Torque Steadiness Measurements of the Shoulder in Normal Subjects and Subjects with Shoulder Pain

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Presentation given at American Physical Therapy Association-Combined Sections Meeting. Purpose/Hypothesis: Physical therapists frequently treat patients with shoulder related pathologies using isometric exercise. There’s limited research on torque steadiness, or in maintaining submax isometric contraction(SIC), in subjects with or without shoulder pain. The purpose of this study was to investigate nonpainful subjects’ torque steadiness at a submax level of muscle intensity compared to subjects with shoulder pain. We hypothesized subjects with shoulder pain would have less accuracy with submax torque steadiness and produce less torque than those without pain.

Number of Subjects: 20

Materials and Methods: Ten subjects from painful and nonpainful groups, were matched by body mass index, sex, and history of overhead sports. Subjects were screened with the Visual Analogue Scale, Disabilities of Arm Shoulder or Hand Questionnaire, and 2 of 4 positive shoulder impingement tests. Subjects were excluded if they had surgery to an upper extremity (UE) within the past year. All subjects underwent randomization, and a UE warm up. Positions included shoulder glenohumeral joint (GH) in 30 degrees abduction, scaption, and diagonal movement; or GH joint in 90 degrees abduction and external rotation. Subjects performed 3 max volitional isometric contractions (MVIC); followed by 60% of the MVIC in GH internal rotation (IR)/external rotation (ER) at mid-range of motion.

Results: Data analysis conducted via SPSS Version 25. An independent-samples t-test was run to determine a difference in root mean square error (RMSE), and coefficient of variation (CV), between groups. A Welch t-test was run for deviation (SD) variation between groups. A Mann-Whitney U test was run to compare median MVIC values between groups. Results show no statistical significant difference(SSD) (p>.05) for RMSE, SD, CV, or median MVIC between groups. RMSE was lower in painful subjects (1.02 ± .30) than nonpainful (1.27 ± .52), but not a SSD with a difference of -.25 (95% CI, -.65 to .14), t(18) = -1.35, p=.19, d=.60. CV was lower in painful subjects (4.85 ± 1.34) than nonpainful (5.17 ± 1.70), and not a SSD of -.32 (95% CI, -1.75 to 1.12), t(18) = -.47, p=.65, d=.21. SD was lower in painful subjects (.64 ± .15) compared to nonpainful (.83 ±.47), but not a SSD with a difference of -.19 (95% CI, -.54 to .15), t(10.8) = -1.23, p=.25. No Cohen’s d effect size was calculated for SD due to violation of homogeneity of variances. Median MVIC for painful (22.24) and nonpainful (23.20) was not a SSD, U = 45, z = -.38, p = .74, using an exact sampling distribution for U.

Conclusions:The hypotheses were unsupported with no SSD between groups. These results indicate subjects with painful shoulders are not limited in their MVIC or in SIC ability, compared to without pain.These results may determine whether to use SIC in shoulder pain patients.

Clinical Relevance: Results demonstrate SICs with torque steadiness may be effective in a rehabilitation program with subjects having shoulder pain because they can maintain the time under tension in a controlled manner. This may help with strengthening and decreasing pain.


Physical Therapy Association-Combined Sections Meeting


Denver, CO

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