Abstract
PurposeNo current guidelines or recommendations exist informing the selection of restriction pressure during blood flow restriction exercise (BFRE). Moreover, the effects of specific relative restriction pressures on the acute muscle, metabolic and cardiopulmonary responses to BFRE are unclear. The purpose of this study was to characterize these acute responses at different levels of restriction pressure.MethodsParticipants (n = 10) completed rhythmic isometric knee extension exercise across five experimental trials in a balanced randomized order. Three were BFRE trials {B-40 [restriction pressure set to 40% LOP (total limb occlusion pressure)]; B-60 (60% LOP); and B-80 (80% LOP)} with a workload equivalent to 20% maximal voluntary force (MVC), one was non-BFRE at 20% MVC (LL) and one was non-BFRE at 80% MVC (HL). Measurements recorded were torque, muscle activity via electromyography (EMG), tissue oxygenation via near infrared spectroscopy, whole body oxygen consumption, blood lactate and heart rate.ResultsFor the LL and B-40 trials, most measures remained constant. However, for the B-60 and B-80 trials, significant fatigue was demonstrated by a reduction in MVC torque across the trial (p < 0.05). Blood lactate increased from baseline in HL, B-60, and B-80 (p < 0.05). Submaximal EMG was greater in B-60 and B-80 than LL, but lower compared with HL (p < 0.05). Tissue oxygenation decreased in HL, B-40, B-60, and B-80 (p < 0.05), which was lower in the B-80 trial compared to all other trials (p < 0.01). Whole body oxygen consumption was not different between the BFRE trials (p > 0.05).ConclusionWe demonstrate graded/progressive acute responses with increasing applied pressure during BFRE, from which we speculate that an effective minimum “threshold” around 60% LOP may be necessary for BFRE to be effective with training. While these data provide some insight on the possible mechanisms by which BFRE develops skeletal muscle size and strength when undertaken chronically across a training program, the outcomes of chronic training programs using different levels of applied restriction pressures remain to be tested. Overall, the present study recommends 60–80% LOP as a suitable “minimum” BFRE pressure.
Highlights
To increase skeletal muscle size and strength it is recommended to lift loads that exceed 65–70% one repetition maximum (1RM) (American College of Sports Medicine, 2009)
It so happens that few studies have attempted to examine the influence of different magnitudes of restriction pressure on acute responses to blood flow restriction exercise (BFRE) (Yasuda et al, 2008; Fatela et al, 2016), that may in turn influence the magnitude of any gains in skeletal muscle size and strength with chronic BFRE training
While the findings of the present study should not be directly extrapolated to common dynamic modes of blood flow restriction (BFR) exercise, given the graded response to BFR pressures and the nature of the decline in maximal voluntary contraction (MVC) torque, MVC EMG and tissue oxygenation during rest periods, we consider the outcomes of such modes would not be vastly different
Summary
To increase skeletal muscle size and strength it is recommended to lift loads that exceed 65–70% one repetition maximum (1RM) (American College of Sports Medicine, 2009). Exercise training using relatively light intensities [20–30% of maximal voluntary contraction (MVC)] in combination with an externally applied blood flow restriction (BFR) can elicit similar gains in skeletal muscle size and strength compared with traditional heavy-load resistance exercise (HLRE) (Shinohara et al, 1997; Karabulut et al, 2010; Yasuda et al, 2011). This lightintensity blood flow restriction exercise (BFRE) has significant practical application for a range of population groups that may be contraindicated to perform HLRE, such as older adults (Abe et al, 2010; Karabulut et al, 2010), athletes and/or patients recovering from musculoskeletal conditions such as anterior cruciate ligament injuries (Takarada et al, 2000b; Ohta et al, 2003). It so happens that few studies have attempted to examine the influence of different magnitudes of restriction pressure on acute responses to BFRE (Yasuda et al, 2008; Fatela et al, 2016), that may in turn influence the magnitude of any gains in skeletal muscle size and strength with chronic BFRE training
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
