Takashi Kawahara

ACTN3 R577X Genotype is Associated with Sprinting in Elite Japanese Athletes

The ACTN3 R577X genotype has been found to associate with sprint/power phenotypes in all elite athlete cohorts investigated. This association has not been extensively studied in elite Asian athletes. The present study was undertaken to investigate the association between the ACTN3 R577X genotype and elite Japanese track and field athlete status. 299 elite Japanese track and field athletes (134 sprint/power athletes; 165 endurance/middle-power athletes) and 649 Japanese controls were genotyped for the ACTN3 R577X polymorphism. All athletes were of national or international level. Sprint/power athletes showed a higher frequency of RR + RX genotype than controls (111/134 [82.8%] vs. 478/649 [73.7%], P = 0.025 under the R-dominant model), while there was no significant difference between endurance/middle-power athletes and controls (126/165 [76.4%] vs. 478/649 [73.7%], P = 0.48 under the R-dominant model). Sprinters with the RR + RX genotype had significantly faster personal best times for the 100u2009m than those with XX genotype (10.42 ± 0.05u2009s vs. 10.64 ± 0.09u2009s, P = 0.042); no such association was found in the 400u2009m sprinters (47.02 ± 0.36u2009s vs. 47.56 ± 0.99u2009s, P = 0.62). ACTN3 R577X genotype is associated with sprint/power performance in elite Japanese track and field athletes, especially short sprint performance.

Mitochondrial haplogroups associated with elite Japanese athlete status

Purpose It has been hypothesised that certain mitochondrial haplogroups, which are defined by the presence of a characteristic cluster of tightly linked mitochondrial DNA polymorphisms, would be associated with elite Japanese athlete status. To examine this hypothesis, the frequencies of mitochondrial haplogroups found in elite Japanese athletes were compared with those in the general Japanese population. Methods Subjects comprised 139 Olympic athletes (79 endurance/middle-power athletes (EMA), 60 sprint/power athletes (SPA)) and 672 controls (CON). Two mitochondrial DNA fragments containing the hypervariable sequence I (m16024–m16383) of the major non-coding region and the polymorphic site at m.5178C>A within the NADH dehydrogenase subunit 2 gene were sequenced, and subjects were classified into 12 major mitochondrial haplogroups (ie, F, B, A, N9a, N9b, M7a, M7b, M*, G2, G1, D5 or D4). The mitochondrial haplogroup frequency differences among EMA, SPA and CON were then examined. Results EMA showed an excess of haplogroup G1 (OR 2.52, 95% CI 1.05 to 6.02, p=0.032), with 8.9% compared with 3.7% in CON, whereas SPA displayed a greater proportion of haplogroup F (OR 2.79, 95% CI 1.28 to 6.07, p=0.007), with 15.0% compared with 6.0% in CON. Conclusions The results suggest that mitochondrial haplogroups G1 and F are associated with elite EMA and SPA status in Japanese athletes, respectively.

Use of supplements by young elite Japanese athletes participating in the 2010 youth Olympic games in Singapore.

Objective:To investigate the prevalence of supplement use among young elite Japanese athletes. Design:Survey study. Setting:2010 Youth Olympic Games, Singapore. Participants:Data were collected from individual interviews during medical evaluations of 75 athletes selected for the Japanese national team. Main Outcome Measures:Main outcome measures included the use of supplements, products used, frequency of use, purpose of use, and relationships between supplement use and athlete attitudes toward a balanced diet. Results:All 75 athletes agreed to participate in this study, and individual interviews by pharmacists made it possible to collect complete answers from all athletes. Of these athletes, 47 (62.7%) used 1 or more supplement products (average number of products used, 1.1 ± 1.3). The most popular supplement was amino acids, which were used by 33 athletes (44.0%). Of the supplements used, 28 (32.6%) were taken every day, whereas 28 (32.6%) were used only on special occasions. Moreover, 34 of the supplement products (39.5%) were taken to enhance recovery from fatigue, whereas 19 (22.1%) were used to improve athletic performance. Statistical analysis suggested that there was no significant relationship between supplement use and attitudes toward a balanced diet. Conclusions:The results revealed widespread supplement use among young elite athletes in the Japanese national team for the Singapore Youth Olympic Games in 2010. Moreover, these athletes apparently used supplements without considering the effects of their normal diets.

Polymorphisms in the control region of mitochondrial DNA associated with elite Japanese athlete status

The control region of mitochondrial DNA (mtDNA) contains the main regulatory elements for mtDNA replication and transcription. Certain polymorphisms in this region would, therefore, contribute to elite athletic performance, because mitochondrial function is one of determinants of physical performance. The present study was undertaken to examine the effect of polymorphisms in this region on elite athlete status by sequencing the mtDNA control region. Subjects comprised 185 elite Japanese athletes who had represented Japan at international competitions (i.e., 100 endurance/middle‐power athletes: EMA; 85 sprint/power athletes: SPA), and 672 Japanese controls (CON). The mtDNA control region was analyzed by direct sequencing. Frequency differences of polymorphisms (minor allele frequency ≥u20090.05) in the mtDNA control region between EMA, SPA, and CON were examined. EMA displayed excess of three polymorphisms [m.152T>C, m.514(CA)n repeat (nu2009≥u20095), and poly‐C stretch at m.568–573 (Cu2009≥u20097)] compared with CON. On the other hand, SPA showed greater frequency of the m.204T>C polymorphism compared with CON. In addition, none of the SPA had m.16278C>T polymorphism, whereas the frequencies of this polymorphism in CON and EMA were 8.3% and 10.0%, respectively. These findings imply that several polymorphisms detected in the control region of mtDNA may influence physical performance probably in a functional manner.

Postural instability at a simulated altitude of 5,000 m before and after an expedition to Mt. Cho-Oyu (8,201 m).

To clarify the effects of altitude acclimatization on postural instability at altitudes, six female climbers stood with their eyes open or closed on a force-measuring platform under normoxia (NC) and hypobaric hypoxia, equivalent to a 5,000xa0m altitude (HC), before and after an expedition to Mt. Cho-Oyu (8,201xa0m). The expedition extended over 84xa0days. We recorded sways in the center of foot pressure, electromyograms (EMGs) of lower-leg muscles, blood components and arterial oxygen saturation (SpO2). Before the expedition, the maximum amplitude of sway with the eyes open and integrated EMG from the medial gastrocnemius increased for HC. After the expedition, red blood cell (from 423.4xa0±xa015.4 to 498.0xa0±xa024.5xa0×xa0104xa0μl−1), hemoglobin content (from 12.6xa0±xa00.32 to 14.5xa0±xa01.00xa0g/dl) and 2,3-diphosphoglycerate (from 1.93xa0±xa00.21 to 2.24xa0±xa00.34xa0μmol/ml) increased. The SpO2 under HC increased from 69.2xa0±xa09.6 to 77.2xa0±xa010.0%. The maximum amplitude of sway with the eyes open decreased for HC. No difference in the sway path length and integrated EMGs was observed between NC and HC. These results suggest that acclimatization can improve the impaired postural stability on initial arrival at altitudes. However, it is still unclear how long acclimatization period is needed. Further studies are needed to reveal this point.

Comprehensive analysis of common and rare mitochondrial DNA variants in elite Japanese athletes: a case–control study

The purpose of the present study was to identify mitochondrial DNA (mtDNA) polymorphisms and rare variants that associate with elite Japanese athletic status. Subjects comprised 185 elite Japanese athletes who had represented Japan at international competitions (that is, 100 endurance/middle-power athletes: EMA; 85 sprint/power athletes: SPA) and 672 Japanese controls (CON). The entire mtDNA sequences (16u2009569u2009bp) were analyzed by direct sequencing. Nucleotide variants were detected at 1488 sites in the 857 entire mtDNA sequences. A total of 311 variants were polymorphisms (minor allele frequency⩾1% in CON), and the frequencies of these polymorphisms were compared among the three groups. The EMA displayed excess of seven polymorphisms, including subhaplogroup D4e2- and D4g-specific polymorphisms, compared with CON (P<0.05), whereas SPA displayed excess of three polymorphisms and dearth of nine polymorphisms, including haplogroup G- and subhaplogroup G2a-specific polymorphisms, compared with CON (P<0.05). The frequencies of 10 polymorphisms, including haplogroup G- and subhaplogroup G2a-specific polymorphisms, were different between EMA and SPA (P<0.05): although none of these polymorphisms differed significantly between groups after correcting for multiple comparison (false discovery rate q-value⩾0.05). The number of rare variants in the 12S ribosomal RNA and NADH dehydrogenase subunit I genes were also higher in SPA than in CON (P<0.05). Analysis of the entire mtDNA of elite Japanese athletes revealed several haplogroup- and subhaplogroup-specific polymorphisms to be potentially associated with elite Japanese athletic status.

CNTFR Genotype and Sprint/power Performance: Case-control Association and Functional Studies.

The aim of this study was to investigate whether rs41274853 in the 3-untranslated region of the ciliary neurotrophic factor receptor gene (CNTFR) is associated with elite sprint/power athletic status and assess its functional significance. A total of 211 Japanese sprint/power track and field athletes (62 international, 72 national, and 77 regional athletes) and 814 Japanese controls were genotyped at rs41274853. Luciferase reporter assay was conducted to investigate whether this C-to-T polymorphism affects binding of microRNA miR-675-5p to this region. The TT genotype was significantly more frequent among international sprint/power athletes (19.4%) than in the controls after Bonferroni correction (7.9%, P=0.036, OR=2.81 [95% CI: 1.43-5.55]). Furthermore, in non-athletic young/middle-aged men (n=132), TT genotype carriers exhibited significantly greater leg extension power (26.6±5.4 vs. 24.0±5.4u2009W/kg BW, P=0.019) and vertical jump performance (50.1±6.9 vs. 47.9±7.5u2009cm, P=0.047) than the CC+CT genotype carriers. Reporter assays revealed that the miR-675-5p binds to this polymorphic region within the CNTFR mRNA, irrespective of the rs41274853 allele present. Although the functional significance of the rs41274853 polymorphism remains unclear, the CNTFR is one of the candidate genes contributing to sprint/power performance.

Use of supplements by Japanese elite athletes for the 2012 Olympic Games in London.

Objective:To investigate supplement use among Japanese elite athletes. Design:We conducted a cross-sectional survey study using individual interviews during athletes medical evaluations. Setting:One to 5 months before the Olympic Games in 2012, London, United Kingdom. Participants:Five hundred fifty-two Japanese athletes for the London Games, including candidates. Independent Variables:Sex, sports, supplement category, and participation. Main Outcome Measures:Whether athletes used supplements, what products were used, the frequency and purposes of use, and from what sources athletes received information on supplements. Results:All 552 athletes were interviewed by pharmacists regarding supplement use and agreed to the survey. Of them, 452 (81.9%) used 1 or more supplement products in the year before the study; a total of 952 different products (mean = 1.7, SD = 1.4) were used. The most commonly used supplement was amino acids (310 athletes; 56.2%), and 358 (38.7%) of the total products were amino acids. Of the athletes, 241 (43.7%) took at least 1 supplement daily, and of the supplements, 457 (49.4%) were taken daily. The most common purpose for supplement use was recovery from fatigue—327 (59.2%) athletes chose this answer, and 486 (52.5%) products were used for this purpose. Finally, regarding athletes information sources on supplements, coaches, managers, and trainers were the most frequent advisors (275 athletes, 49.8%; 466 products, 50.4%). Conclusions:The results revealed widespread supplement use among Japanese elite athletes for the London Olympic Games. Education system was required not only for athletes but also for athletes entourage, such as coaches, managers, trainers, and supplement companies. Clinical Relevance:This study will provide basic data for establishing an education system that would better guide athletes use of supplements.

Sleep quality under mild hypoxia in men with low hypoxic ventilatory response.

Abstract The present study evaluated whether slow-wave sleep and whole-night delta power of the non-rapid eye movement (NREM) sleep electroencephalogram (EEG) decrease during sleep at a simulated altitude of 2000 m, and whether such changes related to measures of hypoxic ventilatory response (HVR). This study consisted of two parts; in the first, HVR was measured in 41 subjects and each seven subjects with the lowest or the highest HVR were selected for the subsequent sleep study. In the second part, polysomnogram, arterial oxygen saturation (SpO2) and respiratory events are recorded on the selected subjects under normoxic and hypoxic conditions. Hypoxia decreased SpO2 and increased respiratory disturbances for both groups. The low HVR group, but not the high HVR group, showed decreases in the whole-night delta power of NREM sleep EEG under hypoxia. On the other hand, two subjects in the high HVR group, who showed relatively high apnoea indices, also showed lower SpO2 nadirs and decreases in the whole-night delta power under hypoxia. These results suggest that acute hypoxia equivalent to that at a 2000 m altitude decreases slow-wave sleep in individuals that show low HVR. However, low HVR may not be the only, but one of some factors that decrease the whole-night delta power under hypoxia. Therefore, it was not sufficient to identify individuals likely to be susceptible to deteriorated sleep quality at a simulated altitude of 2000 m only using the HVR test. Other factors, which relate to respiratory instabilities, should be taken into consideration to identify them.

Sleep quality in athletes under normobaric hypoxia equivalent to 1500 m altitude: A polysomnographic study

Abstract In the present study, we evaluated the duration of slow-wave sleep (Stage 3 and 4) and total delta power (< 3Hz) in all-night non-rapid eye movement (NREM) sleep electroencephalograms (EEGs) of athletes during normobaric hypoxia at simulated altitudes of 1500 m. Seven male athletes slept for two nights in a normoxic condition and one night in an hypoxic condition equivalent to an altitude of 1500 m. Whole-night polysomnographic recordings, thoracic and abdominal motion, nasal and oral airflow, and blood oxygen saturation (SpO2) were recorded. Visual sleep stage scoring and fast Fourier transformation analyses of EEG were performed using 30-s epochs. Mean and minimum SpO2 decreased significantly during sleep in the hypoxic condition. Between groups, changes in heart rate, respiratory disturbance measures including apnoea and hypopnoea, slow-wave sleep and total delta power of the all-night NREM sleep EEG were small and non-significant for the hypoxic condition. However, individual difference in time at an SpO2 below 90% were large in the hypoxic condition, and both slow-wave sleep and total delta power of all-night NREM sleep EEG decreased in three participants who spent a prolonged time below 90% SpO2. The present results suggest that monitoring time below 90% SpO2 is recommended when studying individuals living-high schedule even under hypoxic conditions equivalent to an altitude of 1500 m.