Effect Of Blood Flow Restricted Knee Extension On Exercise-induced Hypoalgesia At Upper And Lower Limb

Abstract

Previous research using repetition matched conditions found greater hypoalgesic responses to low load blood flow restricted exercise compared to non-blood flow restricted exercise. However, it is unknown if the addition of blood flow restriction to low load exercise can elicit any additional exercise-induced hypoalgesic effects when the exercise is taken to failure. PURPOSE: To examine the effect of knee extension exercise with blood flow restriction on exercise-induced hypoalgesia at an upper and lower limb. METHODS: 20 participants performed 2 trials in a random order: knee extension exercise at 30% of one-repetition maximum (KE); and KE with blood flow restriction at 80% of resting arterial occlusion pressure (KE + BFR). The KE exercise involved 4 sets of unilateral knee extension until failure with 30-sec rest intervals between sets. The total number of repetitions for each condition was recorded. Pressure pain thresholds (PPT) were assessed before (twice) and 5-min post exercise at an upper (forearm) and lower (tibialis anterior) limb. The change scores between two pre-exercise measurements (11 minutes apart) from both conditions were averaged and used as a control (CON). A Bayesian paired-samples t-test was performed to assess differences in the total number of repetitions, and a Bayesian one-way ANOVA of change scores was used to examine if the exercise-induced hypoalgesia changed differently between conditions. RESULTS: At the upper limb, PPT increased following both exercise conditions compared to CON (KE: 0.36 kg/cm2, KE + BFR: 0.35 kg/cm2, CON: -0.01 kg/cm2, BF10 = 3167.8) without any differences between exercise conditions. At the lower limb, PPT increased following both exercise conditions compared to CON (KE: 0.56 kg/cm2, KE + BFR: 0.64 kg/cm2, CON: -0.01 kg/cm2, BF10 = 4.260e+6) without any differences between exercise conditions. The total number of repetitions was lower in KE + BFR (39.6 repetitions) compared to KE (68.4 repetitions) (BF10 = 3.260e+8). CONCLUSIONS: Performing an acute bout of low load knee extension exercise until failure with blood flow restriction did not provide additional exercise-induced hypoalgesia. However, the addition of blood flow restriction can induce similar hypoalgesic response to that of non-blood flow restricted exercise with a fewer number of repetitions.