Proprioceptive Localization of the Hand Changes When Skin Stretch around the Elbow Is Manipulated

The efficacy of taping on elbow proprioception in healthy individuals: A single-blinded randomized placebo-controlled study

BACKGROUND

Taping stimulates the mechanoreceptors, increases sensory information to the central nervous system, and improves sensorimotor synchronization, resulting in improved motor control. However, the efficacy of taping on elbow proprioception is not clear.

PURPOSE

This study aimed to evaluate the immediate effects of taping on elbow proprioception in healthy individuals.

STUDY DESIGN

This study was a two-arm, parallel-group, randomized, controlled, single-blinded study with a sham application.

METHODS

Fifty six healthy adults were randomized 1:1 to kinesio taping (n = 27) or sham taping (n = 29). Active joint position sense error (JPSE) was used to quantify proprioception using a universal goniometer at three-time points: baseline (BS), immediately after taping (IA), and 30 minutes after taping (30MA), with the tape still in place at 70° and 110° of elbow flexion. Participants were blinded to group assignments. The Friedman analysis assessed differences between evaluations within groups, and the Mann-Whitney U test determined differences between groups.

RESULTS

The study was completed with 56 participants and there were no dropouts. No skin reaction or adverse effect was observed in the participants and no test trial was excluded. The baseline scores of the groups were similar (p > 0.05). A significant difference was detected in the study group after kinesio taping at 70° (MD = -1.22; CI = (-2.33: -0.10; p < 0.005; d = 0.653) and 110° of elbow flexion (MD = -1.34; CI = 2,47: -0,21; p < 0.005; d = 0.73). This statistically significant difference was observed even at the 30MA evaluations at 70° (p < 0.05). Also, there was a statistically insignificant tendency to decrease in JPSE of both groups at both degrees following taping.

CONCLUSIONS

Elbow proprioception may be enhanced by kinesio taping, and this effect could last up to 30 minutes at 70° of elbow flexion. In contrast, sham taping did not produce such an improvement. Based on the differences in JPSE, kinesio taping proved more effective and had a longer-lasting impact than the sham application. The statistically insignificant tendency to decrease in JPSE may indicate that the 30-minute application period is inadequate to create a statistically significant effect on elbow proprioception. Longer usage periods can better reveal the effects of orthoses on proprioception.

PIEZO2 ion channels in proprioception

PIEZO2 is a stretch-gated ion channel that is expressed at high levels in somatosensory neurons. Humans with rare mutations in the PIEZO2 gene have profound mechanosensory deficits that include a loss of the sense of proprioception. These striking phenotypes match those seen in conditional knockout mouse models demonstrating the highly conserved function for this gene. Here, we review the ramifications of loss of PIEZO2 function on normal daily activities and what studies like these have revealed about proprioception at the molecular and cellular level. Additionally, we highlight recent work that has uncovered the surprising functional and molecular diversity of proprioceptors. Together, these findings pioneer a path toward determining how the detection of mechanosensory input from muscles and tendons is used to control posture and refine motor performance.

Heating the Skin Over the Knee Improves Kinesthesia During Knee Extension

To determine how heating affects dynamic joint position sense at the knee, participants (n = 11; F = 6) were seated in a HUMAC NORM dynamometer. The leg was passively moved through extension and flexion, and participants indicated when the 90° reference position was perceived, both at baseline (28.74 ± 2.43 °C) and heated (38.05 ± 0.16 °C) skin temperatures. Day 2 of testing reduced knee skin feedback with lidocaine. Directional error (actual leg angle–target angle) and absolute error (AE) were calculated. Heating reduced extension AE (baseline AE = 5.46 ± 2.39°, heat AE = 4.10 ± 1.97°), but not flexion. Lidocaine did not significantly affect flexion AE or extension AE. Overall, increased anterior knee-skin temperature improves dynamic joint position sense during passive knee extension, where baseline matching is poorer. Limited application of lidocaine to the anterior thigh, reducing some skin input, did not influence dynamic joint position sense, suggesting cutaneous receptors may play only a secondary role to spindle information during kinesthetic tasks. Importantly, cutaneous input from adjacent thigh regions cannot be ruled out as a contributor.

Proprioceptive Acuity is Enhanced During Arm Movements Compared to When the Arm is Stationary: A Study of Young and Older Adults

Proprioception in old age is thought to be poorer due to degeneration of the central (CNS) and peripheral nervous systems (PNS). We tested whether community-dwelling older adults (65-83 years) make larger proprioceptive errors than young adults (18-22 years) using a natural reaching task. Subjects moved the right arm to touch the index fingertip to the stationary or moving left index fingertip. The range of locations of the target index fingertip was large, sampling the natural workspace of the human arm. The target arm was moved actively by the subject or passively by the experimenter and reaching arm movements towards the target were made under visual guidance, or with vision blocked (proprioceptive guidance). Subjects did not know the direction or speed of upcoming target hand motion in the passive conditions. Mean 3D distance errors between the right and left index finger tips were small in both groups and only slightly larger when vision was blocked than when allowed, but averaged 2-5 mm larger in older than in younger adults in moving (p = 0.002) and stationary (p = 0.07) conditions, respectively. Variable errors were small and similar in the two groups (p > 0.35). Importantly, clearly larger errors were observed for reaching to the stationary than to the moving index fingertip in both groups, demonstrating that dynamic proprioceptive information during movement permits more accurate localization of the endpoint of the moving arm. This novel finding demonstrates the importance of dynamic proprioceptive information in movement guidance and bimanual coordination.

Looking away from a moving target does not disrupt the way in which the movement toward the target is guided

People usually follow a moving object with their gaze if they intend to interact with it. What would happen if they did not? We recorded eye and finger movements while participants moved a cursor toward a moving target. An unpredictable delay in updating the position of the cursor on the basis of that of the invisible finger made it essential to use visual information to guide the finger's ongoing movement. Decreasing the contrast between the cursor and the background from trial to trial made it difficult to see the cursor without looking at it. In separate experiments, either participants were free to hit the target anywhere along its trajectory or they had to move along a specified path. In the two experiments, participants tracked the cursor rather than the target with their gaze on 13% and 32% of the trials, respectively. They hit fewer targets when the contrast was low or a path was imposed. Not looking at the target did not disrupt the visual guidance that was required to deal with the delays that we imposed. Our results suggest that peripheral vision can be used to guide one item to another, irrespective of which item one is looking at.

Interjoint coupling of position sense reflects sensory contributions of biarticular muscles

Perception of limb position and motion combines sensory information from spindles in muscles that span one joint (monoarticulars) and two joints (biarticulars). This anatomical organization should create interactions in estimating limb position. We developed two models, one with only monoarticulars and one with both monoarticulars and biarticulars, to explore how biarticulars influence estimates of arm position in hand (x, y) and joint (shoulder, elbow) coordinates. In hand coordinates, both models predicted larger medial-lateral than proximal-distal errors, although the model with both muscle groups predicted that biarticulars would reduce this bias. In contrast, the two models made significantly different predictions in joint coordinates. The model with only monoarticulars predicted that errors would be uniformly distributed because estimates of angles at each joint would be independent. In contrast, the model that included biarticulars predicted that errors would be coupled between the two joints, resulting in smaller errors for combinations of flexion or extension at both joints and larger errors for combinations of flexion at one joint and extension at the other joint. We also carried out two experiments to examine errors made by human subjects during an arm position matching task in which a robot passively moved one arm to different positions and the subjects moved their other arm to mirror-match each position. Errors in hand coordinates were similar to those predicted by both models. Critically, however, errors in joint coordinates were only similar to those predicted by the model with monoarticulars and biarticulars. These results highlight how biarticulars influence perceptual estimates of limb position by helping to minimize medial-lateral errors.NEW & NOTEWORTHY It is unclear how sensory information from muscle spindles located within muscles spanning multiple joints influences perception of body position and motion. We address this issue by comparing errors in estimating limb position made by human subjects with predicted errors made by two musculoskeletal models, one with only monoarticulars and one with both monoarticulars and biarticulars. We provide evidence that biarticulars produce coupling of errors between joints, which help to reduce errors.

Proprioceptive Localization of the Fingers: Coarse, Biased, and Context-Sensitive

The proprioceptive sense provides somatosensory information about positions of parts of the body, information that is essential for guiding behavior and monitoring the body. Few studies have investigated the perceptual localization of individual fingers, despite their importance for tactile exploration and fine manipulation. We present two experiments assessing the performance of proprioceptive localization of multiple fingers, either alone or in combination with visual cues. In the first experiment, we used a virtual reality paradigm to assess localization of multiple fingers. Surprisingly, the errors averaged 3.7 cm per digit, which represents a significant fraction of the range of motion of any finger. Both random and systematic errors were large. The latter included participant-specific biases and participant-independent distortions that evoked similar observations from prior studies of perceptual representations of hand shape. In a second experiment, we introduced visual cues about positions of nearby fingers, and observed that this contextual information could greatly decrease localization errors. The results suggest that only coarse proprioceptive information is available through somatosensation, and that finer information may not be necessary for fine motor behavior. These findings may help elucidate human hand function, and inform new applications to the design of human-computer interfaces or interactions in virtual reality.

Spatial and temporal influences on discrimination of vibrotactile stimuli on the arm

Body-machine interfaces (BMIs) provide a non-invasive way to control devices. Vibrotactile stimulation has been used by BMIs to provide performance feedback to the user, thereby reducing visual demands. To advance the goal of developing a compact, multivariate vibrotactile display for BMIs, we performed two psychophysical experiments to determine the acuity of vibrotactile perception across the arm. The first experiment assessed vibration intensity discrimination of sequentially presented stimuli within four dermatomes of the arm (C5, C7, C8, and T1) and on the ulnar head. The second experiment compared vibration intensity discrimination when pairs of vibrotactile stimuli were presented simultaneously vs. sequentially within and across dermatomes. The first experiment found a small but statistically significant difference between dermatomes C7 and T1, but discrimination thresholds at the other three locations did not differ. Thus, while all tested dermatomes of the arm and hand could serve as viable sites of vibrotactile stimulation for a practical BMI, ideal implementations should account for small differences in perceptual acuity across dermatomes. The second experiment found that sequential delivery of vibrotactile stimuli resulted in better intensity discrimination than simultaneous delivery, independent of whether the pairs were located within the same dermatome or across dermatomes. Taken together, our results suggest that the arm may be a viable site to transfer multivariate information via vibrotactile feedback for body-machine interfaces. However, user training may be needed to overcome the perceptual disadvantage of simultaneous vs. sequentially presented stimuli.

When Non-Dominant Is Better than Dominant: Kinesiotape Modulates Asymmetries in Timed Performance during a Synchronization-Continuation Task

There is a growing consensus regarding the specialization of the non-dominant limb (NDL)/hemisphere system to employ proprioceptive feedback when executing motor actions. In a wide variety of rhythmic tasks the dominant limb (DL) has advantages in speed and timing consistency over the NDL. Recently, we demonstrated that the application of Kinesio^® Tex (KT) tape, an elastic therapeutic device used for treating athletic injuries, improves significantly the timing consistency of isochronous wrist’s flexion-extensions (IWFEs) of the DL. We argued that the augmented precision of IWFEs is determined by a more efficient motor control during movements due to the extra-proprioceptive effect provided by KT. In this study, we tested the effect of KT on timing precision of IWFEs performed with the DL and the NDL, and we evaluated the efficacy of KT to counteract possible timing precision difference between limbs. Young healthy subjects performed with and without KT (NKT) a synchronization-continuation task in which they first entrained IWFEs to paced auditory stimuli (synchronization phase), and subsequently continued to produce motor responses with the same temporal interval in the absence of the auditory stimulus (continuation phase). Two inter-onset intervals (IOIs) of 550-ms and 800-ms, one within and the other beyond the boundaries of the spontaneous motor tempo, were tested. Kinematics was recorded and temporal parameters were extracted and analyzed. Our results show that limb advantages in performing proficiently rhythmic movements are not side-locked but depend also on speed of movement. The application of KT significantly reduces the timing variability of IWFEs performed at 550-ms IOI. KT not only cancels the disadvantages of the NDL but also makes it even more precise than the DL without KT. The superior sensitivity of the NDL to use the extra-sensory information provided by KT is attributed to a greater competence of the NDL/hemisphere system to rely on sensory input. The findings in this study add a new piece of information to the context of motor timing literature. The performance asymmetries here demonstrated as preferred temporal environments could reflect limb differences in the choice of sensorimotor control strategies for the production of human movement.