Effect of an eccentric exercise bout on concentric power of the shoulder.
Introduction: Eccentric exercise often results in decreases in
strength parameters such as concentric torque production. Previous
research has been limited to the effect of eccentric exercise on torque
production of the elbow flexor and knee extensor musculature. No known
research has focused on its effect on the shoulder musculature. Also, no
evidence showing the effect of eccentric exercise on concentric power of
any musculature has been found. Purpose: To determine the effect of an
eccentric bout of exercise on concentric power of the shoulder
musculature. Methods: Participants consisted of forty-one college-aged
students who were free of any shoulder pathologies. Participants were
randomly assigned to one of two groups, control (CON) (n=22), and
experimental (EXP) (n=19), with the experimental group undergoing a bout
of eccentric exercise between pre- and post-tests. Participants were
familiarized with the study protocol on the Biodex Isokinetic Dynamometer (Biodex, Inc., Shirley, NY) two days before testing. Day one
(D1) cons isted of a power spectrum analysis (PSA) consisting of five
repetitions of concentric internal rotation of the shoulder at each of
six speeds including 60, 120, 180, 210, 240, and 300 deg/sec. Mean and
peak torque (mT and pT) and mean and peak average power (mAP and pAP)
outputs were recorded for each of the six velocities. Day two (D2)
consisted of a bout of 50 repetitions of maximal eccentric activity of
the internal rotators for the experimental group followed immediately by
the PSA. Members of the control group simply underwent the PSA.
Analysis: Changes in criterion measures between groups, days and test
velocities (2x2x6) were measured with four separate repeated measures
ANOVAs. Wherever a significant main effect was present, a post hoc
analysis was used to detect difference in the measures. Results:
Contrary to the hypothesis, there were no significant changes
(p<0.05) in mT, pT, mAP, or pAP between groups. There were also no
significant differences (p<0.05) in any of the measures across days.
A significant main effect was present for velocities (p<0.05) for all
dependent variables. Discussion: Changes in torque and power production
after an eccentric bout may not be as apparent in the shoulder
musculature. Previous research focused on larger, more isolated muscle
groups such as the elbow flexors and knee extensors. Further research
must be conducted to determine the effects of eccentric activity on
concentric shoulder power.
Iveland, S., Noffal, G., Brown, L., Zinder, S., and Koob, R.
Movement Analysis Laboratory, Department of Kinesiology and Health
Science, California State University, Fullerton, CA