Purpose: This study examined tissue oxygen saturation (StO2) of the vastus lateralis (VL) muscles of chronic stroke survivors during a graded exercise test (GXT). We hypothesized that the reduction in StO2 will be blunted in the paretic versus nonparetic VL during a maximum effort GXT. Methods: Chronic stroke survivors performed a GXT, and StO2 of the VL in each leg was measured using near-infrared spectroscopy. Twenty-six stroke survivors performed a GXT. Results: At rest, there was no difference in StO2 between the paretic and nonparetic VL (65 ± 9% vs 68 ± 7%, respectively, P = .32). The maximum change in StO2 from rest during the GXT was greater in the nonparetic versus the paretic VL (−16 ± 14% vs −9 ± 10%, respectively, P < .001). The magnitude of the oxygen resaturation response was also greater in the nonparetic versus the paretic VL (29 ± 23% vs 18 ± 15%, respectively, P < .001). VO2 peak was associated with the magnitude of the VL StO2 change during (r2 = 0.54, P < .0001) and after (r2 = 0.56, P < .001) the GXT. Conclusion: During a GXT, there is a blunted oxygen desaturation response in the paretic versus the nonparetic VL of chronic stroke survivors. In the paretic VL, there was a positive correlation between the oxygen desaturation response during the GXT and VO2 peak.

In this study, we report that 2 wk of remote ischemic conditioning (RIC) improves brachial artery flow-mediated dilation in chronic stroke survivors. Because poor cardiovascular health puts stroke survivors at a heightened risk for recurrent stroke and other cardiovascular events, an intervention that is simple, cost-effective, and easy to perform like RIC holds promise as a means to improve cardiovascular health in this at-risk population.

Introduction: Brachial artery flow mediated dilation (FMD) is a well-established measure of vascular endothelial health and is pathologically low in chronic stroke survivors. Ischemic conditioning (IC) is a cardioprotective stimulus and has been shown to improve FMD and enhance motor function in healthy humans. We recently showed that IC can improve paretic muscle strength and increase self-selected walking speed in stroke survivors. These improvements could be, in part, mediated by improved peripheral vascular function and increased blood flow to the exercising muscle. The effects of IC on vascular endothelial function post-stroke have not been investigated. Hypothesis: Two weeks of IC on the paretic leg of chronic stroke survivors will improve FMD in the non-paretic brachial artery. Methods: This was a prospective, randomized, blinded and controlled pilot study. Twenty chronic stroke survivors (>1-year post-stroke) received either IC (cuff inflation on the paretic leg for five minutes to 225 mmHg) or Sham IC (cuff inflation to 10 mmHg) every other day for two weeks (five on-off cycles per session). Brachial artery FMD was assessed using ultrasonography within 48 hours of the beginning and end of the intervention period. Results: Eight men and twelve women participated in this study. The mean age was 59 ± 16 years and the mean time post-stroke was 9 ± 9 years. Brachial artery FMD increased in the IC group from 6.2 ± 4.9% to 8.9 ± 3.9% (n=10; p=0.023, 2-way Repeated Measures ANOVA) while no change was observed in the Sham IC group (pre- vs. post = 3.8 ± 3.9% vs. 2.7 ± 3.1%, respectively; p=0.32, n=10). Expressed as the mean change in FMD, IC increased FMD by 2.8 ± 3.7% while no change was observed in the Sham IC group (delta FMD = -1.1 ± 3.4%; p=0.024 IC vs. IC Sham, unpaired t-test). Conclusions: Two weeks of IC increases brachial artery FMD in chronic stroke survivors. Taken together with our previous work that shows IC increases paretic muscle strength and walking speed in chronic stroke survivors, IC has the potential to improve both motor and cardiovascular function post-stroke. Future larger studies are needed to evaluate the efficacy of IC to improve stroke recovery and to identify the pathways involved which confer benefit to both the nervous and cardiovascular systems.

This pilot study examined whether ischemic conditioning (IC), a noninvasive, cost-effective, and easy-to-administer intervention, could improve gait speed and paretic leg muscle function in stroke survivors. We hypothesized that 2 wk of IC training would increase self-selected walking speed, increase paretic muscle strength, and reduce neuromuscular fatigability in chronic stroke survivors. Twenty-two chronic stroke survivors received either IC or IC Sham on their paretic leg every other day for 2 wk (7 total sessions). IC involved 5-min bouts of ischemia, repeated five times, using a cuff inflated to 225 mmHg on the paretic thigh. For IC Sham, the cuff inflation pressure was 10 mmHg. Self-selected walking speed was assessed using the 10-m walk test, and paretic leg knee extensor strength and fatigability were assessed using a Biodex dynamometer. Self-selected walking speed increased in the IC group (0.86 ± 0.21 m/s pretest vs. 1.04 ± 0.22 m/s posttest, means ± SD; P < 0.001) but not in the IC Sham group (0.92 ± 0.47 m/s pretest vs. 0.96 ± 0.46 m/s posttest; P = 0.25). Paretic leg maximum voluntary contractions were unchanged in both groups (103 ± 57 N·m pre-IC vs. 109 ± 65 N·m post-IC; 103 ± 59 N·m pre-IC Sham vs. 108 ± 67 N·m post-IC Sham; P = 0.81); however, participants in the IC group maintained a submaximal isometric contraction longer than participants in the IC Sham group (278 ± 163 s pre-IC vs. 496 ± 313 s post-IC, P = 0.004; 397 ± 203 s pre-IC Sham vs. 355 ± 195 s post-IC Sham; P = 0.46). The results from this pilot study thus indicate that IC training has the potential to improve walking speed and paretic muscle fatigue resistance poststroke. NEW & NOTEWORTHY This pilot study is the first to demonstrate that ischemic conditioning can improve self-selected walking speed and reduce paretic muscle fatigue in stroke survivors. Ischemic conditioning has been shown to be safe in numerous patient populations, can be accomplished at home or at the bedside in only 45 min, and requires no specialized training. Future larger studies are warranted to determine the efficacy of ischemic conditioning as a neurorehabilitation therapy poststroke.

Introduction: Weakness of the contralateral leg muscles commonly occurs following unilateral stroke. We and others have also shown that the femoral artery is atrophied in the paretic (P) limb of chronic stroke subjects (>6 months post-stroke) compared to the non-paretic (NP) limb, and that both resting and hyperemic blood flow to the exercising muscle are dramatically reduced. Further, the hyperemic response positively correlates with leg strength and clinical measures of leg function. It is unknown if these changes in femoral artery diameter and peripheral blood flow are present in the subacute phase of stroke (<30 days post-stroke). Hypothesis: Femoral artery diameter is smaller, and resting and hyperemic blood flow to exercising muscle is reduced in the P limb in subjects in the subacute phase of stroke admitted to inpatient rehabilitation. Methods: Stroke patients were tested within three days of admission to inpatient rehabilitation in a hospital setting. Isometric knee extensor maximal voluntary contractions (MVCs) were measured in both legs using a Biodex dynamometer. Superficial femoral artery diameter and blood flow were measured at rest and immediately following MVCs using Doppler ultrasound. Results: A pilot group of four subjects (1 male, 3 female) aged 68 ± 4 years (range 56-75 years) completed all study procedures on average 13 ± 5 days post ischemic stroke (range 7-24 days). All subjects had infarcts of the middle cerebral artery (3 right, 1 left). P leg knee extensor MVCs were lower compared to the NP leg (93.8 ± 25.5 Nm vs. 160.4 ± 33.2 Nm, respectively; p<0.05). Superficial femoral artery diameter was smaller in the P leg compared to the NP leg (5.7 ± 0.4 mm vs. 6.0 ± 0.5 mm, respectively; p=0.06), and resting blood flow was reduced (172 ± 46 ml/min vs. 206 ± 54 ml/min, respectively; p<0.05). Hyperemic blood flow in response to knee extensor MVCs was also lower in the P limb compared to the NP limb (239 ± 62 ml/min vs. 435 ± 67 ml/min, respectively; p<0.05). Conclusions: We show feasibility of testing knee extensor muscle strength and peripheral blood flow in subacute stroke inpatients. Our preliminary data indicates that femoral artery atrophy has occurred in the P leg and that both resting and hyperemic blood flow to the P muscle are reduced.