LYMPH-FLOW DYNAMICS IN EXERCISING HUMAN SKELETAL-MUSCLE AS DETECTED BY SCINTOGRAPHY

1. The effects of dynamic and isometric muscle contractions on the lym ph flow dynamics in human skeletal muscle were studied with a scintogr aphic method. 2. Radioactively labelled human serum albumin (Tc-99m-HS A) was injected bilaterally into the vastus lateralis muscles of eight men (n = 16), four of whom had had an endurance training background. The subjects performed 100 submaximal contractions in 10 min as (i) dy namic knee extensions (CONS), (ii) isometric contractions with the kne es at full extension (IMExt), or (iii) isometric contractions with kne es fixed at 90 deg angle flexion (IMFlex). The exercises were separate d by 85 min periods in supine rest. The level of radioactivity at the injection site was monitored by a gamma-camera, and the clearance rate of radioactivity (CR) was calculated as the fractional decrease durin g the periods of interest (CR unit = % min(-1)). 3. The clearance rate was low during the rest periods (0.04 +/- 0.05% min(-1)), though high er in the trained than in the sedentary subjects (0.06 +/- 0.05 vs. 0. 03 +/- 0.03% min(-1); P = 0.008). Exercise increased the clearance rat e three-to sixfold, to 0.16 +/- 0.16% min(-1) during CONS, 0.20 +/- 0. 15% min(-1) during IMExt and 0.09 +/- 0.11 % min(-1) during IMFlex. Th ere were no differences between the subject subgroups. 4. The higher c learance rate during IMExt than during IMFlex (P = 0.02) demonstrates the importance of muscle deformations on lymph propulsion and experime ntally confirms the current concepts of lymph formation and propulsion in voluntarily active skeletal muscle. It is suggested that lymph pro pulsion by working muscle is most efficient when the muscle is able to shorten close to its minimum length.