The contribution of gravitational torques to limb position sense

Summary An experiment is reported which examined whether gravitational torque acting about a joint is used by the CNS in elbow joint angle matching. Subjects were required to match the joint angles of their two limbs while the external torques acting about each elbow were systematically varied. It was found that when the matching limb was differentially loaded, the error in the produced reference angle corresponded to the directional prediction of a proposed gravitational torque hypothesis. The data suggest that torque sensation is an accessory source of information in limb positioning.This research was partially supported by grants from NATO Scientific Affiars Division, RG82/0227 and US Public Health Service, NS17421 and AG05154 awarded to G. E. Stelmach     

The precision of proprioceptive position sense

The purpose of this study was to determine the precision of proprioceptive localization of the hand in humans. We derived spatial probability distributions which describe the precision of localization on the basis of three different sources of information: proprioceptive information about the left hand, proprioceptive information about the right hand, and visual information. In the experiment subjects were seated at a table and had to perform three different position-matching tasks. In each task, the position of a target and the position of an indicator were available in a different combination of two of these three sources of information. From the spatial distributions of indicated positions in these three conditions, we derived spatial probability distributions for proprioceptive localization of the two hands and for visual localization. For proprioception we found that localization in the radial direction with respect to the shoulder is more precise than localization in the azimuthal direction. The distributions for proprioceptive localization also suggest that hand positions closer to the shoulder are localized more precisely than positions further away. These patterns can be understood from the geometry of the arm. In addition, the variability in the indicated positions suggests that the shoulder and elbow angles are known to the central nervous system with a precision of 0.6–1.1°. This is a considerably better precision than the values reported in studies on perception of these angles. This implies that joint angles, or quantities equivalent to them, are represented in the central nervous system more precisely than they are consciously perceived. For visual localization we found that localization in the azimuthal direction with respect to the cyclopean eye is more precise than localization in the radial direction. The precision of the perception of visual direction is of the order of 0.2–0.6°. Received: 3 July 1997 / Accepted: 27 March 1998     

Influence of hysteresis on joint position sense in the human knee joint

During muscle lengthening in a movement cycle the firing rate of muscle spindles is higher than during shortening. This phenomenon, known as hysteresis, has implications for movement control. Therefore, it should have an impact on joint position sense (JPS), the subject's awareness of the static position of a joint. JPS has been tested on the human knee joint by means of an angle reproduction test. This task included the following sequences. The leg was moved passively, by means of a motor drive, from two different start positions (15 degrees and 75 degrees) to a certain target angle and, after a time of 8 s, it was returned to the start position; subjects had to reproduce the former target angle. Several target angles, mild flexion (30 degrees), intermediate flexion (45 degrees), and strong flexion (60 degrees), were used. Depending on the start position, the movements matching these targets were flexions or extensions. At least for the intermediate position different threshold values should be expected for flexions and extensions, if hysteresis has an impact. Moreover, the JPS measure should show a dependence on movement velocity and independence on distance. Of the variables tested, only movement direction but not movement velocity or distance had a statistically significant impact on the dependent constant angle error (difference between reproduction and target angle). The target angle of 30 degrees was exactly reproduced (-0.14 degrees), independently of the start position. The 45 degrees target angle was significantly underestimated (-4.39 degrees) when matching that position by flexions (starting at 15 degrees) compared to an overestimation (2.27 degrees) when matching that position by extensions (starting at 75 degrees). The target angle of 60 degrees has been constantly underestimated (-3.80 degrees), independently of the start position. Therefore, hysteresis, the dependency of the movement's direction, neglected in the past, should be considered in future tests of JPS or studies considering the role of movement parameters for motor control.     

Position sense asymmetry

Asymmetries in upper limb position sense have been explained in the context of a left limb advantage derived from differences in hemispheric specialization in the processing of kinesthetic information. However, it is not clearly understood how the comparison of perceptual information associated with passive limb displacement and the corresponding matching movement resulting from the execution of a motor command contributes to these differences. In the present study, upper limb position sense was investigated in 12 right-hand-dominant young adults performing wrist position matching tasks which varied in terms of interhemispheric transfer, memory retrieval and whether the reference position was provided by the same or opposite limb. Right and left hand absolute matching errors were similar when the reference and matching positions were produced by the same hand but were 36% greater when matching the reference position with the opposite hand. When examining the constant errors generated from matching movements made with the same hand that provided the reference, the right and left hand matching errors (≈3°) were similar. However, when matching with the opposite limb, a large overshoot (P < 0.05) characterized the error when the right hand matched the left hand reference while a large undershoot (P < 0.05) characterized the error when the left hand matched the right hand reference. The overshoot and undershoot were of similar magnitude (≈4°). Although asymmetries in the central processing of proprioceptive information such as interhemispheric transfer may exist, the present study suggests that asymmetries in position sense predominantly result from a difference in the “gain of the respective proprioceptive sensory-motor loops”. This new hypothesis is strongly supported by a dual-linear model representing the right and left hand sensory-motor systems as well as morphological and physiological data.     

Perception of limb orientation in the vertical plane depends on center of mass rather than inertial eigenvectors

We performed two experiments to test the hypothesis that the perception of limb orientation depends on inertial eigenvectors (e _i ) against the alternative hypothesis that it depends on the center of mass vector (CM). Whereas e _i constrains the dynamic torques involved in angular rotation, CM constrains the static torque necessary to keep the limb aloft in the gravitational field. Hence, possible effects of e _i and CM on kinesthetic judgments must be related to the dynamic and static torques, respectively, involved in moving and positioning a limb. In the first experiment, blindfolded participants matched, with upper arms supported, the orientation of their forearms while the forearms’ e _i and CM were manipulated relative to the elbow. The manipulation of the vector CM alone induced a matching bias, as did the combined manipulation of e _i and CM, whereas the manipulation of e _i alone did not. In the second experiment, participants positioned their unseen and unsupported right arm at an indicated spatial configuration while e _i and CM of the right forearm were manipulated as in Experiment 1. As in the first experiment, forearm positioning was affected by the independent manipulation of CM and the combined manipulation of e _i and CM, but not by the independent variation of e _i . Moreover, none of the manipulations affected upper arm positioning. These results refute the claim that the perception of limb orientation (in the vertical plane) is based on e _i and demonstrate, for the first time, the implication of a limb segment’s CM in the perception of its orientation. This research was supported in part by The Netherlands Organization for Scientific Research (NWO) Grant 402-01-040.     

The combined effect of muscle contraction history and motor commands on human position sense

Along with afferent information, centrally generated motor command signals may play a role in joint position sense. Isometric muscle contractions can produce a perception of joint displacement in the same direction as the joint would move if unrestrained. Contradictory findings of perceived joint displacement in the opposite direction have been reported. As this only occurs if muscle spindle discharge in the contracting muscle is initially low, it may reflect increased muscle spindle firing from fusimotor activation, rather than central motor command signals. Methodological differences including the muscle contraction task and use of muscle conditioning could underlie the opposing findings. Hence, we tested perceived joint position during two contraction tasks (‘hold force’ and ‘hold position’) at the same joint (wrist) and controlled muscle spindle discharge with thixotropic muscle conditioning. We expected that prior conditioning of the contracting muscle would eliminate any effect of increased fusimotor activation, but not of central motor commands. Muscle conditioning altered perceived wrist position as expected. Further, during muscle contractions, subjects reported wrist positions displaced ~12° in the direction of contraction, despite no change in wrist position. This was similar for ‘hold force’ and ‘hold position’ tasks and occurred despite prior conditioning of the agonist muscle. However, conditioning of the antagonist muscle did reduce the effect of voluntary contraction on position sense. The errors in position sense cannot be explained by fusimotor activation. We propose that central signals combine with afferent signals to determine limb position and that multiple sources of information are weighted according to their reliability.     

On the form of the internal model for reaching

We investigated, by using simulations, possible mechanisms responsible for the errors in the direction of arm movements exhibited by deafferented patients. Two aspects of altered feedforward control were evaluated: the inability to sense initial conditions and the degradation of an internal model. A simulation which assumed no compensation for variations in initial arm configuration failed to reproduce the characteristic pattern of errors. In contrast, a simulation that assumed random variability in the generation of joint torque resulted in a distribution of handpaths which resembled some aspects of the pattern of errors exhibited by deafferented patients.     

A metric for assessing acuity in positioning joints and limbs

In this paper, we present a method for assessing the exactness of sensing and setting the positions of joints and limbs, using a measure we call target resolution. Target resolution, derived from information theory but ultimately based on variance, estimates the fewest number of discrete, equally spaced targets required within a range to provide the maximum possible information transfer from any target set. We argue that target resolution provides better insight into the exactness of position sense than does the usual measure of accuracy based on mean or constant error. Studies have shown that measures of mean error in setting or indicating positions of joints or limbs exhibit lability; they drift and show considerable sensitivity to factors such as previous positions of the limb and learning. We derive the equation for calculating target resolution and give example resolutions for several joints we have tested. Target resolution often gives a quite different impression of proprioceptive exactness than do measures of accuracy based on mean error.     

Influence of age on dynamic position sense: evidence using a sequential movement task

Age related changes to the nervous system are well documented. The main objectives of this study were to examine age-associated changes in dynamic position sense and relate these changes to measures of balance and physical function. Two groups of individuals (young <30 years; elderly >60 years) performed an upper extremity movement sequence triggered by a pre-determined target angle during passive rotations of the ankle joint at ten random velocities (10–90° s^–1). Balance was assessed with a series of timed standing tests. Physical function was assessed with the SF 36 questionnaire. Muscle activity was recorded from the ankle dorsiflexors and plantarflexors during the dynamic position tests. Increased error in the elderly group suggested that dynamic position sense declines with age. Moreover, this decline in dynamic position sense was associated with decreased balance and an impaired perception of physical function. The elderly also co-contracted the ankle plantarflexors and dorsiflexors during the proprioceptive testing, perhaps as a strategy to gain up spindle sensitivity. These findings suggest that impaired dynamic position sense of the ankle contributes to alterations in the overall physical function and balance in the elderly. Rehabilitative training methods that improve dynamic position sense of the ankles may improve physical function and balance in the elderly.     

Estimation of Musculotendon Properties in the Human Upper Limb

The purpose of this study was to develop and apply a general method for estimating the architectural properties of human muscles in vivo. The method consists of a two-phase, nested optimization procedure in which the values of peak isometric force, optimal muscle-fiber length, and tendon slack length are calculated for each musculotendon actuator, knowing muscle volume and the minimum and maximum physiological lengths of the actuator. In phase I, the positions of the bones and the activation levels of the muscles are found by maximizing the isometric torque developed for each degree of freedom at each joint. In phase II, the architectural properties of each musculotendon actuator are found by matching the strength profile of the model to that measured for subjects. The method is used to estimate the architectural properties of 26 major muscle groups crossing the shoulder, elbow, and wrist. Wherever possible, the model calculations are compared against measurements obtained from anatomical studies reported in the literature. Architectural data obtained from our work should be useful to researchers interested in developing musculoskeletal models of the upper limb. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr, 8710+e, 8719Ff     

Skin sensory information from the dorsum of the foot and ankle is necessary for kinesthesia at the ankle joint

Previous research has shown that skin is capable of providing kinesthetic cues at particular joints but we are unsure how these cues are used by the central nervous system. The current study attempted to identify the role of skin on the dorsum of the ankle during a joint matching task. A 30 cm patch of skin was anesthetized and matching accuracy in a passive joint matching task was compared before and after skin anesthetization. Goniometers were used to measure ankle angular displacement. Four target angles were used in the matching task, 7° of dorsiflexion, 7°, 14° and 21° of plantarflexion. We hypothesized that, based on the location of skin anesthetized, only the plantarflexion matching tasks would be affected. Absolute error (accuracy) increased significantly for all angles when the skin was anesthetized. Directional error indicated that overall subjects tended to undershoot the target angles, significantly more so for 21° of plantarflexion when the skin was anesthetized. Following anesthetization, variable error (measure of task difficulty) increased significantly at 7° of dorsiflexion and 21° of plantarflexion. These results indicate that the subjects were less accurate and more variable when skin sensation was reduced suggesting that skin information plays an important role in kinesthesia at the ankle.     

Models of behaviors when detecting displacements of joints

This report describes two models of human behavior when detecting displacements of joints that allow one to compare and integrate findings from different proprioception tests in a quantitative way. Results from various tests have led to different and often conflicting conclusions about proprioceptive behaviors and their underlying neural mechanisms. However, it has been impossible to compare data and conclusions in any meaningful way due to lack of a suitable analytical framework to accommodate important differences in procedures used in the various tests. These models can provide one such framework. The models, developed using data from proprioception tests reported in the literature, describe how the amplitude and velocity of joint excursions, and the subject bias expressed as false alarm rate, affect the detectability of displacements of joints. Two models were needed to represent observed behaviors: one based on velocity signals alone (the velocity model) and the other based on both velocity and positional signals (the displacement-velocity model). To simulate the detection-decision process subjects used to determine whether a joint was displaced, we adapted strategies from signal detection theory. The models characterized reported behaviors from disparate proprioception tests remarkably well, requiring only 3 degrees of freedom in the velocity case, and 4 in the displacement-velocity case.     

Stochastic resonance electrical stimulation to improve proprioception in knee osteoarthritis

Proprioceptive deficits occur with knee osteoarthritis (OA) and improving proprioception may slow joint degeneration by allowing more appropriate joint loading. Stochastic resonance (SR) stimulation improves balance and the sensitivity of specific mechanoreceptors. Our purpose was to evaluate the effects of SR electrical stimulation combined with a knee sleeve on proprioception in subjects with knee OA. Joint position sense (JPS) was measured in 38 subjects with knee OA during four conditions in both a partial weight-bearing (PWB) and non weight-bearing (NWB) task: no electrical stimulation/no sleeve, no electrical stimulation/sleeve, 50 μA-RMS stimulation/sleeve, and 75 μA-RMS stimulation/sleeve. Subjects also reported their knee pain, stiffness, functionality (WOMAC), and instability. Repeated measures ANOVA and Spearman correlations were performed to investigate differences between the conditions and relationships among the outcome measures. JPS during the 75 μA-RMS stimulation/sleeve and sleeve alone conditions was significantly improved compared to the control condition in the PWB task. However, the 75 μA-RMS stimulation/sleeve and the sleeve alone conditions did not differ from each other. A moderate correlation was found between the improvements with the 75 μA-RMS stimulation/sleeve condition compared to the JPS of the control condition in the PWB task. No differences in JPS were found between the four conditions in the NWB task. Significant correlations were found between the control JPS and WOMAC indices (p < 0.005). Improved proprioception during the PWB task was achieved with a sleeve alone and in combination with SR stimulation. The observed correlations suggest that subjects with larger proprioceptive deficits may benefit most from these therapies.     

Effect of exercise-induced fatigue on position sense of the knee in the elderly

Previously, data on the effects of muscle fatigue on joint position sense (JPS) have been provided. However, to our knowledge, no studies have been conducted so far to assess the effects of local muscle fatigue on elderly proprioception. Thus, the purpose of the present study was to determine the effects of local muscle fatigue on knee JPS in old-age-subjects. Sixteen male volunteers (mean age ± SD: 69.81 ± 3.92 years) participated in this study. Each subject completed all of the data collection in one morning session; JPS measures were obtained prior to and immediately after the fatigue protocol. JPS was evaluated by the technique of open-kinetic chain and active knee positioning, and was reported using absolute, relative and variable angular errors. The fatigue protocol applied to the lower extremity consisted of 30 maximum concentric repetitions of the knee extensors and flexors muscles on an isokinetic dynamometer at an angular velocity of 120 s⁻¹ (2.09 rad s⁻¹). The results showed that peak torque of knee extensor and flexor muscles was significantly decreased from rest to post exercise-induced fatigue. After local load to the knee muscles, a significant increase of absolute angular error was observed (2.56°). The relative error showed the directional bias in the extension movement. However, the reliability and accuracy of estimating knee angles as showed by the variable error is similar at both times. It can be concluded that exercise-induced local muscle fatigue alters knee JPS in old age adults.     

The influence of sports practice,dominance and gender on the knee joint position sense

BackgroundPhysical activity, muscle fatigue or age have been suggested as factors that positively or negatively influence the knee joint position sense (KJPS). However, conflicting results about the influence of sports practice, limb dominance and gender are found in the literature. This study aimed to assess the influence of sports practice, limb dominance and gender on the KJPS of soccer players and untrained individuals.MethodologySixty subjects participated in this study: 29 soccer players (SPs) and 31 untrained participants (UPs). KJPS was tested in a seated position, for the target angles of 20° and 45° of knee flexion, through an open kinetic chain technique and active repositioning method. Intergroup analysis was performed to compare KJPS between SPs and UPs and between gender, and intragroup analysis was performed to compare proprioceptive acuity between dominant and non-dominant limbs.ResultsKnee repositioning errors were lower in SPs than in the UPs. Repositioning errors of the dominant and non-dominant limb were not significantly different in SPs (P > 0.05), but in UPs the dominant limb showed significantly lower repositioning errors, both for 20° (P = 0.046) and 45° target (P = 0.036). There were no gender differences in the KJPS in both groups (P > 0.05).ConclusionsProprioceptive acuity is higher in trained than in untrained participants. Dominance seems not to influence KJPS of SPs, but in UPs the dominant limb showed a higher accuracy. There were no differences in KJPS related to gender. These results suggest that sports practice, but neither gender nor limb dominance, may positively influence proprioceptive acuity.     

Validity and reliability of smartphones in measuring joint position sense among asymptomatic individuals and patients with knee osteoarthritis: A cross-sectional study

BackgroundQuantifying proprioception deficit in patients with osteoarthritis (OA) may be important in evaluating treatment effectiveness. This study investigated the concurrent and known-groups validity as well as test–retest reliability of a smartphone application in assessing joint position sense (JPS) in asymptomatic individuals and patients with knee OA.MethodsSixty-four knees, from 16 asymptomatic controls and 16 patients with bilateral OA, were assessed twice with a 1-week interval in between. The smartphone Goniometer Pro application and isokinetic dynamometer simultaneously quantified JPS, in terms of absolute repositioning error (RE) angle, during active and passive limb movements at selected angles.ResultsBoth devices showed moderate to almost perfect correlations in measuring JPS; whether active (intra-class correlation coefficient (ICC) >0.87) or passive (ICC >0.97). The mean RE angle differences between the two devices were <0.77° (passive JPS) and <2.76° (active JPS). Both devices were capable of distinguishing patients and asymptomatic controls at 55° and 80°. The smartphone showed moderate test–retest reliability of active JPS measurement (ICC = 0.51) in the two groups, similar to that of the isokinetic dynamometer (ICC = 0.62), but with a high measurement error.ConclusionsSmartphone application is a valid alternative to the isokinetic dynamometer in assessing JPS in patients with knee OA and asymptomatic controls. The two devices could distinguish patients and asymptomatic volunteers during passive JPS measured at 55° and 80°. Both devices have moderate reliability in quantifying active JPS, but reliability results should be considered with caution.     

Changes in head and neck position affect elbow joint position sense

Changes in the position of the head and neck have been shown to introduce a systematic deviation in the end-point error of an upper limb pointing task. Although previous authors have attributed this to alteration of perceived target location, no studies have explored the effect of changes in head and neck position on the perception of limb position. This study investigated whether changes in head and neck position affect a specific component of movement performance, that is, the accuracy of joint position sense (JPS) at the elbow. Elbow JPS was tested with the neck in four positions: neutral, flexion, rotation and combined flexion/rotation. A target angle was presented passively with the neck in neutral, after a rest period; this angle was reproduced actively with the head and neck in one of the test positions. The potential effects of distraction from head movement were controlled for by performing a movement control in which the head and neck were in neutral for the presentation and reproduction of the target angle, but moved into flexion during the rest period. The absolute and variable joint position errors (JPE) were greater when the target angle was reproduced with the neck in the flexion, rotation, and combined flexion/rotation than when the head and neck were in neutral. This study suggests that the reduced accuracy previously seen in pointing tasks with changes in head position may be partly because of errors in the interpretation of arm position.     

Effect of whole body vibration exercise on muscle strength and proprioception in females with knee osteoarthritis

The purpose of this study was to assess the effect of whole body vibration (WBV) exercise on muscle strength and proprioception in female patients with osteoarthritis in the knee (knee-OA). A single blinded, randomised, controlled trial was performed in an outpatient clinic on 52 female patients diagnosed with knee-OA (mean age 60.4 years ± 9.6). They were randomly assigned to one of 3 groups: 1. WBV-exercise on a stable platform (VibM; n = 17 (mean age, 61.5 ± 9.2)), WBV-exercise on a balance board (VibF; n = 18 (mean age, 58.7 ± 11.0)), or control group (Con; n = 18 (mean age, 61.1 ± 8.5)).The WBV groups trained twice a week for 8 weeks, with a progressively increasing intensity. The WBV groups performed unloaded static WBV exercise.The following were measured: knee muscle strength (extension/flexion) and proprioception (threshold for detection of passive movement (TDPM)). Self-reported disease status was measured using WOMAC.It was found that muscle strength increased significantly (p < 0.001) in VibM compared to Con. Isometric knee-extension significantly increased (p = 0.021) in VibM compared to Con. TDPM was significantly improved (p = 0.033) in VibF compared to Con, while there was a tendency (p = 0.051) for VibM to perform better compared to Con. There were no effects in the self-reported disease status measures.This study showed that the WBV-exercise regime on a stable platform (VibM) yielded increased muscle strength, while the WBV-exercise on a balance board (VibF) showed improved TDPM. The WBV-exercise is a time-saving and safe method for rehabilitation of women with knee-OA.     

The role of proprioception in the control of prehension movements: a kinematic study in a peripherally deafferented patient and in normal subjects

In this study we investigated the role of proprioception in the control of prehension movements, with particular reference to the grasp component. Grasp and transport kinematics were studied in a peripherally deafferented patient and in five healthy subjects. Two experiments were carried out: the prehension experiment and the grasp perturbation experiment. In the prehension experiment both the patient and the control subjects were required to reach and grasp three objects of different size, located at three different distances, both with and without visual feedback. In the grasp perturbation experiment a mechanical perturbation was applied to the fingers during prehension movements, again executed with and without visual feedback. In the prehension experiment temporal parameters of the patient's movements were generally slowed, with greater variability on some measures. However, over the first phase of the movement the pattern of the patient's hand opening and transport acceleration, scaled to object size and distance, was the same as that of controls, both with and without visual feedback. On the contrary, during the final phase of the movement (the finger closure phase and deceleration) the patient's performance differed significantly from the controls. These phases were abnormally lengthened and frequent movement adjustments were observed. In the grasp perturbation experiment the patient was not able to compensate for the perturbations applied to the fingers, even with visual feedback. The data allowed us to investigate also the respective contribution of proprioception and of vision of the hand in the control of prehension. We compared prehension kinematics in two conditions: (a) with visual but no proprioceptive feedback (in the patient) and (b) with proprioceptive but no visual feedback (in the controls). In both experiments proprioceptive control was more efficient than visual control. The results of this study are interpreted in favour of the strict dependence of prehension control on proprioception. The first phase of the movement, however, can be appropriately planned and executed without the necessity of either proprioceptive or visual information about the hand.     

Disturbed proprioception following a period of muscle vibration in humans

Forearm position matching tasks were performed by blindfolded subjects before and after applying vibration for 60 s to the biceps or triceps muscle of one arm. Following cessation of vibration, statistically significant alignment (proprioceptive) errors occurred when a movement lengthened the previously vibrated muscle. The error was such that the length of the post-vibrated muscle was greater than the length of the same muscle in the non-vibrated arm. This effect is the opposite to that which occurs during vibration.