Improving physical movement during stroke rehabilitation: investigating associations between sleep measured by wearable actigraphy technology, fatigue, and key biomarkers.

BACKGROUND: Sleep disturbance and fatigue are common in individuals undergoing inpatient rehabilitation following stroke. Understanding the relationships between sleep, fatigue, motor performance, and key biomarkers of inflammation and neuroplasticity could provide valuable insight into stroke recovery, possibly leading to personalized rehabilitation strategies. This study aimed to investigate the influence of sleep quality on motor function following stroke utilizing wearable technology to obtain objective sleep measurements. Additionally, we aimed to determine if there were relationships between sleep, fatigue, and motor function. Lastly, the study aimed to determine if salivary biomarkers of stress, inflammation, and neuroplasticity were associated with motor function or fatigue post-stroke. METHODS: Eighteen individuals who experienced a stroke and were undergoing inpatient rehabilitation participated in a cross-sectional observational study. Following consent, participants completed questionnaires to assess sleep patterns, fatigue, and quality of life. Objective sleep was measured throughout one night using the wearable Philips Actiwatch. Upper limb motor performance was assessed on the following day and saliva was collected for biomarker analysis. Correlation analyses were performed to assess the relationships between variables. RESULTS: Participants reported poor sleep quality, frequent awakenings, and difficulties falling asleep following stroke. We identified a significant negative relationship between fatigue severity and both sleep quality (r=-0.539, p = 0.021) and participants experience of awakening from sleep (r=-0.656, p = 0.003). A significant positive relationship was found between grip strength on the non-hemiplegic limb and salivary gene expression of Brain-derived Neurotrophic Factor (r = 0.606, p = 0.028), as well as a significant negative relationship between grip strength on the hemiplegic side and salivary gene expression of C-reactive Protein (r=-0.556, p = 0.048). CONCLUSION: The findings of this study emphasize the importance of considering sleep quality, fatigue, and biomarkers in stroke rehabilitation to optimize recovery and that interventions may need to be tailored to the individual. Future longitudinal studies are required to explore these relationships over time. Integrating wearable technology for sleep and biomarker analysis can enhance monitoring and prediction of outcomes following stroke, ultimately improving rehabilitation strategies and patient outcomes.

The Influence of Substance Use on Traumatic Brain Injury Recovery and Rehabilitation Outcomes: The Outcome-ABI Study.

OBJECTIVE: This study characterized substance use (alcohol, illicit drugs, amphetamines) in patients with traumatic brain injury (TBI) receiving rehabilitation to determine potential benefit of rehabilitation and whether substance use influenced outcomes in moderate-severe TBI. DESIGN: Prospective, longitudinal study of adults with moderate or severe TBI receiving inpatient rehabilitation. SETTING: Specialist-staffed acquired brain injury rehabilitation center in Melbourne, Australia. PARTICIPANTS: A total of 153 consecutive inpatients with TBI admitted between January 2016 and December 2017 (24 months). INTERVENTIONS: All inpatients with TBI (n=153) received specialist-provided brain injury rehabilitation in accordance with evidence-based guideline care at one 42-bed rehabilitation center. MAIN OUTCOME MEASURES: Data were collected at time of TBI, upon rehabilitation admission, and discharge and 12 months' post-TBI. Recovery was measured by posttraumatic amnesia posttraumatic amnesia length-days and change in Glasgow Coma Scale (admission-discharge). Functional independence was measured on the FIM, Functional Assessment Measure, and Mayo Portland Adaptability Index. Quality of life (QOL) was measured on the EuroQOL-5D-5L and Quality of Life After Brain Injury (QOLIBRI) instruments. RESULTS: Inpatients with history of illicit drug use (n=54) reported lower QOL and adjustment at 12 months' post-TBI compared with those with no history (QOLIBRI social relationships: ratio of means=0.808, P=.028; Mayo Portland Adaptability Index adjustment: incidence rate ratio, 1.273; P=.032). Amphetamine use at time of injury (n=10) was associated with quicker recovery (posttraumatic amnesia length-days: incidence rate ratio, 0.173; P<.01); however, lower QOL at 12 months post-TBI was noted in those with a history of amphetamine use (n=34) compared with those without (QOLIBRI bothered feelings: ratio of means, 0.489, P=.036). CONCLUSIONS: All participants made improvements with rehabilitation post-TBI; however, a history of substance use was associated with lower reported 12-month QOL. These findings add insight to the associations between substance use and acute recovery, potentially suggestive of a short-term recovery-promoting effect of amphetamines but highlighting the importance of rehabilitation to address long-term sequalae.

Perceptions of an Interactive Trauma Recovery Information Booklet.

BACKGROUND: Previous research has shown that people with traumatic injuries have unmet information needs with respect to their injuries, management, and recovery. An interactive trauma recovery information booklet was developed and implemented to address these information needs at a major trauma center in Victoria, Australia. OBJECTIVE: The aim of this quality improvement project was to explore patient and clinician perceptions of a recovery information booklet introduced into a trauma ward. METHODS: Semistructured interviews with trauma patients, family members, and health professionals were undertaken and thematically analyzed using a framework approach. In total, 34 patients, 10 family members, and 26 health professionals were interviewed. RESULTS: Overall, the booklet was well accepted by most participants and was perceived to contain useful information. The design, content, pictures, and readability were all positively appraised. Many participants used the booklet to record personalized information and to ask health professionals questions about their injuries and management. CONCLUSION: Our findings highlight the usefulness and acceptability of a low-cost interactive booklet intervention to facilitate the provision of quality of information and patient-health professional interactions on a trauma ward.

Measuring Sleep Quality in the Hospital Environment with Wearable and Non-Wearable Devices in Adults with Stroke Undergoing Inpatient Rehabilitation.

Sleep disturbances are common after stroke and may affect recovery and rehabilitation outcomes. Sleep monitoring in the hospital environment is not routine practice yet may offer insight into how the hospital environment influences post-stroke sleep quality while also enabling us to investigate the relationships between sleep quality and neuroplasticity, physical activity, fatigue levels, and recovery of functional independence while undergoing rehabilitation. Commonly used sleep monitoring devices can be expensive, which limits their use in clinical settings. Therefore, there is a need for low-cost methods to monitor sleep quality in hospital settings. This study compared a commonly used actigraphy sleep monitoring device with a low-cost commercial device. Eighteen adults with stroke wore the Philips Actiwatch to monitor sleep latency, sleep time, number of awakenings, time spent awake, and sleep efficiency. A sub-sample (n = 6) slept with the Withings Sleep Analyzer in situ, recording the same sleep parameters. Intraclass correlation coefficients and Bland-Altman plots indicated poor agreement between the devices. Usability issues and inconsistencies were reported between the objectively measured sleep parameters recorded by the Withings device compared with the Philips Actiwatch. While these findings suggest that low-cost devices are not suitable for use in a hospital environment, further investigations in larger cohorts of adults with stroke are needed to examine the utility and accuracy of off-the-shelf low-cost devices to monitor sleep quality in the hospital environment.

The Use of Collagen Methacrylate in Actuating Polyethylene Glycol Diacrylate-Acrylic Acid Scaffolds for Muscle Regeneration.

After muscle loss or injury, skeletal muscle tissue has the ability to regenerate and return its function. However, large volume defects in skeletal muscle tissue pose a challenge to regenerate due to the absence of regenerative elements such as biophysical and biochemical cues, making the development of new treatments necessary. One potential solution is to utilize electroactive polymers that can change size or shape in response to an external electric field. Poly(ethylene glycol) diacrylate (PEGDA) is one such polymer, which holds great potential as a scaffold for muscle tissue regeneration due to its mechanical properties. In addition, the versatile chemistry of this polymer allows for the conjugation of new functional groups to enhance its electroactive properties and biocompatibility. Herein, we have developed an electroactive copolymer of PEGDA and acrylic acid (AA) in combination with collagen methacrylate (CMA) to promote cell adhesion and proliferation. The electroactive properties of the CMA + PEGDA:AA constructs were investigated through actuation studies. Furthermore, the biological properties of the hydrogel were investigated in a 14-day in vitro study to evaluate myosin light chain (MLC) expression and metabolic activity of C2C12 mouse myoblast cells. The addition of CMA improved some aspects of material bioactivity, such as MLC expression in C2C12 mouse myoblast cells. However, the incorporation of CMA in the PEGDA:AA hydrogels reduced the sample movement when placed under an electric field, possibly due to steric hindrance from the CMA. Further research is needed to optimize the use of CMA in combination with PEGDA:AA as a potential scaffold for skeletal muscle tissue engineering.

In vitro studies of Annona muricata L. extract-loaded electrospun scaffolds for localized treatment of breast cancer.

This paper presents in vitro studies of the sustained release of Annona muricata leaf extracts (AME) from hybrid electrospun fibers for breast cancer treatment. Electrospun hybrid scaffolds were fabricated from crude AME extracts, poly(lactic-co-glycolic acid)/gelatin (PLGA/Ge) and pluronic F127. The physicochemical properties of the AME extract and scaffolds were studied. The antiproliferative effects of the scaffolds were also assessed on breast cancer (MCF-7 and MDA-MB-231) and non-tumorigenic breast (MCF10A) cell lines. Scanning electron microscope micrographs revealed a random network of micro- and submicron fibers. In vitro drug release profiles, governed by quasi-Fickian diffusion at pH 7.4 and non-Fickian super case II at pH 6.7, showed initial burst AME release from the PLGA/Ge-AME and PLGA/Ge-F127/AME fibers at pH 7.4, and burst release from PLGA/Ge-F127/AME (not observed from PLGA/Ge-AME) at pH 6.7. Then, a slower, sustained release of the remaining AME from the fibers, attributed to the onset of degradation of the PLGA/Ge backbone, was observed for the next 72 hr. The cumulative release of AME was 89.33 ± 0.73% (PLGA/Ge-AME) and 51.17 ± 7.96% (PLGA/Ge-F127/AME) at pH 7.4, and 9.27 ± 2.3% and 73.5 ± 4.5%, respectively, at pH 6.7. Pluronic F127 addition increased the drug loading capacity and prolonged the sustained AME release from the fibers. The released AME significantly inhibited the in vitro growth of the breast cancer cells more than the non-tumorigenic cells, due to the induction of apoptosis, providing evidence for using pluronic F127-containing electrospun fibers for sustained and localized AME delivery to breast cancer cells.

The effects of transcranial direct current stimulation on corticospinal and cortico-cortical excitability and response variability: Conventional versus high-definition montages.

Response variability following transcranial direct current stimulation (tDCS) highlights need for exploring different tDCS electrode montages. Corticospinal excitability (CSE), cortico-cortical excitability and intra-individual variability was compared following conventional and high-definition (HD) anodal (a-tDCS) and cathodal (c-tDCS) tDCS. Fifteen healthy males attended four sessions at-least one-week apart: conventional a-tDCS, conventional c-tDCS, HD-a-tDCS, HD-c-tDCS. TDCS was administered (1 mA, 10-minutes) over primary motor cortex (M1), via 6 × 4 cm active and 7 × 5 cm return electrodes (conventional tDCS) and 4 × 1 ring-electrodes 3.5 cm apart over M1 (HD-tDCS). For CSE, twenty-five single-pulse transcranial magnetic stimulation (TMS) peak-to-peak motor evoked potentials (MEP) were recorded at baseline, 0-minutes and 30-minutes post-tDCS. Twenty-five paired-pulse MEPs with 3-millisecond (ms) inter-pulse interval (IPI) and twenty-five at 10 ms assessed short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). MEP standardised z-values standard deviations represented intra-individual variability. No significant changes in CSE from baseline were reported for all four interventions. No significant differences were reported in CSE between conventional and HD a-tDCS, but significant differences between conventional and HD c-tDCS 0-minutes post-tDCS. Conventional tDCS significantly reduced intra-individual variability compared to HD-tDCS for a-tDCS (0-minutes) and c-tDCS (30-minutes). No changes were reported for SICI/ICF. These novel findings of increased intra-individual variability following HD-tDCS, at the current stimulus parameters, highlight need for further nuanced research and refinement to optimise the HD-tDCS dosage-response relationship.

Can genetic polymorphisms predict response variability to anodal transcranial direct current stimulation of the primary motor cortex?

Genetic mediation of cortical plasticity and the role genetic variants play in previously observed response variability to transcranial direct current stimulation (tDCS) have become important issues in the tDCS literature in recent years. This study investigated whether inter-individual variability to tDCS was in-part genetically mediated. In 61 healthy males, anodal-tDCS (a-tDCS) and sham-tDCS were administered to the primary motor cortex at 1 mA for 10-min via 6 × 4 cm active and 7 × 5 cm return electrodes. Twenty-five single-pulse transcranial magnetic stimulation (TMS) motor evoked potentials (MEP) were recorded to represent corticospinal excitability (CSE). Twenty-five paired-pulse MEPs were recorded with 3 ms inter-stimulus interval (ISI) to assess intracortical inhibition (ICI) via short-interval intracranial inhibition (SICI) and 10 ms ISI for intracortical facilitation (ICF). Saliva samples were tested for specific genetic polymorphisms in genes encoding for excitatory and inhibitory neuroreceptors. Individuals were sub-grouped based on a pre-determined threshold and via statistical cluster analysis. Two distinct subgroups were identified, increases in CSE following a-tDCS (i.e. Responders) and no increase or even reductions in CSE (i.e. Non-responders). No changes in ICI or ICF were reported. No relationships were reported between genetic polymorphisms in excitatory receptor genes and a-tDCS responders. An association was reported between a-tDCS responders and GABRA3 gene polymorphisms encoding for GABA-A receptors suggesting potential relationships between GABA-A receptor variations and capacity to undergo tDCS-induced cortical plasticity. In the largest tDCS study of its kind, this study presents an important step forward in determining the contribution genetic factors play in previously observed inter-individual variability to tDCS.

Genetic Polymorphisms Do Not Predict Interindividual Variability to Cathodal Transcranial Direct Current Stimulation of the Primary Motor Cortex.

Introduction: High variability between individuals (i.e., interindividual variability) in response to transcranial direct current stimulation (tDCS) has become a commonly reported issue in the tDCS literature in recent years. Inherent genetic differences between individuals have been proposed as a contributing factor to observed response variability. This study investigated whether tDCS interindividual variability was genetically mediated. Methods: A large sample size of 61 healthy males received cathodal tDCS (c-tDCS) and sham-tDCS of the primary motor cortex at 1 mA and 10 min via 6 × 4 cm active and 7 × 5 cm return electrodes. Corticospinal excitability (CSE) was assessed via 25 single-pulse transcranial magnetic stimulation motor-evoked potentials (MEPs). Intracortical inhibition was assessed via twenty-five 3 msec interstimulus interval (ISI) paired-pulse MEPs, known as short-interval intracortical inhibition (SICI). Intracortical facilitation (ICF) was assessed via twenty-five 10 msec ISI paired-pulse MEPs. Gene variants encoding for excitatory and inhibitory neuroreceptors were determined via saliva samples. Predetermined thresholds and statistical cluster analyses were used to subgroup individuals. Results: Two distinct subgroups were identified, "responders" reducing CSE following c-tDCS and "nonresponders" showing no reduction or even increase in CSE. Differences in CSE between responders and nonresponders following c-tDCS were not explained by changes in SICI or ICF. Conclusions: No significant relationships were reported between gene variants and interindividual variability to c-tDCS, suggesting that the chosen gene variants did not influence the activity of the neuroreceptors involved in eliciting changes in CSE in responders following c-tDCS. In this largest c-tDCS study of its kind, novel insights were reported into the contribution genetic factors may play in observed interindividual variability to c-tDCS. Impact statement This study adds insight into the issue of interindividual variability to c-tDCS. It highlights not all individuals respond to c-tDCS similarly when exposed to the same stimulus parameters. This disparity in response to c-tDCS between individuals does not appear to be genetically mediated. For c-tDCS to progress to large-scale clinical application, reliability, predictability and reproducibility are essential. Systematically investigating factors contributing to interindividual variability take steps towards this progress the c-tDCS field towards the potential development of screening tools to determine clinical suitability to c-tDCS to ensure its application in those who may benefit the most.

A Checklist to Reduce Response Variability in Studies Using Transcranial Magnetic Stimulation for Assessment of Corticospinal Excitability: A Systematic Review of the Literature.

Response variability between individuals (interindividual variability) and within individuals (intraindividual variability) is an important issue in the transcranial magnetic stimulation (TMS) literature. This has raised questions of the validity of TMS to assess changes in corticospinal excitability (CSE) in a predictable and reliable manner. Several participant-specific factors contribute to this observed response variability with a current lack of consensus on the degree each factor contributes. This highlights a need for consistency and structure in reporting study designs and methodologies. Currently, there is no summarized review of the participant-specific factors that can be controlled and may contribute to response variability. This systematic review aimed to develop a checklist of methodological measures taken by previously published research to increase the homogeneity of participant selection criteria, preparation of participants before experimental testing, participant scheduling, and the instructions given to participants throughout experimental testing to minimize their effect on response variability. Seven databases were searched in full. Studies were included if CSE was measured via TMS and included methodological measures to increase the homogeneity of the participants. Eighty-four studies were included. Twenty-three included measures to increase participant selection homogeneity, 21 included measures to increase participant preparation homogeneity, while 61 included measures to increase participant scheduling and instructions during experimental testing homogeneity. These methodological measures were summarized into a user-friendly checklist with considerations, suggestions, and rationale/justification for their inclusion. This may provide the framework for further insights into ways to reduce response variability in TMS research.

Characterization of a prevascularized biomimetic tissue engineered scaffold for bone regeneration.

Significant bone loss due to disease or severe injury can result in the need for a bone graft, with over 500,000 procedures occurring each year in the United States. However, the current standards for grafting, autografts and allografts, can result in increased patient morbidity or a high rate of failure respectively. An ideal alternative would be a biodegradable tissue engineered graft that fulfills the function of bone while promoting the growth of new bone tissue. We developed a prevascularized tissue engineered scaffold of electrospun biodegradable polymers PLLA and PDLA reinforced with hydroxyapatite, a mineral similar to that found in bone. A composite design was utilized to mimic the structure and function of human trabecular and cortical bone. These scaffolds were characterized mechanically and in vitro to determine osteoinductive and angioinductive properties. It was observed that further reinforcement is necessary for the scaffolds to mechanically match bone, but the scaffolds are successful at inducing the differentiation of mesenchymal stem cells into mature bone cells and vascular endothelial cells. Prevascularization was seen to have a positive effect on angiogenesis and cellular metabolic activity, critical factors for the integration of a graft.

Single-walled carbon nanohorns modulate tenocyte cellular response and tendon biomechanics.

Subfailure ligament and tendon injury remain a significant burden to global healthcare. Here, we present the use of biocompatible single-walled carbon nanohorns (CNH) as a potential treatment for the repair of sub-failure injury in tendons. First, in vitro exposure of CNH to human tenocytes revealed no change in collagen deposition but a significant decrease in cell metabolic activity after 14 days. Additionally, gene expression studies revealed significant downregulation of collagen Types I and III mRNA at 7 days with some recovery after 14 days of exposure. Biomechanical tests with explanted porcine digitorum tendons showed the ability of CNH suspensions to modulate tendon biomechanics, most notably elastic moduli immediately after treatment. in vivo experiments demonstrated the ability of CNH to persist in the damaged matrix of stretch-injured Sprague Dawley rat Achilles tendon but not significantly modify tendon biomechanics after 7 days of treatment. Although these results demonstrate the early feasibility of utility of CNH as a potential modality for tendon subfailure injury, additional work is needed to further validate and ensure clinical efficacy.

The effect of transcranial magnetic stimulation test intensity on the amplitude, variability and reliability of motor evoked potentials.

High degrees of variability reported in Transcranial magnetic stimulation (TMS) assessment of corticospinal excitability (CSE) highlight the need to investigate its reliability as an assessment tool. This study investigated the effect of TMS test intensity on the amplitude, variability and test-retest reliability of motor evoked potentials (MEP). Twenty-five MEPs were recorded at 105%, 120%, 135%, 150% and 165% of resting motor threshold across three sessions in twelve participants. Repeated measures analysis of variance (RM-ANOVA), recruitment curve gradients and standardised z-value SDs were utilized to investigate the effect of TMS test intensity on MEP amplitude and variability. Test-retest reliability of MEP amplitude was assessed using RM-ANOVA and intraclass correlations (ICC). RM-ANOVA reported MEP amplitude significantly increased between 105-120% and 120-135% with non-significant increases thereafter. Recruitment curve gradients reduced as TMS test intensity increased. Standardised z-value SDs reported MEP amplitude variability reduced as TMS test intensity increased with the only significant reduction occurring between 120% and 135%. RM-ANOVA reported no significant effect of time on MEP amplitude, indicating agreement between sessions. ICCs indicated significant intra- and inter-session reliability for all TMS test intensities except for 105%. The only significant reduction in variability and final significant increase in MEP amplitude occurred between the same TMS test intensities. Reduced variability and increased reliability at higher TMS test intensities validate the use of higher TMS test intensities to assess changes in CSE in future research. To increase accuracy in capturing true changes in CSE we recommend assessing changes in CSE across a range of TMS test intensities.

Cluster analysis and subgrouping to investigate inter-individual variability to non-invasive brain stimulation: a systematic review.

Cluster analysis and other subgrouping techniques have risen in popularity in recent years in non-invasive brain stimulation research in the attempt to investigate the issue of inter-individual variability - the issue of why some individuals respond, as traditionally expected, to non-invasive brain stimulation protocols and others do not. Cluster analysis and subgrouping techniques have been used to categorise individuals, based on their response patterns, as responder or non-responders. There is, however, a lack of consensus and consistency on the most appropriate technique to use. This systematic review aimed to provide a systematic summary of the cluster analysis and subgrouping techniques used to date and suggest recommendations moving forward. Twenty studies were included that utilised subgrouping techniques, while seven of these additionally utilised cluster analysis techniques. The results of this systematic review appear to indicate that statistical cluster analysis techniques are effective in identifying subgroups of individuals based on response patterns to non-invasive brain stimulation. This systematic review also reports a lack of consensus amongst researchers on the most effective subgrouping technique and the criteria used to determine whether an individual is categorised as a responder or a non-responder. This systematic review provides a step-by-step guide to carrying out statistical cluster analyses and subgrouping techniques to provide a framework for analysis when developing further insights into the contributing factors of inter-individual variability in response to non-invasive brain stimulation.

Biological and anatomical factors influencing interindividual variability to noninvasive brain stimulation of the primary motor cortex: a systematic review and meta-analysis.

Noninvasive brain stimulation (NIBS) modifies corticospinal excitability (CSE) historically in a predictable manner dependent on stimulation parameters. Researchers, however, discuss high degrees of variability between individuals, either responding as expected or not responding as expected. The explanation for this interindividual variability remains unknown with suggested interplay between stimulation parameters and variations in biological, anatomical, and physiological factors. This systematic review and meta-analysis aimed to investigate the effect of variation in inherent factors within an individual (biological and anatomical factors) on CSE in response to NIBS of the primary motor cortex. Twenty-two studies were included investigating genetic variation (n=7), age variation (n=4), gender variation (n=7), and anatomical variation (n=5). The results indicate that variation in brain-derived neurotrophic factor genotypes may have an effect on CSE after NIBS. Variation between younger and older adults also affects CSE after NIBS. Variation between age-matched males and females does not affect CSE after NIBS, but variation across the menstrual cycle does. Variation between skull thickness and brain tissue morphology influences the electric field magnitude that ultimately reaches the primary motor cortex. These findings indicate that biological and anatomical variations may in part account for interindividual variability in CSE in response to NIBS of the primary motor cortex, categorizing individuals as responding as expected (responders) or not responding as expected (nonresponders).

The Effect of Swelling Ratio on the Coulter Underestimation of Hydrogel Microsphere Diameters.

It has been demonstrated that the diameters of porous particles are underestimated by Coulter measurements. This phenomenon has also been observed in hydrogel particles, but not characterized. Since the Coulter principle uses the displacement of electrolyte to determine particle size, electrolyte contained within the swelled hydrogel microparticles results in an underestimate of actual particle diameters. The increased use of hydrogel microspheres in biomedical applications has led to the increased application of the Coulter principle to evaluate the size distribution of microparticles. A relationship between the swelling ratio of the particles and their reported Coulter diameters will permit calculation of the actual diameters of these particles. Using polyethylene glycol diacrylate hydrogel microspheres, we determined a correction factor that relates the polymer swelling ratio and the reported Coulter diameters to their actual size.

Voluntary activation of the ankle plantar flexors following whole-body vibration.

This study investigated the effect of whole-body vibration (WBV) on the voluntary activation of the ankle plantar flexors. Twelve healthy young adults were randomly exposed to two treatments on separate occasions. The first (non-WBV) involved stretching of the plantar flexors at end range of dorsiflexion for five 1-min bouts. The second involved the same stretch with WBV (26 Hz) for five 1-min bouts. Attempted maximal voluntary contractions (AMVCs) of the plantar flexors were performed on an isokinetic dynamometer (30 degrees s(-1)) before and after each treatment. A twitch interpolation technique was used to investigate voluntary activation. Post-treatment data were normalised against pre-treatment data. Subjects were classified as maximally (n = 6) or sub-maximally (n = 6) activated using the pre-treatment twitch interpolation data. The effects of WBV were assessed by repeated measure (RM) MANOVA. After WBV, the group of subjects classified as sub-maximally activated increased peak voluntary torque and rate of voluntary torque production (P < 0.05), whereas angular displacement to peak torque reduced (P < 0.05); i.e. peak torque was produced at a longer muscle length. No significant non-WBV treatment effects were found for this group. No significant WBV effects were found for the group of subjects classified as maximally activated. This study found that the response to WBV was dependent on the level of voluntary activation of the ankle plantar flexors during a set of AMVCs.