British Journal of Sports Medicine 2009;43:521-525
Original articles
The role of lactate in the exercise-induced human growth hormone response: evidence from McArdle disease
1 Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, UK
2 School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
3 Centre of Exercise and Nutrition Science, University of Chester, Cheshire, UK
4 The Muscle Clinic, Robert Jones and Agnes Hunt Orthopaedic NHS Trust, Oswestry, UK
Dr Richard Godfrey, Centre for Sports Medicine and Human Performance, School of Sport and Education, Brunel University, Uxbridge, UB8 3PH, United Kingdom; richard.godfrey{at}brunel.ac.uk
Purpose: Increased blood lactate concentration has been suggested as a primary stimulus for the exercise-induced growth hormone response (EIGR). Patients with McArdle disease are unable to produce lactate in response to exercise and thus offer a unique model to assess the role of lactate in the EIGR. Accordingly, McArdle’s patients were exercised to test the hypothesis that lactate is a major stimulus of the EIGR.
Methods: 11 patients with McArdle disease (3 male, 8 female; age: 35.5 (SD 13.9) years, height: 166 (8) cm, body mass: 75.2 (13.1) kg) were recruited for the study. The patients walked initially at 0.42 m/s, increasing by 0.14 m/s per 3 min stage. Exercise was terminated when participants completed 3 minutes at 1.80 m/s or when a Borg CR10 pain scale rating of "4" was reached. Stages were separated by 60 s for capillary blood sampling for analysis of hGH and blood lactate concentration.
Results: McArdle’s patients’ blood lactate levels remained at resting levels (0.3–1.2 mmol/l) as exercise intensity increased. Nine out of 11 participants failed to demonstrate an EIGR obtaining hGH values below the clinical definition of a response (>3 µg/l).
Conclusion: The absence of an EIGR in nine out of 11 participants suggests that lactate could play a major role in the EIGR in humans.
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