Anthony Caterisano

The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles

The purpose of this study was to measure the relative contributions of 4 hip and thigh muscles while performing squats at 3 depths. Ten experienced lifters performed randomized trials of squats at partial, parallel, and full depths, using 100–125% of body weight as resistance. Electromyographic (EMG) surface electrodes were placed on the vastus medialis (VMO), the vastus lateralis, (VL), the biceps femoris (BF), and the gluteus maximus (GM). EMG data were quantified by integration and expressed as a percentage of the total electrical activity of the 4 muscles. Analysis of variance (ANOVA) and Tukey post hoc tests indicated a significant difference (p < 0.001*, p = 0.056**) in the relative contribution of the GM during the concentric phases among the partial- (16.9%*), parallel- (28.0%**), and full-depth (35.4%*) squats. There were no significant differences between the relative contributions of the BF, the VMO, and the VL at different squatting depths during this phase. The results suggest that the GM, rather than the BF, the VMO, or the VL, becomes more active in concentric contraction as squat depth increases.

The effect of differential training on isokinetic muscular endurance during acute thermally induced hypohydration

The purpose of this study was to test the effect of acute thermal hypohydration on the muscle endurance performance of three groups of differentially trained subjects. Group I consisted of six anaerobically trained athletes, Group II consisted of five aerobically trained athletes, and Group III consisted of six sedentary indi viduals. Experimental trials involved maximal leg exten sions performed on a Cybex II dynamometer under conditions of euhydration and hypohydration of minus 3% body weight. Integrated electromyographic data were also collected during each trial to factor out mo tivation as a variable. The maximum number of leg extension repetitions performed at or above 50% of each subjects peak torque output were compared between treatments and among the three groups. A 2 x 3 factorial analysis of variance (ANOVA) showed a significant decrease in muscle endurance when com paring euhydration to hypohydration among the anaer obically trained subjects as well as among the seden tary subjects (P < 0.05). The aerobically trained sub jects showed no significant decline in muscle endurance when comparing performance under both experimental conditions. It was hypothesized that the training adap tations that occur with aerobic conditioning and are primarily associated with increased plasma volume may be the key to explaining these results.

Prediction of Ground Reaction Forces of Flexible Barbells using their Bar End Displacement: 1830 Board #91 May 31 3

433 CONCLUSION: We observed a decrease in MMG QAMP during submaximal isometric contractions performed at the same absolute torques following 3 and 6 weeks of 80% 1RM, but not 30% 1RM resistance training. These decreases are similar to the reductions in voluntary activation that we observed previously at submaximal torques following 3 and 6 weeks of high-, but not low-load training. Therefore, we suggest that MMG amplitude is sensitive to training-induced changes in motor unit activation during highversus low-load training.