Effects of low-load blood flow restriction on the venous system in comparison to traditional low-load and high-load exercises

Alexander Franz; Sanghyeon Ji; Frank Sebastian Fröschen; Marleen Kerstin; Patrick Wahl; Michael Behringer

doi:10.3389/fphys.2023.1285462

December 15, 2023Frontiers in PhysiologyOpen Access

Effects of low-load blood flow restriction on the venous system in comparison to traditional low-load and high-load exercises

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Why the study?

Blood-flow-restriction training achieves hypertrophy with light mechanical loads, but its impact on venous pressures and venous function remains unknown.

Does low-load blood flow restriction resistance training alter intravascular venous pressure or venous function compared to traditional low-load and high-load exercises in healthy men?

Structured PICO

Does low-load blood flow restriction resistance training alter intravascular venous pressure or venous function compared to traditional low-load and high-load exercises in healthy men?

P

Population

10 healthy men, mean age 27.6 ± 6.4 years, with no prior vascular surgery of the lower extremities or blood disorders, experienced in resistance training (>2 years) but naive to BFR-RT.

I

Intervention

Low-load blood-flow-restriction resistance training (LL-BFR-RT) consisting of unilateral knee-extensor exercise at 30% of 1-repetition-maximum (1RM) with 50% limb occlusion pressure (LOP). Performed for 4 sets to volitional muscle failure, separated by 60 seconds of rest.

C

Comparator

Low-load resistance training (LL-RT) at 30% 1RM and high-load resistance training (HL-RT) at 75% 1RM, both performed without venous occlusion for 4 sets to volitional muscle failure, separated by 60 seconds of rest.

O

Outcome

Changes in intravascular venous pressure during exercise and venous function (assessed via phlebodynamometry including refill-time, rest pressure, minimal pressure, delta pressure, and offset time) before and after exercise.surrogate

Low-load blood flow restriction training to muscle failure does not acutely elevate venous pressures more than traditional resistance training and does not impair venous function, suggesting it is safe for the venous system in healthy individuals.

Limitations

Results are only generalizable for seated BFR-RT exercise due to the effect of positioning on resting venous pressure.
Comparison of the BFR method to a control condition without a volume-matched protocol.

Implication

Supports venous safety of LL-BFR-RT in healthy men; reinforces its viability as lower-workload training without venous compromise.

Abstract

Purpose: Blood-Flow-Restriction (BFR) training provides the ability to achieve hypertrophy effects even though only light mechanical loads are applied. However, its impact on venous pressures and function are still unknown. Therefore, the present study investigates the influence of BFR-training on intravascular venous pressure and venous function in comparison to control exercises with low or high mechanical loads. Methods: In a randomized cross-over design, ten healthy men (27.6 ± 6.4 years) underwent three trials of unilateral knee-extensor exercise with three different training protocols, low-load- (LL-RT, 30% of the individual 1-repetition-maximum, 1RM), low-load BFR- (LL-BFR-RT, 30% 1RM, 50% limb occlusion pressure, LOP) and high-load resistance exercise (HL-RT, 75% 1RM). Exercise protocols contain about four sets of knee extension exercise (Range-of-Motion: 0-0-95°), separated by 60 s of rest. Each set was performed until volitional muscle failure. For analysis of changes in intravascular venous pressures and venous function, a venous catheter was placed at the exercising leg before each trial. Whereas venous pressures were recorded throughout the exercise trials, phlebodynamometric investigations were performed before and after each trial. Furthermore, subjective pain perception during and after exercise was accessed by visual analogue scale. One-way ANOVA was used to assess mean differences between training protocols, while two-way repeated-measures ANOVA (rANOVA; time x condition) was performed to compare changes in measures over time among conditions. Data were given as means ± standard deviation (SD). Results: In comparison to the exercise trials without venous occlusion, total workload was significantly lower in the LL-BFR-RT (LL-RT: 1745 ± 604 kg vs LL-BFR-RT: 1274 ± 237 kg vs HL-RT: 1847 ± 367 kg, p = 0.004) without indicating statistical differences in venous pressures during the exercise sets (interaction: p = 0.140) or pain perception (interaction: p = 0.574). Similarly, phlebodynamometric assessment of venous function (e.g. refill-time of the venous system pre-vs. post exercise trials–LL-RT: 29.7 ± 11.0 s vs 25.5 ± 9.6 s, LL-BFR-RT: 26.6 ± 13.0 s vs 27.3 ± 13.8 s, HL-RT: 25.9 ± 10.9 s vs 23.1 ± 8.2 s) revealed no time ( p = 0.156), condition effect ( p = 0.802) or their interactions ( p = 0.382). Conclusion: The present study is the first one describing the acute effects of LL-BFR-RT to muscle failure on venous pressures and function in comparison to a LL- and HL-RT in the lower limbs. In contrast to the existing literature, LL-BFR-RT does not elevate the venous pressures during exercise higher than a comparative exercise without BFR and does not show any adverse effects on venous function after the exercise.