Reliability of the Metabolic Response During Steady-State Exercise at FATmax in Young Men with Obesity.

Purpose: In this study we evaluated the reliability of blood lactate levels (BLa), energy expenditure and substrate utilization during prolonged exercise at the intensity that elicits maximal fat oxidation (FATmax). Furthermore, we investigated the accuracy of a single graded exercise test (GXT) for predicting energy metabolism at FATmax. Methods: Seventeen young men with obesity (26 ± 6 years; 36.4 ± 7.2 %body fat) performed a GXT on a treadmill in a fasted state (10-12 h) for the assessment of FATmax and cardiorespiratory fitness. Afterward, each subject performed two additional prolonged FATmax trials (102 ± 11 beats·min-1; 60-min) separated by 7 days. Indirect calorimetry was used for the assessment of energy expenditure and substrate utilization kinetics whereas capillary blood samples were taken for the measurement of BLa. Results: The BLa (limits of agreement (LoA): -1.2 to 0.8 mmol∙L-1; p = 1.0), fat utilization (LoA: -8.0 to 13.4 g∙h-1; p = 0.06), and carbohydrate utilization (LoA: -27.6 to 22.4 g∙h-1; p = 0.41) showed a good agreement whereas a modest systematic bias was found for energy expenditure (LoA: -16811 to 33355 kJ∙h-1; p < 0.05). All the aforementioned parameters showed a moderate to good reliability (Intraclass correlation coefficient: 0.67-0.92). The GXT overestimated fat (~46%) and carbohydrate (~26%) utilization as well as energy expenditure (36%) during steady-state exercise at FATmax. Conversely the GXT underestimated BLa (~28%). Conclusion: a single GXT cannot be used for an accurate prediction of energy metabolism during prolonged exercise in men with obesity. Thus, an additional steady-state FATmax trial (40-60 min) should be performed for a tailored and precise exercise prescription.

Analysis of the associations between salivary cortisol-, alpha-amylase-, and testosterone-responsiveness with the physical contact nature of team handball: a preliminary analysis.

BACKGROUND: This study evaluated endocrine responsiveness (ER) to physical stress (contact vs. non-contact nature of play) during team handball matches, according to the playing positions, thereby contextualizing the contact nature of the handball match. METHODS: The participants were ten male team handball players (24.1±3.17 years, 188.2±6.42 cm, 94.6±9.6 kg) divided into two groups: contact playing positions (CPP) and non-contact playing positions (NCPP). To evaluate the ER, the salivary cortisol (C), testosterone (T), and alpha-amylase (AA) concentrations were assessed before the game, during the halftime break, and after the match. Moreover, playing time (PT) and the number of contacts (NC) were counted post-match by video analysis. To determine possible differences between PT and the NC in the first and second halves of the match, a paired-sample t-test was used. The differences among ER-measures were calculated by the magnitude-based Cohen's effect size. Possible associations between NC and ER were analyzed by comparing CPP and NCPP in C, T, and AA. RESULTS: The CPP group performed significantly more physical contacts, while there was no difference in playing time between the groups. A stronger C response was evidenced in players with a longer playing time. During the game, the C response was directly determined by physical contact, with CPP players showing a stronger C response than NCPP players. CONCLUSIONS: This study provided evidence of the importance of contact actions during matches and training sessions, as a parameter of calculating training loads and preparing strategies for recovery and injury prevention. Further studies examining larger samples are warranted.

DE-PASS Best Evidence Statement (BESt): modifiable determinants of physical activity and sedentary behaviour in children and adolescents aged 5-19 years-a protocol for systematic review and meta-analysis.

INTRODUCTION: Physical activity among children and adolescents remains insufficient, despite the substantial efforts made by researchers and policymakers. Identifying and furthering our understanding of potential modifiable determinants of physical activity behaviour (PAB) and sedentary behaviour (SB) is crucial for the development of interventions that promote a shift from SB to PAB. The current protocol details the process through which a series of systematic literature reviews and meta-analyses (MAs) will be conducted to produce a best-evidence statement (BESt) and inform policymakers. The overall aim is to identify modifiable determinants that are associated with changes in PAB and SB in children and adolescents (aged 5-19 years) and to quantify their effect on, or association with, PAB/SB. METHODS AND ANALYSIS: A search will be performed in MEDLINE, SportDiscus, Web of Science, PsychINFO and Cochrane Central Register of Controlled Trials. Randomised controlled trials (RCTs) and controlled trials (CTs) that investigate the effect of interventions on PAB/SB and longitudinal studies that investigate the associations between modifiable determinants and PAB/SB at multiple time points will be sought. Risk of bias assessments will be performed using adapted versions of Cochrane's RoB V.2.0 and ROBINS-I tools for RCTs and CTs, respectively, and an adapted version of the National Institute of Health's tool for longitudinal studies. Data will be synthesised narratively and, where possible, MAs will be performed using frequentist and Bayesian statistics. Modifiable determinants will be discussed considering the settings in which they were investigated and the PAB/SB measurement methods used. ETHICS AND DISSEMINATION: No ethical approval is needed as no primary data will be collected. The findings will be disseminated in peer-reviewed publications and academic conferences where possible. The BESt will also be shared with policy makers within the DE-PASS consortium in the first instance. SYSTEMATIC REVIEW REGISTRATION: CRD42021282874.

A Systematic Review and Meta-Analysis on the Association and Differences between Aerobic Threshold and Point of Optimal Fat Oxidation.

Over the past two decades, scientists have attempted to evaluate whether the point of maximal fat oxidation (FATmax) and the aerobic threshold (AerT) are connected. The existence of such a relationship would allow a more tailored training approach for athletes while improving the efficacy of individualized exercise prescriptions when treating numerous health-related issues. However, studies have reported conflicting results, and this issue remains unresolved. This systematic review and meta-analysis aimed: (i) to examine the strength of the association between FATmax and AerT by using the effect size (ES) of correlation coefficient (r) and standardized mean difference (SMD); (ii) to identify potential moderators and their influence on ES variability. This study was registered with PROSPERO (CRD42021239351) and ClinicalTrials (NCT03789045). PubMed and Google Scholar were searched and fourteen articles, consisting of overall 35 ES for r and 26 ES for SMD were included. Obtained ESs were analyzed using a multilevel random-effects meta-analysis. Our results support the presence of a significant association between FATmax and AerT exercise intensities. In conclusion, due to the large ES variance caused by clinical and methodological differences among the studies, we recommend that future studies follow strict standardization of data collection and analysis of FATmax and AerT-related outcomes.

Factors Determining the Agreement between Aerobic Threshold and Point of Maximal Fat Oxidation: Follow-Up on a Systematic Review and Meta-Analysis on Association.

Regular exercise at the intensity matching maximal fat oxidation (FATmax) has been proposed as a key element in both athletes and clinical populations when aiming to enhance the body's ability to oxidize fat. In order to allow a more standardized and tailored training approach, the connection between FATmax and the individual aerobic thresholds (AerT) has been examined. Although recent findings strongly suggest that a relationship exists between these two intensities, correlation alone is not sufficient to confirm that the intensities necessarily coincide and that the error between the two measures is small. Thus, this systematic review and meta-analysis aim to examine the agreement levels between the exercise intensities matching FATmax and AerT by pooling limits of agreement in a function of three parameters: (i) the average difference, (ii) the average within-study variation, and (iii) the variation in bias across studies, and to examine the influence of clinical and methodological inter- and intra-study differences on agreement levels. This study was registered with PROSPERO (CRD42021239351) and ClinicalTrials (NCT03789045). PubMed and Google Scholar were searched for studies examining FATmax and AerT connection. Overall, 12 studies with forty-five effect sizes and a total of 774 subjects fulfilled the inclusion criteria. The ROBIS tool for risk of bias assessment was used to determine the quality of included studies. In conclusion, the overall 95% limits of agreement of the differences between FATmax and AerT exercise intensities were larger than the a priori determined acceptable agreement due to the large variance caused by clinical and methodological differences among the studies. Therefore, we recommend that future studies follow a strict standardization of data collection and analysis of FATmax- and AerT-related outcomes.

Evaluating the influence of differences in methodological approach on metabolic thresholds and fat oxidation points relationship.

In this study, we aimed to determine the exercise intensities eliciting the highest (FATmax) and the lowest (FATmin) fat oxidation rate in male cyclists and to compare these intensities with their individual aerobic (AeT) and anaerobic (AnT) thresholds, respectively. Twenty-two moderately trained male cyclists performed a 2-min stage graded exercise test until exhaustion using breath-by-breath gas analysis to determine maximal oxygen consumption (VO2max). The fat oxidation rate was calculated using a stoichiometric equation, with metabolic thresholds being determined by ventilatory gas analysis. In the present group of subjects, FATmax was found at a 21.34 ± 3.64 ml·kg-1·min-1 corresponding to 45.05 ± 7.68% VO2max. AeT occurred at an exercise intensity of 22.15 ± 4.84 ml·kg-1·min-1, matching 46.76 ± 10.24% VO2max. AnT and FATmin were located at intensities equivalent to 32.56 ± 5.52 ml·kg-1·min-1 and 32.30 ± 5.35 ml·kg-1·min-1 which corresponded to 68.74 ± 11.65 and 68.19 ± 11.29% VO2max, respectively. The correlation between FATmax and AeT was strong (r = 0.80, p < 0.05). No statistical difference was observed between FATmin and AnT (r = 0.99, p < 0.05). The strong relationship between observed indices can be used to provide a more tailored exercise approach.

A systematic comparison of commonly used stoichiometric equations to estimate fat oxidation during exercise in athletes.

BACKGROUND: Over the last half-century, different stoichiometric equations for calculating the energy cost of exercise based upon the combustion of mixtures of carbohydrates, fats, and proteins have been proposed and modified. With the means of indirect calorimetry, while measuring oxygen uptake, carbon dioxide production, and urinary urea nitrogen excretion, the contribution of specific substrates to overall energy production can be estimated. However, even with their long history of application, no previous studies have evaluated whether the use of different stoichiometric equations provides similar or distinct maximal fat oxidation rate (MFO) responses and information regarding MFO location (FATmax) in male athletes. METHODS: Twenty healthy male athletes performed graded exercise testing (GXT) cycle ergometry using breath by breath gas analysis to assess fat oxidation and maximal oxygen uptake. Analysis of variance followed by within-equation effects, within-equation factors, and post hoc pairwise comparisons were used to examine within-equation differences. RESULTS: Compared stoichiometric equations demonstrated significant differences in the mean and maximal fat oxidation rates, varying up to nearly 7%. FATmax differences, however, were not noticed. CONCLUSIONS: Our findings suggest that for within-study designs, the equation used appears to be less important, but when inter-study comparisons are planned, caution is in order due to the presence of inter-equation differences.

Does the aerobic threshold correlate with the maximal fat oxidation rate in short stage treadmill tests?

BACKGROUND: The aim of this study was to identify the exercise intensity that elicited the highest rate of fat utilization (FATmax) and to assess its relationship with the aerobic threshold (AeT) in male athletes. We hypothesized existence of high correlation of these two parameters when a short-staged graded treadmill test with AeT identified through breath-by-breath gas exchange analysis was used. METHODS: Fifty-six trained male athletes (age 25.6±3.4 y, height 197.8±5.6 cm, body mass 98.5±6.6 kg) participated in the study. Pearson correlation coefficient (r) and effect size (R2) were used to evaluate the existence of connection between VO2 at AeT and at FATmax. Maximal oxygen consumption (VO2max) and substrate oxidation were determined using breath-by-breath indirect calorimetry during a short-staged graded treadmill test to exhaustion. RESULTS: Mean VO2max was 52.12±9.02 mL·kg-1·min-1. FATmax and AeT occurred at 47.47±10.59% of VO2max and 45.95±10.21% of VO2max, respectively. Fat utilization at FATmax was 0.59±0.24 g·min-1. A high correlation was found between VO2 at FATmax and at AeT (r=0.88, P<0.01, 95% CI: 0.80 to 0.93). The effect size was 77.44%. CONCLUSIONS: Our results confirm the hypothesis of an existence of a high correlation between AeT and FATmax allowing implementation of more accurate training approach.

Fat Utilization During High-Intensity Exercise: When Does It End?

BACKGROUND: This study examined substrate oxidation at high-intensity exercise and aimed to determine when fat oxidation ends (FATmin). We hypothesized the existence of a connection between the anaerobic threshold (AnT) and FATmin point. METHODS: Breath-by-breath data obtained from indirect calorimetry during a graded treadmill test were used to measure substrate oxidation and maximal oxygen uptake (VO2max) on 47 males (30 athletes (ATL) and 17 non-athletes (NATL)). Pearson correlation coefficient (r) and effect size (R 2) were used to test correlations between VO2 at AnT and at FATmin. RESULTS: Maximal oxygen uptake (VO2max) was 56.17 ± 4.95 and 46.04 ± 3.25 ml kg-1 min-1 in ATL and NATL, respectively. In ATL, AnT was observed at 87.57 ± 1.30 % of VO2max and FATmin was observed at 87.60 ± 1.60 % of VO2max. In NATL, AnT and FATmin were at 84.64 ± 1.10 % of VO2max and 85.25 ± 1.10 % of VO2max, respectively. Our data show large correlations between VO2 at AnT and VO2 at FATmin for ATL (r = 0.99, p < 0.01, 95 % CI 0.99 to 1.00) and NATL (r = 0.97, p < 0.01, 95 % CI 0.91 to 0.98). The effect size of correlations for ATL and NATL were 0.98 and 0.94, respectively. CONCLUSIONS: Our results show high correlation between AnT and FATmin in both ATL and NATL with equal substrate oxidation rates at AnT.