Physical Activity for Anxiety for Autistic People: A Systematic Review.

Clinical anxiety is a common comorbidity in autistic people. Due to the prevalence of anxiety in the autism population and the adverse effects it causes, there is a critical need to develop effective interventions which address anxiety symptoms for autistic people. Therefore, the purpose of this systematic review was to examine the effectiveness of the use of physical activity as an intervention to reduce anxiety in autistic people. Three databases PubMed, PsychInfo, and Cochrane RCTs, were searched utilizing key terms. PRISMA systematic search procedures identified 44 studies meeting predetermined inclusion criteria. Participant characteristics, the type of physical activity performed, the nature of the physical activity program/delivery, anxiety-related outcomes, and research methodology was evaluated for each study. Each paper included was appraised and scored for risk of bias using Cochrane Handbook for Systematic Reviews of Interventions risk of bias tool. Titles and abstracts of 44 articles were reviewed and 8 articles met inclusion criteria which evaluated interventions. Evidence from 8 studies suggests that yoga, a community-based football program, an app-assisted walking program, group exercise programs, and horseback riding interventions reduced anxiety for autistic people. The studies included in this systematic review provide strong-to-moderate evidence that physical activity can reduce anxiety for autistic children and adults. However, additional research is needed to identify which mode of physical activity is most beneficial for anxiety reduction. Further, future research should evaluate frequency, duration, and intensity and their effects on anxiety for autistic people.

Evaluating Postural Transition Movement Performance in Individuals with Essential Tremor via the Instrumented Timed Up and Go.

Flexibility in performing various movements like standing, walking, and turning is crucial for navigating dynamic environments in daily life. Individuals with essential tremor often experience movement difficulties that can affect these postural transitions, limiting mobility and independence. Yet, little research has examined the performance of postural transitions in people with essential tremor. Therefore, we assessed postural transition performance using two versions of the timed up and go test: the standard version and a more complex water-carry version. We examined the total duration of the standard and water-carry timed up and go in 15 people with and 15 people without essential tremor. We also compared the time taken for each phase (sit-to-stand phase, straight-line walk phase, stand-to-sit phase) and the turning velocity between groups. Our findings revealed decreased performance across all phases of standard and water-carry timed up and go assessments. Further, both ET and non-ET groups exhibited reduced performance during the water-carry timed up and go compared to the standard timed up and go. Evaluating specific phases of the timed up and go offers valuable insights into functional movement performance in essential tremor, permitting more tailored therapeutic interventions to improve functional performance during activities of daily living.

Clinically Measuring Orofacial Somatosensation in a Cohort of Healthy Aging Adults.

PURPOSE: Humans experience the world through sensations of touch, taste, smell, vision, and audition. Alterations in sensory acuity occur across the adult life span in all types of sensation. The purpose of this study was to describe possible differences in lip and tongue somatosensation (sense of pressure) for healthy older adults using clinically available measurement tools as compared with previously published data using the same protocol. METHOD: A total of 33 healthy adults (ages 60-93 years; M = 70.5 years; 19 women) completed bilateral assessment of lip and tongue pressure detection and discrimination using two-point discrimination discs and Von Frey hair monofilaments. Participants reported basic health information and completed a pure-tone hearing threshold assessment within the same session. RESULTS: Descriptive results are presented for individual data points from healthy aging adults. Group data are compared with previously published data from a cohort of healthy young participants. Although there were no statistically significant differences between the two healthy groups, variations in standard deviations in older adults were observed. CONCLUSIONS: Two-point discrimination and tactile detection and discrimination using Von Frey hair monofilaments can be used to assess labial and lingual pressure detection and discrimination in healthy aging adults. While not reaching statistical significance, on average, older adults demonstrated increased threshold estimates compared with younger adults with increases in standard deviations up to 11.5 times larger than the younger cohort. Subtle differences in somatosensation across the ages may be important for future comparisons with clinical populations across the life span. These assessment techniques can be used with an aging population to complete objective orofacial somatosensory testing.

Cognitive Demands Influence Drop Jump Performance and Relationships With Leg Stiffness in Healthy Young Adults.

ABSTRACT: Holmes, HH, Downs Talmage, JL, Neely, KA, and Roper, JA. Cognitive demands influence drop jump performance and relationships with leg stiffness in healthy young adults. J Strength Cond Res 37(1): 74-83, 2023-Sports-relevant cognition influences neuromuscular control and sports performance. This study assessed the influence of cognition on (a) drop jump performance and (b) commonly researched relationships between lower extremity stiffness, ground contact time (GCT), peak vertical ground reaction force (vGRF), and leg deformation. Active adults (n = 33, 13 men, 20 women, 21 ± 2 years, height = 1.71 ± 0.81 m, body mass = 70.5 ± 10.6 kg) participated in decisions to perform drop jumps or lands of a 30-cm box in 4 conditions: (a) standard, explicit instructions; (b) choice, internally driven decisions; and (c and d) visual and audio, external visual or audio cues reducing time for motor planning. Significance was set at p < 0.05. Ground contact time with audio (M ± SD: 0.62 ± 0.14 seconds) and visual cues (0.59 ± 0.10 seconds) was longer than standard instructions (0.54 ± 0.10 seconds). Standard condition jump height was higher (0.49 ± 0.10 m) than audio (0.435 ± 0.10 m) and choice (0.44 ± 0.09 m). Standard condition reactive strength index was higher (1.03 ± 0.35) than audio (0.76 ± 0.23), visual (0.82 ± 0.27), and choice (0.84 ± 0.33). Visual and audio conditions did not demonstrate significant relationships between leg stiffness and GCT, and relationships between vGRF and leg deformation were not significant with visual cues (p > 0.05). Cognition did not significantly change stiffness and vGRF, indicating alternative force strategies. Understanding how cognition influences performance can positively affect coaching practices, sports-specific assessments, and rehabilitation applications.

Sleep restriction impairs visually and memory-guided force control.

Sleep loss is a common phenomenon with consequences to physical and mental health. While the effects of sleep restriction on working memory are well documented, it is unknown how sleep restriction affects continuous force control. The purpose of this study was to determine the effects of sleep restriction on visually and memory-guided force production magnitude and variability. We hypothesized that both visually and memory-guided force production would be impaired after sleep restriction. Fourteen men participated in an eleven-day inpatient sleep study and completed a grip force task after two nights of ten hours' time in bed (baseline); four nights of five hours' time in bed (sleep restriction); and one night of ten hours' time in bed (recovery). The force task entailed four 20-second trials of isometric force production with the thumb and index finger targeting 25% of the participant's maximum voluntary contraction. During visually guided trials, participants had continuous visual feedback of their force production. During memory-guided trials, visual feedback was removed for the last 12 seconds of each trial. During both conditions, participants were told to maintain the target force production. After sleep restriction, participants decreased the magnitude of visually guided, but not memory-guided, force production, suggesting that visual attention tasks are more affected by sleep loss than memory-guided tasks. Participants who reported feeling more alert after sleep restriction and recovery sleep produced higher force during memory-guided, but not visually guided, force production, suggesting that the perception of decreased alertness may lead to more attention to the task during memory-guided visual tasks.

Inorganic nitrate supplementation and blood flow restricted exercise tolerance in post-menopausal women.

Exercise tolerance appears to benefit most from dietary nitrate (NO3-) supplementation when muscle oxygen (O2) availability is low. Using a double-blind, randomized cross-over design, we tested the hypothesis that acute NO3- supplementation would improve blood flow restricted exercise duration in post-menopausal women, a population with reduced endogenous nitric oxide bioavailability. Thirteen women (57-76 yr) performed rhythmic isometric handgrip contractions (10% MVC, 30 per min) during progressive forearm blood flow restriction (upper arm cuff gradually inflated 20 mmHg each min) on three study visits, with 7-10 days between visits. Approximately one week following the first (familiarization) visit, participants consumed 140 ml of NO3- concentrated (9.7 mmol, 0.6 gm NO3-) or NO3-depleted beetroot juice (placebo) on separate days (≥7 days apart), with handgrip exercise beginning 100 min post-consumption. Handgrip force recordings were analyzed to determine if NO3- supplementation enhanced force development as blood flow restriction progressed. Nitrate supplementation increased plasma NO3- (16.2-fold) and NO2- (4.2-fold) and time to volitional fatigue (61.8 ± 56.5 s longer duration vs. placebo visit; p = 0.03). Nitrate supplementation increased the rate of force development as forearm muscle ischemia progressed (p = 0.023 between 50 and 75% of time to fatigue) with non-significant effects thereafter (p = 0.052). No effects of nitrate supplementation were observed for mean duration of contraction or relaxation rates (all p > 0.150). These results suggest that acute NO3- supplementation prolongs time-to-fatigue and speeds grip force development during progressive forearm muscle ischemia in postmenopausal women.

Manual dexterity and strength and in young adults with and without Attention-Deficit/Hyperactivity Disorder (ADHD).

Manual motor deficits are common in children with attention deficit/hyperactivity disorder (ADHD); however, it is unclear whether these impairments persist into adulthood. The aim of this study was to examine manual dexterity and strength in young adults with ADHD aged 18-25 years. Sixty-one individuals with confirmed ADHD and 56 adults without ADHD completed Purdue Pegboard tasks for manual dexterity and maximal hand- and pinch-grip tests for strength. In the Purdue Pegboard task, participants placed pins using the right, left, and both-hands, respectively. In addition, participants built assemblies using pins, washers, and collars with alternating hand movements. The results demonstrated that women without ADHD out-performed the other three groups in the right-hand, bimanual, and assembly PPB tasks. Both maximal hand strength tests demonstrated that men were stronger than women, but no differences were observed between adults with and without ADHD. The current findings suggest that adults with ADHD may have deficits in manual dexterity and tasks requiring bimanual coordination.

Speech motor control and orofacial point pressure sensation in adults with ADHD.

Attention-Deficit Hyperactivity Disorder (ADHD) is a predominant neurobehavioral disorder of childhood with motor and sensory symptoms often persisting into adulthood. Motor control theories highlight the importance of the bidirectional relationship between sensation and movement for maintaining skilled behaviors like speech. The impact of ADHD on speech in adults has not been well established. The purpose of this study is to assess group differences in quantitative speech and oral somatosensory measures in adults with and without ADHD and to describe the relationship between ADHD symptomology and speech production. A total of 50 adults (18-26 years) were recruited and divided in two groups based on diagnosis: those with (n = 28) and those without (n = 22) ADHD. All participants provided a speech sample to measure articulatory accuracy and speech rate and completed quantitative point-pressure testing using tactile detection and discrimination on bilateral sites on the lower lip and lateral edge of the tongue tip. Independent t-tests corrected for multiple comparisons identified significant group differences using FDR corrected q values in speech production for correct syllables per second and overall speech rate (q<.05). Additionally, there were significant group differences (q<.05) for detection and discrimination threshold estimates at one testing location. Bivariate correlations identified a relationship between several speech measures and self-reported ADHD symptoms such that as symptom severity increased, speech accuracy for correct syllables per second decreased. Young adults with ADHD have subtle differences in speech production compared to non-ADHD control participants. Speech scientists might consider screening for ADHD when collecting normative data samples.

Sex and Emotion Regulation Difficulties Contribute to Depression in Young Adults With Attention-Deficit/Hyperactivity Disorder.

Many young adults with attention-deficit/hyperactivity disorder (ADHD) are at risk for depression. Yet, questions remain about factors associated with the development of depression in young adults with ADHD. This study examined the effects of sex and emotion regulation difficulties on depression in a sample of young adults with (n = 172) and without (n = 730) ADHD. Two aspects of emotion regulation difficulties were examined-impairments in emotional insight (i.e., lack of emotional awareness, nonacceptance of emotion, and lack of emotional clarity) and impairments in behavioral response to emotion (i.e., impulse control difficulties, difficulties engaging in goal-directed behavior, and limited access to emotion regulation strategies). Significant correlations between ADHD and all indices of emotion regulation difficulty emerged. Sex moderated the association between ADHD and lack of emotional awareness, difficulties engaging in goal-directed behavior, and limited access to emotion regulation strategies. Specifically, ADHD was significantly associated with limited emotion regulation awareness for women but not men, while ADHD was associated with greater difficulties engaging in goal-directed behavior and limited access to emotion regulation strategies for women compared to men. These three areas of emotion regulation dysfunction simultaneously mediated the association between ADHD and depression. The findings indicate the importance of considering emotion regulation and sex in understanding depression in young adults with ADHD.

Depression and Suicidal Behavior in Young Adult Men and Women With ADHD: Evidence From Claims Data.

OBJECTIVE: This study used commercial claims data to examine the effects of ADHD and sex on the prevalence of depression, suicidal ideation, and suicide attempts in a sample of young adult men and women (aged 18-25 years) with and without attention-deficit/hyperactivity disorder (ADHD). Patterns of treatment use for these conditions was also explored. METHODS: Young adults with ADHD (162,263 women and 225,705 men) having at least 2 claims with the International Classification of Diseases, Ninth Revision (ICD-9), code for ADHD and a sex- and age-matched group of young adults without an ICD-9 code for ADHD (162,263 women and 225,705 men) were identified. The prevalence of ICD-9 depression and suicidal behavior along with the use and cost of related treatment were compared between young adults with and without ADHD using 2014 claims data. RESULTS: Compared to young adults without ADHD, young adults with ADHD were more frequently identified with depression, suicidal ideation, and suicide attempts. Depression and suicidal ideation were identified more frequently among women with ADHD compared to all other groups. Young adults with ADHD were more frequently engaged in outpatient and inpatient mental health care compared to young adults without ADHD (P < .0001 in each instance). Furthermore, overall costs of outpatient and inpatient care were greater among young adults with ADHD compared to young adults without ADHD (P < .0001 in each instance). CONCLUSIONS: These findings highlight the substantial burden of depression and suicidal behavior among young adults with ADHD, particularly women, and underlie the need for more research focused on mitigating risk for depression and suicidal behavior among both men and women with ADHD.

Lexical frequency affects functional activation and accuracy in picture naming among older and younger adults.

As individuals age, they experience increased difficulties producing speech, especially with infrequent words. Older adults report that word retrieval difficulties frequently occur and are highly frustrating. However, little is known about how age affects the neural basis of language production. Moreover, age-related increases in brain activation are often observed, yet there is disagreement about whether such increases represent a form of neural compensation or dedifferentiation. We used functional magnetic resonance imaging (fMRI) to determine if there are age-related differences in functional activation during picture naming and whether such differences are consistent with a compensatory, dedifferentiation, or hybrid account that factors in difficulty. Healthy younger and older adults performed a picture-naming task with stimuli that varied in lexical frequency-our proxy for difficulty. Both younger and older adults were sensitive to lexical frequency behaviorally and neurally. However, younger adults performed more accurately overall and engaged both language (bilateral insula and temporal pole) and cognitive control (bilateral superior frontal gyri and left cingulate) regions to a greater extent than older adults when processing lower frequency items. In both groups, poorer performance was associated with increases in functional activation consistent with dedifferentiation. Moreover, there were age-related differences in the strength of these correlations, with better performing younger adults modulating the bilateral insula and temporal pole and better performing older adults modulating bilateral frontal pole and precuneus. Overall, these findings highlight the influence of task difficulty on fMRI activation in older adults and suggest that as task difficulty increases, older and younger adults rely on different neural resources. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Shared neural recruitment across working memory and motor control tasks as a function of task difficulty and age.

Past research suggests that working memory (WM) and motor control may engage similar cognitive and neural mechanisms in older adults, particularly when task difficulty increases. However, much of this evidence arises from comparisons across behavioral and imaging studies that test only one of the foregoing functional domains. The current study used fMRI within the same group of older adults to investigate whether WM and motor control recruit common mechanisms, and whether recruitment increased with task demand and age. A conjunction analysis across WM and motor tasks revealed engagement of several frontoparietal regions as a function of increasing task demand. A separate conjunction analysis which included age as a predictor showed comparable regions exhibit increased recruitment with both increasing task demand and age. Results suggest that the recruitment of common frontoparietal regions across WM and motor tasks in response to task difficulty is maintained across the older adult lifespan.

Motor Memory Deficits Contribute to Motor Impairments in Autism Spectrum Disorder.

Sensorimotor abnormalities are common in individuals with autism spectrum disorder (ASD); however, the processes underlying these deficits remain unclear. This study examined force production with and without visual feedback to determine if individuals with ASD can utilize internal representations to guide sustained force. Individuals with ASD showed a faster rate of force decay in the absence of visual feedback. Comparison of force output and tests of social and verbal abilities demonstrated a link between motor memory impairment and social and verbal deficits in individuals with ASD. This finding suggests that deficits in storage or retrieval of motor memories contribute to sensorimotor deficits and implicates frontoparietal networks involved in short-term consolidation of action dynamics used to optimize ongoing motor output.

Attention-deficit/hyperactivity disorder and callous-unemotional traits as moderators of conduct problems when examining impairment in emerging adults.

This study examines attention-deficit/hyperactivity disorder (ADHD) and callous-unemotional (CU) traits as moderators of the association between conduct problems (CP) and young adult functioning. Young adults (n = 283; Mage = 20.82 years; 53.4% female), oversampled for attention and behavior problems, provided self-ratings of ADHD, CP, and CU, and adaptive functioning and psychopathology. ADHD and CU simultaneously moderated relationships between CP and family functioning, tobacco use, and internalizing symptoms. In addition, ADHD moderated the relation between CP and job functioning, and main effects of ADHD in the expected direction were found for educational performance and drug use. CU was associated with poorer educational outcomes. Interestingly, no ADHD, CU, or CP effects were observed for reported alcohol use. Our results highlight the importance of considering ADHD and CU in understanding the impact of CP on young adult functioning and psychopathology, and point to the importance of continued work on this topic.

Memory-guided force control in healthy younger and older adults.

Successful performance of a memory-guided motor task requires participants to store and then recall an accurate representation of the motor goal. Further, participants must monitor motor output to make adjustments in the absence of visual feedback. The goal of this study was to examine memory-guided grip force in healthy younger and older adults and compare it to performance on behavioral tasks of working memory. Previous work demonstrates that healthy adults decrease force output as a function of time when visual feedback is not available. We hypothesized that older adults would decrease force output at a faster rate than younger adults, due to age-related deficits in working memory. Two groups of participants, younger adults (YA: N = 32, mean age 21.5 years) and older adults (OA: N = 33, mean age 69.3 years), completed four 20-s trials of isometric force with their index finger and thumb, equal to 25% of their maximum voluntary contraction. In the full-vision condition, visual feedback was available for the duration of the trial. In the no vision condition, visual feedback was removed for the last 12 s of each trial. Participants were asked to maintain constant force output in the absence of visual feedback. Participants also completed tasks of word recall and recognition and visuospatial working memory. Counter to our predictions, when visual feedback was removed, younger adults decreased force at a faster rate compared to older adults and the rate of decay was not associated with behavioral performance on tests of working memory.

Deficits in inhibitory force control in young adults with ADHD.

Poor inhibitory control is a well-established cognitive correlate of adults with ADHD. However, the simple reaction time (RT) task used in a majority of studies records performance errors only via the presence or absence of a single key press. This all-or-nothing response makes it impossible to capture subtle differences in underlying processes that shape performance. Subsequently, all-or-nothing tasks may underestimate the prevalence of executive function deficits in ADHD. The current study measured inhibitory control using a standard Go/No-Go RT task and a more sensitive continuous grip force task among adults with (N=51, 22 female) and without (N=51, 29 female) ADHD. Compared to adults without ADHD, adults with ADHD made more failed inhibits in the classic Go/No-Go paradigm and produced greater and more variable force during motor inhibition. The amount of force produced on failed inhibits was a stronger predictor of ADHD-related symptoms than the number of commissions in the standard RT task. Adults with ADHD did not differ from those without ADHD on the mean force and variability of force produced in Go trials. These findings suggest that the use of a precise and continuous motor task, such as the force task used here, provides additional information about the nature of inhibitory motor control in adults with ADHD.

Memory-guided force output is associated with self-reported ADHD symptoms in young adults.

Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed mental health disorder in childhood and persists into adulthood in up to 65 % of cases. ADHD is associated with adverse outcomes such as the ability to gain and maintain employment and is associated with an increased risk for substance abuse obesity workplace injuries and traffic accidents A majority of diagnosed children have motor deficits; however, few studies have examined motor deficits in young adults. This study provides a novel examination of visuomotor control of grip force in young adults with and without ADHD. Participants were instructed to maintain force production over a 20-second trial with and without real-time visual feedback about their performance. The results demonstrated that when visual feedback was available, adults with ADHD produced slightly higher grip force than controls. However, when visual feedback was removed, adults with ADHD had a faster rate of decay of force, which was associated with ADHD symptom severity and trait impulsivity. These findings suggest that there may be important differences in the way that adults with ADHD integrate visual feedback during continuous motor tasks. These may account for some of the motor impairments reported in children with ADHD. These deficits could result from (1) dysfunctional sensory motor integration and/or (2) deficits in short-term visuomotor memory.

Non-target stimuli in the visual field influence movement preparation in upper-limb reaching.

The present work provides an empirical test of the Dynamic Field Theory of visuospatial cognition. The Dynamic Field Theory is a bi-stable neural network model applied to explain how visual information is integrated during the preparation of reaching responses (Erlhagen and Schöner). The dynamic field theory posits that motor cortices develop peaks of activation for each possible target in the visual field. Targets that are close in space produce neural peaks with overlapping distributions, whereas targets that are far apart produce distinct peaks with non-overlapping distributions. As such, the Dynamic Field Theory predicts reaction times to potential targets that are close in space will be faster than those to targets that are far apart. The present work examined how proximal and distal distractors impact reaction time in an upper-limb reaching task. The results demonstrated that distal distractors result in prolonged reaction times compared to proximal distractors. We suggest that reaction time represents the time required to inhibit neural activity representing the location of the distractor. Thus, prolonged reaction times observed for distal distractors reflect the temporal demands associated with the competition of two non-overlapping distributions of activity in the brain. These findings support the tenets of the Dynamic Field Theory and demonstrate that non-target stimuli in the visual field can influence movement preparation.

Functional Brain Activity Relates to 0-3 and 3-8 Hz Force Oscillations in Essential Tremor.

It is well-established that during goal-directed motor tasks, patients with essential tremor have increased oscillations in the 0-3 and 3-8 Hz bands. It remains unclear if these increased oscillations relate to activity in specific brain regions. This study used task-based functional magnetic resonance imaging to compare the brain activity associated with oscillations in grip force output between patients with essential tremor, patients with Parkinson's disease who had clinically evident tremor, and healthy controls. The findings demonstrate that patients with essential tremor have increased brain activity in the motor cortex and supplementary motor area compared with controls, and this activity correlated positively with 3-8 Hz force oscillations. Brain activity in cerebellar lobules I-V was reduced in essential tremor compared with controls and correlated negatively with 0-3 Hz force oscillations. Widespread differences in brain activity were observed between essential tremor and Parkinson's disease. Using functional connectivity analyses during the task evidenced reduced cerebellar-cortical functional connectivity in patients with essential tremor compared with controls and Parkinson's disease. This study provides new evidence that in essential tremor 3-8 Hz force oscillations relate to hyperactivity in motor cortex, 0-3 Hz force oscillations relate to the hypoactivity in the cerebellum, and cerebellar-cortical functional connectivity is impaired.

Force control deficits in individuals with Parkinson's disease, multiple systems atrophy, and progressive supranuclear palsy.

OBJECTIVE: This study examined grip force and cognition in Parkinson's disease (PD), Parkinsonian variant of multiple system atrophy (MSAp), progressive supranuclear palsy (PSP), and healthy controls. PD is characterized by a slower rate of force increase and decrease and the production of abnormally large grip forces. Early-stage PD has difficulty with the rapid contraction and relaxation of hand muscles required for precision gripping. The first goal was to determine which features of grip force are abnormal in MSAp and PSP. The second goal was to determine whether a single variable or a combination of motor and cognitive measures would distinguish patient groups. Since PSP is more cognitively impaired relative to PD and MSAp, we expected that combining motor and cognitive measures would further distinguish PSP from PD and MSAp. METHODS: We studied 44 participants: 12 PD, 12 MSAp, 8 PSP, and 12 controls. Patients were diagnosed by a movement disorders neurologist and were tested off anti-Parkinsonian medication. Participants completed a visually guided grip force task wherein force pulses were produced for 2 s, followed by 1 s of rest. We also conducted four cognitive tests. RESULTS: PD, MSAp, and PSP were slower at contracting and relaxing force and produced longer pulse durations compared to controls. PSP produced additional force pulses during the task and were more cognitively impaired relative to other groups. A receiver operator characteristic analysis revealed that the combination of number of pulses and Brief Test of Attention (BTA) discriminated PSP from PD, MSAp, and controls with a high degree of sensitivity and specificity. CONCLUSIONS: Slowness in contracting and relaxing force represent general features of PD, MSAp, and PSP, whereas producing additional force pulses was specific to PSP. Combining motor and cognitive measures provides a robust method for characterizing behavioral features of PSP compared to MSAp and PD.