Practical Occlusion: Ratings of Pain and Exertion Following 2 Sets to Muscular Failure

Abstract

Low intensity resistance training, with restricted blood flow, using specialized equipment has been demonstrated to result in skeletal muscle hypertrophy benefiting those who cannot sustain high intensity exercise. Recently, low intensity resistance training (30% 1RM) to failure without occlusion has been demonstrated to result in similar muscle protein synthesis (MPS) responses as high intensity exercise (90% 1RM) to failure. However, a low load protocol requires more repetitions to stimulate MPS, and those with lower limb injuries may be incapable of sustaining the mechanical stress to reach muscular failure. Practical occlusion with knee wraps (KW) around the upper thigh provides a mode of decreasing time to failure, while maintaining a low external load. Research using specialized equipment for restricted blood flow has previously demonstrated higher ratings of pain (P), with no difference in ratings of perceived exertion (RPE), but this has yet to be investigated using practical occlusion. PURPOSE: To quantify the P and RPE of low intensity exercise to failure using KW as a practical occlusion stimulus. METHODS: Fifteen healthy men and women participated in a randomized crossover study consisting of 3 trials separated by at least 7 days. The first trial determined their one repetition maximum (1RM) on the leg extension. Upon determination of 1RM, subjects were assigned to an occlusion (OCC) or a control (CON) group. After the second trial, subjects crossed over to complete the opposite trial. KW (76 mm wide) were placed around the upper thigh of each leg during OCC to serve as the practical OCC. Subjects completed the leg extension exercise on a selectorized machine for 2 sets at 30% 1RM until muscular failure with 30 seconds rest between sets. Muscular failure, defined as the point at which repetitions could no longer be completed through a full range of motion and total work defined by the repetitions multiplied by the external load. RPE and P were taken immediately after each set. Mean ± SD subject characteristics were age 21.7 ± 2.18 yr, height 171.9 ± 9.14 cm, body mass 78.3 ± 21.84 kg. Data were analyzed using a paired sample t-test with an alpha level of 0.05. RESULTS: The volume of work completed was significantly lower during practical OCC (p = 0.001) [OCC 619.86 ± 276.18 vs CON 962.25 ± 344.14 kg]. P ratings were similar for OCC and CON after the 1st set (p = 0.15) [OCC 5.00 ± 2.58 vs CON 4.2 ± 1.97] but was significantly greater following the 2nd set (p = 0.009) [OCC 6.43 ± 2.63 vs CON 4.93 ± 2.59] with OCC. RPE was significantly higher with OCC for the 1st (p = 0.01) [OCC 5.53 ± 2.06 vs CON 4.36 ± 1.23] and 2nd set (p = 0.003) [OCC 6.46 ± 2.35 vs CON 5.10 ± 2.07]. CONCLUSIONS: KW provide a practical occlusion stimulus allowing muscular failure to occur at a lower overall volume of work, during low intensity leg extensor training. P was increased after the 2nd set, while RPE was higher following both sets of exercise with practical OCC. The higher RPE seen in this study differs from previous studies using blood flow restriction techniques. PRACTICAL APPLICATIONS: Although KW allow muscular failure to occur with a lower total volume of work, the P and RPE ratings were higher when applied. The high acute P rating with practical OCC may limit its application to the highly motivated. Despite this limitation, KW may serve as a stimulus to increase MPS for populations in which high intensity exercise is contraindicated, or those who cannot sustain the mechanical stress of low intensity exercise with normal blood flow which requires more total work to be completed until muscular failure (e.g., early rehabilitation after a sports injury).