title: Intensity of eccentric exercise, shift of optimum angle, and the magnitude of repeated-bout effect.
abstract: This study compared the effect of four different intensities of initial eccentric exercise (ECC1) on optimum angle shift and extent of muscle damage induced by subsequent maximal eccentric exercise. Fifty-two male students were placed into 100%, 80%, 60%, or 40% groups (n = 13 per group), performing 30 eccentric actions of the elbow flexors of 100%, 80%, 60%, or 40% of maximal isometric strength [maximal voluntary contraction (MVC)] for ECC1, followed 2-3 wk later by a similar exercise (ECC2) that used 100% MVC load. MVC at six elbow joint angles, range of motion, upper arm circumference, serum creatine kinase activity, myoglobin concentration, and muscle soreness were measured before and for 5 days following ECC1 and ECC2. A rightward shift of optimum angle following ECC1 was significantly (P < 0.05) greater for the 100% and 80% than for the 60% and 40% groups, and it decreased significantly (P < 0.05) from immediately to 5 days postexercise. By the time ECC2 was performed, only the 100% group kept a significant shift (4 degrees). Changes in most of the criterion measures following ECC1 were significantly greater for the 100% and 80% groups compared with the 60% and 40% groups. Changes in the criterion measures following ECC2 were significantly (P < 0.05) greater for the 40% group compared with other groups. Although the magnitude of repeated bout effect following ECC2 was significantly (P < 0.05) smaller for the 40% and 60% groups, all groups showed significantly (P < 0.05) reduced changes in criterion measures following ECC2 compared with the ECC1 100% bout. We conclude that the repeated-bout effect was not dependent on the shift of optimum angle.
authors.affiliation: Department of Physical Education, National Chiayi University, Taiwan.
authors.forename: Trevor C
authors.initials: TC
authors.lastname: Chen
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
authors.forename: Paul
authors.initials: P
authors.lastname: Sacco
mesh_terms: D000293:Adolescent; D000328:Adult; D003402:Creatine Kinase / Q000097:blood; D004551:Elbow Joint / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D009124:Muscle Proteins / Q000097:blood; D053580:Muscle Strength / Q000502:physiology*; D009211:Myoglobin / Q000097:blood; D016059:Range of Motion, Articular / Q000502:physiology
chemical_list: D009124:Muscle Proteins; D009211:Myoglobin; D003402:Creatine Kinase