Purpose Preexercise ingestion of exogenous ketones alters the metabolic response to exercise, but effects on exercise performance have been equivocal. Methods On two occasions in a double-blind, randomized crossover design, eight endurance-trained runners performed 1 h of submaximal exercise at approximately 65% V˙O2max immediately followed by a 10-km self-paced time trial (TT) on a motorized treadmill. An 8% carbohydrate-electrolyte solution was consumed before and during exercise, either alone (CHO + PLA), or with 573 mg·kg−1 of a ketone monoester supplement (CHO + KME). Expired air, HR, and RPE were monitored during submaximal exercise. Serial venous blood samples were assayed for plasma glucose, lactate, and β-hydroxybutyrate concentrations. Results CHO + KME produced plasma β-hydroxybutyrate concentrations of approximately 1.0 to 1.3 mM during exercise (P < 0.001), but plasma glucose and lactate concentrations were similar during exercise in both trials. V˙O2, running economy, respiratory exchange ratio, HR, and RPE were also similar between trials. Performance in the 10-km TT was not different (P = 0.483) between CHO + KME (mean, 2402 s; 95% confidence interval, 2204–2600 s) and CHO + PLA (mean, 2422 s; 95% confidence interval, 2217–2628 s). Cognitive performance, measured by reaction time and a multitasking test, did not differ between trials. Conclusions Compared with carbohydrate alone, coingestion of KME by endurance-trained athletes elevated plasma β-hydroxybutyrate concentrations, but did not improve 10-km running TT or cognitive performance.

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Purpose Eight weeks of time-restricted eating (TRE) in concert with habitual exercise training was investigated for effects on body composition, energy and macronutrient intakes, indices of endurance running performance, and markers of metabolic health in endurance athletes. Methods Male middle- and long-distance runners (n = 23) were randomly assigned to TRE (n = 12) or habitual dietary intake (CON; n = 11). TRE required participants to consume all of their dietary intake within an 8-h eating window (so-called 16:8 TRE), but dietary patterns, food choices, and energy intake were ad libitum during this window. Participants continued their habitual training during the intervention period. Participants completed an incremental exercise test before (PRE) and after (POST) the 8-wk intervention for the assessment of blood lactate concentrations, running economy, and maximal oxygen uptake. Fasted blood samples were analyzed for glucose, insulin, and triglyceride concentrations. Dietary intake was assessed at PRE, MID (week 4), and POST using a 4-d semiweighed food diary. Results Seventeen participants (TRE, n = 10; CON, n = 7) completed the intervention. Training load did not differ between groups for the duration of the intervention period. TRE resulted in a reduction in body mass (mean difference of −1.92 kg, 95% confidence interval = −3.52 to −0.32, P = 0.022). Self-reported daily energy intake was lower in TRE at MID and POST (group–time interaction, P = 0.049). No effect of TRE was observed for oxygen consumption, respiratory exchange ratio, running economy, blood lactate concentrations, or heart rate during exercise, nor were there any effects on glucose, insulin, or triglyceride concentrations observed. Conclusion Eight weeks of 16:8 TRE in middle- and long-distance runners resulted in a decrease in body mass commensurate with a reduction in daily energy intake, but it did not alter indices of endurance running performance or metabolic health.

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The purpose of this study was to generate movement category velocity thresholds for elite Gaelic football (GF) and hurling referees using a two-stage unsupervised clustering technique.Activity data from 41 GF and 38 hurling referees was collected using global positioning system technology during 338 and 221 competitive games, respectively. The elbow method was used in stage one to identify the number of movement categories in the datasets. In stage two, the respective velocity thresholds for each category were identified using spectral clustering. The efficacy of these thresholds was examined using a regression analysis performed between the median of each of the velocity thresholds and the raw velocity data. Five velocity thresholds were identified for both GF and hurling referees (mean ± standard deviation: GF referees;

There is a paucity of studies describing the physical match demands of elite international women’s rugby union, which limits coaches’ ability to effectively prepare players for the physical demands required to compete at the elite level. Global positioning system technologies were used to measure the physical match demands of 53 international female rugby union players during three consecutive Women’s Six Nations Championships (2020–2022), resulting in 260 individual match performances. Mixed-linear modelling was used to investigate differences in physical match demands between positions. Significant effects (p < 0.05) of the position were observed for all variables, with the exception of relative distances (m.min−1) at velocities of 1.01–3.00 m·s−1 (p = 0.094) and 3.01–5.00 m·s−1 (p = 0.216). This study provides valuable data on the physical match demands of elite international women’s rugby union match play that may aid practitioners in the physical preparation of players to compete at this level. Training methodologies for elite-level female rugby union players should consider the unique demands across positional groups with specific considerations of high-velocity running and collision frequency.

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Purpose Acute ingestion of a ketone monoester, with and without co-ingestion of carbohydrate, was investigated for effects on running economy (RE), time to exhaustion (TTE), and other related indices of endurance running performance. Methods Using a three condition, placebo-controlled, randomized crossover design, eleven male middle- and long- distance runners ran at five submaximal speeds (10 to 14 km.h-1) on a motorized treadmill for 8 min each, immediately followed by a ramp test to volitional exhaustion. Participants consumed either a 10% carbohydrate solution (CHO), a 10% carbohydrate solution with 750 mg.kg-1 body mass of a (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester (CHO + KE), or 750 mg.kg-1 body mass of the ketone monoester in flavored water (KE) before (2/3 of the dose) and during (1/3 of the dose) exercise. Results βHB concentration averaged 1.8 ± 0.3 mM and 2.1 ± 0.3 mM during exercise in CHO + KE and KE, respectively. RE was lower at each submaximal running speed (ES = 0.48 to 0.98) by an average of 4.1% in KE compared to CHO, but not between CHO + KE and CHO. TTE did not differ between CHO (369 ± 116 s), CHO + KE (342 ± 99 s), or KE (333 ± 106 s) (P = 0.093). Conclusions Acute ingestion of a ketone monoester without carbohydrate, but not when co-ingested with carbohydrate, improved RE in middle- and long- distance runners at a range of submaximal running speeds, and did not alter TTE in a short duration ramp test to volitional exhaustion. Further investigation is required to examine if these differences translate into positive performance outcomes over longer durations of exercise.