Abstract

Background: The increase in exercising leg blood flow (LBF) is directly proportional to the workload performed, in relation to the interplay between cardiovascular regulation and muscle energy metabolism. However, little information is available on exercise LBF in thigh muscle contractions in amputated lower legs (ALL) via the stump fitting prosthesis.

Case presentation: A 79-year-old male patient performed 3-min one-legged repeat/dynamic knee extensor exercise at a target muscle contraction frequency (1-s thigh muscle contraction and 1-s relaxation, 90 repetitions) on each leg (left ALL as trans-tibial amputation using a patellar tendon-bearing prosthesis and right non-ALL) at six different contraction intensities. Simultaneous measurement of blood velocity/flow (Doppler ultrasound) in the femoral artery, blood pressure, leg vascular conductance and muscle strength were performed at pre-exercise, during 3-min exercise and 5-min recovery. There was a 12% reduction in the maximum thigh circumference in the ALL compared to non-ALL. LBF was lower in the ALL than non- ALL at pre-exercise and during exercise. In non-ALL, there was a good positive linear relationship (r=0.922, P<0.01) between mean peak muscle strength and mean exercising LBF during 30-s steady-state before the end of exercise, but the same relationship was not seen (r=0.220, P=ns) in the ALL.

Conclusions: The present clinical intervention study showed no significant thigh LBF increase in the ALL with incremental workload (peak muscle strength). This might be due to a mismatch of the workloaddependent LBF increase in the disused and/or atrophic thigh muscle-resection stump of the ALL compared to non-ALL, which in ALL may be due to remaining muscle contractile effort with a reduced arterial inflow and/or lack of venous return in relation to the arteriovenous pressure gradient and/or hydrostatic pressure through the lower leg.

Keywords: Exercising blood flow, knee amputation, dynamic knee extensor exercise, prosthesis, Doppler ultrasound