight/obese adults: Meta-analysis

“…As well, blood flow restriction combined with endurance training has also been shown to improve cardiopulmonary health ( Conceição and Ugrinowitsch, 2019 ). Furthermore, BFRT can effectively improve muscle mass and strength in different populations ( Davids et al, 2021 ; Korkmaz et al, 2022 ), improve muscle fitness ( Hill et al, 2021 ), increase aerobic capacity ( Billaut et al, 2022 ), promote knee rehabilitation ( Centner et al, 2019 ), stimulate acute bone formation markers and hormonal responses ( Bemben et al, 2022 ), and improve athletic performance thereby maintaining overall good health ( Wortman et al, 2021 ). However, in the field of BFRT intervention for overweight/obesity, studies on anthropometric indicators and blood lipids have shown different results ( Da Silva et al, 2020 ; Kim and LeeDongminWon, 2021 ; Mohammadiyan et al, 2021 ; Yong et al, 2021 ).…”