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Alannah K.A. McKay, Peter Peeling, David B. Pyne, Nicolin Tee, Marijke Welveart, Ida A. Heikura, Avish P. Sharma, Jamie Whitfield, Megan L. Ross, Rachel P.L. van Swelm, Coby M. Laarakkers, and Louise M. Burke

This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17–23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p = .004) and hotter trial ambient temperatures (p = .014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise.

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Mohamed Nashrudin Naharudin, Ashril Yusof, David J. Clayton, and Lewis J. James

Background: Preexercise food intake enhances exercise performance due, in part, to the provision of exogenous carbohydrate. Food intake also suppresses hunger, but the specific influence of hunger on exercise performance has not been investigated. This study aimed to manipulate hunger by altering preexercise meal viscosity to examine whether hunger influences performance. Methods: Sixteen resistance-trained males completed 2 experimental trials ingesting either high viscosity semisolid (SEM) and low viscosity liquid (LIQ) carbohydrate-containing meals 2 hours before performing 4 sets of back squat (85 [22] kg) and bench press (68 [13] kg) to failure at 90% 10-repetition maximum. Subjective hunger/fullness as well as plasma concentrations of glucose, insulin, ghrelin, and peptide tyrosine–tyrosine were measured before and periodically after the meal. Repetitions completed in sets were used to determine exercise performance. Results: Hunger was lower, and fullness was greater during SEM compared with LIQ immediately before and during exercise (P < .05). Total repetitions completed for back squat were approximately 10% greater in SEM (SEM 57 [9]; LIQ 51 [7] repetitions; P = .001) with no difference in bench press repetitions (SEM 48 [11]; LIQ 48 [10] repetitions; P = .621). Postprandial glucose concentrations were greater during LIQ (12% increase in peak glucose) but were similar throughout exercise. Conclusion: This study demonstrates that exercise performance in back squat was increased in the SEM trial concomitant to a reduction in hunger. Therefore, this study provides novel data that suggest that exercise performance might be influenced by hunger, at least for resistance exercise.

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Marcel Lemire, Romain Remetter, Thomas J. Hureau, Bernard Geny, Evelyne Lonsdorfer, Fabrice Favret, and Stéphane P. Dufour

Purpose: This study aimed to determine the contribution of metabolic, cardiopulmonary, neuromuscular, and biomechanical factors to the energy cost (ECR) of graded running in well-trained runners. Methods: Eight men who were well-trained trail runners (age: 29 [10] y, mean [SD]; maximum oxygen consumption: 68.0 [6.4] mL·min−1·kg−1) completed maximal isometric evaluations of lower limb extensor muscles and 3 randomized trials on a treadmill to determine their metabolic and cardiovascular responses and running gait kinematics during downhill (DR: −15% slope), level (0%), and uphill running (UR: 15%) performed at similar O2 uptake (approximately 60% maximum oxygen consumption). Results: Despite similar O2 demand, ECR was lower in DR versus level running versus UR (2.5 [0.2] vs 3.6 [0.2] vs 7.9 [0.5] J·kg−1·m−1, respectively; all P < .001). Energy cost of running was correlated between DR and level running conditions only (r 2 = .63; P = .018). Importantly, while ECR was correlated with heart rate, cardiac output, and arteriovenous O2 difference in UR (all r 2 > .50; P < .05), ECR was correlated with lower limb vertical stiffness, ground contact time, stride length, and step frequency in DR (all r 2 > .58; P < .05). Lower limb isometric extension torques were not related to ECR whatever the slope. Conclusion: The determining physiological factors of ECR might be slope specific, mainly metabolic and cardiovascular in UR versus mainly neuromuscular and mechanical in DR. This possible slope specificity of ECR during incline running opens the way for the implementation of differentiated physiological evaluations and training strategies to optimize performance in well-trained trail runners.

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Francisco J. Llorente-Cantarero, Francisco J. Aguilar-Gómez, Gloria Bueno-Lozano, Augusto Anguita-Ruiz, Azahara I. Rupérez, Rocío Vázquez-Cobela, Katherine Flores-Rojas, Concepción M. Aguilera, Luis A. Moreno, Ángel Gil, Rosaura Leis, and Mercedes Gil-Campos

Childhood obesity has been related to metabolic syndrome and low-grade chronic inflammation. This study aimed to evaluate the impact of physical activity intensities and practice on inflammation, endothelial damage, and cardiometabolic risk factors in children. There were 513 participants, aged 6–14 years, recruited for the study. Physical activity was measured by accelerometry, and the children were classified into four groups according to quartiles of moderate to vigorous physical activity (MVPA) practice as very low active, low active, moderate active, and high active. Anthropometric measures, blood pressure, and plasma metabolic and proinflammatory parameters were analyzed. Very low active group presented a worse lipid profile and higher insulin, leptin, adiponectin, resistin, matrix metallopeptidase-9, and tissue plasminogen activator inhibitor-1, while lower levels of tumor necrosis factor-alpha, Type 1 macrophages, and interleukin 8 than high-active children. Regression analyses showed that a higher MVPA practice was associated with lower levels of triacylglycerols (β: −0.118; p = .008), resistin (β: −0.151; p = .005), tPAI (β: −0.105; p = .046), and P-selectin (β: −0.160; p = .006), independently of sex, age, and body mass index (BMI). In contrast, a higher BMI was associated with higher levels of insulin (β: 0.370; p < .001), Homeostasis Model Assessment (β: 0.352; p < .001), triacylglycerols (β: 0.209; p < .001), leptin (β: 0.654; p < .001), tumor necrosis factor-alpha (β: 0.182; p < .001), Type 1macrophages (β: 0.181; p < .001), and tissue plasminogen activator inhibitor (β: 0.240; p < .001), independently of sex, age, and MVPA. A better anthropometric, metabolic, and inflammatory profile was detected in the most active children; however, these differences were partly due to BMI. These results suggest that a higher MVPA practice and a lower BMI in children may lead to a better cardiometabolic status.

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Kellyanne J. Redman, Logan Wade, Vincent G. Kelly, Mark J. Connick, and Emma M. Beckman

Purpose: Tackling is a fundamental skill in collision sports such as rugby league. Given the complexity of tackling and multitude of strength and power variables available for analysis, this study aimed to predict tackle outcomes in professional rugby league based on strength and power principal components (PCs). Methods: Twenty-eight rugby league players participated in this study. Maximal strength was assessed via 1 repetition maximum on the back squat, bench press, and bench pull. Lower-body vertical and horizontal power were evaluated using a countermovement jump and standing broad jump. A postmatch analysis of 5 National Rugby League matches was conducted to examine tackling outcomes. PC analysis was performed on the strength and power assessments. The first PCs were retained in each analysis, and a series of Spearman rank-order correlations were conducted between the tackle outcomes and the retained PCs. The PCs significantly related to tackle outcomes were included in the multiple regression analyses to estimate their effect on tackle outcomes. Results: Strength PC was a significant predictor of play-the-ball speed in attack, accounting for 54% of the variance. Countermovement jump PC was a significant predictor of postcontact meters, explaining 19% of the variance. Conclusions: These findings demonstrate that a range of tackle outcomes may be predicted from strength and power components. The coaching staff may choose to develop programs and testing designed to focus on these components, which may further develop players’ tackle outcomes during competition.

Open access

James A. Betts

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Wolf-Stephan Rudi, Florian Maier, Dominik Schüttler, Antonia Kellnar, Anna Katharina Strüven, Wolfgang Hamm, and Stefan Brunner

Background: Although many countries have introduced strict guidelines regarding mouth and nose coverage in public to contain infection rates during the SARS-CoV-2 pandemic, more information is needed regarding the impact of wearing face masks on lactate thresholds (LT) and performance parameters during exercise. Methods: Ten healthy male and 10 healthy female subjects (age = 33.4 [10.26] y, body mass index = 23.52 [2.36] kg/m2) performed 3 incremental performance tests, wearing no mask (NM), surgical mask (SM), and filtering face piece mask class 2 (FFP2), with a cycle ergometer. The authors analyzed changes in the LT, in blood gas parameters, and in the rating of perceived exertion (RPE). Results: Performance at LT remained unchanged in subjects wearing SM or FFP2 in comparison with NM (162.5 [50.6] vs 167.2 [58.9] vs 162.2 [58.4] W with NM, SM, and FFP2, respectively, P = .24). However, the peak performance was significantly reduced wearing FFP2 compared with NM (213.8 [71.3] vs 230.5 [77.27] W, FFP2 vs NM, respectively, P < .001). Capillary pCO2 was increased while wearing SM as well as FFP2 compared with NM (29 [3.1] vs 33.3 [4] vs 35.8 [4.9] mmHg with NM, SM, and FFP2, respectively; P < .001), and pO2 decreased under maximum performance (84 [6.7] vs 79.1 [7.5] vs 77.3 [8.2] mmHg with NM, SM, and FFP2, P < .01). Importantly, rating of perceived exertion was significantly increased by wearing FFP2 compared with NM at LT according to Mader (16.7 [2.7] vs 15.3 [1.8] FFP2 vs NM, respectively, P < .01). Conclusion: Wearing face masks during exercise showed no effect on LT, limited maximum performance, and induced discrete changes in capillary pCO2 and pO2 within the physiologic range while increasing RPE at LT.