Reilly, T., & Woodbridge, V. (1999). Effects of moderate dietary manipulations on swim performance and on blood lactate-swimming velocity curves. International Journal of Sports Medicine, 20, 93-97.

This study examined the effects of dietary manipulations on both swim performance and on the relationship between blood lactate and swimming velocity. The first study engaged Ss (N = 8) in a regimen to reduce muscle glycogen by a combination of diet and training. Ss were monitored under a normal mixed diet comprising ~54% carbohydrate (carbohydrate) and under a decreased carbohydrate condition (~40% carbohydrate) over 3 days.

Mean swim performance worsened significantly over 400 yards after carbohydrate reduction.

The second study employed Ss (N = 7) in a regimen to enhance muscle glycogen stores. Ss were monitored over three days under a normal diet (~53% carbohydrate) and on a separate occasion under an increased carbohydrate intake (~59% carbohydrate). Mean swimming performance improved over 100 yards and 400 yards under the augmented carbohydrate condition.

Only minor non-significant changes in lactate responses were observed in both studies illustrating the limitations of applying lactate response curves to swim training.

Implication. A moderate reduction in carbohydrate intake alters swimming performance adversely whereas a moderate elevation in carbohydrate intake above the normal diet level improves performance.

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