Increase Pressure (mmHg) During BFR Training Interventions?

📝A literature review (@msccerqueira et al. 2021) containing 29 original papers on cardiovascular adaptations to BFR training explores whether increasing pressure is warranted!?

❕️Blood Flow Restriction Pressure – absolute mmHg or % limb occlusion pressure (BFRP)

📌Introduction:
A major methodological concern in BFR training both from a practical and research perspective is how much BFRP is needed for optimal safety and effectiveness.

Cardiovascular adaptations to BFR and their possible relationship with BFRP are currently not well understood.

Subsequently, it is unknown if increased BFRP throughout a training intervention is needed for optimal outcomes!? Though many studies increase BFRP, it is unclear whether adjustments are warranted.

📍Methods:
Studies included assessments of chronic effects of BFR (>3 weeks of training) and outcomes that may influence BFRP.

Macro- and Microvascular Function & Adaptations to BFR:
BFR potentially increases vasodilatory capacity to reactive hyperemia reducing peripheral vascular resistance, stimulating capillarization, improving arterial compliance, less stiffness, and increasing arterial diameter.

Though, there is a rationale for decreasing BFRP based on vascular adaptations like reduced blood pressure.

❔️Is BFRP Adjusted in the Research? 35% (n =10) of the included studies adjusted BFRP during BFR training intervention with different rationales for BFRP adjustments: To achieve high levels of perceived effort, allow participants to adapt to the occlusion stimulus or impose progressive overload in muscles and circulation.

❔️Need for BFRP Adjustments?
When using fixed BFRP perceived effort and pain may decrease during the intervention period without impairing neuromuscular gains. unnecessary increases in BFRP may contribute to discomfort, impair adherence, and increase the risk of adverse events.

Conclusion:
Currently, no clear justification is provided in the literature for BFRP prescription during BFR exercises, and no specific recommendation can be identified if BFRP should be adjusted during a BFR training intervention.

Considering the possible lowering effect of BFR training on blood pressure, longitudinal studies directly measuring BFRP are needed to establish whether the effect is different in clinical populations.

Future studies should explore if changing BFRP makes BFR training safer and/or more comfortable with similar physiological adaptation!? And discover if there is a BFRP upper or lower threshold to induce cardiovascular adaptations.

Comments:
Anecdotical evidence can probably verify that starting with less BFRP seems to improve the likelihood of adherence to BFR Training. This highly relevant clinical concern has been elaborated by Rolnick et al. (2021).

Worth noting is the common and warranted individual approach to general training dosage that inherently also applies to BFRP. Folks which either are experienced with resistance-type exercise or just being highly motivated may start with higher BFRP (60-80% LOP) as Ratings of Perceived Effort or pain might not be a relevant barrier. On the other hand, less experienced individuals or fragile elderly might benefit from starting with less BFRP (40-50% LOP).

Another important perspective is the other relevant parameters of progression in BFR Training. In both clinical practices and effect studies, if the resistance/load is progressed accordingly throughout the intervention period, alteration of BFRP is probably not warranted above the common threshold of ~50% LOP.

Future research could feature a 3-group design with the following effect parameters: Constant BFRP VS Increasing BFRP VS Decreasing BFRP.

Muscle strength/hypertrophy & Changes in central and/or peripheral cardio vasculature & Adherence as either drop-out/self-reporting acceptability of the intervention

Primary Source: Cerqueira et al. (2021) Blood Flow Restriction Training – To Adjust or Not Adjust the Cuff Pressure Over an Intervention Period.
DOI: 10.3389/fphys.2021.678407

Secondary Source: Rolnick et al. (2021) Perceived Barriers to Blood Flow Restriction Training.
DOI.org/10.3389/fresc.2021.697082