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.