The acute effects of aerobic exercise on sensorimotor adaptation in chronic stroke

Measuring Neuroplasticity in Response to Cardiovascular Exercise in People With Stroke: A Critical Perspective

BACKGROUND

Rehabilitative treatments that promote neuroplasticity are believed to improve recovery after stroke. Animal studies have shown that cardiovascular exercise (CE) promotes neuroplasticity but the effects of this intervention on the human brain and its implications for the functional recovery of patients remain unclear. The use of biomarkers has enabled the assessment of cellular and molecular events that occur in the central nervous system after brain injury. Some of these biomarkers have proven to be particularly valuable for the diagnosis of severity, prognosis of recovery, as well as for measuring the neuroplastic response to different treatments after stroke.

OBJECTIVES

To provide a critical analysis on the current evidence supporting the use of neurophysiological, neuroimaging, and blood biomarkers to assess the neuroplastic response to CE in individuals poststroke.

RESULTS

Most biomarkers used are responsive to the effects of acute and chronic CE interventions, but the response appears to be variable and is not consistently associated with functional improvements. Small sample sizes, methodological variability, incomplete information regarding patient's characteristics, inadequate standardization of training parameters, and lack of reporting of associations with functional outcomes preclude the quantification of the neuroplastic effects of CE poststroke using biomarkers.

CONCLUSION

Consensus on the optimal biomarkers to monitor the neuroplastic response to CE is currently lacking. By addressing critical methodological issues, future studies could advance our understanding of the use of biomarkers to measure the impact of CE on neuroplasticity and functional recovery in patients with stroke.

Enhancing Neuroplasticity in the Chronic Phase After Stroke: Effects of a Soft Robotic Exosuit on Training Intensity and Brain-Derived Neurotrophic Factor

Objective: High intensity training may enhance neuroplasticity after stroke; however, gait deficits limit the ability to achieve and sustain high walking training intensities. We hypothesize that soft robotic exosuits can facilitate speed-based gait training at higher intensities and longer durations, resulting in a corresponding increase in circulating brain-derived neurotrophic factor (BDNF). Results: Eleven individuals >6-mo post-stroke completed a two-session, pilot randomized crossover trial (NCT05138016). Maximum training speed (Δ: 0.07 ± 0.03 m/s), duration (Δ: 2.07 ± 0.88 min), and intensity (VO2 peak, Δ: 1.75 ± 0.60 ml-O2/kg/min) significantly increased (p < 0.05) during exosuit-augmented training compared to no-exosuit training. Post-session increases in BDNF (Δ: 5.96 ± 2.27 ng/ml, p = 0.03) were observed only after exosuit-augmented training. Biomechanical changes were not observed after exosuit-augmented training; however, a deterioration in gait propulsion symmetry (%Δ: -5 ± 2 %) and an increase in nonparetic propulsion (Δ: 0.9 ± 0.3 %bw) were observed (p < 0.05) after no-exosuit training. Conclusion: Soft robotic exosuits facilitate faster, longer duration, and higher intensity walking training associated with enhanced neuroplasticity.

Effects of an Acute High Intensity Exercise Bout on Retention of Explicit, Strategic Locomotor Learning in Individuals With Chronic Stroke

BACKGROUND

Exercise priming, pairing high intensity exercise with a motor learning task, improves retention of upper extremity tasks in individuals after stroke, but has shown no benefit to locomotor learning. This difference may relate to the type of learning studied. Upper extremity studies used explicit, strategic tasks; locomotor studies used implicit sensorimotor adaptation (split-belt treadmill). Since walking is an important rehabilitation goal, it is crucial to understand under which circumstances exercise priming may improve retention of a newly learned walking pattern.

OBJECTIVE

Determine the impact of exercise priming on explicit, strategic locomotor learning task retention in chronic stroke survivors.

METHODS

Chronic stroke survivors (>6 months) performed 2 treadmill walking sessions. Visual feedback was used to train increased step length. Participants were assigned to control group (no exercise), continuous exercise (5 minutes high intensity), or long-interval exercise (15 minutes high/moderate intervals). After day 1 learning, participants either rested or performed exercise. On day 2, retention of the learned walking pattern was tested.

RESULTS

All groups learned on day 1 (P < .001). The 2 priming groups showed significant changes in blood lactate and heart rate after exercise priming, the resting control group did not (P < .001). On day 2, there was no significant between-group difference in cued or un-cued task retention (P = .963 and .287, respectively).

CONCLUSIONS

Exercise priming did not affect retention of an explicit locomotor task in chronic stroke survivors. Further work should explore subgroups of individuals for whom priming may have selective clinical benefit to locomotor learning.ClinicalTrials.gov Identifier: NCT03726047.

Moderate-intensity cardiovascular exercise performed before motor practice attenuates offline implicit motor learning in stroke survivors but not age-matched neurotypical adults

The acute impact of cardiovascular exercise on implicit motor learning of stroke survivors is still unknown. We investigated the effects of cardiovascular exercise on implicit motor learning of mild-moderately impaired chronic stroke survivors and neurotypical adults. We addressed whether exercise priming effects are time-dependent (e.g., exercise before or after practice) in the encoding (acquisition) and recall (retention) phases. Forty-five stroke survivors and 45 age-matched neurotypical adults were randomized into three sub-groups: BEFORE (exercise, then motor practice), AFTER (motor practice, then exercise), and No-EX (motor practice alone). All sub-groups practiced a serial reaction time task (five repeated and two pseudorandom sequences per day) on three consecutive days, followed 7 days later by a retention test (one repeated sequence). Exercise was performed on a stationary bike, (one 20-min bout per day) at 50% to 70% heart rate reserve. Implicit motor learning was measured as a difference score (repeated-pseudorandom sequence response time) during practice (acquisition) and recall (delayed retention). Separate analyses were performed on the stroke and neurotypical groups using linear mixed-effects models (participant ID was a random effect). There was no exercise-induced benefit on implicit motor learning for any sub-group. However, exercise performed before practice impaired encoding in neurotypical adults and attenuated retention performance of stroke survivors. There is no benefit to implicit motor learning of moderately intense cardiovascular exercise for stroke survivors or age-matched neurotypical adults, regardless of timing. Practice under a high arousal state and exercise-induced fatigue may have attenuated offline learning in stroke survivors.

High-intensity training with short and long intervals regulate cortical neurotrophic factors, apoptosis markers and chloride homeostasis in rats with stroke

BACKGROUND/PURPOSE

The optimal endurance exercise parameters remain to be defined to potentiate long-term functional recovery after stroke. We aim to assess the effects of individualized high-intensity interval training (HIIT) with either long or short intervals on neurotrophic factors and their receptors, apoptosis markers and the two-main cation-chloride cotransporters in the ipsi- and contralesional cerebral cortices in rats with cerebral ischemia. Endurance performance and sensorimotor functions were also assessed METHODS: : Rats with a 2-hour transient middle cerebral artery occlusion (tMCAO) performed work-matched HIIT4 (intervals: 4min) or HIIT1 (intervals: 1min) on treadmill for 2 weeks. Incremental exercises and sensorimotor tests were performed at day 1 (D1), D8, and D15 after tMCAO. Molecular analyses were achieved in both the paretic and non-paretic triceps brachii muscles and the ipsi- and contralesional cortices at D17 RESULTS: : Gains in endurance performance are in a time-dependent manner from the first week of training. This enhancement is supported by the upregulation of metabolic markers in both triceps brachii muscles. Both regimens alter the expression of neurotrophic markers and chloride homeostasis in a specific manner in the ipsi- and contralesional cortices. HIIT acts on apoptosis markers by promoting anti-apoptotic proteins in the ipsilesional cortex CONCLUSION: : HIIT regimens seem to be of clinical relevance in the critical period of stroke rehabilitation by strongly improving aerobic performance. Also, the observed cortical changes suggest an influence of HIIT on neuroplasticity in both ipsi- and contralesional hemispheres. Such neurotrophic markers might be considered as biomarkers of functional recovery in individuals with stroke.

A Systematic Review on the Effects of Acute Aerobic Exercise on Neurophysiological, Molecular, and Behavioral Measures in Chronic Stroke

BACKGROUND

A single bout of aerobic exercise (AE) can produce changes in neurophysiological and behavioral measures in healthy individuals and those with stroke. However, the effects of AE-priming effects on neuroplasticity markers and behavioral measures are unclear.

OBJECTIVES

This systematic review aimed to examine the effects of AE on neuroplasticity measures, such as corticomotor excitability (CME), molecular markers, cortical activation, motor learning, and performance in stroke.

METHODS

A literature search was performed in MEDLINE, CINAHL, Scopus, and PsycINFO databases. Randomized and non-randomized studies incorporating acute AE in stroke were selected. Two reviewers independently assessed the risk of bias and methodological rigor of the studies and extracted data on participant characteristics, exercise interventions, and neuroplasticity related outcomes. The quality of transcranial magnetic stimulation reported methods was assessed using a standardized checklist.

RESULTS

A total of 16 studies were found suitable for inclusion. Our findings suggest mixed evidence for the effects of AE on CME, limited to no effects on intracortical inhibition and facilitation and some evidence for modulating brain derived neurotrophic factor levels, motor learning, and cortical activation. Exercise intensities in the moderate to vigorous range showed a trend towards better effects on neuroplasticity measures.

CONCLUSION

It appears that choosing a moderate to vigorous exercise paradigm for at least 20 to 30 minutes may induce changes in some neuroplasticity parameters in stroke. However, these findings necessitate prudent consideration as the studies were diverse and had moderate methodological quality. There is a need for a consensus on an exercise priming paradigm and for good-quality, larger controlled studies.

Optimal Intervention Timing for Robotic-Assisted Gait Training in Hemiplegic Stroke

This study was designed to determine the best intervention time (acute, subacute, and chronic stages) for Walkbot robot-assisted gait training (RAGT) rehabilitation to improve clinical outcomes, including sensorimotor function, balance, cognition, and activities of daily living, in hemiparetic stroke patients. Thirty-six stroke survivors (acute stage group (ASG), n = 11; subacute stage group (SSG), n = 15; chronic stage group (CSG), n = 10) consistently received Walkbot RAGT for 30 min/session, thrice a week, for 4 weeks. Six clinical outcome variables, including the Fugl–Meyer Assessment (FMA), Berg Balance Scale (BBS), Trunk Impairment Scale (TIS), Modified Barthel Index (MBI), Modified Ashworth Scale (MAS), and Mini-Mental State Examination, were examined before and after the intervention. Significant differences in the FMA, BBS, TIS, and MBI were observed between the ASG and the SSG or CSG. A significant time effect was observed for all variables, except for the MAS, in the ASG and SSG, whereas significant time effects were noted for the FMA, BBS, and TIS in the CSG. Overall, Walkbot RAGT was more favorable for acute stroke patients than for those with subacute or chronic stroke. This provides the first clinical evidence for the optimal intervention timing for RAGT in stroke.