Effect of elbow joint angle on the magnitude of muscle damage to the elbow flexors.
OBJECTIVE
It has been shown that eccentric actions at a long muscle length result in a larger decrease in force and more muscle tenderness compared with those at a short muscle length. To further investigate the effect of elbow joint angle on the development of muscle damage, this study compared two maximal eccentric exercise regimens in which the starting position of the action was different, but the range of movement was the same.


METHODS
One arm of 10 male students performed 24 maximal eccentric actions of the elbow flexors at the elbow joint angle from 0.87 to 2.27 rad (50-130 degrees: S condition) and the other arm at the elbow joint angle from 1.74 to 3.14 rad (100-180 degrees: L condition). Maximal isometric force, range of motion, muscle soreness, plasma creatine kinase activity, upper arm circumference, and B-mode ultrasound pictures of the elbow flexors (US) were measured before and for 5 d postexercise in both conditions. Magnetic resonance imaging (MRI) of the transverse scans of the upper arm was taken at 4 d after exercise.


RESULTS
All measures changed significantly (P < 0.01) after exercise for both conditions; however, significantly (P < 0.01) larger changes in the measures were found in the L condition compared with the S condition. MRI and US displayed that only the brachialis was damaged for the S condition but the biceps brachii was also damaged for the L condition.


CONCLUSIONS
The greater development of muscle damage in the L condition compared with the S condition is likely to be associated with the elbow flexors muscles affected by the exercise.
Nosaka
K
K
Exercise and Sports Science, Department of Environmental Science, Yokohama City University, Japan. nosaka@yokohama-cu.ac.jp
Sakamoto
K
K
D000328:Adult; D003402:Creatine Kinase / Q000097:blood; D004551:Elbow Joint / Q000002:abnormalities; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000002:abnormalities / Q000293:injuries*; D014481:United States; D014891:Weight Lifting / Q000293:injuries*; D000092464:Elbow Injuries
D003402:Creatine Kinase