Practical Occlusion: A Mode to Increase Low Load Intensity

• Published in: Journal of strength and conditioning research 2011-03, Vol.25, p.S46
• Main Authors: Loenneke, J P, Balapur, A, Thrower, A D, Pujol, T J
• Format: Article
• Language: English
• Subjects: Muscular system; Proteins
• ISSN: 1064-8011; 1533-4287
• DOI: 10.1097/01.JSC.0000395649.16595.cd

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. Muscular failure requires the recruitment of anaerobic fast twitch (FT) fibers, which contain 3-4 times more S6k1 , a MPS signaling protein, than slow twitch fibers (ST). However, a low load protocol would likely require more repetitions to stimulate MPS. Those with lower limb injuries may be incapable of sustaining the mechanical stress to reach muscular failure. A practical occlusive stimulus with elastic knee wraps (KW) around the upper thigh may provide a mode of increasing exercise intensity while maintaining a low external load. PURPOSE: To determine if KW provide a practical stimulus to significantly decrease the time to failure during low-intensity exercise. METHODS: Twenty 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 at 30% 1RM until muscular failure. 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. Whole blood lactate (WBL) samples were taken before exercise, following muscular failure, and 3 minutes post. Mean ± SD subject characteristics were age 22.1 ± 1.29 yr, height 167.66 ± 17.40 cm, body mass 75.84 ± 16.66 kg. Data were analyzed using a paired sample t-test with an alpha level of 0.05. RESULTS: The number of repetitions to failure was significantly lower with OCC (p = 0.001) [OCC 26.00 ± 5.87 vs CON 36.65 ± 11.36] and the volume of work completed was also significantly lower during practical OCC (p = 0.001) [OCC 555.80 ± 238.40 vs CON 766.60 ± 297.26 kg]. WBL was signific