Respiratory and upper limb function as outcome measures in ambulant and non-ambulant subjects with Duchenne muscular dystrophy: A prospective multicentre study.

The field of translational research in Duchenne muscular dystrophy (DMD) has been transformed in the last decade by a number of therapeutic targets, mostly studied in ambulant patients. A paucity of studies focus on measures that capture the non-ambulant stage of the disease, and the transition between the ambulant and non-ambulant phase. In this prospective natural history study, we report the results of a comprehensive assessment of respiratory, upper limb function and upper limb muscle strength in a group of 89 DMD boys followed in 3 European countries, 81 receiving corticosteroids, spanning a wide age range (5-18 years) and functional abilities, from ambulant (n = 60) to non-ambulant (n = 29). Respiratory decline could be detected in the early ambulatory phase using Peak Expiratory Flow percentage predicted (PEF%), despite glucocorticoid use (mean annual decline: 4.08, 95% CI [-7.44,-0.72], p = 0.02 in ambulant; 4.81, 95% CI [-6.79,-2.82], p < 0.001 in non-ambulant). FVC% captured disease progression in non-ambulant DMD subjects, with an annual loss of 5.47% (95% CI [-6.48,-4.45], p < 0.001). Upper limb function measured with the Performance of Upper Limb (PUL 1.2) showed an annual loss of 4.13 points (95% CI [-4.79,3.47], p < 0.001) in the non-ambulant cohort. Measures of upper limb strength (MyoGrip and MyoPinch) showed a continuous decline independent of the ambulatory status, when reported as percentage predicted (grip force -5.51%, 95% CI [-6.54,-4.48], p < 0.001 in ambulant and a slower decline -2.86%; 95% CI -3.29,-2.43, p < 0.001, in non-ambulant; pinch force: -2.66%, 95% CI [-3.82,-1.51], p < 0.001 in ambulant and -2.23%, 95% CI [-2.92,-1.53], p < 0.001 in non-ambulant). Furthermore, we also explored the novel concept of a composite endpoint by combining respiratory, upper limb function and force domains: we were able to identify clear clinical progression in patients in whom an isolated measurement of only one of these domains failed to appreciate the yearly change. Our study contributes to the field of natural history of DMD, linking the ambulant and non-ambulant phases of the disease, and suggests that composite scores should be explored further.

Self-efficacy and the stages of exercise behavior change.

This study examined the application of constructs concerning stage of readiness to change and self-efficacy to exercise. We developed two scales to measure stages of change for exercise behavior. Prevalence information on a sample of 1,063 government employees and 429 hospital employees was then obtained. Next, the ability of a questionnaire measuring exercise self-efficacy to differentiate employees according to stage of readiness to change was tested. Results from both stages-of-change scales revealed that 34-39% of employees were regularly participating in physical activity. Scores on efficacy items significantly differentiated employees at most stages. Results indicated employees who had not yet begun to exercise, in contrast with those who exercised regularly, had little confidence in their ability to exercise. Continued work at understanding the stages of exercise behavior and exercise self-efficacy could yield important information for enhancing exercise adoption and adherence.

The stages and processes of exercise adoption and maintenance in a worksite sample.

We applied the model of the stages and processes of change to exercise adoption and maintenance. This model has shown promise in advancing theory and treatment of the addictions and other negative health behaviors, but there have been few systematic attempts to apply the model to positive health behaviors, such as exercise adoption. Questionnaires dealing with the stages and processes of exercise change were developed and administered to a sample of 1,172 participants in a worksite health promotion project. The sample was split randomly into halves for (a) initial model development and testing and (b) confirmatory measurement model testing. Additional model confirmation was obtained by examining the hierarchical structure of the processes of change and by conducting Stage x Process analyses. Results suggest that the underlying constructs derived from smoking cessation and other addictive behaviors can be generalized to exercise behavior. Understanding the stages and processes of exercise behavior change may yield important information for enhancing exercise adoption, adherence, and relapse prevention at both individual and public health levels.