Plasma visfatin and adiponectin concentrations in physically active adolescent girls: relationships with insulin sensitivity and body composition variables

The purpose of this study was to evaluate the associations of visfatin and adiponectin concentrations with insulin resistance and body composition in regularly physically active pubertal girls . In 129 girls, aged 13-15 years (pubertal stages 3-5), visfatin, adiponectin, insulin resistance measured with homeostasis model assessment (HOMA) and body composition measured with dual-x ray absorptiometry were evaluated. Visfatin concentration was related to HOMA and overall adiposity (body mass index, fat mass) markers, whereas adiponectin concentration was related to overall adiposity (fat mass), central adiposity (trunk fat) and fat free mass values. These relationships remained significant (p >0.05) after adjusting for pubertal stage. Visfatin was independently related to body mass index (beta=0.936, p=0.0001) and HOMA (beta=0.444, p=0.039) indices, whereas adiponectin was indipendently related to fat free mass (beta=0.468;P=0.042) values. In conclusion visfatin could be related to insulin resistance and overall adiposity indices, whereas adiponectin was related to different body composition values in regularly physically active puberal girls

Reactive oxygen species and male reproductive hormones

Reports of the increasing incidence of male infertility paired with decreasing semen quality have triggered studies on the effects of lifestyle and environmental factors on the male reproductive potential. There are numerous exogenous and endogenous factors that are able to induce excessive production of reactive oxygen species (ROS) beyond that of cellular antioxidant capacity, thus causing oxidative stress. In turn, oxidative stress negatively affects male reproductive functions and may induce infertility either directly or indirectly by affecting the hypothalamus-pituitary-gonadal (HPG) axis and/or disrupting its crosstalk with other hormonal axes. This review discusses the important exogenous and endogenous factors leading to the generation of ROS in different parts of the male reproductive tract. It also highlights the negative impact of oxidative stress on the regulation and cross-talk between the reproductive hormones. It further describes the mechanism of ROS-induced derangement of male reproductive hormonal profiles that could ultimately lead to male infertility. An understanding of the disruptive effects of ROS on male reproductive hormones would encourage further investigations directed towards the prevention of ROS-mediated hormonal imbalances, which in turn could help in the management of male infertility

Leptin responses to short term exercise in college level male rowers

Objective: To investigate plasma leptin response to short term exercise in college level male rowers. Methods: Thirteen rowers performed a 30 minute maximal rowing ergometer test. Venous blood samples were obtained before, immediately after, and after 30 minutes of recovery. Concentrations of leptin, insulin, growth hormone, insulin-like growth factor-I (IGF-I), and IGF binding protein-3 (IGFBP-3) were measured. Results: Plasma leptin was significantly (p<0.05) decreased (from a mean (SD) of 2.7 (0.6) to 2.1 (0.8) ng/ml) and growth hormone significantly increased (from 0.6 (0.9) to 4.6 (5.4) µIU/l) immediately after the 30 minute maximal rowing exercise session (distance covered 7870.4 (443.3) m; blood lactate immediately after the test 14.9 (4.3) mmol/l). All other blood variables measured were not significantly changed as a result of the ergometer test. A positive relation was observed between the decreased plasma leptin concentration immediately after the test and the distance covered (R(2) = 0.645; p<0.05). Changes in leptin and IGF-I concentrations immediately after the test were also related (R(2) = 0.390; p<0.05). Percentage body fat explained 89.6% (p<0.05) of the variance (R(2) x 100) in basal leptin concentration. After normalisation for body fat, basal leptin was related (p<0.05) to basal insulin (r = 0.82) and training history (r = –0.60). Conclusion: Leptin is sensitive to relatively short term intense exercise when all major muscles are involved

Relationship of leptin with body dimensions in normal, overweight and obese adolescents

The relationships of leptin with different anthropometric parameters, in normal, overweight and obese peripubertal boys, is not completely understood. Aim of the present investigation is to assess possible relationships of leptin with skinfolds thicknesses, and body segments in different BMI groups of prepubertal boys (Tanner). Methods. A sample of 248 boys (age 10-12 y) were divided (Cole et al. 2000) into three BMI subgroups: normal weight, n=190 (BMI<19.8-21.9); overweight, n=34 (BMI<24.0-26.8) and obese, n=24 (BMI 6524.0-26.8). 9 skinfolds and 13 circumferences were measured and the waist-to-hip ratio was calculated (tab.1). A 10 ml blood sample was obtained from the antecubital vein with the participant sitting in an upright position in the morning (8-9 a.m.) after an overnight fast. Leptin concentrations were determined by mean of an immunoassay ELISA sandwich method

ELECTROMYOGRAPHIC AND NEUROMUSCULAR FATIGUE THRESHOLDS AS CONCEPTS OF FATIGUE IN ROWERS

Objectives: To investigate the concepts of electromyographic threshold (EMGT) by iEMG signals and neuromuscular fatigue threshold concepts in trained male athletes. Methods: Nine competitive national level male rowers (21.8\ub14.4 years; 186.2\ub14.6 cm; 79.6\ub18.4 kg) took part in this investigation. Subjects were asked to participate in the graded exercise test to volitional exhaustion and 500m, 1000m, and 2000m all-out rowing ergometer tests on rowing ergometer. During the all tests oxygen consumption parameters, average power and integrated EMG of the musculus vastus lateralis was recorded. Results: The ventilatory threshold (VT) (248.9\ub126.67 W) and EMG threshold (258.89\ub127.13 W) were not significantly different but were significantly (p0.05). However, no relationship was detected between NMFT and VT and EMGT parameters, while significant relationship was found in VT and EMGT. All measured threshold values were significantly correlated (r>0.70; p<0.05) to the rowing ergometer performance characteristics. Conclusions: EMGT is closely related to aerobic-anaerobic transition phase as NMFT represents the local fatigue accumulation in the muscl

Longitudinal development of physical and performance parameters during biological maturation of young male swimmers

The aim of the study was to examine the development of specific physical, physiological, and biomechanical parameters in 29 young male swimmers for whom measurements were made three time for two consecutive years. During the 400-m front crawl swimming, the energy cost of swimming, and stroking parameters were assessed. Peak oxygen consumption (VO2 peak) was assessed by means of the backward-extrapolation technique recording VO2 during the first 20 sec. of recovery period after a maximal trial of a 400 m distance. Swimming performance at different points of physical maturity was mainly related to the increases in body height and arm-span values from physical parameters, improvement of VO2 peak value from physiological characteristics, and improvement in stroke indices on biomechanical parameters. In addition, biomechanical factors characterized best the 400 m swimming performance followed by physical and physiological factors during the 2-yr. study period for the young male swimmers

Physical development and swimming performance during biological maturation in young female swimmers

The present study analyzed the development of physiological, biomechanical and anthropometrical parameters in young female swimmers and assessed the effect of these parameters on swimming performance during biological maturation. In total, 26 female swimmers participated in the study in which data were annually collected for two consecutive years. Body composition, basic anthropometrical parameters and biological age were measured. During the 400 m front-crawl swimming, the energy cost of swimming and stroking parameters were assessed. Peak oxygen consumption (VO2 peak) was assessed by means of the backward-extrapolation technique recording VO2 during the first 20 sec of the recovery period after a maximal trial of 400 m distance. During the 2 year follow-up study period, age, height, body mass, body fat %, fat free mass, bone mineral mass, total bone mineral density, arm span and biological maturation values significantly increased during each year (p&lt;0.05). The tracking of the physical characteristics measured over the 2-years study period was relatevely high (r > 0,694), except for the body fat% (r>0.554). The tracking of the Tanner stages was also high (r = 0.759-0.780). Stepwise regression analyses showed that biomechanical factors (R2 > 0.322;p&lt;0.05) best characterized the 400 m swimming performance in young female swimmers, followed by bioenergetical (R2 > 0.311; p&lt; 0.05) and physical (R2>0.203;p&lt;0.05) factors during all three measurement times