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The metabolic response to squash including the influence of pre-exercise carbohydrate ingestion.

1982; National Institutes of Health; Volume: 62; Issue: 20 Linguagem: Inglês

Timothy D. Noakes, Jane Cowling, Wieland Gevers, J P de V van Niekerk,

Diet and metabolism studies

Serum glucose, free fatty acid, insulin and growth hormone values, blood lactate levels and changes in body weight and rectal temperature were measured in 6 squash players during two separate 90-minute matches, one of which started 25 minutes after the players had ingested 67 g carbohydrate. Serum glucose, growth hormone and blood lactate levels rose during both matches, reaching peak values after 45 minutes, whereas serum free fatty acid levels rose progressively and insulin levels fell. The mean weight loss was 2 kg and the mean post-match rectal temperature was 39 degrees C. Pre-exercise carbohydrate ingestion caused serum insulin and growth hormone concentrations to be significantly higher during the first half of the match. Glucose and free fatty acid levels were lower, but not significantly so, during exercise after carbohydrate ingestion. Neither weight loss nor rectal temperature ws influenced by pre-exercise carbohydrate feeding. We conclude that the thermal and metabolic response to squash is similar to that to moderate-intensity running and is characterized by hyperthermia, hyperglycaemia, elevated free fatty acid and growth hormone levels and low blood lactate and serum insulin values. In these players pre-exercise carbohydrate feeding did not produce adverse metabolic effects, possibly because the players had enhanced glucose tolerance, characterized by a diminished insulin response to ingested carbohydrate. This is likely to be associated with a high degree of endurance adaptation. Nevertheless, the lower serum glucose and free fatty acid levels indicate that pre-exercise carbohydrate feeding impairs the normal metabolic response to squash and may adversely affect performance, particularly in poorly trained players. Players should therefore be discouraged from ingesting high-carbohydrate foods or drinks shortly before playing squash or taking part in other similar activities.