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ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2019 March;59(3):357-65

DOI: 10.23736/S0022-4707.18.08281-6

Copyright © 2018 EDIZIONI MINERVA MEDICA

lingua: Inglese

Overnight fasting compromises exercise intensity and volume during sprint interval training but improves high-intensity aerobic endurance

Tasuku TERADA 1, Saeed R. TOGHI ESHGHI 2, Yilina LIUBAOERJIJIN 2, Michael KENNEDY 2, Étienne MYETTE-CÔTÉ 3, Kevin FLETCHER 2, Normand G. BOULÉ 2

1 Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada; 2 Faculty of Kinesiology, Sport and Recreation, 1-052 Li Ka Shing Center for Health Research Innovation, University of Alberta, Edmonton, Canada; 3 School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada



BACKGROUND: The combined effects of sprint interval training (SIT) and exercising in the fasted state are unknown. We compared the effects of SIT with exogenous carbohydrate supplementation (SIT-CHO) and SIT following overnight fast (SIT-Fast) on aerobic capacity (peak oxygen consumption: V̇O2peak) and high-intensity aerobic endurance (time-to-exhaustion at 85% V̇O2peak [T85%]).
METHODS: Twenty male cyclists were randomized to SIT-CHO and SIT-Fast. Both groups performed 30-second all-out cycling followed by 4-minute active recovery 3 times per week for 4 weeks, with the number of sprint bouts progressing from 4 to 7. Peak power output (PPO) and total mechanical work were measured for each sprint interval bout. The SIT-CHO group performed exercise sessions following breakfast and consumed carbohydrate drink during exercise, whereas the SIT-Fast group performed exercise sessions following overnight fast and consumed water during exercise. Before and after training, V̇O2peak and T85% were assessed. Blood glucose, non-esterified fatty acids, insulin and glucagon concentrations were measured during T85%.
RESULTS: Overall PPO and mechanical work were lower in SIT-Fast than SIT-CHO (3664.9 vs. 3871.7 J/kg; P=0.021 and 10.6 vs. 9.9 W/kg; P=0.010, respectively). Post-training V̇O2peak did not differ between groups. Baseline-adjusted post-training T85% was longer in SIT-Fast compared to SIT-CHO (19.7±3.0 vs. 16.6±3.0 minutes, ANCOVA P=0.038) despite no changes in circulating energy substrates or hormones.
CONCLUSIONS: Our results suggest that SIT-Fast compromises exercise intensity and volume but still can have a greater impact on the ability to sustain high-intensity aerobic endurance exercise compared to SIT-CHO.


KEY WORDS: Exercise - Athletic performance - Carbohydrate loading diet - Fasting

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