Previous studies suggest that the extensor carpi radialis brevis (ECRB) is the muscle most frequently affected in cases of lateral epicondylitis ("tennis elbow"). The purpose of this study was to compare the electromyographic (EMG) activity in two forearm muscles during two different backhand stroke techniques in tennis players with and without lateral epicondylitis. Twelve recreational tennis players (mean age, 47.2 ± 6.3 yrs), with USTA skill ratings between 3.0 and 5.0 participated in this study. Six subjects used a one-handed backhand, while six utilized a two-handed backhand; half the subjects in each technique group had lateral elbow pain from playing tennis. EMG data were collected at 1200 Hz from surface electrodes over the motor points of the ECRB and flexor carpi radialis (FCR) muscles of the dominant arm while subjects hit tennis balls using their preferred backhand stroke. Backhand strokes were divided into three phases: preparatory, acceleration, and follow-through, determined from video data. EMG data were normalized and expressed as a percentage of peak muscle activity in each trial. ANOVAs (technique x pain group x trials, () = 0.5) revealed that ECRB activity was significantly greater during the preparatory phase in players with elbow pain than in those without pain, but not significantly different between backhand techniques nor pain groups during acceleration and follow-through phases. FCR activity was greater for those with elbow pain during the acceleration and follow-through phases for both backhand strokes. FCR also exhibited a technique x pain group interaction, with the one-handed backhand with lateral elbow pain group having greater EMG activity than any other group. These results are in agreement with findings by Kelley et al. (1994) that previously injured muscles demonstrate increased EMG activity levels.
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