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Nutrients 2016, 8(10), 639; doi:10.3390/nu8100639

Time of Day and Training Status Both Impact the Efficacy of Caffeine for Short Duration Cycling Performance

1
Human Performance Lab, Department of Kinesiology, James Madison University, Harrisonburg, VA 22807, USA
2
Department of Chemistry, James Madison University, Harrisonburg, VA 22807, USA
*
Author to whom correspondence should be addressed.
Received: 26 August 2016 / Revised: 6 October 2016 / Accepted: 7 October 2016 / Published: 14 October 2016
(This article belongs to the Special Issue Nutrition, Health and Athletic Performance)
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Abstract

This project was designed to assess the effects of time of day and training status on the benefits of caffeine supplementation for cycling performance. Twenty male subjects (Age, 25 years; Peak oxygen consumption, 57 mL·kg−1·min−1) were divided into tertiles based on training levels, with top and bottom tertiles designated as ‘trained’ (n = 7) and ‘untrained’ (n = 7). Subjects completed two familiarization trials and four experimental trials consisting of a computer-simulated 3-km cycling time trial (TT). The trials were performed in randomized order for each combination of time of day (morning and evening) and treatment (6mg/kg of caffeine or placebo). Magnitude-based inferences were used to evaluate all treatment effects. For all subjects, caffeine enhanced TT performance in the morning (2.3% ± 1.7%, ‘very likely’) and evening (1.4% ± 1.1%, ‘likely’). Both untrained and trained subjects improved performance with caffeine supplementation in the morning (5.5% ± 4.3%, ‘likely’; 1.0% ± 1.7%, ‘likely’, respectively), but only untrained subjects rode faster in the evening (2.9% ± 2.6%, ‘likely’). Altogether, our observations indicate that trained athletes are more likely to derive ergogenic effects from caffeine in the morning than the evening. Further, untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts. View Full-Text
Keywords: exercise time of day; caffeine supplementation; training history; diurnal; training status exercise time of day; caffeine supplementation; training history; diurnal; training status
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MDPI and ACS Style

Boyett, J.C.; Giersch, G.E.W.; Womack, C.J.; Saunders, M.J.; Hughey, C.A.; Daley, H.M.; Luden, N.D. Time of Day and Training Status Both Impact the Efficacy of Caffeine for Short Duration Cycling Performance. Nutrients 2016, 8, 639.

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