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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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Tim Woodman and Charlotte Welch

Individuals high in alexithymia use high-risk sport to regulate their anxiety. Given the conceptual similarities between arduous high-risk sports and extreme endurance running, we investigated the relationship between alexithymia and the anxiolytic effects of endurance running. We measured marathon and ultramarathon runners (n = 35) on alexithymia, and pre- and postrace anxiety. Bootstrapped regression analyses using MEMORE revealed that alexithymia moderated the relationship between pre- and postrace anxiety such that there was a significant anxiety reduction for individuals high in alexithymia only. In conclusion, extreme endurance running provides an emotion regulation function for individuals high in alexithymia. The modest sample size points to the need for replication and further exploration.

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Jeane Franco Pires Medeiros, Michelle Vasconcelos de Oliveira Borges, Aline Alves Soares, Elys Costa de Sousa, José Ronaldo Ribeiro da Costa, Weberthon Alessanderson Costa Silva, Magnus Vinícius Bezerra de Sousa, Vivian Nogueira Silbiger, Paulo Moreira Silva Dantas, and André Ducati Luchessi

Although vitamin D is related to cardiorespiratory fitness and muscle strength, there is no evidence in the literature about the genetic influence of the response to vitamin D supplementation and improvements in these parameters. Therefore, we evaluate the effect of longitudinal supplementation of vitamin D on parameters of physical fitness in monozygotic twins. In total, 74 participants were included, with a mean age of 25 years, divided into two groups, one group received supplementation with cholecalciferol for 60 days and the other group did not. Cardiorespiratory fitness and muscle strength were measured before and after supplementation through maximal treadmill tests and dynamometry, respectively. Wilcoxon tests were used to compare intragroup results and the Mann–Whitney test to examine intergroup differences. There was an increase in the serum concentration of vitamin D in participants who ingested the supplementation. Cardiorespiratory fitness improved after supplementation through increases in the values of maximum oxygen consumption of 28% (p < .001). Muscle strength in left hand grip increased 18% in participants who received the supplement (p = .007). Sixty days of cholecalciferol supplementation improved cardiorespiratory fitness and upper limb muscle strength.

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Katherine L. Schofield, Holly Thorpe, and Stacy T. Sims

Aim: To highlight energy availability status, resting metabolic rate measures, dietary protein intake, and testosterone concentration in 4 elite male track cycling athletes (mean [SD]: age: 20.8 [1.5] y, body mass: 76.3 [3.6] kg, height: 181.8 [2.9] cm). Method: A cross-sectional observation included measures of energy availability (energy intake minus exercise energy expenditure, divided by fat-free mass), resting metabolic rate from indirect calorimetry, dietary protein intake from food records, blood analysis to assess sex hormone status, and performance markers. Results: Midrange testosterone (16.9–19.8 nmol/L), lowered resting metabolic rate ratio (0.76–0.98), varied luteinizing hormone (4–10 U/L), and suboptimal energy availability (26–41 kcal/kg fat-free mass/d, range) were observed in the male track cyclists. Protein intakes ranged from 2.0 g to 2.8 g protein/kg/d. Conclusion: The current cohort may have within-day energy deficiency, putting them in a catabolic state.

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Toshiyuki Ohya, Kenta Kusanagi, Jun Koizumi, Ryosuke Ando, Keisho Katayama, and Yasuhiro Suzuki

Purpose: Inspiratory muscle strength training (IMST) can improve exercise performance. Increased maximal inspiratory mouth pressure (MIP) could be beneficial for swimmers to enhance their performance. This study aimed to clarify the effect of high-intensity IMST for 6 weeks on MIP and swimming performance in highly trained competitive swimmers. Methods: Thirty male highly trained competitive swimmers were assigned to high-intensity IMST (HI; n = 10), moderate-intensity IMST (MOD; n = 10), and control (n = 10) groups. The 6-week IMST intervention comprised twice daily sessions for 6 d/wk at inspiratory pressure threshold loads equivalent to 75% MIP (HI) and 50% MIP (MOD). Before and after the intervention, MIP and swimming performance were assessed. Swimming performance was evaluated in free and controlled frequency breathing 100-m freestyle swimming time trials in a 25-m pool. For controlled frequency breathing, participants took 1 breath every 6 strokes. Results: The MIP values after 2 and 6 weeks of IMST in the HI and MOD groups were significantly higher than those before IMST (P = .0001). The magnitudes of the MIP increases after 6 weeks of IMST did not differ between the HI (13.4% [8.7%]) and MOD (13.1% [10.1%]) groups (P = .44). The 100-m freestyle swimming times under the controlled frequency condition were significantly shorter after IMST than those before IMST in both the HI (P = .046) and MOD (P = .042) groups. Conclusions: Inspiratory pressure threshold load equivalent to 50% MIP could be sufficient to improve MIP and swimming performance under the controlled frequency breathing condition in highly trained competitive swimmers.

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Olivier Girard, Romain Leuenberger, Sarah J. Willis, Fabio Borrani, and Grégoire P. Millet

Purpose: The authors compared the effects of active preconditioning with local and systemic hypoxia during submaximal cycling. Methods: On separate visits, 14 active participants completed 4 trials. Each visit was composed of 1 preconditioning phase followed, after 40 minutes of rest, by 3 × 6-minute cycling bouts (intensity = 85% of critical power; rest = 6 min). The preconditioning phase consisted of 4 × 5-minute cycling bouts at 1.5 W·kg−1 (rest = 5 min) in 4 conditions: control (no occlusion and normoxia), blood flow restriction (60% of total occlusion), HYP (systemic hypoxia; inspired fraction of oxygen = 13.6%), and blood flow restriction + HYP (local and systemic hypoxia combined). Results: During the preconditioning phase, there were main effects of both systemic (all P < .014) and local hypoxia (all P ≤ .001) on heart rate, arterial oxygen saturation, leg discomfort, difficulty of breathing, and blood lactate concentration. Cardiorespiratory variables, gross efficiency, energy cost, and energy expenditure during the last minute of 6-minute cycling bouts did not differ between conditions (all P > .105). Conclusion: Local and systemic hypoxic stimuli, or a combination of both, during active preconditioning did not improve physiological responses such as cycling efficiency during subsequent submaximal cycling.

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Kathleen H. Miles, Brad Clark, Jocelyn K. Mara, Peter M. Fowler, Joanna Miller, and Kate L. Pumpa

Purpose: To compare the habitual sleep of female basketball and soccer athletes to age- and sex-matched controls and to characterize the sleep of basketball and soccer athletes at different competition locations and on the days surrounding competition. Methods: Using an observational case–control design, 41 female participants were recruited to participate, consisting of 11 basketball athletes (mean [SD]: age = 24.1 [4.9] y), 10 soccer athletes (24.8 [6.4] y), and 20 nonathletic controls (24.2 [2.8] y). Sleep was monitored using actigraphy for four 7-day periods throughout the preseason and subsequent competition season. Generalized linear models were used to analyze the effect of group and competition situation (eg, Home or Away) on sleep. Results: During habitual conditions, basketball athletes had longer sleep durations (7.4 [1.5] h) than soccer athletes (7.0 [1.2] h, P < .001) and controls (7.3 [1.2] h, P = .002). During competition, basketball and soccer athletes had longer sleep durations following home (7.7 [1.7] and 7.2 ± 1.3 h) compared with away games (6.8 [1.8] and 7.0 [1.3] h). In addition, basketballers went to bed earlier (23:49 [01:25]) and woke earlier (07:22 [01:59]) following away games compared with soccer athletes (00:10 [01:45] and 08:13 [01:45]). Conclusions: Basketballers had longer habitual sleep durations compared with soccer athletes and nonathletic controls. During competition, basketballers had earlier bed and wake times compared with soccer athletes following away games, highlighting the need for individualized sleep strategies.