Our study objectively demonstrates the reduced physical activity of claudicating patients and documents physical activity/duration profiles throughout the day. The intensity of the physical activity of the average claudicating patient fluctuates very little during the day and rarely exceeds a light intensity level. Claudicating patients spend approximately half of their awake time in sedentary behavior and when they walk they do it in short bursts followed by several minutes of rest. We anticipate that changes in routine physical activity/duration profiles of patients with PAD will provide relevant, sensitive, and direct measures of the effectiveness of therapeutic interventions.

Objective-In patients with peripheral artery disease (PAD) supervised exercise therapy is a first line of treatment as it increases maximum walking distances comparable to surgical revascularization therapy. Little is known regarding gait biomechanics following supervised exercise therapy. This study characterized the effects of supervised exercise therapy on gait biomechanics and walking distances in claudicating patients with peripheral artery disease.Methods-Forty-seven claudicating patients with PAD underwent gait analysis before and immediately following 6 months of supervised exercise therapy. Exercise sessions consisted of a 5 min warmup of mild walking and stretching of upper and lower leg muscles, 50 min of intermittent treadmill walking, and 5 min cooldown (similar to warmup) 3 times per week. Measurements included self-perceived ambulatory limitations measured by questionnaire, anklebrachial index, walking distance measures, maximal plantarflexor strength measured by isometric dynamometry, and overground gait biomechanics trials performed prior to and after the onset of claudication pain. Paired t-tests were used to test for differences in quality of life, walking distances, ankle-brachial index, and maximal strength. A two factor repeated measures ANOVA determined differences for intervention and condition for gait biomechanics dependent variables.Results-Following supervised exercise therapy, quality of life, walking distances, and maximal plantar flexor strength improved, while ankle brachial index did not significantly change. Several gait biomechanics parameters improved following intervention including torque and power generation at the ankle and hip. Similar to previous studies the onset of claudication pain led to a worsening gait, or gait that was less like healthy individuals compared with pain free gait.

Objective Peripheral Artery Disease (PAD) is a common manifestation of atherosclerosis, characterized by lower leg ischemia and myopathy in association with leg dysfunction. Patients with PAD have impaired gait from the first step they take with consistent defects in the movement around the ankle joint especially in plantar flexion. Our goal was to develop muscle strength profiles to better understand the problems in motor control responsible for the walking impairment in patients with PAD. Methods Ninety-four claudicating PAD patients performed maximal isometric plantar flexion contractions lasting 10s in two conditions: pain-free (patient is well rested and has no claudication symptoms) and pain-induced (patient has walked and has claudication symptoms). Sixteen matched healthy Controls performed the pain-free condition only. Torque curves were analyzed for dependent variables of muscle strength and motor control. Independent t tests were used to compare variables between groups and dependent t tests determined differences between conditions. Results Patients with PAD had significantly reduced peak torque and Area Under the Curve compared to Controls. Measures of control differed between PAD conditions only. Load rate and Linear Region Duration were greater in the pain condition. Time to peak torque was shorter in the pain condition. Conclusions The current study conclusively demonstrates that the plantar flexor muscles of the PAD patient at baseline and without pain are weaker in patients with PAD compared to Controls. With the onset of claudication pain, patients with PAD exhibit altered muscle control strategies and further strength deficits are manifest compared to baseline levels. The myopathy of PAD legs appears to have a central role in the functional deterioration of the calf muscles, as it is evident both before and after onset of ischemic pain.

Peripheral artery disease (PAD) is an atherosclerotic disease that impairs blood flow and muscle function in the lower limbs. A skeletal muscle myopathy characterized by mitochondrial dysfunction and oxidative damage is present in PAD; however, the underlying mechanisms are not well-established. We investigated the impact of chronic ischemia on skeletal muscle microcirculatory function and its association with leg skeletal muscle mitochondrial function and oxygen delivery and utilization capacity in PAD. Gastrocnemius samples and arterioles were harvested from patients with PAD (n=10) and age-matched controls (CON, n=11). Endothelial-dependent and independent vasodilation was assessed in response to flow (30μL∙min-1), acetylcholine, and sodium nitroprusside (SNP). Skeletal muscle mitochondrial respiration was quantified by high-resolution respirometry, and microvascular oxygen delivery and utilization capacity (TOI) was assessed by near-infrared spectroscopy. Vasodilation was attenuated in PAD (P<0.05) in response to acetylcholine (CON: 71.1±11.1%, PAD: 45.7±18.1%) and flow (CON: 46.6±20.1%, PAD: 29.3±10.5%) but not SNP (P=0.30). Complex I+II state 3 respiration (P<0.01) and TOI recovery rate were impaired in PAD (P<0.05). Both flow and acetylcholine-mediated vasodilation were positively associated with complex I+II state 3 respiration (r=0.5 and r=0.5, respectively, P<0.05). Flow-mediated vasodilation and complex I+II state 3 respiration were positively associated with TOI recovery rate (r=0.8 and r=0.7, respectively, P<0.05). These findings suggest that chronic ischemia attenuates skeletal muscle arteriole endothelial function, which may be a key mediator for mitochondrial and microcirculatory dysfunction in the PAD leg skeletal muscle. Targeting microvascular dysfunction may be an effective strategy to prevent and/or reverse disease progression in PAD.

The purpose of the study was to compare the effects of a feedback-controlled treadmill (FeedbackTM) to a traditional fixed-speed treadmill (FixedTM) on spatiotemporal gait means, variability, and dynamics. The study also examined inter-session reliability when using the FeedbackTM. Ten young adults walked on the FeedbackTM for a 5-minute familiarization followed by a 16-minute experimental trial. They returned within one week and completed a 5minute familiarization followed by a 16-minute experimental trial each for FeedbackTM and FixedTM conditions. Mean walking speed and step time, length, width, and speed means and coefficient of variation were calculated from all experimental conditions. Step time, length, width, and speed gait dynamics were analyzed using detrended fluctuation analysis. Mean differences between experimental trials were determined using ANOVAs and reliability between FeedbackTM sessions was determined by intraclass correlation coefficient. No difference was found in mean walking speed nor spatiotemporal variables, with the exception of step width, between the experimental trials. All mean spatiotemporal variables demonstrated good to excellent reliability between sessions, while coefficient of variation was not reliable. Gait dynamics of step time, length, width, and speed were significantly more persistent during the FeedbackTM condition compared to FixedTM, especially step speed. However, gait dynamics demonstrated fair to poor reliability between FeedbackTM sessions. When walking on the FeedbackTM, users maintain a consistent set point, yet the gait dynamics around the mean are different when compared to walking on a FixedTM. In addition, spatiotemporal gait dynamics and variability may not be consistent across separate days when using the FeedbackTM.

Background: Patients with peripheral artery disease (PAD) who experience intermittent claudication report a range of symptoms. Patients with symptoms other than classically described intermittent claudication may be at the highest risk for functional decline and mobility loss. Therefore, technologies allowing for characterization of PAD severity are desirable. Near-infrared spectroscopy (NIRS) allows for measurements of muscle heme oxygen saturation (StO 2 ) during exercise. We hypothesized lower extremities affected by PAD would exhibit distinct NIRS profiles as measured by a lowcost, wireless NIRS device and that NIRS during exercise predicts walking limitation. Methods:We recruited 40 patients with PAD and 10 control participants. All patients with PAD completed a computed tomographic angiography, 6-minute walk test, and a standardized treadmill test. Controls completed a 540-second treadmill test for comparison. StO 2 measurements were continuously taken from the gastrocnemius during exercise.Variables were analyzed by Fischer's exact, c 2 , Wilcoxon rank-sum, and Kruskal-Wallis tests as appropriate. Correlations were assessed by partial Spearman correlation coefficients adjusted for occlusive disease pattern.Results: Patients with PAD experienced claudication onset at a median of 108 seconds with a median peak walking time of 288 seconds. The baseline StO 2 was similar between PAD and control. The StO 2 of PAD and control participants dropped below baseline at a median of 1 and 104 seconds of exercise, respectively (P < .0001). Patients with PAD reached minimum StO 2 earlier than control participants (119 seconds vs 522 seconds, respectively; P < .001) and experienced a greater change in StO 2 at 1 minute of exercise (À73.2% vs 8.3%; P < .0001) and a greater decrease at minimum exercise StO 2 (À83.4% vs À16.1%; P < .0001). For patients with PAD, peak walking time, and 6-minute walking distance correlated with percent change in StO 2 at 1 minute of exercise (r ¼ À0.76 and -0.67, respectively; P < .001) and time to minimum StO 2 (r ¼ 0.79 and 0.70, respectively; P < .0001). Conclusions:In this initial evaluation of a novel, low-cost NIRS device, lower extremities affected by PAD exhibited characteristic changes in calf muscle StO 2 , which differentiated them from healthy controls and were strongly correlated with walking impairment. These findings confirm and expand on previous work demonstrating the potential clinical value of NIRS devices and the need for further research investigating the ability of low-cost NIRS technology to evaluate, diagnose, and monitor treatment response in PAD. (J Vasc Surg 2020;71:946-57.)

The reliability of the treadmill belt speed using a feedback-controlled treadmill algorithm was analyzed in this study. Using biomechanical factors of the participant’s walking behavior, an estimated walking speed was calculated and used to adjust the speed of the treadmill. Our proposed algorithm expands on the current hypotheses of feedback-controlled treadmill algorithms and is presented below. Nine healthy, young adults walked on a treadmill controlled by the algorithm for three trials over two days. Each participant walked on the feedback-controlled treadmill for one 16-minute and one five-minute trial during day one and one 16-minute trial during day two. Mean, standard deviation, interclass correlation coefficient (ICC), and standard error of measurement (SEM) were analyzed on the treadmill belt speed mean, standard deviation, and coefficient of variation. There were significantly high ICC for mean treadmill speed within- and between-days. Treadmill speed standard deviation and coefficient of variation were significantly reliable within-day. These results suggest the algorithm will reliably produce the same treadmill belt speed mean, but may only produce a similar treadmill belt speed standard deviation and coefficient of variation if the trials are performed in the same day. A feedback-controlled treadmill algorithm that accounts for the user’s behavior provides a greater level of control and minimizes any possible constraints of walking on a conventional treadmill.

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