Abstract
Aerobic deconditioning, due to lower levels of physical activity, could impact independence for people with neuromuscular conditions. We report the maximal cardiopulmonary response in a cohort of people with Charcot Marie Tooth disease type 1A (CMT 1A) and inclusion body myositis (IBM). We also explored potential predictors of aerobic capacity with measures of physical impairment and functional performance. Participants underwent maximal cardiopulmonary exercise testing (CPET) using a semi-recumbent cycle ergometer. Data were analyzed to determine the peak O2 consumption (VO2 peak), anaerobic threshold (AT), maximum heart rate (MHR), ventilatory equivalent for CO2 slope (VE /VCO2 ), and respiratory exchange ratio (RER). Impairment, functional and patient reported measures were also recorded. Predicted CPET variables were calculated based on published normative data for age, gender, and weight. Twenty-two people with CMT and 17 people with IBM were recruited. Both groups showed significantly lower VO2 peak, MHR, AT, and VE /VCO2 . The CMT group overall performed better than the IBM group, with significantly higher VO2 peak, MHR, and AT, but lower VE /VCO2. Linear regression analysis demonstrated that VO2 peak was related to body fat percentage and 6-min walk distance for both groups, and steps per day for the IBM group. Lower than predicted CPET variables were observed that were not explained by cardiopulmonary limitations or reduced effort, implicating peripheral factors in limiting the cycling task. Regression analysis implied prediction of VO2 peak by body fat percentage and 6-min walk distance. Six-minute walk distance could be a potential proxy measure of cardiopulmonary fitness.
Highlights
People with neuromuscular diseases (NMDs) may be at increased risk of morbidities such as obesity, cardiovascular, and metabolic conditions,[1] because of lower levels of physical activity.[2,3] Insufficient physical activity is a major risk factor for the development of noncommunicable diseases, with an associated 20%–30% increased risk of all-cause mortality.[4]
The inclusion body myositis (IBM) group was older with a smaller proportion of females and slightly higher systolic blood pressure (SBP), but there were no other differences between disease groups in demographics and general health measures (Table 1)
In the IBM group, the same was true for all variables except for ventilatory equivalent for CO2 slope (VE/VCO2) slope
Summary
People with neuromuscular diseases (NMDs) may be at increased risk of morbidities such as obesity, cardiovascular, and metabolic conditions,[1] because of lower levels of physical activity.[2,3] Insufficient physical activity is a major risk factor for the development of noncommunicable diseases, with an associated 20%–30% increased risk of all-cause mortality.[4] Low aerobic capacity can negatively impact on independent community living. Aerobic de-conditioning and secondary disuse muscle atrophy are common in people with NMD and are a likely consequence of reduced general activity levels. Investigations of people with Charcot Marie Tooth disease (CMT) found they are less active than the general population[2,3,5] and are “de-conditioned,” as measured by oxygen uptake during exercise.[6] Similar reductions in aerobic capacity have been reported in people with idiopathic inflammatory myopathy,[7] but this has not been explored in inclusion body myositis (IBM)
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