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-onse t GH deficiency (GHD). 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 mechani cal and metabolic measurements were taken. Methods: Oxygen consumption, and mechanical internal and external work of l ocomotion 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 s peeds, In walking, the relationships between both the mechanical energy rec overy and the metabolic cost with speed were shifted towards lower speeds i n 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. Str ide 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 h igher 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 diffe rent from those of healthy controls, thus demonstrating a substantial 'norm ality' in this group of GHD patients at metabolically attainable speeds, Th e '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 thos e with acquired GHD, taking into account the well recognized heterogeneity of the adult GHD syndrome.