Blood flow occlusion superimposed on submaximal knee extensions does not evoke hypoalgesia: A pilot study

Exercise-induced hypoalgesia (EIH) is a transient decrease in pain perception that can be observed following various tasks, including non-painful low-intensity and painful high-intensity exercise. The application of blood flow occlusion (BFO) can help enhance exercise adaptations while being able to exercise at a low intensity, which has important implications for clinical and rehabilitative settings. Through descending inhibitory pathways, BFO-induced pain can potentially alleviate exercise-induced pain. This study aimed to assess whether the superimposition of BFO - and its associated augmented perceived responses - during low-intensity, low-volume resistance exercise could induce hypoalgesia. Nineteen healthy adults (10 females) attended three sessions: i) no exercise (CTRL), ii) two minutes of dynamic single-leg knee extension at 10% body weight (EXER), and iii) EXER with complete occlusion applied to the upper exercising leg (OCCL). Handheld algometry-derived pain pressure threshold (PPT) of the trapezius and contralateral and ipsilateral rectus femoris muscles were measured pre- and post-exercise, and after 5 and 10 min of recovery. Perceived pain (0-10) and effort (6-20) were also rated after exercise. Although pain and effort were augmented in the OCCL condition (Pain: 6{+/-}2; Effort: 14{+/-}3) compared to CTRL (Pain: 2{+/-}2, p<0.001; Effort 9{+/-}2, p=0.017), PPT of all muscles did not change across time nor between any conditions. Therefore, the low-intensity, low-volume resistance exercise prescribed in the present study was insufficient to evoke EIH even with the application of BFO-induced pain.