Joint and pull phase specific relative effort in weightlifting and simulated training effects

The purposes of this study were to quantify the relative effort (RE) of the extensor and plantarflexor muscles during the clean and simulate the effects of strength and speed-strength training on joint and pull phase specific RE. Five weightlifters performed the clean at 85% of their one-repetition maximum, while motion capture and ground reaction forces were recorded and used to calculate lower body net joint moments via inverse dynamics (NJM_ID). Joint angle and angular velocity data were used as input to a musculoskeletal model that estimated maximum NJM (NJM_max) weightlifters could theoretically generate. The RE of the hip and knee extensor and ankle plantarflexor muscles were calculated as the ratios between NJM_ID and NJM_max. Model parameters were changed to simulate the effects of strength and speed-strength training. Results show that simulated strength training decreased RE of all muscle groups during the first and second pull. In contrast, speed-strength training decreased hip extensor and knee extensor RE during the first pull and second pull, respectively. Strength training may have broad and consistent effects on RE during the clean, whereas speed-strength training may have more joint and phase-specific effects.