Contribution of Solid Food to Achieve Individual Nutritional Requirement during a Continuous 438 km Mountain Ultramarathon in Female Athlete

Abstract

Background: Races and competitions over 100 miles have recently increased. Limited information exists about the effect of multiday continuous endurance exercise on blood glucose control and appropriate intake of food and drink in a female athlete. The present study aimed to examine the variation of blood glucose control and its relationship with nutritional intake and running performance in a professional female athlete during a 155.7 h ultramarathon race with little sleep.

Methods: We divided the mountain course of 438 km into 33 segments by timing gates and continuously monitored the participant's glucose profile throughout the ultramarathon. The running speed in each segment was standardized to the scheduled required time-based on three trial runs. Concurrently, the accompanying runners recorded the participant's food and drink intake. Nutrient, energy, and water intake were then calculated.

Results: Throughout the ultramarathon of 155.7 h, including 16.0 h of rest and sleep, diurnal variation had almost disappeared with the overall increase in blood glucose levels (25-30 mg/dL) compared with that during resting (p < 0.0001). Plasma total protein and triglyceride levels were decreased after the ultramarathon. The intake of protein and fat directly or indirectly contributed to maintaining blood glucose levels and running speed as substrates for gluconeogenesis or as alternative sources of energy when the carbohydrate intake was at a lower recommended limit. The higher amounts of nutrient intakes from solid foods correlated with a higher running pace compared with those from liquids and gels to supply carbohydrates, protein, and fat.

Conclusion: Carbohydrate, protein, and fat intake from solid foods contributed to maintaining a fast pace with a steady, mild rise in blood glucose levels compared with liquids and gels when female runner completed a multiday continuous ultramarathon with little sleep.

Keywords: Freestyle Libre; carbohydrate; continuous glucose monitoring; hydration; protein; sports nutrition; trail running.

Figure 1

Blood glucose fluctuation during the 7-day ultramarathon. Each solid line represents the daily glucose variation (A). Scatter plot of blood glucose during a preliminary, ultramarathon, and post-ultramarathon periods, respectively (B). Scatter plot of blood glucose levels during night (dark) and day (light) throughout the ultramarathon (C). Histogram of blood glucose fluctuation during preliminary, ultramarathon (night and day), and post-ultramarathon periods (D). *** p < 0.001, **** p < 0.0001 The differences between dark and light were compared by the Mann–Whitney test, and those among pre, ultramarathon post were compared by the Kruskal–Wallis nonparametric ANOVA, followed by Dunn’s multiple comparison test.

Figure 2

Scatter plots showing the relationships between nutrient intake and blood glucose level. The intake of energy (A), carbohydrate (B), protein (C), fat (D), water (E), and salt (F) was calculated according to the consumed food and fluid products. Each plot indicates one segment.

Figure 3

Relationship between the running pace and the highest blood glucose level, lowest blood glucose level, and delta (difference between the highest and lowest blood glucose levels) between segments. The pace was calculated from the difference between the estimated running time and actual running time of the segment, as described in the Methods section. Briefly, the pace value was positive when the runner ran faster than the estimated running time and negative when the runner ran slower.

Figure 4

Scatter plots showing the relationships between nutrient intake and running pace. The intake of energy (A), carbohydrate (B), protein (C), fat (D), water (E), and salt (F) was calculated according to the nutrition information of the consumed food and fluid products. Each plot indicates one segment.

Figure 5

Comparison of energy (A), carbohydrate (B), protein (C), fat (D), water (E), and salt (F) intake among different running paces (fast, when the running pace was faster than planned; on time, when the running pace was the same as planned; slow, when the running pace was slower than planned). * p < 0.05 and ** p < 0.01 between fast and slow, Mann–Whitney test. The horizontal bar represents the median in each group.

Figure 6

Comparison of product type for energy (A), carbohydrate (B), protein (C), fat (D), water (E), and salt (F) consumption among different running paces (fast, when the running pace was faster than planned; on time, when the running pace was the same as planned; slow, when the running pace was slower than planned). * p < 0.05, ** p < 0.01, *** p < 0.001 between fast and slow, Mann–Whitney test. Values are means ± SEM.