High-Intensity Interval Exercise Test Stimulates Growth Hormone Secretion in Children

Background: Exercise stimulates growth hormone (GH) secretion and may serve as a promising physiological test for the diagnosis of GH deficiency. However, exercise standardization for a feasible GH test is still lacking. The aim of the present study was to examine the GH secretion to high intensity interval exercise.

Methods: Seventeen children (12.4 ± 2.6 years) with impaired growth rate performed a high-intensity interval exercise test (HIIE) that included 10 intervals of 15 s all-out pedaling against resistance determined by age, sex and weight on a cycle ergometer, with 1-min active rest between each interval. Power output measurements were collected during the test. Blood samples were collected before, immediately after, and 30, 45, and 60 min after the beginning of the exercise test. GH response was compared to pharmacological provocation test (clonidine or glucagon).

Results: HIIE led to a significant increase in GH levels (p= 0.001), with a high correlation to GH response following pharmacological stimulation (r = 0.82, r = 0.80 for clonidine and glucagon, respectively, p=0.001) A significant correlation was found between mean peak power to body weight and the GH response (r = 0.50, p = 0.04). 83% of the participants who reached peak power 10 watts/kg had normal GH secretion.

Conclusions: HIIE is a brief and individualized exercise protocol that may be used as a physiological provocation test for GH secretion. There might be a minimum of anaerobic power needed to induce adequate GH response during HIIE.