Muscle Damage Not Evident in LOPD Patients After Resistance Exercise

Strength training exercises did not aggravate muscle damage in people with late-onset Pompe disease (LOPD), although patients with significant changes in certain markers of muscle damage should be monitored while determining their best training regime.

This result comes from the study “Muscle damage in response to a single bout of high intensity concentric exercise in patients with Pompe disease,” and published in the Annals of Translational Medicine.

LOPD stems from a lack of the acid alpha-glucosidase enzyme, resulting in a toxic buildup of glycogen within patients’ cells. The damage this does to cells causes gradual muscle weakness that eventually affects motor function and mobility.

Enzyme replacement therapy, the condition’s standard treatment, is considered efficient at stabilizing or improving strength and functional abilities, with physical therapy often prescribed as a supportive, or add-on measure.

Physical exercise can be broadly categorized as aerobic or resistance exercise, the latter better known as weight training. Although resistance exercise is an established way of developing strength of healthy individuals, there are concerns regarding its safety in LOPD.

Unaccustomed exercise typically causes muscle some damage — known as exercise-induced muscle damage (EIMD) — that is marked by heightened levels of creatine kinase, lactate dehydrogenase, and myoglobin, as well as muscle soreness and temporary strength loss. Studies indicate that EIMD is less severe when muscle contractions are performed concentrically, or in ways that cause muscle tension as muscles shorten (as with a bicep curl).

Limited data exist on how these markers change in response to resistance exercise in LOPD. Resistance exercises are generally not recommended for these people, but no evidence-based expert agreement exists on whether high-force resistance worsens muscle damage in LOPD patients.

Researchers at the University of Pécs, in Hungary, investigated how EIMD markers change in response to resistance exercises — repeat sets of concentric knee flexions with resistance — among LOPD patients.

Their study enrolled 12 adults with LOPD — five men and seven women, mean age of 42.8 — and 12 age- and sex-matched healthy controls. Each patient had been treated with Myozyme (alglucosidase alfa, marketed as Lumizyme in the U.S.) at a standard 20 mg/kg of body weight every two weeks for an average of four years.

Starting levels of all three blood biomarkers — creatine kinase, lactate dehydrogenase and myoglobin — were higher in patients than controls.

Levels of these markers increased significantly among the healthy controls at 24 hours post-exercise, before lowering. In contrast, only myoglobin levels rose among those with LOPD, remaining elevated at 48 hours after the exercise session.

These changes reflected total concentrations of each biomarker. When the investigators measured the change in biomarker levels relative to the amount of force each participant could exert, LOPD patients produced comparatively more lactate dehydrogenase.

Both groups reported increased muscle soreness 24 hours after exercising, which disappeared at 48 hours.

MRI showed increased water retention and blood perfusion in control participants’ muscles that could be related to greater muscle demand, whereas the investigators observed no statistically significant changes in those of the LOPD patients.

Overall, it appeared that resistance exercise increased patients’ strength over 24 hours, and that with the exception of lactate dehydrogenase, changes in EIMD markers were less severe among patients than controls.

Because of the relative change in lactate dehydrogenase, the researchers suggest that this biomarker should be monitored in a patient’s early phase of resistance exercise training, particularly if that person shows large changes in its levels. These levels may also help to determine the training effort and intensity needed to limit muscle damage among patients.

“In conclusion,” they wrote, “LOPD did not cause exacerbation of EIMD after a single bout of high intensity concentric exercise [knee flexions] compared to controls.”