Filling and emptying characteristics of lower limb venous network in athletes. Study by postural plethysmography.

Leg volume changes were assessed in healthy volunteers by mercury strain gauge postural plethysmography in order to study the effects of different types of physical training on lower limb venous distensibility and emptying. Seven endurance trained subjects (E), seven muscle strength trained subjects (M) and seven sedentary subjects (S) were submitted to a tilt table test. The test measured leg filling volumes FV (ml.100 ml-1) during 30 head-up tilt, half-emptying time T1/2 (seconds) and venous output at the 6th second of emptying (VO6) (ml.100 ml-1.min-1) during return to horizontal position. Comparative tests were made using an ANOVA test. Results showed significantly higher values for FV and VO6 in E (FV: 3.9 +/- 0.2 ml.100 ml-1 in E vs 2.5 +/- 0.2 and 2.2 +/- 0.2 ml.100 ml-1 in M and S, respectively; VO6: 9.2 +/- 1.1 ml.100 ml-1.min-1 in E vs 6.9 +/- 0.7 and 5.5 +/- 0.5 ml.100 ml-1.min-1 in M and S, respectively) whereas no significant differences were observed between groups for T1/2. M and S had the same physiological responses to orthostatic stress. Endurance training seems to increase lower limb venous distensibility without affecting venous emptying and venous return from the lower limbs. These results suggest that the greater venous distensibility in endurance-trained subjects does not result from alterations of the visco-elastic properties of deep vein walls and that it is probably a physical response to hypervolemia consecutive to chronic aerobic training.