Birth sex ratio in the offspring of professional male soccer players: influence of exercise training load.

STUDY QUESTION: Can the exercise training load of elite male athletes influence the sex ratio of their offspring? SUMMARY ANSWER: This is the first study assessing the influence of exercise training load on the offspring sex ratio of children from male professional athletes, observing a bias toward more females being born as a result of both high-intensity and high-volume loads, with intensity having the greatest effect. WHAT IS KNOWN ALREADY: There is a relatively constant population sex ratio of males to females among various species; however, certain events and circumstances may alter this population sex ratio favoring one sex over the other. STUDY DESIGN, SIZE, DURATION: Observational, descriptive cross-sectional study with a duration of 3 months. PARTICIPANTS/MATERIALS, SETTING, METHODS: Seventy-five male professional soccer players from First Division soccer teams. Offspring variables were sex of the offspring, number of children and order of birth. Exercise training variables were volume and intensity. MAIN RESULTS AND THE ROLE OF CHANCE: Total offspring was 122 children (52 males (42.6%), 70 females (57.4%)). Analysis revealed that increase in either the volume (P < 0.001) or intensity (P < 0.001) of training by the players shifted the birth offspring ratio more toward females. Within the sample of females born, more births (i.e. number) were observed as a consequence of training at the highest intensity (45 out of 70; P < 0.001), no such pattern occurred within males (P > 0.05). When female versus male births were compared within each intensity, only the high-intensity comparison was significant (45 (75%) females vs 15 (25%) males, P < 0.001). LIMITATIONS, REASONS FOR CAUTION: While this is the first study assessing differences in the sex ratio of the offspring of male athletes (i.e. soccer players), we acknowledge there are limitations and confounders within our approach; e.g. small sample size, ethnic background and variations in the timing of intercourse relative to ovulation as well as in sex hormone levels. As such, we propose that future research is needed to confirm or refute our findings. It is recommended that such work expand on the measurements obtained and conduct direct assessment of sperm characteristics. WIDER IMPLICATIONS OF THE FINDINGS: The findings of the study support the fact that different stressors on the body may alter the sex of the offspring. While in the present study the stressor is the excessive training load of soccer players, other events may lead to similar results. The bias in offspring sex ratio may have important implications for demography and population dynamics, as well as genetic trait inheritance. STUDY FUNDING/COMPETING INTEREST(S): There is no funding nor competing interests. TRIAL REGISTRATION NUMBER: N/A.

Sperm DNA fragmentation as a result of ultra-endurance exercise training in male athletes.

Intensive sports practice seems to exert negative effects on semen parameters; in order to assess these effects, the objective of this study was to assess semen, including DNA fragmentation, and hormone parameters in elite triathletes. Twelve high-level triathletes preparing for a National Triathlon Championship participated in the study. The qualitative sperm parameters analysed were volume, sperm count, motility, morphology and DNA fragmentation; when needed, additional testing was performed. Assessed hormones were testosterone (T), cortisol (C) and testosterone-cortisol ratio (T/C). Maximum oxygen consumption and training characteristics were also assessed. Hormonal values and physical semen parameters were within normal ranges. DNA fragmentation showed high values (20.4 ± 6.1%). Round cells in semen were higher than normal (2.8 ± 1.5 million/ml), with the presence of macrophages. Correlations were found for several parameters: concentration of round cells positively correlated with progressive sperm motility (p = .01) and sperm morphology (p = .02); contrarily, the correlation found with DNA fragmentation was negative (p = .04). Sperm DNA fragmentation and the T/C ratio, however, were correlated in a positive manner (p = .03). As evidenced by the observed results, sperm DNA fragmentation is affected by high-level sports practice; therefore, high loads of endurance training could potentially interfere with the athlete's fertility potential.

The limitations of scaling laws in the prediction of performance in endurance events.

In the twentieth century, scientists have examined running speed over various distances, analyzing world records and studying the ability of an athlete to sustain a given speed. Assuming that running speed expresses the response of a non-linear multisystemic behavior, the relationship between these two variables (distance vs. velocity) can therefore be evaluated by applying scaling laws that fulfill the key principles of specificity and individuality of each athlete, yet responding to bioenergetic and functional patterns that are well-known to sports physiology. Since speed loss as distance increases exhibits fractal behavior, with small changes in the speed-reduction curve due to the effect of fatigue, it must be recognized that no universal scaling law can account, with acceptable precision, for the effect exerted by fatigue on potential speed at any given moment in a race. Power laws using a range of scaling exponents provide technical staff and athletes with a reliable, non-invasive tool for planning of training schedules, predicting athletes' performances over various distances and comparing the performance of specialists in different track events. The equations for the scaling laws for the distances investigated here were: V1500=15.00 × D⁻°·¹° (R²=0.99); V3000=12.76 × D⁻°·°8 (R²=0.99); V5000=11.55 × D⁻°·°7 (R²=0.99); V10,000=11.59 × D⁻°·°7 (R²=0.99); V21,095=10.78 × D⁻°·°6 (R²=0.97); V42,175=10.27 × D⁻°·°57 (R²=0.99).

Echocardiographic study of structure and functional cardiac profile of football referees.

AIM: The aim of this study was to analyze, through echocardiography, the structure and functional cardiac profile of national category Spanish soccer referees. METHODS: The sample consisted of 54 licensed referees, who belonged to the Football Inter-Insular Federation of Las Palmas. The sample presented a mean age of 28.52 ± 6.39 years, a height of 1.76 ± 0.07 m, a body mass of 77.26 ± 10.74 kg and a Body Mass Index of 24.90 ± 2-73 kg/m2. The diastolic and systolic dimensions of the left ventricle were 50.03 ± 4.79 mm and 33.74 ± 5.23 mm, respectively. The thicknesses of the interventricular septum and the posterior wall of the left ventricle were 9.77 ± 1.53 mm and 9.47 ± 1.54 mm, respectively. The left ventricular mass was 112.80 ± 26.53 g/m2, the diastolic volume of the left ventricle 135.09 ± 39.63 mL and the ejected volume 47.34 ± 12.44 mL/m2. RESULTS: This study shows that the echocardiographic profile of football referees is characterized by presenting an increase in the left ventricular mass caused by an increase of the cardiac chambers and a normal systolic and diastolic function. The values obtained by football referees were higher than those found in sedentary people and lower than in professional football players. CONCLUSION: These differences may be due to the different physical training workloads employed by football players and referees.

Male powerlifting performance described from the viewpoint of complex systems.

This paper reflects on the factors that condition performance in powerlifting and proposes that the result-generating process is inadequately described by the allometric equations commonly used. We analysed the scores of 1812 lifters belonging to all body mass categories, and analysed the changes in the results achieved in each weight category and by each competitor. Current performance-predicting methods take into account biological variables, paying no heed to other competition features. Performance in male powerlifting (as in other strength sports) behaves as a self-organised system with non-linear interactions between its components. Thus, multiple internal and external elements must condition changes in a competitor's score, the most important being body mass, body size, the number of practitioners, and the concurrency of favourable factors in one individual. It was observed that each behaved in a specific form in the high level, according to the individuals' circumstances, which make up the main elements of the competitive system in every category. In powerlifting, official weight categories are generally organised in three different groups: light (<52.0 to <60 kg), medium (<67.5 to <90.0 kg) and heavy (<100 to >125 kg) lifter categories, each one of them with specific allometric exponents. The exponent should be revised periodically, especially with regard to the internal dynamics of the category, and adjusted according to possible changes affecting competition.

Applying graphs and complex networks to football metric interpretation.

This work presents a methodology for analysing the interactions between players in a football team, from the point of view of graph theory and complex networks. We model the complex network of passing interactions between players of a same team in 32 official matches of the Liga de Fútbol Profesional (Spain), using a passing/reception graph. This methodology allows us to understand the play structure of the team, by analysing the offensive phases of game-play. We utilise two different strategies for characterising the contribution of the players to the team: the clustering coefficient, and centrality metrics (closeness and betweenness). We show the application of this methodology by analyzing the performance of a professional Spanish team according to these metrics and the distribution of passing/reception in the field. Keeping in mind the dynamic nature of collective sports, in the future we will incorporate metrics which allows us to analyse the performance of the team also according to the circumstances of game-play and to different contextual variables such as, the utilisation of the field space, the time, and the ball, according to specific tactical situations.

Impact of physical activity and exercise on male reproductive potential: a new assessment questionnaire.

Male athletes in general are subjected to the same causes of infertility as the general population, but sports practice itself may be possibly an additional infertility factor or, at least an aggravating factor for a previously existing fertility condition; on the contrary, being physically active has been hypothesized to favor hormonal and seminological processes and could be beneficial for fertility. In this relationship, the different inherent parameters of physical activity-exercise (training volume, intensity, objective, organization and frequency) are of paramount importance. Therefore, this review discusses both the negative and positive impact of physical exercise on the male reproductive potential. Clear knowledge is lacking on this topic as incongruences exist due to the fact that studies lack standardization in assessment tools or research protocols. So that future studies can reveal more information regarding exercising male fertility, we introduce a unique questionnaire developed with the intent to help standardize future studies on male fertility and exercise.