Blood pressure and calf muscle oxygen extraction during plantar flexion exercise in peripheral artery disease

• Published in: Journal of applied physiology (1985) Vol. 123; no. 1; pp. 2 - 10
• Main Authors: Luck, J. Carter, Miller, Amanda J., Aziz, Faisal, Radtka, John F., Proctor, David N., Leuenberger, Urs A., Sinoway, Lawrence I., Muller, Matthew D.
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.07.2017
• Subjects: Aged; Arteries; Arteriosclerosis; Atherosclerosis; Blood pressure; Blood Pressure - physiology; Cardiovascular diseases; Exercise; Exercise - physiology; Fatigue; Female; Heart rate; Hemoglobin; Humans; I.R. radiation; Infrared spectra; Infrared spectroscopy; Intermittent Claudication - diagnosis; Intermittent Claudication - physiopathology; Male; Microvasculature; Middle Aged; Muscle, Skeletal - physiology; Muscles; Near infrared radiation; Oxygen; Oxygen Consumption - physiology; Oxygen uptake; Oxygenation; Patients; Peripheral Arterial Disease - diagnosis; Peripheral Arterial Disease - physiopathology; Physical training; Physiological responses; Pilot Projects; Plant extracts; Plantar flexion; Plantar Plate - physiology; Range of Motion, Articular - physiology; Reduction; Skeletal muscle; Vascular diseases; Vein & artery diseases; heart rate; muscle metabolism; exercise physiology; sympathetic nervous system
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.01110.2016

Peripheral artery disease (PAD) is an atherosclerotic vascular disease that affects 200 million people worldwide. Although PAD primarily affects large arteries, it is also associated with microvascular dysfunction, an exaggerated blood pressure (BP) response to exercise, and high cardiovascular mortality. We hypothesized that fatiguing plantar flexion exercise that evokes claudication elicits a greater reduction in skeletal muscle oxygenation (SmO 2 ) and a higher rise in BP in PAD compared with age-matched healthy subjects, but low-intensity steady-state plantar flexion elicits similar responses between groups. In the first experiment, eight patients with PAD and eight healthy controls performed fatiguing plantar flexion exercise (from 0.5 to 7 kg for up to 14 min). In the second experiment, seven patients with PAD and seven healthy controls performed low-intensity plantar flexion exercise (2.0 kg for 14 min). BP, heart rate (HR), and SmO 2 were measured continuously using near-infrared spectroscopy (NIRS). SmO 2 is the ratio of oxygenated hemoglobin to total hemoglobin, expressed as a percent. At fatigue, patients with PAD had a greater increase in mean arterial BP (18 ± 2 vs. vs. 10 ± 2 mmHg, P = 0.029) and HR (14 ± 2 vs. 6 ± 2 beats/min, P = 0.033) and a greater reduction in SmO 2 (−54 ± 10 vs. −12 ± 4%, P = 0.001). However, both groups had similar physiological responses to low-intensity, nonpainful plantar flexion exercise. These data suggest that patients with PAD have altered oxygen uptake and/or utilization during fatiguing exercise coincident with an augmented BP response. NEW & NOTEWORTHY In this laboratory study, patients with peripheral artery disease performed plantar flexion exercise in the supine posture until symptoms of claudication occurred. Relative to age- and sex-matched healthy subjects we found that patients had a higher blood pressure response, a higher heart rate response, and a greater reduction in skeletal muscle oxygenation as determined by near-infrared spectroscopy. Our data suggest that muscle ischemia contributes to the augmented exercise pressor reflex in peripheral artery disease.