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A case to be made: theoretical and empirical arguments for the need to consider fatigue in post-stroke motor rehabilitation.

Sterr A, Furlan L - Neural Regen Res (2015)

View Article: PubMed Central - PubMed

Affiliation: School of Psychology, University of Surrey, Guildford, UK ; Department of Neurology, University of Sao Paulo, Sao Paulo, Brazil.

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Given that, and further advancing our research agenda in this arena (Sterr et al., 2002; Sterr and Freivogel, 2003, 2004; Sterr, 2004; Sterr et al., 2006; Sterr and Saunders, 2006), we recently tested the efficacy of a 2-week modified constraint-induced (CI) therapy program in chronic stroke individuals with very low-functioning upper limb hemiparesis (Sterr et al., 2014a)... They were assessed at baseline and after the intervention (2 weeks before, immediately before and after, 6, and 12 months after)... Across the cohort, motor function improved significantly, and treatment benefits were largely sustained over the 12 months of follow-up... As suggested by previous work (Sterr et al., 2002), longer sessions of daily training were expected to yield better outcomes than short sessions, a finding in line with the theory that massed practice is essential for neuroplasticity processes driving the functional improvements induced by CI therapy... However, this was not entirely the case... While we found some differences suggesting greater benefit of longer training sessions, the picture was not as clear as one might expect... This is likely to elevate both perception of fatigue and fatigability during motor activities by accelerating depletion of skeletal muscle energy reserves and causing rapid declines in force production, respectively... While the first is likely a compound of an impaired cardiorespiratory system – which may fail to effectively supply contracting muscles with oxygen and nutrients – and a deteriorated musculoskeletal function – in terms of reduced capillary density and oxidative capacity limiting muscle energy production –, the latter mostly results from an impaired neuro-musculoskeletal system, owing primarily to both a reduced ability to activate spinal motor units and skeletal muscle plastic changes... When combined to a physically demanding motor training regimen such as CI therapy, this may well have exacerbated perception of fatigue and fatigability in our sample... The CI therapy intervention is grounded on this principle (Morris and Taub, 2006)... In our study, the individuals receiving longer daily sessions indeed spent more time in active, repetitive motor practice than those receiving shorter sessions, but treatment outcomes did not coherently reflect this... One could henceforth conclude that 90 minutes of daily training is enough... But we do not take this position... Furthermore, an increased fatigued status is also likely to negatively impact on motivation and compliance, which in our study could have not only contributed to aggravate an already existing condition of elevated perception of fatigue in the individuals exposed to the more intensive CI therapy protocol (see mechanisms of fatigue), but also directly affected their ability to engage with the training as well as their commitment to it.

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Related in: MedlinePlus

Hypothetical relationship between training intensity and outcomes in chronic hemiparetic stroke.This figure illustrates the modulation of the optimum session length/training intensity by residual recovery levels. Two assumptions are made. Firstly, as session length increases, performance also increases, until it reaches its peak; increasing session length further, however, results in performance deterioration, which presumably reflects the impact of fatigue. Secondly, in stroke survivors with low-functioning hemiparesis (red line), performance is not only lower in general, but critically, the optimum training intensity is reached earlier than in those with high-functioning hemiparesis (blue line). Optimum session length/training intensity: Mostly determined by both the level of residual recovery and the fatigued status an individual achieves. Of note, the latter is critically influenced by the first. Investigations of dosage effects in motor rehabilitation should, therefore, not only carefully consider the level of residual function, but also take measures of fatigue into consideration.
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Figure 1: Hypothetical relationship between training intensity and outcomes in chronic hemiparetic stroke.This figure illustrates the modulation of the optimum session length/training intensity by residual recovery levels. Two assumptions are made. Firstly, as session length increases, performance also increases, until it reaches its peak; increasing session length further, however, results in performance deterioration, which presumably reflects the impact of fatigue. Secondly, in stroke survivors with low-functioning hemiparesis (red line), performance is not only lower in general, but critically, the optimum training intensity is reached earlier than in those with high-functioning hemiparesis (blue line). Optimum session length/training intensity: Mostly determined by both the level of residual recovery and the fatigued status an individual achieves. Of note, the latter is critically influenced by the first. Investigations of dosage effects in motor rehabilitation should, therefore, not only carefully consider the level of residual function, but also take measures of fatigue into consideration.

Mentions: Motor rehabilitation after hemiparetic stroke is essential to soften physical disability (Furlan, 2014). Nevertheless, current interventions are mostly designed for well recovered individuals and often exclude stroke survivors with rather limited motor ability (Sterr and Conforto, 2012). Given that, and further advancing our research agenda in this arena (Sterr et al., 2002; Sterr and Freivogel, 2003, 2004; Sterr, 2004; Sterr et al., 2006; Sterr and Saunders, 2006), we recently tested the efficacy of a 2-week modified constraint-induced (CI) therapy program in chronic stroke individuals with very low-functioning upper limb hemiparesis (Sterr et al., 2014a). We tested the influence of both the intensity of daily motor training (90 vs. 180 minutes) and the restraint of the less affected upper limb (restraint vs. no restraint) on treatment outcomes. Sixty-five individuals were randomly assigned to four experimental conditions (90 minutes of training with or without restraint, and 180 minutes of training with or without restraint). They were assessed at baseline and after the intervention (2 weeks before, immediately before and after, 6, and 12 months after). Across the cohort, motor function improved significantly, and treatment benefits were largely sustained over the 12 months of follow-up. Analysis of the different treatment variants, however, revealed interesting yet unexpected findings, particularly with regards to the relationship between intensity (amount) of daily training and motor outcomes. As suggested by previous work (Sterr et al., 2002), longer sessions of daily training were expected to yield better outcomes than short sessions, a finding in line with the theory that massed practice is essential for neuroplasticity processes driving the functional improvements induced by CI therapy. However, this was not entirely the case. While we found some differences suggesting greater benefit of longer training sessions, the picture was not as clear as one might expect. This pointed to an interaction between training intensity and motor outcomes in low-functioning chronic stroke that appears to be different from that seen in less severe chronic hemiparesis, where the concept of ‘the more the better’ often holds true (Figure 1). We argued that this intensity-outcome relationship is moderated by variables that highly depend on the level of residual recovery. A key candidate for this moderation is fatigue. Fatigue is identified as rather common, yet obscure problem in stroke survivors (Wu et al., 2015). Post-stroke fatigue is multifactorial and seems to result from a complex interaction among biological, psychosocial, and behavioral factors (Wu et al., 2015). Here, we discuss the role of fatigue in motor rehabilitation of low-functioning chronic stroke using the framework recently suggested by Kluger et al. (2013). Although relatively different from, yet not antithetic to other fatigue models (e.g., Wu et al., 2015), we believe their framework provides conceptual and mechanistic support to our hypothesis. According to that framework, neurological, including post-stroke fatigue encompasses two domains: Perception of fatigue and fatigability. Perception of fatigue refers to a subjective sense of effort or exhaustion, whereas fatigability is related to an objective decline in performance. Although these two types of fatigue might be largely interrelated (e.g., an increased sense of effort would usually contribute to impair performance), they might also act independently and still significantly affect the individual's engagement with activities posing high motor and/or cognitive demands. This is because those two types of fatigue are likely to be caused by different, yet potentially interacting factors. For instance, perception of fatigue could be induced by homeostatic (e.g., metabolic stimuli, such as depletion of energy reserves in skeletal muscle and/or brain tissue) and/or psychological (e.g., decreased motivation) mechanisms, while fatigability could occur due to declines in skeletal muscle force production and/or deficits in task-related neural processing (Kluger et al., 2013). Based on that, we propose that low-functioning chronic stroke survivors are highly susceptible to get into a complex fatigued state, which renders motor training ineffective. This state is more likely to be reached by individuals undergoing longer training sessions. Essentially, we elaborate here on the possibility that a combination of general deconditioning and compromised neural processing might greatly increase both perception of fatigue and fatigability in those individuals, which substantially reduces their engagement with motor training and thereby decreases the likelihood for neuroplasticity processes driving behavioral improvements.


A case to be made: theoretical and empirical arguments for the need to consider fatigue in post-stroke motor rehabilitation.

Sterr A, Furlan L - Neural Regen Res (2015)

Hypothetical relationship between training intensity and outcomes in chronic hemiparetic stroke.This figure illustrates the modulation of the optimum session length/training intensity by residual recovery levels. Two assumptions are made. Firstly, as session length increases, performance also increases, until it reaches its peak; increasing session length further, however, results in performance deterioration, which presumably reflects the impact of fatigue. Secondly, in stroke survivors with low-functioning hemiparesis (red line), performance is not only lower in general, but critically, the optimum training intensity is reached earlier than in those with high-functioning hemiparesis (blue line). Optimum session length/training intensity: Mostly determined by both the level of residual recovery and the fatigued status an individual achieves. Of note, the latter is critically influenced by the first. Investigations of dosage effects in motor rehabilitation should, therefore, not only carefully consider the level of residual function, but also take measures of fatigue into consideration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590218&req=5

Figure 1: Hypothetical relationship between training intensity and outcomes in chronic hemiparetic stroke.This figure illustrates the modulation of the optimum session length/training intensity by residual recovery levels. Two assumptions are made. Firstly, as session length increases, performance also increases, until it reaches its peak; increasing session length further, however, results in performance deterioration, which presumably reflects the impact of fatigue. Secondly, in stroke survivors with low-functioning hemiparesis (red line), performance is not only lower in general, but critically, the optimum training intensity is reached earlier than in those with high-functioning hemiparesis (blue line). Optimum session length/training intensity: Mostly determined by both the level of residual recovery and the fatigued status an individual achieves. Of note, the latter is critically influenced by the first. Investigations of dosage effects in motor rehabilitation should, therefore, not only carefully consider the level of residual function, but also take measures of fatigue into consideration.
Mentions: Motor rehabilitation after hemiparetic stroke is essential to soften physical disability (Furlan, 2014). Nevertheless, current interventions are mostly designed for well recovered individuals and often exclude stroke survivors with rather limited motor ability (Sterr and Conforto, 2012). Given that, and further advancing our research agenda in this arena (Sterr et al., 2002; Sterr and Freivogel, 2003, 2004; Sterr, 2004; Sterr et al., 2006; Sterr and Saunders, 2006), we recently tested the efficacy of a 2-week modified constraint-induced (CI) therapy program in chronic stroke individuals with very low-functioning upper limb hemiparesis (Sterr et al., 2014a). We tested the influence of both the intensity of daily motor training (90 vs. 180 minutes) and the restraint of the less affected upper limb (restraint vs. no restraint) on treatment outcomes. Sixty-five individuals were randomly assigned to four experimental conditions (90 minutes of training with or without restraint, and 180 minutes of training with or without restraint). They were assessed at baseline and after the intervention (2 weeks before, immediately before and after, 6, and 12 months after). Across the cohort, motor function improved significantly, and treatment benefits were largely sustained over the 12 months of follow-up. Analysis of the different treatment variants, however, revealed interesting yet unexpected findings, particularly with regards to the relationship between intensity (amount) of daily training and motor outcomes. As suggested by previous work (Sterr et al., 2002), longer sessions of daily training were expected to yield better outcomes than short sessions, a finding in line with the theory that massed practice is essential for neuroplasticity processes driving the functional improvements induced by CI therapy. However, this was not entirely the case. While we found some differences suggesting greater benefit of longer training sessions, the picture was not as clear as one might expect. This pointed to an interaction between training intensity and motor outcomes in low-functioning chronic stroke that appears to be different from that seen in less severe chronic hemiparesis, where the concept of ‘the more the better’ often holds true (Figure 1). We argued that this intensity-outcome relationship is moderated by variables that highly depend on the level of residual recovery. A key candidate for this moderation is fatigue. Fatigue is identified as rather common, yet obscure problem in stroke survivors (Wu et al., 2015). Post-stroke fatigue is multifactorial and seems to result from a complex interaction among biological, psychosocial, and behavioral factors (Wu et al., 2015). Here, we discuss the role of fatigue in motor rehabilitation of low-functioning chronic stroke using the framework recently suggested by Kluger et al. (2013). Although relatively different from, yet not antithetic to other fatigue models (e.g., Wu et al., 2015), we believe their framework provides conceptual and mechanistic support to our hypothesis. According to that framework, neurological, including post-stroke fatigue encompasses two domains: Perception of fatigue and fatigability. Perception of fatigue refers to a subjective sense of effort or exhaustion, whereas fatigability is related to an objective decline in performance. Although these two types of fatigue might be largely interrelated (e.g., an increased sense of effort would usually contribute to impair performance), they might also act independently and still significantly affect the individual's engagement with activities posing high motor and/or cognitive demands. This is because those two types of fatigue are likely to be caused by different, yet potentially interacting factors. For instance, perception of fatigue could be induced by homeostatic (e.g., metabolic stimuli, such as depletion of energy reserves in skeletal muscle and/or brain tissue) and/or psychological (e.g., decreased motivation) mechanisms, while fatigability could occur due to declines in skeletal muscle force production and/or deficits in task-related neural processing (Kluger et al., 2013). Based on that, we propose that low-functioning chronic stroke survivors are highly susceptible to get into a complex fatigued state, which renders motor training ineffective. This state is more likely to be reached by individuals undergoing longer training sessions. Essentially, we elaborate here on the possibility that a combination of general deconditioning and compromised neural processing might greatly increase both perception of fatigue and fatigability in those individuals, which substantially reduces their engagement with motor training and thereby decreases the likelihood for neuroplasticity processes driving behavioral improvements.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology, University of Surrey, Guildford, UK ; Department of Neurology, University of Sao Paulo, Sao Paulo, Brazil.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Given that, and further advancing our research agenda in this arena (Sterr et al., 2002; Sterr and Freivogel, 2003, 2004; Sterr, 2004; Sterr et al., 2006; Sterr and Saunders, 2006), we recently tested the efficacy of a 2-week modified constraint-induced (CI) therapy program in chronic stroke individuals with very low-functioning upper limb hemiparesis (Sterr et al., 2014a)... They were assessed at baseline and after the intervention (2 weeks before, immediately before and after, 6, and 12 months after)... Across the cohort, motor function improved significantly, and treatment benefits were largely sustained over the 12 months of follow-up... As suggested by previous work (Sterr et al., 2002), longer sessions of daily training were expected to yield better outcomes than short sessions, a finding in line with the theory that massed practice is essential for neuroplasticity processes driving the functional improvements induced by CI therapy... However, this was not entirely the case... While we found some differences suggesting greater benefit of longer training sessions, the picture was not as clear as one might expect... This is likely to elevate both perception of fatigue and fatigability during motor activities by accelerating depletion of skeletal muscle energy reserves and causing rapid declines in force production, respectively... While the first is likely a compound of an impaired cardiorespiratory system – which may fail to effectively supply contracting muscles with oxygen and nutrients – and a deteriorated musculoskeletal function – in terms of reduced capillary density and oxidative capacity limiting muscle energy production –, the latter mostly results from an impaired neuro-musculoskeletal system, owing primarily to both a reduced ability to activate spinal motor units and skeletal muscle plastic changes... When combined to a physically demanding motor training regimen such as CI therapy, this may well have exacerbated perception of fatigue and fatigability in our sample... The CI therapy intervention is grounded on this principle (Morris and Taub, 2006)... In our study, the individuals receiving longer daily sessions indeed spent more time in active, repetitive motor practice than those receiving shorter sessions, but treatment outcomes did not coherently reflect this... One could henceforth conclude that 90 minutes of daily training is enough... But we do not take this position... Furthermore, an increased fatigued status is also likely to negatively impact on motivation and compliance, which in our study could have not only contributed to aggravate an already existing condition of elevated perception of fatigue in the individuals exposed to the more intensive CI therapy protocol (see mechanisms of fatigue), but also directly affected their ability to engage with the training as well as their commitment to it.

No MeSH data available.


Related in: MedlinePlus