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Caffeine ingestion and cycling power output in a low or normal muscle glycogen state
Lane, Suzanne Areta, José Bird, S Coffey, Vernon Burke, Louise Desbrow, B Karagounis, L Hawley, John A.
Lane, Suzanne
Areta, José
Bird, S
Coffey, Vernon
Burke, Louise
Desbrow, B
Karagounis, L
Hawley, John A.
Abstract
Purpose: Commencing selected workouts with low muscle glycogen availability augments several markers of training adaptation compared with undertaking the same sessions with normal glycogen content. However, low glycogen availability reduces the capacity to perform high-intensity (>85% of peak aerobic power (V·O2peak)) endurance exercise. We determined whether a low dose of caffeine could partially rescue the reduction in maximal self-selected power output observed when individuals commenced high-intensity interval training with low (LOW) compared with normal (NORM) glycogen availability.
Methods: Twelve endurance-trained cyclists/triathletes performed four experimental trials using a double-blind Latin square design. Muscle glycogen content was manipulated via exercise–diet interventions so that two experimental trials were commenced with LOW and two with NORM muscle glycogen availability. Sixty minutes before an experimental trial, subjects ingested a capsule containing anhydrous caffeine (CAFF, 3 mg-1·kg-1 body mass) or placebo (PLBO). Instantaneous power output was measured throughout high-intensity interval training (8 × 5-min bouts at maximum self-selected intensity with 1-min recovery).
Results: There were significant main effects for both preexercise glycogen content and caffeine ingestion on power output. LOW reduced power output by approximately 8% compared with NORM (P < 0.01), whereas caffeine increased power output by 2.8% and 3.5% for NORM and LOW, respectively, (P < 0.01).
Conclusion: We conclude that caffeine enhanced power output independently of muscle glycogen concentration but could not fully restore power output to levels commensurate with that when subjects commenced exercise with normal glycogen availability. However, the reported increase in power output does provide a likely performance benefit and may provide a means to further enhance the already augmented training response observed when selected sessions are commenced with reduced muscle glycogen availability.
Keywords
Date
2013
Type
Journal article
Journal
Medicine and Science in Sports and Exercise
Book
Volume
Issue
Page Range
1577-1584
Article Number
ACU Department
Centre for Exercise and Nutrition
Faculty of Health Sciences
Mary MacKillop Institute for Health Research
Faculty of Health Sciences
Mary MacKillop Institute for Health Research
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Open Access Status
License
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Controlled