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Delaying consumption of a carbohydrate-rich breakfast does not impair afternoon intermittent exercise performance / CHRISTOPHER LAMB

Swansea University Author: CHRISTOPHER LAMB

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Abstract

Background: Omission of a carbohydrate-rich breakfast has been shown to impair afternoon/evening exercise performance, but previous studies have been limited by a lack of placebo control and the inclusion of complete omission of feeding until lunch, versus delaying the breakfast feeding. In this ran...

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Published: Swansea, Wales, UK 2024
Institution: Swansea University
Degree level: Master of Research
Degree name: MSc by Research
Supervisor: Metcalfe, Richard ; Waldron, Mark ; Love, Thomas
URI: https://cronfa.swan.ac.uk/Record/cronfa66962
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Abstract: Background: Omission of a carbohydrate-rich breakfast has been shown to impair afternoon/evening exercise performance, but previous studies have been limited by a lack of placebo control and the inclusion of complete omission of feeding until lunch, versus delaying the breakfast feeding. In this randomised, single-blind, placebo-controlled study, we hypothesised that introducing a placebo control would show no-difference to prolonged intermittent exercise performance in the afternoon versus consuming a high-carbohydrate breakfast. Methods: Ten regular intermittent games players completed two trials (EARLY and DELAY) that were matched for energy intake. In EARLY, participants consumed a high-carbohydrate breakfast shake (2 g·kg BM-1 maltodextrin, 1 ml·kg BM-1 orange squash, 0.15 g·kg BM-1 Xantham gum, 0.067 g·kg BM-1 artificial sweetener and 6 ml·kg BM-1 water) at 8am, followed by a taste and texture matched, but energy depleted, placebo (Identical minus Maltodextrin) at 10am. In DELAY the order of these shakes was reversed. In both trials, a standardised and individualised high carbohydrate lunch (888±107 Kcal, 145±28 g carbohydrate) was consumed at 12pm. Blood glucose and substrate oxidation measurements were conducted hourly throughout the day, and a subjective appetite rating taken after each meal. At 3pm, participants subsequently completed an 80-min intermittent exercise performance task, consisting of two, 40-min stages with 10-min of rest in between. Peak, mean, and end power output were measured during each sprint and averaged across each stage of the test for statistical analysis, with heart rate and RPE measured after each sprint. Results: The subjective appetite response followed a similar pattern during the morning of both trials, despite differing blood glucose and substrate oxidation results, which together confirmed the success of the single-blind placebo control. There were no differences in peak power (1st half: mean difference [95% CI]: 0.85 [-12 to 14] W, p=0.89, d=0.01); 2nd half: 1.6 [-12 to 15] W, p=0.79, d=0.01), mean power (1st half: mean difference: 2.2 [-12 to 17] W, p=0.73, d=0.01); 2nd half: mean difference: -2.2 [-16 to 11] W, p=0.72, d=0.02) or end power (1st half: mean difference: 6.9 [-11 to 25], p=0.42, d=0.05); 2nd half: mean difference: -1.7 [-16 to 12] W, p=0.80, d=0.01) in the DELAY compared to the EARLY condition. Conclusions: These data provide differing results to studies which focused on overt breakfast omission, rather than delaying breakfast using a placebo. This study provides preliminary suggestions that the results in other studies may likely be from a psychological, rather than physiological, mechanism.
Keywords: Exercise, Nutrition, Placebo, Performance, Physiology, Psychology
College: Faculty of Science and Engineering