Int J Sport Nutr Exerc Metab [JOURNAL]
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200 papers
A Novel Honey Powder-Based Supplement Containing Carbohydrate and Protein Did Not Improve Endurance Performance in Recreationally Trained Cyclists.
Toniazzo T, Azevedo RA, Oliveira TN … +6 more , de Souza RAS, Marinho LSV, Roschel H, Gualano B, Saunders B, Tadini CC
Int J Sport Nutr Exerc Metab · 2025 Nov · PMID 40812383 · Publisher ↗
Sports supplements composed of carbohydrate and protein are widely used by endurance athletes and recreational practitioners, mostly aimed at improving performance. This study investigated the effect of a novel carbohydr...
Sports supplements composed of carbohydrate and protein are widely used by endurance athletes and recreational practitioners, mostly aimed at improving performance. This study investigated the effect of a novel carbohydrate + protein honey powder (HP) product on endurance cycling performance and physiological and perceptual responses using a double-blind, crossover, counterbalanced, placebo-controlled (PLA) design. Twelve male cyclists exercised for 100 min (i.e., 5 min at 1 W/kg of body mass, followed by three sets of 10-min stages at 1.5, 2.0, and 2.5 W/kg, followed by 5 min at 1 W/kg), followed by a 20-min self-paced time trial (20-min TT). Blood glucose, lactate, pH, bicarbonate, heart rate, ratings of perceived exertion, and side effects were analyzed throughout the 100-min cycling protocol and the 20-min TT. The 20-min TT performance was similar between HP and PLA (total work done: 294 ± 40 vs. 292 ± 44 kJ, p = .72; mean power output: 245 ± 33 vs. 243 ± 37 W, p = .61), as was blood glucose, lactate, pH, and ratings of perceived exertion either during the 100 or 20-min TT protocols (all p > .05). Blood bicarbonate was lower in HP compared with PLA throughout the 100-min protocol (p = .01), and heart rate was higher in HP compared with PLA during the 20-min TT (p = .01). Finally, HP supplementation did not elicit greater side effects compared with PLA, either during the 100 or the 20-min TT protocols (all p > .05). This novel HP supplement did not improve endurance performance in this study, though future research with higher doses is encouraged.
High-Protein Time-Restricted Eating Alongside Resistance Training Reduces Adipose Tissue While Preserving Fat-Free Mass in Women With Overweight: A Randomized Controlled Trial.
Bagherpour F, Arazi H, Rajabi H … +1 more , Campbell BI
Int J Sport Nutr Exerc Metab · 2025 Nov · PMID 40796095 · Publisher ↗
BACKGROUND: Time-restricted eating (TRE), a subtype of intermittent fasting, has gained significant popularity in recent years. This dietary approach, when combined with resistance training (RT), has demonstrated potenti...
BACKGROUND: Time-restricted eating (TRE), a subtype of intermittent fasting, has gained significant popularity in recent years. This dietary approach, when combined with resistance training (RT), has demonstrated potential benefits for body composition and physiological parameters. OBJECTIVE: This study aimed to investigate the effects of TRE and high-protein consumption on visceral adipose tissue (VAT), subcutaneous adipose tissue, leptin, and ghrelin levels in young women with overweight engaged in RT. METHODS: Thirty-two women with overweight (body mass index 25-30 kg/m2), aged 18-30 years, were randomly assigned to four groups: TRE with high protein (THP), TRE with regular protein, high protein only (HP), and regular protein only. All participants underwent RT and adhered to a 25% calorie-restricted diet. The high-protein groups received 1.6 g·kg-1·day-1 of protein. Body composition, blood biomarkers, and muscle functions were assessed. RESULTS: Significant reductions in VAT (p < .001) and subcutaneous adipose tissue (p < .001) were observed across all groups, with the THP group exhibiting the greatest decrease in VAT (Δ = -146.98 ± 12.66, d = -1.867). Leptin levels also showed a significant decrease in all groups (p < .001). However, significant differences in leptin reduction were detected only between THP versus regular protein only (p = .045) and TRE with regular protein versus regular protein only (p = .034) groups. Plasma ghrelin levels remained unchanged across all groups. Notably, the high-protein groups (THP and high protein only) demonstrated a significant increase in fat-free mass (Δ THP = 1.06 ± 1.75, Δ HP = 2.37 ± 0.64). CONCLUSION: An 8-week program combining TRE, high-protein intake, and RT effectively reduced VAT, subcutaneous adipose tissue, and leptin levels while preserving muscle mass in women with overweight. This intervention did not significantly alter plasma ghrelin levels.
Could It Bee? Honey Ingestion Induces Comparable Metabolic Responses to Traditional Carbohydrate-Based Sports Nutrition Product During 3-Hr Steady-State Cycling and Subsequent Exercise Capacity Test.
Fortis HO, Ravikanti S, Barrett JS … +5 more , Lopez EM, Bampouras TM, Haworth JJ, Areta JL, Pugh JN
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40675563 · Publisher ↗
The present study investigated the effects of honey compared with a traditional carbohydrate based sports nutrition product (TRAD-CHO) on metabolic and gastrointestinal responses during exercise, as well as exercise capa...
The present study investigated the effects of honey compared with a traditional carbohydrate based sports nutrition product (TRAD-CHO) on metabolic and gastrointestinal responses during exercise, as well as exercise capacity. In a randomized crossover design 12 trained males ingested 90 g × hr-1 of carbohydrate in the form of TRAD-CHO, or honey (HONEY) during 180 min of steady-state cycling undertaken at 90% lactate threshold, followed by a capacity test consisting of a time to fatigue at 120% of lactate threshold. Mean total CHO oxidation (HONEY 2.47 ± 0.37 g × min-1, TRAD-CHO 2.41 ± 0.39 g × min-1) and fat oxidation (HONEY 0.44 ± 0.12 g/min, TRAD-CHO 0.42 ± 0.10 g/min) were not different between trials during steady-state cycling (p = .517). The overall incidence of gastrointestinal symptoms rated as "moderately severe" or worse was low. There was no difference in time to fatigue (p = .517). There was no difference in breath hydrogen postexercise (p = .319) and the number of participants in each condition, with >20 parts per million rise from baseline not significantly different between conditions (6: SPORT, 7 HONEY: p = 1.00). From these data, honey could be a potentially alternative fueling option to commercial TRAD-CHO, with the current data providing no evidence of any systematic differences between the conditions on whole-body carbohydrate oxidation and endurance capacity test.
The Acute Effects of Caffeine and Normobaric Hypoxia on Cardiorespiratory Exercise Responses in Healthy Adults: A Randomized Controlled Trial.
Narang BJ, Štritof A, Debevec T
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40675560 · Publisher ↗
The ergogenic effects of caffeine for endurance performance at sea level are well established. However, whether caffeine enhances exercise capacity or modulates cardiorespiratory responses in hypoxia remains unclear. Twe...
The ergogenic effects of caffeine for endurance performance at sea level are well established. However, whether caffeine enhances exercise capacity or modulates cardiorespiratory responses in hypoxia remains unclear. Twenty-nine healthy, active volunteers (14 women) completed four tests in a pseudorandomized order, comprising 10 min of steady-state cycling (40% normoxic maximal aerobic power) followed by incremental exercise tests to exhaustion. Participants consumed 6 mg/kg body mass anhydrous caffeine, or placebo, 45 min before exercise. Tests were performed while breathing room air or a hypoxic gas mixture (simulating ∼3,500 m). At peak exercise intensity, oxygen uptake was affected by condition (hypoxia vs. normoxia; 44.8 ± 7.3 vs. 51.4 ± 7.9 ml·kg-1·min-1; p < .001) but not supplement (caffeine vs. placebo; 48.2 ± 8.2 vs. 48.0 ± 8.4 ml·kg-1·min-1; p = .501). Maximal aerobic power and pulse oxygen saturation were lower in hypoxia (both p < .001), but unaffected by caffeine (p = .061 and .898, respectively). Pulmonary ventilation was unaffected by hypoxia (p = .154) or caffeine (p = .117). Heart rate was higher in normoxia and with caffeine (both p < .001). During steady-state cycling, hypoxia (p < .001) and caffeine (p = .026) increased pulmonary ventilation. However, the hypoxia-induced pulse oxygen saturation decrease (p < .001) was not attenuated with caffeine (interaction p = .283). Perceived exertion was higher in hypoxia (p < .001) and lower with caffeine (p = .026). Caffeine increased vastus lateralis oxygenation in hypoxia (caffeine vs. placebo; 52 ± 8 vs. 50 ± 10%; p = .020) but not in normoxia (caffeine vs. placebo; 59 ± 7 vs. 59 ± 8%; p > .999). Overall, caffeine did not enhance exercise capacity in either environmental condition. However, during steady-state cycling, caffeine enhanced pulmonary ventilation, reduced perceived exertion, and mitigated hypoxia-induced muscle oxygenation reductions.
No Effect of Topical Application of a Commercial Magnesium Gel on Exercise Recovery in Active Individuals.
Coates AM, Patel DV, Binet ER … +1 more , Gibala MJ
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40537122 · Publisher ↗
Oral magnesium supplementation can reduce muscle soreness and muscle damage markers after unaccustomed exercise. However, the effectiveness of topical magnesium applications remains unclear. This randomized, double-blind...
Oral magnesium supplementation can reduce muscle soreness and muscle damage markers after unaccustomed exercise. However, the effectiveness of topical magnesium applications remains unclear. This randomized, double-blind, parallel-design study investigated whether a commercial magnesium gel could reduce the perception of muscle soreness and muscle damage markers following an acute bout of unaccustomed exercise. Healthy active participants (n = 35) performed a 40-min bout of downhill treadmill running. Magnesium (Mg) or placebo (Pla) gels were administered to each thigh 10 min before and immediately after exercise. Measurements were made before (Pre) and immediately (Post), 24 hr, and 48 hr after exercise. The primary outcome was muscle soreness using a 0-100 visual analog scale after a sit-to-stand maneuver. Secondary outcomes included peak isometric knee extensor strength, plasma creatine kinase, and serum interleukin-6. There were no differences between treatments on any outcome. Compared with Pre (Mg: 4 ± 5, Pla: 4 ± 5 a.u.), muscle soreness was higher post (Mg: 28 ± 20, Pla: 21 ± 14) and after 24 hr (Mg: 43 ± 27, Pla: 41 ± 26) and 48 hr (Mg: 42 ± 31, Pla: 32 ± 23) (all main effects, p < .0001). Interleukin-6 was higher Post (Mg: 1.8 ± 0.7, Pla: 1.6 ± 0.7 pg/ml) versus Pre (Mg: 1.1 ± 0.8, Pla: 1.1 ± 0.6; main effect, p = .006), and creatine kinase was higher Post (Mg: 111 ± 57, Pla: 121 ± 44 U/L), 24 hr (Mg: 216 ± 113, Pla: 228 ± 97), and 48 hr (Mg: 136 ± 45, Pla: 179 ± 85) versus Pre (Mg: 93 ± 54, Pla: 91 ± 30; all main effects, p < .001). Knee extensor strength was reduced after exercise (main effect, p = .04). The Mg gel did not reduce muscle soreness or muscle damage markers after unaccustomed exercise compared with Pla. The dose (0.53 mg/ml) or application protocol may have been insufficient to elicit a meaningful effect.
Negligible Effects of Fructose-Glucose Composite Carbohydrates on Performance Across a Prolonged Soccer Match Simulation Compared With a Glucose-Only Control in Semiprofessional Soccer Players.
Fischer A, Corr L, Birdsey LP … +11 more , Hearris M, Morgan P, Hodson N, Martinho D, Fleming J, Mohr M, Krustrup P, Russell M, Sale C, Harper LD, Field A
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40537112 · Publisher ↗
Higher carbohydrate availability, achieved through combined intake of glucose and fructose, has been shown to enhance endurance performance. This study examined the effects of higher carbohydrate doses containing a fruct...
Higher carbohydrate availability, achieved through combined intake of glucose and fructose, has been shown to enhance endurance performance. This study examined the effects of higher carbohydrate doses containing a fructose-glucose mixture (1:2 ratio) compared with lower doses containing only glucose on performance during a 120-min simulated soccer match. Fifteen semiprofessional soccer players (seven males and eight females) completed two 120-min soccer-specific exercise sessions in a randomized and crossover design. Participants consumed either 60 g/hr glucose or a combination of 0.5 g/min fructose and 1.0 g/min glucose (90 g/hr) at preexercise, halftime, full time, and midway through extra time. Measures, including gastrointestinal discomfort, mental fatigue, passing accuracy, neuromuscular performance (reactive strength index, countermovement jump height, and peak power output), and sprint performance (15- and 30-m sprints), were assessed at 0, 45, 90, and 120 min. Blood glucose and lactate concentrations were assessed every 15 min. Fructose-glucose coingestion elevated blood glucose concentration from 105 min (p = .006, d = 1.2) but did not maintain performance (p > .05). Gastrointestinal symptoms of gastric reflux at 45 min (p = .011, d = 0.9), fullness at 90 min (p = .013, d = 0.9), and flatulence at 120 min worsened in the glucose group (p = .003, d = 1.1). Abdominal cramps were greater in the fructose-glucose group at 45 (p < .001, d = 1.7) and 90 min (p < .001, d = 1.6). Although supplementation did not influence any other variables (p > .05), countermovement jump height, peak power output, and sprint performance were negatively influenced by exercise in both conditions (p < .05). A higher carbohydrate dosage of fructose-glucose coingestion increases blood glucose concentrations but does not mitigate technical and neuromuscular performance impairments during a prolonged simulated soccer match.
Comparison of Ramp and Step Graded Cardiopulmonary Exercise Tests for the Estimate of Substrate Oxidation Rates in Recreationally Active Individuals.
Nesti L, Santoni L, Frascerra S … +2 more , Chiriacò M, Natali A
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40447267 · Publisher ↗
Fat oxidation rates are key determinants of exercise capacity and metabolic health, evaluated by indirect calorimetry during step graded exercise test. We sought to verify whether indirect calorimetry applied to ramp gra...
Fat oxidation rates are key determinants of exercise capacity and metabolic health, evaluated by indirect calorimetry during step graded exercise test. We sought to verify whether indirect calorimetry applied to ramp graded exercise test provides comparable results to the reference test and to identify the physiological bases of possible dissimilarities. To this aim, 14 healthy volunteers performed two cardiopulmonary exercise tests with concomitant stress echocardiography according to standard protocols until limit of tolerance on separate days, in randomized order. Compared at matched exercise intensities, expressed as percentage of estimated maximal rate of oxygen uptake (%V˙O2max), indirect calorimetry applied to ramp provided identical kinetics of macronutrient oxidation, with a negligible (7%, p > .05) constant overestimation of fat and underestimation of carbohydrate oxidation rates. Despite identical hemodynamic and ventilatory parameters throughout the tests, we observed a minute downward shift of the Δ V˙CO2/Δ V˙O2 intercept with ramp in comparison to step (-0.05 ± 0.09 L/min; p = .077) due to delayed alignment of gas exchange to work rate, which explains the differences in substrate oxidation values between the two tests. Ramp macronutrient oxidation rates were fully normalized by correcting the stoichiometric equations for the Δ V˙CO2/Δ V˙O2 intercept difference. In conclusion, cardiopulmonary and metabolic responses are dependent on exercise intensity and not on the protocol used. Indirect calorimetry applied to ramp protocols correctly identifies the kinetics of macronutrient oxidation while introducing minimal differences in the absolute values due to different gas-exchange response that can be mathematically corrected by applying the Δ V˙CO2/Δ V˙O2 correction factor.
Isotope Dilution for Measuring Total Energy Expenditure, Water Turnover, and Total Body Water in Athletes: A Systematic Review.
Jesus F, Costello NB, Kondo E … +15 more , Francisco R, Nunes CL, Matu J, Sardinha LB, Murphy-Alford AJ, Luke AH, Pontzer H, Rood J, Sagayama H, Westerterp KR, Wong WW, Yamada Y, Schoeller DA, Speakman JR, Silva AM
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40404134 · Publisher ↗
Isotope-based tracer methods allow the determination of total energy expenditure (TEE), water turnover (rH2O), and total body water (TBW) in free-living conditions. These methods have exciting applications in athletes. H...
Isotope-based tracer methods allow the determination of total energy expenditure (TEE), water turnover (rH2O), and total body water (TBW) in free-living conditions. These methods have exciting applications in athletes. However, the limited number of available measurements constrains their applicability. The aim was to describe the application of isotope dilution techniques for measuring TEE, rH2O, and TBW in athletic populations. A comprehensive search (https://doi.org/10.17605/OSF.IO/7932T) was performed in three databases: PubMed, EBSCO (CINAHL, MEDLINE, and SPORTDiscus), and Cochrane Library. A total of 1,540 records were identified (564 excluded) and 174 through other sources. After excluding 53 duplicates, 1,097 articles were screened. A total of 121 studies were included, totaling 3,244 measurements from different types of sports, age range, and tier level, with 1,020 from female athletes and 139 measurements where sex was not reported. For TEE, 75 studies were included with values ranging from 1,939 to 10,070 kcal/day. For rH2O, 15 studies were included with values ranging from 2.7 to 13.4 L/day. For TBW, 77 studies were included with values ranging from 29.8 to 76.8 kg. Variability was observed across the studies among the variables of interest. Overall, males showed higher TEE, rH2O, and TBW values than females, with endurance sports showing the greatest variability in energy and water flux, and TBW values varying most in team and mixed sports. Future research should increase representation of females, athletes with disabilities, and Tier 5 "world-class" athletes to establish normative values across sports, age groups, and sex while applying standardized isotope dilution methodologies.
Effects of Carotenoid Supplementation on Exercise-Induced Oxidative Stress: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.
Ye X, Li Y
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40404130 · Publisher ↗
OBJECTIVE: This study aims to investigate the potential effects of carotenoid supplementation on mitigating exercise-induced oxidative stress and to provide guidance for future research. METHODS: We conducted a systemati...
OBJECTIVE: This study aims to investigate the potential effects of carotenoid supplementation on mitigating exercise-induced oxidative stress and to provide guidance for future research. METHODS: We conducted a systematic review and meta-analysis using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched multiple databases from inception to August 2024 for randomized clinical trials investigating the effects of carotenoid supplementation on biomarkers of oxidative stress, inflammatory markers, antioxidant levels, and metabolic parameters in the context of exercise-induced oxidative stress. The search terms included "carotenoids," "supplementation," "exercise," "oxidative stress," "inflammation," "antioxidants," "metabolic parameters," and their synonyms. Two reviewers independently extracted study data, with disagreements resolved by a third reviewer. Quality was assessed by the Cochrane risk-of-bias method. Random and fixed effects models were used for the analysis of standard mean differences (SMD) or weighted mean differences (MDs) with 95% confidence intervals (CI). RESULTS: A total of 12 studies were included in the final analysis. Carotenoid supplementation led to significant effects in assessing oxidative stress induced by exercise (overall oxidative stress: SMD = -0.55, 95% CI [-1.04, -0.06]; malondialdehyde: MD = -0.05, 95% CI [-0.09,-0.02]; total antioxidant capacity: MD = 0.03, 95% CI [0.02, 0.03]; 8-isoprostane: MD = -35.70, 95% CI [-59.32, -12.09]; lipid peroxide: SMD = -1.07, 95% CI [-1.94, -0.20]; and nitric oxide: MD = -8.07, 95% CI [-12.54,-3.59]), inflammatory markers (inflammatory levels: SMD = 1.63, 95% CI [0.81, 2.46]; interleukin levels: SMD = 1.54, 95% CI [0.69, 2.40]; and C-reactive protein: MD = 4.56, 95% CI [0.97, 8.14]), antioxidant levels (SMD = 0.84, 95% CI [0.14, 1.53]), and metabolic parameters (energy expenditure: SMD = -0.52, 95% CI [-0.78, -0.26]; p < .05). CONCLUSION: Carotenoid supplementation appears to attenuate exercise-induced oxidative stress and the inflammatory response and improve antioxidant levels and metabolic capabilities. However, these results may be influenced by participant variability or methodological differences. Further research with larger sample sizes, longer supplementation periods, higher doses, and carotenoid bioavailability is needed to confirm these findings.
Female Athletes Report Positive Experiences as Research Participants.
Smith ES, McKay AKA, Ackerman KE … +4 more , Elliott-Sale KJ, Stellingwerff T, Harris R, Burke LM
Int J Sport Nutr Exerc Metab · 2025 Sep · PMID 40335164 · Publisher ↗
Given the underrepresentation of women in sports and exercise science research, we sought to understand the experiences of female athletes currently involved in applied sports and exercise science research to inform futu...
Given the underrepresentation of women in sports and exercise science research, we sought to understand the experiences of female athletes currently involved in applied sports and exercise science research to inform future studies and potentially increase participation rates. Accordingly, we investigated the experiences of 89 female athletes (n = 48 cyclists/triathletes, n = 19 race walkers, n = 22 National Rugby League Indigenous Women's Academy players) who participated in four separate studies of sports performance with different methodological characteristics. Participants completed a questionnaire upon study completion that queried prior research participation, reasons for participating and experiences during the current study. Across all 89 athletes, 81% were first-time research participants, with the primary barriers cited as a perceived lack of opportunities or being unaware of opportunities (93%). Participants rated an interest in the research outcome as the most important aspect influencing their decision to participate (90 ± 14 [out of 100]), followed by the opportunities to receive personalized results (84 ± 20) and education (78 ± 27). Most participants (87%) stated that they would apply the study findings to their sports involvement, while the remaining 13% reported that they required support to understand the application of results. The majority (94%) of participants indicated a willingness to participate in future studies, while the research experience was rated positively at a mean 77 out of 100. Ultimately, our findings uncovered a perceived lack of opportunity as the primary barrier to female athlete research participation. As such, opportunities for women to participate in high-quality studies should be prioritized.
Impact of Overnight Fasted State Versus Fed State on Adaptations to Resistance Training: A Randomized Clinical Trial.
Vieira AF, Blanco-Rambo E, Bandeira-Guimarães M … +8 more , Silva RT, Fergutz A, Paz IA, Munhoz SV, Colombelli R, Vaz MA, Macedo RCO, Cadore EL
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40335157 · Publisher ↗
The aim was to verify the effects of 12 weeks of resistance training (RT) performed in the fasted state compared with the fed state on body composition and physical performance in young adults. Participants were randomly...
The aim was to verify the effects of 12 weeks of resistance training (RT) performed in the fasted state compared with the fed state on body composition and physical performance in young adults. Participants were randomly assigned into fasting RT group (Fast-RT, n = 15) and fed RT group (Fed-RT, n = 13). Both groups trained two weekly resistance exercise sessions after an overnight fast or between 1 and 2 hr after consumption of a carbohydrate-rich meal, associated with isocaloric nutritional guidance. Assessments of body composition (dual-energy X-ray absorption), quadriceps muscle thickness (ultrasonography), maximum dynamic strength (one repetition maximum test), and muscle power in bench press and knee-extension exercises were performed before and after 12 weeks of intervention. Both Fast-RT and Fed-RT groups showed increases (p time ≤ .01) in quadriceps muscle thickness (1.21 and 1.18 cm, respectively; p group = .371; p Group × Time = .871), maximum dynamic strength (bench press: 10.53 and 4.89 kg, respectively; p group = .251; p Group × Time = .268; knee extension: 28.53 and 29.31 kg, respectively; p group = .919; p Group × Time = .846), and muscle power (knee extension mean power 70% one repetition maximum: 59.28 and 46.21 W, respectively; p group = .833; p Group × Time = .616; knee extension maximal power 70% one repetition maximum: 100.65 and 54.76 W, respectively; p group = .812; p Group × Time = .409). Regardless of food consumption prior to the sessions (fasted state and fed state), RT performed twice weekly across 12 weeks was associated with improvements in muscle hypertrophy and neuromuscular performance in young adults.
Caffeine Augments Sustained Hyperemia in Previously Exercised Leg in Male Competitive Long-Distance Runners.
Fujii N, Hirayama T, Matsutake R … +4 more , Ohki S, Nabekura Y, Hiroyama T, Nishiyasu T
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40274263 · Publisher ↗
Blood flow in exercised skeletal muscle remains elevated postexercise, potentially playing a critical role in recovery and adaptation process. However, effective and easily implementable interventions that augment this r...
Blood flow in exercised skeletal muscle remains elevated postexercise, potentially playing a critical role in recovery and adaptation process. However, effective and easily implementable interventions that augment this response have yet to be identified. In this study, we investigated whether caffeine intake enhances sustained postexercise hyperemia in previously active leg in competitive long-distance runners. Ten competitive male long-distance runners participated in baseline measurements, during which cardiorespiratory responses, including leg blood flow measured by ultrasound Doppler equipment, were assessed in a supine position. Subsequently, they ingested either (a) placebo capsules or (b) capsules containing 6 mg/kg caffeine in a randomized, counterbalanced, double-blind, and crossover manner. They then completed 8-min high-intensity treadmill running at 98% of the average running speed of their estimated 10,000-m best time, followed by postexercise measurements assessing the same cardiorespiratory responses. Postexercise leg blood flow was elevated from baseline, and this response was 17% higher in caffeine relative to placebo condition (between-trial difference in average with [95% CI] = 182 [2.33, 363] ml/min, p = .048, d = 1.03). Caffeine ingestion also increased minute ventilation (2.06 [0.603, 3.53] L/min, p = .011, d = 1.17), whereas it reduced end-tidal CO2 partial pressure (-2.09 [-3.68, -0.504] mmHg, p = .015, d = 1.15) postexercise relative to placebo condition. We show that preexercise 6 mg/kg caffeine intake increases postexercise leg blood flow following high-intensity running in male competitive long-distance runners. Our results stimulate future studies to assess if caffeine-induced elevations in leg blood flow accelerates recovery and/or adaptations.
Current Resting Metabolic Rate Prediction Equations Lack Sensitivity and Specificity to Indicate Relative Energy Deficiency in Sport: A Large Cohort Study in Elite Athletes.
Heikura IA, Tsai MC, Sesbreno E … +4 more , McCluskey WTP, Johnson L, Murray H, Stellingwerff T
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40262739 · Publisher ↗
OBJECTIVES: Measured resting metabolic rate (RMR) was compared to predicted RMR equations (RMRratio) to see whether a low RMRratio relates to the Relative Energy Deficiency in Sport (REDs) Clinical Assessment Tool 2 (CAT...
OBJECTIVES: Measured resting metabolic rate (RMR) was compared to predicted RMR equations (RMRratio) to see whether a low RMRratio relates to the Relative Energy Deficiency in Sport (REDs) Clinical Assessment Tool 2 (CAT2) severity/risk score. METHODS: Female (n = 127) and male (n = 53) athletes (performance Tiers 3-5) were assigned green/yellow/orange/red light according to CAT2. RMR and submaximal exercise energy expenditure (via cycle ergometer) were assessed fasted on the same morning via indirect calorimetry. Low RMR was defined as RMRratio < 0.90, with 11 RMR prediction equations tested for sensitivity, specificity, and predictive validity against the CAT2. RESULTS: RMRratio (Cunningham) was only lower in red versus green light (0.90 ± 0.07 vs. 0.99 ± 0.10; p = .023; but RMRratio was only low in 44% of red light athletes). The prevalence of low RMRratio ranged from 1% (Owen equation) to 68% (van Hooren equation) despite the overall prevalence of REDs being 46%. As a diagnostic (no REDs [green] vs. REDs [yellow + orange + red]), Cunningham equation reported sensitivity (true positives) of 0.77 at RMRratio of 1.00 and specificity (true negatives) of 1.00 at RMRratio of 0.70. Exercise energy expenditure was significantly lower in green versus orange (0.131 ± 0.013 vs. 0.142 ± 0.008 kcal·kg fat-free mass-1·min-1; p < .001) but was greater in red (0.127 ± 0.011) versus orange. CONCLUSION: Interpretation of RMRratio is radically impacted by choice of prediction equation. Although there may be some utility in cross-sectionally detecting extreme REDs cases (red light) via RMRratio, more research with a focus on sport/phenotype-specific prediction equations and varying risk thresholds is required to strengthen the validity and reliability of RMR as a part of REDs diagnostics.
Is It Required to Abstain From Fluid Consumption in the 10 Min Before Collection of a Saliva Sample?
Leal DV, Hough J
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40185478 · Publisher ↗
The noninvasive and reliable saliva collection method for stress-related endocrine biomarkers analysis has become common in field- and laboratory-based research in the last 15 years. Current guidelines recommend interrup...
The noninvasive and reliable saliva collection method for stress-related endocrine biomarkers analysis has become common in field- and laboratory-based research in the last 15 years. Current guidelines recommend interrupting water consumption 10 min before saliva sampling to avoid inaccurate, diluted concentrations of the biomarkers being examined. However, the impact of saliva dilution on salivary cortisol and testosterone levels has not been examined yet. This was a randomized, crossover experiment. Fourteen active healthy males completed three separate cycle-bout trials, where a set volume of water (250 ml) was consumed 10, 5, or 1 min before saliva sampling. Saliva was collected pre-, post-, and 30 min postexercise. No differences were observed in resting samples in any of the trials (p < .05). However, salivary cortisol increased from pre- to postexercise in the 10 (+52%, p = 0.022) and 5-min trial (+36%, p = .005) only. Salivary testosterone also increased in 10 (+34%, p = .005), 5 (+37%, p < .001), and 1-min trials (+24%, p < .035). This study proposes that consuming water up to 1 min before providing a saliva sample will not dilute the sample, allowing for an accurate determination of salivary cortisol and testosterone concentration levels. Practically, the 10-min fluid abstinence required before saliva sampling in the previous guidelines could be reduced to 1 min; however, if examining the response of salivary cortisol to an exercise trail, a fluid abstinence of 5 min may be more appropriate. This conclusion will allow for less restriction on researchers and participants alike.
No Effect of Delaying a Carbohydrate-Rich Breakfast on Afternoon High-Intensity Intermittent Exercise Performance in Trained Games Players: A Randomized, Single-Blind, Placebo-Controlled Trial.
Lamb C, Collins-Shirley F, Rees-Millns S … +5 more , Cowley A, Love TD, Waldron M, Chen YC, Metcalfe RS
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40112828 · Publisher ↗
This study tested the hypothesis that delaying consumption of a carbohydrate-rich breakfast by 2 hr would impair prolonged high-intensity intermittent exercise performance in the afternoon. Fifteen intermittent games pla...
This study tested the hypothesis that delaying consumption of a carbohydrate-rich breakfast by 2 hr would impair prolonged high-intensity intermittent exercise performance in the afternoon. Fifteen intermittent games players (mean ± SD: age: 24 ± 6 years; V˙O2peak: 46 ± 6 ml·kg-1·min-1) completed a randomized, single-blind, placebo-controlled crossover study with two trials (EARLY and DELAY) matched for dietary intake. In EARLY, participants consumed a high-carbohydrate (semisolid) breakfast shake (2 g/kg BM maltodextrin, 1 ml/kg BM orange squash, 0.15 g/kg BM xanthan gum, 0.067 g/kg BM artificial sweetener, and 6 ml/kg BM water) at 8 a.m., followed by a taste and texture matched, but energy depleted, placebo shake 2 hr later. In DELAY, the order of these shakes was reversed. Three hours following a high-carbohydrate lunch (888 ± 107 Kcal, 145 ± 28 g carbohydrate), participants completed a 90-min intermittent cycling test, consisting of two 40-min halves, with 10 min of rest in between. Each half involved 18 repeated 2-min blocks of steady-state cycling (100 s; 35% Wmax), followed by 15 s of unloaded pedaling and a 6-s all-out sprint. There were no differences in peak power (first half: mean difference [95% confidence interval]: 6.6 [-10.9, 24.1] W, d = 0.03 and second half: 8.5 [-6.5, 23.6] W, d = 0.04) or mean power (first half: mean difference: 6.4 [-10.7, 23.5] W, d = 0.03 and second half: mean difference: 7.3 [-6.5, 21.3] W, d = 0.04) during the sprints between the DELAY and EARLY conditions. In contrast with our hypothesis, these data provide no evidence that delaying consumption of a carbohydrate-rich breakfast by 2 hr impairs prolonged high-intensity intermittent exercise performance in the afternoon.
Case Series: Management of Exercise-Associated Gastrointestinal Symptoms in Endurance Athletes Using a High-Carbohydrate Low-FODMAP Therapeutic Intervention.
Scrivin R, Slater G, Costa RJS
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40049175 · Publisher ↗
This case-series describes a four-phase management approach implementing gastrointestinal assessment during exercise (GastroAxEx) to develop therapeutic interventions for athletes affected by exercise-associated gastroin...
This case-series describes a four-phase management approach implementing gastrointestinal assessment during exercise (GastroAxEx) to develop therapeutic interventions for athletes affected by exercise-associated gastrointestinal symptoms (Ex-GIS). Recreational to elite-level athletes who experienced recurrent severe Ex-GIS (n = 9) and controls (n = 2) (without Ex-GIS) volunteered to participate in the case series. The four-phased approach involved a clinical assessment (Phase 1), a standardized laboratory GastroAxEx where physiological strain and GIS data were collected (Phase 2), individualized therapeutic intervention and management strategies based on Phase 2 outcomes that specifically included implementation of a 48-hr high carbohydrate low FODMAP diet (Phase 3), and the monitoring and adjustment of therapeutic interventions (Phase 4). The majority of athletes (n = 6/9) consumed <400 ml/hr of fluid ad libitum, resulting in 2%-4% body mass loss, and <40 g/hr of exogenous carbohydrate (n = 8/9), during the GastroAxEx. Severe Ex-GIS (predominantly loose stools) was reported by n = 4/9 athletes, whereas n = 8/9 athletes reported severe Ex-GIS (predominantly loose stools) in the recovery period. All athletes reported low food and fluid intake tolerance during exercise and recovery. Orocecal transit time was slow or delayed for n = 2/9 athletes. Most athletes (n = 8/9) successfully implemented a 48-hr high carbohydrate low FODMAP prior to and improved intake tolerance during the targeted event. In addition, the incidence and severity of Ex-GIS were reduced, resulting in improved perceived work output during the targeted events. A 48-hr high carbohydrate low FODMAP before endurance exercise appears to be a valuable addition to suggested therapeutic interventions used to mitigate Ex-GIS.
Female Exercise Metabolism: Quality Assessment of Existing Knowledge Base and Key Challenges in Study Design.
Bagot S, Miles-Chan J, Hackney AC … +2 more , Duclos M, Isacco L
Int J Sport Nutr Exerc Metab · 2025 May · PMID 40043719 · Publisher ↗
A better understanding of the practical and methodological challenges inherent in accurately tracking female hormonal status would enhance the clarity of research findings in exercise metabolism. The purpose of this stud...
A better understanding of the practical and methodological challenges inherent in accurately tracking female hormonal status would enhance the clarity of research findings in exercise metabolism. The purpose of this study was to conduct an objective assessment of the quality of existing literature in this area and to provide a general overview of the practical conditions and issues encountered in studies investigating substrate metabolism during exercise in women, both in those using (HC+) or not using (HC-) hormonal contraceptives. Forty-four articles were identified through systematic reviews, meta-analyses, and searches on PubMed/MEDLINE. A quality assessment framework was developed and applied using a double-blind scoring approach. The loss/exclusion of data between baseline and final analyses per study was quantified, and the main challenges were highlighted. A higher mean global score was observed in studies conducted among HC+ women (81%) than those among HC- women (46%). Although the dropout rates were rarely mentioned in HC+ women articles, the mean rate of participant/data loss in HC- groups was 22.1%. The rate of HC- participant loss was positively correlated with the global score (r = .504, p = .02). High-quality research may be easier to achieve in studies involving HC+ women compared with those involving HC- women. Studies on HC- women seem to face more practical challenges, such as tracking the menstrual cycle and targeting specific (sub)phases of the menstrual cycle, along with technical and feasibility limitations. Thus, although the framework for designing such studies exists, the quality assessment of the available literature emphasizes its challenge in terms of research implementation.
The Effects of Prebiotic Supplementation on Markers of Exercise-Induced Gastrointestinal Syndrome in Response to Exertional Heat Stress.
Rauch CE, Henningsen K, Martinez I … +7 more , Young P, Mika A, Huschtscha Z, McCubbin A, Henry R, Anderson D, Costa RJS
Int J Sport Nutr Exerc Metab · 2025 Jul · PMID 40010361 · Publisher ↗
Exercise perturbs various aspects of gastrointestinal integrity and function, which may lead to performance impeding gastrointestinal symptoms (GIS) and/or precipitate clinical issues warranting medical management. This...
Exercise perturbs various aspects of gastrointestinal integrity and function, which may lead to performance impeding gastrointestinal symptoms (GIS) and/or precipitate clinical issues warranting medical management. This study aimed to determine the impact of prebiotic supplementation on gastrointestinal integrity and functional status in response to exertional heat stress (EHS). Sixteen endurance athletes completed two trials of 3-hr running at 60% V˙O2max in 30 °C at baseline (T1) and following an 8-week supplementation period (T2), with 16 g/day prebiotic (PREBIOTIC) or matched placebo (PLACEBO). Blood samples were collected pre-EHS and post-EHS and in recovery for determination of stress response (cortisol), intestinal epithelial injury (intestinal fatty acid binding protein), bacterial endotoxemia (sCD14), and systemic inflammation (C-reactive protein). GIS and feeding tolerance variables were assessed throughout the EHS. Orocecal transit time was determined via a lactulose challenge given at 2.5 hr into EHS. Plasma cortisol (combined mean: +252 ng/ml), intestinal fatty acid binding protein (+800 pg/ml), and sCD14 (+487 ng/ml) concentrations increased in response to EHS in T1 (p ≤ .05), but not for C-reactive protein (+0.8 μg/ml; p > .05), in both PREBIOTIC and PLACEBO. PREBIOTIC supplementation resulted in a blunted intestinal fatty acid binding protein response on T2 (+316 pg/ml) compared with an increase (+1,001 ng/ml) in PLACEBO (p = .005). Lower sCD14 was observed at T2 (2,799 ng/ml) versus T1 (3,246 ng/ml) in PREBIOTIC only (p = .039). No intervention effects were observed for C-reactive protein. No difference within or between PREBIOTIC and PLACEBO at T1 and T2 was observed for orocecal transit time, GIS, and feeding tolerance. In conclusion, 8 weeks of prebiotic supplementation modestly attenuates EHS associated perturbations to intestinal integrity, but does not further impair gastrointestinal transit and/or exacerbate EHS associated GIS or feeding tolerance.
Minimal Influence of Formulated Nutritional Interventions on Sleep and Next-Morning Physical Performance, Cognitive Function, and Postural Sway in Adult Males: A Randomized, Placebo-Controlled, Crossover Study.
Morrison M, Weakley J, Roach GD … +7 more , Sargent C, Miller DJ, Nyman L, Gardiner C, Munteanu G, Pahnke MD, Halson SL
Int J Sport Nutr Exerc Metab · 2025 May · PMID 39983739 · Publisher ↗
Athletes often experience poor sleep quality and quantity which may hinder physical performance and cognitive function. Presleep nutritional strategies may be an alternative to pharmacological interventions to improve sl...
Athletes often experience poor sleep quality and quantity which may hinder physical performance and cognitive function. Presleep nutritional strategies may be an alternative to pharmacological interventions to improve sleep. The aim of this study was to examine the effect of two different doses of a nutritional intervention (both containing high Glycemic Index carbohydrate, whey, tryptophan, theanine, and 5'AMP) versus placebo on objective and subjective sleep, next-morning physical performance, cognitive function, and postural sway. Seventeen healthy, trained adult males completed three double-blind trials in a randomized, counterbalanced, crossover design. Participants were allocated to conditions using a Latin Square design. A (a) low-dose, (b) high-dose, or (c) placebo drink was provided 90 min before sleep each night. Polysomnography was used to measure objective sleep parameters. Cognitive function, postural sway, and subjective sleep quality were assessed 30 min after waking. Physical performance was assessed using a 10-min maximal effort cycling time trial each morning. All data were analyzed using linear mixed effects models and effect sizes were calculated using Cohen's d. This study was registered prospectively as a clinical trial with Australian New Zealand Clinical Trials Registry (registration number: NCT05032729). No significant main effects or improvements were observed in objective or subjective sleep parameters, physical performance, cognitive function, or postural sway. The low-dose intervention appeared to reduce N3 sleep duration compared with placebo (-13.6 min). The high-dose intervention appeared to increase N1 sleep duration compared with placebo (+7.4 min). However, the magnitude of changes observed were not likely to cause meaningful reductions in sleep quality and quantity.
Caffeinated Ice Slushy Enhances 1,200 kJ Cycle Time-Trial Performance in the Heat.
Landers GJ, Ward S, Zimmermann M
Int J Sport Nutr Exerc Metab · 2025 May · PMID 39947192 · Publisher ↗
This study aimed to assess the effects of caffeine ingestion incorporated into an ice slushy on cycling time-trial (CTT) performance in hot, humid conditions. Nine moderately trained recreational male cyclists or triathl...
This study aimed to assess the effects of caffeine ingestion incorporated into an ice slushy on cycling time-trial (CTT) performance in hot, humid conditions. Nine moderately trained recreational male cyclists or triathletes ingested 6.8 g/kg crushed ice with either 6% carbohydrate concentration only (CON) or 6% carbohydrate concentration and 3 mg/kg caffeine (CAF) consumed over a 30 min period prior to exercise in a single-blind, counterbalanced design. Postingestion, participants completed a CTT equating 1,200 kJ of work (∼40 km) in a climate-controlled chamber (33 °C and 60% relative humidity). Experimental sessions were separated by 7 days. During each CTT, rectal temperature, cycling time, heart rate, blood lactate, and ratings of perceived exertion and thermal sensation were measured at set intervals of work. The 1,200 kJ CTT was completed faster in CAF (4,716 ± 785 s) compared with CON (4,911 ±755 s) (p < .05); and split times were completed faster in CAF compared with CON from the 800 to 1,200 kJ timepoints of the CTT. Precooling lowered rectal temperature similarly in both CAF (-0.6 ± 0.2 °C) and CON (-0.6 ± 0.1 °C) (p > .05). No differences were observed between CAF and CON for heart rate, rating of perceived exertion, rating of perceived thermal sensation, or blood lactate across the measured time points (p > .05). Precooling with the combination of a carbohydrate-based ice slushy and caffeine resulted in improved CTT performance in hot conditions compared with a carbohydrate-based ice slushy alone. Therefore, the addition of caffeine to ice slushies might be considered by endurance athletes competing in the heat for enhanced performance gains.
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