Morgan R. Wood1, Marissa Bello2, Zachary Gillen1, JohnEric Smith1. 1Mississippi State University, Mississippi State, MS. 2Univeristy of Alabama at Birmingham, Birmingham, AL.

Background Programmed resistance training to optimize muscle strength is a vital component of exercise programs for athletes and non-athletes alike. Training with high-loads (≥80% of maximum) has been reported to be a more effective method of increasing muscle strength, compared to training with low-loads (≤30% of maximum). The purpose of this study was to compare changes in lower-body strength after 9-weeks of high- vs. low-load using a full-body resistance training protocol. Methods Seventeen recreationally trained males were selected for this study (mean± standard deviation age=20.4±2.7 yrs; weight=77.9±16.5 kg) and were randomly split into a high- (85% 1-RM; n=8) or low-load (30% 1-RM; n=9) training group. Both groups completed 3 training sessions per week, with 3 working sets to failure of the back squat, bench press, deadlift, t-bar row, biceps curl, and lying triceps extension. Predicted 1RM was taken pre- and post-resistance training for the back squat and deadlift. Isometric and isokinetic (angular velocities= 60 and 120̊·s-1) assessments of peak torque were taken for knee flexion and extension. Differences in changes of lower-body strength between groups were compared using change scores (Δ1RM) calculated post-pre. Independent samples t-tests were used to compare Δ1RM between groups. Mixed Factorial ANOVAs were used to compare change in 1RM within and between groups. Results Significant differences were found between groups for Δ1RM in the back squat (p=0.012) and deadlift (p=0.031), with significant increases in the 85% group in back squat (p=0.014) and deadlift(p=0.002). Significant decreases in both groups were found in 60̊·s-1 knee flexion (p=0.005). No significant differences were found for any other measure (p≥0.078). Conclusion This study demonstrates a full-body high-load resistance training program results in greater changes in back squat and deadlift strength overall, but not isometric or isokinetic strength. It is possible the changes in peak torque from the isolated, single-joint knee flexion and extension muscle actions were not as sensitive to change, as these movements do not permit hip flexion or extension during the muscle action. Thus, the principle of specificity must be considered. Overall, the present study demonstrates training at high-loads is more impactful for improving lower-body strength during dynamic, compound movements than training at low-loads.

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