Association of Muscle Strength and Walking Performance in Adult Patients With Pompe Disease

BACKGROUND: The loss of the ability to walk is among the most prominent signs of Pompe disease. The associations with muscle strength have not been described. OBJECTIVE: The objective of this study was to estimate the associations of walking performance with muscle strength in 4 specific lower extremity muscle groups along with other factors in adult patients with Pompe disease. DESIGN: This was a single-center, cross-sectional study. METHODS: Muscle strength (hand-held dynamometry of hip flexion and abduction and knee extension and flexion) and walking performance (unable to walk, able with aids, walking without aids but with a waddling gait, or walking without aids and with a normal gait) were assessed in 107 patients at their first visit. Relationships between walking performance and muscle strength were studied through multivariate analyses and regression modeling. Age, sex, body mass index (BMI), disease duration, and use of ventilator support were taken into account as potential confounders. The results were transformed into a nomogram to allow the probability of a patient having a certain level of walking performance to be calculated based on the values of the independent variables. RESULTS: Walking performance declined significantly with decreasing muscle strength of hip flexion and abduction and knee extension and flexion. The final selected model, including strength of the hip abductor and knee extensor, BMI, age, sex, and use of ventilation, predicted 66% of the cases accurately. LIMITATIONS: These results are based on cross-sectional data and do not predict future changes. CONCLUSIONS: In adult people with Pompe disease, walking performance can be explained by muscle strength, BMI, age, sex, and ventilation use. The proposed model gives insight into how an individual is expected to walk based on his or her risk factors and serves as a starting point to unraveling factors associated with walking performance and ultimately to developing a prognostic model.