The Effect of Increasing Blood Flow Restriction Pressure When the Contractions Are Already Occlusive

Context: Blood flow restricted exercise involves the use of external pressure to enhance fatigue and augment exercise adaptations. The mechanisms by which blood flow restricted exercise limits muscular endurance are not well understood. Objective: To determine how increasing blood flow restriction pressure impacts local muscular endurance, discomfort, and force steadiness when the contractions are already occlusive. Design: Within-participant, repeated-measures crossover design. Setting: University laboratory. Patients: A total of 22 individuals (13 males and 9 females). Intervention: Individuals performed a contraction at 30% of maximal isometric elbow flexion force for as long as possible. One arm completed the contraction with 100% of arterial occlusion pressure applied, while the other arm had 150% of arterial occlusion pressure applied. At the end of the protocol, individuals were asked to rate their perceived discomfort. Main Outcome Measures: Time to task failure, discomfort, and force steadiness. Results: Individuals had a longer time to task failure when performing the 100% arterial occlusion condition compared with the 150% arterial occlusion pressure condition (time to task failure = 82.4 vs 70.8 s; Bayes factors = 5.77). There were no differences in discomfort between the 100% and 150% conditions (median discomfort = 5.5 vs 6; Bayes factors = 0.375) nor were there differences in force steadiness (SD of force output 3.16 vs 3.31 N; Bayes factors = 0.282). Conclusion: The results of the present study suggest that, even when contractions are already occlusive, increasing the restriction pressure reduces local muscle endurance but does not impact discomfort or force steadiness. This provides an indication that mechanisms other than the direct alteration of blood flow are contributing to the increased fatigue with added restrictive pressure. Future studies are needed to examine neural mechanisms that may explain this finding.

Title: Blood flow restricted exercise training: Perspectives of people with chronic obstructive pulmonary disease and health professionals

Objective This descriptive qualitative study explored perspectives of people with chronic obstructive pulmonary disease (COPD) and health professionals concerning blood flow restricted exercise (BFRE) training. Methods People living with COPD and health professionals (exercise physiologists, physiotherapists, and hospital-based respiratory nurses and doctors) participated in interviews or focus groups, which included information about BFRE training and a facilitated discussion of positive aspects, barriers and concerns about BFRE training as a possible exercise-based intervention. Sessions were audio-recorded, and transcript data analysed using inductive content analysis. Results Thirty-one people participated (people with COPD n = 6; health professionals n = 25). All participant groups expressed positive perceptions of BFRE as a potential alternative low-intensity exercise mode where health benefits might be achieved. Areas of overlap in perceived barriers and concerns included the need to address the risk of potential adverse events, suitability of training sites and identifying processes to appropriately screen potential candidates. Discussion While potential benefits were identified, concerns about determining who is safe and suitable to participate, delivery processes, health professional training and effects on a variety of health-related outcomes need to be addressed before implementation of BFRE training for people with COPD.

Physiological responses of human skeletal muscle to acute blood flow restricted exercise assessed by multimodal MRI

Acute changes in blood flow, diffusion, blood oxygenation, cross-sectional area, and the “T2 shift” are evaluated in human skeletal muscle in response to blood flow-restricted (BFR) and conventional free-flow knee extensor exercise performed in an MRI scanner. The acute physiological response to exercise was dependent on the magnitude of load and the application of BFR. Physiological variables changed markedly and established a steady state rapidly after the first of four exercise sets.