Isometric Strength Training Across Multiple Joint-Angles Versus Concentric-only Strength Training on Strength and Fatigue Adaptations in Resistance-Trained Males

Naidu, R. S. Rayen (2025) Isometric Strength Training Across Multiple Joint-Angles Versus Concentric-only Strength Training on Strength and Fatigue Adaptations in Resistance-Trained Males. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This study compared the effectiveness of isometric strength training (IST) performed at multiple joint angles versus concentric-only strength training (CONonly) on fatigue resistance and strength adaptations in young resistance-trained males. Fifteen participants (age = 22.3 ± 1.1 years; weight = 72.2 ± 14.9 kg; height = 173.8 ± 4.4 cm; resistance training experience = 2.9 ± 1.4 years) were assigned to either an IST group (n=7) performing isometric deadlifts at two joint angles or a CONonly group (n=8). Both groups followed their respective protocols throughout a six-week progressive training programme consisting of two weekly sessions. Outcome measures included concentric strength (1-repetition maximum deadlift); 1RM DL), isometric strength (isometric mid-thigh pull; IMTP), concentric-related fatigue resistance (80-second repeated squat jump test; SJ80), and isometric-related fatigue resistance (IMTP fatiguing protocol). Results showed significant main effect of time for concentric strength, isometric strength, and concentric-related fatigue resistance (p<0.001), indicating overall pre-to-post improvements across participants. However, no significant changes were observed in isometric-related fatigue resistance (p>0.699). No significant main effects of group or time × group interactions were observed (all p>0.05), suggesting that both training modalities induced comparable strength gains, with neither improving fatigue resistance. These findings suggest that both IST and CONonly strength training show similarly effectiveness in improving maximal strength (1RM DL, IMTP) and concentric-related fatigue resistance (SJ80) in resistance-trained males, while neither improves isometric-related fatigue resistance. Thus, both modalities are equally effective for strength and dynamic fatigue improvements, but not isometric endurance. Future studies should explore hybrid multi-angle IST with dynamic training, longer interventions (>12 weeks), and objective monitoring (e.g., force sensors) to optimize adaptations.