Leg crossing with muscle tensing, a physical counter-manoeuvre to prevent syncope, enhances leg blood flow.

In patients with orthostatic intolerance, the mechanisms to maintain BP (blood pressure) fail. A physical counter-manoeuvre to postpone or even prevent orthostatic intolerance in these patients is leg crossing combined with muscle tensing. Although the central haemodynamic effects of physical counter-manoeuvres are well documented, not much is known about the peripheral haemodynamic events. Therefore the purpose of the present study was to examine the peripheral haemodynamic effects of leg crossing combined with muscle tensing during 70 degrees head-up tilt. Healthy subjects (n=13) were monitored for 10 min in the supine position followed by 10 min in 70 degrees head-up tilt and, finally, for 2 min of leg crossing with muscle tensing in 70 degrees head-up tilt. MAP (mean arterial BP), heart rate, stroke volume, cardiac output and total peripheral resistance were measured continuously by Portapres. Leg blood flow was measured using Doppler ultrasound. Leg vascular conductance was calculated as leg blood flow/MAP. A significant increase in MAP (13 mmHg), stroke volume (27%) and cardiac output (18%), a significant decrease in heart rate (-5 beats/min) and no change in total peripheral resistance during the physical counter-manoeuvre were observed when compared with baseline 70 degrees head-up tilt. A significant increase in leg blood flow (325 ml/min) and leg vascular conductance (2.9 arbitrary units) were seen during the physical counter-manoeuvre when compared with baseline 70 degrees head-up tilt. In conclusion, the present study indicates that the physical counter-manoeuvre of leg crossing combined with muscle tensing clearly enhances leg blood flow and, at the same time, elevates MAP.

Passive leg movements and passive cycling do not alter arterial leg blood flow in subjects with spinal cord injury.

BACKGROUND AND PURPOSE: Subjects with a spinal cord injury (SCI) are at increased risk for cardiovascular disease-related secondary complications, such as pressure ulcers and attenuated wound healing. It has been suggested that passive exercise enhances blood flow via mechanical pump effects or reflex activation. The purpose of this study was to assess the effects of passive leg movements and passive cycling on the arterial circulation in subjects with SCI. SUBJECTS: Eight men with motor complete SCI and 8 male control subjects participated. METHODS: Echo Doppler measurements were obtained to measure leg blood flow at rest, during and after 10 minutes of standardized passive leg movements, and during and after 20 minutes of passive leg cycling. Blood pressure was measured continuously, and total vascular resistance and leg vascular resistance were calculated. RESULTS: In both groups, no changes in leg blood flow, vascular resistance, or blood pressure were observed during or after the 2 interventions. DISCUSSION AND CONCLUSION: The results of the study demonstrate that passive leg movements and passive cycling do not alter the arterial peripheral circulation in subjects with SCI or control subjects. Although the results do not support the use of passive movements or exercise for the prevention of cardiovascular disease-related secondary complications, physical therapists should not be dissuaded from using these techniques to address musculoskeletal concerns.