Maximal step-up height as a simple and relevant health indicator: a study of leg muscle strength and the associations to age, anthropometric variables, aerobic fitness and physical function.

Background Low muscle strength is related to an increased risk for several chronic diseases. Increased muscle strength improves daily function and quality of life. Objective To measure maximal step-up height, an assessment of leg strength and function, and its association to age, anthropometric variables, maximal oxygen uptake (VO2-max) and self-reported physical function before and after a physical activity programme. Methods Female patients (n=178, 22-83 years) with musculoskeletal disorders, metabolic risk factors and other chronic diseases were recruited from primary care. Maximal step-up height (standardised step-up without a kick-off with the floor foot), anthropometric variables, VO2-max and self-reported physical function (Short Form 36 (SF-36)) were assessed before and after a 3-month group training intervention programme. Associations between maximal step-up height and other variables were examined using univariate and multivariate methods. Results At baseline and after intervention, maximal step-up height was negatively correlated to age, waist circumference and body weight and positively correlated to VO2-max, self-reported physical function and height. Furthermore, maximal step-up height correlated to training intensity at follow-up. Variations in changes in maximal step-up height were significantly explained by changes in waist circumference and physical function, regardless of age and changes in VO2-max. Maximal step-up height below 24 cm discriminated patients with self-reported severe limitation in physical function. Conclusions Maximal step-up height, assessed simply with a standardised step-up test, may function as a relevant indicator of health since it correlated negatively to the metabolic risk factors, waist circumference, body weight and age, and positively to VO2-max and physical function.