Carbohydrate ingestion and exercise performance in the heat: Neuromuscular aspects of fatigue

Camila Nassif

Research output: ThesisDoctoral Thesis

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Abstract

Study One: Objective: The effect of carbohydrate (CHO) supplementation on endurance performance has been extensively studied but its placebo (PLA) effect can make the ergogenic qualities of CHO more difficult to determine. This study tested the effect of double blind ingestions of PLA and 6% CHO in capsules (c) and in a beverage (b) during a 60 km self-paced cycle time trial in the heat (32 oC and 50% relative humidity). Methods: Ten well trained male subjects (mean ± SD: 26 ± 3 years; 64.5 ± 7.7 kg and 70.7 ± 8.8 mL.kg-1.min-1 maximal oxygen consumption) completed 5 x 60km cycling time trials (TT) punctuated with 4 x 1 km sprints at 14, 29, 45 and 59 km. Trials consisted of 5 treatments, PLA in beverage (PLAb) and capsule (PLAc) form and CHO (CHOb and CHOc) in similar forms and a control water trial (H2O). Mean fluid volume ingested in each treatment was 284 ± 30 mL. Results: There were no differences in TT among treatments (H2O 138.2 min ± 17.5 min, PLAb 130.2 ± 11.2 min, CHOb 140.5 ± 18.1 min, PLAc 143.1 min ± 29.2 min, CHOc 137.3 ± 20.1 min). An increase in blood glucose was observed in the treatments where CHO was ingested compared with PLA and H2O treatment (p< 0.05). No differences in blood lactate were observed between treatments. There were no differences in power output, speed and cadence among treatments although these were different (p< 0.05) between the sprints and the low intensity periods of the trial for all treatments. No differences were observed in core and mean skin temperatures among treatments. Changes in electromyography were evident between sprints and low intensity efforts with muscle recruitment for PLAc and CHOc treatments being reduced in the latter stages of the trial (> 36.5 km). Conclusions: We conclude that CHO ingestion has no significant benefit in either capsule or beverage form over 60 km in the heat compared to either PLA or H2O.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Marino, Frank, Principal Supervisor
Award date01 Dec 2008
Place of PublicationAustralia
Publisher
Publication statusPublished - 2010

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