Isokinetic Testing Effects of Various Positions and Velocities on Two Novel Functional Unilateral Shoulder Ratios
Presentation given at American Physical Therapy Association-Combined Sections Meeting.
Purpose/Hypothesis: There is limited information on shoulder muscle concentric (CON) and eccentric (ECC) unilateral isokinetic ratios at different testing positions and velocities, particularly the ratios between internal (IR) and external (ER) rotators CON/ECC muscle performance, which are more representative of functional activities. The purpose was to compare two mixed unilateral ER/IR shoulder rotation muscle ratios (CON/ECC, ECC/CON) between two testing positions (30°abduction-30°-scaption-30°diagonal motion and 90°abduction-90°elbow flexion), and two velocities (60°/s and 180°/s), and to determine sex related differences. We hypothesized the CON/ECC ratio would show the largest difference whereas the ECC/CON ratio would show the smallest difference at the 90°-90°position at 60°/s, with the effects being greater for males.
Number of Subjects: 50 (25♀)
Materials and Methods: Subjects participated in 2 testing sessions (7-10 day interval) for each testing position. Sessions began with a 5 minute upper body ergometer warmup and shoulder stretches, followed by Biodex isokinetic testing of shoulder IR and ER at 2 velocities. Testing position and velocity order were randomized. The 2 unilateral ratios were computed for each testing position and velocity and statistically analyzed with a position by velocity by sex repeated measures analysis of variance (α=.05).
Results: For the CON/ECC, post hoc analysis of a significant velocity by sex interaction (P=.015, η2p = .117) demonstrated the males to have a significantly (P=.004, d=.76) higher ratio than the females at 180°/s, while there was no significant difference (P=.195, d=.32) between the males and females at 60°/s. For both males (P<.001, d=.94) and females (P=.002, d=.27), the ratios were significantly less for 180°/s compared to 60°/s with the difference being significantly greater for males (P=.015, d=.72).
For the ECC/CON, the 30°-30°-30° position ratio was significantly less (P<.001, d=.47) than the 90°-90° position, the 60°/s ratio was significantly less (P<.001, d=.74) than 180°/s, and the male ratio was significantly less than the female (P=.005, d=.68).
Conclusions: The activities in which recreationally active males participate may commonly involve upper extremity utilization to a greater extent than recreationally active females, thereby explaining the greater ECC/CON ratio difference between testing velocities. The force-velocity relationship likely explains the ratio changes between velocities for CON/ECC (ratio decrease) and ECC/CON (ratio increase). The higher ratios in the 90-90 for both ECC/CON and CON/ECC may be explained by the position elongating the muscle fibers of the rotator cuff muscles, allowing for greater force production.
Clinical Relevance: The results may be valuable in screening, reassessment, and criteria for discharge back to activity for individuals who have shoulder-related problems.
Physical Therapy Association-Combined Sections Meeting
Abell, Hayley K., Hannah Lawson, Alyssa Martinek, Bradley Seuntjens, Bryan L. Riemann, George J. Davies.
"Isokinetic Testing Effects of Various Positions and Velocities on Two Novel Functional Unilateral Shoulder Ratios."
Health and Kinesiology Faculty Presentations.