You are looking at 11 - 20 of 1,834 items for :

  • International Journal of Sport Nutrition and Exercise Metabolism x
  • Refine by Access: All Content x
Clear All
Restricted access

Volume 34 (2024): Issue S1 (Feb 2024)

Free access

Abstracts From the 2023 International Sport + Exercise Nutrition Conference

Restricted access

Energy Expenditure of Elite Male and Female Professional Tennis Players During Habitual Training

Daniel G. Ellis, James P. Morton, Graeme L. Close, and Tim F. Donovan

Understanding the daily energy expenditure of athletes during training is important to support recovery, adaptation, and the maintenance of performance. The aim of the current research was to assess the total daily energy expenditure (TDEE) and the acute energy expenditure (EE) of tennis training sessions during habitual training of elite tennis players. Using a cohort study design, 27 (n = 10, male; age; 22.3 ± 3.2 years and n = 17, female; age: 23.8 ± 3.5 years) elite singles tennis players were assessed for TDEE and tennis training EE. Using Actiheart activity monitors during a 2- to 5-day training period, male players were analyzed for 26 days and 33 (1.3 ± 0.5 sessions/day) tennis training sessions, and female players for 43 days and 58 (1.2 ± 0.4 sessions/day) tennis training sessions. Male TDEE (4,708 ± 583 kcal/day) was significantly higher than female (3,639 ± 305 kcal/day). Male absolute and relative tennis training EEs (10.2 ± 2.3 kcal/min and 7.9 ± 1.4 kcal·hr−1·kg−1) were significantly higher than those of females (7.6 ± 1.0 kcal/min and 6.8 ± 0.9 kcal·hr−1·kg−1). The resting metabolic rate was assessed via indirect calorimetry. The physical activity level for both groups was 2.3 AU. The TDEE of male and female players during habitual training now highlights the continual cycle of high energy demands experienced by the elite tennis player. The broad ranges of TDEE and EE reported here suggest individual assessment and nutritional planning be prioritized, with a particular focus on carbohydrate requirements.

Restricted access

Caffeine Does Not Alter Performance, Perceptual Responses, and Oxidative Stress After Short Sprint Interval Training

Mauro F. Bernardo, Alysson Enes, Elisangela F. Rezende, Alexandre R. Okuyama, Ragami C. Alves, Murilo de Andrade, Ana Carolina G. Macedo, Marcelo Paes de Barros, Darren G. Candow, Scott C. Forbes, and Tácito P. Souza-Junior

Despite the abundance of research investigating the efficacy of caffeine supplementation on exercise performance, the physiological and biochemical responses to caffeine supplementation during intermittent activities are less evident. This study investigated the acute effects of caffeine supplementation on measures of exercise performance, ratings of perceived exertion, and biomarkers of oxidative stress induced by an acute bout of sprint interval training. In a randomized crossover design, 12 healthy males (age: 26 ± 4 years, height: 177.5 ± 6 cm, body mass: 80.7 ± 7.6 kg) ingested 6 mg/kg of caffeine or placebo 60 min prior to performing sprint interval training (12 × 6 s “all-out sprints” interspersed by 60 s of rest). Performance scores and ratings of perceived exertion were assessed after every sprint. Blood samples were collected before supplementation, prior to and following each sprint, and 5 and 60 min after the last sprint. Caffeine had no effect on any performance measures, ratings of perceived exertion, or biomarkers of oxidative stress (p > .05). In conclusion, caffeine supplementation does not improve performance or decrease oxidative stress after an acute bout of sprint interval training.

Restricted access

Timing of Caffeine Ingestion Does Not Improve Three-Point Shooting Accuracy in College Basketball Players

Zhi Sen Tan, Rachelle Yahn Yee Sim, Masato Kawabata, Dorrain Yanwen Low, Yulan Wang, and Stephen F. Burns

This study investigated the effects of the timing of caffeine (3 mg/kg body mass) ingestion on three-point shooting accuracy and other performance parameters during a basketball exercise simulation test (BEST). Eighteen college basketball players (mean ± SD: age = 24.4 ± 1.5 years, height = 181.7 ± 9.5 cm, body mass = 80.9 ± 13.2 kg) underwent one familiarization trial and three main conditions in a randomized order: (a) placebo (maltodextrin) and placebo, (b) caffeine and placebo, and (c) placebo and caffeine. Participants ingested either the placebo or caffeine pill 75 and 15 min before performing four quarters of the BEST and a three-point shooting protocol. During each quarter, participants completed 16 rounds of the BEST and ten three-point shots. Vertical jump height, 6 m sprint timing, BEST completion timing, three-point shooting accuracy, heart rate, rate of perceived exertion, blood glucose, blood lactate, and psychological measures pertaining to performance were measured. The BEST completion timing differed among conditions (placebo and placebo = 26.4 ± 2.0 s, caffeine and placebo = 25.8 ± 2.0 s, placebo and caffeine = 25.9 ± 2.1 s; p = .031) but not three-point shooting accuracy (placebo and placebo = 12.33 ± 4.10; caffeine and placebo = 12.61 ± 2.81; placebo and caffeine = 11.67 ± 3.77; p = .648), vertical jump height, or sprint times. Manipulating ingestion timing of caffeine did not improve three-point shooting accuracy, vertical jump height, or 6 m sprint timings, but caffeine can improve performance times during simulated basketball exercise irrespective of ingestion timing.

Restricted access

Acute Beetroot Juice Supplementation Has No Effect on Upper- and Lower-Body Maximal Isokinetic Strength and Muscular Endurance in International-Level Male Gymnasts

Ozcan Esen, Joseph Fox, Raci Karayigit, and Ian Walshe

Nitrate ( NO 3 ) has properties that can improve muscle function, leading to improvements in metabolic cost of exercise as well as enhance force production. Gymnastics is a whole-body sport, involving events that demand a high level of strength and fatigue resistance. However, the effect of NO 3 supplementation on both upper- and lower-body function in gymnasts is unknown. This study examined the effect of acute beetroot juice (BRJ) supplementation on isokinetic strength and endurance of the upper- and lower-body in highly trained international-level male gymnasts. In a double-blind, randomized crossover design, 10 international-level male gymnasts completed two acute supplementation periods, consuming either 2 × 70 ml NO 3 -rich (∼12.8 mmol/L of NO 3 ) or NO 3 -depleted (PLA) BRJ. Maximal strength of the upper-leg and upper-arm at 60°/s, 120°/s, 180°/s, and 300°/s, and muscular endurance (50 repeated isokinetic contractions at 180°/s) were assessed. Plasma NO 3 (BRJ: 663 ± 164 μM, PLA: 89 ± 48 μM) and nitrite ( NO 2 ) concentrations (BRJ: 410 ± 137 nmol/L, PLA: 125 ± 36 nmol/L) were elevated following BRJ compared to PLA (both p < .001). Maximal strength of knee and elbow extensors and flexors did not differ between supplements (p > .05 for all velocities). Similarly, fatigue index of knee and elbow extension and flexion was not different between supplements (all p > .05). Acute BRJ supplementation, containing ∼12.8 mmol/L of NO 3 , increased plasma NO 3 and NO 2 concentrations, but did not enhance isokinetic strength or fatigue resistance of either upper or lower extremities in international-level male gymnasts.

Restricted access

Pharmacokinetic Profile of Caffeine and Its Two Main Metabolites in Dried Blood Spots After Five Different Oral Caffeine Administration Forms—A Randomized Crossover Study

Chiara Tuma, Andreas Thomas, Lasse Trede, Hans Braun, and Mario Thevis

Caffeine is an ergogenic substance that is consumed globally in many forms. The use of buccally absorbable formulations instead of gastrointestinal uptake has become increasingly popular over the years, especially when accelerated absorption with minimal gastrointestinal stress is desired. This study investigated the impact of five different formulations and administration routes of caffeine on the whole blood concentrations of caffeine, paraxanthine, and theobromine: caffeinated capsules, tablets, shots, pouches, and chewing gums. A uniform dose of caffeine (200 mg) was administered to 16 healthy recreational athletes (26.0 ± 2.1 years) using a randomized crossover design. Samples were taken in the form of dried blood spots at 16 different time points in a 2-hr timeframe after drug administration. The samples were analyzed using a validated liquid chromatography–tandem mass spectrometry method. The results for caffeine showed no significant differences in the overall bioavailability (area under the concentration–time curve), maximal concentration, and time to maximum concentration. However, when analyzing the bioavailability of caffeine in the first 5, 10, and 15 min, the liquid caffeine formulation was superior to other administered forms (p < .05). This indicates that caffeine solubility has a major influence on its absorption rate. In sports, the rate of caffeine absorption must be considered, not only when ingesting anhydrous caffeine, but also when choosing buccal absorption. These findings imply that general guidelines for ergogenic caffeine use should consider the formulation used and, accordingly, the corresponding route of absorption.

Restricted access

Sex Differences in Hydration Biomarkers and Test–Retest Reliability Following Passive Dehydration

Colin S. Doherty, Lauren V. Fortington, and Oliver R. Barley

This study investigated (a) differences between males and females for changes in serum, tear, and urine osmolality, hematocrit, and urine specific gravity following acute passive dehydration and (b) assessed the reliability of these biomarkers separately for each sex. Fifteen males (age: 26.3 ± 3.5 years, body mass: 76 ± 7 kg) and 15 females (age: 28.8 ± 6.4 years, body mass: 63 ± 7 kg) completed a sauna protocol twice (5–28 days apart), aiming for 4% body mass loss (BML). Urine, blood, and tear markers were collected pre- and postdehydration, and change scores were calculated. Male BML was significantly greater than that of females in Trial 1 (3.53% ± 0.55% vs. 2.53% ± 0.43%, p < .001) and Trial 2 (3.36% ± 0.66% vs. 2.53% ± 0.44%, p = .01). Despite significant differences in BML, change in hematocrit was the only change marker that displayed a significant difference in Trial 1 (males: 3% ± 1%, females: 2% ± 1%, p = .004) and Trial 2 (males: 3% ± 1%, females: 1% ± 1%, p = .008). Regression analysis showed a significant effect for sex (male) predicting change in hematocrit (β = 0.8, p = .032) and change in serum osmolality (β = −3.3, p = .005) when controlling for BML but not for urinary or tear measures. The intraclass correlation coefficients for females (ICC 2, 1) were highest for change in urine specific gravity (ICC = .62, p = .006) and lowest for change in tear osmolarity (ICC = −.14, p = .689), whereas for males, it was posthematocrit (ICC = .65, p = .003) and post tear osmolarity (ICC = .18, p = .256). Generally, biomarkers showed lower test–retest reliability in males compared with females but, overall, were classified as poor–moderate in both sexes. These findings suggest that the response and reliability of hydration biomarkers are sex specific and highlight the importance of accounting for BML differences.

Restricted access

Sweat Characteristics and Fluid Balance Responses During Two Heat Training Camps in Elite Female Field Hockey Players

Paul S.R. Goods, Bradley Wall, Brook Galna, Alannah K.A. McKay, Denise Jennings, Peter Peeling, and Greig Watson

We examined the sweat characteristics and fluid balance of elite female field hockey players during two heat training camps. Fourteen elite female field hockey players from the Australian national squad participated in two heat training camps held ∼6 months apart, following winter- (Camp 1) and summer-based training (Camp 2). Daily waking body mass (BM) and urine specific gravity (USG) were collected, along with several markers of sweat and fluid balance across two matches per camp. There was a 19% mean reduction in estimated whole-body sweat sodium concentration from Camp 1 (45.8 ± 6.5 mmol/L) to Camp 2 (37.0 ± 5.0 mmol/L; p < .001). Waking urine specific gravity ≥ 1.020 was observed in 31% of samples, with no significant differences in mean urine specific gravity or BM between camps (p > .05), but with substantial interindividual variation. Intramatch sweat rates were high (1.2–1.8 L/hr), with greater BM losses in Camp 1 (p = .030), resulting in fewer players losing ≥2% BM in Camp 2 (0%–8%), as compared with Camp 1 (36%–43%; p = .017). Our field data suggest that elite female field hockey players experience substantial sweat losses during competition in the heat regardless of the season. In agreement with previous findings, we observed substantial interindividual variation in sweat and hydration indices, supporting the use of individualized athlete hydration strategies.

Open access

Auditing the Representation of Females Versus Males in Heat Adaptation Research

Monica K. Kelly, Ella S. Smith, Harry A. Brown, William T. Jardine, Lilia Convit, Steven J. Bowe, Dominique Condo, Joshua H. Guy, Louise M. Burke, Julien D. Périard, Rhiannon M.J. Snipe, Rodney J. Snow, and Amelia J. Carr

The aim of this audit was to quantify female representation in research on heat adaptation. Using a standardized audit tool, the PubMed database was searched for heat adaptation literature from inception to February 2023. Studies were included if they investigated heat adaptation among female and male adults (≥18–50 years) who were free from noncommunicable diseases, with heat adaptation the primary or secondary outcome of interest. The number and sex of participants, athletic caliber, menstrual status, research theme, journal impact factor, Altmetric score, Field-Weighted Citation Impact, and type of heat exposure were extracted. A total of 477 studies were identified in this audit, including 7,707 participants with ∼13% of these being female. Most studies investigated male-only cohorts (∼74%, n = 5,672 males), with ∼5% (n = 360 females) including female-only cohorts. Of the 126 studies that included females, only 10% provided some evidence of appropriate methodological control to account for ovarian hormone status, with no study meeting best-practice recommendations. Of the included female participants, 40% were able to be classified to an athletic caliber, with 67% of these being allocated to Tier 2 (i.e., trained/developmental) or below. Exercise heat acclimation was the dominant method of heat exposure (437 interventions), with 21 studies investigating sex differences in exercise heat acclimation interventions. We recommend that future research on heat adaptation in female participants use methodological approaches that consider the potential impact of sexual dimorphism on study outcomes to provide evidence-based guidelines for female athletes preparing for exercise or competition in hot conditions.