Growth hormone regulation of muscle function: Role of the anaerobic energy system (#117)
Growth hormone (GH) regulates muscle function such as strength and aerobic fitness. It has recently been reported that GH improves sprinting (1), a performance activity dependent on anaerobic glycolysis, suggesting stimulation of anaerobic energy production by GH in muscle. The effect and physiological significance of GH on the anaerobic energy system are unknown.
To investigate the regulation of the anaerobic energy system in muscle by GH and its functional significance.
Nine adults with GH deficiency (GHD) and 10 age- and body mass index (BMI)-matched normal subjects were compared. Anaerobic capacity was assessed by the Wingate test and aerobic capacity by the VO2max test. The functional significance of anaerobic capacity was assessed by the stair-climb test, chair-stand test and 7-day pedometry. Group comparison was performed using unpaired t-test and relationships between performance and functional tests were analyzed by linear regression.
Mean CVs for performance and functional tests in 6 healthy volunteers ranged from 3-11% with corresponding intra-class correlation >0.9. In the GHD group, mean anaerobic capacity (3.7±0.3 vs. 4.9±0.4 watts/kg, p=0.02) and VO2max (23.5±1.3 vs. 33±2.2 ml/kg/min, p=0.002) were significantly lower than the normal group. These measures were lower in women than in men. The mean duration for the completion of the stair-climb test was longer (19±0.8 vs15.2±0.6 seconds, p<0.001) in the GHD group and correlated with mean anaerobic capacity. In a multivariate analysis after correcting for age, gender and BMI, GH status significantly (p< 0.05) predicted anaerobic capacity and VO2max. Anaerobic capacity but not VO2max significantly (p< 0.004) predicted stair-climb performance.
Anaerobic capacity, VO2max and stair-climb performance are reduced in GH deficiency. Anaerobic capacity independently predicts stair-climb performance.
GH regulates the anaerobic energy system, which plays an important role in functional activities of daily living such as climbing stairs.
Supported by the Princess Alexandra Research Support Scheme.
- Meinhardt U, Nelson AE, Hansen JL, Birzniece V, Clifford D, Leung KC, Graham K, Ho KKY Ann Intern Med. 2010;152(9):568-77.