Lymph flow in instrumented dogs varies with exercise intensity.
BACKGROUND
Although it is generally accepted that exercise accelerates lymph flow, no study has directly measured lymph flow as a function of exercise intensity. In this study, we have measured flow in the thoracic lymph duct of five instrumented dogs while they ran on a treadmill.


RESULTS
Dogs were surgically instrumented with an ultrasonic flow transducer on the thoracic lymph duct and a catheter in the descending thoracic aorta. After recovery from surgery, the dogs ran on a treadmill at speeds which varied stepwise from 0 to 10 mph and from 10 to 0 mph. Dogs ran for 1 min at each speed with 15 min rest between each exercise. Heart rate increased significantly during exercise, whereas mean aortic pressure did not change. Resting lymph flow was 1.7+/-0.2 ml/min. Exercise at 1.5 mph significantly increased lymph flow to 3.9 +/- 0.6 ml/min (P < 0.01), 121% higher than resting flow. Lymph flow was further elevated at higher treadmill speeds, reaching 9.0 +/-1.6 ml/min (P < 0.01) at 10 mph, 419% higher than resting flow. Regression analysis demonstrated a linear relationship between treadmill speed and the percent increase in lymph flow. Lymph flow returned to the resting rate 1-2 min post-exercise.


CONCLUSIONS
Lymph flow in the thoracic duct is positively correlated with exercise intensity.
Desai
Pratikkumar
P
Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA.
Williams
Arthur G
AG
Prajapati
Parna
P
Downey
H Fred
HF
D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D002404:Catheterization; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D016014:Linear Models; D008196:Lymph / Q000502:physiology*; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D013897:Thoracic Duct / Q000502:physiology*