Improvement of Saccadic Eye Movements after Head-Eye Vestibular Motion (HEVM) Therapy and Neuro-Psychiatric Considerations.

INTRODUCTION: Eye movement pathology can assist in the identification, diagnosis and treatment of mental health disorders. Eye-tracking paradigms have been utilized to provide greater ecological validity, and directly capture the detailed sequence of processes in perception and attention, while quantifying classifiers in mood, anxiety, and psychotic disorders. Saccadic eye movements serve as an endophenotype for various mental health disorders. SUBJECTS AND METHODS: Patients suffering from post-concussive syndrome and mental health concerns performed saccadic eye movements that were quantified for amplitude, velocity, latency and accuracy before and after Head-Eye Vestibular Motion therapy (HEVM). RESULTS: HEVM therapy is associated with statistical and substantive significant improvements in mental health and in saccadic metrics. CONCLUSIONS: Oculomotor dysfunction is related to the symptom dimensions of mental health disorders that may be treated with physical rehabilitation modalities. We feel it reasonable to suggest that psychiatrists and others involved in the treatment of mental health disorders quantify eye movements and use them as biomarkers in the evaluation of the outcomes of varied therapies.

The Pupillary Light Reflex as a Biomarker of Concussion.

The size of our pupils changes continuously in response to variations in ambient light levels, a process known as the pupillary light reflex (PLR). The PLR is not a simple reflex as its function is modulated by cognitive brain function and any long-term changes in brain function secondary to injury should cause a change in the parameters of the PLR. We performed a retrospective clinical review of the PLR of our patients using the BrightLamp Reflex iPhone app. The PLR variables of latency, maximum pupil diameter (MaxPD), minimum pupil diameter (MinPD), maximum constriction velocity (MCV), and the 75% recovery time (75% PRT) were associated with significant differences between subjects who had suffered a concussion and those that had not. There were also significant differences in PLR metrics over the life span and between genders and those subjects with and without symptoms. The differences in PLR metrics are modulated not only by concussion history but also by gender and whether or not the person has symptoms associated with a head injury. A concussive injury to the brain is associated with changes in the PLR that persist over the life span, representing biomarkers that might be used in clinical diagnosis, treatment, and decision making.

Brain Vital Signs in Elite Ice Hockey: Towards Characterizing Objective and Specific Neurophysiological Reference Values for Concussion Management.

Background: Prior concussion studies have shown that objective neurophysiological measures are sensitive to detecting concussive and subconcussive impairments in youth ice-hockey. These studies monitored brain vital signs at rink-side using a within-subjects design to demonstrate significant changes from pre-season baseline scans. However, practical clinical implementation must overcome inherent challenges related to any dependence on a baseline. This requires establishing the start of normative reference data sets. Methods: The current study collected specific reference data for N = 58 elite, youth, male ice-hockey players and compared these with a general reference dataset from N = 135 of males and females across the lifespan. The elite hockey players were recruited to a select training camp through CAA Hockey, a management agency for players drafted to leagues such as the National Hockey League (NHL). The statistical analysis included a test-retest comparison to establish reliability, and a multivariate analysis of covariance to evaluate differences in brain vital signs between groups with age as a covariate. Findings: Test-retest assessments for brain vital signs evoked potentials showed moderate-to-good reliability (Cronbach's Alpha > 0.7, Intraclass correlation coefficient > 0.5) in five out of six measures. The multivariate analysis of covariance showed no overall effect for group (p = 0.105), and a significant effect of age as a covariate was observed (p < 0.001). Adjusting for the effect of age, a significant difference was observed in the measure of N100 latency (p = 0.022) between elite hockey players and the heterogeneous control group. Interpretation: The findings support the concept that normative physiological data can be used in brain vital signs evaluation in athletes, and should additionally be stratified for age, skill level, and experience. These can be combined with general norms and/or individual baseline assessments where appropriate and/or possible. The current results allow for brain vital sign evaluation independent of baseline assessment, therefore enabling objective neurophysiological evaluation of concussion management and cognitive performance optimization in ice-hockey.

Head Position and Posturography: A Novel Biomarker to Identify Concussion Sufferers.

Balance control systems involve complex systems directing muscle activity to prevent internal and external influences that destabilize posture, especially when body positions change. The computerized dynamic posturography stability score has been established to be the most repeatable posturographic measure using variations of the modified Clinical Test of Sensory Integration in Balance (mCTSIB). However, the mCTSIB is a standard group of tests relying largely on eyes-open and -closed standing positions with the head in a neutral position, associated with probability of missing postural instabilities associated with head positions off the neutral plane. Postural stability scores are compromised with changes in head positions after concussion. The position of the head and neck induced by statically maintained head turns is associated with significantly lower stability scores than the standardized head neutral position of the mCTSIB in Post-Concussion Syndrome (PCS) subjects but not in normal healthy controls. This phenomenon may serve as a diagnostic biomarker to differentiate PCS subjects from normal ones as well as serving as a measurement with which to quantify function or the success or failure of a treatment. Head positions off the neutral plane provide novel biomarkers that identify and differentiate subjects suffering from PCS from healthy normal subjects.

The Treatment of Autism Spectrum Disorder With Auditory Neurofeedback: A Randomized Placebo Controlled Trial Using the Mente Autism Device.

Introduction: Children affected by autism spectrum disorder (ASD) often have impairment of social interaction and demonstrate difficulty with emotional communication, display of posture and facial expression, with recognized relationships between postural control mechanisms and cognitive functions. Beside standard biomedical interventions and psychopharmacological treatments, there is increasing interest in the use of alternative non-invasive treatments such as neurofeedback (NFB) that could potentially modulate brain activity resulting in behavioral modification. Methods: Eighty-three ASD subjects were randomized to an Active group receiving NFB using the Mente device and a Control group using a Sham device. Both groups used the device each morning for 45 minutes over a 12 week home based trial without any other clinical interventions. Pre and Post standard ASD questionnaires, qEEG and posturography were used to measure the effectiveness of the treatment. Results: Thirty-four subjects (17 Active and 17 Control) completed the study. Statistically and substantively significant changes were found in several outcome measures for subjects that received the treatment. Similar changes were not detected in the Control group. Conclusions: Our results show that a short 12 week course of NFB using the Mente Autism device can lead to significant changes in brain activity (qEEG), sensorimotor behavior (posturography), and behavior (standardized questionnaires) in ASD children.

Posturographic changes associated with music listening.

OBJECTIVES: The aim of this study was to ascertain whether listening to music might cause changes in human stability and be useful in fall prevention and rehabilitation. The aim was also to find what percentage of subjects without neurologic signs or symptoms associated with falling had less than ideal stability. DESIGN: Computer dynamic posturography (CDP) provided stability scores in 266 subjects without a history of falls or vertigo. Subjects were randomized into several different music listening groups and one control group. The music listening groups were given a daily specific music listening task and CDP was obtained 10 minutes, 1 week, and 1 month after the subject's treatment in a blinded fashion. RESULTS: Tests of postural stability have shown that 73% of 266 subjects without neurologic signs or symptoms were found to have balance abnormalities associated with an increased probability of falling. We have demonstrated positive changes in stability scores in these subjects who underwent a variety of music listening tasks, with the music of Nolwenn Leroy found to be significantly superior to other music tested. CONCLUSIONS: Listening to certain types of music has the potential to change human stability and promote change in the field of fall prevention and rehabilitation with a potential to decrease disability.

Posturographic testing and motor learning predictability in gymnasts.

PURPOSE: One aim of this study was to find if there was a difference between balance and stability between elite level gymnasts and non-gymnasts. Another aim was to find if there was a relationship between dynamic posturographic scores associated with sway fatigue or adaptability and the ability to learn new gymnastic routines. The ultimate aim of the study was to improve gymnastic performance while reducing the probability of injury. METHODS: Computer dynamic posturography (CDP) provided stability scores, fatigability ratios and adaptation ratios in elite level gymnasts and non-gymnasts controls. Relationships between the postural integrity of gymnasts and non-gymnasts were calculated. The gymnasts were trained in a novel gymnastic routine and performance outcomes were compared to the CDP outcomes. RESULTS: Tests of postural stability have shown that gymnasts have greater postural stability than non-gymnasts. Gymnasts whose adaptability scores were higher were able to learn and perform new motor routines better than those with lower adaptability scores or high fatigability ratios. CONCLUSIONS: While gymnasts have greater postural integrity than do non-gymnasts, CDP can identify individuals whose ability to perform new motor activities might be impaired. Methodology to improve functional stability not associated with the motor task may contribute to increased sports performance and decreased probability of injury.

Head-Eye Vestibular Motion Therapy Affects the Mental and Physical Health of Severe Chronic Postconcussion Patients.

CONTEXT: Approximately 1.8-3.6 million annual traumatic brain injuries occur in the United States. An evidence-based treatment for concussions that is reliable and effective has not been available. OBJECTIVE: The objective of this study is to test whether head-eye vestibular motion (HEVM) therapy is associated with decreased symptoms and increased function in postconcussive syndrome (PCS) patients that have been severely impaired for greater than 6 months after a mild traumatic brain injury. DESIGN: Retrospective clinical chart review. SETTING AND PARTICIPANTS: Tertiary Specialist Brain Rehabilitation Center. INTERVENTIONS: All subjects underwent comprehensive neurological examinations including measurement of eye and head movement. The seven modules of the C3 Logix Comprehensive Concussion Management System were used for pre- and postmeasurements of outcome of HEVM therapy. MATERIALS AND METHODS: We utilized an objective validated measurement of physical and mental health characteristics of our patients before and after a 1-week HEVM rehabilitation program. We included only PCS patients that were disabled from work or school for a period of time exceeding 6 months after suffering a sports concussion. These subjects all were enrolled in a 5-day HEVM rehabilitation program at our Institutional Brain Center with pre- and post-C3 Logix testing outcomes. RESULTS: There were statistical and substantive significant decreases in PCS symptom severity after treatment and statistical and substantive significant increases in standardized assessment of concussion scores. The outcomes were associated with positive changes in mental and physical health issues. This is a retrospective review and no control group has been included in this study. These are major limitations with retrospective reviews and further investigations with prospective designs including a randomized controlled study are necessary to further our understanding. CONCLUSION: Head-eye vestibular motion therapy of 5 days duration is associated with statistical and substantive significant decreases of symptom severity associated with chronic PCS.

Eye-Movement Training Results in Changes in qEEG and NIH Stroke Scale in Subjects Suffering from Acute Middle Cerebral Artery Ischemic Stroke: A Randomized Control Trial.

CONTEXT: Eye-movement training (EMT) can induce altered brain activation and change the functionality of saccades with changes of the brain in general. OBJECTIVE: To determine if EMT would result in changes in quantitative electroencephalogram (qEEG) and NIH Stroke Scale (NIHSS) in patients suffering from acute middle cerebral artery (MCA) infarction. Our hypothesis is that there would be positive changes in qEEG and NIHSS after EMT in patients suffering from acute MCA ischemic stroke. DESIGN: Double-blind randomized controlled trial. SETTING AND PARTICIPANTS: Thirty-four subjects with acute MCA ischemic stroke treated at university affiliated hospital intensive care unit. INTERVENTIONS: Subjects were randomized into a "control" group treated only with aspirin (125 mg/day) and a "treatment" group treated with aspirin (125 mg/day) and a subject-specific EMT. MAIN OUTCOME MEASURES: Delta-alpha ratio, power ratio index, and the brain symmetry index calculated by qEEG and NIHSS. RESULTS: There was strong statistical and substantive significant improvement in all outcome measures for the group of stroke patients undergoing EMT. Such improvement was not observed for the "control" group, and there were no adverse effects. CONCLUSION: The addition of EMT to a MCA ischemic stroke treatment paradigm has demonstrated statistically significant changes in outcome measures and is a low cost, safe, and effective complement to standard treatment.

Between-subjects differences of within-subject variability in repeated balance measures: consequences on the minimum detectable change.

When repeating tests on a subject it is important to know if changes of the results are significant. Researchers have used measures of reliability, e.g., intraclass correlation coefficient (ICC) and minimum detectable change (MDC), to assess reliability and validity of balance measures and equipment, and to determine what constitutes a significant change (SC). Using ICC and MDC assumes measurement differences are random in nature, i.e., that within-subject variability is similar between subjects. We investigated if this assumption holds true for center of pressure based balance measures. 20 repetitions of the tests comprising the modified Clinical Test of Sensory Integration in Balance (mCTSIB) protocol were performed by two 17-subject groups simulating laboratory and clinical conditions. Force platform based computerized dynamic posturography Vestibular Technologies CAPS(®) systems exceeding ISPGR recommended accuracy, precision and resolution were used to perform the testing and collect the data. The MDC was compared with the SC computed from individual subjects' within-subject standard deviation, with and without averaging 3 repetitions. We found within-subjects variability was not similar between subjects, rendering the applicability of ICC and MDC questionable. The MDC greatly underestimated the SC for some subjects and overestimated it for others, therefore it should be used with extreme caution, if at all. It seems that for balance measures the SC is more a subject's rather than an instrument's or test's characteristic and should be evaluated on an individual basis. We suggest doing so might provide useful additional clinical information about a subject.

Effect of tone-based sound stimulation on balance performance of normal subjects: preliminary investigation.

Sound is known to affect the human brain, hence sound or music therapy is sometimes used to improve a subject's physicaland mental health. In this study, the effects sound stimulation has on balance were investigated by means of computerizeddynamic posturography tests performed with eyes closed on an unstable surface using a CAPS® system, exceeding theInternational Society for Posture and Gait Research (ISPGR) recommended metrological performance standards. Subjectswere tested without listening to any music (baseline), listening to “pure music”, and listening to the same music with differenttones embedded into it (one for each key). We found that different subjects react differently to different tones. Music alonedid not have a statistically significant effect on balance compared to the baseline, but the “best” tone significantly improvedbalance compared to the baseline or the “pure music” conditions. Furthermore, the “worst” tone reduced the balancecompared to “pure music”, but the reduction was not statistically significant relative to the baseline. The results thereforeindicate that, at least relative to balance performance, the tone-based sound stimulation we investigated is effective andinherently safe, but that tone selection depends on the individual subject.

Posturographic performance and repeatability of the computerized sit-to-stand test: preliminary results.

Each year, one in every three adults over the age of 65 falls often with injury. While this public health problem can be substantially reduced with simple interventions such as vestibular rehabilitation, balance assessments are not routinely done in the clinic, and less than half of affected adults talk to their physicians about such concerns. The goal of this study is to investigate distinct posturographic parameters of the computerized Sit-to-Stand (StS) Test to determine between- and within- subject variability of these. The CAPS® Professional system and the BalanceTRAK® software were used to collect ten repetitions of the StS from 25 subjects. The inclusion criteria included a questionnaire investigating the subject’s health status, the presence of known vestibular health concerns or illnesses, and the ability to maintain balance while standing. Significant variation between and within subjects were found for all posturographic parameters considered in this study. However, no fatigue or learning effects were found among the ten repetitions.

Evaluation of the Effectiveness of a Novel Brain and Vestibular Rehabilitation Treatment Modality in PTSD Patients Who have Suffered Combat-Related Traumatic Brain Injuries.

INTRODUCTION: Blast-related head injuries are among the most prevalent injuries suffered by military personnel deployed in combat and mild traumatic brain injury (mTBI) or concussion on the battlefield in Iraq/Afghanistan has resulted in its designation as a "signature injury." Vestibular complaints are the most frequent sequelae of mTBI, and vestibular rehabilitation (VR) has been established as the most important treatment modality for this group of patients. MATERIALS AND METHODS: We studied the effectiveness of a novel brain and VR treatment post-traumatic stress disorder (PTSD) in subjects who had suffered combat-related traumatic brain injuries in terms of PTSD symptom reduction. The trial was registered as ClinicalTrials.gov Identifier: NCT02003352. (http://clinicaltrials.gov/ct2/show/NCT02003352?term=carrick&rank=6). We analyzed the difference in the Clinician Administered DSM-IV PTSD Scale (CAPS) scores pre- and post-treatment using our subjects as their own matched controls. The study population consisted of 98 combat veterans maintaining an alpha of <0.05 and power of 80%. RESULTS: Prior to treatment, 75 subjects representing 76.53 % of the sample were classified in the 2 most severe categories of PTSD. Forty-one subjects, representing 41.80 % of the total sample, were classified in the extreme category of PTSD and 34 subjects, representing 34.70 % of the total sample, were classified in the severe category of PTSD. After treatment, we observed a large reduction in CAPS severity scores with both statistical and substantive significance. DISCUSSION: Treatment of PTSD as a physical injury rather than a psychiatric disorder is associated with strong statistical and substantive significant outcomes associated with a decrease of PTSD classification. The stigma associated with neuropsychiatric disorders may be lessened when PTSD is treated with brain and VR with a potential decrease in suffering of patients, family, and society.

Short- and Long-Term Effectiveness of a Subject's Specific Novel Brain and Vestibular Rehabilitation Treatment Modality in Combat Veterans Suffering from PTSD.

INTRODUCTION: Treatment for post-traumatic stress disorder (PTSD) in combat veterans that have a long-term positive clinical effect has the potential to modify the treatment of PTSD. This outcome may result in changed and saved lives of our service personnel and their families. In a previous before-after-intervention study, we demonstrated high statistical and substantively significant short-term changes in the Clinician Administered DSM-IV PTSD Scale (CAPS) scores after a 2-week trial of a subject's particular novel brain and vestibular rehabilitation (VR) program. The long-term maintenance of PTSD severity reduction was the subject of this study. MATERIAL AND METHODS: We studied the short- and long-term effectiveness of a subject's particular novel brain and VR treatment of PTSD in subjects who had suffered combat-related traumatic brain injuries in terms of PTSD symptom reduction. The trial was registered as ClinicalTrials.gov Identifier: NCT02003352. We analyzed the difference in the CAPS scores pre- and post-treatment (1 week and 3 months) using our subjects as their matched controls. RESULTS: The generalized least squares (GLS) technique demonstrated that with our 26 subjects in the 3 timed groups the R (2) within groups was 0.000, R (2) between groups was 0.000, and overall the R (2) was 0.000. The GLS regression was strongly statistically significant z = 21.29, p < 0.001, 95% CI [58.7, 70.63]. The linear predictive margins over time demonstrated strong statistical and substantive significance of decreasing PTSD severity scores for all timed CAPS tests. DISCUSSION: Our investigation has the promise of the development of superior outcomes of treatments in this area that will benefit a global society. The length of the treatment intervention involved (2 weeks) is less that other currently available treatments and has profound implications for cost, duration of disability, and outcomes in the treatment of PTSD in combat veterans.

In-situ verification of accuracy, precision and resolution of force and balance platforms.

It is common practice in laboratories to check for accuracy, precision and resolution of instrumentation before using it inresearch. For force platforms used in gait analysis and balance measures, most of these verifications are done in staticconditions, i.e., applying known weights in known locations on the surface of the instrument, measuring what the output is,and comparing it with what it should be. However, this is not a realistic simulation of a subject standing on the instrument,as the Center of Pressure (CoP) varies continuously over time and covers a good portion of the area of support. Otherauthors have proposed a device to assess how well a force platform measures a time-changing CoP trace by comparing themathematically known, spiral-shaped trace generated by a rotating mass with what is measured by the force platform.Changing mass and rotation speed allows evaluation of a wide range of frequencies and areas of support. In this paper, thedifferent in-situ verification techniques most commonly mentioned in the literature were investigated from a theoreticalpoint of view and then compared using commercially available balance platforms, to assess their ability to verify accuracyand resolution of force platforms.

Using posturography to measure balance control during seated tai chi.

BACKGROUND: Tai Chi for Arthritis (TCA) is recognized by the CDC as an evidenced-based program to prevent falls in older adults. Although seated Tai Chi is recommended for those unable to stand, little is known about balance control during seated TCA. PURPOSE: To explore the use of posturography to assess differences between experts and non-expert practitioners of seated TCA. METHODS: Twenty-three participants were recruited from those attending a Tai cChi workshop. While seated in a hard back chair centered on a force platform, participants performed selected forms from TCA and then did them in a continuous sequence. Center of pressure (CoP) indices to assess balance were normalized by height and then compared between expert and non-expert participants. RESULTS: Experts had significantly greater average velocity and path length (p = 0.02) for the entire sequence and open/close, but not for CoP 95% Confidence ellipse area. No significant differences in the CoP were found for commencement, wave hands, or single whip. CONCLUSIONS: A few differences in balance control while performing seated TCA movements were found. Future studies are needed to determine whether these can be accounted for by quality of the Tai Chi movements or factors associated with the seated position.

Frequency content of standard posturographic measures - biomed 2013.

Although still considered experimental by some, computerized posturography is becoming more and more the standard assessment of balance and neuromuscular control mechanisms while standing. However, there is no consensus as to the data acquisition parameters to be used. Depending on which posturography school one belongs to, acquisition frequencies vary from a few Hz all the way to 1 kHz, and little attention is usually given to the post-sampling filter cut-off frequency (implemented either in the hardware or in the software used to acquire the data), often without realizing the consequences such choices will have on the results. But the sampling and the filter cut-off frequencies are particularly important when dealing with spectral analysis or when secondary measurements such as the center of pressure coordinates, sway path length, velocity or acceleration are calculated from the measured forces and moments. In this paper, frequency content of vertical ground reaction force and center of pressure path coordinates excursion were determined for 946 subjects of both genders, with various age, height, body type, health status and nationality. The results of this spectral analysis made it possible to draw some general conclusions as to what should be a proper acquisition frequency for posturographic data.

Using posturography to assess expertise among tai chi practitioners - biomed 2013.

Tai Chi, performed either seating or standing, is frequently recommended to improve various aspects of health, including balance, metabolic control, heart rate variability, sleep, or immune response. Many studies exploring mind-body interventions, both with self-reported or biologically-measured outcomes, report significant differences in outcomes among participants. However, neither the physiological or psychological mechanisms behind the variations are understood. The purpose of this study was to determine whether posturography is a useful method to assess physical skill level differences between experts and non-expert Tai Chi practitioners. While standing, participants performed a series of movements from the Tai Chi for Arthritis form based on Sun style (commencement, open/close, single whip and wave hands in cloud). Master trainers and senior trainers were considered experts; all others were considered non-experts. Body sway was assessed by the CAPS™ Professional portable computerized force platform (Vestibular Technologies, LLC.). Center of Pressure motion measures were normalized by the subject's height. While standing, the experts displayed statistically greater displacement excursion and velocity when preforming commencement and wave hands in clouds forms. The results of this pilot study indicated that posturography may be a useful method to assess the quality of Tai Chi movements and potentially link the expertise of Tai Chi practitioners to changes in health related outcomes.

A novel methodology to evaluate the psycho-physical condition of individuals performing at-risk activities.

Currently the evaluation of the psycho-physical condition of individuals performing at-risk activities involves either subjective evaluations or invasive biological tests, and is not often indicative of the actual ability of the subject to perform the specific activity. We propose a new methodology based on posturographic and reaction time measurements, derived from the strict relationship between the control strategies used to maintain the erect posture and the psycho-physical abilities of an individual. These strategies are affected by fatigue, diseases and substances such as alcohol and drugs. The measuring device consists of a posturographic platform, a hand-held trigger and a personal computer running the software. The subject is asked to perform simultaneously two tasks: move the center of mass of the body to follow a target on the screen, and react to the appearance of another stimulus by pressing the trigger. The task is made more complicated by randomly presenting the stimuli and by the presence of “dummy” targets the subject is supposed to ignore. Evaluating how accurately the subject follows the target, the reaction times, as well as the number of reactions to “dummy” targets allows to quantify the psycho-physical condition of the individual. This methodology could be used as a real time, fast and quantitative measure to improve road and workplace safety, not invading the privacy of the subject, easily relating to real-world activities, and not requiring highly trained personnel to administer the test.

Learning effect of standing on foam during posturographic testing – preliminary findings.

Balance protocols such as the modified Clinical Test of Sensory Integration on Balance (mCTSIB) or the Balance Error Scoring System (BESS) include testing a person while standing on a thick foam cushion. The role of the foam cushion is to perturb the somatosensory and proprioceptive information and to provide an unstable and unpredictable standing surface. This, combined with asking the subject to keep the eyes closed during the test, is to make the subject rely mostly on the vestibular system to maintain balance. However, this type of condition rarely occurs in real life. It is not well understood if learning and/or fatiguing might affect the results of these type of tests. This has important methodological consequences for balance protocols in terms of the number of repetitions and how these might affect the results of the balance tests. In this study, the balance of 25 healthy subjects who had never undergone this type of testing was evaluated. The subjects performed in rapid succession 4, 60s long posturographic tests while standing on a foam cushion. A computerized posturographic device was used to collect the data. Half of the participants performed the tests with eyes open and half with eyes closed. This allowed to discover the presence of a “learning effect” the first time subjects are tested on the foam cushion. Once the subjects had learned to stand on the foam cushion, the length of the tests and the number of repetitions did not show a statistically significant effect.