Effect of Submaximal Concentric and Eccentric Training on Torque Steadiness of the Ankle Plantarflexors


1Rozea G., 2Tillman M., 2Dodd S., 2Chmielewski T., 1Vanic, K., 1East Stroudsburg University, East Stroudsburg, PA, 2University of Florida, Gainesville, FL,

Purpose: This study was conducted to determine the effects of submaximal training of the plantar flexor muscles on the neural control and proprioception at the ankle during eccentric actions. Eccentric (ECC) muscle actions are a crucial part of movements during everyday activities and athletic competitions. Maximal ECC actions are up to 40% more forceful than maximal concentric (CON) actions and result in the greatest number of muscle injuries. Current knowledge of neural mechanisms controlling ECC is limited. The effects of submaximal training on torque steadiness and neural control has not yet been investigated. The purpose of this study was to determine effects of submaximal CON/ECC training, movement speeds, and muscle actions on torque steadiness. Methods: Using the Kin-Com AP, participants performed a torque steadiness test using 40% MVIC torque during an ISOK CON/ECC plantar/dorsiflexion motion. Participants were tested pre- and post-training. Training consisted of one week of submaximal (40%) plantar/dorsiflexion torque steadiness training 3 sets of 10 repetitions at the three testing speeds. Fifteen participants and their matched controls (12 male, 18 female; age = 22.0 ± 3.2 years, height = 169.6 ± 9.9, mass = 75.0 ± 13.7) were tested. Independent variables included treatment (training and control), velocity (10°/s, 20°/s, 30°/s, 40°/s), and muscle action (CON and ECC). Three MANOVAs were used to determine differences in torque steadiness, mean EMG, and peak/mean EMG. The dependent variables for torque steadiness included coefficient of variation (CV) and absolute error scores; for muscle activity mean EMG and P/M EMG both for gastroc and soleus. Results: The submaximal training significantly improved both measures of participants’ torque steadiness (F(6,852) = 32.636, p < .001), increased velocity significantly decreased torque steadiness (F(6,852) = 6.694, p < .001), and eccentric muscle actions had significantly decreased torque steadiness compared to concentric (F(2,425) = 6.055, p = .003). Conclusion: The training protocol improved measures of torque steadiness. Mean EMG increased with training demonstrating an improvement in muscle activation or increase in number of motor units recruited, a factor associated with muscle strain injuries. Peak EMG decreased possibly because muscle spindle afferent feedback increased resulting in improved efficiency of muscle contraction. By more fully activating the muscle, the participant appears to have greater control. The submaximal CON/ECC training may be beneficial in improving neural control and therefore in the prevention and treatment of muscle strain injuries. Underlying neural control mechanisms may be linked to muscle strains and improved prevention and rehabilitation.

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