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Mahmoud S. El-Sayed, Angelheart J.M. Rattu and Ian Roberts

The study examined the effect of carbohydrate ingestion on exercise performance capacity. Nine male cyclists performed two separate trials at 70% VO2max for 60 min followed by a maximal ride for 10 min. During trials subjects were fed either an 8% glucose solution (CHO) or a placebo solution (PL), which were administered at rest and during and immediately after submaximal exercise. Statistical analyses indicated that glucose levels at rest increased significantly 15 min after the ingestion of CHO compared to PL. At 30 and 60 min during submaximal exercise, plasma glucose levels decreased significantly in the CHO but not in the PL trial. Following the performance ride, glucose levels increased significantly only during the CHO test trial. Free fatty acids did not change significantly during testing trials. The maximal performance ride results showed that in the CHO trial, a significantly greater external work load was accomplished compared to the PL trial. It is concluded that CHO ingestion improves maximal exercise performance after prolonged exercise.

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Jason T. Penry and Melinda M. Manore

Choline plays a central role in many physiological pathways, including neurotransmitter synthesis (acetylcholine), cell-membrane signaling (phospholipids), lipid transport (lipoproteins), and methyl-group metabolism (homocysteine reduction). Endurance exercise might stress several of these pathways, increasing the demand for choline as a metabolic substrate. This review examines the current literature linking endurance exercise and choline demand in the human body. Also reviewed are the mechanisms by which exercise might affect blood choline levels, and the links between methyl metabolism and the availability of free choline are highlighted. Finally, the ability of oral choline supplements to augment endurance performance is assessed. Most individuals consume adequate amounts of choline, although there is evidence that current recommendations might be insufficient for some adult men. Only strenuous and prolonged physical activity appears sufficient to significantly decrease circulating choline stores. Moreover, oral choline supplementation might only increase endurance performance in activities that reduce circulating choline levels below normal.

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Anthony C. Hackney, Mary Ann McCracken-Compton and Barbara Ainsworth

This study examined substrate metabolism responses of eumenorrheic women to different intensities of submaximai exercise at the midfollicular (MF) and the midluteal (ML) phases of the menstrual cycle. Nine women performed a 30-min treadmill run in which the exercise intensity was made more difficult every 10 min (35%, 60%, and 75%). Carbohydrate (CHO) utilization and oxidation rates for the 35% and 60% intensities during the ML session were significantly lower than during the comparable intensities in the MF. Conversely, lipid utilization and oxidation were significantly greater during the 35% and 60% ML session than in the MF session. At 75%, however, the ML and MF CHO-lipid utilization and oxidation rates were not significantly different from one another. Thus, the phase of the menstrual cycle in eumenorrheic women does influence metabolic substrate usage during low- to moderate-intensity submaximai exercise, probably due to changes in the endogenous levels of the female sex hormones.

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Justin H. Rigby and Austin M. Hagan

oxidative species, and a decrease in metabolic substrates including ATP, creatine phosphate, and glycogen. 17 During the repeated bouts of a fatigue task, we assumed our participants suffered from these physiological effects of fatigue. After a controlled fatigue task, approximately 30% of participants who

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Peter Ibbott, Nick Ball, Marijke Welvaert and Kevin G. Thompson

compromise between limiting the development of neuromuscular fatigue, replenishment of metabolic substrates, and the available time in which training can be conducted. 11 , 13 – 15 Sets of repetitions are generally completed as closed-loop events. During the interset rest periods, athletes have time to

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Sigridur L. Gudmundsdottir

that increased intraindividual variability in sleep in adults is associated with blunted diurnal cortisol slopes and lower levels of waking cortisol ( 3 , 38 ). As cortisol secretion in response to exercise will increase the availability of metabolic substrates during activity and recovery ( 1 ), the