Diurnal variations of postural stability and attentional capacities in 5–6-year-old tennis players

The present study aimed to investigate the diurnal variation of postural stability, attentional capacities, and oral temperature in 5–6-year-old tennis players. A total of 24 young children were divided into two groups: Twelve tennis players with 2 years of training experience and twelve sedentary children without previous experience in any type of sport. They were asked to maintain an upright bipedal stance on a static force platform with eyes open (EO) and eyes closed (EC) at 07:00, 10:00, 14:00, and 18:00 h. Postural stability was evaluated by the center of pressure (CoP), surface area (CoP_Area), CoP mean velocity (CoP_Vm), and Romberg’s index (RI). Oral temperature and simple reaction time (SRT) were also recorded at the beginning of each test session. Postural stability in 5–6-year-old tennis players was low at 07:00 h and improved at 10:00 h (p < 0.001); then, it worsened at 14:00 h (p < 0.001) and improved again at 18:00 h (p < 0.001) as found in sedentary children. This rhythm was also close to that of SRT in both groups. Body temperature increased significantly (p < 0.001) from the morning to the afternoon in both groups. However, the peak of postural performance, the peak of attentional capacities, and the greatest vision contribution to maintain balance observed at 18:00 h were only found in the trained group. Moreover, young tennis players were more stable (p < 0.001) and more attentive (p < 0.01) than sedentary ones at 18:00 h. The amplitude of the diurnal rhythm of CoP parameters was significantly larger (p < 0.01) in trained children compared to sedentary ones (43.1 ± 8.5 vs 31.7 ± 8.3 for the CoP_Area; 27.5 ± 7.4 vs 17.7 ± 8.2 for the CoP_Vm). Therefore, time-of-day has a significant effect on static postural stability and attentional capacities in young tennis players with better performances in the late afternoon (habitual hour of training). Thus, we recommend planning some training sessions at 07:00 and/or 14:00 h to optimize postural stability at the time of its batyphase and to reduce the incidence of fall-related injury risks during this critical age in athletic environments.     

Is Sp1 binding site polymorphism within COL1A1 gene associated with tennis elbow?

Tennis elbow defines a condition of pain and tenderness over the lateral epicondyle of the humerus. The exact aetiology of the injury is not yet fully understood. The major constituent of tendons is type 1 collagen which is encoded by COL1A1 gene. The aim of the study was to determine whether Sp1 binding site polymorphism (SNP rs1800012; 1546G/T) within the intronic region of COL1A1 gene is associated with tennis elbow. One hundred and three tennis elbow patients and one hundred and three healthy subjects without any history of previous ligament or tendon injuries were recruited for this genetic association study. All participants were genotyped for the COL1A1 Sp1 binding site polymorphism by using PCR–RFLP method. There were no observed statistical differences in the genotype (p = 0.17) or allele (p = 0.11) distributions between the groups. G allele frequency in patients and controls was 82.5% and 76.21%, and T allele frequency was 17.5% and 23.79% respectively. This study has shown that there is no association between this polymorphism and tennis elbow within the population studied.     

The food niches of the invasive Dugesia tigrina (Girard) and indigenous Polycelis tennis Ijima and P. nigra (Müller) (Turbellaria; Tricladida) in a Welsh lake

The invasion of Llyn Coron in North Wales by the American immigrant Dugesia tigrina resulted in the almost entire displacement of the native Polycelis tenuis and P. nigra populations. Because competition for food is the most important factor controlling and regulating populations of British lake-dwelling triclads, the diets of the invasive and native triclads in the lake were examined in an attempt to explain the successful invasion.A serological technique, the precipitin test, identified the gut contents of field-collected triclads. Niche breadth, electivity and niche overlap indices were used in analysis of the data. A broad food niche was recorded for all the triclad species. Oligochaetes predominated in the diet of D. tigrina followed by Asellus and chironomids, in almost equal proportions, snails and caddisflies, with mayflies scarcely eaten. Both Polycelis species fed heavily on oligochaetes followed by Asellus. P. tenuis ate slightly higher proportions of chironomids and caddisflies than snails and mayflies, whilst P. nigra consumed similar proportions of these four prey taxa. Gammarus, scarce in Llyn Coron, and cladocerans were not eaten by the Polycelis species and by only a few D. tigrina.To-date there has been no apparent shift in the diet of the Polycelis species as a consequence of the invasion by D. tigrina. In the absence of any evidence for the partitioning of food on the basis of prey size or condition, the considerable overlap in the diets of D. tigrina and the Polycelis species suggests the potential for severe inter-specific competition for food. The superior exploitation by D. tigrina of the available food resource requires explanation.