Training program-induced skeletal muscle adaptations in two men with myotonic dystrophy type 1

Area of Science:

• Exercise physiology
• Skeletal muscle biology
• Myotonic dystrophy type 1 research

Background:

• Myotonic dystrophy type 1 (DM1) is a genetic disorder affecting skeletal muscle.
• Understanding exercise-induced adaptations in DM1 patients is crucial for management.
• Previous research on exercise interventions in DM1 is limited.

Purpose of the Study:

• To investigate skeletal muscle adaptations in response to a training program in individuals with DM1.
• To evaluate changes in muscle strength, myofiber characteristics, and markers of muscle growth.
• To explore the relationship between training adherence and muscle adaptations.

Main Methods:

• Two male patients with DM1 participated in a 12-week strength/endurance training program (18 sessions).
• Muscle biopsies were collected pre- and post-training to analyze myofiber cross-sectional area (CSA) and type proportion.
• Indirect markers of muscle growth, including centrally nucleated fibers (CNF) and immune cell density, were assessed.

Main Results:

• Significant muscular adaptations, including increased CSA of type I and II myofibers and altered proportion, were observed in the patient with 72% training attendance.
• No significant changes in muscle strength, CNF percentage, or neutrophil/macrophage density were noted.
• The patient with 39% attendance showed no notable adaptations.

Conclusions:

• Skeletal muscle cells in DM1 patients retain the capacity for exercise-induced adaptations related to muscle growth.
• Training adherence appears to be a critical factor influencing the extent of these adaptations.
• Further research with larger cohorts is warranted to confirm these findings.