Abstract
Carbohydrate (CHO) intake recommendations for events lasting longer than 3h indicate that athletes should ingest up to 90g.h.−1 of multiple transportable carbohydrates (MTC). We examined the dietary intake of amateur (males: n=11, females: n=7) ultra-endurance runners (mean age and mass 41.5±5.1years and 75.8±11.7kg) prior to, and during a 24-h ultra-endurance event. Heart rate and interstitial glucose concentration (indwelling sensor) were also tracked throughout the event. Pre-race diet (each 24 over 48h) was recorded via weighed intake and included the pre-race meal (1–4h pre-race). In-race diet (24h event) was recorded continuously, in-field, by the research team. Analysis revealed that runners did not meet the majority of CHO intake recommendations. CHO intake over 24–48h pre-race was lower than recommended (4.0±1.4g·kg−1; 42±9% of total energy), although pre-race meal CHO intake was within recommended levels (1.5±0.7g·kg−1). In-race CHO intake was only in the 30–60g·h−1 range (mean intake 33±12g·h−1) with suboptimal amounts of multiple transportable CHO consumed. Exercise intensity was low to moderate (mean 68%HRmax 45%VO2max) meaning that there would still be an absolute requirement for CHO to perform optimally in this ultra-event. Indeed, strong to moderate positive correlations were observed between distance covered and both CHO and energy intake in each of the three diet periods studied. Independent t-tests showed significantly different distances achieved by runners consuming ≥5 vs. <5g·kg−1 CHO in pre-race diet [98.5±18.7miles (158.5±30.1km) vs. 78.0±13.5miles (125.5±21.7km), p=0.04] and ≥40 vs. <40g·h−1 CHO in-race [92.2±13.9miles (148.4±22.4km) vs. 74.7±13.5miles (120.2±21.7km), p=0.02]. Pre-race CHO intake was positively associated with ultra-running experience, but no association was found between ultra-running experience and race distance. No association was observed between mean interstitial glucose and dietary intake, or with race distance. Further research should explore approaches to meeting pre-race dietary CHO intake as well as investigating strategies to boost in-race intake of multiple transportable CHO sources. In 24-h ultra-runners, studies examining the performance enhancing benefits of getting closer to meeting pre-race and in-race carbohydrate recommendations are required.
Highlights
Ultra-endurance running presents the athlete with a substantial nutritional challenge
Ten of the participants continued moving for the full 24-h, six stopped to sleep, and two were unable to continue
The sub-set of participants (n = 7) who wore heart rate monitor (HRM)/GPS devices throughout the event exercised at a mean intensity of 68 ± 5% HRmax, equating to approximately 45 ± 17% VO2max. (Table 1), representing low to moderate intensity exercise
Summary
Ultra-endurance running presents the athlete with a substantial nutritional challenge. Intakes of 8–12 g·kg−1 CHO per 24-h are recommended in the 36–48 h leading up to a prolonged endurance event to ensure well stocked muscle glycogen, with a further 1–4 g·kg−1 in a pre-race meal during the final 1–4 h recommended to top up liver glycogen stores (Thomas et al, 2016; Costa et al, 2019a). Recommendations for endurance activities lasting >2.5–3 h, are to consume up to 90 g·h−1 of multiple transportable carbohydrates (MTC; Burke et al, 2011). This amount can prove challenging in ultra-endurance running events (Costa et al, 2019a,b) higher intakes of 120 g·h−1 are possible and reduced exercise-induced muscle damage, in elite mountain-marathon runners (Viribay et al, 2020)
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