Exercise Intolerance in Facioscapulohumeral Muscular Dystrophy.

Area of Science:

• Neurology
• Exercise Physiology
• Muscular Dystrophy Research

Background:

• Facioscapulohumeral muscular dystrophy (FSHD) is a progressive genetic disorder affecting skeletal muscles.
• Exercise intolerance is a common but not fully understood symptom in adults with FSHD.
• Understanding the physiological mechanisms behind exercise intolerance is crucial for managing FSHD.

Purpose of the Study:

• To determine if adults with FSHD exhibit exercise intolerance compared to healthy controls.
• To investigate potential contributing factors to exercise intolerance in FSHD, focusing on physiological mechanisms.
• To correlate objective exercise capacity measures with patient-reported functional limitations.

Main Methods:

• A comparative study involving eleven adults with FSHD and eleven age- and sex-matched healthy controls.
• Maximal incremental cycling exercise tests were performed to measure peak oxygen consumption (V̇O2peak) and other physiological responses.
• Body composition, including lean mass (LM), was assessed using dual-energy x-ray absorptiometry.

Main Results:

• Individuals with FSHD demonstrated significantly lower V̇O2peak (32% lower) and peak wattage (55% lower) compared to controls.
• At submaximal exercise intensities, FSHD patients achieved lower wattage but reported similar exertion and dyspnea.
• At absolute workload, FSHD patients experienced significantly higher perceived exertion and dyspnea.
• V̇O2peak in FSHD was strongly correlated with leg lean mass and self-reported functional limitations (FSHD-HI score).

Conclusions:

• Disease-driven loss of lean mass is a primary contributor to exercise intolerance in FSHD.
• Reduced V̇O2peak and increased symptoms of dyspnea and fatigue during exercise are characteristic of FSHD.
• Maintaining or preserving lean mass through regular exercise may offer protection against exercise intolerance in individuals with FSHD.