Mechanical and metabolic profile of locomotion in adults with childhood-onset GH deficiency

Objective: The aim of the present study was to evaluate the energy cost and the mechanical work of locomotion in a group of adults with childhood- onset GH deficiency (GILD). Subjects: Eight males with childhood-onset GHD (mean age ± S.D.: 31.7 ± 3.6 years; mean height: 145.1 ± 6.7 cm) and six age-, sex- and exercise-matched normal subjects were studied. Design: GHD patients and healthy controls were requested to walk and run in the speed range of 2-11 km h-1. For each condition, simultaneous mechanical and metabolic measurements were taken. Methods: Oxygen consumption, and mechanical internal and external work of locomotion were evaluated with standard open-circuit respirometry and three-dimensional motion analysis respectively. Results: External work was not significantly different between GHD patients and healthy controls, while internal work was higher for patients at all speeds. In walking, the relationships between both the mechanical energy recovery and the metabolic cost with speed were shifted towards lower speeds in patients. As a consequence, the optimal speed of walking, i.e. the speed at which the cost of locomotion is minimum, was lower for GHD patients. Stride frequency was significantly higher (11.2-11.3%) for GHD patients at all speeds of walking and running. GHD patients were unable to run at speeds higher than 8 km h-1 for the time needed to reach a metabolic steady state. Conclusion: It appears that both the mechanics and energetics of locomotion in short-statured adults with childhood-onset GHD are not strikingly different from those of healthy controls, thus demonstrating a substantial 'normality' in this group of GHD patients at metabolically attainable speeds. The 'harmonic' body structure and the adherence to allometric transformations in these patients do not exclude the possibility of a different metabolic role of GH in normally statured adults with childhood-onset GHD and in those with acquired GHD, taking into account the well recognized heterogeneity of the adult GHD syndrome