ECSS Paris 2023: OP-PN09
INTRODUCTION: Ultra-running is in the midst of a carbohydrate (CHO) revolution. Anecdotal reports by ultra-runners suggest CHO ingestion at 120 g/h significantly enhances performance compared to the current recommended dose of 90 g/h. However, CHO dose-response studies have yet to establish a performance advantage of 120 g/h over 90 g/h. This is the first study to evaluate the effects of ingesting 120 g/h vs 90 g/h of CHO on ultra-running performance, heart rate, rating of perceived exertion (RPE), blood glucose, blood lactate, and gastrointestinal distress in ultra-runners during a mountain trail ultra-marathon. METHODS: 28 male (n=18) and female (n=10) ultra-runners were recruited, however only 10 males completed the study. On two occasions, separated by 21 days, participants completed three 17.7 km loops of a simulated 53 km mountain trail race with 2,500m of vertical elevation. Participants were blinded to dose, taking either 90 or 120 g/h (maltodextrin: fructose ratio 1:0.8) in a randomised crossover design. CHO were provided as gels and drinks, consumed in 30 or 40 g doses every 20 minutes throughout the race. Race times were recorded at the end of each loop and at three separate checkpoints within each loop. RPE, gastrointestinal (GI) symptoms, blood lactate and glucose were collected pre-race and at the end of each loop, while heart rate was monitored throughout the study. RESULTS: There were no significant differences for total race completion time (p = 0.80), loop time (p = 0.80), or segment times (p = 0.79) between 90 and 120 g/h conditions. No significant differences were reported between conditions for GI symptoms during loop 1 (p = 0.98) and loop 2 (p = 0.87). GI symptoms steadily increased during loop 3 and were significantly greater in the 120 compared to the 90 g/h condition (16.8 vs 7.5; p = 0.035). During loop 3, upper GI symptoms accounted for 63% of all reported issues, which were significantly higher for the 120 g/h condition (9.0 vs 3.8; p = 0.013). Blood lactate did not change significantly with duration (p = 0.11). Blood glucose (p = 0.001), heart rate (p <0.0001), %VO2max (p <0.0001), and RPE (p <0.0001) all increased significantly with duration. There were no significant differences in these variables between conditions, except blood glucose and RPE, which were significantly higher in the 120 g/h condition during loop 3 (6.91 vs 6.20 mmol/l; p = 0.04 and 15.5 vs 14.5; p = 0.003, respectively). CONCLUSION: This is the first study to report that ingesting carbohydrates at a dose of 120 g/h does not improve performance during a 53 km mountain trail ultra-marathon compared with 90 g/h. This is despite an increase in upper gastrointestinal symptoms and perceived exertion during the final stage of the race whilst consuming 120 g/h of carbohydrates. Therefore, ultra-runners competing in trail races up to 50 km are recommended to follow current carbohydrate recommendations at 90 g/h, to avoid unnecessary gastrointestinal stress.
Read CV Paul BoothECSS Paris 2023: OP-PN09
INTRODUCTION: Prediabetes is a transitional state between normal glucose levels and diabetes. Excess body weight, accompanied by dyslipidemia, can exacerbate insulin resistance, accelerating the progression from prediabetes to diabetes. Lifestyle interventions involving exercise and diet during the prediabetes stage demonstrate effectiveness in weight management, improving lipid profiles, and reducing diabetes development rates. High-intensity interval exercise (HIIE) is a time-efficient strategy to improve metabolic health, whereas a low-carbohydrate diet (LCD) has demonstrated efficacy in improving lipid levels among diabetic patients. However, their efficacy in improving lipid profiles in prediabetic populations remains limited. Therefore, identifying feasible and effective lifestyle interventions that promote prediabetes health management is of major clinical relevance. This pilot study aimed to investigate the effect of HIIE combined with LCD for physically inactive adults with prediabetes. METHODS: This study was a 12-week pilot randomized trial. Thirty adults aged 40 to 64 years with prediabetes were randomly allocated to the following groups: HIIE group (performing home-based HIIE 3 times/week), LCD group (targeting carbohydrate intake at least 10% but less than 26% of total calories), or combined group (COM, combined HIIE and LCD intervention). Body composition, such as body weight (BW), body fat, and waist circumference (WC) were assessed at baseline and after 12 weeks of intervention. In addition, lipid profiles, such as total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides, were assessed by venous blood after 8 hours of fasting. Generalized estimating equations analyses were used to assess the treatment of the interventions. Statistical significance was defined as a two-sided p-value < 0.05. RESULTS: No significant group-by-time interaction effect was observed for BW (p = 0.059). However, a significant main effect of time was found in BW (p < 0.001) and WC (p < 0.001), indicating that the reduction of BW and WC occurred over time across all three groups. A group-by-time interaction effect was found for body fat percentage (p = 0.029). The COM group showed a larger reduction than the HIIE group (mean difference [95% confidence intervals]: -2.45% [-3.96, -0.95], p = 0.001) and the LCD group (-1.68% [-3.12, -0.24], p = 0.023). No significant time-by-group effect was observed for TC (p = 0.858) and LDL-C (p = 0.651). A significant time effect was found in HDL-C (p <0.001) and triglycerides (p = 0.01). CONCLUSION: All three interventions had benefits in weight loss, while the COM group had an additional effect on greater reduction of body fat compared with the other two groups. In addition to weight reduction, partial improvements in lipid profiles were observed. Low-carbohydrate and HIIE may represent viable strategies for weight and metabolic management in prediabetic individuals.
Read CV Ye HeECSS Paris 2023: OP-PN09
INTRODUCTION: Endurance performance has traditionally been determined by maximal oxygen uptake (V̇O2max), fractional utilization at lactate threshold, and exercise economy. However, these parameters do not capture the temporal deterioration in physiological characteristics during prolonged endurance exercise (i.e., durability or physiological resilience). Furthermore, the extent to which this fatigue-induced deterioration can be mitigated through nutritional strategies remains poorly understood. This study investigated the effects of graded carbohydrate (CHO) ingestion on changes in critical power following 3 h of moderate-intensity cycling. We hypothesized that moderate-intensity exercise would reduce the power output at the heavy-to-severe intensity transition, and that higher CHO ingestion rates METHODS: Using a randomized, counterbalanced crossover design, 16 endurance-trained cyclists and triathletes (V̇O2max 51.8 ± 6.8 mL·kg–1·min–1, gas exchange threshold [GET] 178 ± 15 W) completed a 3-minute all-out critical power test (3MT) in the following conditions: rested state, and after three prolonged 3 h cycles at 95% GET (‘fatigued’ state) while ingesting a CHO drink at a rate of 0 g·h–1 (WATER), 60 g·h–1 (CHO60) and 120 g·h–1 (CHO120). CHO drinks contained maltodextrin and fructose in a 1:0.8 ratio. Each experimental trial was preceded by a standardized 24 h CHO loading protocol (8 g·kg–1 body mass) and a pre-exercise meal (2 g·kg–1). Critical power was calculated as the mean power output over the last 30 s of the 3MT (end-test power [EP]), and W′ as the total amount of work above EP (WEP). RESULTS: Critical power measured in a rested state (Control-EP) was significantly reduced in all experimental conditions (P<0.001), meaning Fatigued-EPWATER (236±30 W [–14.7±7.1%], P<0.001), Fatigued-EPCHO60 (257±28 W [–7.4±4.7%], P<0.001) and Fatigued-EPCHO120 (266±29 W [–4.2±3.7%], P=0.002) were lower than Control-EP (277±27 W). However, this deterioration was attenuated with increasing CHO intake, such that Fatigued-EPCHO60 was higher than Fatigued-EPWATER (P<0.001, Cohen’s d=1.92), and higher in Fatigued-EPCHO120 compared with Fatigued-EPCHO60 (P=0.006, Cohen’s d=1.01). W′ declined following prolonged exercise compared to fresh values (Control-WEP 15.46±3.61 kJ, P<0.001), with no differences between fatigued conditions (F-WEPWATER 12.01±3.98 kJ, F-WEPCHO60 13.41±3.65 kJ, F-WEPCHO120 12.72±3.61 kJ; P>0.05). Mean whole-body CHO oxidation rates were significantly higher with increasing CHO intake (WATER 1.84±0.28, CHO60 2.16±0.15, CHO120 2.31±0.14 g·min–1; P<0.001). CONCLUSION: These data suggest that high CHO ingestion at 120 g·h–1 limits the reduction in power output at the heavy-to-severe domain boundary (i.e., critical power) following 3 h of moderate-intensity cycling, with no apparent effect on W′. These findings demonstrate that the boundary between exercise intensity domains shifts under fatigue, with CHO availability acting as a key modulator of endurance durability.
Read CV Bernardo NorteECSS Paris 2023: OP-PN09