Influences of pain and strength on physical function and responses to elastic resistance in women with osteoarthritis
Hayes, Dawn Marie
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The leading cause of disability, arthritis, has led to 17.4 million US adults reporting arthritis-attributable activity limitations. Study I investigated leg strength as being a mediator between pain and physical function in older women diagnosed with OA. Thirty-five women (68.41 ± 5.1 years) completed Arthritis Impact Measurement Scales 2 (AIMS2) symptom scale, leg MVC, and Continuous Scale Physical Functional Performance-10 test (CS-PFP10). Regression analyses revealed that all conditions for mediation were satisfied: 1) pain affected physical function (Beta= -.35, p= .017), 2) pain affected MVC (Beta= -.35, p= .003), 3) MVC affected physical function after controlling for pain (Beta= .65, p= .002), and 4) the effect of pain on physical function became smaller and non-significant (Beta= -.12, p= .387) when both pain and MVC were included in the equation; concluding that improving physical function is directly accomplished by targeting muscular weakness. As evidenced by the literature and study one, continued investigation was warranted on elastic resistance training effects. Study II evaluated the effect of elastic resistance training (ERT) on leg MVC, CS-PFP10, self-reported physical function (SF36 PF), AIMS2 symptom, and depression symptoms (CES-D) compared to a wait list control (WLC). Thirty-one women (68 ± 5 years) were randomly assigned to WLC (n=17) or ERT (n=14) groups. The ERT group exercised 2 days/week for 16 weeks; WLC group maintained usual activity. One-way analysis of covariance was conducted. After controlling for baseline scores, post-test CS-PFP10 Total (Cohen’s d (ES) = .67) and leg MVC (ES = 1.3) were significantly greater in the ERT group. Depression symptoms (ES = .63) were significantly reduced for the ERT group. Post-test AIMS2 symptom (ES = .85) and SF36 PF (ES = .64) were not analyzed using ANCOVA due to homogeneity-of-slopes assumption not being met. An alternative analysis to ANCOVA was used, Johnson-Neyman (J-N) technique, which suggested that those women who scored ”58.6 on the SF36 PF and/or •4.6 on the AIMS2 symptom benefited more from the intervention. Elastic resistance training was more effective than a no treatment control for improving performance-based physical function and leg strength while reducing depression symptoms in older women with OA.