• DOI: 10.1249/MSS.0000000000002544

The aim of this study was to investigate the effects of repeated application of BFR+EMS on preserving skeletal muscle mass and strength during a period of limb disuse. It was hypothesized that repeated BFR+EMS treatment would be more effective than repeated BFR treatment without EMS for attenuating the loss of quadriceps mass and knee-extension strength during a 14-day leg unloading period

Subjects

A mixed-sex group of 30 healthy, young individuals (14 males, 16 females; age: 22 ± 3 years; body mass index: 23 ± 3 kg.m -2) who were naïve to BFR training were recruited from the university and surrounding community.

Study design

Participants were randomly allocated to either the control (CON; n = 10), BFR (n = 10), or BFR+EMS (n = 10) group. All three groups underwent a 14-day period of single-leg muscle unloading through use of a knee brace and crutches. Unloading was performed using the left leg of all participants to allow safe operation of a motor vehicle during the study. Over the 14-day
unloading period, participants had no intervention (CON), or underwent treatment with either BFR or BFR+EMS twice daily, 5 times per week, for a total of 20 treatment sessions.

Interventions

BFR was performed with the participant in a sitting position using arterial occlusion accomplished via a PTSi automated tourniquet system (Delfi Medical Innovations Inc. Vancouver, Canada). Full arterial occlusion was chosen to maximize the metabolic stimulus and adaptive training response (18). An 11-cm wide tourniquet cuff was positioned proximally around the left thigh and inflated to a pressure that was minimally superior to systolic pressure (≥ 2 mmHg), allowing for arterial occlusion. This pressure, also referred to as the lowest effective occlusion pressure (LOP).

Muscle stimulation for the ITT was performed using a constant current high voltage stimulator (model DS7AH, Digitimer, Welwyn Garden City, Hertfordshire, UK) where evoked twitches were delivered to the knee extensors transcutaneously using two custom electrode pads, previously described by Dalton et al. (17). Electrodes were placed perpendicular to the long axis of the femur, with the proximal pad at ~5 cm above the kneecap and the distal pad ~10 cm above the proximal electrode, covering the anterior aspect of the thigh completely.

BFR + Muscle stimulation in combination

Discussion

Data reported here suggests that repeated BFR+EMS treatment represents an effective interventional strategy to attenuate muscle disuse atrophy, which is known to lead to reduced functional capacity (21- 23), a shift in fuel metabolism (24), impaired muscle insulin sensitivity (25), a decline in basal metabolic rate (26, 27), and an increase in body fat mass (28). Given the ability to use BFR+TEMS as a “passive” treatment modality requiring no external load, these data are relevant to persons immobilized from injury or illness, persons who are differentially-abled or confined to a wheelchair, astronauts living in reduced gravity environments, or others seeking to minimize the consequences of muscle disuse atrophy. Specific applications to those rehabilitating from sports and orthopaedic injuries are perhaps obvious, and with the known association of muscle mass with cardiometabolic health and acute blood sugar maintenance through glucose uptake (29, 30), it is possible that further applications exist for persons who are faced with acute or chronic forced sedentarism.

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However, we believe that BFR+EMS likely presents a more effective method to attenuate muscle loss compared to EMS alone as a previous study shows a greater recruitment of muscle fibers when blood flow is restricted during electrically evoked muscle contractions (37) compared to when electrically evoked muscle contractions are performed without blood flow restriction.

In conclusion

In conclusion, the combined treatment of BFR+EMS uniquely preserves muscle mass during a period of limb disuse, while BFR treatment without EMS did not protect against this expected disuse atrophy. These results suggest that BFR+EMS treatment, but not BFR treatment alone, represents an effective interventional strategy to attenuate muscle atrophy during a period of disuse and this may have implications across a variety of health and performance applications wherein disuse cannot be avoided.