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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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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.

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Jessica L. Bigg, Alexander S.D. Gamble, and Lawrence L. Spriet

Purpose: The purpose of this study was to quantify the internal load of male varsity ice hockey players, using both sessional rating of perceived exertion (sRPE) and the heart rate–derived physiological measure of training impulse (TRIMP), during training sessions and competitions throughout an entire season. Methods: Twenty-seven male varsity ice hockey players (22.1 [1.1] y, 85.9 [5.4] kg, 181.3 [5.1] cm) were included in this longitudinal prospective cohort study. Results: The internal load was significantly higher (P < .001) for games (sRPE: 403 [184] arbitrary units [AU], TRIMP: 98 [59] AU) compared with training sessions (sRPE: 281 [130] AU, TRIMP: 71 [35] AU). The regular season had the highest internal load compared with the preseason and postseason. There was evidence of microcycle periodization with training sessions several days prior to game days having the highest internal load (both sRPE and TRIMP) and tapering down as the subsequent training sessions approached game day. For positional comparisons, the goalies had higher sRPE (346 [151] AU, P < .001) and TRIMP (99 [64] AU, P < .001) compared with defense (sRPE: 295 [130] AU, TRIMP: 65 [29] AU) and forwards (sRPE: 264 [123] AU, TRIMP: 70 [30] AU) for training sessions, but no significant differences were present for competitions. Finally, there was an overall moderate and statistically significant relationship between the sRPE and TRIMP internal load measures (r = .434, P < .001). Conclusions: Internal load was greater during competitions versus training sessions in male varsity ice hockey players, and the microcycle assessment demonstrated that training sessions were tailored to game day. Mesocycle assessment revealed the highest internal loads during the regular season due to dense game scheduling and a short season.

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Dana M. Lis, Matthew Jordan, Timothy Lipuma, Tayler Smith, Karine Schaal, and Keith Baar

Background: Exercise and vitamin C-enriched collagen supplementation increase collagen synthesis, potentially increasing matrix density, stiffness, and force transfer. Purpose: To determine whether vitamin C-enriched collagen (hydrolyzed collagen [HC] + C) supplementation improves rate of force development (RFD) alongside a strength training program. Methods: Using a double-blinded parallel design, over 3 weeks, healthy male athletes (n = 50, 18–25 years) were randomly assigned to the intervention (HC + C; 20 g HC + 50 mg vitamin C) or placebo (20 g maltodextrin). Supplements were ingested daily 60 min prior to training. Athletes completed the same targeted maximal muscle power training program. Maximal isometric squats, countermovement jumps, and squat jumps were performed on a force plate at the same time each testing day (baseline, Tests 1, 2, and 3) to measure RFD and maximal force development. Mixed-model analysis of variance compared performance variables across the study timeline, whereas tests were used to compare the change between baseline and Test 3. Results: Over 3 weeks, maximal RFD in the HC + C group returned to baseline, whereas the placebo group remained depressed (p = .18). While both groups showed a decrease in RFD through Test 2, only the treatment group recovered RFD to baseline by Test 3 (p = .036). In the HC + C group, change in countermovement jumps eccentric deceleration impulse (p = .008) and eccentric deceleration RFD (p = .04) was improved. A strong trend was observed for lower limb stiffness assessed in the countermovement jumps (p = .08). No difference was observed in maximal force or squat jump parameters. Conclusion: The HC + C supplementation improved RFD in the squat and countermovement jump alongside training.

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Bruno P. Melo, Aline C. Zacarias, Joyce C.C. Oliveira, Letícia M. De Souza Cordeiro, Samuel P. Wanner, Mara L. Dos Santos, Gleide F. Avelar, Romain Meeusen, Elsa Heyman, and Danusa D. Soares

We aimed to investigate the combined effects of aerobic exercise (EXE) and cocoa flavanol (COCOA) supplementation on performance, metabolic parameters, and inflammatory and lipid profiles in obese insulin-resistant rats. Therefore, 32 male Wistar rats (230–250 g) were fed a high-fat diet and a fructose-rich beverage for 30 days to induce insulin resistance. Next, the rats were randomized into four groups, orally administered placebo solution or COCOA supplementation (45 mg·kg−1), and either remained sedentary or were subjected to EXE on a treadmill at 60% peak velocity for 30 min, for 8 weeks. Blood samples and peripheral tissues were collected and processed to analyze metabolic and inflammatory parameters, lipid profiles, and morphological parameters. Supplementation with COCOA and EXE improved physical performance and attenuated body mass gain, adipose index, and adipocyte area. When analyzed as individual interventions, supplementation with COCOA and EXE improved glucose intolerance and the lipid profile reduced the concentrations of leptin, glucose, and insulin, and reduced homeostasis assessment index (all effects were p < .001 for both interventions), while ameliorated some inflammatory mediators in examined tissues. In skeletal muscles, both COCOA supplementation and EXE increased the expression of glucose transporter (p < .001 and p < .001), and combined intervention showed additive effects (p < .001 vs. COCOA alone or EXE alone). Thus, combining COCOA with EXE represents an effective nonpharmacological strategy to treat insulin resistance; it could prevent Type 2 diabetes mellitus by improving physical performance, glucose metabolism, neuroendocrine control, and lipid and inflammatory mediators in the liver, pancreas, adipose tissue, and skeletal muscle in obese male insulin-resistant rats.

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Bent R. Rønnestad, Timo Andre Bakken, Vetle Thyli, Joar Hansen, Stian Ellefsen, and Daniel Hammarstrøm

Purpose: Accumulated time at a high percentage of peak oxygen consumption (VO2peak) is important for improving performance in endurance athletes. The present study compared the acute physiological and perceived effects of performing high-intensity intervals with roller ski double poling containing work intervals with (1) fast start followed by decreasing speed (DEC), (2) systematic variation in exercise intensity (VAR), and (3) constant speed (CON). Methods: Ten well-trained cross-country skiers (double-poling VO2peak 69.6 [3.5] mL·min−1·kg−1) performed speed- and duration-matched DEC, VAR, and CON on 3 separate days in a randomized order (5 × 5-min work intervals and 3-min recovery). Results: DEC and VAR led to longer time ≥90% VO2peak (P = .016 and P = .033, respectively) and higher mean %VO2peak (P = .036, and P = .009) compared with CON, with no differences between DEC and VAR (P = .930 and P = .759, respectively). VAR, DEC, and CON led to similar time ≥90% of peak heart rate (HRpeak), mean HR, mean breathing frequency, mean ventilation, and mean blood lactate concentration ([La]). Furthermore, no differences between sessions were observed for perceptual responses, such as mean rate of perceived exertion, session rate of perceived exertion or pain score (all Ps > .147). Conclusions: In well-trained XC skiers, DEC and VAR led to longer time ≥90% of VO2peak compared with CON, without excessive perceptual effort, indicating that these intervals can be a good alternative for accumulating more time at a high percentage of VO2peak and at the same time mimicking the pronounced variation in exercise intensities experienced during XC-skiing competitions.

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Robin Pla, Arthur Leroy, Yannis Raineteau, and Philippe Hellard

Purpose: To quantify the impact of successive competitions on swimming performance in world-class swimmers. Methods: An entire data set of all events swum during a new competition named the International Swimming League was collected. A Bayesian linear mixed model has been proposed to evaluate whether a progression could be observed during the International Swimming League’s successive competitions and to quantify this effect according to event, age, and gender. Results: An overall progression of 0.0005 (0.0001 to 0.0010) m/s/d was observed. The daily mean progression (ie, faster performance) was twice as high for men as for women (0.0008 [0.00 to 0.0014] vs 0.0003 [−0.0003 to 0.0009] m·s−1). A tendency toward higher progression for middle distances (200 and 400 m) and for swimmers of a higher caliber (above 850 FINA [Fédération Internationale de Natation] points) was also observed. Swimmers between 23 and 26 years of age seemed to improve their swimming speed more in comparison with the other swimmers. Conclusions: This new league format, which involves several competitions in a row, seems to allow for an enhancement in swimming performance. Coaches and their support staff can now adapt their periodization plan in order to promote competition participation.

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Jurdan Mendiguchia, Adrián Castaño-Zambudio, Pedro Jiménez-Reyes, Jean–Benoît Morin, Pascal Edouard, Filipe Conceição, Jonas Tawiah-Dodoo, and Steffi L. Colyer

Purpose: Sprint kinematics have been linked to hamstring injury and performance. This study aimed to examine if a specific 6-week multimodal intervention, combining lumbopelvic control and unning technique exercises, induced changes in pelvis and lower-limb kinematics at maximal speed and improved sprint performance. Methods: Healthy amateur athletes were assigned to a control or intervention group (IG). A sprint test with 3-dimensional kinematic measurements was performed before (PRE) and after (POST) 6 weeks of training. The IG program included 3 weekly sessions integrating coaching, strength and conditioning, and physical therapy approaches (eg, manual therapy, mobility, lumbopelvic control, strength and sprint “front-side mechanics”-oriented drills). Results: Analyses of variance showed no between-group differences at PRE. At POST, intragroup analyses showed PRE–POST differences for the pelvic (sagittal and frontal planes) and thigh kinematics and improved sprint performance (split times) for the IG only. Specifically, IG showed (1) a lower anterior pelvic tilt during the late swing phase, (2) greater pelvic obliquity on the free-leg side during the early swing phase, (3) higher vertical position of the front-leg knee, (4) an increase in thigh angular velocity and thigh retraction velocity, (5) lower between-knees distance at initial contact, and (6) a shorter ground contact duration. The intergroup analysis revealed disparate effects (possibly to very likely) in the most relevant variables investigated. Conclusion: The 6-week multimodal training program induced clear pelvic and lower-limb kinematic changes during maximal speed sprinting. These alterations may collectively be associated with reduced risk of muscle strain and were concomitant with significant sprint performance improvement.