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Significant Changes in Resting Metabolic Rate Over a Competitive Match Week Are Accompanied by an Absence of Nutritional Periodization in Male Professional Soccer Players

Jennie L. Carter, David J. Lee, Craig G. Perrin, Mayur K. Ranchordas, and Matthew Cole

Resting metabolic rate (RMR) is an important component of total daily energy expenditure; however, it is currently not understood how it varies across a typical competitive match week in professional soccer players. For the first time, we aimed to assess RMR throughout an in-season competitive week in professional soccer players. Additionally, we aimed to assess energy and carbohydrate intake across the same week. Twenty-four professional soccer players from an English Premier League club (age: 18 ± 1.6 years) completed the study. RMR was assessed each morning of a typical competitive match week (match day [MD] −3, −2, −1, +1, +2, and + 3), and dietary intake (including MD) was assessed daily via the remote food photography method and 24-hr recall. Daily training load was quantified using Global Positioning System, daily muscle soreness ratings were recorded, and body composition was assessed via dual-energy X-ray absorptiometry. There was a significant (p = .0004) increase in mean RMR of ∼261 kcal/day on MD + 1, compared with MD − 1. Additionally, volume of oxygen consumed significantly increased at MD + 1 (p = .0002) versus MD − 1. There were no significant differences in daily energy or carbohydrate intake across the competitive week (p > .05), with inadequate carbohydrate intakes on MD − 1 (∼3.9 g/kg body mass), MD (∼4.2 g/kg body mass), and MD + 1 (∼3.6 g/kg body mass) in relation to current recommendations. We report, for the first time, that RMR is significantly increased following a competitive match in professional soccer players. In addition, we confirm previous findings to reinforce that players exhibit inadequate nutrition periodization practices, which may impair physical performance and recovery.

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Total Energy Expenditure and Nutritional Intake in Continuous Multiday Ultramarathon Events

Andrew W. Best, Amanda McGrosky, Zane Swanson, Rebecca Rimbach, Katie McConaughy, Joe McConaughy, Cara Ocobock, and Herman Pontzer

Continuous multiday ultramarathon competitions are increasingly popular and impose extreme energetic and nutritional demands on competitors. However, few data have been published on energy expenditure during these events. Here, we report doubly labeled water-derived measures of total energy expenditure (in kilocalories per day) and estimated physical activity level (PAL: total energy expenditure/basal metabolic rate) collected from five elite and subelite finishers (four males and one female, age 34.6 ± 4.9 years)—and nutritional intake data from the winner—of the Cocodona 250, a ∼402-km race in Arizona, and from a fastest-known-time record (one male, age 30 years) on the ∼1,315-km Arizona Trail. PAL during these events exceeded four times basal metabolic rate (Cocodona range: 4.34–6.94; Arizona Trail: 5.63). Combining the results with other doubly labeled water-derived total energy expenditure data from ultraendurance events show a strong inverse relationship between event duration and PAL (r 2 = .68, p < .0001). Cocodona race duration was inversely, though not significantly, associated with PAL (r 2 = .70, p = .08). Water turnover varied widely between athletes and was not explained by PAL or body mass. The Cocodona race winner met ∼53% of energy demand via dietary intake, 85.6% of which was carbohydrate, while ∼47% of energy demand was met via catabolism of body energy stores. Together, these results illustrate the energetic deficits incurred during competitive continuous multiday ultramarathon efforts and implicate macronutrient absorption and/or storage as key factors in ultramarathon performance.

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Volume 33 (2023): Issue 5 (Sep 2023)

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The Effects of an Acute Dose of New Zealand Blackcurrant Extract on 5-km Running Performance

Samantha L. Moss, Edward Brindley, Kevin Enright, Jamie Highton, and Richard Bott

This study investigated the effects of an acute dose (900 mg) of New Zealand Blackcurrant (NZBC) extract on 5-km running performance, alongside associated physiological and metabolic responses. Sixteen trained male runners (age 26 ± 5 years, stature 173.4 ± 7.3 cm, body mass 73.7 ± 6.9 kg, maximal oxygen consumption [ V ˙ O 2 max ] 55.4 ± 6.1 ml·kg−1·min−1) ingested either capsules containing NZBC extract (3 × 300 mg CurraNZ, 315 mg anthocyanins) or a matched placebo (3 × 300 mg gluten-free flour) 2 hr before exercise in a double-blind, randomized, crossover design. Performance time, physiological, and metabolic responses were assessed in a 5-km time trial, preceded by 10-min exercise at the lactate threshold on a treadmill. NZBC extract did not alter the physiological or metabolic responses to exercise at the lactate threshold (oxygen uptake, respiratory exchange ratio, minute ventilation, carbohydrate oxidation, fat oxidation, heart rate, blood lactate, or rating of perceived exertion, p > .05). The 5-km time trial was completed in a faster time in the NZBC extract condition compared with placebo (NZBC: 1,308.96 ± 122.36 s, placebo: 1,346.33 ± 124.44, p = .001, d = −0.23, confidence interval range = [−0.46, 0.00 s]). No differences in physiological or metabolic responses were apparent between conditions for the 5-km time trial (p > .05). Ingesting 900 mg of NZBC extract as an acute dose improves performance in trained male runners without altering physiological or metabolic responses to exercise. Further research is needed to assess a wider range of possible mechanisms (e.g., cardiovascular function, metabolite profiles) to advance insight into improved performance following supplementation.

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Mouth Rinsing and Ingestion of Unpleasant Salty or Bitter Solutions Does Not Improve Cycling Sprint Performance in Trained Cyclists

Edward A. Gray, Rocco Cavaleri, and Jason C. Siegler

The purpose of this study was to investigate the influence of mouth rinsing and ingesting unpleasant salty or bitter solutions on cycling sprint performance and knee extensor force characteristics. Eleven male and one female trained cyclists (age: 34 ± 9 years, maximal oxygen uptake 56.9 ± 3.9 ml·kg−1·min−1) completed a ramp test and familiarization followed by four experimental trials. In each trial, participants completed an all-out 30-s cycling sprint with knee extensor maximal voluntary contractions before and immediately after the sprint. In a randomized, counterbalanced, cross-over order, the four main trials were: a no solution control condition, water, salty (5.8%), or bitter (2 mM quinine) solutions that were mouth rinsed (10 s) and ingested immediately before the cycling sprint. There were no significant differences between conditions in mean power (mean ± SD, no solution: 822 ± 115 W, water: 818 ± 108 W, salt: 832 ± 111 W, bitter: 818 ± 105 W); peak power (no solution: 1,184 ± 205 W, water: 1,177 ± 207 W, salt: 1,195 ± 210 W, bitter: 1,184 ± 209 W); or fatigue index (no solution: 51.5% ± 5.7%, water: 50.8% ± 7.0%, salt: 51.1% ± 5.9%, bitter: 51.2% ± 7.1%) during the sprint. Maximal force and impulse declined postexercise; however, there were no significant differences between conditions in knee extensor force characteristics. The present data do not support the use of unpleasant salty or bitter solutions as an ergogenic aid to improve sprint exercise performance.

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The Impact of a Short-Term Ketogenic Low-Carbohydrate High-Fat Diet on Biomarkers of Intestinal Epithelial Integrity and Gastrointestinal Symptoms

Alannah K.A. McKay, Alice M. Wallett, Andrew J. McKune, Julien D. Périard, Philo Saunders, Jamie Whitfield, Nicolin Tee, Ida A. Heikura, Megan L.R. Ross, Avish P. Sharma, Ricardo J.S. Costa, and Louise M. Burke

Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk. Twenty-eight male race walkers adhered to a high carbohydrate (CHO)/energy diet (65% CHO, energy availability = 40 kcal·kg FFM−1·day−1) for 6 days prior to a Baseline 25-km race walk. Athletes were then split into three subgroups: high CHO/energy diet (n = 10); low-CHO, high-fat diet (LCHF: n = 8; <50 g/day CHO, energy availability = 40 kcal·kg FFM−1·day−1); and low energy availability (n = 10; 65% CHO, energy availability = 15 kcal·kg FFM−1·day−1) for a further 6-day dietary intervention period prior to a second 25-km race walk (Adaptation). During both trials, venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for markers of intestinal epithelial disruption. Intestinal fatty acid-binding protein concentration was significantly higher (twofold increase) in response to exercise during Adaptation compared to Baseline in the LCHF group (p = .001). Similar findings were observed for soluble CD14 (p < .001) and lipopolysaccharide-binding protein (p = .003), where postexercise concentrations were higher (53% and 36%, respectively) during Adaptation than Baseline in LCHF. No differences in high CHO/energy diet or low energy availability were apparent for any blood markers assessed (p > .05). A short-term LCHF diet increased intestinal epithelial cell injury in response to a 25-km race walk. No effect of low energy availability on gastrointestinal injury or symptoms was observed.

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Ergogenic Effects of Very Low to Moderate Doses of Caffeine on Vertical Jump Performance

Teppei Matsumura, Yuki Takamura, Kazushi Fukuzawa, Kazuya Nakagawa, Shunya Nonoyama, Keigo Tomoo, Hayato Tsukamoto, Yasushi Shinohara, Motoyuki Iemitsu, Akinori Nagano, Tadao Isaka, and Takeshi Hashimoto

Although the ergogenic effects of 3–6 mg/kg caffeine are widely accepted, the efficacy of low doses of caffeine has been discussed. However, it is unclear whether the ergogenic effects of caffeine on jump performance are dose responsive in a wide range of doses. This study aimed to examine the effect of very low (1 mg/kg) to moderate doses of caffeine, including commonly utilized ergogenic doses (i.e., 3 and 6 mg/kg), on vertical jump performance. A total of 32 well-trained collegiate sprinters and jumpers performed countermovement jumps and squat jumps three times each in a double-blind, counterbalanced, randomized, crossover design. Participants ingested a placebo or 1, 3, or 6 mg/kg caffeine 60 min before jumping. Compared with the placebo, 6 mg/kg caffeine significantly enhanced countermovement jump (p < .001) and squat jump (p = .012) heights; furthermore, 1 and 3 mg/kg of caffeine also significantly increased countermovement jump height (1 mg/kg: p = .002, 3 mg/kg: p < .001) but not squat jump height (1 mg/kg: p = .436, 3 mg/kg: p = .054). There were no significant differences among all caffeine doses in both jumps (all p > .05). In conclusion, even at a dose as low as 1 mg/kg, caffeine improved vertical jump performance in a dose-independent manner. This study provides new insight into the applicability and feasibility of 1 mg/kg caffeine as a safe and effective ergogenic strategy for jump performance.

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Erratum. Ergogenic Effects of Very Low to Moderate Doses of Caffeine on Vertical Jump Performance

International Journal of Sport Nutrition and Exercise Metabolism

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Stop, Collaborate, and Listen

James A. Betts

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Erratum. The Postprandial Plasma Amino Acid Response Does Not Differ Following the Ingestion of a Solid Versus a Liquid Milk Protein Product in Healthy Adult Females

International Journal of Sport Nutrition and Exercise Metabolism