The effects of dynamic and isometric muscle contractions on the lymph flow dynamics in human skeletal muscle were studied with a scintographic method. Radioactively labelled human serum albumin (99mTc‐HSA) 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) dynamic knee extensions (CONS), (ii) isometric contractions with the knees at full extension (IMExt), or (iii) isometric contractions with knees fixed at 90 deg angle flexion (IMFlex). The exercises were separated by 65 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 during the periods of interest (CR unit =% min−). The clearance rate was low during the rest periods (0.04 ± 0.05% min−1), though higher 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 rate three‐ to sixfold, to 0.16 ± 0.16% min−1 during CONS, 0.20 ± 0.15% min− during IMExt and 0.09 ± 0.11 % min−1 during IMFlex. There were no differences between the subject subgroups. The higher clearance rate during IMExt than during IMFlex (P= 0.02) demonstrates the importance of muscle deformations on lymph propulsion and experimentally confirms the current concepts of lymph formation and propulsion in voluntarily active skeletal muscle. It is suggested that lymph propulsion by working muscle is most efficient when the muscle is able to shorten close to its minimum length.

No abstract

This study was designed to find out if the lymph flow, indicated as albumin clearance, from active skeletal muscle is maintained constant during a prolonged steady-state exercise. 99mTc-labelled albumin was injected bilaterally into the vastus lateralis muscles of eight endurance-trained men. The radioactivity at the injection site was monitored by a gamma-camera before, frequently during, and after a 2 h run at a controlled steady intensity of 69 +/- 4% of the maximal heart rate. The fractional clearance rate of albumin was calculated for each monitoring interval, and was expressed as percentage clearance per minute (% min(-1)). During the first 15 min of exercise the clearance rate was five times higher than at rest before the exercise (0.29 +/- 0.12 vs. 0.06 +/- 0.05% min(-1), P = 0.001). During the next 25 min of running the clearance rate fell to 0.19 +/- 0.08% min(-1) (P = 0.02), from which level it was further attenuated, being 0.12 +/- 0.04% min(-1) at the end of the exercise. After the exercise the clearance rate fell rapidly to the level of 0.04 +/- 0.03% min(-1). The results showed that the albumin clearance from working muscles is not constant during steady-state exercise, suggesting that lymph flow from exercising skeletal muscle may not be constant despite lymphatic pumping being assumed to be unchanged during the course of exercise (i.e. constant exercise intensity and running speed).

This study was designed to find out if the lymph flow, indicated as albumin clearance, from active skeletal muscle is maintained constant during a prolonged steady‐state exercise. 99mTc‐labelled albumin was injected bilaterally into the vastus lateralis muscles of eight endurance‐trained men. The radioactivity at the injection site was monitored by a gamma‐camera before, frequently during, and after a 2 h run at a controlled steady intensity of 69 ± 4% of the maximal heart rate. The fractional clearance rate of albumin was calculated for each monitoring interval, and was expressed as percentage clearance per minute (% min‐1). During the first 15 min of exercise the clearance rate was five times higher than at rest before the exercise (0.29 ± 0.12 vs. 0.06 ± 0.05% min‐1, P = 0.001). During the next 25 min of running the clearance rate fell to 0.19 ± 0.08% min‐1 (P = 0.02), from which level it was further attenuated, being 0.12 ± 0.04% min‐1 at the end of the exercise. After the exercise the clearance rate fell rapidly to the level of 0.04 ± 0.03% min‐1. The results showed that the albumin clearance from working muscles is not constant during steady‐state exercise, suggesting that lymph flow from exercising skeletal muscle may not be constant despite lymphatic pumping being assumed to be unchanged during the course of exercise (i.e. constant exercise intensity and running speed).

A new method to fuse the distribution of radiation in the synovectomy of the knee was developed using SPECT/MRI image registration. Image registration of SPECT and MRI can be used to determine the activity distribution of radioisotopes in relation to synovitis.