Contribution of neck proprioception to subjective vertical perception among experts in physical activities and untrained women

Visual dependency and postural control on swing performance in golf players

Individuals have to reweight the respective contribution of the different sources of sensorial information for regulating posture and balance, especially during fine task execution. Given the evidences indicating strategy during swing performance as associated with prioritization of task-relevant visuospatial information for skill execution, the aim of the present work is to assess differences in visual dependency (VD) and postural control in a population of expert (EXP) and non-expert (NEXP) golfers when compared with healthy subjects (HC) and to discover possible relationships between these outcomes and swing performance. Thus, 15 golfers (EXP = 7; NEXP = 8) and 32 matched HC underwent otoneurological testing including video Head Impulse Test, posturography and Rod and Disk Test (RDT). Golf players also underwent a swing session procedure, which performance was measured by means of the Flightscope X2 Doppler-radar launch monitor system. EXP subjects demonstrated significant (p < 0.05) lower values in i) counter-clockwise (CCW) and clockwise (CW) dynamic conditions when compared with both NEXP and HC subjects RDT outcome measures and ii) surface and length posturography values as compared with HC subjects. When treating golf players outcomes as 'a continuum', CCW and CW scores were found to positively correlate with both lateral distance and horizontal launch angle and to negatively correlate with spin rpm. In conclusion, the present study suggests that the high-level of visual-independency demonstrated by EXP subjects may be functionally related in expert golfers to an effective motor strategy preferentially not referring to an inappropriate reliance on visual input.

Rod and frame test and posture under optokinetic stimulation used to explore two complementary aspects of the visual influence in postural control after stroke

BACKGROUND

Balance rehabilitation should consider individual comportments according to visual input (VI). Indeed, visual dependence (VD), defined as the predominance given to the VI whatever the circumstances, frequent after stroke it could disturb balance. Because the term VD is a bit restrictive and cannot be deduced from clinical tests, the term visual sensitivity (VS) is preferred here.

HYPOTHESIS

VI could have different influence depending on the task for a given individual.

METHODS

We retrospectively compared 2 VS tests routinely used: the rod and frame test (RFT) and optokinetic stimulation (OKS). In RFT, VS was defined by a misperception of the visual verticality induced by a tilted frame (VS RFT) and in OKS by tilted sitting posture induced by rotational OKS (VS OKS). We studied the relations between VS RFT and VS OKS.

RESULTS

We analysed data for 84 patients, mean age 55±10years, 45±30days after stroke. Scores for both tests were correlated with autonomy measured by the functional independence measure (r=-0.3, p=0.01 and r=-0.2, p=0.02). VS OKS score was also correlated with balance measured by the postural assessment scale for stroke (r=-0.3, p=0.03). VS RFT score was not correlated with VS OKS score (p=0.4, r=0.04).

DISCUSSION - CONCLUSION

A patient may display VS for one test without sensitivity for the other because these tests investigate different neural organisation - perception for RFT or action for OKS. Their relation to balance disorders should be further investigated to build individualized rehabilitation programs.

Laterality of proprioception in the orofacial muscles and temporomandibular joint

Laterality of function in the orofacial musculature suggests there may be side-to-side asymmetry of proprioceptive acuity in lip movement compared to the temporomandibular joint (TMJ). In the present work, 14 young adults were tested for acuity of lip and TMJ closure movements onto plugs varying from 5 to 8mm without visual feedback. Testing was conducted on both left and right sides, using the same psychophysical task and stimuli. Results showed superior proprioceptive acuity at the lips, with no significant side effect. However, there was side-to-side asymmetry in the correlations between proprioceptive performance for the two anatomical structures, with performance on the right side strongly correlated but not on the left. This is consistent with the need for coordination between structures during chewing. When acuity at different points in the stimulus range was examined, the right side lips were better with small stimuli. Overall, results support enhanced use-specific proprioception.

Processing of proprioceptive and vestibular body signals and self-transcendence in Ashtanga yoga practitioners

In the rod and frame test (RFT), participants are asked to set a tilted visual linear marker (i.e., a rod), embedded in a square, to the subjective vertical, irrespective of the surrounding frame. People not influenced by the frame tilt are defined as field-independent, while people biased in their rod verticality perception are field-dependent. Performing RFT requires the integration of proprioceptive, vestibular and visual signals with the latter accounting for field-dependency. Studies indicate that motor experts in body-related, balance-improving disciplines tend to be field-independent, i.e., better at verticality perception, suggesting that proprioceptive and vestibular expertise acquired by such exercise may weaken the influence of irrelevant visual signals. What remains unknown is whether the effect of body-related expertise in weighting perceptual information might also be mediated by personality traits, in particular those indexing self-focusing abilities. To explore this issue, we tested field-dependency in a class of body experts, namely yoga practitioners and in non-expert participants. Moreover we explored any link between performance on RFT and self-transcendence (ST), a complex personality construct, which refers to tendency to experience spiritual feelings and ideas. As expected, yoga practitioners (i) were more accurate in assessing the rod's verticality on the RFT, and (ii) expressed significantly higher ST. Interestingly, the performance in these two tests was negatively correlated. More specifically, when asked to provide verticality judgments, highly self-transcendent yoga practitioners were significantly less influenced by a misleading visual context. Our results suggest that being highly self-transcendent may enable yoga practitioners to optimize verticality judgment tasks by relying more on internal (vestibular and proprioceptive) signals coming from their own body, rather than on exteroceptive, visual cues.

Effects of cervical muscle fatigue on the perception of the subjective vertical and horizontal

Introduction

Cervical functional capacity outcome measures that are simple and reliable are urgently needed in order permit accurate assessment/reassessment during treatments and rehabilitation. Induced neck muscle fatigue has been shown to alter functional capacities such as balance and kinaesthetic sense in the standing posture. The Rod and Frame Test has also shown promise as a method of assessing the effects of chronic neck pain and injury, but currently only in the sitting position. The objectives of this project were therefore 1) to validate the computerised rod and frame test in the standing posture, and 2) to measure the effects that different cervical muscle fatigue protocol would have on the assessment of the subjective visual vertical and horizontal.

Method

The validation of the standing computerised rod and frame test in the standing posture was obtained by comparing results (n = 74) between the sitting and standing positions with the Spearman’s correlation coefficient. In addition, agreement between the two methods was analysed with the Bland-Altman method.

Participants (n = 56) resisted with their neck muscles approximately 35% maximum isometric voluntary contraction force for 15 minutes on a purpose built apparatus in eight different directions. Wilcoxon signed rank tests analysed changes in horizontal and vertical rod and frame test between the neutral and all different directions of contraction. The changes of recorded unsigned vertical and horizontal errors for the combined frame condition in all situations of isometric contraction were analysed with two respective one-way repeated measures analysis of variance (ANOVA).

Discussion

The Spearman’s rho and Bland-Altman plots show that the Rod and Frame Test works equally well in sitting and standing positions.

After muscle contraction, there were significant increases in error in all participants for both horizontal and vertical rod and frame tests, except after flexion. These errors were predominantly present after fatigue of muscles in the coronal plane of contraction. Proprioception alone cannot explain the difference in the rod and frame results between different muscle groups. It is suggested that an evolutionary advantage of developing improved subjective verticality awareness in the same direction as the main visual field could explain these findings.

The Effects of Rotating the Self Out of the Body in the Full Virtual Body Ownership Illusion

It has been shown that it is possible to induce a strong illusion that a virtual body (VB) is one's own body. However, the relative influence of a first-person-perspective (1PP) view of the VB and spatial coincidence of the real body and VB remains unclear. We demonstrate a method that permits separation of these two factors. It provides a 1PP view of a VB, supporting visuomotor synchrony between real body and VB movements, but where the entire scene including the body is rotated 15° upwards through the axis connecting the eyes, so that the VB and real body are coincident only through this axis. In a within-subjects study that compared this 15° rotation with a 0° rotation condition, participants reported only slightly diminished levels of perceived ownership of the VB in the rotated condition and did not detect the rotation of the scene. These results indicate that strong spatial coincidence of the virtual and real bodies is not necessary for a full-body ownership illusion. The rotation method used, similar to the effects of vertical prisms, did not produce significant negative side-effects, thus providing a useful methodology for further investigations of body ownership.

Multisensory origin of the subjective first-person perspective: visual, tactile, and vestibular mechanisms

In three experiments we investigated the effects of visuo-tactile and visuo-vestibular conflict about the direction of gravity on three aspects of bodily self-consciousness: self-identification, self-location, and the experienced direction of the first-person perspective. Robotic visuo-tactile stimulation was administered to 78 participants in three experiments. Additionally, we presented participants with a virtual body as seen from an elevated and downward-directed perspective while they were lying supine and were therefore receiving vestibular and postural cues about an upward-directed perspective. Under these conditions, we studied the effects of different degrees of visuo-vestibular conflict, repeated measurements during illusion induction, and the relationship to a classical measure of visuo-vestibular integration. Extending earlier findings on experimentally induced changes in bodily self-consciousness, we show that self-identification does not depend on the experienced direction of the first-person perspective, whereas self-location does. Changes in bodily self-consciousness depend on visual gravitational signals. Individual differences in the experienced direction of first-person perspective correlated with individual differences in visuo-vestibular integration. Our data reveal important contributions of visuo-vestibular gravitational cues to bodily self-consciousness. In particular we show that the experienced direction of the first-person perspective depends on the integration of visual, vestibular, and tactile signals, as well as on individual differences in idiosyncratic visuo-vestibular strategies.

Gait adaptability training is affected by visual dependency

As part of a larger gait adaptability training study, we designed a program that presented combinations of visual flow and support-surface manipulations to investigate the response of healthy adults to walking on a treadmill in novel discordant sensorimotor conditions. A visual dependence score was determined for each subject, and this score was used to explore how visual dependency was linked to locomotor performance (1) during three training sessions and (2) in a new discordant environment presented at the conclusion of training. Performance measures included reaction time (RT), stride frequency (SF), and heart rate (HR), which respectively served as indicators of cognitive load, postural stability, and anxiety. We hypothesized that training would affect performance measures differently for highly visually dependent individuals than for their less visually dependent counterparts. A seemingly unrelated estimation analysis of RT, SF, and HR revealed a significant omnibus interaction of visual dependency by session (p < 0.001), suggesting that the magnitude of differences in these measures across training day 1 (TD1), training day 3 (TD3), and exposure to a novel test is dependent on subjects' levels of visual dependency. The RT result, in particular, suggested that highly visually dependent subjects successfully trained to one set of sensory discordant conditions but were unable to apply their adapted skills when introduced to a new sensory discordant environment. This finding augments rationale for developing customized gait training programs that are tailored to an individual. It highlights one factor--personal level of visual dependency--to consider when designing training conditions for a subject or patient. Finally, the link between visual dependency and locomotor performance may offer predictive insight regarding which subjects in a normal population will require more training when preparing for specific novel locomotor conditions.

Effects of martial arts on health status: a systematic review

OBJECTIVE

To systematically summarize the evidence for the effects of martial arts on health and fitness, to show the strengths of different types of martial arts, and to get a more complete picture of the impacts of martial arts on health, and also to provide a basis for future research on martial arts as an exercise prescription in exercise therapy.

METHOD

We searched for "martial arts""health" and "random" in eight databases (n= 5432). Randomized controlled trials and controlled clinical trials on the health effects of martial arts were included in the study.

RESULTS

The final analysis included 28 papers (one general martial arts, one kung fu, sixteen tai chi, six judo, three karate, and one taekwondo). Among the disciplines of martial arts, tai chi was the most well-studied, followed by judo, karate, and taekwondo. Research topics varied widely, and included health, injuries, competition, morals and psychology, and herbal medicine. Most found positive effects on health. Tai chi is no-contact, low-impact, soft body and mindfulness exercise, which has been widely adopted by elderly people and proven to be a beneficial health promotion exercise. Research on judo, karate, and taekwondo mainly focused on improvements to athletes' competitive abilities, rather than on health effects. We did not find any published randomized controlled trials or controlled clinical trials on aikido, kendo, sumo, kyudo, qi gong, or other disciplines.

DISCUSSION AND CONCLUSION

Since martial arts are widely practiced, their effects on physiology, morphology, immunology, and neurology should be further studied in order to help people to select the best discipline or style to accomplish their purposes. This necessitates categorizing and classifying the disciplines and styles according to their effects on different body systems and levels of contact, as well as standardizing evaluation criteria for martial arts. Martial arts as an exercise prescription can then move from an experience-based to an evidence-based treatment.

Organization of postural equilibrium in several planes in ballet dancers

This study analyzed the balance strategies of ballet dancers during postural equilibrium in three single leg balance conditions with and without vision and regard to age. Dancers participating formed two groups of 20 dancers each, one aged between 8 and 16 years (young group) and the other aged between 17 and 30 years (adult group). Ground reaction forces (GRFs) (mediolateral (ML), anteroposterior (AP) components, vertical (V)) were recorded. Results analysis enabled us to extract some spatiotemporal data for each component of the GRF (number of GRF oscillations, variability and impulses). Young dancers are characterized, compared to adult dancers, by an instability combined with an increase of oscillations number and a decrease variability mainly visible on the ML component. In the two groups, the absence of vision implies an increase of AP, ML and V impulsions and GRF variability. Balance with the gesturing limb to the rear increases the age and vision effect compared to balances with the limb forward or to the side. Young dancers are less efficient at controlling their balance than adult dancers. This observation may be related to the number of hours practicing dance, which differs between groups. The dancers have a visual dependence to control the postural balance.

Visual motion combined with base of support width reveals variable field dependency in healthy young adults

We previously reported responses to induced postural instability in young healthy individuals viewing visual motion with a narrow (25 degrees in both directions) and wide (90 degrees and 55 degrees in the horizontal and vertical directions) field of view (FOV) as they stood on different sized blocks. Visual motion was achieved using an immersive virtual environment that moved realistically with head motion (natural motion) and translated sinusoidally at 0.1 Hz in the fore-aft direction (augmented motion). We observed that a subset of the subjects (steppers) could not maintain continuous stance on the smallest block when the virtual environment was in motion. We completed a posteriori analyses on the postural responses of the steppers and non-steppers that may inform us about the mechanisms underlying these differences in stability. We found that when viewing augmented motion with a wide FOV, there was a greater effect on the head and whole body center of mass and ankle angle root mean square (RMS) values of the steppers than of the non-steppers. FFT analyses revealed greater power at the frequency of the visual stimulus in the steppers compared to the non-steppers. Whole body COM time lags relative to the augmented visual scene revealed that the time-delay between the scene and the COM was significantly increased in the steppers. The increased responsiveness to visual information suggests a greater visual field-dependency of the steppers and suggests that the thresholds for shifting from a reliance on visual information to somatosensory information can differ even within a healthy population.

[Visual dependence after recent stroke]

INTRODUCTION

After chronic stroke, inability to use pertinent somatosensory or vestibular information have been described. The aim of the study was to determine whether visual dependence occurred early after stroke before rehabilitation.

METHOD

Thirty patients with recent hemiplegia (16 right and 14 left hemispheric stroke) performed the rod and frame test (RFT). Patients were asked to adjust the rod to the vertical position under 3 conditions: basically, with a frame tilted 18 degrees to the right and then with the frame tilted to the left. Bias in each condition (mean, SD) was recorded and compared to adjustments of the rod by 23 controls. Motor control, sensibility, functional level (functional independence measure), age, neglect, and then balance by the postural assessment scale for stroke were assessed.

RESULTS

Fifty-six per cent (17/30) of patients but only 26% of controls were influenced by the tilt of the frame on the 2 sides (visual dependence). No correlation was found between visual dependence and the characteristics of the patients.

DISCUSSION

Many patients with recent hemiplegia seem to rely on visual input. The mechanisms of such visual dependence are discussed. Rehabilitation programs should take into account the possible impairment of sensory organisation and should include exercises to be performed under visual disturbances.