Myotonic Dystrophy Type 1 and Resistance Exercise (STYRK DM1)

Oslo University Hospital, University of Southern Denmark, University of Copenhagen, Maastricht University, University of Oslo

The purpose of this study is to investigate the response after one bout of moderate-heavy resistance exercise in patients suffering from Myotonic Dystrophy type 1. There is still doubt about if these patients could benefit from resistance exercise, or if this mode of exercise is detrimental to their mobility and health. We aim to monitor the subjects during the recovery phase and investigate recovery in several ways.

Myotonic dystrophy type 1 (DM1) is an autosomal, dominantly inherited, muscular disease and the most common muscular dystrophy amongst adults. The disease is characterized by progressive myopathy and myotonia, first evident in the distal parts of the body: calves and forearms, further progressing towards proximal parts. A recent review by Voet and co-workers (2013) concludes that exercise is safe for DM1-patients, and based on our current knowledge, DM1-patients should be able to gain positive adaptations from exercise. However, the physiological outcomes of an exercise stimulus are not well studied in this population and because of alterations in important Ca2+ handling systems the recovery processes might be significantly different from healthy muscles. The aim of this study is to investigate the acute responses to moderate-heavy resistance exercise in DM1-patients. We aim to establish a timeline for recovery of muscle strength, measured as maximal voluntary contraction. In line with this, we want to investigate if any muscular damage has occurred with both direct and indirect measures, and possible mechanisms leading to muscle damage, i.e. impaired Ca2+ handling.

Participants in both groups (patients and control) perform unilateral leg resistance exercise, contralateral leg serves as control

Leg press: 3 x 8 repetitions at 75% of 1 repetition maximum, 3 minutes rest between sets. Knee extension: 3 x 6 repetitions at 85% of 1 repetition maximum, 3 minutes rest between sets.

Rate of muscle protein synthesis in m. vastus lateralis between baseline and 27 hours after final session of resistance exercise

Rate of muscle protein breakdown in m. vastus lateralis between baseline and 27 hours after final session of resistance exercise

Myofibrillar disruption and necrosis observed in muscle tissue samples from m. vastus lateralis with electron microscopy

Appearance of macrophages, satellite cell localization, and disruption of membrane in single muscle fibers and cross-sections using confocal microscopy

Expression and phosphorylation status of central mediators in anabolic signaling pathways using Western blotting

Expression and phosphorylation status of central mediators in pathways regulating muscle protein breakdown using Western blotting

Inclusion Criteria: Confirmed Myotonic Dystrophy type 1-diagnosis Exclusion Criteria: Non-ambulatory Injuries to muscle-skeletal-system that prevents resistance exercise Severe affection of the cardiovascular system Cognitive affection Lives more than one hour from test site