Lymph flow dynamics in exercising human skeletal muscle as detected by scintography.
Level 3 - non-randomized controlled study
Non-randomized controlled within-subject physiological study.
PubMed 9350633 · doi:10.1111/j.1469-7793.1997.233bf.x
What was done
Eight men (four endurance-trained, four sedentary) received bilateral injections of technetium-99m-labelled human serum albumin (99mTc-HSA) into the vastus lateralis muscles (n = 16 legs). Subjects completed 100 submaximal contractions in 10 minutes under three conditions separated by 65-minute supine rest intervals: dynamic knee extensions (CONS), isometric contractions at full knee extension (IMExt), and isometric contractions at 90-degree knee flexion (IMFlex). Clearance rate of radioactivity (% min-1) was monitored via gamma camera.
What was found
Resting clearance rate was 0.04 ± 0.05% min-1 overall, and was significantly higher in trained than sedentary subjects (0.06 ± 0.05 vs. 0.03 ± 0.03% min-1; P = 0.008). Exercise increased clearance rates 3- to 6-fold 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, with no subgroup differences during exercise. Clearance was significantly higher during IMExt than IMFlex (P = 0.02).
Why it matters
The findings provide direct human scintigraphic evidence that active skeletal muscle contractions stimulate lymphatic drainage, with lymph propulsion being most effective when the muscle shortens close to its minimum length.
Limits
The sample size was small (n = 8 men) and restricted to males. The trial order was not stated to be randomized, carry-over effects cannot be fully excluded, and radioisotope tracer clearance serves only as an indirect surrogate for total lymphatic flow.
Cited by
- supports The lymphatic system relies on skeletal muscle contractions, such as calf muscle action during walking, to pump and drain fluid.