The aims of this study were to measure the aerodynamic drag in professional cyclists, to obtain aerodynamic drag reference values in static and effort positions, to improve the cyclists' aerodynamic drag by modifying their position and cycle equipment, and to evaluate the advantages and disadvantages of these modifications. The study was performed in a wind tunnel with five professional cyclists. Four positions were assessed with a time-trial bike and one position with a standard racing bike. In all positions, aerodynamic drag and kinematic variables were recorded. The drag area for the time-trial bike was 31% higher in the effort than static position, and lower than for the standard racing bike. Changes in the cyclists' position decreased the aerodynamic drag by 14%. The aero-helmet was not favourable for all cyclists. The reliability of aerodynamic drag measures in the wind tunnel was high (r > 0.96, coefficient of variation < 2%). In conclusion, we measured and improved the aerodynamic drag in professional cyclists. Our results were better than those of other researchers who did not assess aerodynamic drag during effort at race pace and who employed different wheels. The efficiency of the aero-helmet, and the validity, reliability, and sensitivity of the wind tunnel and aerodynamic field testing were addressed.

The functional integrity of the beta- and alpha-adrenergic stimulatory pathways in a rapid ventricular pacing model of congestive heart failure in dogs was investigated; normal dogs served as controls. Total beta-adrenergic receptor density was 35% lower (p less than 0.01) in the pacing-overdrive dogs, and the beta-adrenergic receptor-mediated stimulation of adenylate cyclase (Vmax) was found to be 68% and 72% lower (p less than 0.01) in the left and right ventricles of the paced dogs. In addition, the basal adenylate cyclase activity was found to be 56% and 68% lower (p less than 0.01) in the left and right ventricles of the failing heart. Similarly, the Vmax of 5'-guanylylimidodiphosphate (GppNHp) and forskolin stimulation of adenylate cyclase activity was significantly lower, 70% and 55%, respectively (p less than 0.01), in both ventricles of the paced dogs. However, although the concentration yielding half-maximal velocity for beta-agonist and GppNHp stimulation of adenylate cyclase was similar in both groups, that for forskolin stimulation of the enzyme was significantly increased (p less than 0.01). Pertussis toxin-mediated ADP-ribosylation of membranes from control and failing hearts revealed a significant decrease in the inhibitory guanine nucleotide binding protein content (48 +/- 9%, p less than 0.01) in the hearts of the paced dogs. Moreover, although the pertussis toxin treatment increased the basal and the forskolin-stimulated adenylate cyclase activity in both normal and failing heart membranes, the adenylate cyclase activity remained significantly depressed in the failing heart after pertussis toxin treatment (p less than 0.01). Consistent with the depressed adenylate cyclase activity, mechanical studies on isolated papillary muscles and trabeculae revealed a decrease in baseline total tension (from 7.0 +/- 0.7 to 3.8 +/- 0.4 g/mm2, p less than 0.01) and dT/dt (from 26 +/- 8 to 13 +/- 1 g/mm2/sec, p less than 0.01) in the pacing-overdrive model. Tension generation and dT/dt observed in the paced dogs in response to increasing concentrations of forskolin demonstrated a rightward shift in the dose-response curve and a decrease in maximal forskolin stimulation (p less than 0.01). Similarly, maximal tension and dT/dt in the presence of isoproterenol was significantly lower than in the normal dogs (p less than 0.01). The decrease in beta-adrenergic responsiveness was accompanied by a decrease and rightward shift in alpha 1-adrenergic responsiveness (increase in tension was 1.1 +/- 0.1 g/mm2 in paced dogs versus 2.1 +/- 0.1 g/mm2 in controls, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

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The bulk of the evidence supports the notion that there is a life course association between socioeconomic position early in life and physical activity during adulthood. Studies using more rigorous methodology supported this conclusion more consistently.