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Longitudinal Changes in Body Composition and Resting Metabolic Rate in Male Professional Flat Jockeys: Preliminary Outcomes and Implications for Future Research Directions

George Wilson, Carl Langan-Evans, Dan Martin, Andreas M. Kasper, James P. Morton, and Graeme L. Close

Jockeys are unique given that they make weight daily and, therefore, often resort to fasting and dehydration. Through increasing daily food frequency (during energy deficit), we have reported short-term improvements in jockey’s body composition. While these changes were observed over 6–12 weeks with food provided, it is unclear whether such improvements can be maintained over an extended period during free-living conditions. We, therefore, assessed jockeys over 5 years using dual X-ray absorptiometry, resting metabolic rate, and hydration measurements. Following dietary and exercise advice, jockeys reduced fat mass from baseline of 7.1 ± 1.4 kg to 6.1 ± 0.7 kg and 6.1 ± 0.6 kg (p < .001) at Years 1 and 5, respectively. In addition, fat-free mass was maintained with resting metabolic rate increasing significantly from 1,500 ± 51 kcal/day at baseline to 1,612 ± 95 kcal/day and 1,620 ± 92 kcal/day (p < .001) at Years 1 and 5, respectively. Urine osmolality reduced from 816 ± 236 mOsmol/L at baseline to 564 ± 175 mOsmol/L and 524 ± 156 mOsmol/L (p < .001) at Years 1 and 5, respectively. The percent of jockeys consuming a regular breakfast significantly increased from 48% at baseline to 83% (p = .009) and 87% (p = .003) at Years 1 and 5, alongside regular lunch from 35% to 92% (p < .001) and 96% (p < .001) from baseline to Years 1 and 5, respectively. In conclusion, we report that improved body composition can be maintained in free-living jockeys over a 5-year period when appropriate guidance has been provided.

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Abstracts From the 2022 International Sport + Exercise Nutrition Conference

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Volume 33 (2023): Issue S1 (Mar 2023)

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Volume 33 (2023): Issue 2 (Mar 2023)

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Comment on: “Creatine Monohydrate Supplementation, but not Creatyl-L-Leucine Increased Muscle Creatine Content in Healthy Young Adults: A Double-Blind Placebo-Controlled Trial”

Guillermo Escalante and Dean St. Mart

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Reply to G. Escalante and D. St. Mart

Andrew T. Askow and Nicholas A. Burd

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Chronic Statin Treatment Does Not Impair Exercise Lipolysis or Fat Oxidation in Exercise-Trained Individuals With Obesity and Dyslipidemia

Laura Alvarez-Jimenez, Alfonso Moreno-Cabañas, Felix Morales-Palomo, Juan F. Ortega, and Ricardo Mora-Rodriguez

Objective: To determine whether statin medication in individuals with obesity, dyslipidemia, and metabolic syndrome affects their capacity to mobilize and oxidize fat during exercise. Methods: Twelve individuals with metabolic syndrome pedaled during 75 min at 54 ± 13% V ˙ O 2 max (5.7 ± 0.5 metabolic equivalents) while taking statins (STATs) or after 96-hr statin withdrawal (PLAC) in a randomized double-blind fashion. Results: At rest, PLAC increased low-density lipoprotein cholesterol (i.e., STAT 2.55 ± 0.96 vs. PLAC 3.16 ± 0.76 mmol/L; p = .004) and total cholesterol blood levels (i.e., STAT 4.39 ± 1.16 vs. PLAC 4.98 ± 0.97 mmol/L; p = .008). At rest, fat oxidation (0.99 ± 0.34 vs. 0.76 ± 0.37 μmol·kg−1·min−1 for STAT vs. PLAC; p = .068) and the rates of plasma appearance of glucose and glycerol (i.e., Ra glucose–glycerol) were not affected by PLAC. After 70 min of exercise, fat oxidation was similar between trials (2.94 ± 1.56 vs. 3.06 ± 1.94 μmol·kg−1·min−1, STA vs. PLAC; p = .875). PLAC did not alter the rates of disappearance of glucose in plasma during exercise (i.e., 23.9 ± 6.9 vs. 24.5 ± 8.2 μmol·kg−1·min−1 for STAT vs. PLAC; p = .611) or the rate of plasma appearance of glycerol (i.e., 8.5 ± 1.9 vs. 7.9 ± 1.8 μmol·kg−1·min−1 for STAT vs. PLAC; p = .262). Conclusions: In patients with obesity, dyslipidemia, and metabolic syndrome, statins do not compromise their ability to mobilize and oxidize fat at rest or during prolonged, moderately intense exercise (i.e., equivalent to brisk walking). In these patients, the combination of statins and exercise could help to better manage their dyslipidemia.

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Individual Variability Is More Important Than Analytical Methods When Calculating Relative Speed of Beverage Bioavailability

Edward M. Balog, Mateo Golloshi, HyunGyu Suh, and Melinda Millard-Stafford

Deuterium oxide (D2O) appearance in blood is a marker of fluid bioavailability. However, whether biomarker robustness (e.g., relative fluid delivery speed) is consistent across analytical methods (e.g., cavity ring-down spectroscopy) remains unclear. Fourteen men ingested fluid (6 ml/kg body mass) containing 0.15 g/kg D2O followed by 45 min blood sampling. Plasma (D2O) was detected (n = 8) by the following: isotope-ratio mass spectrometry after vapor equilibration (IRMS-equilibrated water) or distillation (IRMS-plasma) and cavity ring-down spectroscopy. Two models calculated D2O halftime to peak (t 1/2max): sigmoid curve fit versus asymmetric triangle (TRI). Background (D2O) differed (p < .001, η2 = .98) among IRMS-equilibrated water, IRMS-plasma, and cavity ring-down spectroscopy (152.2 ± 0.8, 147.2 ± 1.5, and 137.7 ± 2.2 ppm), but did not influence (p > .05) D2O appearance (Δppm), time to peak, or t 1/2max. Stratifying participants based on mean t 1/2max (12 min) into “slow” versus “fast” subgroups resulted in a 5.8 min difference (p < .001, η2 = .73). Significant t 1/2max model (p = .01, η2 = .44) and Model × Speed Subgroup interaction (p = .005, η2 = .50) effects were observed. Bias between TRI and sigmoid curve fit increased with t 1/2max speed: no difference (p = .75) for fast (9.0 min vs. 9.2 min, respectively) but greater t 1/2max (p = .001) with TRI for the slow subgroup (16.1 min vs. 13.7 min). Fluid bioavailability markers are less influenced by which laboratory method is used to measure D2O as compared with the individual variability effects that influence models for calculating t 1/2max. Thus, TRI model may not be appropriate for individuals with slow fluid delivery speeds.

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No Effect of Acute Balenine Supplementation on Maximal and Submaximal Exercise Performance in Recreational Cyclists

Sarah de Jager, Stefaan Van Damme, Siegrid De Baere, Siska Croubels, Ralf Jäger, Martin Purpura, Eline Lievens, Jan G. Bourgois, and Wim Derave

Carnosine (β-alanyl-L-histidine) and its methylated analogues anserine and balenine are highly concentrated endogenous dipeptides in mammalian skeletal muscle that are implicated in exercise performance. Balenine has a much better bioavailability and stability in human circulation upon acute ingestion, compared to carnosine and anserine. Therefore, ergogenic effects observed with acute carnosine and anserine supplementation may be even more pronounced with balenine. This study investigated whether acute balenine supplementation improves physical performance in four maximal and submaximal exercise modalities. A total of 20 healthy, active volunteers (14 males; six females) performed cycling sprints, maximal isometric contractions, a 4-km TT and 20-km TT following either preexercise placebo or 10 mg/kg of balenine ingestion. Physical, as well as mental performance, along with acid–base balance and glucose concentration were assessed. Balenine was unable to augment peak power (p = .3553), peak torque (p = .3169), time to complete the 4 km (p = .8566), nor 20 km time trial (p = .2660). None of the performances were correlated with plasma balenine or CN1 enzyme activity. In addition, no effect on pH, bicarbonate, and lactate was observed. Also, the supplement did not affect mental performance. In contrast, glucose remained higher during and after the 20 km time trial following balenine ingestion. In conclusion, these results overall indicate that the functionality of balenine does not fully resemble that of carnosine and anserine, since it was unable to elicit performance improvements with similar and even higher plasma concentrations.

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Volume 33 (2023): Issue 1 (Jan 2023)