ECSS Paris 2023: OP-PN09
INTRODUCTION: Maximal fat oxidation (MFO) has implications for metabolic health [1] and explains between 12-14% of the variance in ultra-endurance events [2,3]. MFO seems to be influenced by training status, exercise intensity/duration, nutrition and sex [4]. Regarding the latter, there are still inconclusive findings on the influence of sex, that are biased by the expressed units and performance differences between groups [5,6]. This study aimed to compare MFO and the corresponding intensity (Fatmax) between females and males who are matched for maximal oxygen uptake (V̇O2max). METHODS: A sub-sample was taken from a previous study in N = 44 well-trained runners/triathletes [7]. Ultimately, n = 10 females and n = 10 males met the inclusion criterion of a V̇O2max between 55 and 63 ml/min/kg. Substrate oxidation rates were calculated from a graded exercise test by using equations of stoichiometry [8]. Fat oxidation was calculated for every intensity level and interpolated by a quadratic polynomial to determine MFO and Fatmax (expressed in %V̇O2max). Normality was checked by the Kolomogorov-Smirnov test (α=10%). Based on this criterion, comparisons between groups were performed by an independent t-test or the Mann-Whitney-U-test (α=5%). Effect-sizes were calculated as Cohen’s d. RESULTS: There was no significant difference between females and males in terms of V̇O2max (d=-0.331, p=0.533), MFO (d=-0.500, p=0.269), Fatmax (d=0.030, p=0.948), onset of blood lactate accumulation (d=-0.775, p=0.108) and maximal lactate accumulation rate (d=-0.919, p=0.600). MFO was 0.38±0.14 and 0.45±0.14 g/min in females and males, respectively. Even if MFO was normalised to fat free mass, there was no difference between sexes (d=0.330, p=0.432). However, females needed significantly more time to cover a 5-km time trial (d=1.383, p=0.006). CONCLUSION: MFO and Fatmax were similar in females and males who are matched for V̇O2max. This indicates that the influence of training status is higher than the influence of sex per se. However, these results are specific for the applied protocol, equipment and equations, that seem to influence outcomes of fat oxidation [9]. Limitations worth mentioning are that no concrete standardizations were applied in terms of nutrition, daytime and menstrual cycle between participants, which increases the secondary variance of this study. Future studies should validate these findings in a larger and more standardized sample as well as in elite (endurance) athletes. References 1) Chavéz-Guevara et al. Eur J Appl Physiol 2) Fradsen et al. (2017) Int J Sports Med 3) Martinez-Navarro et al. (2020) Int J Sports Med 4) Purdom et al. (2018) J Int Soc Sports Nutr 5) Randell et al. (2017) Med Sci Sports Exerc 6) Maunder et al. (2018) Front Physiol 7) Quittmann et al. (2022) Int J Sports Med 8) Péronnet & Massicotte (1991) Can J Sport Sci 9) Amaro-Gahete et al. (2019) Scand J Med Sci Sports
Read CV Oliver Jan QuittmannECSS Paris 2023: OP-PN09
INTRODUCTION: An increasing number of recreational active athletes are considering a low-carbohydrate, high-fat (LCHF) diet for health and performance reasons. Nevertheless, the question remains whether an LCHF diet can be considered healthy, especially for individuals at higher risk for cardiovascular diseases. Therefore, the objective was to investigate the impact of a LCHF diet on blood lipid profiles in endurance trained individuals, comparing it to a high carbohydrate (CHO) diet with varying glycaemic indices. METHODS: In a randomised, parallel group design, recreationally active runners (n=65, VO2 peak=55±8 mL·min-1·kg-1) completed 10 weeks of an ad libitum dietary intervention (LOW-GI:≥65% low GI CHO per day, n=24; HIGH-GI:≥65% high GI CHO per day, n=20; LCHF:≤50g CHO daily, n=21) together with prescribed five sessions of an endurance training program. Dietary recalls were conducted twice a week during the intervention phase. Serum was collected at the beginning and after 10 weeks and was analysed for fasting total cholesterol (TC), triglycerides (TG), LDL-C and HDL-C. Data were analysed using a 2-way mixed ANOVA und are presented as mean±STD. RESULTS: Significant time x group interactions were found for TC, HDL-C and LDL-C and are presented in the following. After the intervention, TC was significantly higher in LCHF (196±37 mg·dL-1) compared to LOW-GI (171±41 mg·dL-1) or HIGH-GI (152±28 mg·dL-1, p<0.001, ηp2=0.201). LDL-C was reduced in LOW-GI (-14±20 mg·dL-1) and HIGH-GI (-13±18 mg·dL-1), increased for subjects in LCHF (17±21 mg·dL-1, p<0.05 respectively) and differed significantly between all groups after 10 weeks (p<0.001, ηp2=0.257). Participants in HIGH-GI experienced a reduction in HDL-C (-3±9 mg·dL-1, p=0.006), while the changes in the other two regimes were not significant. Additionally, during the intervention, intake in saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) was significantly higher in LCHF compared to CHO groups (p<0.001, ηp2 = 0.459, ηp2 = 0.520). Compared to LOW-GI intake in SFA (27±13 vs. 60±20 g·day-1) and MUFA (28±11 vs. 63±23 g·day-1) was around 45% higher in LCHF. Intake in soluble and insoluble fibre differed significantly between groups (p<0.001, ηp2 = 0.507, ηp2 = 0.378) with the highest intake in LOW-GI (12±3 and 28±6 g·day-1) and the lowest intake in LCHF (6±2 and 18ׅ±8 g·day-1). CONCLUSION: Although a LCHF diet is often recommended for weight loss and improvement of fat oxidation, the current data suggest that a LCHF diet, even if together with regular endurance exercise, significantly impairs blood lipids compared to a high CHO diet. In addition, a higher fibre intake combined with a lower intake of SFA, resulted in favourable changes in blood lipids during a CHO rich diet, independent of GI. These findings suggest that active individuals should consider the potential effects of their diet on blood lipid levels, as a LCHF diet may counteract the benefits of exercise thereby potentially increasing their atherogenic risk profile.
Read CV Anna MoitziECSS Paris 2023: OP-PN09
INTRODUCTION: Carbohydrate (CHO) metabolism is crucial for performance in middle distance races. However, it has so far not been studied robustly if low glycogen stores could interfere with the exercise capacity in the field conditions of relatively short endurance events. It thus remains to be determined if diminished glycogen stores affect sports performance where relatively small amounts of CHO are required to complete the race. The present study tested how 1500 m race is affected by dietary manipulation intended to alter pre-race glycogen reserves in high-level runners. METHODS: National level middle distance runners [n=11 (4 females); age: 21.4 (SD 4.3) y, height: 179.5 (10.5) cm, BMI: 21.2 (1.5), training volume: 12.3 (1.8) h/wk, 69 (25) km/wk] completed, in a randomized cross-over design, a 1500 m time trial (TT) after abundant (High) or restricted (Low) CHO consumption for 2 days after glycogen depleting session (60 min of continuous moderate intensity run followed by 10 x 200 m at planned 1500 m TT pace). CHO intake during 5 days before the each glycogen depleting session averaged 4.8 (1.4) g/kg/d. To keep the diet between glycogen depleting session and TT eucaloric, the Low condition required substitution of most of the diet CHO with fats, while the High condition required consumption of foods high in CHO and low in fats (protein intake was aimed to be unchanged). During Low and High conditions, CHO intake was <2 g/kg/d (average 1.0 (0.4) g/kg/d) and >5 g/kg/d (average 9.7 (2.6) g/kg/d), respectively. The TT took place in an indoor 200 m track and was run individually with time recorded every 100 m split. Striding pattern, heart rate (HR), capillary blood lactate and glucose dynamics and plasma malondialdehyde (MDA, an oxidative stress marker) response were determined. RESULTS: Time to complete 1500 m TT was slower in Low vs. High condition by 4.5 (4.5) s (i.e. by ~2%; p<0.01). Slowing in the later stages of the race in Low condition was largely due to decrease in stride length (p<0.05) rather than stride frequency. HR response to TT was not affected by feeding condition. Blood lactate and glucose were lower immediately before TT in Low vs. High condition (1.8 (0.5) vs. 2.2 (0.7) mmol/l and 5.4 (0.7) vs. (5.9 (0.8) mmol/l, p=0.022 and 0.007, respectively), peak lactate was higher in High vs. Low condition (16.8 (3.1) vs. 14.5 (4.2) mmol/l, p=0.039), while glucose was not affected by feeding condition during the 15 min of passive recovery. Plasma MDA levels did not differ between the conditions before TT, and 15 min after TT increased similarly by 15 % in Low (p=0.03) and High (p<0.01) conditions. CONCLUSION: In conclusion, compared to CHO restriction, a diet with ample CHO after a glycogen depleting session allowed for faster 1500 m race in high-level distance runners. Restriction of CHO to <2 g/kg/d after the glycogen exhaustion session slightly reduced baseline and peak blood lactate values but did not markedly change blood glucose or plasma MDA response to 1500 m race.
Read CV Tomas VenckunasECSS Paris 2023: OP-PN09