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  • Author: Mark D. Haub x
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Richard R. Rosenkranz, Chad M. Cook and Mark D. Haub

Purpose:

To illustrate the effects of low-carbohydrate (LC) and grain-based (GB) diets on body composition, biomarkers, athletic training, and performance in an elite triathlete.

Methods:

The athlete followed 2 dietary interventions for 14 d while maintaining a prescheduled training program. Pre- and post intervention measurements for each diet included plasma and serum samples, resting energy expenditure, body composition, and a performance bike ride.

Results:

Compared with the GB diet, the LC diet elicited more disruptions to training and unfavorable subjective experiences. Total cholesterol, HDL cholesterol, LDL cholesterol, ratings of perceived exertion, and heart rate were elevated on the LC diet. Blood insulin, resting lactate, post exercise lactate, and C-reactive protein were lowest on the LC diet.

Conclusion:

The LC diet resulted in both favorable and unfavorable outcomes. The primary observation was a disruption to scheduled training on the LC diet. Researchers should consider how the potential mediating effect of disruptions to training could influence pretest–posttest designs.

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Mark D. Haub, Jeffrey A. Potteiger, Dennis J. Jacobsen, Karen L. Nau, Lawrence A. Magee and Matthew J. Comeau

We investigated the effects of carbohydrate ingestion on glycogen replenishment and subsequent short duration, high intensity exercise performance. During Session 1, aerobic power was determined and each subject (N = 6) was familiarized with the 100-kJ cycling test (lOOKJ-Test). During the treatment sessions, the subjects performed a lOOKJ-Test (Ride-1), then consumed 0.7 g ⋅ kg body mass-1 of maltodextrin (CHO) or placebo (PLC), rested 60 min, and then performed a second lOOKJ-Test (Ride-2). Muscle tissue was collected before (Pre-1) and after Ride-1 (Post-1), and before (Pre-2) and after Ride-2 (Post-2), and analyzed for glycogen concentration. Both treatments yielded a significant increase in glycogen levels following the 60-min recovery, but there was no difference between treatments. Time to complete the lOOKJ-Test increased significantly for PLC, but not for CHO. These data indicate that the decrease in performance during Ride-2 in PLC was not the result of a difference in glycogen concentration.