A link between diurnal preference and a variable number tandem-repeat (VNTR) polymorphism in the PERIOD3 gene (PER3) has been demonstrated: the longer PER3(5) and shorter PER3(4) alleles with preferences for mornings and evenings, respectively. As many competitive events in South Africa for individual athletes are scheduled for the early mornings, we hypothesized that this might favor those athletes with a preference for morning activities. Self-selected white, male cyclists (CYC, n = 125), runners (RUN, n = 120) and Ironman triathletes (IM, n = 287) of European descent were compared with a control population of active, non-competitive individuals (CON, n = 96). The chronotypes of all CYC, RUN and CON participants and a sub-sample of the IM group (n = 49) were assessed using the Horne-Östberg Morningness-Eveningness Questionnaire, and the PER3 VNTR genotype for each participant was determined. The athlete groups contained more morning-type individuals than the CON group (CYC: 72%, n = 90; RUN: 67%, n = 80; IM: 59%, n = 29; CON: 41%, n = 39; p < .001). The prevalence of the PER3(5) allele was greater in the athlete groups (CYC: 61%, n = 152; RUN: 58%, n = 132; IM: 56%, n = 324; CON: 38%, n = 76; p < .001), and more athletes were genotyped as PER3(5/5) than CON individuals (CYC: 41%, n = 51; RUN: 23%, n = 26; IM: 28%, n = 81, CON: 9%, n = 8; p < .001). A strong relationship between chronotype and PER3 VNTR genotype was observed (p < .001). Finally, the time of day at which the athletes preferred to train was related to their chronotype (p < .001). This is the first study of its kind in a South African sporting population, and the results have not yet been replicated. These data suggest that white males of European descent participating in individual endurance sports in South Africa are more likely to be morning types. Furthermore, the PER3 VNTR may be one of the factors contributing to this observation.
A recent study found that South African endurance athletes are likely to be morning-types and carry the PER3(5) allele, which has been associated with a preference for mornings. The aim of this study was to measure the response of morning-type cyclists to a standardised bout of exercise performed at different times of the day. Participants ncluded 20 trained male cyclists (age: 39.8 ± 7.7 years, VO2max: 51.0 ± 7.0 ml · kg(-1) · min(-1), training: 166 ± 98 km · wk(-1)), categorised as morning-types (mean Horne-Östberg score: 68.3 ± 5.5) and carrying the PER3(5) allele. They completed a 17-min sub-maximal cycling test at 60%, 80% and 90% of maximum heart rate (HRmax) at 06h00, 10h00, 14h00, 18h00 and 22h00. These morning-type cyclists reported higher ratings of perceived exertion when cycling at 60% (P = 0.044), 80% (P < 0.001) and 90% (P < 0.001) of HRmax during the evening (18h00 and 22h00) compared to the other sessions (0600, 10h00 and 14h00). This was despite absolute power output, speed and cadence displaying no time-of-day differences. Thus, morning-type cyclists perceive the same relative intensity workload to be harder in the evening compared to the morning. This may have implications for both training and competition scheduling, and highlights the importance of considering individual chronotype in sports in which diurnal variation may be relevant to training and competition.
ObjectiveTo review risk factors associated with acute respiratory illness (ARill) in athletes, including non-infectious ARill and suspected or confirmed acute respiratory infections (ARinf).DesignSystematic review.Data sourcesElectronic databases: PubMed-Medline, EbscoHost and Web of Science.Eligibility criteriaOriginal research articles published between January 1990 and July 2020 in English were searched for prospective and retrospective full text studies that reported quantitative data on risk factors associated with ARill/ARinf in athletes, at any level of performance (elite/non-elite), aged 15–65 years.Results48 studies (n=19 390 athletes) were included in the study. Risk factors associated with ARill/ARinf were: increased training monotony, endurance training programmes, lack of tapering, training during winter or at altitude, international travel and vitamin D deficits. Low tear-(SIgA) and salivary-(IgA) were immune biomarkers associated with ARill/ARinf.ConclusionsModifiable training and environmental risk factors could be considered by sports coaches and athletes to reduce the risk of ARill/ARinf. Clinicians working with athletes can consider assessing and treating specific nutritional deficiencies such as vitamin D. More research regarding the role and clinical application of measuring immune biomarkers in athletes at high risk of ARill/ARinf is warranted.PROSPERO registration numberCRD42020160928.
ObjectiveTo determine the incidence of acute respiratory illness (ARill) in athletes and by method of diagnosis, anatomical classification, ages, levels of performance and seasons.DesignSystematic review and meta-analysis.Data sourcesElectronic databases: PubMed-Medline, EbscoHost and Web of Science.Eligibility criteriaOriginal research articles published between January 1990 and July 2020 in English reporting the incidence of ARill in athletes, at any level of performance (elite/non-elite), aged 15–65 years.ResultsAcross all 124 studies (n=1 28 360 athletes), the incidence of ARill, estimated by dividing the number of cases by the total number of athlete days, was 4.7 (95% CI 3.9 to 5.7) per 1000 athlete days. In studies reporting acute respiratory infections (ARinf; suspected and confirmed) the incidence was 4.9 (95% CI 4.0 to 6.0), which was similar in studies reporting undiagnosed ARill (3.7; 95% CI 2.1 to 6.7). Incidences of 5.9 (95% CI 4.8 to 7.2) and 2.8 (95% CI 1.8 to 4.5) were found for studies reporting upper ARinf and general ARinf (upper or lower), respectively. The incidence of ARinf was similar across the different methods to diagnose ARinf. A higher incidence of ARinf was found in non-elite (8.7; 95% CI 6.1 to 12.5) vs elite athletes (4.2; 95% CI 3.3 to 5.3).Summary/conclusionsThese findings suggest: (1) the incidence of ARill equates to approximately 4.7 per athlete per year; (2) the incidence of upper ARinf was significantly higher than general (upper/lower) ARinf; (3) elite athletes have a lower incidence of ARinf than non-elite athletes; (4) if pathogen identification is not available, physicians can confidently use validated questionnaires and checklists to screen athletes for suspected ARinf. For future studies, we recommend that a clear diagnosis of ARill is reported.PROSPERO registration numberCRD42020160472.
Individual sport athletes have been shown to comprise unusually high proportions of morning-types (MTs) coupled with a higher prevalence of the morningness-associated PERIOD3 variable number tandem repeat (VNTR) allele, PER3. The degree to which type of sport selected is influenced by either chronotype or genotype, or the extent to which sporting environment contributes to chronotype is unclear. The aim of this study was to assess chronotype and PER3 VNTR polymorphism frequencies in team sport players and non-athletic controls. South African male Super Rugby players (RUG, n = 120) and a control population of males with habitually low levels of physical activity (defined as exercise no more than twice a week; CON, n = 117) took part in this study. Participants completed the Horne-Östberg morningness-eveningness questionnaire to determine chronotype and donated buccal cell or blood samples from which PER3 VNTR genotype was established. There were more MTs in the RUG (47%) than CON group (23%, p < 0.001), more evening-types in the CON group (18%) compared to the RUG group (3%, p < 0.001), but no differences in PER3 VNTR genotype (p = 0.619) or allele (p = 0.758) frequencies. In both groups, more people carried the PER3 allele (RUG: 63%, CON: 62%). Chronotype was associated with genotype in the CON (p = 0.004) but not the RUG group (p = 0.895). Unlike the individual sport endurance athletes previously studied in whom the PER3 allele predominated, the PER3 VNTR genotype distribution in these team sport players was similar to that of the general population. We hypothesise that the absence of any chronotype-genotype relationship in these rugby players is because their diurnal preference is shifted towards morningness through habitual athletic behaviour.
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