Effects of low load exercise with and without blood‐flow restriction on microvascular oxygenation, muscle excitability and perceived pain

Abstract

This paper aimed to examine the acute effect of low-load (LL) exercise with blood-flow restriction (LL-BFR) on microvascular oxygenation and muscle excitability of the vastus medialis (VM) and vastus lateralis (VL) muscles during a single bout of unilateral knee extension exercise performed to task failure. Seventeen healthy recreationally resistance-trained males were enrolled in a within-group randomized cross-over study design.Participants performed one set of unilateral knee extensions at 20% of one-repetition maximum (1RM) to task failure, using a LL-BFR or LL free-flow (LL-FF) protocol in a randomized order on separate days. Changes in oxygenation and muscle excitability in VL and VM were assessed using near-infrared spectroscopy (NIRS) and surface electromyography (sEMG), respectively. Pain measures were collected using the visual analog scale (VAS) before and following set completion. Within-and between-protocol comparisons were performed at multiple time points of set completion for each muscle. During LL-BFR, participants performed 43% fewer repetitions and reported feeling more pain compared to LL-FF (p<0.05). Normalized to time to task failure, LL-BFR and LL-FF generally demonstrated similar progression in microvascular oxygenation and muscle excitability during exercise to task failure. The present results demonstrate that LL-BFR accelerates time to task failure, compared with LL-FF, resulting in a lower dose of mechanical work to elicit similar levels of oxygenation, blood-pooling, and muscle excitability. LL-BFR may be preferable to LL-FF in clinical settings where high workloads are contraindicated, although increased pain experienced during BFR may limit its application.

Distinct adaptations of muscle endurance but not strength or hypertrophy to low‐load resistance training with and without blood flow restriction

“…Finally, and most importantly, further research is needed to determine whether our findings can be applied to multi-joint and/or lower-limb exercises. Nevertheless, recent studies using singleleg squat (Petrick et al, 2019) and knee extension (Kolind et al, 2023) have shown that the application of BFR caused a reduction in the total number of repetitions, the magnitude of which was similar to that in the present study. We thus believe that the acute and chronic effects of BFR on muscle endurance performance and adaptations are consistent across types of exercises.…”

“…The sample size in experiment 1 was determined by the following procedure. Initially, we estimated an effect size (Cohen's d ) in Student's paired t ‐test to be 1.5 from previous studies investigating the acute effect of BFR on the maximum number of repetitions (Farup et al., 2015; Kolind et al., 2023; Wernbom et al., 2009). Using power analysis software (G*Power v.3.1.9.6, University of Düsseldorf, Germany), the minimal sample size required for an 80% statistical power and an α error of 5% (two tailed) resulted in seven participants.…”

“…One feature of exercise with BFR potentially related to muscle and performance adaptations is the reduction in time to task failure or the number of repetitions in comparison to exercise without BFR (Farup et al., 2015; Kolind et al., 2023; Wernbom et al., 2009), resulting in time‐efficient improvements in muscle mass and strength. However, the exercise volume (load × number of repetitions) is considered to play a major role in improving muscle endurance (Campos et al., 2002; Stone & Coulter, 1994).…”

Acute Effect of Resistance Training With Blood Flow Restriction on Perceptual Responses: A Systematic Review and Meta-Analysis

“…This is an interesting finding considering how RPE is elevated with increasing proximity to failure and that BFR exercise accelerates volitional fatigue in an exercise task by as much as 43%. 25 The heterogeneity of the included studies within our analyses likely produced our findings because RPE is similar (eg, near maximal) during failure training regardless of the application of BFR, 32 necessitating additional subgrouping according to repetition scheme (eg, fixed versus failure).…”

Low-Level Laser Therapy Facilitates Postcontraction Recovery with Ischemic Preconditioning

“…Because of low microvascular oxygenation, early fatigue development in local muscle is a potential barrier to muscle training with BFR. Risks associated with excessive metabolic stress prevent increases in training volume (33)(34)(35) and/or delay-onset muscle soreness (36) under the hypoxic condition. The decline in MVC force after strength training with ischemic preconditioning is of peripheral and/or central origins, such as the accumulation of lactate (37) and decline in corticospinal excitability (10).…”