The development of blood flow restriction training as a rehabilitation adjunct following musculoskeletal lower-limb injury

Smith, Philip James (2017) The development of blood flow restriction training as a rehabilitation adjunct following musculoskeletal lower-limb injury. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Blood flow Restriction Training [BfRT] involves the intentional and temporary reduction of blood flow through a limb to induce short periods of mild limb ischaemia, often during periods of low-intensity exercise. A systematic review into the use of BfRT to attenuate losses to lower-limb muscle strength and size during periods of injury-related impaired weight bearing revealed wide variations in the equipment, methodology and outcomes described. No evidence specifically investigated the acute physiological effect of BfRT during un-resisted, or ‘no-load’ rehabilitation exercises. This doctoral research project aimed to address these issues, by developing externally-valid BfRT methodologies utilising relatively inexpensive BfR equipment, and determining the acute physiological effects of combining BfRT with ‘no-load’ lower-limb exercise. Phase I recruited sixty-one healthy participants across 3 subgroups; 21 males, 19 females and 21 elite male rugby players. Short periods of lower-limb blood flow restriction [BfR] were applied to participants at 40, 60, 80, 100 or 120mmHg via a thigh blood-pressure cuff. Ultrasound imaging was used to quantify the degree of popliteal arterial blood-flow remaining [%PBfR] at each cuff pressure. Subgroups were statistically different to each other across nine physical characteristics (p ≤ 0.05). %PBfR decreased as cuff pressure increased (p < 0.0001), but with no between-subgroup differences (p = 0.122). Only weak bivariate correlations existed between physical characteristics and %PBfR across tested cuff pressures. A polynomial equation was created to indicate %PBfR based only upon the amount of thigh-cuff pressure applied. Phase II recruited sixteen participants (n=9 male, n=7 female) who undertook four un-resisted, seated, unilateral knee extension exercise sessions with 0, 40, 60 or 80mmHg of continuous thigh-cuff pressure applied. A near-infra red spectroscopy [NIRS] device measured tissue oxygen saturation [SmO₂] of the vastus lateralis muscle before and during exercise sessions. Compared to 0mmHg, greater cuff pressures resulted in greater drops in vastus lateralis SmO₂ during exercise sessions (p < 0.05). Bivariate correlations existed between physical characteristics and the mean magnitude of change in SmO₂ during BfRT sessions, including Body Mass Index (Pearson r = 0.791, p < 0.001). Phase III recruited three injured professional rugby players to undertake lower-limb BfRT 4-5 times per week over periods of 4 to 12 weeks. BfRT sessions were as per Phase II, but delivered at higher cuff pressures (100 and 120mmHg). No adverse events or pain occurred during any BfRT session. NIRS data indicated that greater cuff pressure resulted in greater drops in vastus lateralis SmO₂ during exercise sessions. Thigh girth (recorded via tape measurement) was maintained longitudinally in all players. MRI evidence suggested that BfRT did not hinder healing from a tibial and femoral osseous stress injury. This doctoral project has expanded the evidence base available to healthcare professionals wishing to use BfRT during lower-limb injury rehabilitation. In particular, findings support the use of relatively inexpensive blood-pressure cuffs as a method of delivering BfRT, and in the ability of BfR to amplify the acute, local metabolic demand of an un-resisted ‘no-load’ exercise suitable for use in rehabilitation.