Monitoring training loads, stress, immune-endocrine responses and performance in tennis players

The study aim was to investigate the effect of a periodised pre-season training plan on internal training load and subsequent stress tolerance, immune-endocrine responses and physical performance in tennis players. Well-trained young tennis players (n = 10) were monitored across the pre-season period, which was divided into 4 weeks of progressive overloading training and a 1-week tapering period. Weekly measures of internal training load, training monotony and stress tolerance (sources and symptoms of stress) were taken, along with salivary testosterone, cortisol and immunoglobulin A. One repetition maximum strength, running endurance, jump height and agility were assessed before and after training. The periodised training plan led to significant weekly changes in training loads (i.e. increasing in weeks 3 and 4, decreasing in week 5) and posttraining improvements in strength, endurance and agility (P \u3c 0.05). Cortisol concentration and the symptoms of stress also increased in weeks 3 and/or 4, before returning to baseline in week 5 (P \u3c 0.05). Conversely, the testosterone to cortisol ratio decreased in weeks 3 and 4, before returning to baseline in week 5 (P \u3c 0.05). In conclusion, the training plan evoked adaptive changes in stress tolerance and hormonal responses, which may have mediated the improvements in physical performance

Relative Growth Of Carcass Tissues Of Goat Kids From Five Breed Types Finished On Pasture Or Feedlot

The aim of this study was to evaluate the effect of cross breeding, finishing system, and gender on the relative growth of carcass tissues of dairy kids. Seventy eight kids (39 male and 39 female) from five breed types were used: Alpine; 1/2 Boer + 1/2 Alpine (1/2 BA); 1/2 Nubian + 1/2 Alpine (1/2 ANA); 3/4 Boer + 1/4 Alpine (3/4 BA); and 1/2 Nubian + 1/4 Boer + 1/4 Alpine (TC). Kids were distributed into two finishing systems: in pasture with doe (FS1) and weaned in feedlot (FS2). Kids were slaughtered at a mean age of 128.4 ± 7.9 days and mean live weight of 22.07 kg. The mean weight of half carcasses was 5.09 kg. To determine allometric growth, we used the exponential equation Y= aXb. In the half carcass, muscle tissue showed comparatively early growth in group 1/2 BA, whereas fat tissue of animals in FS1 had relatively late growth. Females exhibited early growth of muscle tissue, while in males this tissue was intermediate. The 1/2 BA first-cross improved carcass characteristics by enhancing the growth of muscle tissue.37298999

On the dynamics of Extrasolar Planetary Systems under dissipation. Migration of planets

We study the dynamics of planetary systems with two planets moving in the same plane, when frictional forces act on the two planets, in addition to the gravitational forces. The model of the general three-body problem is used. Different laws of friction are considered. The topology of the phase space is essential in understanding the evolution of the system. The topology is determined by the families of stable and unstable periodic orbits, both symmetric and non symmetric. It is along the stable families, or close to them, that the planets migrate when dissipative forces act. At the critical points where the stability along the family changes, there is a bifurcation of a new family of stable periodic orbits and the migration process changes route and follows the new stable family up to large eccentricities or to a chaotic region. We consider both resonant and non resonant planetary systems. The 2/1, 3/1 and 3/2 resonances are studied. The migration to larger or smaller eccentricities depends on the particular law of friction. Also, in some cases the semimajor axes increase and in other cases they are stabilized. For particular laws of friction and for special values of the parameters of the frictional forces, it is possible to have partially stationary solutions, where the eccentricities and the semimajor axes are fixed.Comment: Accepted in Celestial Mechanics and Dynamical Astronom