Background: Inclusion Body Myositis (IBM) is a rare, progressive inflammatory myopathy with limited treatment options. Strength and balance exercises may help preserve muscle strength and physical function, but evidence in IBM is limited.

Objectives: To evaluate pre–post changes in physical function, patient-reported outcomes, and physical activity after a 16-week strength and balance program in IBM, and to explore the impact of adherence on outcomes.

Methods: Fifteen patients with IBM participated in a 16-week intervention consisting of one weekly supervised group-based session at Oslo University Hospital and one home-based session per week, both including strength and balance exercises. Physical function was assessed using the Manual Muscle Test-8 (MMT-8), grip strength, 30-second sit-to-stand test, Functional Index-3 (FI-3), 2-minute walk test (2MWT), and Berg Balance Scale. Patient-reported outcomes (PROMs) included the Inclusion Body Myositis Functional Rating Scale (IBMFRS), Health Assessment Questionnaire (HAQ), Patient-Specific Functional Scale (PSFS), and International Physical Activity Questionnaire (IPAQ). Pre- and post-intervention scores were compared using Wilcoxon signed-rank tests.

Results: Of the 15 included patients, thirteen patients completed the intervention. Two patients withdrew after baseline assessments due to back pain and transportation challenges. The median age was 71.7 years (IQR 66.8–72.9), and 54% were male. Statistically significant improvements were observed in grip strength, with the right hand increasing from median 22.0 lbs (IQR 19.0–32.3) to 23.7 lbs (20.2–34.2) ( p = 0.004), and the left hand from 16.7 lbs (11.4–25.5) to 19.0 lbs (14.0–32.4) ( p = 0.003). The number of repetitions in the 30-second sit-to-stand test increased from 8.0 (0.0–11.0) to 9.0 (2.0–13.5) ( p = 0.004). Participants also reported a significant increase in moderate-to-vigorous physical activity, from 100 minutes per week (53–440) to 225 minutes (110–585) ( p = 0.02). Additionally, walking time increased from 60 minutes per week (IQR 5–260) to 210 minutes (54–420) ( p = 0.06), and time spent sitting decreased from 600 minutes per day (450–750) to 420 minutes (315–720) ( p = 0.07). Other outcomes, including MMT-8, FI-3, 2MWT and Berg Balance Scale, remained unchanged or showed trends toward improvement without reaching statistical significance. PROMs such as IBMFRS, HAQ, and PSFS showed minimal changes. A per-protocol analysis was conducted, including only participants with satisfactory adherence to the exercise program (10/13). The results were largely consistent with the primary analysis: hand grip strength in both hands and 30-second sit-to-stand performance remained significantly improved. However, while MVPA no longer reached statistical significance (p=0.07), walking time now showed a significant increase (p=0.04), and sedentary time demonstrated a significant reduction (p=0.02). These findings indicate that adherence to the program may have had a meaningful impact on physical activity outcomes.

Conclusions: The exercise intervention was associated with statistically significant improvements in grip strength, lower limb function, and physical activity levels. However, some of the observed changes were small and may be influenced by measurement variability. The per-protocol analysis further highlighted significant reductions in sedentary time and increases in walking time, suggesting that adherence may influence some outcomes, particularly activity-related measures. Trends toward increased walking time and reduced sedentary behavior suggest potential benefits of individualized strength and balance training for patients with IBM, but further research is needed to confirm clinical relevance.

REFERENCES: NIL.

Acknowledgments: NIL.

Disclosure of Interests: None declared.