Ultra-endurance athletes accumulate an energy deficit throughout their events and those competing in self-sufficient multi-stage races are particularly vulnerable due to load carriage considerations. Whilst urinary ketones have previously been noted in ultra-endurance exercise and attributed to insufficient carbohydrate (CHO) availability, not all studies have reported concomitant CHO intake. Our aim was to determine changes in blood glucose and β-hydroxybutyrate concentrations over five days (240 km) of a self-sufficient multi-stage ultramarathon in combination with quantification of energy and macronutrient intakes, estimated energy expenditure and evaluation of energy balance. Thirteen runners (8 male, 5 female, mean age 40 ± 8 years) participated in the study. Glucose and β-hydroxybutyrate were measured every day immediately post-running, and food diaries completed daily. CHO intakes of 301 ± 106 g·day-1 (4.3 ± 1.8 g·kg-1·day^-1) were not sufficient to avoid ketosis (5-day mean β-hydroxybutyrate: 1.1 ± 0.6 mmol.L^-1). Furthermore, ketosis was not attenuated even when CHO intake was high (9 g·kg^-1·day^-1). This suggests that competing in a state of ketosis may be inevitable during multi-stage events where load reduction is prioritised over energy provisions. Attenuating negative impacts associated with such a metabolic shift in athletes unaccustomed to CHO and energy restriction requires further exploration.

Item Type:	Refereed Article
Keywords:	ketosis, carbohydrate, endurance, ultra-endurance, nutrition
Research Division:	Health Sciences
Research Group:	Sports science and exercise
Research Field:	Exercise physiology
Objective Division:	Health
Objective Group:	Other health
Objective Field:	Other health not elsewhere classified
UTAS Author:	Kitic, CM (Dr Cecilia Kitic)
ID Code:	136382
Year Published:	2019
Web of Science® Times Cited:	2
Deposited By:	Health Sciences
Deposited On:	2019-12-17
Last Modified:	2020-05-13
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