Blood rheology and body composition as determinants of exercise performance in female rugby players.

Athletes involved in rugby are characterized by a very specific pattern of body composition with an unusually important muscle mass. In a preceding study about rugbymen we evidenced that they exhibit a correlation between red blood cell aggregability and the amount of body fat although it remains within a normal range, and that red cell rigidity was correlated to isometric adductor strength. We had the opportunity of studying the relationships among exercise performance, body composition and hemorheology in 19 female rugby players (age 19-26, mean: 24.47 ± 0.67 yr) practising 4 - 10 hr/wk (mean 7.15 ± 0.3) since 1-12 yr (mean 4,05 ± 0,694). VO2max was not related by its own to blood rheology, either hematocrit (r = -0.0717 p = 0.7706) or plasma viscosity (r = 0.0144; p = 0.9533), but other markers of performance exhivited a correlation with red cell rheology. Relationships between fitness and body composition were evidenced. Isometric handgrip strength was negatively correlated to red blood cell aggregability (Myrenne M, r = -0.57839; p = 0.00948 M1 r = -0.58910; p = 0.00795). Adductor isometric strength was negatively correlated to red blood cell aggregability Myrenne M (r = -0.5033; p = 0.0280) but not to M1 (r = -0.4227; p = 0.0714). Fat mass is a major determinant of the maximal oxygen consumption VO2max either measured by a field test (r = -0.766; p = 0.00013) or exercise test (r = -0.575; p = 0.00994) and was also negatively correlated to both handgrip (r = -0.4918; p = 0.0325) and RBC aggregability M (r = -0.57839; p = 0.00948 and M1 r = -0.5891; p = 0.00795). Independently of fat mass, FFM appears to be a determinant of blood viscosity (r = 0.4622; p = 0.0463) due to its correlation with RBC rigidity (r = 0.4781; p = 0.0384). Thus, trained young women exercising 4-10 hr/wk and thus exhibiting a low percentage of body fat exhibit clear relationships between body composition and hemorheology, but fat mass being low, the parameter correlated with blood rheology is in this case fat-free mass, consistent with recent findings indicating that high fat mass in women is sometimes correlated with parameters of the metabolic syndrome such as insulin resistance or inflammation. In addition, parameters quantifying fatness even within such a physiological range are in this sample negatively related with exercise performance.

Effects of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool.

The aim of our study was to determine the impact of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool. An indoor swimming pool was equipped with two medium-pressure UV lamps. We collected eight samples of water daily over a four-weeks period and measured total and free chlorine, pH, water temperature, bacteriological parameters, total organic carbon and trihalomethanes. During the first week, which served as control, medium-pressure UV lamps were turned off. During the next three weeks, medium-pressure UV lamps were kept on 24 h per day. The third week, we reduced the level of the injected chlorine into water, and the last week we also reduced the water renewal volume by 27%. Our results showed that bacteriological parameters remained within allowable french limits. When medium-pressure UV lamps were kept on, total, free and active chlorine levels were significantly increased (P<0.001), whereas combined chlorine level were significantly decreased (P<0.001 and P<0.05, respectively). The levels of chloroform and bromodichloromethane were significantly increased when medium-pressure UV lamps were kept on (P<0.001), whereas chlorodibromomethane and bromoform levels significantly decreased (P<0.05 and P<0.001, respectively). The additional formation of chloroform and bromodichloromethane may be explained by the increase in active chlorine and by radicalizing mechanisms initiated by UV radiation.

Contributions of social influences and psychopathological factors to cannabis use and dependence in high-school students.

OBJECTIVES: To evaluate the relative contributions of peers cannabis use or non use, parental approval of such use, adolescents' own beliefs about use, self-esteem, and depressive and symptoms of borderline personality disorder, in the prediction of cannabis use and dependence. METHOD: Participants were 257 high-school students who completed questionnaires assessing cannabis use frequency, cannabis dependence, the number of peers using cannabis, the number of peers opposed to cannabis use, parental attitude toward cannabis use, participants' attitude toward use, self-esteem, depressive and borderline symptomatology. Logistic regression analyses were conducted to predict cannabis use, daily use and dependence. RESULTS: The number of peers using cannabis, participants' approval of cannabis use, and the intensity of symptoms of borderline personality disorder were risk factors for use whereas the number of peers opposed to cannabis use was a protective factor. Parental attitudes toward use and participants' depressive symptomatology were not significant independent predictors of use. There were no significant predictors of probable cannabis dependence. CONCLUSION: To inform adolescents that a significant proportion of them disapprove of cannabis use may be an effective component of prevention of use. Symptoms of borderline personality disorder may account for the association between depression and cannabis use. The social influences and psychopathological factors evaluated in this study did not appear to play a major role in the development of cannabis dependence.

Blood fluidity is related to the ability to oxidize lipids at exercise.

We previously reported in rugbywomen correlations between RBC deformability and the ability to oxidize at exercise more lipids. This surprising finding might of course be spurious, or reflect the importance of the balance of substrates at exercise on baseline parameters that regulate blood rheology. Actually, the capacity of skeletal muscle to utilize either lipid or carbohydrate as fuels strongly influences whole body metabolism both at rest and during exercise. While the healthy skeletal muscle has substantial metabolic flexibility and is able to switch from predominantly lipid o oxidation during fasting or endurance exercise to increased glucose oxidation in conditions of insulin stimulation, obese individuals and those with type 2 diabetes manifest higher lipid oxidation during insulin-stimulated conditions despite lower rates of lipid oxidation during fasting or prolonged exercise. A low ability to oxidize and to periodically deplete triglyceride in muscle is associated with raised blood lipids. In addition, high carbohydrate oxidation rates in the mitochondrion are likely to promote more free radical generation. An increase in either blood lipids or free radicals is likely to induce profound hemorheological effects. We present here hemorheological studies in various populations with the use of exercise calorimetry in order to assess this switch of substrates. These studies further evidence negative correlations between the ability to oxidize lipids at exercise and parameters of blood viscosity. Correlations found between RBC deformability and the ability to oxidize at exercise more lipids may be due to effects of endurance training on lipid oxidation which may in turn modify both lipid metabolism and free radical generation, thus influencing RBC rheology.