ECSS Paris 2023: OP-PN34
INTRODUCTION: Carbohydrate (CHO) ingestion during endurance exercise improves performance (1). Peak exogenous CHO oxidation of 1.8 g·min-1 has been shown when 2.0 g·min-1 is ingested during cycling exercise (2). While such intakes were well tolerated in cyclists, the feasibility of 120 g.h-1 during running exercise and at higher exercise intensities is unclear, with both being associated with higher gastrointestinal (GI) symptom prevalence (3). This study investigated the effect of varying CHO doses on exercise metabolism and GI symptoms in elite runners exercising in the heavy intensity domain. METHODS: In a double-blind, randomised crossover design, 8 male marathon runners (PB 02:22:54 ± 00:05:37) completed three trials after a 24h high CHO (8 g·kg-1) diet and pre-exercise meal (2 g·kg-1). Trials consisted of a 120-min run, with 90 min at 94% of lactate turnpoint, flanked by 15 mins at 95% of lactate threshold. Every 15 minutes, subjects consumed U-13C enriched drinks at rates of 60 (1:0, maltodextrin: fructose), 90 (2:1), or 120 (1:1) g·h⁻¹. CHO and fat oxidation, blood glucose and lactate, running economy, and GI symptoms were measured. A one-way and two-way repeated-measures ANOVA analysis was used for peak exogenous CHO oxidation and time and trial differences, respectively, followed by Bonferroni post hoc analysis. Significance was set at P<0.05. RESULTS: There was a significant main effect of condition (F2, 14 = 25.71, p<0.001), with mean whole body CHO oxidation higher in 120 g·h⁻¹ (3.06±0.19 g·min⁻¹) than 90 g·h⁻¹ (2.46±0.12g·min⁻¹; p=0.001) and 60 g·h⁻¹ (2.08±0.03 g·min⁻¹; p=0.004). A significant effect of time for whole body CHO (F7, 49 = 40.31, p<0.001) and exogenous CHO oxidation (F7,49 = 150.42, p<0.001) was found. A condition x time interaction for whole body (F14,98 = 2.32, p<0.008) and exogenous CHO (F14,98 = 9.60, p<0.001) oxidation showed that oxidation increased over time more with higher intakes. Peak exogenous oxidation rates were highest (p<0.001) at 120 g·h⁻¹ (1.78±0.2 g·min⁻¹) compared to 90 g·h⁻¹ (1.48±0.2 g·min⁻¹) and 60 g·h⁻¹ (1.02±0.1 g·min⁻¹). The incidence of moderate or severe (≥4) GI symptoms was high across all conditions, though not significantly different. All runners reported experiencing one or more moderate or severe symptoms. CONCLUSION: Consuming 120 g·h⁻¹ increases whole-body CHO and exogenous oxidation compared to 60 and 90 g·h⁻¹, with no effect on the incidence of GI symptoms. The high prevalence of GI symptoms in all trials requires further investigation and may be due to the higher exercise intensity. Future research should investigate the impact on performance.
Read CV Samanvita RavikantiECSS Paris 2023: OP-PN34
INTRODUCTION: Low energy availability (LEA) is the underlying cause of the Female Athlete Triad and Relative Energy Deficiency in Sports (REDs) and has potentially detrimental effects on health and performance. LEA is typically associated with reduced availability of carbohydrates, a critical substrate for cellular metabolism, energy storage and energy supply of the brain. While current consensus statements on REDs highlight the importance of adequate carbohydrate availability (CA) as a mitigating factor, to our knowledge, no experimental study has directly assessed the effects of varying CA under conditions of LEA. METHODS: In a randomized, cross-over study, participants (n=11, 36% male, 24±2years) underwent two 4-day intervention phases with a 2-week washout period between conditions. In both conditions, energy availability was reduced to 20 kcal/kg fat-free mass (FFM)/day by clamping energy intake at 45 kcal/kg FFM/day and exercise energy expenditure at 25 kcal/kg FFM/d, which was achieved by cycling at 60% of maximal oxygen uptake. CA, which was defined as the difference between carbohydrate intake and carbohydrate oxidation during exercise, was maintained either at 1.5g/kg/day (LEA-LC) or 4.0g/kg/day (LEA-HC). Assessments included changes in body weight and body composition, substrate utilization and selected metabolic hormones (leptin, insulin, IGF-1). RESULTS: Both conditions resulted in similar weight loss (-0.6±0.6kg vs. -0.7±0.7kg; p=0.60). Maximal fat oxidation increased to a greater degree in LEA-LC than in LEA-HC (+39±31% vs. +7.3±17.9%; p<0.05). Changes in leptin (-40±21% vs. -26±29%) and IGF-1 (-24±8% vs. -10±13%) were significantly greater in LEA-LC when compared to LEA-HC (both p<0.05). In contrast, changes in insulin were similar between conditions (-15±36% vs. -18±26%; p=0.56). CONCLUSION: Our findings demonstrate the differential effects of high and low CA under conditions of LEA on substrate utilization and endocrine pathways. Low CA amplifies metabolic shifts towards fat oxidation, paralleling metabolic changes seen with carbohydrate restriction at normal energy availability. On the other hand, increased CA preserves nutrient-sensing pathways such as insulin- and leptin-mediated production of IGF-1, thereby mitigating endocrine disruption associated with LEA.
Read CV Karsten KoehlerECSS Paris 2023: OP-PN34
INTRODUCTION: Higher carbohydrate (CHO) availability is a key factor in enhancing endurance performance during prolonged exercise. The combination of fructose and glucose has been shown to improve CHO absorption and oxidation, offering an effective means of increasing overall CHO availability. However, the optimal dosage of this combination, particularly in the context of team sports like soccer, remains unclear. Studies on endurance cyclists have demonstrated that a 90 g·h⁻¹ fructose-glucose mixture can enhance performance, but its impact on prolonged intermittent exercise, such as the extra time phase in soccer, has not been well established. Extra time, a 30-min period added when matches are tied, is a common feature in major tournaments like the FIFA World Cup. This study aimed to investigate the effects of a higher CHO dose, provided in gel form through a fructose-glucose mixture (1:2 ratio), on performance during a 120-min simulated soccer match, compared to a lower dose of glucose only. METHODS: Fifteen semi-professional soccer players (7 males, 8 females) participated in two 120-min soccer-specific exercise sessions, completed in a randomised, single-blinded crossover design. Participants consumed either 60 g·h⁻¹ glucose or a combination of 0.5 g∙min⁻¹ fructose and 1.0 g∙min⁻¹ glucose (90 g·h⁻¹) at pre-exercise, halftime, full-time, and midway through extra time. Assessments at 0, 45, 90, and 120 min included gastrointestinal (GI) discomfort, mental fatigue, passing accuracy, neuromuscular performance (reactive strength index, countermovement jump height, peak power output), and sprint performance (15 m and 30 m sprints). Blood glucose and lactate concentrations were measured every 15 min. RESULTS: Countermovement jump height, peak power output, and sprint performance declined over time in both conditions (p < 0.05). Fructose-glucose co-ingestion increased blood glucose by 0.41 mmol∙L from 105 min compared to glucose-only ingestion (p = 0.006, d = 1.2), but did not preserve performance (p > 0.05). GI symptoms were more pronounced with fructose-glucose, including greater fullness at 90 min (+9.9%, p = 0.013, d = 0.9) and increased abdominal cramps at 45 min (+9.3%, p < 0.001, d = 1.7) and 90 min (+9.0%, p < 0.001, d = 1.6). Glucose-only ingestion led to higher gastric reflux at 45 min (+7.8%, p = 0.011, d = 0.9) and flatulence at 120 min (+3.3%, p = 0.003, d = 1.1). No other variables were significantly affected (p < 0.05). CONCLUSION: Fructose-glucose co-ingestion increased blood glucose availability during the latter stages of exercise but did not prevent declines in neuromuscular or sprint performance compared to glucose-only ingestion. Additionally, the higher CHO dose caused greater GI discomfort, which may limit its practicality for soccer players during extended match play. Future research should refine CHO intake strategies for intermittent sports, balancing performance benefits with GI tolerance.
Read CV Adam FieldECSS Paris 2023: OP-PN34