How much pressure is needed for BFR Training? – The Pressure-Load Continuum

A recent review by Queiros et al. has explored how different restriction pressures measured as % Limb Occlusion Pressure / Arterial Occlusion Pressure (LOP) effects fatigue.

📍Background:

Considering the association between metabolite induced fatigue with muscle hypertrophy, some authors have investigated how manipulating BFR pressures during exercise can exert an effect on the level of acute fatigue e.g.,., Maximum Voluntary Contraction (MVC) or electromyography (EMG).

The data from the original studies are divergent, but it seems that very low-load resistance exercise performed with higher pressures evokes higher levels of acute fatigue and overall training effect known as the pressure-load continuum.

📍Aim:
Systematically review and pooling of available data on neuromuscular and metabolic responses at Low-Load BFR resistance exercise (LL-BFR) with different pressures (% of LOP/AOP).

The effects of different restriction pressures on neuromuscular responses can assist trainers and physical therapists in more appropriate and safer prescriptions.

Main Outcomes:
1. Maximum Voluntary Contraction (MVC)

2. Surface Electromyography (EMG)

1. MVC:
40% vs. 60% LOP – No difference.

30% of 1 RM: 40-50% vs. 80-90% LOP – No difference.

15-20% 1 RM: 40-50% vs. 80-90% LOP – Favor of High Pressure.

40-80% LOP vs. No-BFR (Free Flow) – Favor of BFR.

2. EMG:

“Not failure protocols”: 40% vs. 60% or 80% LOP – Favors Higher Pressure.

“Failure protocols”: 40% vs 80% LOP – Favors Less Pressure

Low-load 40-80% LOP vs. Low-Load No-BFR – No difference.

Low-load 40-80% LOP vs. High-Load No-BFR – Favors High-Load.

📌📌Conclusion

Not surprisingly, low-load resistance exercise with (40-90% LOP) BFR pressure induces more fatigue than No-BFR low-load.

For very low-load (15–20% 1RM) higher pressure (about 80% LOP) can increase the magnitude of fatigue and are thereby recommended. On the other hand, it seems that higher pressures (≥80%) with loads of 20-40% 1 RM should not be performed to failure but instead use a pre-defined repetition schemes e.g., 30x15x15x15 reps.

📄Primary Source:
Queiros et al. (2021) Myoelectric Activity and Fatigue in Low-Load Resistance Exercise With Different Pressure of Blood Flow Restriction- A Systematic Review and Meta-Analysis