Comparative Effects of Strengthening Exercise Modalities on Biochemical and Functional Outcomes in Duchenne Muscular Dystrophy

Abstract

Background: Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder characterized by declining muscle function and impaired physical performance. Exercise prescription in children with DMD requires careful consideration of the type and intensity of muscle loading. However, evidence regarding the comparative effects of different modes of strengthening exercise on metabolic and functional outcomes remains limited.
Objective: To compare the effects of concentric, isometric, and eccentric strengthening exercises on lipid profile, gait performance, and handgrip power in ambulatory children with DMD aged 6–10 years.
Methods: Eighty-three children with DMD were assessed for eligibility, of whom 23 were excluded according to the predefined eligibility criteria. Sixty children were randomly allocated equally to three intervention groups (n=20 each): concentric strengthening, isometric strengthening, and eccentric strengthening. The intervention was conducted for 3 months, three sessions per week, with each session lasting 40 minutes. The targeted muscles included the hip flexors and extensors, knee flexors and extensors, ankle dorsiflexors, wrist extensors, and finger flexors. Serum creatine kinase (CK), total cholesterol, triglycerides (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were assessed as biochemical outcomes. Functional outcomes included the 6-Minute Walk Test (6MWT) and maximal static power as a measure of handgrip power. Within-group changes were analyzed using the Wilcoxon signed-rank test, while differences in change scores among the three groups were assessed using the Friedman test.
Results: Significant pre-to-post changes were observed in the concentric group for CK (P=0.018), total cholesterol (P=0.009), TG (P=0.022), HDL (P=0.044), LDL (P=0.031), 6MWT (P=0.035), and muscle power (P=0.001). The isometric group demonstrated significant changes in CK (P=0.012), total cholesterol (P=0.023), HDL (P=0.043), LDL (P=0.025), 6MWT (P=0.001), and MSPOW (P=0.041), but not TG (P=0.146). The eccentric group demonstrated significant changes in TG (P=0.028), HDL (P=0.029), LDL (P=0.037), 6MWT (P=0.001), and muscle power (P=0.007), whereas changes in CK (P=0.754) and total cholesterol (P=0.099) were not significant. Friedman test analysis demonstrated significant differences among the three groups in change scores for CK (χ²=6.721, P=0.010), total cholesterol (χ²=13.091, P<0.001), TG (χ²=11.756, P=0.001), HDL (χ²=12.902, P<0.001), LDL (χ²=5.818, P=0.016), 6MWT (χ²=30.422, P<0.001), and muscle power (χ²=21.564, P<0.001).
Conclusion: Three months of concentric, isometric, or eccentric strengthening exercise were associated with significant changes in several lipid profile parameters, walking performance, and handgrip power in ambulatory children with DMD. The magnitude of pre-to-post change differed significantly among the three exercise modalities across all assessed outcomes. Further pairwise analysis is required to determine which specific exercise modalities differ from one another.