Cardiovascular Response to Low-Intensity Walking with Restricted Leg Muscle Blood Flow

Abstract

Walk training with restricted leg muscular blood flow leads to hypertrophic effects in muscle (J Appl Physiol 100:1460–1466, 2006), but cardiovascular responses to this type training are not known. PURPOSE: To examine the cardiovascular responses to walking with restriction of venous blood flow from the leg (Kaatsu). METHODS: Eight healthy men (age: 26.9±3.1(SD)yrs, VO2max: 54.3±7.7 ml kg-1 min-1) performed two trials of treadmill walking with (Kaatsu) and without (control) restricted muscular blood flow. Exercise consisted of 5 2-min bouts of walking (33 m.min-1, 4% grade); rest: 1-min between bouts and 20 minutes between trials. A specially designed elastic belt (Kaatsu-Master, Japan; 50 mm wide) was placed around the most proximal portion of each leg during Kaatsu. A pneumatic bag on the belt's inner surface was connected to an electronic air pressure system that controlled the restriction pressure at 200 mmHg during rest and exercise with Kaatsu. Vo2 (indirect calorimetry) and cardiovascular response (impedance cardiography; CNSystems Medizintechnik, Austria) were determined before and during each bout of exercise. RESULTS: Pre-exercise Data: Vo2 (l.min-1, K: 0.32±0.08; C: 0.31±0.07) and cardiac output [(Q); l.min-1, K: 4.78±0.56; C: 4.96+0.69] were similar between trials. Stroke volume (SV) was lower (P<0.05) and heart rate was higher (P<0.05) during Kaatsu (64.5+9.0 ml and 76+11 b.min, respectively) than control (75.0±9.2 ml and 66±6 b.min-1, respectively). Mean arterial pressure (MAP) and total peripheral resistance (TPR) were similar during Kaatsu (101±10 mmHg and 1677±289 dyn*s.cm-5) and control (96±12 mmHg and 1543±371 dyn*s.cm-5). Exercise Data: Vo2 was 13% higher during Kaatsu, but Q was similar in both trials (l.min-1, K: 6.73±0.50; C: 7.48±0.87). SV was lower (P<0.01) and heart rate was higher (P<0.05) during Kaatsu (66.6±7.4 ml and 102±15 b.min-1, respectively) than control (83.1±10.3 ml and 90±10 b.min-1, respectively). MAP was similar (mmHg, K: 115±14; C: 102±14), but TPR was higher (P<0.05) during Kaatsu (dyn*s.cm-5, K: 1352±194; C: 1082+195). CONCLUSIONS: Kaatsu appears to cause a slight increase in metabolic cost of low-intensity walking. Despite flow restriction and reduced SV (increased TPR and apparent decrease in venous return) with Kaatsu, Q is maintained by higher heart rate.