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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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CAFFEINE ATTENUATES ACUTE GROWTH HORMONE RESPONSE TO A SINGLE BOUT OF RESISTANCE EXERCISE |
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Bo-Han Wu1 
and Jung-Chang Lin2 |
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1Department of Sports & Recreation Management, Chang Jung Christian University, Tainan, Taiwan, 2Graduate Institute Sport Coaching Science, Chinese Culture University, Taipei, Taiwan |
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© Journal of Sports Science and Medicine (2010) 9, 262 - 269 |
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| ABSTRACT | |||
| The purpose of this study was to investigate the effects of caffeine
consume on substrate metabolism and acute hormonal responses to a single
bout of resistance exercise (RE). Ten resistance-trained men participated
in this study. All subjects performed one repetition maximum (1RM) test
and then performed two protocols: caffeine (CAF, 6 mg·kg-1) and control
(CON) in counter balanced order. Subjects performed RE (8 exercises, 3 sets
of 10 repetitions at 75% of 1RM) after caffeine or placebo ingestion one
hour prior to RE. Blood samples collected prior to treatment ingestion (pre-60),
immediately prior to RE (pre-exe), and 0, 15, 30 min post to RE (P0, P15,
P30) for analysis of insulin, testosterone, cortisol, growth hormone, glucose,
free fatty acid and lactic acid. Each experiment was separated by seven
days. In this study, statistical analysis of a two-way analysis of variance
(treatment by time) with repeated measures was applied. After ingesting
caffeine, the concentrations of free fatty acid (pre- exe, P0, P15, P30)
in CAF were significantly higher than CON (p < 0.05). Additionally, the
responses of GH (P0, P15, P30) in CAF were significantly lower than CON
(p < 0.05), whereas the concentrations of insulin, testosterone and cortisol
were not different between CAF and CON (p < 0.05) after RE. The results
of this study indicated that caffeine ingestion prior to RE might attenuate
the response of GH. This effect might be caused by the elevation in blood
FFA concentration at the beginning of RE.
Key words: Nutritional supplementation, growth hormone, free fatty acid, ergogenic aids. |
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