The purpose of this study is to test the effects of leg exercise assistive paddling (LEAP) therapy during prolonged sitting (PS) on vascular and functional performance in those with peripheral artery disease (PAD) and age-matched controls. LEAP therapy is a novel application of passive limb movement to enhance blood flow through the legs without muscular contractions. Specifically, LEAP therapy is the rotational passive movement of the lower leg about the knee from 90 to 180 degrees of rotation at a cadence of 1Hz. Previous literature has indicated that this movement pattern can produce robust increases in blood flow in the passively moved limb in healthy individuals, and passive limb movement may protect vascular function during PS. However, the impact of LEAP therapy to improve blood flow in the legs of those with PAD during PS is unknown.
Participants will participate in a randomized cross-over design study with 2 visits (LEAP therapy and no LEAP therapy). For the first visit, participants will be randomly allocated to receive LEAP therapy during 2.5 hours of PS or not. For the second visit, participants will sit for 2.5 hours and will receive the condition that they did not previously receive. Before and after PS, the following measurements will be made: flow-mediated dilation of the popliteal and brachial arteries, arterial stiffness with tonometry techniques, microvascular vasodilatory capacity and skeletal muscle metabolic rate with near-infrared spectroscopy, autonomic nervous system function, and there will be blood drawn from the antecubital vein. After PS, participants will participate in a graded exercise test to assess functional walking capacity. Finally, during PS, near-infrared spectroscopy on the calf muscles and electrocardiogram will be collected continuously to monitor muscle oxygen availability and autonomic activity, respectively.
Able to provide written informed consent
50-85 years of age
Diagnosed with Peripheral Arterial Disease (PAD) Fontaine stage II-III
Women must be postmenopausal (cessation of menses for > 24 months)
Pain at rest and/or tissue loss from Peripheral Arterial Disease (PAD), Fontaine stage IV PAD
Acute lower extremity ischemic event secondary to thromboembolic disease or acute trauma
Limited walking capacity from conditions other than PAD
Have not had a physical exam to assess exercise limitations in the past year
Crossover
LEAP therapy
Other interventionKnee bending from 90°-180° at 1Hz for 1 minute every 10 minutes during 2.5 hours of prolonged sitting
no LEAP therapy
Other intervention2.5 hours of uninterrupted prolonged sitting (no movement)
Macrovascular Endothelial Function
Macrovascular endothelial function will be measured non-invasively using the flow-mediated dilation (FMD) technique in the brachial and popliteal arteries using a Doppler ultrasound. These measures will be performed before and after 2.5 hours of prolonged sitting with LEAP therapy, and before and after 2.5 hours of prolonged sitting without LEAP therapy.
Microvascular Vasodilatory Capacity
Microvascular vasodilatory capacity will be measured as the near-infrared spectroscopy (NIRS) reoxygenation rate in the medial gastrocnemius after an arterial occlusion. These measures will be performed before and after 2.5 hours of prolonged sitting with LEAP therapy, and before and after 2.5 hours of prolonged sitting without LEAP therapy.
Femoral and Popliteal Artery Blood Flow
Femoral and popliteal artery blood flow will be measured in both legs using Doppler ultrasound. These measures will be performed before and after 2.5 hours of prolonged sitting with LEAP therapy, and before and after 2.5 hours of prolonged sitting without LEAP therapy.
Walking capacity
Physical walking capacity will be measured during the Gardner treadmill protocol. Participants will walk on a treadmill at 2.0 miles per hour (mph). Grade will began at zero and will be increased by two percent every two minutes. Participants unable to walk at least 2.0 mph begin walking at 0.5 mph and their speed is increased by 0.50 mph every two minutes until the participant reaches 2.0 mph. After reaching 2.0 mph, treadmill grade is increased by two percent every two minutes. Participants are asked to continue walking without stopping until they cannot continue because of leg symptoms, exhaustion, or other symptoms. These measures will be performed before and after 2.5 hours of prolonged sitting with LEAP therapy, and before and after 2.5 hours of prolonged sitting without LEAP therapy.
Click on the lead sponsor to view all of their trials.
