Pinch Grip Task Research Articles

The effect of trapeziometacarpal joint passive stiffness on mechanical loadings of cartilages

Hypermobility of the trapeziometacarpal joint is commonly considered to be a potential risk factor for osteoarthritis. Nevertheless, the results remain controversial due to a lack of quantitative validation. The objective of this study was to evaluate the effect of joint laxity on the mechanical loadings of cartilage.A patient-specific finite element model of trapeziometacarpal joint passive stiffness was developed. The joint passive stiffness was modeled by creating linear springs all around the joint. The linear spring stiffness was determined by using an optimization process to fit force–displacement data measured during laxity tests performed on eight healthy volunteers. The estimated passive stiffness parameters were then included in a full thumb finite element simulation of a pinch grip task driven by muscle forces to evaluate the effect on trapeziometacarpal loading. The correlation between stiffness and the loading of cartilage in terms of joint contact pressure and maximum shear strain was analyzed.A significant negative correlation was found between the trapeziometacarpal joint passive stiffness and the contact pressure on trapezium cartilage during the simulated pinch grip task.These results therefore suggest that the hypermobility of the trapeziometacarpal joint could affect the contact pressure on trapezium cartilage and support the existence of an increased risk associated with hypermobility.

Exercise repetition rate measured with simple sensors at home can be used to estimate Upper Extremity Fugl-Meyer score after stroke.

It would be valuable if home-based rehabilitation training technologies could automatically assess arm impairment after stroke. Here, we tested whether a simple measure-the repetition rate (or "rep rate") when performing specific exercises as measured with simple sensors-can be used to estimate Upper Extremity Fugl-Meyer (UEFM) score. 41 individuals with arm impairment after stroke performed 12 sensor-guided exercises under therapist supervision using a commercial sensor system comprised of two pucks that use force and motion sensing to measure the start and end of each exercise repetition. 14 of these participants then used the system at home for three weeks. Using linear regression, UEFM score was well estimated using the rep rate of one forward-reaching exercise from the set of 12 exercises (r2 = 0.75); this exercise required participants to alternately tap pucks spaced about 20 cm apart (one proximal, one distal) on a table in front of them. UEFM score was even better predicted using an exponential model and forward-reaching rep rate (Leave One Out Cross Validation (LOOCV) r2 = 0.83). We also tested the ability of a nonlinear, multivariate model (a regression tree) to predict UEFM, but such a model did not improve prediction (LOOCV r2 = 0.72). However, the optimal decision tree also used the forward-reaching task along with a pinch grip task to subdivide more and less impaired patients in a way consistent with clinical intuition. At home, rep rate for the forward-reaching exercise well predicted UEFM score using an exponential model (LOOCV r2 = 0.69), but only after we re-estimated coefficients using the home data. These results show how a simple measure-exercise rep rate measured with simple sensors-can be used to infer an arm impairment score and suggest that prediction models should be tuned separately for the clinic and home environments.

Rate control deficits during pinch grip and ankle dorsiflexion in early-stage Parkinson's disease.

Much of our understanding of the deficits in force control in Parkinson's disease (PD) relies on findings in the upper extremity. Currently, there is a paucity of data pertaining to the effect of PD on lower limb force control. The purpose of this study was to concurrently evaluate upper- and lower-limb force control in early-stage PD and a group of age- and gender-matched healthy controls. Twenty individuals with PD and twenty-one healthy older adults participated in this study. Participants performed two visually guided, submaximal (15% of maximum voluntary contractions) isometric force tasks: a pinch grip task and an ankle dorsiflexion task. PD were tested on their more affected side and after overnight withdrawal from antiparkinsonian medication. The tested side in controls was randomized. Differences in force control capacity were assessed by manipulating speed-based and variability-based task parameters. Compared with controls, PD demonstrated slower rates of force development and force relaxation during the foot task, and a slower rate of relaxation during the hand task. Force variability was similar across groups but greater in the foot than in the hand in both PD and controls. Lower limb rate control deficits were greater in PD with more severe symptoms based on the Hoehn and Yahr stage. Together, these results provide quantitative evidence of an impaired capacity in PD to produce submaximal and rapid force across multiple effectors. Moreover, results suggest that force control deficits in the lower limb may become more severe with disease progression.

Influence of emotion on precision grip force control: A comparison of pleasant and neutral emotion.

The present study aimed to investigate the impact of emotion on force steadiness of isometric precision pinch grip that is not direction-specific. Thirty-two healthy volunteer subjects participated in the present study. Subjects were divided into two experimental groups: pleasant image group and neutral image group. The isometric precision pinch grip task was performed for three times. Specifically, the first task was performed before pleasant or neutral picture viewing, the second task was performed immediately after picture viewing, further the third task was performed 30 seconds after the second task. During the isometric precision pinch grip task, participants were asked to exert pinch grip force at 10% of maximal voluntary contraction with visual feedback. The coefficient of variation of force production and normalized root mean square value of electromyography activity were calculated. After pleasant picture viewing, coefficient of variation of pinch force production and normalized root mean square value of electromyography was decreased. While, in the neutral image condition, theses variables were not altered. More important, compared to the neutral image condition, pleasant emotion led to lower coefficient of variation of pinch grip force production. These findings indicate that pleasant emotion improves force control of isometric precision pinch grip. Therefore, in clinical settings, the emotional state of patients may affect the effectiveness of rehabilitation and should be taken into consideration.

Emotions and ensuing motor performance are altered by regulating breathing frequency: Implications for emotion regulation and sport performance.

Breathing interventions have been shown to improve sport performance. Although evidence exists to support the role of perceived arousal as a critical underlying mechanism of breathing interventions, methodological differences in the literature preclude clear understanding of potential contributing factors to the effectiveness of such interventions. Under neutral contexts, we have demonstrated attention, dyspnea, and hindrance may need to be considered as mediators of how breathing frequency affects motor performance. We sought to extend our previous findings to determine how breathing frequency affects motor performance under varying emotional conditions. Participants (N = 35, Mage = 21.68, SD = 2.96; 20 females) performed slow, normal, and fast metronome-paced breathing while viewing pleasant and unpleasant stimuli prior to executing a pinch grip task. Performance was assessed via reaction time (RT), variability (V) and error (AE). Assessment of indices of perceived arousal included measuring heart rate variability (HRV) and visual analog scale responses. Visual analog scales were also used to assess attention, dyspnea, and hindrance. Repeated measures ANOVAs showed slow breathing increased RT and HRV compared to normal and fast breathing under emotional conditions (all p’s < 0.05). Hierarchical multiple regression models revealed that decreased breathing frequency predicted increases in RT (β = −0.25, p < 0.05) under pleasant conditions, while predicting increases in HRV for unpleasant conditions (β = −0.45, p < 0.001). Increases in dyspnea (β = 0.29, p < 0.05) and hindrance (β = 0.35, p < 0.01) predicted increases in RT under pleasant conditions, while only increases in hindrance predicted increases in RT under unpleasant conditions (β = 0.41, p < 0.01). Decreases in breathing frequency predicted increases in HRV under unpleasant conditions (β = −0.45, p < 0.001). Overall, our findings suggest under varying emotional contexts breathing frequency differentially affects movement, potentially mediated by factors other than perceived arousal. In addition, these results inform the use of breath regulation as an antecedent emotion regulation strategy.

The effect of index finger distal interphalangeal joint arthrodesis on muscle forces and adjacent joint contact pressures.

Distal interphalangeal joint arthrodesis is a frequent surgical operation performed to treat severe arthritis. Nevertheless, the angle selected when fusing the joint is arbitrarily chosen without any quantified data concerning its mechanical effects, thus preventing the optimal choice for the patient. In the current study, we realized an experiment and developed a numerical model to investigate the effect of fusion angle on the biomechanics of adjacent non-operated joints. Six participants performed a pinch grip task while arthrodesis was simulated with a metal splint. Kinematic and force data were recorded during this task and used in a biomechanical model to estimate contact pressures in adjacent joints. The biomechanical model involved combining a multibody system and a finite element method. Results showed that the angle of any distal interphalangeal joint arthrodesis influences index finger kinematics and maximal grip force in several participants. For one participant, in the arthrodesis simulation, we observed an increase of 1.9MPa in the proximal interphalangeal joint contact pressure. Our results provide quantified information about the biomechanical consequences of this surgical operation and its potential long-term effects.

Modulation of subjective peripheral sensation, F-waves, and somatosensory evoked potentials in response to unilateral pinch task measured on the contractile and non-contractile sides.

Depression of the sensory input during voluntary muscle contractions has been demonstrated using electrophysiological methods in both animals and humans. However, the association between electrophysiological responses of the sensory system and subjective peripheral sensation (SPS) during a voluntary muscle contraction remains unclear. This study aimed to describe the changes in SPS, spinal α-motoneuron excitability (F-wave to M-wave amplitude), and somatosensory evoked potentials (SEPs) during a unilateral pinch-grip task. Outcome variables were measured on the side ipsilateral and contralateral to the muscle contraction and at rest (control). Participants were 8 healthy men aged 20.9±0.8 years. The isometric pinch-grip task was performed at 30% of the maximum voluntary isometric force measured for the right and left hands separately. The appearance rate of the F-wave during the task was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and control condition. Although there was no difference in the F-wave latency between hands and the control condition, the amplitude of the F-wave was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. There was no difference in the amplitude of the SEP at N20. However, the amplitude at P25 was significantly lower for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. The accuracy rate of detecting tactile stimulation, evaluated for 20 repetitions using a Semmes–Weinstein monofilament at the sensory threshold for each participant, was significantly lower during the pinch-grip task for both the ipsilateral (right) and contralateral (left) hands than in the control condition. Overall, our findings show that SPS and neurophysiological parameters were not modulated in parallel during the task, with changes in the subjective sensation preceding changes in electrophysiological indices during the motor task. Our findings provide basic information on sensory-motor coordination.

Long-Term Application of Cerebellar Transcranial Direct Current Stimulation Does Not Improve Motor Learning in Parkinson's Disease.

Cerebellar transcranial direct current stimulation (c-tDCS) enhances motor skill acquisition and motor learning in young and old adults. Since the cerebellum is involved in the pathophysiology of Parkinson’s disease (PD), c-tDCS may represent an intervention with potential to improve motor learning in PD. The primary purpose was to determine the influence of long-term application of c-tDCS on motor learning in PD. The secondary purpose was to examine the influence of long-term application of c-tDCS on transfer of motor learning in PD. The study was a randomized, double-blind, SHAM-controlled, between-subjects design. Twenty-one participants with PD were allocated to either a tDCS group or a SHAM stimulation group. Participants completed 9 practice sessions over a 2-week period that involved extensive practice of an isometric pinch grip task (PGT) and a rapid arm movement task (AMT). These practice tasks were performed over a 25-min period concurrent with either anodal c-tDCS or SHAM stimulation. A set of transfer tasks that included clinical rating scales, manual dexterity tests, and lower extremity assessments were quantified in Test sessions at Baseline, 1, 14, and 28 days after the end of practice (EOP). There were no significant differences between the c-tDCS and SHAM groups as indicated by performance changes in the practice and transfer tasks from Baseline to the 3 EOP Tests. The findings indicate that long-term application of c-tDCS does not improve motor learning or transfer of motor learning to a greater extent than practice alone in PD.

Fast breathing facilitates reaction time and movement time of a memory-guided force pulse

Slow controlled breathing can be beneficial for performance of continuous and serial motor tasks. However, how controlled breathing influences discrete motor task performance remains unclear. We sought to determine the impact of paced breathing frequency on measures of movement initiation (reaction time: RT), accuracy (absolute endpoint error: AE; constant error: CE), and variability (trial-to-trial variability: V), in a goal-directed discrete motor task. We hypothesized slow breathing would be accompanied by faster RT, reduced AE and CE, and less V compared to faster breathing rates. Participants (N=47) performed a memory-guided force pulse pinch task targeted at 10% of their maximum voluntary contraction while breathing at metronome-paced slow, normal, and fast frequencies. During each breathing condition, heart rate variability (HRV) as indexed by the standard deviation of 'NN' intervals (SDNN) was measured to ensure objective manipulation check of participants breathing at their set pace. Following each breathing condition, participants provided subjective ratings using the Affect Grid and Visual Analog Scales for arousal, hindrance, and dyspnea. Manipulation check results indicated participants correctly breathed at metronome paces, as indexed by increased HRV for slow breathing and decreased HRV for fast breathing. Results indicated that fast breathing reduced reaction time and movement time, and increased ratings of arousal, hindrance, and dyspnea. In contrast, slow breathing increased reaction time, and levels of hindrance and dyspnea were similar to normal breathing. Breathing frequency did not differentially impact accuracy or variability across conditions. Findings provide evidence that breathing frequency affects fundamental movement parameters, potentially mediated by factors other than arousal.

Estimation of joint contact pressure in the index finger using a hybrid finite element musculoskeletal approach

The knowledge of local stress distribution in hand joints is crucial to understand injuries and osteoarthritis occurrence. However, determining cartilage contact stresses remains a challenge, requiring numerical models including both accurate anatomical components and realistic tendon force actuation. Contact forces in finger joints have frequently been calculated but little data is available on joint contact pressures. This study aimed to develop and assess a hybrid biomechanical model of the index finger to estimate in-vivo joint contact pressure during a static maximal strength pinch grip task. A finite element model including bones, cartilage, tendons, and ligaments was developed, with tendon force transmission based on a tendon-pulley system. This model was driven by realistic tendon forces estimated from a musculoskeletal model and motion capture data for six subjects. The hybrid model outputs agreed well with the experimental measurement of fingertip forces and literature data on the physiological distribution of tendon forces through the index finger. Mean contact pressures were 6.9 ± 2.7 MPa, 6.2 ± 1.0 MPa and 7.2 ± 1.3 MPa for distal, proximal interphalangeal and metacarpophalangeal joints, respectively. Two subjects had higher mean contact pressure in the distal joint than in the other two joints, suggesting a mechanical cause for the prevalence of osteoarthritis in the index distal joint. The inter-subject variability in joint contact pressure could be explained by different neuromuscular strategies employed for the task. This first application of an effective hybrid model to the index finger is promising for estimating hand joint stresses under daily grip tasks and simulating surgical procedures.

Altered visual strategies and attention are related to increased force fluctuations during a pinch grip task in older adults.

The purpose of the study was to determine the visual strategies used by older adults during a pinch grip task and to assess the relations between visual strategy, deficits in attention, and increased force fluctuations in older adults. Eye movements of 23 older adults (>65 yr) were monitored during a low-force pinch grip task while subjects viewed three common visual feedback displays. Performance on the Grooved Pegboard test and an attention task (which required no concurrent hand movements) was also measured. Visual strategies varied across subjects and depended on the type of visual feedback provided to the subjects. First, while viewing a high-gain compensatory feedback display (horizontal bar moving up and down with force), 9 of 23 older subjects adopted a strategy of performing saccades during the task, which resulted in 2.5 times greater force fluctuations in those that exhibited saccades compared with those who maintained fixation near the target line. Second, during pursuit feedback displays (force trace moving left to right across screen and up and down with force), all subjects exhibited multiple saccades, and increased force fluctuations were associated (rs = 0.6; P = 0.002) with fewer saccades during the pursuit task. Also, decreased low-frequency (<4 Hz) force fluctuations and Grooved Pegboard times were significantly related (P = 0.033 and P = 0.005, respectively) with higher (i.e., better) attention z scores. Comparison of these results with our previously published results in young subjects indicates that saccadic eye movements and attention are related to force control in older adults.NEW & NOTEWORTHY The significant contributions of the study are the addition of eye movement data and an attention task to explain differences in hand motor control across different visual displays in older adults. Older participants used different visual strategies across varying feedback displays, and saccadic eye movements were related with motor performance. In addition, those older individuals with deficits in attention had impaired motor performance on two different hand motor control tasks, including the Grooved Pegboard test.

Essential and aging-related tremor: Differences of central control

For essential tremor, the distribution of age of onset is bimodally distributed, with peaks in adolescence and another in late adulthood. The latter is here referred to as aging-related tremor, and it is considered to be associated with earlier aging and increased mortality. We hypothesize that different tremor networks detected by multichannel electroencephalography (EEG) underlie these two tremor groups. We investigated 20 patients with essential tremor separated into two groups and 10 age- and sex-matched aging-related tremor patients using pooled coherence spectra of the maximally coherent EEG electrodes during a holding task, a pinch grip task, and whilst performing slow hand movements. Functional and effective connectivity at the coupling frequency was estimated. The maximal coherence was significantly higher in early-onset essential tremor compared with aging-related tremor during the three tasks. Compared with the patients with aging-related tremor, 2 Hz to 40 Hz power, spectral peak frequency, and relative signal-to-noise ratio were not different, but the electromyographic amplitude was significantly greater in essential tremor. The source analysis revealed the well-known cortico-brainstem-cerebello-thalamo-cortical network for classical essential tremor, but patients with aging-related tremor showed a cortico-thalamic network only. The connections between the sources for both tremors were bidirectional. Only the cerebellum and the brainstem showed unidirectional connections in essential tremor and the thalamus in aging-related tremor patients. A second essential tremor group with similar electromyographic amplitudes confirmed the differences between both tremor types. We show that the oscillating cerebral networks underlying classical essential tremor and aging-related tremor differ, suggesting a pathophysiological difference.

A virtual reality system integrated with robot-assisted haptics to simulate pinch-grip task: Motor ingredients for the assessment in chronic stroke.

Among numerous studies on virtual reality (VR) technology for motor rehabilitation, the majorities have only used it as a motor training system and did not use the kinematic or kinetic information obtained as the basis for therapeutic effect assessment. Incorporating the kinematic and kinetic information acquired through a robot-assisted VR system on pinch-grip training, this study intends to propose novel motor ingredients represented as indices for the interpretation of motor behaviors and verify the efficacy of them for the assessment in chronic stroke. Clinical trials were conducted on eight stroke patients and clinical assessments were made as the objective standard. Non-parametric test and correlation analysis were performed on results of motor indices and clinical assessments. Non-parametric test indicated that 50% of the motor indices significantly improved while the others showed a trend of improvement, consisting with the findings in clinical assessments. Correlation analysis showed that the three clinical assessment items were correlated to items in the motor ingredients. The proposed motor ingredients gathered from the robot-assisted VR training system were able to contribute to the assessment of therapeutic effect in chronic stroke and were capable for the interpretation of behavior phases.

Primary motor cortex disinhibition during motor skill learning

Motor learning requires practice over a period of time and depends on brain plasticity, yet even for relatively simple movements, there are multiple practice strategies that can be used for skill acquisition. We investigated the role of intracortical inhibition in the primary motor cortex (M1) during motor skill learning. Event-related transcranial magnetic stimulation (TMS) was used to assess corticomotor excitability and inhibition thought to involve synaptic and extrasynaptic γ-aminobutyric acid (GABA). Short intracortical inhibition (SICI) was assessed using 1- and 2.5-ms interstimulus intervals (ISIs). Participants learned a novel, sequential pinch-grip task on a computer in either a repetitive or interleaved practice structure. Both practice structures showed equivalent levels of motor performance at the end of acquisition and at retention 1 wk later. There was a novel task-related modulation of 1-ms SICI. Repetitive practice elicited a greater reduction of 1- and 2.5-ms SICI, i.e., disinhibition, between rest and task acquisition, compared with interleaved practice. These novel findings support the use of a repetitive practice structure for motor learning because the associated effects within M1 have relevance for motor rehabilitation.

Quantification of finger joint loadings using musculoskeletal modelling clarifies mechanical risk factors of hand osteoarthritis

Owing to limited quantitative data related to the loadings (forces and pressures) acting upon finger joints, several clinical observations regarding mechanical risk factors of hand osteoarthritis remain misunderstood. To improve the knowledge of this pathology, the present study used musculoskeletal modelling to quantify the forces and pressures acting upon hand joints during two grasping tasks.Kinematic and grip force data were recorded during both a pinch and a power grip tasks. Three-dimensional magnetic resonance imaging measurements were conducted to quantify joint contact areas. Using these datasets as input, a musculoskeletal model of the hand and wrist, including twenty-three degrees of freedom and forty-two muscles, has been developed to estimate joint forces and joint pressures.When compared with the power grip task, the pinch grip task resulted in two to eight times higher joint loadings whereas the grip forces exerted on each finger were twice lower. For both tasks, joint forces and pressures increased along a disto-proximal direction for each finger.The quantitative dataset provided by the present hand model clarified two clinical observations about osteoarthritis development which were not fully understood, i.e., the strong risk associated to pinch grip tasks and the high frequency of thumb-base osteoarthritis.

Corticomuscular coherence in asymptomatic first‐degree relatives of patients with essential tremor

Essential tremor (ET) follows an autosomal dominant type of inheritance in the majority of patients, yet its genetic basis has not been identified. Its exact origin is still elusive, but coherence measurements between electromyography tremor bursts and electroencephalography unequivocally demonstrate a correlation. We tested these measurements in 37 healthy first-degree relatives (children) of patients with essential tremor (ET) and a group of 37 age-matched and sex-matched controls. Pooled coherence spectra of the maximally coherent electroencephalogram electrodes were computed for ET relatives and controls. The maximal coherence and its frequency were significantly higher in ET relatives than in controls during the pinch grip task and during slow hand movements. Electromyography amplitude (root-mean-square) was slightly but significantly greater in ET relatives, whereas 2-Hz to 40-Hz power and spectral peak frequency were not different. The presymptomatic alteration in corticomuscular interaction may reflect a role of genetic factors.

The Effects of Age on Precision Pinch Force Control Across Five Days of Practice

The effects of age on control of fingertip forces, across five days of practice, were determined for an isometric precision pinch grip task. The task involved controlling a computer cursor so that it traveled upward and horizontally on a 45 degree template line by applying X-axis isometric force with contraction of the thumb, and Y-axis force with the index finger. Upon reaching a reverse circle target, the cursor was returned to the start by controlling the steady release of isometric force. Participants' control across the 6 segments of the template line (3 applying and 3 releasing force) was examined. Healthy participants comprised three age groups: Y20 (mean = 21 ± 4 years), O70 (mean = 70 ± 3 years) and O80 (mean = 79 ± 3 years). The results indicated that 1) overall the Y20 group was faster in completing the task than the O80 group, 2) age differences in task duration time (speed) increased over 4 days, 3) the Y20 and O70 groups, but not the O80 group, improved performance (increased accuracy and decreased within-participant variability for time and accuracy) with practice, 4) circle target proximity (segments 3 and 6) was a potent factor; all groups were slower, less accurate, and less consistent irrespective of force direction in the segments approaching a circle target goal (reverse/end). A task maneuver preceding a directional reversal of force modulation, from increasing to decreasing, was the most difficult element for the O80 group followed by the O70 and Y20 groups. These old adults improved tracing accuracy and consistency, but not performance speed with practice on this precision pinch force control task.

Methodological Advances in Brain Connectivity

Methodological Advances in Brain Connectivity

Impaired Discrimination of Sensory Information About Slip Between Object and Skin is Associated With Handgrip Limitation Poststroke

AbstractImpaired somatosensory processing could contribute to handgrip limitation following stroke. The aim of this study was to examine the association between somatosensory function measured by psychophysical tests and clinical measures of handgrip limitation poststroke. Forty-five people with stroke who could perform a pinch grip task were recruited from rehabilitation settings. Ability to discriminate surface friction, and to match object weight were quantified using psychophysical methods. Handgrip limitation was measured using items of the Motor Assessment Scale, Jebsen Taylor Hand Function Test and the Hand Function Survey. Impaired discrimination of surface friction was moderately to weakly associated with handgrip limitation (rs = .36 to .55). In contrast, an association between degree of impairment in matching weight and handgrip limitation poststroke was not observed (rs &lt; .24). The findings suggest that processing of tactile cues arising between the object and skin when training handgrip ability may be beneficial for people with stroke.

Clinical Measures of Handgrip Limitation Relate to Impaired Pinch Grip Force Control after Stroke

This study examined whether clinical measures of handgrip limitation relate to laboratory measures of grip force impairment during a pinch grip, lift, and hold task post-stroke. Handgrip ability in 45 people with stroke who had residual grip ability was examined relative to 45 age–matched healthy adults. The clinical tests included items from a) the Jebsen Taylor Hand Function Test; b) the Motor Assessment Scale; c) the Functional Independence Measure (FIM); and d) a custom-designed survey about hand-use in daily life. The laboratory test was summarized by principal components: 1) Pre-Lift Delay and 2) Grip Force Dyscontrol. For the stroke group, a moderate to strong correlation was found between Pre-Lift Delay and each clinical measure of handgrip limitation ( r s = 0.70–0.85) except the FIM ( r s = 0.38–0.49). In contrast, Grip Force Dyscontrol was not associated with handgrip limitation on any of the clinical tests ( r s = −0.08 to 0.18).