BACKGROUND:In Pompe disease, resistance exercise could be an effective treatment to delay motor function impairment, however, the acute effects of this exercise modality are unclear.METHODS:In a prospective cohort study, we compared responses to a single bout of resistance exercise by serum markers of muscle damage and quantitative muscle magnetic resonance imaging (MRI) in patients (n=12) and age- and gender-matched healthy controls (n=12). Participants performed 50 maximal effort concentric knee flexions on a dynamometer.RESULTS:Twenty-four hours after exercise, levels of serum creatine kinase, lactate dehydrogenase and myoglobin increased in controls. In contrast, only myoglobin level increased in patients. All elevated serum markers declined by 48 hours after exercise in both groups. Mild soreness developed at 24 hours, which disappeared at 48 hours in both groups. In controls, MRI R2* relaxation rate reduced immediately and 24 hours after exercise, indicating increased water content and muscle perfusion. In patients, exercise had no effect on R2* values. The resistance exercise did not induce acute strength deficit in patients, rather, patients increased their strength by 24 hours. When serum marker changes were normalized to the magnitude of knee flexor tension developed during exercise, lactate dehydrogenase response was greater in patients.CONCLUSIONS:Late-onset Pompe disease did not exacerbate exercise-induced muscle damage, however, lactate dehydrogenase may be monitored to screen high responders during high intensity resistance exercise interventions.

Introduction: Both resistance and stretch-shortening cycle exercise have positive effects on physical abilities and health related factors. In the present experiment we tested the hypothesis that an 8-week-long combined strength and stretch-shortening cycle exercise training is superior to strength training alone in the development of walking and running economy in healthy untrained women. Methods: Twenty untrained female college students (age = 21.5 +/- 2.1 years, body mass index = 22.3 +/- 2.9) were divided into two experimental groups. Both groups performed own-body resistance exercises three times per week but one group performed additional stretch-shortening cycle exercises. Countermovement jump force as well as maximal voluntary isometric torque and elastic energy storage and re-use in quadriceps muscle were measured. Running and walking economy was quantified by measuring maximal oxygen consumption during a treadmill test. Results: Isometric torque improved uniformly in the two groups (p < 0.05), however countermovement jump force, elastic energy storage and re-use as well as running economy improved selectively after strength and additional stretch-shortening cycle exercise (p < 0.05). Walking economy was unaffected in either of the experimental groups. Conclusion: This study suggests that improved elastic energy storage and re-use rather than maximum muscle contractility may account for the changes in countermovement jump force and running economy after additional stretch-shortening cycle exercise. The present data should be taken into consideration for understanding the favourable effects of stretch-shortening cycle exercise training in the young untrained population.