In a previous blog post from August 05, intermittent BFR (deflating
the pressure in the inter-set rest period) was mentioned to mitigate or at least attenuate perceptual responses to BFR.
The actual effect of intermittent BFR (iBFR) vs Continuous BFR (cBFR) has recently been investigated in a review by Sinclair et al.
The present paper was conducted to decipher whether iBFR improves tolerance, without compromising strength, as iBFR VS cBFR on outcomes of exercise tolerance or strength.
Materials and Methods:
Only RCT’s were included in this review. The primary outcomes of interest were those describing tolerance to BFR during exercise:
• Rating of perceived exertion (RPE)
• Pain
• Discomfort
• Delayed onset muscle soreness (DOMS)
• Objective reporting of adherence rates and adverse events, with the appropriate reasons provided.
• Qualitative reporting of experiences and preferences.
Secondary outcomes:
Change in muscle strength.
Search strategy: Preferred reporting system for systematic reviews and meta-analyses (PRISMA) statement. Data analysis: Cochrane risk of bias tool for randomized trials e.g., randomization and allocation processes, blinding of participants, investigators and outcome assessors, and reporting of outcomes.
Results:
186 studies were selected, but only 9 RCT’s were included published between 2013-2019, 7 were cross-over by design.
The iBFR groups of all studies had their cuffs deflated in the inter-set rest periods. All but one study deflated the cuffs during the rest periods between exercises for both iBFR and cBFR.
Primary outcome:
There was no significant difference in RPE between BFR training methods, however, the effect estimate shifted towards the use of iBFR.
Secondary outcome:
No significant strength difference between BFR groups.
Discussion:
It seems iBFR may be better tolerated than cBFR. The overall difference in the meta-analysis however did not show significant variance. Additionally, there is limited evidence to suggest that comparable gains in strength can be expected.
Conclusion:
Deflating the cuffs risks attenuating the metabolic stress and thus the mechanism by which BFR exerts its effects on hypertrophy and strength. It is recommended that further research in this area focus on other means to improve tolerance to exercise.
Primary Source:
Sinclair et al. (2021) Tolerance to Intermittent vs. Continuous Blood Flow Restriction Training: A Meta-Analysis.
