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1.
The Impact of Morning versus Afternoon Exercise on Iron Absorption in Athletes.
McCormick, R, Moretti, D, McKay, AKA, Laarakkers, CM, Vanswelm, R, Trinder, D, Cox, GR, Zimmerman, MB, Sim, M, Goodman, C, et al
Medicine and science in sports and exercise. 2019;(10):2147-2155
Abstract
PURPOSE This study examined postexercise inflammatory, hepcidin, and iron absorption responses to endurance exercise performed in the morning versus the afternoon. METHODS Sixteen endurance-trained runners (10 male, 6 female) with serum ferritin (sFer) < 50 μg·L completed a 90-min running protocol (65% vV˙O2max) in the morning (AM), or the afternoon (PM), in a crossover design. An iron-fortified fluid labeled with stable iron isotopes (Fe or Fe) was administered with a standardized meal 30 min following the exercise and control conditions during each trial, serving as a breakfast and dinner meal. Venous blood samples were collected before, immediately after, and 3 h after the exercise and control conditions to measure sFer, serum interleukin-6 (IL-6), and serum hepcidin-25. A final venous blood sample was collected 14 d after each trial to determine the erythrocyte iron incorporation, which was used to calculate iron absorption. Linear mixed-modeling was used to analyze the data. RESULTS Overall, exercise significantly increased the concentrations of IL-6 (4.938 pg·mL; P = 0.006), and hepcidin-25 concentrations significantly increased 3 h after exercise by 0.380 nM (P < 0.001). During the PM trial, hepcidin concentrations exhibited diurnal tendency, increasing 0.55 nM at rest (P = 0.007), before further increasing 0.68 nM (P < 0.001) from prerun to 3 h postrun. Fractional iron absorption was significantly greater at breakfast after the AM run, compared with both the rested condition (0.778%; P = 0.020) and dinner in the AM run trial (0.672%; P = 0.011). CONCLUSIONS Although exercise resulted in increased concentrations of IL-6 and hepcidin, iron was best absorbed in the morning after exercise, indicating there may be a transient mechanism during the acute postexercise window to promote iron absorption opposing the homeostatic regulation by serum hepcidin elevations.
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2.
Effects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis.
Salinero, JJ, Lara, B, Del Coso, J
Research in sports medicine (Print). 2019;(2):238-256
Abstract
The aim of this investigation was to perform a systematic review and meta-analysis to determine the efficacy of the acute ingestion of caffeine (from 3 to 6 mg/kg) to increase performance on variables related to team sports. A systematic review was performed in scientific databases from January to April 2018. All studies included had cross-over experimental designs comparing caffeine to an identical placebo condition. A meta-analysis was performed using the random effects model and pooled standardized mean differences (Glass's Δ). Thirty-four studies published between 2001 and 2018 were included in the analysis. The meta-analysis revealed that caffeine increased single (Δ;95% confidence intervals = 0.19;0.14-0.25; p < 0.01) and repeated jump height (0.29;0.16-0.42; p < 0.01), single (0.16;0.02-0.30; p = 0.03) and repeated sprint velocity (0.14;0.03-0.25; p = 0.02), and reduced the time to complete agility tests (0.41;0.04-0.77; p = 0.03). During team sport matches, caffeine increased total running distance (0.41;0.20-0.62; p < 0.01), distance covered at sprint velocity (0.36;0.12-0.59; p < 0.01) and the number of sprints (0.44;0.18-0.69; p < 0.01). The acute ingestion of a moderate dose of caffeine had a small but significant positive effect on several aspects related to physical performance in team sports.
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3.
Leaders' creation of shared identity impacts group members' effort and performance: Evidence from an exercise task.
Stevens, M, Rees, T, Steffens, NK, Haslam, SA, Coffee, P, Polman, R
PloS one. 2019;(7):e0218984
Abstract
There is growing evidence that leaders' effectiveness derives in part from their creation of a sense of identity that is shared by members of a group they are attempting to lead (i.e., their identity entrepreneurship). Little is known, however, about the impact of identity entrepreneurship in sport and exercise settings, particularly in relation to its effect on group members' effort and performance. Using a pre-post between subjects experimental design, we examined the effect of leaders' identity entrepreneurship on group members' effort and performance during 5km cycling time trials. Following a baseline session (in which time trials were completed individually), participants (N = 72) were randomly allocated to either a high or low identity entrepreneurship condition, and further randomly divided into groups of five (including a leader who was a confederate). In the subsequent test sessions (which participants attended with their fellow group members), leaders displayed either high or low identity entrepreneurship behaviors. Results indicated that, compared to participants in the low identity entrepreneurship condition, those in the high identity entrepreneurship condition maintained greater effort (maximum heart rate), and demonstrated improved (rather than poorer) performance (average power output in the first 60 seconds of time trials). Examination of pacing showed that the largest increases in participants' average power output occurred in the early stages of their second time trials for those in the high identity entrepreneurship condition only. Results provide causal evidence that leaders who create a shared sense of identity among team members are able to inspire greater participant effort and performance.
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4.
Performance and altitude: Ways that nutrition can help.
Caris, AV, Santos, RVT
Nutrition (Burbank, Los Angeles County, Calif.). 2019;:35-40
Abstract
High altitudes are a challenge for human physiology and for sports enthusiasts. Several reasons lead to deterioration in performance at high altitudes. Hypoxia owing to high altitude causes a breakdown of homeostasis with imbalance in several physiological systems, including the immune system. The reduction in mucosal immunity and inflammation and the predominance of the humoral immune response causes a condition of immunosuppression and an increased likelihood of infection. In addition, it is known that worsening of the immune response is associated with reduced performance. On the other hand, immunonutrition plays an important role in modulating the effects of physical exercise on the immune system. However, to our knowledge, few studies have evaluated the effect of nutrition on the immune system after exercise in hypoxia. Although the association between exercise and hypoxia has been shown to be more severe for the body owing to the sum of stressful agents, supplementation with carbohydrates and glutamine seems to play a relevant role in mitigating immunosuppressive effects. These findings, although limited by the fact that they are the result of very few studies, shed light on a relevant theme for sports physiology and nutrition and suggest that both supplements may be useful for athletes, visitors, and workers in high-altitude regions. The aim of this review was to discuss the effects of high-altitude hypoxia on the human body from the point of view of exercise immunology because it is known that transient immunosuppression after strenuous exercise and competition should be followed by reduction in training overload and worse performance.
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5.
The social and psychological health outcomes of team sport participation in adults: An integrative review of research.
Andersen, MH, Ottesen, L, Thing, LF
Scandinavian journal of public health. 2019;(8):832-850
Abstract
Aim: The aim of this article was to review the international scientific research literature about the social and psychological health outcomes associated with participation in team sport and to synthesise the key issues about team sport as a health-promoting activity. Methods: The methodological framework guiding the review process is the integrative research review. A search of 10 key electronic databases was conducted to identify both quantitative and qualitative studies addressing the social and/or psychological health outcomes from participation in a team sport. A total of 6,097 publications were identified and 17 studies met the inclusion criteria. Results: A wide range of different positive social, psychological, and psychosocial health outcomes associated with team sport participation were identified in the studies, with emotional social support, sense of belonging, higher self-esteem, social network, and social interaction being the most frequently reported health benefits. In addition, three key issues influencing the psychological and social health outcomes of team sport participation as a health-promoting activity were identified: (1) team sport versus individual sport, (2) competitive versus non-competitive structure, and (3) commitment and continuation. Conclusions: There is consistent evidence that participation in a team sport is associated with improved social and psychological health independent of the type of team sport, age, somatic, or mental health problems. The findings indicate that team sport could be more efficient in promoting health and ensuring exercise participation and continuation than individual sport. However, when utilising team sports for health purposes, precautions must be taken with regard to their inherent competitive nature.
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The application of mental fatigue research to elite team sport performance: New perspectives.
Russell, S, Jenkins, D, Smith, M, Halson, S, Kelly, V
Journal of science and medicine in sport. 2019;(6):723-728
Abstract
OBJECTIVES Mental fatigue resulting from prolonged periods of demanding cognitive activity, has been found to impair endurance exercise performance and performance in some sport-specific tasks. The application of such research to the elite sporting environment however is limited. DESIGN & METHODS This article reviews the literature relevant to mental fatigue and team sporting performance with aim to provide perspectives on the transferability and significance of currently available evidence to the applied elite sporting context. RESULTS Inconsistent findings in the limited available literature can be attributed to large variations in the participants involved, the nature of the cognitively demanding tasks used to induce mental fatigue and the tests used to assess performance outcomes. Few studies have used trained athletes in combination with performance tests that accurately represent the physiological and technical demands experienced by athletes in competition. While there is growing interest in the acute influence of mental fatigue on exercise performance, a potential cumulative effect of mental fatigue on performance over, for example, a competitive season is an area yet to be investigated. CONCLUSIONS If it is accepted that mental fatigue impairs the performance of some athletes, then improving the ecological validity of research in the area of mental fatigue and sport will significantly advance our understanding of how to better monitor and manage mental fatigue. At the elite level of competition, where outcomes are determined by very small margins of difference, reducing the impact of mental fatigue on performance has potential to be significant.
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7.
Organized Sport Participation From Childhood to Adolescence Is Associated With Bone Mass in Young Adults From the Raine Study.
McVeigh, JA, Howie, EK, Zhu, K, Walsh, JP, Straker, L
Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. 2019;(1):67-74
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Abstract
There is a critical need for longitudinal cohort studies to consider the association of the cumulative exposure of physical activity during childhood and adolescence and bone mass. The aim of this study was to investigate the relationship between organized sports trajectories (that capture distinct and potentially meaningful patterns over critical developmental periods) and bone mass at age 20 years. Participation in organized sport was recorded by parental report at ages 5, 8, 10, 14, and 17 years in 984 offspring (48% female) of a pregnancy cohort (Raine Study). Latent class analysis identified three trajectory classes in each sex. In females, these were "consistent sport participators" (48%), "dropouts" (34%), and "non-participators" (18%); in males, "consistent sport participators" (55%), "dropouts" (37%), and "sport joiners" (8%). Whole-body bone mineral content (BMC) at age 20 years was assessed by dual-energy X-ray absorptiometry (DXA). At age 20 years, after adjustment for covariates measured at age 20 years, including height, lean mass, physical activity, calcium intake, serum 25-hydroxyvitamin D, alcohol, and smoking, males who were "consistent sport participators" had significantly greater whole-body and leg BMC than those who dropped out of sport (p < 0.001), whereas males who joined sports had significantly greater leg BMC than those who dropped out of sport (p = 0.002). Females in the "consistent sport participator" trajectory had significantly greater leg BMC than those who dropped out (all p = 0.004). Participation in organized sport during childhood and adolescence is associated with bone mass at age 20 years. Because attainment of optimal peak bone mass in young adulthood is protective against osteoporosis in later life, this may have long-term skeletal benefits. © 2018 American Society for Bone and Mineral Research.
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Ultra-endurance events in tropical environments and countermeasures to optimize performances and health.
Hermand, E, Chabert, C, Hue, O
International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group. 2019;(1):753-760
Abstract
Physical performance in a tropical environment, combining high heat and humidity, is a difficult physiological challenge that requires specific preparation. The elevated humidity of a tropical climate impairs the thermoregulatory mechanisms by limiting the rate of sweat evaporation. Hence, a proper management of whole-body temperature is required to complete an ultra-endurance event in such an environment. In these long-duration events, which can last from 8 to 20 h, held in hot and humid settings, performance is tightly linked to the ability in maintaining an optimal hydration status. Indeed, the rate of withdrawal in these longer races was associated with lower water intake, and the majority of finishers exhibited alterations in electrolyte balance (e.g., sodium). Hence, this work reviews the effects on performance of high heat and humidity in two representative ultra-endurance sports, ultramarathons and long-distance triathlons, and several countermeasures to counteract the impact of these harsh environmental stresses and maintain a high level of performance, such as hydration, cooling strategies and heat acclimation.
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Optimizing training and competition during the month of Ramadan: Recommendations for a holistic and personalized approach for the fasting athletes.
Chamari, K, Roussi, M, Bragazzi, NL, Chaouachi, A, Abdul, RA
La Tunisie medicale. 2019;(10):1095-1103
Abstract
During the month of Ramadan, Muslim believers of adult-aged and healthy, restrain themselves from food consumption and liquid intake from dawn to sunset (fasting duration varying according to the geographical location and time of the year). Differently from other fasting regimens such as caloric restriction, Ramadan fasting is a unique kind of fasting, being total (i.e., absolute abstain from food as well as fluid), time-restricted, intermittent, and circadian (following the circadian rhythm and the human biological clock). As such, the fasting athletes could potentially suffer from hypohydration, altered sleep pattern and architecture, sleep disturbances, mood swings, immunological alterations, impaired psychomotor performance and overall perceived physical and perhaps, mental fatigue, among others. Hence, Muslim athletes who continue to train and compete during Ramadan faced many challenges. Research has shown that depending on the level of effort, Ramadan fasting could have diverse effects on physical performance; from no effect to marked effects. The present review aims to provide practical recommendations based on an updated, evidence-based synthesis of the existing scholarly literature and/or experts opinions on the topic and subsequently, some useful tips for athletes, coaches, medical and scientific support, and sports managers, in order to guide them on how to promote appropriate behavioral, social and psychological strategies to cope with the changes and potential constraints induced by the observance of Ramadan fasting. These recommendations should be adjusted and coped with, utilizing a holistic approach, rather than focusing on the single alterations/perturbations. Moreover, the implemented strategies should not be "one size fits it all" approach, but should rather take into account the variability among athletes and their specific needs (biological, psychological, cognitive-behavioral), and their social and living environment; as it is clearly more challenging when the individual is performing the Ramadan fasting in a predominantly non-Muslim majority country.
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Cardiovascular, muscular, and skeletal adaptations to recreational team handball training: a randomized controlled trial with young adult untrained men.
Hornstrup, T, Løwenstein, FT, Larsen, MA, Helge, EW, Póvoas, S, Helge, JW, Nielsen, JJ, Fristrup, B, Andersen, JL, Gliemann, L, et al
European journal of applied physiology. 2019;(2):561-573
Abstract
PURPOSE The prevalence of lifestyle diseases has escalated, and effective exercise training programmes are warranted. This study tested the hypothesis that regular participation in small-sided team handball training could provide beneficial health effects on cardiovascular, skeletal, and muscular parameters in young adult untrained men. METHOD Twenty-six untrained 20-30-year-old men were randomly allocated to either a team handball training group (HG; n = 14), which completed 1.9 ± 0.3 training sessions per week over 12 weeks, or an inactive control group (CG; n = 12). Physiological training adaptations were assessed pre- and post interventions by DXA scans, blood samples, muscle biopsies, and physical tests. RESULTS The average heart rate during training was equivalent to 84 ± 4% of maximal heart rate. Compared to CG, HG displayed significant increases in VO2max (11 ± 6%), proximal femur bone mineral density (2 ± 1%), whole-body bone mineral content (2 ± 1%), intermittent endurance performance (32 ± 16%), incremental treadmill test performance (16 ± 7%) and muscle citrate synthase activity (22 ± 28%) as well as decreases in total fat mass (7 ± 7%) and total fat percentage (6 ± 7%) (all p < 0.05). There were no significant changes in muscle mass, blood pressure, resting heart rate, muscle hydroxyl-acyl-dehydrogenase activity, or blood lipids (all p > 0.05). CONCLUSION Participation in regular recreational team handball training was associated with positive cardiovascular, skeletal, and muscular adaptations, including increased maximal oxygen uptake, increased muscle enzymatic activity, and improved bone mineralization as well as lower fat percentage. These findings suggest that recreational team handball training may be an effective health-promoting activity for young adult men.