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Grip strength exercises may mediate effects of SARAH on hand function
In patients with rheumatoid arthritis who undertake the strengthening and stretching for rheumatoid arthritis of the hand exercise program, exercises aimed at improving grip strength are important components of the exercise program and mediate its effects, according to recent findings.
Investigators conducted a two-arm, randomized controlled trial of 488 patients with rheumatoid arthritis. Eligible participants were either not on disease-modifying antirheumatic drugs (DMARDs) or had been on a stable DMARD regimen for the previous 3 months. Patients were randomized to receive usual care (n= 246) or usual care plus the strengthening and stretching for rheumatoid arthritis of the hand (SARAH) exercise program (n=242). The mean age was 61.3 ± 12 years in the intervention group and 63.5 ±11 years in the control group.
Researchers evaluated treatment outcomes, as well as potential mediating variables at baseline (T0), and at 4 months (T1) and 12 months (T2) post-randomization. The primary outcome was hand function as evaluated by the Michigan Hand Outcomes Questionnaire (MHQ) overall hand function subscale score.
Proposed mediating variables consisted of factors for which the SARAH exercise program was designed, including: wrist flexion and wrist extension, measured from the neutral position with a goniometer; finger flexion; finger extension; thumb opposition; dexterity; and full hand grip strength and tripod pinch strength. Researchers used structural equivalent modeling to determine mediation on change in hand function via change in possible mediators.
The trial had a follow-up rate of 92% at 4 months’ follow-up and 89% at 12 months for the MHQ, and a significant treatment effect was identified in assessing this outcome.
In analyzing the potential mediators, the researchers found the following mean changes at 4 months:
- full hand grip in usual care group, 7.98 N vs. exercise group, 16.43 N;
- pinch grip force in usual care group, 2.91 N vs. exercise group 4.05 N;
- combined finger flexion in usual care group, 3.48 mm vs. exercise group 4.48 mm;
- combined finger extension in usual care group, 1.34 mm vs. exercise group, 4 mm;
- active wrist extension score in usual care, 1.35° vs. exercise group, 1.50°;
- active wrist flexion score in usual care, 1.30° vs. 3.34°;
- thumb apposition score in usual care, 0.17 vs. exercise group, 0.23; and
- dexterity in usual care group, 0.74 vs. exercise group, 1.08.
Of these positive effects conferred by the intervention on all mediators, only the effect on grip strength reached statistical significance.
The following effect size estimates were seen between grip strength at 4 months and hand function at 12 months: total effect size, 4.35; direct effect size, 3.50; indirect effect size, 0.85; and proportion mediated, 19%.
“This study provides initial evidence that strength training components are active ingredients that contribute to the effectiveness of the SARAH exercise program,” the researchers wrote. “As the role of mobility exercises remains unclear, it is reasonable to continue to recommend the use of the SARAH intervention as per the proposed protocol, including both strength and mobility exercises in combination with behavioral strategies.” — by Jennifer Byrne
Disclosure: The researchers report no relevant disclosures.