Dose-Response Effects of p
-Synephrine on Fat Oxidation Rate During Exercise of Increasing Intensity

The present study aimed to investigate the potential effect of different aerobic fitness levels on substrate oxidation in trained taekwondo athletes. 57 male athletes (age 21.10±7.79 years; VO2max 50.67±6.67 ml/kg/min) with regular weekly taekwondo training and training experience of at least three years completed a graded exercise test to exhaustion on a treadmill. Maximal fat oxidation (MFO), the exercise intensity related to MFO (Fatmax), and carbohydrate (CHO) oxidation rate were measured using indirect calorimetry methods. The athletes then were divided into a low (<50 ml/kg/min, n=18) and high (>50 ml/kg/min, n=39) VO2max group. The average MFO was higher in the high VO2max group than in the low VO2max group (0.46±0.19 vs 0.28±0.11 g/min; P<0.001). Although Fatmax tended toward higher values in the high VO2max group, no difference was observed between the groups (49.15±15.22 vs 42.42±12.37% of VO2max; P=0.18). It was also shown that the high VO2max group had a lower CHO oxidation rate and a higher fat oxidation rate at given exercise intensities. In conclusion, it seems that MFO and substrate oxidation rates in taekwondo athletes can be influenced by aerobic fitness level such that the athletes with higher VO2max appeared to use more fat as a fuel source for energy supply during a given exercise.

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Body Fat has No Effect on the Maximal Fat Oxidation Rate in Young, Normal, and Overweight Women

The Journal of Strength and Conditioning Research ◽

10.1519/jsc.0000000000000512 ◽

2014 ◽

Vol 28 (8) ◽

pp. 2121-2126 ◽

Cited By ~ 5

Author(s):

Ashley N. Blaize ◽

Jeffrey A. Potteiger ◽

Randal P. Claytor ◽

Douglas A. Noe

Keyword(s):

Body Fat ◽

Oxidation Rate ◽

Fat Oxidation ◽

Overweight Women ◽

Maximal Fat Oxidation

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Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis

Nutrients ◽

10.3390/nu12123603 ◽

2020 ◽

Vol 12 (12) ◽

pp. 3603

Author(s):

Daniel Collado-Mateo ◽

Ana Myriam Lavín-Pérez ◽

Eugenio Merellano-Navarro ◽

Juan Del Coso

Keyword(s):

Systematic Review ◽

Oxidation Rate ◽

Meta Analysis ◽

Fat Oxidation ◽

Caffeine Intake ◽

Fasting Period ◽

Fitness Level ◽

Recreational Athletes ◽

Other Substances ◽

Dose Response Effect

A number of previous investigations have been designed to determine the effect of acute caffeine intake on the rate of fat oxidation during exercise. However, these investigations have shown contradictory results due to the differences in the exercise protocols used or the co-ingestion of caffeine with other substances. Hence, to date, there is no consensus about the effect of caffeine on fat oxidation during exercise. The purpose of this study was to conduct a systematic review followed by a meta-analysis to establish the effect of acute intake of caffeine (ranging from 2 to 7 mg/kg of body mass) on the rate of fat oxidation during exercise. A total of 19 studies published between 1978 and 2020 were included, all of which employed crossover experimental designs in which the ingestion of caffeine was compared to a placebo. Studies were selected if the exercise intensity was consistent in the caffeine and placebo trials and if these were preceded by a fasting protocol. A subsequent meta-analysis was performed using the random effects model to calculate the standardized mean difference (SMD). The meta-analysis revealed that caffeine significantly (p = 0.008) increased the fat oxidation rate (SMD = 0.73; 95% CI = 0.19 to 1.27). This increment was consistent with a significant (p = 0.04) reduction of the respiratory exchange ratio (SMD = −0.33; 95% CI = −0.65 to −0.01) and a significant (p = 0.049) increase in the oxygen uptake (SMD = 0.23; 95% CI = 0.01 to 0.44). The results also showed that there was a dose–response effect of caffeine on the fat oxidation rate, indicating that more than 3.0 mg/kg is necessary to obtain a statistically significant effect of this stimulant on fat oxidation during exercise. Additionally, the ability of caffeine to enhance fat oxidation during exercise was higher in sedentary or untrained individuals than in trained and recreational athletes. In conclusion, pre-exercise intake of a moderate dose of caffeine may effectively increase fat utilization during aerobic exercise of submaximal intensity performed after a fasting period. However, the fitness level of the participant may modulate the magnitude of the effect of caffeine on fat oxidation during exercise.

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Oxygen uptake and ratings of perceived exertion at the lactate threshold and maximal fat oxidation rate in untrained adults

European Journal of Applied Physiology ◽

10.1007/s00421-010-1821-z ◽

2011 ◽

Vol 111 (9) ◽

pp. 2063-2068 ◽

Cited By ~ 14

Author(s):

Corey A. Rynders ◽

Siddhartha S. Angadi ◽

Nathan Y. Weltman ◽

Glenn A. Gaesser ◽

Arthur Weltman

Keyword(s):

Oxygen Uptake ◽

Oxidation Rate ◽

Lactate Threshold ◽

Perceived Exertion ◽

Fat Oxidation ◽

Ratings Of Perceived Exertion ◽

Maximal Fat Oxidation

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Oxidation rate of exogenous carbohydrate during exercise is higher in boys than in men

Journal of Applied Physiology ◽

10.1152/japplphysiol.00140.2002 ◽

2003 ◽

Vol 94 (1) ◽

pp. 278-284 ◽

Cited By ~ 65

Author(s):

Brian W. Timmons ◽

Oded Bar-Or ◽

Michael C. Riddell

Keyword(s):

Total Energy ◽

Oxidation Rate ◽

Relative Proportion ◽

Fat Oxidation ◽

Substrate Utilization ◽

Pubertal Status ◽

Pubertal Boys ◽

Total Fat ◽

Relative Utilization

To determine whether the relative utilization of exogenous carbohydrate (CHOexo) differs between children and adults, substrate utilization during 60 min of cycling at 70% peak O2 uptake was studied in 12 pre- and early pubertal boys (9.8 ± 0.1 yr) and 10 men (22.1 ± 0.5 yr) on two occasions. Subjects consumed either a placebo or a13C-enriched 6% CHOexo beverage (total volume per trial: 24 ml/kg). Substrate utilization was calculated for the final 30 min of exercise. During both trials, total fat oxidation was higher (5.4 ± 0.5 vs. 3.0 ± 0.4 mg · kg−1 · min−1, P < 0.001) and total CHO oxidation lower (27.4 ± 1.5 vs. 34.8 ± 1.2 mg · kg−1 · min−1, P < 0.001) in boys than in men, respectively. During the CHOexo trial, CHOexo oxidation was higher ( P < 0.001) in boys (8.8 ± 0.5 mg · kg−1 · min−1) than in men (6.2 ± 0.5 mg · kg−1 · min−1) and provided a greater ( P < 0.001) relative proportion of total energy in boys (21.8 ± 1.4%) than in men (14.6 ± 0.9%). These results suggest that, although endogenous CHO utilization during exercise is lower, the relative oxidation of ingested CHO is considerably higher in boys than in men. The greater reliance on CHOexo in boys may be important in preserving endogenous fuels and may be related to pubertal status.

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Plasma free fatty acid concentration is closely tied to whole body peak fat oxidation rate during repeated exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00995.2018 ◽

2019 ◽

Vol 126 (6) ◽

pp. 1563-1571 ◽

Cited By ~ 5

Author(s):

Jacob Frandsen ◽

Stine Dahl Vest ◽

Christian Ritz ◽

Steen Larsen ◽

Flemming Dela ◽

...

Keyword(s):

Fatty Acid ◽

Free Fatty Acid ◽

Body Fat ◽

Oxidation Rate ◽

Plasma Free Fatty Acid ◽

Fat Oxidation ◽

Whole Body ◽

Exercise Tests ◽

Repeated Exercise ◽

Plasma Ffa

Plasma free fatty acids (FFA) are a major contributor to whole body fat oxidation during exercise. However, the extent to which manipulating plasma FFA concentrations will influence whole body peak fat oxidation rate (PFO) during exercise remains elusive. In this study we aimed to increase plasma FFA concentrations through a combination of fasting and repeated exercise bouts. We hypothesized that an increase in plasma FFA concentration would increase PFO in a dose-dependent manner. Ten healthy young (31 ± 6 yr) (mean ± SD) well-trained (maximal oxygen uptake 65.9 ± 6.1 ml·min−1·kg−1) men performed four graded exercise tests (GXTs) on 1 day. The GXTs were interspersed by 4 h of bed rest. This was conducted either in a fasted state or with the consumption of a standardized carbohydrate-rich meal 3.5 h before each GXT. Fasting and previous GXTs resulted in a gradual increase in PFO from 0.63 ± 0.18 g/min after an overnight fast (10 h) to 0.93 ± 0.17 g/min after ∼22 h of fasting and three previous GXTs. This increase in PFO coincided with an increase in plasma FFA concentrations ( r2 = 0.73, P < 0.0001). Ingestion of a carbohydrate-rich meal 3.5 h before each GXT resulted in unaltered PFO. This was also reflected in unchanged plasma FFA, glucose, and insulin concentrations. In this study we show that plasma FFA availability is closely tied to whole body PFO and that the length of fasting combined with previous exercise are robust stimuli toward increasing plasma FFA concentration, highlighting the importance for preexercise standardization when conducting GXTs measuring substrate oxidation. NEW & NOTEWORTHY We show that peak fat oxidation is increased in close relationship with plasma free fatty acid availability after combined fasting and repeated incremental exercise tests in healthy highly trained men. Therefore it may be argued that whole body fat oxidation rate measured in most cases after an overnight fast indeed does not represent whole body maximal fat oxidation rate but a whole body peak fat oxidation rate within the context of the preexercise standardization obtained in the study design.

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