Conclusions
Collectively, these changes may contribute to an increase in reaction time, which may affect risk for recurrent symptoms. These findings suggest that therapists may need to address both strength and rapid force development deficits in patients with LE. Level of evidence: 3B.
Methods
Twenty-eight participants with LE (13 unilateral and 15 bilateral LE) and 13 healthy controls participated in this study. A multiaxis profile dynamometer was used to evaluate grip strength and rapid grip force generation. The ability to rapidly produce force is composed of the electromechanical delay and rate of force development. Electromechanical delay is defined as the time between the onset of electrical activity and the onset of muscle force production. The Patient-rated Tennis Elbow Evaluation (PRTEE) questionnaire was used to assess pain and functional disability. Magnetic resonance imaging was used to evaluate tendon degeneration.
Results
LE-injured upper extremities had lower rate of force development (50 lb/sec, confidence interval [CI]: 17, 84) and less grip strength (7.8 lb, CI: 3.3, 12.4) than nonnjured extremities. Participants in the LE group had a longer electromechanical delay (- 59% , CI: 29, 97) than controls. Peak rate of force development had a higher correlation (r = 0.56; p<0.05) with PRTEE function than grip strength (r = 0.47; p<0.05) and electromechanical delay (r = 0.30; p>0.05) for participants with LE. In addition to a reduction in grip strength, those with LE had a reduction in rate of force development and an increase in electromechanical delay. Conclusions: Collectively, these changes may contribute to an increase in reaction time, which may affect risk for recurrent symptoms. These findings suggest that therapists may need to address both strength and rapid force development deficits in patients with LE. Level of evidence: 3B.