Limb-specific blood flow regulation during cycling exercise in traumatic single lower limb amputees

To investigate the limb-specific blood flow regulation during dynamic bilateral cycling exercise in individuals with traumatic single lower-limb amputation compared to a control group.

Seven individuals with single lower leg amputation (AMP) (37 ± 11 years, 11 ± 8 years since amputation) and 7 age-matched controls (Ctrl) (36 ± 10 years) were tested during three 5 min constant workload exercise at 60W, 100W, and 80% of peak power output (PPO), on a reclined cycling ergometer. In AMP, femoral blood flow (FBF) and leg vascular conductance (LVC) were measured in the amputated leg (AL) and whole leg (WL), while in Ctrl, the same measurements were obtained in the right and left legs. Interlimb balance was measured with a power meter, and bilateral asymmetry index was calculated for FBF and interlimb balance. Oxygen consumption ( $\dot{V}$ O₂), ventilation ( ${\dot{V}}_E$ ), mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO) were also quantified.

AMP exhibited lower FBF in AL compared to WL (60W, - 61%; 100W, -69%; 80% PPO, - 64%; p < 0.001). LVC increased as expected in WL but did not increase significantly throughout workloads in AL. Interlimb balance exhibited a much higher contribution of the WL (60W, 76% of the work; 100W, 68%; 80% PPO,65%) than AL (60W, 26%; 100W, 34%; 80% PPO, 35%). No differences were found in FBF (p = 0.187), LVC (p = 0.871), and interlimb balance (p = 0.829) in CTRLs. No difference between AMP and CTRL in $V$ O₂ (p = 0.241), ${\dot{V}}_E$ (p = 0.124), MAP (p = 0.186), HR (p = 0.360), and CO (p = 0.144) at any workload was detected.

Individuals with amputation present considerable limb-specific blood flow regulation during bilateral cycling exercise. Understanding the mechanisms for this interlimb difference may provide important information to improve rehabilitation and training in this population.