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Abstract

The aim of the present study was to investigate the relationship between maximal fat oxidation rate (MFO) measured during a progressive exercise test on a cycle ergometer and ultra-endurance performance. 61 male ironman athletes (age: 35±1 yrs. [23–47 yrs.], with a BMI of 23.6±0.3 kg/m2 [20.0–30.1 kg/m2], a body fat percentage of 16.7±0.7% [8.4–30.7%] and a VO2peak of 58.7±0.7 ml/min/kg [43.9–72.5 ml/min/kg] SEM [Range]) were tested in the laboratory between 25 and 4 days prior to the ultra-endurance event, 2016 Ironman Copenhagen. Simple bivariate analyses revealed significant negative correlations between race time and MFO (r2=0.12, p<0.005) and VO2peak (r2=0.45, p<0.0001) and a positive correlation between race time and body fat percentage (r2=0.27, p<0.0001). MFO and VO2peak were not correlated. When the significant variables from the bivariate regression analyses were entered into the multiple regression models, VO2peak and MFO together explained 50% of the variation observed in race time among the 61 Ironman athletes (adj R2=0.50, p<0.001). These results suggests that maximal fat oxidation rate exert an independent influence on ultra-endurance performance (>9 h). Furthermore, we demonstrate that 50% of the variation in Ironman triathlon race time can be explained by peak oxygen uptake and maximal fat oxidation.

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... 2024, 9, 141 2 of 10 system by the prolonged endurance training regimes and the dietary and carbohydrate intake strategies may also enhance the capacity for fat oxidation by causing an increase in mitochondrial volume density [7] and increased capillarisation [8]. Interestingly, in male Ironman athletes, there was a significant negative correlation between race time and maximal fat oxidation (r 2 = 0.12) [9]. However, it is well known that other physiological factors such as maximum oxygen uptake [9] and exercise economy [10] are more essential for race time and competitive completion during an Ironman event. ...
... Interestingly, in male Ironman athletes, there was a significant negative correlation between race time and maximal fat oxidation (r 2 = 0.12) [9]. However, it is well known that other physiological factors such as maximum oxygen uptake [9] and exercise economy [10] are more essential for race time and competitive completion during an Ironman event. During Ironman triathlon competition, carbohydrate intake is essential. ...
... In Ironman athletes, laboratory testing has been focused on metabolic (i.e., maximal fat oxidation) [9] and physiological parameters (e.g., heart rate at ventilatory thresholds [12] to predict overall Ironman competitive performance. As far as we know, observations from laboratory testing on the effectiveness of ergogenic nutritional supplementation in Ironman athletes or other ultra-endurance athletes that are close to competition are absent. ...
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New Zealand blackcurrant (NZBC) is known to alter exercise-induced physiological and metabolic responses with chronic (i.e., 7 days) dosing. We examined the effects of acute intake of New Zealand blackcurrant (NZBC) extract on 4 h indoor cycling-induced physiological and metabolic responses in a male amateur Ironman athlete (age: 49 years; BMI: 24.3 kg·m−2; V˙O2max: 58.6 mL·kg−1·min−1; maximal aerobic power: 400 W; history: 14 Ironman events in 16 years) three weeks before competition. Indirect calorimetry was used and heart rate was recorded at 30 min intervals during 4 h indoor (~22.4 °C, relative humidity: ~55%) constant power (165 W) cycling on a Trek Bontrager connected to a Kickr smart trainer. Blood lactate and rating of perceived exertion (RPE) were taken at 60 min intervals. Study was a single-blind placebo-controlled study with capsules (4 × 105 mg anthocyanins) taken 2 h before starting the 4 h of cycling. Water was allowed ad libitum with personalised consumption of gels [a total of eight with three with caffeine (100 mg)], two bananas and 8 × electrolyte capsules (each 250 mg sodium and 125 mg potassium) at personalised time-points. With NZBC extract (CurraNZ), during 4 h of cycling (mean of 8 measurements), minute ventilation was 8% lower than placebo. In addition, there was no difference for oxygen uptake, with carbon dioxide production found to be 4% lower with NZBC extract. With the NZBC extract, the ventilatory equivalents were lower for oxygen and carbon dioxide by 5.5% and 3.7%; heart rate was lower by 10 beats·min−1; lactate was 40% different with lower lactate at 2, 3 and 4 h; RPE was lower at 2, 3 and 4 h; and carbohydrate oxidation was 11% lower. With NZBC extract, there was a trend for fat oxidation to be higher by 13% (p = 0.096), with the respiratory exchange ratio being lower by 0.02 units. Acute intake of New Zealand blackcurrant extract (420 mg anthocyanins) provided beneficial physiological and metabolic responses during 4 h of indoor constant power cycling in a male amateur Ironman athlete 3 weeks before a competition. Future work is required to address whether acute and chronic dosing strategies with New Zealand blackcurrant provide a nutritional ergogenic effect for Ironman athletes to enhance swimming, cycling and running performance.
... De igual manera, se desconoce la influencia de la disponibilidad de nutrientes y la capacidad oxidativa sobre la MFO en deportistas. Frandsen et al. (2017), reportaron que, en conjunto, el consumo de oxígeno al FATmax, la concentración de ácidos grasos libres en plasma y la concentración de lactato, determinaron el 23% de la variación en MFO (p<0.01) en atletas masculinos de triatlón. ...
... En las tablas 2 y 3 se presentan la MFO y FATmax reportadas en ciclistas (González-Haro et al., 2006;Amaro-Gahete et al., 2019;Frandsen et al., 2019;Zurbuchen., et al., 2020), corredores de larga distancia (Schwindling et al., 2014;Frandsen et al., 2017;Vest et al., 2018;Soria et al., 2020), atletas de esquí a campo traviesa (Dandanell et al., 2018;Hansen et al., 2019;Rømer et al., 2020), jugadores profesionales de futbol soccer (Randell et al., 2019) y grupos mixtos de atletas de futbol soccer, baloncesto, balonmano, volibol, tenis, hockey, béisbol, futbol americano, golf y rugby (Randell et al., 2017;Peric et al., 2018). Retos Al promediar los datos reportados para cada población, se observa que, la MFO es superior en corredores de larga distancia vs ciclistas (0.55±0.09 vs. 0.48±0.05 ...
... Por otro lado, Frandsen et al. (2017) y Vest et al. (2018) reportan que la MFO es superior en mujeres vs hombres, atletas de triatlón (12.9±0.5 vs 9.1±0.3 mg·kg -1 masa magra -1 ·min -1 ), denotando la importancia de establecer valores normativos de MFO según el sexo de los atletas. ...
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Resumen. El uso diferencial de sustratos energéticos (lípidos y carbohidratos) durante la competencia deportiva se ha propuesto como un factor determinante del rendimiento deportivo. Por lo tanto, la presente revisión tiene por objetivos: (i) describir la asocia-ción de la máxima oxidación de grasas (MFO) y su correspondiente intensidad (FATmax) con indicadores del rendimiento deportivo en atletas de resistencia, (ii) reportar el fenotipo metabólico de atletas pertenecientes a diferentes disciplinas deportivas. Resultados: La FATmax y MFO están directamente asociadas entre sí, sin embargo, solo la MFO esta positivamente asociada con el tiempo de carrera en atletas de triatlón, esquiadores profesionales a campo traviesa y corredores de ultramaraton. En dichas poblaciones, el máximo consumo de oxigeno (VO 2 max) muestra una correlación positiva con la MFO, mientras que la edad esta inversamente asociada a MFO. Tanto la FATmax como la MFO han sido estudiados en pocas disciplinas deportivas. Por otro lado, la MFO difiere entre atletas de distintas disciplinas deportivas, siendo superior en corredores de larga distancia y esquiadores profesionales vs. ciclistas (0.55±0.09 vs. 0.48±0.05 g·min-1), a pesar de similitudes en el VO 2 max y la masa libre de grasa. Aunque la MFO reportada en atletas de balonmano, voleibol y baloncesto (0.59±0.24 g·min-1), así como en futbolistas profesionales (0.69±0.15 g·min-1), es superior a los valores observados en corredores de larga distancia y esquiadores de elite. Conclusión: La relación de la MFO y la FATmax con el rendimiento deportivo varía según la edad, disciplina deportiva y el sexo de los atletas, observándose un fenotipo metabólico particular para cada disciplina deportiva. Por lo tanto, además de medir el VO 2 max y la intensidad de trabajo correspondiente al umbral de lactato o segundo umbral ventilatorio se recomienda incorporar la MFO y FATmax en las evaluaciones fisiológicas de los atletas para optimizar su rendimiento físico.
... The maximal fat oxidation rate (MFO) observed at submaximal exercise intensity during an incremental-load exercise test represents the capacity of the skeletal muscle to use fatty acids as a fuel when energy demand raises by muscle contraction (Fig. 1). Since introduced by Jeukendrup and Achten (2001), many studies have analyzed the validity of this parameter as a marker of metabolic flexibility and a predictor of sports performance in endurance athletes, reporting that (1) MFO is directly related to insulin sensitivity (r = 0.33, p < 0.01) and 24-h fat oxidation (r = 0.65, p < 0.01) in healthy males (Robinson et al. 2015); (2) predicts total fat oxidation during steady-state exercise in men with obesity (R 2 = 0.46, p < 0.01) (Chávez-Guevara et al. 2021) and is positively associated with exercise fat oxidation in the postprandial state in trained males (r = 0.83, p < 0.01) (Maunder et al. 2021); (3) is related with fat mass loss induced by exercise training performed at MFO intensity (FATmax) in subjects with obesity (r = 0.35, p < 0.01) (Drapier et al. 2018); (4) it explains 12 and 14% of endurance performance on Ironman (Frandsen et al. 2017) and ultra-trail male athletes, respectively (Martinez-Navarro et al. 2020). The aforementioned evidence highlights the relevance of investigating those biological and nutritional factors as well as the fitness components that determine MFO to understand the molecular and physiological mechanisms affecting metabolic health and athletic performance. ...
... The data from Robinson et al. (2016) suggest that fatty acid availability prior exercise seems to be more determinant than lipolytic response to this stimulus. In this sense, Frandsen et al. (2017) showed that overnight fasting (9-13 h) plasma FFA at rest was independently associated with MFO explaining 6% of its variation in male ironman athletes, although such association was not observed in female ironman athletes (R 2 = 0.07, ns) in whom VO 2peak was the only biomarker associated with MFO (Vest et al. 2018). The discrepancy across these studies suggests that MFO is determined by different physiological mechanisms across male and female ironman athletes which require further analysis. ...
... Furthermore, plasma glucose and lactate were not associated with MFO in trained men (Robinson et al. 2016). On the contrary, plasma lactate levels at rest were negatively associated with MFO (R 2 = 0.12, p < 0.01) in male ironman athletes (Frandsen et al. 2017), although similar lactate concentrations were noted in comparison to the participants from the study of Robinson et al. (2016) (0.8 ± 0.3 vs. 0.8 ± 0.2 mmol L −1 , respectively). Thus, the influence of glycolytic flux at rest and MFO remains controversial and future investigations including individuals with obesity and type II diabetes mellitus who exhibit higher circulating levels of lactate, glucose and insulin will help to elucidate the aforementioned mechanism. ...
Article
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The maximal fat oxidation rate (MFO) assessed during a graded exercise test is a remarkable physiological indicator associated with metabolic flexibility, body weight loss and endurance performance. The present review considers existing biomarkers related to MFO, highlighting the validity of maximal oxygen uptake and free fatty acid availability for predicting MFO in athletes and healthy individuals. Moreover, we emphasize the role of different key enzymes and structural proteins that regulate adipose tissue lipolysis (i.e., triacylglycerol lipase, hormone sensitive lipase, perilipin 1), fatty acid trafficking (i.e., fatty acid translocase cluster of differentiation 36) and skeletal muscle oxidative capacity (i.e., citrate synthase and mitochondrial respiratory chain complexes II–V) on MFO variation. Likewise, we discuss the association of MFO with different polymorphism on the ACE, ADRB3, AR and CD36 genes, identifying prospective studies that will help to elucidate the mechanisms behind such associations. In addition, we highlight existing evidence that contradict the paradigm of a higher MFO in women due to ovarian hormones activity and highlight current gaps regarding endocrine function and MFO relationship.
... On a related topic, during prolonged training and competitive efforts (>4 h), an increased fatty acid contribution to total energy turnover is observed and fat oxidation capacity could be considered as a desirable adaptation for road cycling performance [21,22]. Accordingly, assessing and training to improve this capacity are important aspects of the training process in cycling [22]. ...
... On a related topic, during prolonged training and competitive efforts (>4 h), an increased fatty acid contribution to total energy turnover is observed and fat oxidation capacity could be considered as a desirable adaptation for road cycling performance [21,22]. Accordingly, assessing and training to improve this capacity are important aspects of the training process in cycling [22]. Different authors have reported that the maximal fat oxidation zone (Fatmax) is achieved at approximately 45-60% of VO2max [23,24] and that this concept is closely related to cycling economy and efficiency. ...
... Notably, these differences were not found for the same parameters when the values were normalized to BW (VO2R and Load/BW), which is in line with previous findings [23,24] and had not been reported for either differences in economy and efficiency when amateur and professional cyclist were compared [17]. Based on the present results, coaches should be aware that Fatmax does not seem to be a key factor discriminating the performance level in cyclists, although it could be important in long-term modalities as demonstrated in Ironman triathletes [22]. ...
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Endurance profile assessment is of major interest to evaluate the cyclist’s performance potential. In this regard, maximal oxygen uptake and functional threshold power are useful functional parameters to determine metabolic training zones (ventilatory threshold). The aim of this study was to evaluate and compare the physiological profile of different road cyclist age categories (Youth, Junior, and Under-23) to obtain the performance requirements. Sixty-one competitive road cyclists (15–22 years) performed a maximal incremental test on a bike in order to determine functional parameters (maximal fat oxidation zone, ventilatory thresholds, maximal oxygen uptake, and functional threshold power) and metabolic training zones. The results suggest major differences, with the Youth group showing clear changes in all metabolic zones except in fat oxidation. The main differences between Under-23 vs. Junior groups were observed in maximal relative power output (Under-23: 6.70 W·Kg−1; Junior: 6.17 W·Kg−1) and relative functional threshold power (Under-23: 4.91 W·Kg−1; Junior: 4.48 W·Kg−1). The Youth group physiological profile is clearly different to the other age categories. Some parameters normalized to body weight (maximal oxygen consumption, load and functional threshold power) could be interesting to predict a sporting career during the Junior and Under-23 stages.
... One laboratorybased study in which dietary macronutrient composition was manipulated indicated a possible influence of PFO on 100-km cycling time-trial performance, though this was not statistically significant (Rowlands and Hopkins 2002). Weak associations between PFO during fasted incremental cycling and endurance performance in field-based, multisport events have been observed, although between-subject pre-or during-competition controls were not employed (Frandsen et al. 2017;Vest et al. 2019). As fat oxidation is influenced by feeding status Horowitz et al. 1997;Bergman and Brooks 1999), and increases over time during prolonged exercise (Ahlborg et al. 1974;Watt et al. 2002Watt et al. , 2006, PFO measured during fasted, incremental exercise may not reflect metabolic responses to the prolonged, fed-state exercise typically performed in competition. ...
... The traditional model did not use observed PFO. The bold model has the lowest Akaike information criterion (AIC), and was, therefore, selected as the best and most parsimonious model fit Previously, significant associations between finishing time in an Ironman triathlon and PFO during an incremental test have been observed (Frandsen et al. 2017;Vest et al. 2019), though in these studies the relationships with performance (r = 0.35-0.47, P < 0.05) were weaker than in the present investigation. ...
... P < 0.05) were weaker than in the present investigation. These disparities could be related to the fieldbased, multi-sport, longer duration Ironman triathlons and lack between-subject pre-and during-competition controls used in previous work (Frandsen et al. 2017;Vest et al. 2019). ...
Article
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Purpose Whole-body fat oxidation during exercise can be measured non-invasively during athlete profiling. Gaps in understanding exist in the relationships between fat oxidation during incremental fasted exercise and skeletal muscle parameters, endurance performance, and fat oxidation during prolonged fed-state exercise. Methods Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to assess peak whole-body fat oxidation (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 30-min maximal-effort cycling time-trial preceded by 2-h of fed-state moderate-intensity cycling to assess endurance performance and fed-state metabolism on separate occasions within one week. Results PFO (0.58 ± 0.28 g.min⁻¹) was associated with vastus lateralis citrate synthase activity (69.2 ± 26.0 μmol.min−1.g⁻¹ muscle protein, r = 0.84, 95% CI 0.58, 0.95, P < 0.001), CD36 abundance (16.8 ± 12.6 μg.g⁻¹ muscle protein, rs = 0.68, 95% CI 0.31, 1.10, P = 0.01), pre-loaded 30-min time-trial performance (251 ± 51 W, r = 0.76, 95% CI 0.40, 0.91, P = 0.001; 3.2 ± 0.6 W.kg⁻¹, r = 0.62, 95% CI 0.16, 0.86, P = 0.01), and fat oxidation during prolonged fed-state cycling (r = 0.83, 95% CI 0.57, 0.94, P < 0.001). Addition of PFO to a traditional model of endurance (peak oxygen uptake, power at 4 mmol.L⁻¹ blood lactate concentration, and gross efficiency) explained an additional ~ 2.6% of variation in 30-min time-trial performance (adjusted R² = 0.903 vs. 0.877). Conclusion These associations suggest non-invasive measures of whole-body fat oxidation during exercise may be useful in the physiological profiling of endurance athletes.
... In addition, the importance of substrate utilization is being increasingly emphasized to predict endurance performance [14,15]. It is well known that human carbohydrate stores are limited, and exogenous carbohydrate uptake cannot match utilization rates during prolonged endurance exercise, leading in turn to muscle and liver glycogen depletion and thus fatigue and decreased performance [16]. This has sparked interest into strategies to augment fat oxidation during endurance exercise to preserve endogenous carbohydrate stores [15,17]. ...
... This has sparked interest into strategies to augment fat oxidation during endurance exercise to preserve endogenous carbohydrate stores [15,17]. Yet, no previous research regarding trail running performance factors have examined whether fat metabolism keeps a significant relationship with race time, as it has been demonstrated for Ironman triathlon [16,18]. ...
... Lastly, we were interested in exploring possible associations between body composition and race time. Our hypothesis were: (1) peak oxygen uptake, peak speed and speed at first and second ventilatory thresholds would be related with performance; (2) maximal fat oxidation capacity would be independently associated with performance in male but not in female athletes [16,18]. ...
Article
The study aimed to assess the relationship between peak oxygen uptake, ventilatory thresholds and maximal fat oxidation with ultra trail male and female performance. 47 athletes (29 men and 18 women) completed a cardiopulmonary exercise test between 2 to 4 weeks before a 107-km ultra trail. Body composition was also analyzed using a bioelectrical impedance weight scale. Exploratory correlation analyses showed that peak oxygen uptake (men: r = –0.63, p = 0.004; women: r = –0.85, p < 0.001), peak speed (men: r = –0.74, p < 0.001; women: r = –0.69, p = 0.009), speed at first (men: r = –0.49, p = 0.035; women: r = –0.76, p = 0.003) and second (men: r = –0.73, p < 0.001; women: r = –0.76, p = 0.003) ventilatory threshold, and maximal fat oxidation (men: r = –0.53, p = 0.019; women: r = –0.59, p = 0.033) were linked to race time in male and female athletes. Percentage of fat mass (men: r = 0.58, p = 0.010; women: r = 0.62, p = 0.024) and lean body mass (men: r = –0.61, p = 0.006; women: r = –0.61, p = 0.026) were also associated with performance in both sexes. Subsequent multiple regression analyses revealed that peak speed and maximal fat oxidation together were able to predict 66 % of male performance; while peak oxygen uptake was the only statistically significant variable explaining 69 % of the variation in women’s race time. These results, although exploratory in nature, suggest that ultra trail performance is differently predicted by endurance variables in men and women.
... 10 Recently, the relationship between prolonged endurance performance and the peak fat oxidation rate (PFO) was investigated in male and female ironman triathletes. 11,12 PFO was measured during a graded exercise protocol, and race time in the Copenhagen Ironman was used as measure of performance. PFO 11,12 and the exercise intensity at which it occurs (Fat max ) 12 were negatively correlated with race time, albeit V O 2peak was the strongest predictor of performance. ...
... 11,12 PFO was measured during a graded exercise protocol, and race time in the Copenhagen Ironman was used as measure of performance. PFO 11,12 and the exercise intensity at which it occurs (Fat max ) 12 were negatively correlated with race time, albeit V O 2peak was the strongest predictor of performance. 11,12 Together, these results suggest that PFO and Fat max are related to prolonged endurance performance, thus indicating a potential performance benefit in athletes with superior fat oxidation. ...
... PFO 11,12 and the exercise intensity at which it occurs (Fat max ) 12 were negatively correlated with race time, albeit V O 2peak was the strongest predictor of performance. 11,12 Together, these results suggest that PFO and Fat max are related to prolonged endurance performance, thus indicating a potential performance benefit in athletes with superior fat oxidation. ...
Article
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The peak fat oxidation rate (PFO) and the exercise intensity that elicits PFO (Fatmax) is associated with endurance performance during exercise primarily involving lower body musculature, but it remains elusive whether these associations are present during predominant upper body exercise. The aim was to investigate the relationship between PFO and Fatmax determined during a graded exercise test on a ski‐ergometer using double poling (GET‐DP) and performance in the long‐distance cross‐country skiing race, Vasaloppet. Forty‐three healthy men completed GET‐DP and Vasaloppet and were divided into two subgroups; recreational (RS, n=35) and elite skiers (ES, n=8). Additionally, RS completed a cycle‐ergometer GET (GET‐Cycling) to elucidate whether the potential relationships were specific to exercise modality. PFO (r²=0.10, p=0.044) and Fatmax (r²=0.26, p<0.001) were correlated with performance, however, V̇O2peak was the only independent predictor of performance (adj. R²=0.36) across all participants. In ES, Fatmax was the only variable associated with performance (r²=0.54, p=0.038). Within RS, DP V̇O2peak (r²=0.11, p=0.047) and ski specific training background (r²=0.30, p=0.001) were associated with performance. Between the two GETs Fatmax (r²=0.20, p=0.006) but not PFO (r²=0.07, p=0.135) was correlated. Independent of exercise mode, neither PFO nor Fatmax were associated with performance in RS (p>0.05). These findings suggest that prolonged endurance performance is related to PFO and Fatmax but foremost to V̇O2peak during predominant upper body exercise. Interestingly, Fatmax may be an important determinant of performance among ES. Among RS, DP V̇O2peak and skiing experience appeared as performance predictors. Additionally, whole‐body fat oxidation seemed specifically coupled to exercise modality.
... Martinez-Navarro et al. (2022) showed a correlation between MFO and completion time for a 107-km ultra-trail running race (Martinez-Navarro et al., 2022). Additionally, Frandsen et al. (2017) found a negative correlation between MFO and race time among ironman athletes, indicating that higher MFO levels are linked to improved ultra-endurance performance (Frandsen et al., 2017). These outcomes suggest that MFO is an important criterion for endurance athletes. ...
... Martinez-Navarro et al. (2022) showed a correlation between MFO and completion time for a 107-km ultra-trail running race (Martinez-Navarro et al., 2022). Additionally, Frandsen et al. (2017) found a negative correlation between MFO and race time among ironman athletes, indicating that higher MFO levels are linked to improved ultra-endurance performance (Frandsen et al., 2017). These outcomes suggest that MFO is an important criterion for endurance athletes. ...
Article
Taurine (TAU) has been shown to improve time to exhaustion (TTE) and fat oxidation during exercise; however, no studies have examined the effect of acute TAU supplementation on maximal fat oxidation (MFO) and related intensity to MFO (FATmax). Our study aimed to investigate the effect of acute TAU supplementation on MFO, FATmax, VO2peak, and TTE. Eleven recreationally trained male endurance runners performed three incremental running tests. The first visit included a familiarization to the test, followed by two subsequent visits in which exercise was performed 90 min after ingestion of either 6-g TAU or placebo (PLA) using a triple-blind randomized crossover design. There was no effect of TAU on MFO (p = .89, d = −0.07, TAU: 0.48 ± 0.22 g/min; PLA: 0.49 ± 0.15 g/min or FATmax (p = .26, d = −0.66; TAU: 49.17 ± 15.86 %˙VO2peak; PLA: 56.00 ± 13.27 %˙VO2peak). TTE was not significantly altered (TAU: 1,444.8 ± 88.6 s; PLA: 1,447.6 ± 87.34 s; p = .65, d = −0.04). TAU did not show any effect on ˙VO2peak in comparison with PLA (TAU: 58.9 ± 8.4 ml·kg−1·min−1; PLA: 56.5 ± 5.7 ml·kg−1·min−1, p = .47, d = 0.48). However, ˙VO2 TAU at most stages of exercise with large effect sizes (η2p=.43). The acute ingestion of 6 g of TAU before exercise did not enhance MFO, FATmax, or TTE. However, it did increase the oxygen cost of running fixed intensities in recreationally trained endurance runners
... A synergistic outcome that combines high rates of carbohydrate oxidation with the retention of an enhanced capacity for fat oxidation provides a means of preventing glycogen depletion and hypoglycaemia, which would otherwise limit the performance in keto-adapted individuals in prolonged endurance performance (Cox, et al., 2010), as well as influencing performance through central nervous system-based mechanisms (Maunder, Kilding, & Plews, 2018;Stellingwerff & Cox, 2014). Whilst there is a growing body of research examining the impact of ketogenic diets on endurance performance, little work has been conducted in the context of ultra-endurance performance, despite the increased importance of fat oxidation in longer exercise formats (Frandsen, Vest, Larsen, Dela, & Helge, 2017) making it a more promising area of research in the context of ketogenic diets. ...
... It is also important to note that fat oxidation was greater during the two day feeding condition notwithstanding carbohydrate supplementation, supporting the previous research showing that fat oxidation can remain elevated after a period of keto-adaptation despite singular acute carbohydrate ingestion (Carey, et al., 2001;Lambert, et al., 2001). It is clear that fat oxidation was maintained at high rates and this enhanced ability to oxidise fat is particularly beneficial during ultra-endurance exercise (Frandsen, et al., 2017), thus a ketogenic dietary intervention may be useful for athletes looking to spare muscle glycogen over ultra-endurance activities. Future research should look to study this detail in more controlled settings to determine the level of the reduction in fat oxidation following carbohydrate supplementation. ...
Article
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Ketogenic dietary interventions cause a dramatic increase in fat oxidation, with a growing body of research indicating prolonged ketogenic diets do not impair exercise performance. However, there is neither strong evidence in support of such a strategy. Over prolonged endurance events, the need for carbohydrates becomes increasingly important to prevent glycogen depletion and hypoglycaemia. A case study methodology was used to examine the response of an ultra-endurance runner with experience of events ranging from 60 to 161km (age: 37; stature: 184cm; mass: 80.2±0.8kg; 56.5ml/kg/min; mean training volume 37km/week) to three identical 67km field tests following an 8-week ketogenic dietary intervention. Supplementation protocols comprised an acute carbohydrate feeding on the day of competition (74g carbohydrate [0.92g/kg pre-race], 310g [3.85g/kg] during race), in addition to a condition comprising an acute feed as well as a two day of carbohydrate feed (200g carbohydrate [2.5g/kg] in two day feed, 44g carbohydrate [0.54g/kg pre-race], 310g [3.85g/kg] during race), prior to the event and these were compared to baseline event where no carbohydrate was consumed, within race feeding restricted to low carbohydrate options. Compared to baseline (05:58:47 [hours:minutes:seconds]), the 67km time trial improved in both carbohydrate feeding conditions, with greater performance improvements after acute consumption compared to the two-day feed (05:36:59 vs. 05:42:01). Rate of fat oxidation during 0-15km and 40-45km of the acute condition time trial decreased compared to baseline (0.95±0.32g/min, 0.42±0.24g/min vs. 1.20±0.34g/min, 0.89±0.02g/min), and was greatest during the two-day feed condition (1.52±0.30g/min, 1.37±0.34g/min). Carbohydrate feeding impacted substrate metabolism and improved time to complete ultra marathon performance in a ketogenic athlete emphasising the importance of carbohydrates as a fuel for exercise performance. More research is required to determine the efficacy of this strategy within ketogenic athletic populations, as well as investigating optimal ketogenic dietary practices and carbohydrate supplementation protocols.
... This is a consequence of the glycogensparing hypothesis developed based on pioneering work by the groups of Bergström, Hultman, and Costill in the 1960s and 70s. [1][2][3] Research has typically focused on endurance sports when investigating the relationship between fat oxidation and performance with indications of peak fat oxidation (PFO) and the intensity eliciting PFO (Fatmax) being positively associated with performance in prolonged endurance events, [4][5][6] whereas diet-or training-induced increases in fat oxidation during exercise have equivocal effects on endurance performance. [7][8][9][10] Interestingly, a large cross-sectional study by Randell and colleagues 11 showed that PFO and Fatmax in male football players and other team sport athletes were equal to and possibly higher than previously reported in endurance athletes. ...
... Together, this implies that PFO may be important for physical performance in football, as previously proposed as a determinant of prolonged endurance performance. 4 However, physical performance in football, as in any other team sport, is challenging to assess due to the complex dynamics within and between matches caused by technical and tactical aspects of the sport. ...
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Purpose In Football, the high‐intensity running bouts during matches are considered decisive. Interestingly, recent studies showed that peak fat oxidation rates (PFO) are higher in football players than other athletes. This study aimed to investigate whether PFO increases following a pre‐season. Secondarily, and due to COVID‐19, we investigated whether PFO is related to the physical performance in a subgroup of semi‐professional male football players. Methods Before and after 8 weeks of pre‐season training, 42 sub‐elite male football players (18 semi‐professionals and 24 non‐professionals) had a dual‐energy x‐ray absorptiometry scan and performed a graded exercise test on a treadmill for the determination of PFO, the exercise intensity eliciting PFO (Fatmax) and peak oxygen uptake (V̇O2peak). Additionally, the semi‐professional players performed a Yo‐Yo Intermittent Recovery Test level 2 (YYIR2) before and after pre‐season training to determine football‐specific running performance. Results PFO increased by 11 ± 10% (mean ± 95% CI), p = 0.031, and V̇O2peak increased by 5 ± 1%, p < 0.001, whereas Fatmax was unchanged (+12 ± 9%, p = 0.057), following pre‐season training. PFO increments were not associated with increments in V̇O2peak (Pearson's r² = 0.00, p = 0.948) or fat‐free mass (FFM) (r² = 0.00, p = 0.969). Concomitantly, YYIR2 performance increased in the semi‐professional players by 39 ± 17%, p < 0.001, which was associated with changes in V̇O2peak (r² = 0.35, p = 0.034) but not PFO (r² = 0.13, p = 0.244). Conclusions PFO, V̇O2peak, and FFM increased following pre‐season training in sub‐elite football players. However, in a subgroup of semi‐professional players, increments in PFO were not associated with improvements in YYIR2 performance nor with increments in V̇O2peak and FFM.
... Key training adaptations obtained by responders to regular moderate-intensity continuous exercise are mitochondrial biogenesis [2], an increase in maximal oxygen uptake [3], an increase in skeletal muscle capillarization [4] and enhanced exercise-induced whole-body fat oxidation [5]. In male ironman athletes, maximal fat oxidation and peak oxygen consumption showed significant negative correlations with the ironman race time [6]. The observation by Frandsen et al. [6] indicates the importance for whole-body fat oxidation during ultra-endurance events. ...
... In male ironman athletes, maximal fat oxidation and peak oxygen consumption showed significant negative correlations with the ironman race time [6]. The observation by Frandsen et al. [6] indicates the importance for whole-body fat oxidation during ultra-endurance events. Ultra-endurance athletes may benefit from enhanced whole-body fat oxidation during racing events by attenuating the rate of glycogen utilization. ...
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Physical training for ultra-endurance running provides physiological adaptations for exercise-induced substrate oxidation. We examined the effects of New Zealand blackcurrant (NZBC) extract on running-induced metabolic and physiological responses in a male amateur ultra-endurance runner (age: 40 years, body mass: 65.9 kg, BMI: 23.1 kg·m−2, body fat: 14.7%, V˙O2max: 55.3 mL·kg−1·min−1, resting heart rate: 45 beats·min−1, running history: 6 years, marathons: 20, ultra-marathons: 28, weekly training distance: ~80 km, weekly running time: ~9 h). Indirect calorimetry was used and heart rate recorded at 15 min intervals during 120 min of treadmill running (speed: 10.5 km·h−1, 58% V˙O2max) in an environmental chamber (temperature: ~26 °C, relative humidity: ~70%) at baseline and following 7 days intake of NZBC extract (210 mg of anthocyanins·day−1) with constant monitoring of core temperature. The male runner had unlimited access to water and consumed a 100-kcal energy gel at 40- and 80 min during the 120 min run. There were no differences (mean of 8, 15 min measurements) for minute ventilation, oxygen uptake, carbon dioxide production and core temperature. With NZBC extract, the respiratory exchange ratio was 0.02 units lower, carbohydrate oxidation was 11% lower and fat oxidation was 23% higher (control: 0.39 ± 0.08, NZBC extract: 0.48 ± 0.12 g·min−1, p < 0.01). Intake of the energy gel did not abolish the enhanced fat oxidation by NZBC extract. Seven days’ intake of New Zealand blackcurrant extract altered exercise-induced substrate oxidation in a male amateur ultra-endurance runner covering a half-marathon distance in 2 h. More studies are required to address whether intake of New Zealand blackcurrant extract provides a nutritional ergogenic effect for ultra-endurance athletes to enhance exercise performance.
... These absolute rates of fat oxidation are of the same magnitude as those reported in cross-sectional studies of athletes who have undertaken such dietary treatments for > 8 mo [25,26]. Because we used an event-specific 4-stage graded exercise test that is widely employed in the testing of high performance athletes [52], rather than the cycling/ treadmill running fat max test with a larger number of separate work intensities [53,54], we were unable to directly measure the exercise intensity at which maximal rates of fat oxidation (Fat max ) occur. However, it is likely that our intervention would have shifted Fat max from the typical~50-65% of peak aerobic capacity to values of~65-75% VO 2 max, as demonstrated in populations with longer-term keto-adaptation [26]. ...
... Increased rates of fat oxidation during exercise are a hallmark of endurance training and offer the advantage of making better use of a fuel substrate found in relatively unlimited amounts in even the leanest endurance athlete [25]. Furthermore, we appreciate that a capacity for high rates of fat oxidation in fasted but non-adapted athletes in a Fat max test may correlate with race performance, as has been recently reported in ultra-endurance triathletes [54]. This finding is consistent with the model we have used to explain our study findings, if we consider that rates of fat oxidation might be a proxy for absolute work capacity and mitochondrial mass in one setting, but that competition outcomes are achieved with different nutritional strategies. ...
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Introduction We repeated our study of intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) in world-class endurance athletes, with further investigation of a “carryover” effect on performance after restoring CHO availability in comparison to high or periodised CHO diets. Methods After Baseline testing (10,000 m IAAF-sanctioned race, aerobic capacity and submaximal walking economy) elite male and female race walkers undertook 25 d supervised training and repeat testing (Adapt) on energy-matched diets: High CHO availability (8.6 g∙kg⁻¹∙d⁻¹ CHO, 2.1 g∙kg⁻¹∙d⁻¹ protein; 1.2 g∙kg⁻¹∙d⁻¹ fat) including CHO before/during/after workouts (HCHO, n = 8): similar macronutrient intake periodised within/between days to manipulate low and high CHO availability at various workouts (PCHO, n = 8); and LCHF (<50 g∙d⁻¹ CHO; 78% energy as fat; 2.1 g∙kg⁻¹∙d⁻¹ protein; n = 10). After Adapt, all athletes resumed HCHO for 2.5 wk before a cohort (n = 19) completed a 20 km race. Results All groups increased VO2peak (ml∙kg⁻¹∙min⁻¹) at Adapt (p = 0.02, 95%CI: [0.35–2.74]). LCHF markedly increased whole-body fat oxidation (from 0.6 g∙min⁻¹ to 1.3 g∙min⁻¹), but also the oxygen cost of walking at race-relevant velocities. Differences in 10,000 m performance were clear and meaningful: HCHO improved by 4.8% or 134 s (95% CI: [207 to 62 s]; p < 0.001), with a trend for a faster time (2.2%, 61 s [-18 to +144 s]; p = 0.09) in PCHO. LCHF were slower by 2.3%, -86 s ([-18 to -144 s]; p < 0.001), with no evidence of superior “rebound” performance over 20 km after 2.5 wk of HCHO restoration and taper. Conclusion Our previous findings of impaired exercise economy and performance of sustained high-intensity race walking following keto-adaptation in elite competitors were repeated. Furthermore, there was no detectable benefit from undertaking an LCHF intervention as a periodised strategy before a 2.5-wk race preparation/taper with high CHO availability. Trial registration Australia New Zealand Clinical Trial Registry: ACTRN12619000794101.
... During sports wherein the use of limited stored energy substrates is important, increasing fat oxidation (FATOX) could be important to preserve endogenous carbohydrate stores. For example, the ability to use fat during exercise is positively associated with performance in an Ironman Triathlon in men (Frandsen et al., 2017) and women (Vest et al., 2018). Furthermore, body composition also influences FATOX during exercise, with a higher body fat percentage increasing utilization of fat (Goodpaster et al., 2002). ...
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New Zealand black currant extract (NZBC) has been shown to increase fat oxidation during exercise and decrease the postexercise blood pressure in men and women. The change in fat oxidation by NZBC has also been shown to be correlated to body composition in men and women. There has never been a comparison of sex responses within the same study. Twenty-two participants (11 men and 11 women, age: 29 ± 8 years, maximal oxygen uptake: 44 ± 9 ml·kg ⁻¹ ·min ⁻¹ , body fat: 18% ± 6%) had resting blood pressure measured for 2 hr (no exercise). In a double-blind, placebo-controlled (PLA), randomized crossover design, participants completed 1 hr of treadmill exercise at 50% maximal oxygen uptake with expired gas measurement, followed by 2-hr resting blood pressure measurement with 7 days of NZBC or PLA. Average fat oxidation was different between the conditions (NZBC: 0.27 ± 0.11 g/min, PLA: 0.21 ± 0.12 g/min, p < .001), but the response between men and women was not different. When combined, there was no relationship ( p > .05) between body fat percentage and change in fat oxidation ( r = −.079), with men also demonstrating no relationship ( r = −.069), although women did demonstrate a relationship ( r = .691, p < .05). In the 2-hr rest, systolic pressure delta change was larger with NZBC than PLA (no exercise vs. NZBC: −5.5 ± 5.4 mmHg vs. no exercise vs. PLA: −2.9 ± 5.1 mmHg, p < .001) but was not different between men and women. A 7-day intake of NZBC extract increases fat oxidation during moderate-intensity exercise and decreases postexercise blood pressure in men and women. The magnitude of change in fat oxidation in women is correlated to body fat percentage.
... Over 20% higher lipid oxidation was noticed in the group of trained cycling females and experienced ultra-endurance runner in both cases after 7 days of supplementation [66,77]. Lipid oxidation has previously been considered to enhance exercise capacity among 34 healthy male volunteers participating in the Copenhagen Ironman Competition [88]. The period of 7-day supplementation was also found to be effective in improving repeated cycling performance (dose 300 mg/day), climbing time and endurance (600 mg/day), as well as muscle oxygenation [65,70,71]. ...
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Numerous studies have documented that high-intensity or prolonged exercise is associated with increased oxidative stress and modification of antioxidant status. Polyphenol-rich dietary supplements seem to be the compounds that can upregulate the endogenous antioxidant defense system and consequently prevent muscle damage, support recovery. As berry fruits are at the top of the list of the richest polyphenol food sources, supplements containing berries have become the subject of interest in the context of counteracting exercise-induced oxidative stress and the development of cardiovascular diseases. The purpose of this review is to summarize current knowledge on the effects of berry-derived polyphenol supplementation on exercise-induced oxidative stress and cardiovascular health in physically active individuals. Based on the available literature, blackcurrant supplementation, with its richest version being New Zealand blackcurrant extract, is the most commonly explored berry fruit, followed by chokeberries and blueberries. Although several studies have documented the significant and beneficial influence of berry-derived supplements on redox status and cardiovascular response, some inconsistencies remain. The presented findings should be interpreted with caution due the limited number of available studies, particularly with the participation of physically active individuals. Further research is needed to reveal more comprehensive and accurate data concerning the impact of berry-derived supplements on exercise-induced outcomes taking into account the type of supplement, time of administration, and dosage.
... Theoretical models based on a world-class triathlete cycling at 313 W and running at 14.7 km · h −1 during competition estimates a range in "possible" oxidation rate of ∼2.0 to 3.7 g carbohydrates·min −1 and 0.6 to 1.2 g fat·min −1 , 3 with ∼1.0 being the highest individual value in a mixed cohort of fasted full-distance triathles. 4 During the loops in the present case study, cycling power (∼330 W + initial surge at 400 W) and running speed (∼16.4 km · h −1 ) were higher than in the theoretical model. Using the same equation/estimate as Maunder et al, 3 and accounting for changes in power and speed, oxidation of carbohydrate was 4.1 g·min −1 on average (range 3.1-5.4) ...
Article
Purpose: To investigate metabolism and exercise economy during prolonged race simulation (>4 h) in a world-class, full-distance triathlete to help guide/adjust strategies for training, nutrition, hydration, and thermoregulation. Methods: Two experimental race-simulation days, designed to mimic the demands of a full-distance triathlon, were executed by a world-class male triathlete (MD; 25 y, body weight 82 kg, V˙O2max 6.2 L·min-1, blood lactate threshold ∼410 W, and 18 km · h-1 in cycling and running) who at the time ranked second in the world. Race simulation was performed 23 and 10 days prior to competing in Challenge Roth 2023, where MD won in a new world record/best time (7:24:40 h:min:s). Both test days lasted ∼4 to 5 hours with physiologic testing every ∼45 to 60 minutes in a "stationary" setting during cycling on a direct-mount trainer (∼320 W) and treadmill running (16 km · h-1), enabling gas exchange measurements (V˙O2 and respiratory exchange ratio) and other physiologic measurements of interest (ie, core temperature and heart rate). This was combined with "real activity" as repeated loops in an open-air field setting at expected race pace in swimming, biking, and running. Results: V˙O2 was maintained at ∼4.2 L·min-1, with carbohydrates being the dominant fuel for oxidation as respiratory exchange ratio values dropped from ∼1 at the start of cycling to ∼0.85 during running. Cycling economy was stable, whereas a slight impairment in running economy occurred over time. Conclusion: High aerobic energy turnover and stable exercise economy can be maintained in a world-class record-breaking triathlete for prolonged period of time (+4 h), showcasing the importance of both for success in competition.
... It seems clear that physiological resilience to fatigue is a key determinant of endurance exercise performance [1], but also that fatigue is affected by a complex interplay among multiple factors that can vary across exercise conditions and affect individuals differently, depending on the type of stress and physiological differences within individuals [16][17][18]. In relation to prevention of fatigue provoked by glycogen depletion or by metabolic disturbance of muscle homeostasis, there has been a particular focus on maximal fat oxidation and power output at different metabolic thresholds as factors of relevance to fatigue resistance [19][20][21]. However, most laboratory studies lack ecological validity and fail to link the capacity for fat oxidation or other traditional measures of aerobic exercise performance with increased durability in race-like conditions [1,[22][23][24][25]. ...
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Fatigue resistance is vital for success in elite road cycling, as repeated, intense efforts challenge the athletes' ability to sustain peak performance throughout prolonged races. The present study combined recurrent performance testing and physiological measures during 6 h simulated racing with laboratory testing to investigate factors influencing fatigue resistance. Twelve male national elite cyclists (25 ± 3 years; 76 ± 6 kg and VO2max of 5.2 ± 0.5 L/min) completed incremental power and maximal fat oxidation tests. Subsequently, they underwent field testing with physiological measures and fatigue responses evaluated through peak sprint power and 5 km time trial (TT) testing after 0, 2, 4, and 6 h of exercise. Peak power declined from 1362 ± 176 W in first sprint to 1271 ± 152 W after 2 h (p < 0.01) and then stabilized. In contrast, TT mean power gradually declined from 412 ± 38 W in the first TT to 384 ± 41 W in the final trial, with individual losses ranging from 2% to 14% and moderately correlated (r² = 0.45) to accumulated exercise time above lactate threshold. High carbohydrate intake (~90 g/h) maintained blood glucose levels, but post‐TT [lactate] decreased from 15.1 ± 2 mM to 7.1 ± 2.3 mM, while fat oxidation increased from 0.7 ± 0.3 g/min at 0 h to 1.1 ± 0.1 g/min after 6 h. The study identifies fatigue patterns in national elite cyclists. Peak sprint power stabilized after an initial impairment from 0 to 2 h, while TT power gradually declined over the 6 h simulated race, with increased differentiation in fatigue responses among athletes.
... However, in males and females that were performance-matched for 42.2 km running, the better 90 km performance in females was not associated with enhanced fat metabolism [38]. Interestingly, for an Ironman (i.e., 3.9 km (2.4 mile) swimming, 180.2 km (112 mile) cycling, and 42.2 km (26.2 mile) running), peak fat oxidation in females [39] and males [40] was associated with race time. The importance of exercise-induced fat oxidation for the race time of a Marathon des Sables athlete is not known. ...
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Four weeks before competition in the 2023 Marathon des Sables, a 6-stage, ~250 km running event in the Sahara Desert, we examined the effects of a 7-day intake of New Zealand blackcurrant extract (210 mg anthocyanins per day) on 1 h treadmill running-induced physiological and metabolic responses in the heat (~34 °C, relative humidity: ~30%) in non-acclimatized amateur female and male athletes (age: 23, 38 yrs, BMI: 24.2, 28.4 kg·m−2, body fat%: 29.2, 18.8%, V˙O2max: 50.1, 52.1 mL·kg−1·min−1). During the 1 h run at 50%V˙O2max (speed female: 7.3, male: 7.5 km·h−1), indirect calorimetry was used, and heart rate was recorded at 15 min intervals with core temperature monitoring (0.05 Hz). The 1 h runs took place 3 h after a light breakfast and 2 h after intake of the final dose of New Zealand blackcurrant extract with water allowed ad libitum during the run. The New Zealand blackcurrant extract had no effects on the female athlete. The respiratory exchange ratio (RER) of the female athlete in the non-supplement control condition was 0.77 ± 0.01, indicating an existing ~77% contribution of fat oxidation to the energy requirements. In the male athlete, during 1 h of running, fat oxidation was higher by 21% (p < 0.01), carbohydrate oxidation was 31% lower (p = 0.05), RER was 0.03 units lower (p = 0.04), and core temperature was 0.4 °C lower (p < 0.01) with no differences for heart rate, minute ventilation, oxygen uptake, and carbon dioxide production for the New Zealand blackcurrant condition compared to the non-supplement control condition. Seven-day intake of New Zealand blackcurrant extract (210 mg anthocyanins per day) provided beneficial physiological and metabolic responses during exertional heat stress by 1 h of indoor (~34 °C) treadmill running in a male Marathon des Sables athlete 4 weeks before competition. Future work is required to address whether New Zealand blackcurrant provides a nutritional ergogenic effect for Marathon des Sables athletes during long-duration running in the heat combined with personalized nutrition.
... Indeed, fat oxidation rates during submaximal exercise have been associated with durability of the heavy-to-severe-intensity transition and severe-intensity performance (Spragg et al. 2023b). The capacity for fat oxidation during exercise has been quantified using the peak fat oxidation rate (PFO) observed during an incremental exercise test (Maunder et al. 2018(Maunder et al. , 2023, and PFO has been related to endurance performance outcomes (Frandsen et al. 2017;Maunder et al. 2022). However, the relationship between PFO and the effect of prolonged exercise on severeintensity performance has not been assessed. ...
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Purpose Power output at the moderate-to-heavy-intensity transition decreases during prolonged exercise, and resilience to this has been termed ‘durability’. The purpose of this study was to assess the relationship between durability and the effect of prolonged exercise on severe-intensity performance, and explore intramuscular correlates of durability. Methods On separate days, 13 well-trained cyclists and triathletes (V̇O2peak, 57.3 ± 4.8 mL kg⁻¹ min⁻¹; training volume, 12 ± 2.1 h week⁻¹) undertook an incremental test and 5-min time trial (TT) to determine power output at the first ventilatory threshold (VT1) and severe-intensity performance, with and without 150-min of prior moderate-intensity cycling. A single resting vastus lateralis microbiopsy was obtained. Results Prolonged exercise reduced power output at VT1 (211 ± 40 vs. 198 ± 39 W, ∆ -13 ± 16 W, ∆ -6 ± 7%, P = 0.013) and 5-min TT performance (333 ± 75 vs. 302 ± 63 W, ∆ -31 ± 41 W, ∆ -9 ± 10%, P = 0.017). The reduction in 5-min TT performance was significantly associated with durability of VT1 (rs = 0.719, P = 0.007). Durability of VT1 was not related to vastus lateralis carnosine content, citrate synthase activity, or complex I activity (P > 0.05). Conclusion These data provide the first direct support that durability of the moderate-to-heavy-intensity transition is an important performance parameter, as more durable athletes exhibited smaller reductions in 5-min TT performance following prolonged exercise. We did not find relationships between durability and vastus lateralis carnosine content, citrate synthase activity, or complex I activity.
... In line with our hypothesis, we observed that the absolute MFO rate was lowered with age in the three BMI and fitness level matched groups. The absolute MFO rate is closely related to fitness level as indicated by the correlation between V̇O 2max and MFO rate ( Figure 2A), and as previously demonstrated in the literature (Frandsen et al., 2017;Venables et al., 2005). We recruited trained women with cardiorespiratory fitness levels well above average within their age group when compared to a large Danish representative sample (Eriksen et al., 2016). ...
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The fat oxidation capacity is higher in young compared to elderly subjects and higher in premenopausal compared to postmenopausal women, but the influence of age on maximal fat oxidation (MFO) is not clear. Therefore, this study aimed to evaluate MFO (g/min) across the lifespan of trained adult women. In total, 36 healthy trained women were recruited into three groups: (n = 12), young (27 ± 3 years, mean ± SD) premenopausal, middle‐aged (57 ± 3 years), and older (71 ± 2 years) postmenopausal women and all had a body mass index <25 kg/m². After an overnight fast, body composition was determined by dual‐energy X‐ray absorptiometry, and blood samples were obtained. A FATmax‐test was performed on a cycle ergometer, and MFO was calculated from the pulmonary V̇O2 and V̇CO2 measured by indirect calorimetry. The absolute MFO was significantly higher in young (0.40 ± 0.07 g/min) compared to both middle‐aged (0.33 ± 0.07 g/min) (p = 0.035) and old (0.25 ± 0.05 g/min) women (p < 0.001). Absolute MFO was higher in middle‐aged compared to old women (p = 0.018). Relative MFO (MFO/LBM, mg/min/LBM) was higher in young (8.39 ± 1.62 mg/min/LBM) compared to old (6.16 ± 1.14 mg/min/LBM) women (p = 0.004). A significant linear relationship was observed between absolute MFO and age (R² = 0.41; p < 0.001), V̇O2max (R² = 0.40; p < 0.001), and LBM (R² = 0.13; p = 0.033), respectively, and between relative MFO and fat mass (R² = 0.12; p = 0.04). In conclusion, the maximal capacity to oxidize fat is attenuated with age in trained women. Furthermore, postmenopausal middle‐aged women have higher absolute MFO compared to older women, and this implies that it is age per se and not a change in estrogen availability that leads to lower absolute MFO.
... Indeed, a well-trained endurance athlete is well known to have a high MFO and a declining FATox rate at exercise intensities of approximately 80%-85% of maximal oxygen consumption ( _ VO 2 max) (Hurley et al., 1986;Martin et al., 1993;Phillips et al., 1996;Bircher and Knetchle, 2004). Moreover, fat oxidation capacity has been correlated with performance in ironman triathletes, which take part in ultra-endurance events (Frandsen et al., 2017). A recent review showed normative percentile values for MFO and FATmax in different subject populations in order to contextualize individually measured values and define the fat oxidation capacity of given research cohorts (Maunder et al., 2018). ...
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Introduction: Post-acute sequelae of SARS-CoV-2 infection (PASC) presents a spectrum of symptoms following acute COVID-19, with exercise intolerance being a prevalent manifestation likely linked to disrupted oxygen metabolism and mitochondrial function. This study aims to assess maximal fat oxidation (MFO) and exercise intensity at MFO (FATmax) in distinct PASC subject groups and compare these findings with normative data. Methods: Eight male subjects with PASC were involved in this study. The participants were divided into two groups: “endurance-trained” subjects ( V ˙ O 2 max > 55 mL/min/kg) and “recreationally active” subjects ( V ˙ O 2 max < 55 mL/min/kg). Each subject performed a graded exercise test until maximal oxygen consumption ( V ˙ O 2 max ) to measure fat oxidation. Subsequently, MFO was assessed, and FATmax was calculated as the ratio between V ˙ O 2 at MFO and V ˙ O 2 max. Results: The MFO and FATmax of “endurance-trained” subjects were 0.85, 0.89, 0.71, and 0.42 and 68%, 69%, 64%, and 53%, respectively. Three out of four subjects showed both MFO and FATmax values placed over the 80th percentile of normative data. The MFO and FATmax of “recreationally active” subjects were 0.34, 0.27, 0.35, and 0.38 and 47%, 39%, 43%, and 41%, respectively. All MFO and FATmax values of those subjects placed below the 20th percentile or between the 20th and 40th percentile. Discussion: Significant differences in MFO and FATmax values between ‘endurance-trained’ and “recreationally active” subjects suggest that specific endurance training, rather than simply an active lifestyle, may provide protective effects against alterations in mitochondrial function during exercise in subjects with PASC.
... Maximal fat oxidation rate (MFO) during exercise is a remarkable physiological indicator associated with metabolic flexibility/body weight loss and endurance performance, such as Ironman triathlon (Frandsen et al. 2017). Interestingly, previous investigations have found that MFO can be increased just by the oral intake of caffeine in doses between 3 and 6 mg/kg of body mass . ...
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Purpose Caffeine is a stimulant with well-recognized performance and metabolic benefits, however, there is a lack of studies investigating the time-of-day influence in the properties of caffeine to enhance fat oxidation in women. Thus, the aim of the present study was to evaluate the influence of the time of the day on the effect of caffeine on the maximal rate of fat oxidation during aerobic exercise in trained women. Methods Fourteen female athletes (25.5 ± 7.1 years) took part in a randomized, crossover, double-blind study. All participants undertook four different experimental trials combining the ingestion of 3 mg/kg caffeine and a placebo either in the morning (8.00–10.00 h) and in the evening (17.00–19.00 h) realizing an incremental test on a cycle ergometer with 3 min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Substrate oxidation rates were measured by indirect calorimetry. In each trial, the maximum rate of fat oxidation (MFO) and the intensity that elicited MFO (Fatmax) were measured. Results In comparison to placebo, MFO was significantly higher with caffeine both in the morning (0.24 ± 0.13 vs 0.30 ± 0.14 g/min; p < 0.001; ES = 0.79) and in the evening (0.21 ± 0.08 vs 0.28 ± 0.10 g/min; p = 0.002; ES = 0.72). No time-of-day effect on the capacity of caffeine to increase MFO was found (all p = 0.336) Conclusion The intake of 3 mg/kg of caffeine increased the use of fat as a fuel during exercise independently of the time-of-day in trained women. Trial registration The study was registered in ClinicalTrials.gov with the following ID: NCT05880186 by 15 May 2023.
... A study found that childhood ALL survivors had lower ɺ VO 2 peak, compared to the healthy population 12 which could affect our associations between ɺ VO 2 peak and MFO. It has been hypothesized that associations between MFO and ɺ VO 2 peak are only visible when comparing heterogenous groups 61,62 and that the level of physical activity can influence participants' MFO and Fat max . 61,63 In our study, physical activity levels were not associated with fat oxidation, suggesting that other variables of interest may have impacted childhood ALL survivors' substrate oxidation. ...
Article
Children with acute lymphoblastic leukemia (ALL) are at high risk of developing long-term cardiometabolic complications during their survivorship. Maximal fat oxidation (MFO) is a marker during exercise of cardiometabolic health, and is associated with metabolic risk factors. Our aim was to characterize the carbohydrate and fat oxidation during exercise in childhood ALL survivors. Indirect calorimetry was measured in 250 childhood ALL survivors to quantify substrate oxidation rates during a cardiopulmonary exercise test. A best-fit third-order polynomial curve was computed for fat oxidation rate (mg/min) against exercise intensity (V̇O2peak) and was used to determine the MFO and the peak fat oxidation (Fatmax). The crossover point was also identified. Differences between prognostic risk groups were assessed (ie, standard risk [SR], high risk with and without cardio-protective agent dexrazoxane [HR + DEX and HR]). MFO, Fatmax and crossover point were not different between the groups (p = .078; p = .765; p = .726). Fatmax and crossover point were achieved at low exercise intensities. A higher MFO was achieved by men in the SR group (287.8 ± 111.2 mg/min) compared to those in HR + DEX (239.8 ± 97.0 mg/min) and HR groups (229.3 ± 98.9 mg/min) (p = .04). Childhood ALL survivors have low fat oxidation during exercise and oxidize carbohydrates at low exercise intensities, independently of the cumulative doses of doxorubicin they received. These findings alert clinicians on the long-term impact of cancer treatments on childhood ALL survivors' substrate oxidation.
... Since the first triathlon competitions, this endurance event has spread worldwide, attracting thousands of endurance-trained athletes. All competitions and their distances are regulated by the World Triathlon, the highest organisation in the world that oversees and regulates official triathlon competitions [4]. ...
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Background: Nutrition in sport is a priority; it is the basis for maintaining optimal health and a prerequisite for the high performance necessary for competitions. The aim of this study was to assess low energy availability and its possible consequences among female triathletes by using the Low Energy Availability in Females Questionnaire (LEAF-Q). Methods: The study involved 30 female triathetes. The LEAF-Q was used in the study. An analysis of the body composition was carried out with the seca device mBCA 515 medical Body Composition Analyzer. Results: Of the 30 female triathletes studied, 23.3% had a monthly cycle disorder, defined as an amenorrhea state for more than 90 days. No differences were found in injury rates or training days lost to injury due to menstrual disturbances. Menstruation changes were significantly greater due to increases in exercise intensity, frequency, and duration in the group experiencing menstrual disturbances (85.7 [95% CIs: 42.1-99.6] vs. 8.7 [95% CIs: 1.1-28.0]). The menstrual disorder group had a greater incidence of their periods stopping for more than 3 months than the group without menstrual disturbances. Conclusions: The female triathletes did not show abnormalities in body weight or composition, and these were not related to the incidence of menstrual disturbances. However, 20% of the triathletes either had, at the time of the study, or had had in the past monthly cycle disorders that could indicate an immediate risk of low energy availability. The LEAF-Q identified 10% of the triathletes as at risk (score > 8) of low energy availability and the physiological and performance consequences related to relative energy deficiency in sports (RED-S).
... Additionally, MFO added substantial explanation of variance to stepwise regression models of all TT, despite lipid oxidation being likely neglectable during these intensities. Multiple studies however, have shown MFO is an expression of endurance training status (Maunder et al., 2018) and especially relevant during ultra-endurance running (Frandsen et al., 2017;Pastor et al., 2022). Athletes with higher endurance performance capacity display higher MFO, presumably due to higher absolute training volume in the low-intensity domain. ...
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Purpose: Aim of this thesis was the identification and critical review of traditional and novel physiological and performance parameters for different threshold concepts and 1-, 2-, 3-km time-trial (TT) running. Methods: Physiological tests and TTs were carried out in a group of sprinters (n = 6), middle- and long-distance (n = 16) and ultra-runners (n = 3). Relationship between TT performance and physiological (V̇O2max, RE, %V̇O2max, MFO, V̇Lamax, dLa100) as well as performance parameters (vV̇O2max, vMLSS, CV, Fatmax, D’, ASR, SRR) was assessed, Additionally, correlations between all investigated parameters and agreement between velocity at different threshold concepts (vOBLA, vMLSS and CV) was analyzed. Results: V̇O2max and CV presented the strongest positive relationship with 2- (r = 0.81, r = 0.84) and 3-km (r = 0.89, r = 0.98) TT performance among physiological and performance parameters respectively. V̇Lamax, La100, D’, ASR and SRR were positively correlated with sprint performance (r = 0.73, r = 0.54, r = 0.69, r = 0.56, r = 0.43) and negatively with 2- (r = -0.41, r = -0.46, r = -0.37, r = -0.71, r = -0.81) an 3-km (r = -0.50, r = -0.53, r = -0.62, r = -0.85, r = -0.91) TT performance and vMLSS r = -0.48, r = -0.51, r = -0.62, r = -0.79, r = -0.86). Correlations coefficients for 1-km TT were lower compared to 2- and 3-km. Strong agreement was found between threshold concepts (vMLSS – vOBLA: R2 = 0.94; vMLSS – CV: R2 = 0.83) and mean differences amounted to -0.08 and -0.49 m·s-1. Conclusion: Parameters linked to aerobic metabolism displayed the strongest relationship with TTs. While anaerobic variables correlated positively with sprint performance the relationships became increasingly negative with increasing distance of TT. It can be hypothesized that influence of anaerobic metabolism is in balance for maximal running efforts around three minutes. Efforts slower than this balance point might tend to benefit from anaerobic metabolism while longer efforts might be affected in a detrimental way. Prediction of TT and threshold velocity was more accurate through performance than physiological parameters. Based on these findings, novel parameters can complement traditional test variables in running. Deliberate and differential selection of test parameters is advised for performance prediction or physiological training prescription in running and depending on race distance.
... Splitting the results by sex, they found that maximal fat oxidation was a predictor of performance for men, but not for women, despite a significant correlation with performance for women as well. Maximal fat oxidation has also been shown to predict performance in other long-duration sports, such as Ironman triathlon (Frandsen et al., 2017;Vest et al., 2018). The effect of fat oxidation race in middle-distance and long-distance running performance has not received much attention in the literature. ...
Thesis
The objectives of this thesis were to investigate the performance determinants of trail running, and to evaluate the changes in running economy following prolonged endurance running exercise. First, we tested elite road and trail runners for differences in performance factors. Our results showed that elite trail runners are stronger than road runners, but they have greater cost of running when running on flat ground. In the second study, we evaluated the performance factors that predicted performance in trail running races of different distances, ranging from 40 to 170 km. We found that maximal aerobic capacity was a determinant factor of performance for races up to 100 km. Performance in shorter races, up to approximately 55 km, was also predicted by lipid utilization at slow speed, while performance in the 100 km race was also predicted by maximal strength and body fat percentage. The most important factors of performance for races longer than 100 km are still debated. We also tested the effects of trail running race distance on cost of locomotion, finding that cost of running increased after races up to 55 km, but not after races of 100-170 km. Finally, we tested the. effects of two different exercise modalities, cycling and running, on cost of locomotion, after 3 hours of intensity-matched exercise. Cost of locomotion increased more following cycling than running, and the change in cost of locomotion was related to changes in cadence and loss of force production capacity.
... The ability to effectively oxidize fat for fuel, represented by a lower RER, is important for metabolic health [14] and long-duration exercise performance [15,16], and many athletes attempt to manipulate substrate oxidation during exercise as part of a periodized nutrition and training plan [17,18]. However, managing substrate oxidation during exercise is challenged by the influence of both modifiable The easily measured and easily modifiable factors related to exercise such as exercise duration and intensity, daily macronutrient intake, and pre-and peri-exercise carbohydrate intake, can only explain roughly one-third of the variation in RER during exercise. ...
Article
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Background: Multiple factors influence substrate oxidation during exercise including exercise duration and intensity, sex, and dietary intake before and during exercise. However, the relative influence and interaction between these factors is unclear. Objectives: Our aim was to investigate factors influencing the respiratory exchange ratio (RER) during continuous exercise and formulate multivariable regression models to determine which factors best explain RER during exercise, as well as their relative influence. Methods: Data were extracted from 434 studies reporting RER during continuous cycling exercise. General linear mixed-effect models were used to determine relationships between RER and factors purported to influence RER (e.g., exercise duration and intensity, muscle glycogen, dietary intake, age, and sex), and to examine which factors influenced RER, with standardized coefficients used to assess their relative influence. Results: The RER decreases with exercise duration, dietary fat intake, age, VO2max, and percentage of type I muscle fibers, and increases with dietary carbohydrate intake, exercise intensity, male sex, and carbohydrate intake before and during exercise. The modelling could explain up to 59% of the variation in RER, and a model using exclusively easily modified factors (exercise duration and intensity, and dietary intake before and during exercise) could only explain 36% of the variation in RER. Variables with the largest effect on RER were sex, dietary intake, and exercise duration. Among the diet-related factors, daily fat and carbohydrate intake have a larger influence than carbohydrate ingestion during exercise. Conclusion: Variability in RER during exercise cannot be fully accounted for by models incorporating a range of participant, diet, exercise, and physiological characteristics. To better understand what influences substrate oxidation during exercise further research is required on older subjects and females, and on other factors that could explain additional variability in RER.
... Likewise, it is well known that Fatmax zone and muscle deoxygenation kinetics are associated [41], SmO 2 remains stable in the presence of fat oxidation and at the SmO 2 breakpoint where VT2 is entered one no longer consumes fat and is totally dependent on carbohydrate energy (Figure 1b). This is also a result of the subjects with better performance in endurance tests maintaining higher SmO 2 values during exercise than sprinting athletes [42]. ...
Article
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Use of muscle oxygen saturation (SmO2) has been validated as a performance factor during incremental exercise with portable near-infrared stereoscopy (NIRS) technology. However, there is little knowledge about the use of SmO2 to identify training zones. The objective of this study was to evaluate the metabolic zones by SmO2: maximum lipid oxidation zone (Fatmax), ventilatory thresholds (VT1 and VT2) and maximum aerobic power (MAP) during a graded exercise test (GXT). Forty trained cyclists and triathletes performed a GXT. Output power (W), heart rate (HR), oxygen consumption (VO2), energy expenditure (kcal/min) and SmO2 were measured. Data were analysed using the ANOVA test, ROC curves and multiple linear regressions. Significance was established at p ≤ 0.05. SmO2 decreases were observed from baseline (LB) to Fatmax (Δ = -16% p < 0.05), Fatmax to VT1 (Δ = -16% p < 0.05) and VT1 to VT2 (Δ = -45% p < 0.01). Furthermore, SmO2 together with weight, HR and output power have the ability to predict VO2 and energy expenditure by 89% and 90%, respectively. We conclude that VO2 and energy expenditure values can be approximated using SmO2 together with other physiological parameters and SmO2 measurements can be a complementary parameter to discriminate aerobic workload and anaerobic workload in athletes.
... A good fat oxidation capacity, combined with carbohydrate intake during endurance events, would allow an athlete to preserve more glycogen which can be used when the intensity increases, such as when a cyclist needs to respond to an acceleration or at the end of the race when the athletes are accelerating toward the finish line (Hall et al., 2016;Jeukendrup & Achten, 2001). Frandsen et al. (2017) found that the maximal fat oxidation of triathletes competing in an Ironman triathlon is related to their performance in this ultra-endurance event. Endurance athletes generally have a good fat oxidation capacity, but there are many ways an athlete can increase even more their fat oxidation capacity, such as doing long aerobic training, doing fasted training, training twice a day or by training with minimum or without carbohydrate intake (Hawley, 2014). ...
Article
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This study aimed to determine the effects of consuming a high fat solution (HFS) compared to a high carbohydrate solution (HCS) during a cycling effort on substrate oxidation, muscle oxygenation and performance with cyclists and triathletes. Thirteen men participated in this study (age: 30.4 ± 6.3 y; height: 178.7 ± 6.1 cm; weight: 74.9 ± 6.5 kg; V̇O2 peak: 60.5 ± 7.9 mlO2×kg-1×min-1). The solutions were isocaloric (total of 720 kcal) and were consumed every 20 minutes. Each solution of HFS contained 12.78 g of lipids, 1.33 g of carbohydrates and 0.67 g of proteins, and each solution of HCS contained 28 g of carbohydrates. We measured pulmonary oxygen consumption and skeletal muscle oxygenation, using a Near Infrared Spectrometer (NIRS) during a cycling effort consisting of 2 hours at 65 % of maximal aerobic power (MAP) followed immediately by a 3-minute time-trial (TT). We observed that the consumption of the HFS increased the rate of fat oxidation at the end of the sub-maximal effort (0.61 ± 0.14 vs 0.53 ± 0.17 g×min-1, p < 0.05). We have also shown that the HFS negatively affected the performance in the TT (mean Watts: HCS: 347.0 ± 77.4 vs HFS: 326.5 ± 88.8 W; p < 0.05) and the rating of perceived exertions during the sub-maximal effort (modified Borg Perceived Exertion scale: 1–10) (mean: 3.62 ± 0.58 for HCS vs 4.16 ± 0.62 for HFS; p < 0.05). We did not observe a significant effect of the acute consumption of the HFS compared to the HCS on muscle oxygenation during the cycling effort. Finally, we observed that cyclists who demonstrated a high skeletal muscle deoxygenation relative to their pulmonary oxygen consumption (DHHb/V̇O2) had a higher fat oxidation capacity (higher Fatmax). In conclusion, even though the consumption of HFS increased the rate of fat oxidation at the end of a sub-maximal effort, it did not affect muscle oxygenation and it negatively affected performance and perceived exertion during a time-trial and caused gastro-intestinal distress in some participants. Keywords: Fat oxidation, Skeletal muscle oxygenation, Lipid supplementation, Carbohydrate supplementation, Near Infrared Spectroscopy (NIRS), Cycling, Triathlon.
... Indeed, greater mitochondrial respiratory capacity is a common reported adaptation to endurance training (34), which is largely explained by augmentation of mitochondrial volume and not by a change in mitochondrial quality (54,55). In line with these findings, cross-sectional studies have shown that differences in fitness levels between active individuals and elite endurance athletes are largely related to differences in mitochondrial volume (56) and that a high whole body fat oxidation capacity, a key feature of elite endurance athletes (57), is related to mitochondrial volume and not to the intrinsic properties of mitochondria (58). Since the subjects of the present study were highly trained endurance athletes belonging to both the national and international elite, only modest changes in the mitochondrial volume were expected although training was intensified. ...
Article
Aim: The maintenance of healthy and functional mitochondria is the result of a complex mitochondrial turnover and herein quality-control program which includes both mitochondrial biogenesis and autophagy of mitochondria. The aim of this study was to examine the effect of an intensified training load on skeletal muscle mitochondrial quality control in relation to changes in mitochondrial oxidative capacity, maximal oxygen consumption and performance in highly trained endurance athletes. Methods: 27 elite endurance athletes performed high intensity interval exercise followed by moderate intensity continuous exercise 3 days per week for 4 weeks in addition to their usual volume of training. Mitochondrial oxidative capacity, abundance of mitochondrial proteins, markers of autophagy and antioxidant capacity of skeletal muscle were assessed in skeletal muscle biopsies before and after the intensified training period. Results: The intensified training period increased several autophagy markers suggesting an increased turnover of mitochondrial and cytosolic proteins. In permeabilized muscle fibers, mitochondrial respiration was ~20 % lower after training although some markers of mitochondrial density increased by 5-50%, indicative of a reduced mitochondrial quality by the intensified training intervention. The antioxidative proteins UCP3, ANT1, and SOD2 were increased after training, whereas we found an inactivation of aconitase. In agreement with the lower aconitase activity, the amount of mitochondrial LON protease that selectively degrades oxidized aconitase, was doubled. Conclusion: Together, this suggests that mitochondrial respiratory function is impaired during the initial recovery from a period of intensified endurance training while mitochondrial quality control is slightly activated in highly trained skeletal muscle.
... Although this trait is adaptable with training, around 65% of VO 2 max seems to be the ultimate ceiling, even for endurance athletes [9,45]. Additionally, PFO and Fat Max weakly correlated with ultra-endurance performance in males [46] and females [47]. The above studies validate that FA flux cannot support the OXPHOS in exercise on its own, and despite being substrate-efficient, it tells only a part of the story of the oxidative phenotype. ...
Article
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Mitochondria are popularly called the “powerhouses” of the cell. They promote energy metabolism through the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, which in contrast to cytosolic glycolysis are oxygen-dependent and significantly more substrate efficient. That is, mitochondrial metabolism provides substantially more cellular energy currency (ATP) per macronutrient metabolised. Enhancement of mitochondrial density and metabolism are associated with endurance training, which allows for the attainment of high relative VO2 max values. However, the sedentary lifestyle and diet currently predominant in the Western world lead to mitochondrial dysfunction. Underdeveloped mitochondrial metabolism leads to nutrient-induced reducing pressure caused by energy surplus, as reduced nicotinamide adenine dinucleotide (NADH)-mediated high electron flow at rest leads to “electron leak” and a chronic generation of superoxide radicals (O2−). Chronic overload of these reactive oxygen species (ROS) damages cell components such as DNA, cell membranes, and proteins. Counterintuitively, transiently generated ROS during exercise contributes to adaptive reduction-oxidation (REDOX) signalling through the process of cellular hormesis or “oxidative eustress” defined by Helmut Sies. However, the unaccustomed, chronic oxidative stress is central to the leading causes of mortality in the 21st century—metabolic syndrome and the associated cardiovascular comorbidities. The endurance exercise training that improves mitochondrial capacity and the protective antioxidant cellular system emerges as a universal intervention for mitochondrial dysfunction and resultant comorbidities. Furthermore, exercise might also be a solution to prevent ageing-related degenerative diseases, which are caused by impaired mitochondrial recycling. This review aims to break down the metabolic components of exercise and how they translate to athletic versus metabolically diseased phenotypes. We outline a reciprocal relationship between oxidative metabolism and inflammation, as well as hypoxia. We highlight the importance of oxidative stress for metabolic and antioxidant adaptation. We discuss the relevance of lactate as an indicator of critical exercise intensity, and inferring from its relationship with hypoxia, we suggest the most appropriate mode of exercise for the case of a lost oxidative identity in metabolically inflexible patients. Finally, we propose a reciprocal signalling model that establishes a healthy balance between the glycolytic/proliferative and oxidative/prolonged-ageing phenotypes. This model is malleable to adaptation with oxidative stress in exercise but is also susceptible to maladaptation associated with chronic oxidative stress in disease. Furthermore, mutations of components involved in the transcriptional regulatory mechanisms of mitochondrial metabolism may lead to the development of a cancerous phenotype, which progressively presents as one of the main causes of death, alongside the metabolic syndrome.
... During the past decade a large number of studies have been conducted using a similar methodological approach to measure MFO in 2 laboratories: (i) Xlab [Department of Biomedical Sciences at the University of Copenhagen, Copenhagen, Denmark (n = 276)]; and (ii) at the Sport and Health University Research Institute [University of Granada, Granada, Spain (n = 200)]. A total of 476 graded exercise tests to establish MFO were identified (Ara et al. 2011;Larsen et al. 2012;Dandanell et al. 2017aDandanell et al. , 2017bFrandsen et al. 2017Frandsen et al. , 2019Frandsen et al. , 2020aFrandsen et al. , 2020bVest et al. 2018;Amaro-Gahete et al. 2018, 2020. Subjects were divided into separate groups based on the following steps ( Fig. 1): ...
Article
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Fat oxidation decreases with age, yet no studies have previously investigated if aging affects the maximal fat oxidation rate (MFO) during exercise in men and women differently. We hypothesized that increased age would be associated with a decline in MFO and this would be more pronounced in women due to menopause, compared with men. In this cross-sectional study design, 435 (247/188, male/female) subjects of varying ages performed a DXA scan, a submaximal graded exercise test and a maximal oxygen uptake test, to measure MFO and cardiorespiratory fitness (CRF) by indirect calorimetry. Subjects were stratified into 12 groups according to sex (male/female), age (<45, 45–55 and >55 years), CRF (below average and above average). Women aged <45 years had a higher MFO relative to fat free mass (FFM) (mg/min/kg) compared with men, regardless of CRF. However, there were no differences in MFO (mg/min/kg FFM) between men and women, in the groups aged between 45–55 and >55 years. In summary, we found that women aged <45 years display a higher MFO (mg/min/kg FFM) compared with men and that this sexual divergence is abolished after the age of 45 years. Novelty:Maximal fat oxidation rate is higher in young women compared with men. This sex-related difference is attenuated after the age of 45 years. Cardiorespiratory fitness does not influence this sex-related difference.
... One of the key physiological variables that determines endurance performance is VO 2 max [29], showing that high-level endurance athletes can achieve a large VO 2 max [10]. Therefore, a common aim of endurance training programs is to improve VO 2 max. ...
Article
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A systematic review and meta-analysis were performed to determine if heart rate variability-guided training (HRV-g), compared to predefined training (PT), maximizes the further improvement of endurance physiological and performance markers in healthy individuals. This analysis included randomized controlled trials assessing the effects of HRV-g vs. PT on endurance physiological and performance markers in untrained, physically active, and well-trained subjects. Eight articles qualified for inclusion. HRV-g training significantly improved maximum oxygen uptake (VO 2 max) (MD = 2.84, CI: 1.41, 4.27; p < 0.0001), maximum aerobic power or speed (WMax) (SMD = 0.66, 95% CI 0.33, 0.98; p < 0.0001), aerobic performance (SMD = 0.71, CI 0.16, 1.25; p = 0.01) and power or speed at ventilatory thresholds (VT) VT1 (SMD = 0.62, CI 0.04, 1.20; p = 0.04) and VT2 (SMD = 0.81, CI 0.41, 1.22; p < 0.0001). However, HRV-g did not show significant differences in VO 2 max (MD = 0.96, CI −1.11, 3.03; p = 0.36), WMax (SMD = 0.06, CI −0.26, 0.38; p = 0.72), or aerobic performance (SMD = 0.14, CI −0.22, 0.51; p = 0.45) in power or speed at VT1 (SMD = 0.27, 95% CI −0.16, 0.70; p = 0.22) or VT2 (SMD = 0.18, 95% CI −0.20, 0.57; p = 0.35), when compared to PT. Although HRV-based training periodization improved both physiological variables and aerobic performance, this method did not provide significant benefit over PT.
... However, there has been an increased interest in low-carbohydrate, high-fat (LCHF) diets in recent years, as a mechanism to increase fat oxidation during exercise and utilize more of the body's fat stores [2]. A high capacity for fat oxidation may be particularly important for athletes competing in ultradistance events [3], and adaptation to a LCHF diet could benefit long-distance swimmers who perform prolonged sub-maximal exercise with limited opportunity to consume adequate carbohydrate [2,4]. ...
Article
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Background Swimming economy refers to the rate of energy expenditure relative to swimming speed of movement, is inversely related to the energetic cost of swimming, and is as a key factor influencing endurance swimming performance. The objective of this study was to determine if high-carbohydrate, low-fat (HCLF) and low-carbohydrate, high-fat (LCHF) diets affect energetic cost of submaximal swimming. Methods Eight recreational swimmers consumed two 3-day isoenergetic diets in a crossover design. Diets were tailored to individual food preferences, and macronutrient consumption was 69–16-16% and 16–67-18% carbohydrate-fat-protein for the HCLF and LCHF diets, respectively. Following each 3-day dietary intervention, participants swam in a flume at velocities associated with 50, 60, and 70% of their maximal aerobic capacity (VO 2max ). Expired breath was collected and analyzed while they swam which enabled calculation of the energetic cost of swimming. A paired t-test compared macronutrient distribution between HCLF and LCHF diets, while repeated-measures ANOVA determined effects of diet and exercise intensity on physiological endpoints. Results Respiratory exchange ratio was significantly higher in HCLF compared to LCHF ( p = 0.003), but there were no significant differences in the rate of oxygen consumption ( p = 0.499) or energetic cost of swimming ( p = 0.324) between diets. Heart rate did not differ between diets ( p = 0.712), but oxygen pulse, a non-invasive surrogate for stroke volume, was greater following the HCLF diet ( p = 0.029). Conclusions A 3-day high-carbohydrate diet increased carbohydrate utilization but did not affect swimming economy at 50–70% VO 2max . As these intensities are applicable to ultramarathon swims, future studies should use higher intensities that would be more relevant to shorter duration events.
... However, there has been an increased interest in low-carbohydrate, high-fat (LCHF) diets in recent years, as a mechanism to increase fat oxidation during exercise and utilize more of the body's fat stores (2). A high capacity for fat oxidation may be particularly important for athletes competing in ultra-distance events (3), and adaptation to a LCHF diet could bene t long-distance swimmers who perform prolonged sub-maximal exercise with limited opportunity to consume adequate carbohydrate (2,4). ...
Preprint
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Background: Swimming economy refers to the rate of energy expenditure relative to swimming speed of movement, is inversely related to the energetic cost of swimming, and is as a key factor influencing endurance swimming performance. The objective of this study was to determine if high-carbohydrate, low-fat (HCLF) and low-carbohydrate, high-fat (LCHF) diets affect energetic cost of submaximal swimming. Methods: Eight recreational swimmers consumed two 3-day isoenergetic diets in a crossover design. Diets were tailored to individual food preferences, and macronutrient consumption was 69-16-16% and 16-67-18% carbohydrate-fat-protein for the HCLF and LCHF diets, respectively. Following each 3-day dietary intervention, participants swam in a flume at velocities associated with 50, 60, and 70% of their maximal aerobic capacity (VO2max). Expired breath was collected and analyzed while they swam which enabled calculation of the energetic cost of swimming. A paired t-test compared macronutrient distribution between HCLF and LCHF diets, while repeated-measures ANOVA determined effects of diet and exercise intensity on physiological endpoints. Results: Respiratory exchange ratio was significantly higher in HCLF compared to LCHF (p = 0.003), but there were no significant differences in the rate of oxygen consumption (p = 0.499) or energetic cost of swimming (p = 0.324) between diets. Heart rate did not differ between diets (p = 0.712), but oxygen pulse, a non-invasive surrogate for stroke volume, was greater following the HCLF diet (p = 0.029). Conclusions: A 3-day high-carbohydrate diet increased carbohydrate utilization but did not affect swimming economy at 50-70% VO2max. As these intensities are applicable to ultramarathon swims, future studies should use higher intensities that would be more relevant to shorter duration events.
... For example, 6 weeks of fasted-state training increased the intensity at which maximal fat oxidation occurred more than training in a CHO-fed state (Van Proeyen et al., 2011), while another 6-week study found no differences in fat oxidation rates when tested in a fed state while also providing additional CHO (De Bock et al., 2008). Although high capacity for fat oxidation is important during extended-duration endurance events (Frandsen et al., 2017), it is unclear how much this can be increased through fasted-state training. This uncertainty is reflected in the large number of athletes who believe fasted-state training is not beneficial or are unsure of its merit. ...
Article
Athletes may choose to perform exercise in the overnight-fasted state for a variety of reasons related to convenience, gut comfort, or augmenting the training response, but it is unclear how many endurance athletes use this strategy. We investigated the prevalence and determinants of exercise performed in the overnight-fasted state among endurance athletes using an online survey and examined differences based on sex, competitive level, and habitual dietary pattern. The survey was completed by 1,950 endurance athletes (51.0% female, mean age 40.9 ± 11.1 years). The use of fasted training was reported by 62.9% of athletes, with significant effects of sex ( p < .001, Cramer’s V [φ c ] = 0.18, 90% CI [0.14, 0.22]), competitive level ( p < .001, φ c = 0.09, 90% CI [0.5, 0.13]), and habitual dietary pattern noted ( p < .001, φ c = 0.26, 90% CI [0.22, 0.29]). Males, nonprofessional athletes, and athletes following a low-carbohydrate, high-fat diet were most likely to perform fasted training. The most common reasons for doing so were related to utilizing fat as a fuel source (42.9%), gut comfort (35.5%), and time constraints/convenience (31.4%), whereas the most common reasons athletes avoided fasted training were that it does not help their training (47.0%), performance was worse during fasted training (34.7%), or greater hunger (34.6%). Overall, some athletes perform fasted training because they think it helps their training, whereas others avoid it because they think it is detrimental to their training goals, highlighting a need for future research. These findings offer insights into the beliefs and practices related to fasted-state endurance training.
... This leads to a greater fat oxidation capacity (Stisen et al., 2006;Sahlin et al., 2008) and delayed reliance on carbohydrates (Brooks and Mercier, 1994), resulting in a "glycogen-sparing effect" (Holloszy and Coyle, 1984) in endurance-trained athletes. The fat oxidation capacity may be a determining factor in endurance performance (Frandsen et al., 2017). ...
... This leads to a greater fat oxidation capacity (Stisen et al., 2006;Sahlin et al., 2008) and delayed reliance on carbohydrates (Brooks and Mercier, 1994), resulting in a "glycogen-sparing effect" (Holloszy and Coyle, 1984) in endurance-trained athletes. The fat oxidation capacity may be a determining factor in endurance performance (Frandsen et al., 2017). ...
Article
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Purpose: The present study aimed to determine whether whole-body fat oxidation and muscle deoxygenation kinetics parameters during exercise were related in individuals with different aerobic fitness levels. Methods: Eleven cyclists [peak oxygen uptake (VO 2peak): 64.9 ± 3.9 mL·kg −1 ·min −1 ] and 11 active individuals (VO 2peak : 49.1 ± 7.4 mL·kg −1 ·min −1) performed a maximal incremental cycling test to determineVO 2peak and a submaximal incremental cycling test to assess whole-body fat oxidation using indirect calorimetry and muscle deoxygenation kinetics of the vastus lateralis (VL) using near-infrared spectroscopy (NIRS). A sinusoidal (SIN) model was used to characterize fat oxidation kinetics and to determine the intensity (Fat max) eliciting maximal fat oxidation (MFO). The muscle deoxygenation response was fitted with a double linear model. The slope of the first parts of the kinetics (a 1) and the breakpoint ([HHb] BP) were determined. Results: MFO (p = 0.01) and absolute fat oxidation rates between 20 and 65% VO 2peak were higher in cyclists than in active participants (p < 0.05), while Fat max occurred at a higher absolute exercise intensity (p = 0.01). a 1 was lower in cyclists (p = 0.02) and [HHb] BP occurred at a higher absolute intensity (p < 0.001) than in active individuals.VO 2peak was strongly correlated with MFO, Fat max , and [HHb] BP (r = 0.65-0.88, p ≤ 0.001). MFO and Fat max were both correlated with [HHb] BP (r = 0.66, p = 0.01 and r = 0.68, p < 0.001, respectively) and tended to be negatively correlated with a 1 (r =-0.41, p = 0.06 for both). Conclusion: This study showed that whole-body fat oxidation and muscle deoxygenation kinetics were both related to aerobic fitness and that a relationship between the two kinetics exists. Individuals with greater aerobic fitness may have a delayed reliance on glycolytic metabolism at higher exercise intensities because of a longer maintained balance between O 2 delivery and consumption supporting higher fat oxidation rates.
... This leads to a greater fat oxidation capacity (Stisen et al., 2006;Sahlin et al., 2008) and delayed reliance on carbohydrates (Brooks and Mercier, 1994), resulting in a "glycogen-sparing effect" (Holloszy and Coyle, 1984) in endurance-trained athletes. The fat oxidation capacity may be a determining factor in endurance performance (Frandsen et al., 2017). ...
Article
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Purpose The present study aimed to determine whether whole-body fat oxidation and muscle deoxygenation kinetics parameters during exercise were related in individuals with different aerobic fitness levels. Methods Eleven cyclists [peak oxygen uptake (V.O2⁢p⁢e⁢a⁢k): 64.9 ± 3.9 mL⋅kg–1⋅min–1] and 11 active individuals (V.O2⁢p⁢e⁢a⁢k: 49.1 ± 7.4 mL⋅kg–1⋅min–1) performed a maximal incremental cycling test to determine V.O2⁢p⁢e⁢a⁢k and a submaximal incremental cycling test to assess whole-body fat oxidation using indirect calorimetry and muscle deoxygenation kinetics of the vastus lateralis (VL) using near-infrared spectroscopy (NIRS). A sinusoidal (SIN) model was used to characterize fat oxidation kinetics and to determine the intensity (Fatmax) eliciting maximal fat oxidation (MFO). The muscle deoxygenation response was fitted with a double linear model. The slope of the first parts of the kinetics (a1) and the breakpoint ([HHb]BP) were determined. Results MFO (p = 0.01) and absolute fat oxidation rates between 20 and 65% V.O2⁢p⁢e⁢a⁢k were higher in cyclists than in active participants (p < 0.05), while Fatmax occurred at a higher absolute exercise intensity (p = 0.01). a1 was lower in cyclists (p = 0.02) and [HHb]BP occurred at a higher absolute intensity (p < 0.001) than in active individuals. V.O2⁢p⁢e⁢a⁢k was strongly correlated with MFO, Fatmax, and [HHb]BP (r = 0.65–0.88, p ≤ 0.001). MFO and Fatmax were both correlated with [HHb]BP (r = 0.66, p = 0.01 and r = 0.68, p < 0.001, respectively) and tended to be negatively correlated with a1 (r = -0.41, p = 0.06 for both). Conclusion This study showed that whole-body fat oxidation and muscle deoxygenation kinetics were both related to aerobic fitness and that a relationship between the two kinetics exists. Individuals with greater aerobic fitness may have a delayed reliance on glycolytic metabolism at higher exercise intensities because of a longer maintained balance between O2 delivery and consumption supporting higher fat oxidation rates.
... FAT MAX ) (Amaro-Gahete et al. 2019;Maunder et al. 2018). However, knowledge on the reproducibility of these parameters is crucial to be able to appropriately interpret the importance of PFO and FAT MAX in the context of weight management (Dandanell et al. 2017a, b), metabolic health (Robinson et al. 2015) and/or endurance exercise performance (Frandsen et al. 2017). ...
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PurposePrior studies exploring the reliability of peak fat oxidation (PFO) and the intensity that elicits PFO (FATMAX) are often limited by small samples. This study characterised the reliability of PFO and FATMAX in a large cohort of healthy men and women.Methods Ninety-nine adults [49 women; age: 35 (11) years; V˙\dot{V}O2peak: 42.2 (10.3) mL·kg BM−1·min−1; mean (SD)] completed two identical exercise tests (7–28 days apart) to determine PFO (g·min−1) and FATMAX (%V˙\dot{V}O2peak) by indirect calorimetry. Systematic bias and the absolute and relative reliability of PFO and FATMAX were explored in the whole sample and sub-categories of: cardiorespiratory fitness, biological sex, objectively measured physical activity levels, fat mass index (derived by dual-energy X-ray absorptiometry) and menstrual cycle status.ResultsNo systematic bias in PFO or FATMAX was found between exercise tests in the entire sample (− 0.01 g·min−1 and 0%V˙\dot{V}O2peak, respectively; p > 0.05). Absolute reliability was poor [within-subject coefficient of variation: 21% and 26%; typical errors: ± 0.06 g·min−1 and × / ÷ 1.26%V˙\dot{V}O2peak; 95% limits of agreement: ± 0.17 g·min−1 and × / ÷ 1.90%V˙\dot{V}O2peak, respectively), despite high (r = 0.75) and moderate (r = 0.45) relative reliability for PFO and FATMAX, respectively. These findings were consistent across all sub-groups.Conclusion Repeated assessments are required to more accurately determine PFO and FATMAX.
... Increased fat oxidation and decreased submaximal HR (which would increase run speed at the same HR) have been shown respectively by Heatherly et al. (2018), who demonstrated increased fat oxidation rates through a LCD and improved 5 km performance in 6 of 8 participants, and Le Meur et al. (2013) who showed decreased submaximal HR and associated improved competitive performances. In addition, 50% of the variation in Ironman triathlon race time was shown to be explained by peak oxygen uptake and MFO in well trained triathletes competing in the Ironman World Championship (Frandsen et al., 2017). ...
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The earliest humans relied on large quantities of metabolic energy from the oxidation of fatty acids to develop larger brains and bodies, prevent and reduce disease risk, extend longevity, in addition to other benefits. This was enabled through the consumption of a high fat and low-carbohydrate diet (LCD). Increased fat oxidation also supported daily bouts of prolonged, low-intensity, aerobic-based physical activity. Over the past 40-plus years, a clinical program has been developed to help people manage their lifestyles to promote increased fat oxidation as a means to improve various aspects of health and fitness that include reducing excess body fat, preventing disease, and optimizing human performance. This program is referred to as maximum aerobic function, and includes the practical application of a personalized exercise heart rate (HR) formula of low-to-moderate intensity associated with maximal fat oxidation (MFO), and without the need for laboratory evaluations. The relationship between exercise training at this HR and associated laboratory measures of MFO, health outcomes and athletic performance must be verified scientifically.
... Our data may be relevant to those competing in ultraendurance events >4 h, in which maximal fat oxidation has been shown to be associated with performance. 32 However, the duration of our exercise protocol (60 min), and the intensity employed (65% V O 2 max) cannot be readily applied to the longer duration (>4 h), lower intensity work that characterizes ultra-endurance events. In addition, prolonged ultra-endurance performance cannot be sustained on water alone, and requires exogenous fuel ingestion (for example, ingestion of carbohydrate gels and beverages). ...
Article
Objectives: This study investigated the effect of 7 days' supplementation with New Zealand blackcurrant extract on thermoregulation and substrate metabolism during running in the heat. Design: Randomized, double-blind, cross-over study. Methods: Twelve men and six women (mean±SD: Age 27±6 years, height 1.76±0.10m, mass 74±12kg, V̇O2max 53.4±7.0mLkg-1min-1) completed one assessment of maximal aerobic capacity and one familiarisation trial (18°C, 40% relative humidity, RH), before ingesting 2×300mgday-1 capsules of CurraNZ™ (each containing 105mg anthocyanin) or a visually matched placebo (2×300mg microcrystalline cellulose M102) for 7 days (washout 14 days). On day 7 of each supplementation period, participants completed 60min of fasted running at 65% V̇O2max in hot ambient conditions (34°C and 40% relative humidity). Results: Carbohydrate oxidation was decreased in the NZBC trial [by 0.24gmin-1 (95% CI: 0.21-0.27gmin-1)] compared to placebo (p= 0.014, d=0.46), and fat oxidation was increased in the NZBC trial [by 0.12gmin-1 (95% CI: 0.10 to 0.15gmin-1)], compared to placebo (p=0.008, d=0.57). NZBC did not influence heart rate (p=0.963), rectal temperature (p=0.380), skin temperature (p=0.955), body temperature (p=0.214) or physiological strain index (p=0.705) during exercise. Conclusions: Seven-days intake of 600mg NZBC extract increased fat oxidation without influencing cardiorespiratory or thermoregulatory variables during prolonged moderate intensity running in hot conditions.
... In contrast when eating the LCHF diet, athletes retained the capacity to oxidize both fat and carbohydrate at high rates during exercise at that intensity whilst maintaining their performance capacity. Superior metabolic flexibility would likely be beneficial during ultradistance events as maximal fat oxidation rate measured during a graded exercise test is a significant predictor of performance time during the Ironman Triathlon (Frandsen et al., 2017). ...
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A common belief is that high intensity exercise (>60%VO2max) is best sustained by high rates of carbohydrate oxidation. The belief is based, in part, on an idea developed by Krogh and Lindhard in 1920. In the 100 years since, few studies have tested its validity. We tested the null hypothesis that performance in competitive recreational athletes exercising at >80% VO2max, during simulated 5-km running time trials (5KTT) would be impaired during a 6-week period of adaption to a low-carbohydrate, high-fat (LCHF) diet, compared to their performances when they ate a diet higher in carbohydrate and lower in fat (HCLF). Seven male athletes (age 35.6 ± 8.4 years, height 178.7 ± 4.1 cm, weight 68.6 ± 1.6 kg) completed two maximal exercise (VO2max) tests (Day 1 and 39) and four 5KTT (Day 4, 14, 28, and 42) in a fasted state during two 6-week periods when they ate either a HCLF or a LCHF diet, in a randomized counterbalanced, crossover design. Exercise performance during the VO2max tests was unchanged on either diet (p = 0.251). Performance in the initial 5KTT was significantly slower on the LCHF diet (p = 0.011). There were no diet-related performance differences in the remaining three 5KTT (p > 0.22). Subjects exercised at ~82%VO2max. Carbohydrate oxidation provided 94% of energy on the HCLF diet, but only 65% on the LCHF diet. 5KTT performance at ~82%VO2max was independent of the runners' habitual diet. The HCLF diet offered no advantage over a diet with a high-fat content. Since these athletes run faster than 88% of recreational distance runners in the United States (U.S.), this finding may have wide general application.
... Given that humans have a greater capacity for storage of fats than carbohydrates (in the form of glycogen), there is a progressively greater use of lipids as fuel over the duration of the event (up to 80% of the total caloric expenditure) (36,37). Indeed, rates of maximal fat oxidation have been shown to correlate with Ironman performance, with the fastest athletes (finishing time of 9 hours) displaying the highest rates (38). Therefore, increasing this ability through training or nutritional strategies would seem appropriate to maximise performance over long distance events. ...
Chapter
Triathlon is a sport consisting of swimming, cycling and running performed consecutively over different distances, with each discipline connected by a brief transition. The distances over which triathlon racing occurs range from mixed-team relays to sprint, Olympic, long distance, half-Ironman and Ironman events. Within these events the swim (300–4000 m), cycle (7–180 km) and run (1.6–42.2 km) segments differ considerably. As a result, specific physiological requirements dictate success in the various forms of triathlon. Moreover, certain rules and regulations, such as the ability to draft behind competitors, affect the style of racing and consequently the physiological demands. This chapter will address these physiological requirements and the responses associated with the different distances of triathlon, from sprint to Ironman.
Article
Purpose The purpose of this study is to evaluate the effect of three different preexercise meals: high-carbohydrate, low-glycemic index (LGI), high-carbohydrate, high-GI (HGI) and low-carbohydrate high fat (LCHO) on substrate oxidation during an incremental cycling test (ICT) in recreationally active adults. Design/methodology/approach This was a parallel, randomized study in which participants ingested one of three meals (LGI, HGI or LCHO) 3 h prior to exercise testing. Testing included ICT to exhaustion with continuous ergospirometry measurement. Findings Fat oxidation rate was significantly higher in LCHO compared to HGI ( p = 0.039). Carbohydrate contribution to energy production was significantly lower and fat contribution higher in LCHO compared to HGI ( p = 0.034). Fat-to-carbohydrates crossover point was achieved at significantly higher heart rate in LCHO group compared to LGI and HGI ( p = 0.046 and p = 0.049, respectively). Peak fat oxidation occurred significantly later during exercises in LCHO group compared to HGI ( p = 0.025). In conclusion, LCHO meal results in a higher fat oxidation, reduced carbohydrates contribution-to-energy production, delayed peak fat oxidation point and altered fat-to-carbohydrates crossover dynamics. There are no differences in substrate oxidation between high-carbohydrate preexercise meals that differ only in GI. Originality/value To the best of the authors’ knowledge, this is the first study to compare the acute effect of both the amount of carbohydrates and the GI in a preexercise meal on substrate utilization during ICT.
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In exercise science, the crossover effect denotes that fat oxidation is the primary fuel at rest and during low-intensity exercise with a shift towards an increased reliance on carbohydrate oxidation at moderate to high exercise intensities. This model makes four predictions: First, >50% of energy comes from carbohydrate oxidation at ≥60% of maximum oxygen consumption (VO2max), termed the crossover point. Second, each individual has a maximum fat oxidation capacity (FATMAX) at an exercise intensity lower than the crossover point. FATMAX values are typically 0.3–0.6 g/min. Third, fat oxidation is minimized during exercise ≥85%VO2max, making carbohydrates the predominant energetic substrate during high-intensity exercise, especially at >85%VO2max. Fourth, high-carbohydrate low-fat (HCLF) diets will produce superior exercise performances via maximizing pre-exercise storage of this predominant exercise substrate. In a series of recent publications evaluating the metabolic and performance effects of low-carbohydrate high-fat (LCHF/ketogenic) diet adaptations during exercise of different intensities, we provide findings that challenge this model and these four predictions. First, we show that adaptation to the LCHF diet shifts the crossover point to a higher %VO2max (>80%VO2max) than previously reported. Second, substantially higher FATMAX values (>1.5 g/min) can be measured in athletes adapted to the LCHF diet. Third, endurance athletes exercising at >85%VO2max, whilst performing 6 × 800 m running intervals, measured the highest rates of fat oxidation yet reported in humans. Peak fat oxidation rates measured at 86.4 ± 6.2%VO2max were 1.58 ± 0.33 g/min with 30% of subjects achieving >1.85 g/min. These studies challenge the prevailing doctrine that carbohydrates are the predominant oxidized fuel during high-intensity exercise. We recently found that 30% of middle-aged competitive athletes presented with pre-diabetic glycemic values while on an HCLF diet, which was reversed on LCHF. We speculate that these rapid changes between diet, insulin, glucose homeostasis, and fat oxidation might be linked by diet-induced changes in mitochondrial function and insulin action. Together, we demonstrate evidence that challenges the current crossover concept and demonstrate evidence that a LCHF diet may also reverse features of pre-diabetes and future metabolic disease risk, demonstrating the impact of dietary choice has extended beyond physical performance even in athletic populations.
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In general, the concept of a mechanism in biology has three distinct meanings. It may refer to a philosophical thesis about the nature of life and biology, to the internal workings of a machine-like structure, or to the causal explanation of a particular phenomenon [1]. Understanding the biological mechanisms that justify acute and chronic physiological responses to exercise interventions determines the development of training principles and training methods. A strong understanding of the effects of exercise in humans may help researchers to identify what causes specific biological changes and to properly identify the most adequate processes for implementing a training stimulus [1]. Despite the significant body of knowledge regarding the physiological and physical effects of different training methods (based on load dimensions), some biological causes of those changes are still unknown. Additionally, few studies have focused on natural biological variability in humans and how specific human properties may underlie different responses to the same training intervention. Thus, more original research is needed to provide plausible biological mechanisms that may explain the physiological and physical effects of exercise and training in humans. In this Special Issue, we discuss/demonstrate the biological mechanisms that underlie the beneficial effects of physical fitness and sports performance, as well as their importance and their role in/influences on physical health. A total of 28 manuscripts are published here, of which 25 are original articles, two are reviews, and one is a systematic review. Two papers are on neuromuscular training programs (NMTs), training monotony (TM), and training strain (TS) in soccer players [2,3]; five articles provide innovative findings about testosterone and cortisol [4,5], gastrointestinal hormones [6], spirulina [7], and concentrations of erythroferrone (ERFE) [8]; another five papers analyze fitness and its association with other variables [7,9–12]; three papers examine body composition in elite female soccer players [2], adolescents [6], and obese women [7]; five articles examines the effects of high-intensity interval training (HIIT) [7,10,13–15]; one paper examines the acute effects of different levels of hypoxia on maximal strength, muscular endurance, and cognitive function [16]; another article evaluates the efficiency of using vibrating exercise equipment (VEE) compared with using sham-VEE in women with CLBP (chronic lowback pain) [17]; one article compares the effects of different exercise modes on autonomic modulation in patients with T2D (type 2 diabetes mellitus) [14]; and another paper analyzes the changes in ABB (acid–base balance) in the capillaries of kickboxers [18]. Other studies evaluate: the effects of resistance training on oxidative stress and muscle damage in spinal cord-injured rats [19]; the effects of muscle training on core muscle performance in rhythmic gymnasts [20]; the physiological profiles of road cyclist in different age categories [21]; changes in body composition during the COVID-19 [22]; a mathematical model capable of predicting 2000 m rowing performance using a maximum-effort 100 m indoor rowing ergometer [23]; the effects of ibuprofen on performance and oxidative stress [24]; the associations of vitamin D levels with various motor performance tests [12]; the level of knowledge on FM (Fibromyalgia) [25]; and the ability of a specific BIVA (bioelectrical impedance vector analysis) to identify changes in fat mass after a 16-week lifestyle program in former athletes [26]. Finally, one review evaluates evidence from published systematic reviews and meta-analyses about the efficacy of exercise on depressive symptoms in cancer patients [27]; another review presents the current state of knowledge on satellite cell dependent skeletal muscle regeneration [28]; and a systematic review evaluates the effects of exercise on depressive symptoms among women during the postpartum period [29]
Article
Maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) seems to show a diurnal variation in men, which favours an increased performance in the afternoon than the morning. At present, it remains unknown whether the observed MFO and Fatmax diurnal variation in men is also present in women. Therefore, the current study examined the diurnal variations of MFO and Fatmax in women. Nineteen healthy women (age: 26.9 ± 8.7 years, maximum oxygen uptake: 39.8 ± 6.5 ml/kg/min) participated in the study. MFO and Fatmax were determined by a graded exercise test in cycloergometer using a cross-over design performed on two separate daytime schedules, one conducted in the morning (8am–11am) and one in the afternoon (5pm–8pm). Stoichiometric equations were used to calculate fat oxidation rates. There were no significant differences between MFO-morning and MFO-afternoon (0.24 ± 0.10 vs. 0.23 ± 0.07 g/min, respectively; P = 0.681). Similarly, there was no significant differences between Fatmax-morning and Fatmax-afternoon (41.1 ± 4.7 vs. 42.6 ± 5.5% of maximal oxygen uptake, respectively; P = 0.305). These results persisted after controlling for fat mass percentage (all P > 0.5). In summary, the main finding of the present study was that MFO and Fatmax were similar independent of the time-of-day when the exercise test is performed in healthy women. These results have important clinical implications since they suggest that, in contrast to what was found in men, MFO and Fatmax show similar rates during the course of the day in women. Highlights • MFO and Fatmax were similar during the afternoon and morning in young healthy women. • Our results suggest that, in women, it does not matter when endurance exercise is performed in term of fat metabolism during exercise.
Thesis
Die Arbeit beleuchtet den Einsatz algorithmischer Datenbearbeitungen bei sportwissenschaftlichen Spiroergometrien aus praktischen und theoretischen Gesichtspunkten. Die aktuelle Verbreitung von algorithmischen Datenbearbeitungen aus Breath-by-Breath Untersuchungen wird über die Ergebnisse eines Fragebogens und einer systematischen Literaturübersicht dargestellt. Zudem erfolgt die Analyse der durch Algorithmen verursachten Messwertvarianzen der Sauerstoffaufnahme in diskontinuierlichen Belastungsuntersuchungen, bei Jugendlichen und im submaximalen Belastungsbereich.
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Introduction: The aim of this study was to describe maximal fat oxidation (MFO) rates in an athletic population. Method: In total, 1121 athletes (933 males and 188 females), from a variety of sports and competitive level, undertook a graded exercise test on a treadmill in a fasted state (≥5 h fasted). Rates of fat oxidation were determined using indirect calorimetry. Results: The average MFO was 0.59 ± 0.18 g·min, ranging from 0.17 to 1.27 g·min. Maximal rates occurred at an average exercise intensity of 49.3% ± 14.8% V˙O2max, ranging from 22.6% to 88.8% V˙O2max. In absolute terms, male athletes had significantly higher MFO compared with females (0.61 and 0.50 g·min, respectively, P < 0.001). Expressed relative to fat-free mass (FFM), MFO were higher in the females compared with males (MFO/FFM: 11.0 and 10.0 mg·kg·FFM·min, respectively, P < 0.001). Soccer players had the highest MFO/FFM (10.8 mg·kg·FFM·min), ranging from 4.1 to 20.5 mg·kg·FFM·min, whereas American Football players displayed the lowest rates of MFO/FFM (9.2 mg·kg·FFM·min). In all athletes, and when separated by sport, large individual variations in MFO rates were observed. Significant positive correlations were found between MFO (g·min) and the following variables: FFM, V˙O2max, FATMAX (the exercise intensity at which the MFO was observed), percent body fat, and duration of fasting. When taken together these variables account for 47% of the variation in MFO. Conclusion: MFO and FATMAX vary significantly between athletes participating in different sports but also in the same sport. Although variance in MFO can be explained to some extent by body composition and fitness status, more than 50% of the variance is not explained by these variables and remains unaccounted for.
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The purpose of this study was to compare whole-body fat oxidation kinetics after prior exercise with overnight fasting in elite endurance athletes. Thirteen highly trained athletes (9 men and 4 women; maximal oxygen uptake: 66 ± 1 mL·min⁻¹·kg⁻¹) performed 3 identical submaximal incremental tests on a cycle ergometer using a cross-over design. A control test (CON) was performed 3 h after a standardized breakfast, a fasting test (FAST) 12 h after a standardized evening meal, and a postexercise test (EXER) after standardized breakfast, endurance exercise, and 2 h fasting recovery. The test consisted of 3 min each at 30%, 40%, 50%, 60%, 70%, and 80% of maximal oxygen uptake and fat oxidation rates were measured through indirect calorimetry. During CON, maximal fat oxidation rate was 0.51 ± 0.04 g·min⁻¹ compared with 0.69 ± 0.04 g·min⁻¹ in FAST (P < 0.01), and 0.89 ± 0.05 g·min⁻¹ in EXER (P < 0.01). Across all intensities, EXER was significantly higher than FAST and FAST was higher than CON (P < 0.01). Blood insulin levels were lower and free fatty acid and cortisol levels were higher at the start of EXER compared with CON and FAST (P < 0.05). Plasma nuclear magnetic resonance-metabolomics showed similar changes in both EXER and FAST, including increased levels of fatty acids and succinate. In conclusion, prior exercise significantly increases whole-body fat oxidation during submaximal exercise compared with overnight fasting. Already high rates of maximal fat oxidation in elite endurance athletes were increased by approximately 75% after prior exercise and fasting recovery.
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Background: Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations. Methods: Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months). Results: Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise). Conclusion: Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.
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This narrative review summarizes recent intentions to find potential predictor variables for ultra-triathlon race performance (ie, triathlon races longer than the Ironman distance covering 3.8 km swimming, 180 km cycling, and 42.195 km running). Results from studies on ultra-triathletes were compared to results on studies on Ironman triathletes. A literature search was performed in PubMed using the terms "ultra", "triathlon", and "performance" for the aspects of "ultra-triathlon", and "Ironman", "triathlon", and "performance" for the aspects of "Ironman triathlon". All resulting papers were searched for related citations. Results for ultra-triathlons were compared to results for Ironman-distance triathlons to find potential differences. Athletes competing in Ironman and ultra-triathlon differed in anthropometric and training characteristics, where both Ironmen and ultra-triathletes profited from low body fat, but ultra-triathletes relied more on training volume, whereas speed during training was related to Ironman race time. The most important predictive variables for a fast race time in an ultra-triathlon from Double Iron (ie, 7.6 km swimming, 360 km cycling, and 84.4 km running) and longer were male sex, low body fat, age of 35-40 years, extensive previous experience, a fast time in cycling and running but not in swimming, and origins in Central Europe. Any athlete intending to compete in an ultra-triathlon should be aware that low body fat and high training volumes are highly predictive for overall race time. Little is known about the physiological characteristics of these athletes and about female ultra-triathletes. Future studies need to investigate anthropometric and training characteristics of female ultra-triathletes and what motivates women to compete in these races. Future studies need to correlate physiological characteristics such as maximum oxygen uptake (VO2max) with ultra-triathlon race performance in order to investigate whether these characteristics are also predictive for ultra-triathlon race performance.
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The aim of the present study was to assess whether physical characteristics, training, or prerace experience were related to performance in recreational male Ironman triathletes using bi- and multivariate analysis. 83 male recreational triathletes who volunteered to participate in the study (M age 41.5 yr., SD = 8.9) had a mean body height of 1.80 m (SD = 0.06), mean body mass of 77.3 kg (SD = 8.9), and mean Body Mass Index of 23.7 kg/m2 (SD = 2.1) at the 2009 IRONMAN SWITZERLAND competition. Speed in running during training, personal best marathon time, and personal best time in an Olympic distance triathlon were related to the Ironman race time. These three variables explained 64% of the variance in Ironman race time. Personal best marathon time was significantly and positively related to the run split time in the Ironman race. Faster running while training and both a fast personal best time in a marathon and in an Olympic distance triathlon were associated with a fast Ironman race time.
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To elucidate if fat oxidation at rest predicts peak fat oxidation during exercise and/or metabolic phenotype in moderately overweight, sedentary men. Cross-sectional study.Subjects:We measured respiratory exchange ratio (RER) at rest in 44 moderately overweight, normotensive and normoglycemic men and selected 8 subjects with a low RER (L-RER, body mass index (BMI): 27.9+/-0.9 kg m(-2), RER: 0.76+/-0.02) and 8 with a high RER (H-RER; BMI 28.1+/-1.1 kg m(-2), RER: 0.89+/-0.02). After an overnight fast, a venous blood sample was obtained and a graded exercise test was performed. Fat oxidation during exercise was quantified using indirect calorimetry. Peak fat oxidation during exercise was higher in L-RER than in H-RER (0.333+/-0.096 vs 0.169+/-0.028 g min(-1); P<0.01) and occurred at a higher relative intensity (36.2+/-6.6 vs 28.2+/-3.1% VO(2max), P<0.05). Using the International Diabetes Federation criteria, we found that there was a lower accumulation of metabolic risk factors in L-RER than in H-RER (1.6 vs 3.5, P=0.028), and no subjects in L-RER and four of eight subjects in H-RER had the metabolic syndrome. Resting RER was positively correlated with plasma triglycerides (P<0.01) and negatively with plasma free fatty acids (P<0.05), and peak fat oxidation during exercise was positively correlated with plasma free fatty acid concentration at rest (P<0.05). A low RER at rest predicts a high peak fat oxidation during exercise and a healthy metabolic phenotype in moderately overweight, sedentary men.
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Seven men were studied during 30 min of treadmill exercise (approximately 70% VO2 max) to determine the effects of increased availability of plasma free fatty acids (FFA) and elevated plasma insulin on the utilization of muscle glycogen. This elevation of plasma FFA (1.01 mmol/1) with heparin (2,000 units) decreased the rate of muscle glycogen depletion by 40% as compared to the control experiment (FFA = 0.21 mmol/1). The ingestion of 75 g of glucose 45 min before exercise produced a 3.3-fold increase in plasma insulin and a 38% rise in plasma glucose at 0 min of exercise. Subsequent exercise increased muscle glycogen utilization and total carbohydrate (CHO) oxidation 17 and 13%, respectively, when compared to the control trial. This elevation of plasma insulin produced hypoglycemia (less than 3.5 mmol/1) in most subjects throughout the exercise. These data illustrate the regulatory influence of both plasma insulin and FFA on the rate of CHO usage during prolonged severe muscular activity.
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Eleven male triathletes were studied to determine the relationships between selected metabolic measurements and triathlon performance. Measurements of oxygen uptake (VO2), pulmonary ventilation (VE), and heart rate (HR) were made during submaximal and maximal 365.8 m freestyle swimming (FS), cycle ergometry (CE), and treadmill running (TR). Submaximal workloads were 1 m/s for swimming, 200 W for cycling, and 201.2 m/min for running. The mean VO2 max (l/min) was significantly (p less than .05) lower during FS (4.17) than CE (4.68) or TR (4.81). Swimming, cycling, and running performance times during the Muncie Endurathon (1.2 mile swim, 56 mile cycle, 13.1 mile run) were not significantly related to the event-specific VO2 max (ml/kg/min): -.49, -32 and -.55, respectively. The VO2 max expressed in l/min was found to be significantly (p less than .05) related to cycling time (r = -.70). A significant (p less than .05) relationship was observed between submaximal VO2 (ml/kg/min) during TM and run performance time (r = .64), whereas swimming and cycling performance times were significantly (p less than .05) related to submaximal VO2 max (l/min), r = .72 and .60, respectively. The percentage of VO2 (%VO2 max) used during the submaximal tests was significantly (p less than .05) related to swimming (.91), cycling (.78), and running (.86) performance times. Time spent running and cycling during triathlon competition was significantly (p less than .05) related to overall triathlon time, r = .97 and .81, respectively. However, swimming time was not significantly related (.30) to overall triathlon time. This study suggests that economy of effort is an important determinant of triathlon performance.
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We examined the variability and determinants of the respiratory exchange ratio (RER) at rest and during exercise in 61 trained cyclists. Fasting (10-12 h) RER was measured at rest and during exercise at 25, 50, and 70% of peak power output (W(peak)), during which blood samples were drawn for [lactate] and [free fatty acid] ([FFA]). Before these measurements, training volume, dietary intake and muscle fiber composition, [substrate], and enzyme activities were determined. There was large interindividual variability in resting RER (0.718-0.927) that persisted during exercise of increasing intensity. The major determinants of resting RER included muscle glycogen content, training volume, proportion of type 1 fibers, [FFA] and [lactate], and %dietary fat intake (adjusted r(2) = 0.59, P < 0.001). Except for muscle fiber composition, these variables also predicted RER at 25, 50, and 70% W(peak) to different extents. The key determinant at 25% W(peak) was blood-borne [substrate], at 50% was muscle [substrate] and glycolytic enzyme activities, and at 70% was [lactate]. Resting RER was also a significant determinant of RER at 25 (r = 0.60) and 50% (r = 0.44) W(peak).
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We studied male and female nonprofessional Ironman triathletes to determine whether percent body fat, training, and/or previous race experience were associated with race performance. We used simple linear regression analysis, with total race time as the dependent variable, to investigate the relationship among athletes' percent body fat, average amount of weekly training, and best time in an Ironman triathlon. For male athletes, percent body fat (r2 = 0.57, p < .001) was related to total race time but not average weekly training. For women, percent body fat showed no association with total race time; howeven average weekly training volume was related to total race time (r = .43, p < .01). Percent body fat and average weekly training were not correlated in either gender Speed in training was not associated with race performance in either gender. For men (r2 = .56, p < .001) and women (r2 = .45, p < .05), personal best time in an Ironman triathlon was related to total race time. We concluded that percent body fat was related to race performance in male athletes and to average weekly training in female athletes. Personal best time in an Ironman triathlon was associated with total race time for both male and female athletes.
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To examine the improvement in swimming (3.8 km), cycling (180 km), running (42.2 km), and overall performances at the Hawaii Ironman Triathlon of elite males and females between 1981 and 2007. Trends across years, gender differences in performance times in the three disciplines, and overall winning times of the top 10 males and females were analyzed. Overall performance time in the ironman decreased rapidly from 1981 but has remained stable since the late 1980s. From 1988 to 2007, linear regression analysis showed that change in swimming, cycling, running, and total performance for both males and females was less than 1.4% per decade, except for females' running time, which decreased by 3.8% per decade. Since 1988, the mean (SD) gender differences in time for swimming, cycling, running, and total event were 9.8% (2.9), 12.7% (2.0), 13.3% (3.1), and 12.6% (1.3), respectively. After an initial phase of rapid improvement of performances during the 1980s, there was a relative plateau, but at least in running and cycling, there were small improvements. Over the last two decades, gender difference in swimming remained stable while it slightly increased in cycling and decreased in running. The gender difference in ironman total performance is unlikely to change in the future.
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