Intensifying Functional Task Practice to Meet Aerobic Training Guidelines in Stroke Survivors

 

How will this be possible  for those with stroke fatigue?

At least half of all stroke survivors experience fatigue 

Or is it 70%?

Or is it 40%?

 

Intensifying Functional Task Practice to Meet Aerobic Training Guidelines in Stroke Survivors

Liam P. Kelly,^1,* Augustine J. Devasahayam,¹ Arthur R. Chaves,¹ Elizabeth M. Wallack,¹ Jason McCarthy,¹ Fabien A. Basset,² and Michelle Ploughman¹

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Abstract

Objective: To determine whether stroke survivors could maintain workloads during functional task practice that can reach moderate levels of cardiometabolic stress (i.e., ≥40% oxygen uptake reserve (V˙O₂R) for ≥20 min) without the use of ergometer-based exercise.

Design: Cross-sectional study using convenience sampling.

Setting: Research laboratory in a tertiary rehabilitation hospital.

Participants: Chronic hemiparetic stroke survivors (>6-months) who could provide consent and walk with or without assistance.

Intervention: A single bout of intermittent functional training (IFT). The IFT protocol lasted 30 min and involved performing impairment specific multi-joint task-oriented movements structured into circuits lasting ~3 min and allowing 30–45 s recovery between circuits. The aim was to achieve an average heart rate (HR) 30-50 beats above resting without using traditional ergometer-based aerobic exercise.

Outcome measures: Attainment of indicators for moderate intensity aerobic exercise. Oxygen uptake (V˙O₂), carbon dioxide production (V˙CO₂), and HR were recorded throughout the 30 min IFT protocol. Values were reported as percentage of V˙O₂R, HR reserve (HRR) and HRR calculated from predicted maximum HR (HRR_pred), which were determined from a prior maximal graded exercise test.

Results: Ten (3-female) chronic (38 ± 33 months) stroke survivors (70% ischemic) with significant residual impairments (NIHSS: 3 ± 2) and a high prevalence of comorbid conditions (80% ≥ 1) participated. IFT significantly increased all measures of exercise intensity compared to resting levels: V˙O₂ (Δ 820 ± 290 ml min⁻¹, p < 0.001), HR (Δ 42 ± 14 bpm, p < 0.001), and energy expenditure (EE; Δ 4.0 ± 1.4 kcal min⁻¹, p < 0.001). Also, mean values for percentage of V˙O₂R (62 ± 19), HRR (55 ± 14), and HRR_pred (52 ± 18) were significantly higher than the minimum threshold (40%) indicating achievement of moderate intensity aerobic exercise (p = 0.004, 0.016, and 0.043, respectively).

Conclusion: Sufficient workloads to achieve moderate levels of cardiometabolic stress can be maintained in chronic stroke survivors using impairment-focused functional movements that are not dependent on ergometers or other specialized equipment.

Keywords: stroke rehabilitation, physical exertion, physical therapy modalities, aerobic exercise, cardiometabolic stress

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Introduction

Stroke mortality rate continues to decrease thanks to advances in medical management (Thrift et al., 2017) and emergency medical care (Crichton et al., 2016). However, the amount of recovery observed after disabling stroke remains largely unchanged and the number of individuals living with life-altering physical and cognitive impairments due to stroke is increasing (Krueger et al., 2015). A major challenge to regaining function after disabling stroke is the limited time window for optimal recovery, which is thought to occur within the first 3 months (Cramer, 2008; Murphy and Corbett, 2009). This sensitive period for enhanced plasticity and subsequent plateau of recovery follows well-defined neurobiological processes that involve upregulation of growth-promoting factors followed by their downregulation with concurrent increases in growth-inhibiting factors (Murphy and Corbett, 2009). Substantial resources are currently being employed to develop interventions that extend this time window and possibly even enhance repair mechanisms through use of stem cells, brain stimulation, and other pharmaceutical therapies (Ward, 2017). However, it is unclear whether the plateau of recovery observed post-stroke is due to a failure of the mechanisms underlying spontaneous biological recovery or if it is related to suboptimal dosage of physical and behavioral therapies (Ward, 2017). Animal models of stroke reinforce the critical importance of intense therapeutic exercise combined with an enriched environment to optimize the efficacy of pharmaceutical, and stem cell interventions (Johansson, 2000; Hicks et al., 2009; Ploughman et al., 2009; Sale et al., 2014). Therefore, stroke rehabilitation must be optimized to not only take advantage of intrinsic mechanisms for recovery but also to enhance the effects of emerging therapies.

Unfortunately, current inpatient stroke rehabilitation is of insufficient intensity to promote optimal recovery. Studies from across the globe consistently report that stroke patients spend most of their time “inactive and alone” (Bernhardt et al., 2004) throughout the acute and subacute phases of recovery (Astrand et al., 2016). Also, the total amount of work performed during structured therapy is below levels required to maintain functional fitness (Macko et al., 2005) and reduce cardiovascular risk (MacKay-Lyons and Makrides, 2002). Accordingly, patients in both the acute and chronic phases of recovery demonstrate levels of cardiorespiratory fitness that are about half (~16 ml min⁻¹ kg ⁻¹) of those observed in age and gender matched populations (Potempa et al., 1995; Smith et al., 2012; Mackay-Lyons et al., 2013a; Ivey et al., 2015). In addition to increasing risk for recurrent stroke (Mackay-Lyons et al., 2013b), such levels of physical deconditioning limit patients' ability to participate in structured therapy (Tang et al., 2009; Billinger et al., 2015) and may even contribute to a ceiling for neuromotor recovery (Ploughman and Kelly, 2016). Given the inverse association between cardiorespiratory fitness and stroke risk (Pandey et al., 2016), premorbid physical activity levels also contribute to the poor aerobic capacity observed after rehabilitation. Regardless, the low intensity nature of the inpatient environment must be addressed to optimize recovery.

Several studies have proposed adding ergometer-based aerobic training to inpatient rehabilitation (Tang et al., 2009; Mackay-Lyons et al., 2013a; Wang et al., 2014), while others have suggested that practice of gross motor skills could produce a training effect if there was adequate attention to heart rate monitoring (Otterman et al., 2012; van de Port et al., 2012; Marsden et al., 2017). In either case, stroke best practice guidelines have advised therapists to provide aerobic training in addition to a minimum of 3 h per day of skilled task training (Billinger et al., 2014; Hebert et al., 2016). In practice, however, there are many challenges to implementing such recommendations including insufficient time, lack of resources, patient level of impairment, and concern for ongoing cardiovascular risk (Bayley et al., 2012; Biasin et al., 2014; Prout et al., 2016). Rehabilitative strategies that are individualized to level of impairment, addressing multiple targets (i.e., relearning of functional tasks and cardiorespiratory fitness), and which do not rely on specialized equipment are urgently needed. The purpose of the current study was to determine whether functional task practice could be structured in such a way to maintain sufficient workloads to reach moderate levels of cardiometabolic stress (i.e., ≥40% oxygen uptake reserve (V˙O₂R) for ≥20 min) without the use of ergometers. As a first step, an impairment-based intermittent functional training (IFT) protocol was developed to answer this question among chronic stroke survivors. It was hypothesized that (i) workloads maintained during IFT would cause significant elevations in cardiometabolic responses compared to resting values, and (ii) the increased cardiometabolic demands of IFT would be within a range needed to increase cardiorespiratory fitness (i.e., moderate-to-vigorous intensity).