External validation of a prediction model for estimating fat mass in children and adolescents in 19 countries: individual participant data meta-analysis.

OBJECTIVE: To evaluate the performance of a UK based prediction model for estimating fat-free mass (and indirectly fat mass) in children and adolescents in non-UK settings. DESIGN: Individual participant data meta-analysis. SETTING: 19 countries. PARTICIPANTS: 5693 children and adolescents (49.7% boys) aged 4 to 15 years with complete data on the predictors included in the UK based model (weight, height, age, sex, and ethnicity) and on the independently assessed outcome measure (fat-free mass determined by deuterium dilution assessment). MAIN OUTCOME MEASURES: The outcome of the UK based prediction model was natural log transformed fat-free mass (lnFFM). Predictive performance statistics of R2, calibration slope, calibration-in-the-large, and root mean square error were assessed in each of the 19 countries and then pooled through random effects meta-analysis. Calibration plots were also derived for each country, including flexible calibration curves. RESULTS: The model showed good predictive ability in non-UK populations of children and adolescents, providing R2 values of >75% in all countries and >90% in 11 of the 19 countries, and with good calibration (ie, agreement) of observed and predicted values. Root mean square error values (on fat-free mass scale) were <4 kg in 17 of the 19 settings. Pooled values (95% confidence intervals) of R2, calibration slope, and calibration-in-the-large were 88.7% (85.9% to 91.4%), 0.98 (0.97 to 1.00), and 0.01 (-0.02 to 0.04), respectively. Heterogeneity was evident in the R2 and calibration-in-the-large values across settings, but not in the calibration slope. Model performance did not vary markedly between boys and girls, age, ethnicity, and national income groups. To further improve the accuracy of the predictions, the model equation was recalibrated for the intercept in each setting so that country specific equations are available for future use. CONCLUSION: The UK based prediction model, which is based on readily available measures, provides predictions of childhood fat-free mass, and hence fat mass, in a range of non-UK settings that explain a large proportion of the variability in observed fat-free mass, and exhibit good calibration performance, especially after recalibration of the intercept for each population. The model demonstrates good generalisability in both low-middle income and high income populations of healthy children and adolescents aged 4-15 years.

Trends in Weather Conditions and Performance by Age Groups Over the History of the Berlin Marathon.

The effect of different environmental conditions such as temperature, wind, barometric pressure, and precipitation has been well investigated in elite marathoners, but not by age categories (i.e., age group marathoners). The aim of the study was to investigate the potential influence of environmental conditions such as temperature, precipitation, and atmospheric pressure on marathon performance in age group marathoners competing in the 'Berlin Marathon' from 1974 to 2019. A total of 869,474 valid finisher records were available for analysis, of which 711,136 correspond to males and 158,338 to females. The influence of temperature, atmospheric pressure, and precipitation on marathon race times was investigated in age group marathoners grouped in 5-year-intervals. Within the 46 years of Berlin marathons under investigation, there was some level of precipitation for 18 years, and 28 years without any rain. Sunshine was predominant in 25 of the events, whilst in the other 21 years, cloud cover was predominant. Marathon race times were significantly and positively correlated with age (i.e., older runners were slower than younger runners) where the correlation was higher for males than for females. Marathon race times were significantly and positively correlated with both the hours of sunshine and the daily maximum temperature. The fastest marathon runners (meaning the minimum times) achieved the fastest race times on race days with higher maximum temperatures (i.e., 15-30°C). Daily maximum temperatures showed an influence on age group marathoners from age group 35-40 years and older. Higher precipitation levels impaired performance across most age groups. In summary, higher daily maximum temperatures (i.e., >15°C) and higher precipitation levels impaired performance of master marathoners (i.e., 35-40 years and older) competing in the 'Berlin Marathon' in the last 45 years. Master marathoners should start in marathon races with temperatures < 15°C and no precipitation in order to achieve a fast marathon race time.

Age-Related Decline in Vertical Jumping Performance in Masters Track and Field Athletes: Concomitant Influence of Body Composition.

Vertical jumping power declines with advancing age, which is theoretically explicable by loss of muscle mass and increases in body fat. However, the results of previous cross-sectional studies remain inconsistent on these relationships. The present study included 256 masters athletes who competed at the 2018 track and field world championships in Málaga, Spain. We assessed body composition with bioelectrical impedance (Inbody S10) and vertical jumping power with a Leonardo ground reaction force platform. Relationships between age, jumping power, and body composition were analyzed by correlation and regression analyses. Hierarchical multiple regression analysis was used to evaluate effects of each factor on vertical jumping power. Age-related rates of decreases in maximal power and jump height were similar between male and female athletes. Percent fat-free mass and percent body fat were negatively and positively, respectively, associated with age in masters athletes and were comparable to those previously observed in the general population. Moreover, these effects in body composition can, to a great extent, explain the age-related decline in jumping power, an effect that seems at least partly independent of age. Finally, the multiple regression model to determine independent predictors of vertical jump performance yielded an overall R 2 value of 0.75 with the inclusion of (1) athletic specialization in power events, (2) percent fat-free mass, and (3) phase angle. However, partial regression yielded significant effects of age, but not gender, on peak power, even when adjusting for athletic specialization, percent fat-free mass, and phase angle. We concluded that loss of skeletal muscle mass and changes in bio-impedance phase angle are important contributors to the age-related reduction in anaerobic power, even in adults who maintain high levels of physical activity into old age. However, age per se remains a significant predictor of vertical jump performance, further demonstrating deteriorated muscle quality at old age (sarcosthenia).

A Simple Equation to Estimate Half-Marathon Race Time From the Cooper Test

BACKGROUND: Half-marathon races have become increasingly more popular with many recreational athletes all around the world. New and recreational runners are likely to have the greatest need for training advice to set running paces during long-distance races. PURPOSE: To develop a simple equation to estimate half-marathon time from the Cooper test and verify its validity. METHODS: One hundred ninety-eight recreational runners (177 men and 21 women, 40 [6.8] years and 33.7 [8] years, respectively) participated in this study. All runners completed the Cooper test 7 to 10 days prior to races. A stepwise multiple regression analysis was performed to select the main predictors of half-marathon time. RESULTS: Simple correlation analysis showed that Cooper test performance (distance) was a good construct to estimate half-marathon time (r = -.906; 95% confidence interval, -0.927 to -0.877; P < .0001). The authors also derived an equation with a high predictive validity (R2 = .82; standard error of estimation = 5.19 min) and low systematic bias (mean differences between the predicted value and the criterion of 0.48 [5.2] min). Finally, the concordance coefficient of correlation (.9038) and proportional bias analysis (Kendall τ = -.0799; 95% confidence interval, -0.184 to 0.00453; P = .09) confirmed a good concurrent validity. CONCLUSION: In this study, the authors derived an equation from the Cooper test data with a high predictive and concurrent validity and low bias.

Effects of detraining on breathing pattern and ventilatory efficiency in young soccer players.

BACKGROUND: This study investigated the effects of detraining on breathing pattern. The aim of this study was to evaluate the effect of a six-week detraining period on breathing patterns and ventilatory efficiency. METHODS: Fourteen young soccer players were evaluated at the end of a competitive season and after a six-week detraining period. Assessment of respiratory efficiency was based on VE/VCO2 slope changes below 70% of exercise intensity. All participants underwent twice an incremental graded exercise test up to exhaustion. RESULTS: No differences in breathing frequency and inspiratory time/total time ratio (Ti/Ttot) were found after detraining (P>0.05). Differences in tidal volume (VT), VT/Ti quotient and VE were significant (P<0.05) at between 40 to 100% of exercise intensity. The VE/VCO2 slope did not change (P>0.05) during a postdetraining maximal incremental test. CONCLUSIONS: A six-week detraining period causes changes in inspiratory flow but does not affect the inspiratory time/total respiratory cycle time ratio. The overall ventilatory efficiency of the respiratory system remains constant and is not affected by detraining.

Cortisol awakening response and emotion at extreme altitudes on Mount Kangchenjunga.

The cortisol awakening response (CAR) was examined over a 45days stay at extreme altitudes (above of about 5500m) on Mount Kangchenjunga. The CAR refers to a peak cortisol response during the waking period that is superimposed to the diurnal rhythmicity in cortisol secretion, whose function has been proposed to be the anticipation of demands of the upcoming day (the CAR anticipation hypothesis). According to this hypothesis, we distinguished between resting days on which the expedition team engaged in routine activities in the base camp, and ascent days on which it planned to climb up a very demanding track. We were also interested in examining the association of testosterone with emotional anticipation, given the role of this steroid hormone in reward-related processes in challenge situations. Results showed that the climber group had a bigger CAR on ascent days, relative to the Sherpa group at the same altitude and the non-climber group at sea level. Several methodological issues, however, made it difficult to interpret these group differences in terms of the CAR anticipation hypothesis (e.g. a seemingly influential covariate was awakening time). Although based on tentative results, correlational and regression analyses controlling for awakening time coherently showed that the CAR was associated with anticipation of a hard day and feelings of fear, and testosterone was associated with feelings of energy and positive affect. Whether or not the anticipation of a hard day played a key role in regulation of the CAR, the observation of an intact CAR in the climber group under hypobaric hypoxia conditions would require in-depth reflection from the perspective of human adaptive evolution.

Testosterone, cortisol and anxiety in elite field hockey players.

The aim of the present study was to assess the change in the levels of testosterone and cortisol after victory and defeat in male field hockey players during an important tournament. In the beginning of the game series, the players were ranked very closely to achieve (for the first time) the championship rising to The Honor Division-A, the highest status national category. The first game resulted in a 7-4 victory, the second game resulted in a 6-1 victory, and the third game resulted in a 1-2 defeat. As expected, there were changes in testosterone levels after the competition, dropping in the game which ended in defeat, and rising slightly in the two games which ended in victory; there were also changes in cortisol levels, rising in the game which ended in defeat, and showing no variations in the games which ended in victory; correlational analyses congruently showed that defeat led to rises in cortisol whereas victory led to rises in testosterone; anticipatory somatic anxiety was related to cortisol levels prior to games, and physical exertion during competition was related to the change in testosterone levels (suggesting an inhibitory effect) but not to the change in cortisol levels. Hence, this pattern of hormonal responses to a real-life dominance challenge complied with Mazur's (1985) [16] biosocial model of status and dominance motivation, by showing that testosterone and cortisol are linked to victory and defeat in a theoretically predictable fashion.

Effects of victory and defeat on testosterone and cortisol response to competition: evidence for same response patterns in men and women.

In this study, we report evidence from sport competition that is consistent with the biosocial model of status and dominance. Results show that testosterone levels rise and drop following victory and defeat in badminton players of both sexes, although at lower circulating levels in women. After losing the match, peak cortisol levels are observed in both sexes and correlational analyses indicate that defeat leads to rises in cortisol as well as to drops in testosterone, the percent change in hormone levels being almost identical in both sexes. In conclusion, results show the same pattern of hormonal responses to victory and defeat in men and women.

Métodos de evaluación de la composición corporal: tendencias actuales (III) / Body composition assessment methods: actual trends (III)

Se abordan aspectos sobre la valoración de los diferentes métodos de laboratorio y de campo utilizados en estudios de investigación, en clínica y en el campo de la salud, para la obtención de medidas válidas de composición corporal y se establecen recomendaciones sobre métodos específicos y ecuaciones de predicción. Así mismo se analiza el estado actual acerca de la evaluación de la composición corporal, sujeta a las modificaciones constantes de los nuevos métodos así como las nuevas tecnologías que pueden estar disponibles en un futuro. La densitometría (hidrodensitometría y pletismografía por desplazamiento de aire), la hidrometría, y el DEXA (dual-energy x-ray absorptiometry) son las técnicas comúnmente más utilizadas y validadas para obtener medidas de referencia en composición corporal y en investigación, por la mayoría de autores.No obstante como estos métodos de referencia aportan medidas por métodos indirectos de composición del cuerpo, se podría afirmar que ninguno de ellos es el "mejor de referencia" para la evaluación de la composición del cuerpo "in vivo". Las variables obtenidas con los tres métodos anteriores, pueden ser usados como forma de estimación multicomponente, para derivar medidas de referencias de composición corporal en investigación, desarrollo y aprobación de métodos de campo y ecuaciones de predicción.Por otra parte los métodos como el análisis por impedancia bioeléctrica (BIA), los pliegues cutáneos de grasa y los métodos antropométricos, que son extensamente utilizados para la estimación de la composición corporal, en el campo de la condición física-salud. La exactitud predictiva de estos métodos de campo y sus ecuaciones de predicción son aceptables, pero limitadas a las diferencias por sexo, etnia, edad y otros factores, por la ausencia de un único método de referencia. Una gran cantidad de ecuaciones de predicción para la evaluación por métodos de campo, han sido desarrolladas y validadas usando el modelo clásico de composición corporal de dos componentes conjuntamente con un método de referencia. Por eso, el error de predicción de la estimación de la composición corporal que se obtuvo con estas ecuaciones puede ser mayor de lo esperado y sobre todo si la densidad de la masa libre de grasa del individuo difiere en gran medida del valor asumido por el modelo de los dos componentes. Con estas precauciones se hacen en este trabajo recomendaciones con respecto a la selección de métodos y ecuaciones para su uso en grupos diversos de población

This review artic1e focuses on severallaboratory and field methods used in research studies, clinical practice and other health areas to obtain valid body composition values and suggest recommendations about specific methods and prediction equations. Also current body composition background is up to date in both aspects, new ca1culation methods and new technologies that can be available in a near future. Densitometry (hidrodensitometry and air displacement plethismography), Hidrometry and DEXA (dual-energy x-ray absorptiometry) are methods commonly used and validated in order to have body composition reference values and in research on a majority of authors. Nevertheless this reference methods shows indirect values of body composition, we could conc1ude that any one of them is the "Gold Standard" for "In Vivo" determination of body composition. Variables obtained with, the three mentioned methods, could be used to estimate measures in a multicomponent model, in order to have reference values in body composition in research, develop and validation of field methods and prediction equations. On the other hand, bioe1ectrical impedance analysis (BIA), skinfolds and anthropometric methods, are widely used in fitness area in order to estimate body composition. Predictive accuracy of this field methods an its prediction equations are acceptable, but limited by the differences by sex, race, age and other factors, by lack of a only one reference method. A lot of predictive equations for predictive estimation by field method, have been developed and validated using the two component body composition c1assic model jointly with a reference method. Thus, the prediction errors of body composition estimation obtained with this equations could be greater than expected specially if fat free mass d~nsity of subjects have a great difference with the assumed value by the two components model. Whith the mentioned cautions, there are suggested in this artide recommendations about selecting methods and equations to be used in diverse population groups

Métodos de evaluación de la composición corporal: tendencias actuales (II) / Body composition assessment methods: actual trends (II)

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