GIRLS ARE LESS SUSCEPTIBLE TO ECCENTRIC-TRAINING MUSCLE DAMAGE THAN ADULT WOMEN

Chen, T. C., Lin, M.-R., Ho, C.-C., Chen, H.-L., Tseng, K.-W., & Nosaka, K. (2016). Proprioception changes after eccentric exercise of the elbow flexors: comparison between children and adults. Medicine & Science in Sports & Exercise, 48(5), Supplement abstract number 687.

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"Significant impairment of proprioception such as position sense and joint-reaction angle was observed after the initial bout of unilateral eccentric exercise of the knee flexors, but the second of the same exercise performed three weeks later induced smaller changes in position sense and joint-reaction angle (Paschalis et al., EJAP 2008). Chen et al. (EJAP 2014) reported that the magnitude of muscle damage after unilateral eccentric exercise of the elbow flexors was smaller for children than adult men. However, no previous study has compared between children and adults for position sense and joint-reaction angle changes after eccentric exercise."

This study compared changes in several indirect markers of muscle damage and proprioception parameters after maximal elbow-flexor unilateral eccentric exercise between children and adult women, and between two unilateral eccentric exercise bouts (ECC1 and ECC2). Thirteen girls (9-10 years) and untrained young women (20-24 years) performed two bouts (separated by two weeks) of five sets of six elbow-flexor eccentric contractions by lowering a dumbbell (60% of pre-exercise maximal voluntary isometric contraction strength: MVC) with the non-dominant arm from an elbow flexed at 90 to a fully extended position. Changes in maximal voluntary isokinetic concentric contraction strength (MVC-CON), muscle soreness, plasma creatine kinase activity, position sense, and joint-reaction angle of the elbow were measured before, immediately after, and 1-5 days after each exercise.

Significant changes in all variables were found after eccentric exercise 1 for both groups, but the changes were significantly smaller for girls than adult women. Changes in all variables were smaller after eccentric exercise 2 than eccentric exercise 1 for both girls and adult women, and the changes were still smaller for children than adult women.

Implication. The magnitude of proprioception impairment was associated with the magnitude of muscle damage, and confirmed the previous study (Chen et al., 2014) that children were less susceptible to muscle damage than adults. The damage incurred by adults means they will have greater difficulty in adjusting established skills to accommodate the changes than will children.

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