The Effects of Sprint Training on Exercise Capacity, Growth Hormone and Body Composition

Abstract

Short-term, high-intensity exercise training has been shown to alter exercise capacity, growth hormone (GH) secretion and body composition. PURPOSE: To examine the effects of 3-weeks of sprint exercise training (SET) on a cycle ergometer on exercise capacity, growth hormone secretion and body composition. METHODS: Eight, recreationally active, male subjects (M ± SD) (age = 26.8 ± 4.3 yrs; height = 1.77 ± 0.05 m; weight= 77.8 ± 7.4 kg; lean body mass = 62.0 ± 7.1 kg) completed a 2-hour resting profile and a 2-hr acute sprint (AS) profile, followed by three weeks of SET with additional AS profiles at the end of each week. Blood samples were taken every 15 minutes [Q15] during rest and more frequently [Q1-Q10] during exercise. Cycling VO2max [TrueOne, ParvoMedics] and body composition [DXA; Prodigy Advanced, GE Lunar] were assessed pre and post training. SET consisted of 4-6 repetitions of 30-second maximal sprints relative to body mass, three times per week. Integrated 2 hr serum GH area under the curve (AUC) was calculated using trapezoidal integration. RESULTS: SET did not alter VO2max, but did result in increased total work during VO2max testing (M ± SD) (318±59 vs. 343±62 watts; P = <0.05), and peak power (PP) (7.5%; P < 0.05), while time to peak power (TTP) decreased 58.0 % (P < 0.05). GH AUC per unit lean body mass (LBM), did not change significantly (P = 0.82) during SET, although a trend was observed for it to decrease from the first AS to the second AS following the first week of SET (M ± SE) (8.45 ± 3.0 ng/ml vs. 3.59 ± 1.21 ng/ml, respectively; P = 0.90). Lean body mass pre vs. post training increased (M ± SD) (62.0 ± 7.1 vs. 62.9 ± 6.9 kg, respectively; P < 0.05), while body fat percent decreased (17.7 ± 4.8 vs. 16.8 ± 4.9%, respectively; P = <0.05). Despite these changes, total fat mass did not change. CONCLUSION: Although significant increases in PP were found, 3 weeks of SET did not significantly alter the GH AUC response to an AS. Additionally, 3 weeks of SET resulted in small alterations in body composition and improved anaerobic power output but not overall aerobic capacity.