29/10/2024
Passive blood flow restriction - To contract or not?
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The recovery from illness or injury can require otherwise healthy individuals to undergo a period of muscle disuse (e.g. bed rest or limb immobilization). A major consequence of disuse is skeletal muscle atrophy with evidence showing a substantial decline in muscle mass and strength after only 5 days of limb immobilization (Wall, 2014). The rapid loss in muscle mass with immobilization is particular for anti-gravity muscles such as the quadriceps, and also occurs with a faster rate after surgery compared to “controlled immobilization” of healthy individuals.
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Passive application of blood flow restriction is a proposed method to minimize loss in muscle mass and function (Patterson, 2019 & Scott, 2023). Early papers of Takarada (2000) and Kubota (2008 & 2011) support the use of passive BFR to minimize loss in muscle mass and/or function with a [5 x 5 min, 3 min rest, 2 x d for 2 wk, pressure; 50-260 mmHg], however later research from Iversen (2016), who also used post-op patients after ACL reconstruction as Takarada, failed to find improvements with the same BFR protocol added to a standard-care treatment.
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Indirect evidence from Nyakayiru 2019, found that only BFR with exercise increased myofibrillar protein synthesis rates at 5-h post stimuli compared to a passive BFR application in resting conditions, indicating a need to add muscle contraction to utilize the effect of BFR.
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In a recently published study (Fuchs 2024) a group of researchers measured the impact of BFR on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest in 12 healthy male adults. One leg received passive BFR (3 x 5 min inflation w. 1.5 min rest, 3 times/day, pressure: 200 mmHg, 45 min total BFR/day for 14 days) while the other leg served as control. The results showed that both legs had significant loss in muscle mass and strength and there was no difference between conditions.
In contrast, the use of passive BFR has been found to reduce muscle atrophy in elderly coma patient in the intensive care unit (ICU). Like Fuchs, Barbalho 2018 also used a with-in patient design, where one leg received passive mobilization + BFR (intervention) and the other leg only received passive mobilization (control). The authors found that both legs atrophied during ICU but the loss in muscle mass was lower after BFR + passive mobilization.
With conflicting results in the litterature it remains unknown if passive BFR alone can protect against muscle atrophy. We tend to support that some sort of muscle contraction leading to single fiber mechanical tension is needed with BFR, as it is proposed to be the primary mechanism driving muscle hypertrophy (Wackerhage 2019).
One way of adding involuntary muscle contraction is with Neuromuscular Electrical Stimulation (NMES). NMES is commonly used as a rehabilitative technique for preventing muscle atrophy during immobilization periods. It is proposed that the combination of BFR and NMES provides a synergistic effect in which hypertrophy may be possible as a passive intervention. In a with-in patient design, a high frequenzy training protocol; twice daily, 5d/week for 2 wk consisting of involuntary NMES combined with BFR (NMES-BFR leg) improved isometric and isokinetic quadriceps strength and muscle mass. The control leg (NMES-only leg), only had a negligible effect on isometric strength (Natsume 2015).
Likewise, the use of synergist exercises (hip abduction, adduction or flexion) or early very-low load exercises with limited range of motion (seated quadriceps contractions and closed chain knee extensions) can be effective strategies to add muscle contraction within the limitations of an injury or post-surgery. 12 (Jack 2023) and 16 week (Ohta 2003) training including these modalities with BFR following ACL reconstruction improved outcome parameters like strength, muscle mass and time for return-to-activity.
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