ECSS Paris 2023: OP-PN10
INTRODUCTION: High altitude-related impaired oxygen delivery to working muscles leads to decelerated oxygen uptake kinetics during exercise (1). We previously demonstrated that ketone monoester (KE) ingestion enhances oxygen uptake and mitigates tissue oxygenation reductions during moderate-intensity exercise under acute simulated high-altitude conditions (2). Under this premise, we aimed to evaluate the effects of intermittent exogenous ketosis on oxygen uptake kinetics and oxygenation responses during moderate-intensity exercise across three days at terrestrial high altitude. METHODS: Healthy, recreationally active participants were randomized into an intermittent exogenous ketosis (IEK, n = 17) and a placebo group (PLA, n = 17). They completed four moderate-intensity exercise sessions; one near sea-level (295 m), and the other three on consecutive days at terrestrial high altitude (3375 m). To establish a true baseline, no supplementation was administered at sea level. At high altitude, IEK received daily KE supplements, while PLA received placebo supplements 30 minutes prior to exercise. Each session consisted of three 6-minute cycling intervals at 80% of the gas exchange threshold, separated by 6-minute active recovery periods at 0 W. Power output during high-altitude sessions was adjusted to account for predicted altitude-induced exercise capacity reductions (3). Pulmonary oxygen uptake, systemic oxygen saturation, and muscle tissue oxygenation were continuously measured during exercise transitions and steady-state phases. Group differences over time were evaluated using mixed-model ANOVA, with statistical significance set at p < 0.05. RESULTS: Pre-exercise ketosis was consistently induced in IEK (~2.5 mM) compared to PLA (~0.3 mM) (p < 0.001). Relative to sea level, the amplitude of the oxygen uptake response decreased upon arrival at high altitude (p < 0.001), and remained reduced throughout early acclimatization (p > 0.181), with no between-group differences (p > 0.05). The time constant of the primary phase of oxygen uptake kinetics was not modified by either high-altitude exposure time (p = 0.136) or supplementation (p = 0.823). Systemic oxygen saturation declined significantly upon arrival at high altitude compared to sea level (p < 0.001), and progressively improved throughout acclimatization, yet again independent of the supplementation (p = 0.169). In contrast, muscle tissue oxygenation did not significantly change across time (p = 0.102), and no difference was seen between groups (p = 0.591). CONCLUSION: These data suggest that pre-exercise ketosis at high altitude does not influence oxygen uptake kinetics, systemic oxygen saturation, or muscle tissue oxygenation during moderate-intensity exercise across three days of high-altitude acclimatization. 1. Cleuziou C. et al., Int J Sports Med. 2005;26(5):356-62 2. Poffe C, et al., Am J Physiol Regul Integr Comp Physiol. 2021;321(6):844-57 3. MacInnis MJ, et al., Med Sci Sports Exerc. 2015;47(9):1869-76
Read CV Domen TominecECSS Paris 2023: OP-PN10
INTRODUCTION: The high-carbohydrate (HC) diet is widely adopted to enhance endurance and power output, while KD has been suggested to impair high-intensity performance. KD shifts reliance towards fat oxidation, due to glycogen depletion. This study assessed the impact of athletes following habitual (>3 months) HC and KD diets on exercise performance. METHODS: Nineteen recreationally active individuals (mean age: 35 ± 9 y; stature: 175.5 ± 10.5 cm; body mass: 79.5 ± 12.4 kg; body fat %: 20.3 ± 6.2%; fat-free mass: 63.2 ± 11.6 kg were stratified into those who followed either a KD (<50 g/day CHO, >60% fat) or HC (225–325 g/day CHO, 45–65% CHO),diet for the preceding 3-months. Diets were verified via food frequency questionnaires and MyFitnessPal tracking during testing (KD: n = 8, HC: n = 11). A six-session battery of tests spanned three weeks under standardised conditions (≥3h fasted, no prior training). Visit 1 (V1) included anthropometric assessment, arm crank VO₂ max (ACEVO₂MAX), isokinetic dynamometry (ISODYNO) (30°–240°/s), and a 30-second Wingate anaerobic test (30sWAnT). V2 comprised an ACE one-hour endurance test (ACE1HR) and a 20-minute performance test. (ACE20Min). V3 assessed maximal oxygen uptakes on a LODE cycle ergometer (LODEVO₂MAX). V4 included a one-hour endurance test on the LODE cycle ergometer (LODE1HR) followed by a five-by-10-second repeat sprint Wingate test (10sWAnT). Heart rate (HR), respiratory exchange ratio (RER), VO₂ (ml.kg.min-1), power (PWR, W) and time to fatigue (s) were recorded, while blood glucose (BG, mg/dl), ketones (BK, mmol/L), and lactate (BL, mmol/L) were recorded at set intervals per test for group comparison. Data was analysed using SPSS 29 for normality. Independent t-tests compared between-group differences in VO₂ max, RER, heart rate, peak torque, average power, and fatigue factor, while a Repeated-Measures ANOVA analysed time × diet interactions for HR, RER, VO₂, BG, BK and BL. Significance was set at p < 0.05. Data are expressed as mean ± SD. RESULTS: No significant differences were found in V1 for ACEVO₂max, peak HR, or ISODYNO average power. However, KD had lower RER (p < 0.05) and greater PeakTQBW at 120°/s and 240°/s (p < 0.05). In 30sWAnT, no differences were found in peak PWR, distance, or fatigue factor, though KD showed greater variance. During V2, VO₂ increased over time (p < 0.05) and was higher in KD (p < 0.05), while ACE1HR and ACE20MIN distance were similar. BK was higher in KD (p < 0.05).In V3/V4, no differences were found in LODEVO₂MAX or LODE1HR, but KD had higher BL (p < 0.05). In 10sWAnT, HC had higher cadence and speed in sprints 1–4 (p < 0.05), while peak PWR and distance were unchanged. CONCLUSION: KD increased fat oxidation and VO₂ uptake during endurance exercise, while HC resulted in higher cadence and sprint speed. Although both diets elicit different metabolic responses there is little consequential difference between dietary approaches and exercise performance.
Read CV Richard PhillipsECSS Paris 2023: OP-PN10
INTRODUCTION: Hepcidin, an iron-regulating hormone, is thought to be downregulated by stimuli that promote erythropoiesis (Nemeth & Ganz, 2023). Ketosis, characterized by elevated β-hydroxybutyrate (βHB) levels, was reported to increase post-exercise serum erythropoietin (EPO) concentration following acute ketone supplementation in healthy men (Evans et al., 2023). Therefore, this study aimed to investigate the effects of βHB supplementation after exercise on EPO and hepcidin responses in active women. METHODS: Eight women completed the experimental trials [means ± SD, age: 20 ± 1 years, height: 155.8 ± 7.9 cm, body mass (BM): 54.9 ± 6.2 kg, peak oxygen consumption (VO2peak): 45.7 ± 4.3 mL/kg/min] under two different conditions during the early-follicular phase: either consuming 25.5 g of βHB (8.5 g/h, 3 times; βHB) or an equivalent amount of placebo (CON) after high-intensity interval exercise (3-minutes warm-up, 8 sets of 3-minutes cycling at 85%VO2peak, 3-minutes cool-down). The βHB/placebo supplements (OKETOA®, Osaka Gas Co., Ltd.) were consumed immediately, 60 min and 120 min after exercise. A light meal (0.9 g/kg BM of carbohydrate, 0.1 g/kg BM of protein) was consumed with βHB/placebo supplements 60 min after exercise. Blood samples were collected before and after exercise (0, 30, 120, and 180 min); respiratory samples with a breath-by-breath method were collected before and after exercise (30, 120, and 180 min). A repeated-measures two-way ANOVA was applied, and significant interactions or main effects were followed up using Bonferroni post-hoc test. Significance was set at p < 0.05. RESULTS: Significant differences were observed in serum βHB responses (F = 43.523, p < 0.001). Serum βHB concentrations were significantly higher in the βHB trial than in the CON trial (30 min: p = 0.004, 60 min: p = 0.004, 120 min: p = 0.006, 180 min: p = 0.028). The βHB trial showed a significantly lower mean blood glucose concentration than the CON trial (F = 11.372, p = 0.012). Significant differences were observed in changes in the respiratory exchange ratio (RER; F = 3.994, p = 0.011). The βHB trial exhibited a significantly lower RER 120 min after exercise than in the CON trial (p = 0.002). No significant differences were observed in serum hepcidin response between the trials (F = 0.714, p = 0.427). Significant differences were observed in serum EPO response between the trials (F = 7.595, p = 0.020); however, the post-hoc test did not reveal significant differences between the trials. Changes in serum EPO concentration (180 min minus pre-exercise) were significantly different between the trials (βHB: + 0.325 ± 0.974 mIU/mL, CON: -1.325 ± 1.400 mIU/mL; p = 0.027). CONCLUSION: Exogenous ketosis via βHB supplementation influenced the EPO response and glucose metabolism but did not affect the hepcidin response following high-intensity interval exercise.
Read CV Nanako HayashiECSS Paris 2023: OP-PN10