The acute effects of heavy-load squats on verticle jump height and neuromuscular activation characteristics in the thigh during a counter-movement jump
Cardiff Metropolitan University
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The purpose of the current study was to validate the complex training theory. The study aims to investigate the effects of a set of 6 repetition maximum (6RM) halÊ squats on neuromuscular activation characteristics in the thigh, and consequently vertical jump height; during a countermovement jump (CMJ). Complex training is a recently advanced power training method, and is charactenzed by a dynamic heavyload exercise proceeded immediately (0-30 s) by a biomechanically similar plyometric exercise. The theory suggests that the heavy-load induces optimal neuromuscular activation conditions, and consequently; enhances power during the plyometric exercise. If the theory is correct; complex training will provide maximal stimulus for neuromuscular adaptations, and allow the speed and strength components of power to be trained during the same session. 5 male sports science students of age; 22.4 (+2.4) years, weight; 81.2 (+8.2) kg, and stature; 173.2 (+16.3) cm, and at least one years squat training experience, performed a CMJ; pre (P1), and post (P2) a set of 6RM half-squats. Pl and P2 were performed on a Kistler force platform to determine jump height using the 'flight time' method, and neuromuscular activation characteristics were measured in the rectus femoris (agonist) and bicep femoris (antagonist). The EMG data was analysed for AEMG and MF scores. A change in AEMG during P2 was determined as change in motor unit recruitment and./or firing rate. A change in MF during P2 was determined as a change in firing rate. Results found no significant difference (p>0.05) in; CMJ height, MF in the agonist, AEMG in the antagonist, or MF in the antagonist. There was a significant decrease (p<0.05) in AEMG in the agonist during P2, representing neural fatigue, induced by the treatment. Analysis of individual scores showed each subject reacted to agonist neural fatigue, by displaying a negative response in at least one of the following factors; motor unit recruitment, firing rate, and/or agonist-antagonist activation patterns. In conclusion; the complex treatment did not enhance jump height but neither was it detrimental to perforrnance, and therefore may have organisational benefits during a high volume preparation phase. The complex treatment did however induce detrimental effects in certain neuromuscular activation characteristics, and therefore; was not found to be an optimal training modality. There is a suggestion that maximal neuromuscular activation conditions aro realised with a 3-5min recovery period post heavy-load, however additional support for this theory is required before employing complex haining during; pre-competition, competition or tapering periods. For reliable conclusions on the effectiveness of complex training; future research should investigate the manipulation of other haining variables such as; rest interval between complex sets, and number of complexes per session, within a training study.
BSc (Hons) Sport, PE and Recreation
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