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PubMed2005

Tactile directional sensitivity and postural control.

People are good at telling the direction of a moving tactile stimulus and this capacity provides a sensitive clinical test of somatosensory disturbances. Tactile directional sensitivity depends on two different kinds of somatosensory information, i.e. spatiotemporal information and information about friction-induced changes in skin stretch. The objective of this study was to compare the relative contribution to postural control of these two types of information for both glabrous and hairy skin. Postural sway amplitudes and sway paths were recorded, with or without access to tactile and/or visual stabilizing stimuli. Subjects were standing on two types of surface, either solid metal or 50 mm foam plastic. Two types of stimulus were used to generate sway-related tactile information. One was a thin air-stream that was used to assess the contribution by spatiotemporal information, and the second was a narrow steel rod that was glued to the skin to assess the contribution by skin-stretch information. The stimuli were applied to the hairy skin of the forearm and to the glabrous skin of the fingertip. In addition, we studied the ability to tell the direction of movement of an air-stream stimulus on glabrous and hairy skin. The air-stream caused significant sway reductions when applied to glabrous, but not hairy skin. The weak effect on hairy skin reflected the perceptually poor directional sensitivity for the air-stream stimulus in this cutaneous area. In contrast, the glued rod reduced sway when applied to both glabrous and hairy skin reflecting the tactile afferents' high sensitivity to skin stretch in these areas. Both types of tactile stimulus reduced sway amplitudes more than sway paths for both hairy and glabrous skin. The visual cue, on the other hand, tended to reduce sway paths more than amplitudes. The two types of tactile receptive surface seem to influence postural control in the same manner, despite anatomical and physiological differences. The results invite speculation that patients with poor directional sensitivity might have reduced postural stability compared with healthy individuals.

Adult↗
PubMed2006

Effects of distance and gaze position on postural stability in young and old subjects.

Visual stabilization of posture is known to improve when the distance to target fixation decreases; this is attributed to increased angular size of retinal slip induced by body sway. At near distance, however, the eyes converge and efferent or afferent oculomotor signals could also be involved in posture stabilization. The goal of this study is to test whether the distance effect exists for both young and elderly and to test the role of vergence itself and of gaze position. Eighteen young (25.3 years) and 17 elderly (61.6 years) subjects were asked to fixate a target in quiet stance presented either at close (40 cm) or at far distance (200 cm); the vergence angle was 9 degrees and 2 degrees , respectively. For each distance, three gaze positions were studied straight-ahead (0 degrees ), 15 degrees up or down. We found a decrease in the surface of center of pressure (CoP), of standard deviation of antero-posterior and lateral body sway and of speed variance at near distance that occurs for both young and elderly. At far distance, the surface of CoP is smaller for 15 degrees up or down gaze in comparison with straight-ahead position, but at near distance there is no such gaze position effect. In an additional experiment, subjects fixated a target at far distance (200 cm) but prisms were used to cause the eyes to converge by an amount similar to that required for 40 cm viewing distance. The use of prisms decreased surface of CoP to values similar to those for natural near viewing distance. The effect of gaze position and of convergence (experiment with prisms) leads us to suggest that in addition to retinal slip, the ocular motor signals and perhaps related neck muscle activity are involved in postural stabilization. Finally, the elderly presented higher speed variance of CoP than the young subjects even though the surface itself was similar to adult values. We suggest that increment of speed variance is the first sign of senescence in postural control.

Adaptation, Physiological↗
PubMed2006

Threshold control of arm posture and movement adaptation to load.

We addressed the fundamental questions of which variables underlie the control of arm movement and how they are stored in motor memory, reproduced and modified in the process of adaptation to changing load conditions. Such variables are defined differently in two major theories of motor control (internal models and threshold control). To resolve the controversy, these theories were tested (experiment 1) based on their ability to explain why active movement away from a stable posture is not opposed by stabilizing mechanisms (the posture-movement problem). The internal model theory suggests that the system counteracts the opposing forces by increasing the muscle activity in proportion to the distance from the initial posture (position-dependent EMG control). In contrast, threshold control fully excludes these opposing forces by shifting muscle activation thresholds and thus resetting the stabilizing mechanisms to a new posture. Subjects were sitting, holding the vertical handle of a double-joint manipulandum with their right hand and were facing a computer screen on which the handle and target to be reached were displayed. In response to an auditory signal, subjects quickly moved the handle from an initial position to one of two (frontal and sagittal) targets. No load was applied during the movement but in separate trials, a brief perturbation was applied to the handle by torque motors controlling the manipulandum. Perturbations were applied prior to or 3 s after movement offset, in the latter case in one of eight directions. The EMG activity of the majority of the seven recorded muscles was at zero level before movement onset and returned to zero level after movement offset. Those muscles that remained active before or after the movement could be made silent whereas previously silent muscles could be activated after a small passive displacement (several millimeters) elicited by perturbations in appropriate directions. Results showed that the activation thresholds of motoneurons of arm muscles were reset from the initial to a final position and that EMG activity was not position-dependent. These results were inconsistent with the internal model theory but confirmed the threshold control theory. Then the ability of threshold control theory to explain rapid movement adaptation to a position-dependent load was investigated (experiment 2 and 3). Subjects produced fast movement to the frontal target with and without a position-dependent load applied to the handle. Trials were organized in blocks alternating between the load and no-load condition (20 blocks in total, with randomly chosen number of five to ten trials in each). Subjects were instructed "do not correct" in experiment 2 and "correct" movement errors during the trial in experiment 3. Five threshold arm configurations underlying the movement production and adaptation were identified. When instructed "do not correct", movement precision was fully restored on average after two trials. No significant improvement was observed as the experiment progressed despite the fact that the same load condition was repeated after one block of trials. Thus, in each block, the adaptation was made anew, implying that subjects relied on short-term memory and could not recall the threshold arm configurations they specified to accurately reach the same target in the same load condition in previous blocks. When instructed to "correct" within each trial, precision was restored faster, on average after one trial. Major aspects of the production and adaptation of arm movement (including the kinematics, movement errors, instruction-dependent behavior, and absence of position-related EMG activity) are explained in terms of threshold control.

Adaptation, Physiological↗
PubMed2006

Representation of dynamic events triggered by motion lines and static human postures.

Artists and cartoonists are able to dexterously depict a running person on paper with the aid of 'motion lines'. We scientifically examined whether the cognitive system can exploit motion lines in constructing memory representations of the location of a running person depicted in a still image. A target depicting a standing or a running person with or without motion lines was presented to participants for 500 ms. Observers were required to reproduce the location of the target 1 s after its disappearance. Data from depicted leftward and rightward moving persons were collapsed. Memory displacement of the target was shown to be largest in the presence of motion lines and a posture indicating an identical direction of movement. By assessing the absolute localization error, we showed that there was no localization advantage toward a target with a symmetrical (standing) posture over one with an asymmetrical (running) posture. Our findings indicate synergetic interaction between the mechanisms responsible for processing of motion lines and human postures in the representation of dynamic events.

Analysis of Variance↗
PubMed2006

Returning home: location memory versus posture memory in object manipulation.

Previous studies of object manipulation have suggested that when participants return an object to the place from which they just carried it, they tend to grasp the object for the target-back-to-home trips close to where they just grasped it for the home-to-target trips [Exp Brain Res 157(4):486-495, 2004; Psychon Bull Rev, 2006]. What was unclear from these previous studies was whether participants recalled postures or locations. According to the posture hypothesis, they remembered what body positions they adopted when they last held the object. According to the location hypothesis, they remembered where they held the object and then took hold of it there or nearby again. To distinguish between these possibilities, we had participants mount or dismount a platform after home-to-target moves and before target-back-to-home moves. In the control condition, they did not change their vertical position relative to the shelf containing the home and target platforms (they merely stepped sideways). We found that participants grasped the object at nearly the same place along its length as they had before, even if this meant adopting very different postures than before. This outcome is consistent with the location-recall account and is inconsistent with the posture-recall account. The implications for motor planning are discussed.

Adult↗
PubMed2006

Cognitive load affects postural control in children.

Inferring relations between cognitive processes and postural control is a relatively topical challenge in developmental neurology. This study investigated the effect of a concurrent cognitive task on postural control in a sample of 50 nine-year-old children. Each subject completed two balance trials of 60 s, one with a concurrent cognitive task (cognitive load) and another with no cognitive load. The concurrent cognitive task consisted of mentally counting backwards in steps of 2. Twelve posturographic parameters (PPs) were extracted from the centre of pressure (CoP) trajectory obtained through a load cell force plate. Analysis of variance revealed significant differences in the majority of the extracted PPs. CoP was found to travel faster, farther, and with substantially different features demonstrating an overall broadening of the spectrum in the frequency domain. Nonlinear stability factors revealed significant differences when exposed to a concurrent cognitive task, showing an increase of instability in the intervention rate of the postural control system. By grouping children through selected items from Teachers Ratings and PANESS assessment, specific significant differences were also found both in time and frequency domain PPs, thus confirming the hypothesis of an interaction between cognitive processes (and their development), and postural control.

Attention↗
PubMed1998

The influence of vision on the automatic postural muscle responses of newly standing and newly walking infants.

In adults, visual inputs do not appear to contribute significantly to automatic postural muscle responses (90-100 ms latency) activated by transient support surface displacements causing threats to standing balance, but are activated through slow pathways with latencies of more than 200 ms. However, it has been shown that the postural sway behavior of early walking infants is strongly influenced by visual flow cues that falsely signal self-movement. To determine whether there also are significant contributions of vision to automatic postural muscle responses in this age group, two groups of infants were tested on a moveable platform; pre-walkers (n=6) and early walkers (n=6). Pre-walkers did not show any measurable effect of visual condition (vision vs no vision) on muscle response characteristics. However, the integrated gastrocnemius activity of early walkers increased significantly in vision versus no vision conditions (P<0.05). These results show that visual cues contribute to, or modulate, the automatic postural responses in children who are in the developmental transition to independent walking.

Cues↗
PubMed1998

High postural constraints affect the organization of reaching and grasping movements.

In the vast majority of prehension experiments, subjects are requested to grasp a static object and to transport it with respect to the body. There are grasping tasks, however, that have different grasping requirements. For example, in rock climbing, the goal is to grasp a hold to transport the body about the grasped object. Unlike simple reaching and grasping movements, the successful hand grip is not the goal of the task per se, and it is the postural stability that primarily determines the success or failure of the task. In the present experiment, we wanted to examine the influence of such postural constraints on the organization of reaching movements. Four expert climbers participated in the study. A climbing simulator, equipped with strain gauges, measured the vertical forces applied by the hands. The subjects performed grasping movements (one-reach and two-reach conditions) towards holds of various depths (easy and difficult holds) in two different postures (standing and climbing conditions). The results showed that the duration of the right-hand transport phase was similar whatever the condition. Unexpectedly, in the climbing condition, the duration of the left-hand transport phase was shorter when the subjects grasped a difficult than when they grasped an easy hold. This result suggests that, in extreme cases such as rock climbing, the postural constraints may prevail over accuracy constraints, since increasing accuracy requirements did not yield an increased duration of the transport phase.

Adult↗
PubMed1999

Anticipatory postural adjustments are associated with single vertical jump and their timing is predictive of jump amplitude.

This study was carried out to determine the existence and the specificity of anticipatory postural adjustments (APA) associated with vertical jump. Single vertical jump is an upward-oriented movement with identical initial and final postures. A consistent backward shift of the center of pressure (CP) clearly demonstrated the existence of APA. This shift mainly resulted from a soleus (SO) deactivation and tibialis anterior (TA) activation. As in gait initiation, the main role of APA associated with vertical jump is to create the necessary disequilibrium to initiate the movement. A comparison of CP and CG (center of gravity) forward shifts between single jump and tip-toe rising allowed us to propose that forward disequilibrium ends when a critical CP position is reached. As in gait initiation, the duration of jump's APA was several hundreds of milliseconds. This showed that when the role of the APA is to create the initial disequilibrium, their duration is greater than when their role is to compensate for the forthcoming postural disturbance due to the movement. Since the goal of the voluntary movement was to jump at a given height, one expected that this parameter could be programmed. APA's timing depended on the amplitude of the vertical jump: the time of onset of SO deactivation and TA activation and that of backward CP shift were dependent on the peak amplitude of the jump. Nevertheless, there was no relationship between the backward CP shift amplitude and the vertical impulse. Thus, it appears that the amplitude of the jump is not fully programmed but must be adjusted after the onset of the movement, i.e., there is a sequential programming of forward and upward movement. It is also of interest to stress that the SO-TA synergy, which is shown here to be at the basis of the APA associated with single vertical jump, has been also found in many forward-oriented movements. Thus, the present data reinforce the idea that SO-TA synergy is part of a functional synergy used by the central nervous system to simplify the postural motor command.

Adult↗
PubMed2004

In vivo-application of anti-proctolin-antiserum affects antennal flight posture in crickets.

Tethered crickets flying in a wind tunnel adopt a characteristic posture in which the antennae are pointed in parallel and anteriorly into the headwind. Although the firing rates of antennal motoneurons are largely reduced after the start of a flight sequence, the associated postural changes of the antennae are small. It is hypothesised that proctolin, which is present in antennal motoneurons, stabilises the prolonged antennal forward position. To test this hypothesis, proctolin was blocked by anti-proctolin antiserum injections into one antennal base in otherwise intact behaving crickets. The antiserum quickly led to prolonged backward deflections of the treated antennae in 65% of cases. It then took more than one hour for the deflected posture to revert to a normal flight posture. It appears that proctolin is necessary to produce muscle tension large enough to hold the antennae in a forward position and to compensate for the headwind drag. Proctolin, therefore, acts to generate force with reduced electrical activity of motoneurons and muscles.

Action Potentials↗
PubMed2005

Effects of neck and circumoesophageal connective lesions on posture and locomotion in the cockroach.

Few studies in arthropods have documented to what extent local control centers in the thorax can support locomotion in absence of inputs from head ganglia. Posture, walking, and leg motor activity was examined in cockroaches with lesions of neck or circumoesophageal connectives. Early in recovery, cockroaches with neck lesions had hyper-extended postures and did not walk. After recovery, posture was less hyper-extended and animals initiated slow leg movements for multiple cycles. Neck lesioned individuals showed an increase in walking after injection of either octopamine or pilocarpine. The phase of leg movement between segments was reduced in neck lesioned cockroaches from that seen in intact animals, while phases in the same segment remained constant. Neither octopamine nor pilocarpine initiated changes in coordination between segments in neck lesioned individuals. Animals with lesions of the circumoesophageal connectives had postures similar to intact individuals but walked in a tripod gait for extended periods of time. Changes in activity of slow tibial extensor and coxal depressor motor neurons and concomitant changes in leg joint angles were present after the lesions. This suggests that thoracic circuits are sufficient to produce leg movements but coordinated walking with normal motor patterns requires descending input from head ganglia.

Action Potentials↗
PubMed2004

Functional, postural and perceived balance for predicting the work ability of firefighters.

OBJECTIVE: The importance of balance abilities for firefighting and rescue work has already been recognized, but there are no valid balance tests available in the test batteries for the physical work capacity of firefighters. Moreover, few studies have examined the associations between balance and work ability in general. Valid work-related balance tests are needed for the purpose of screening in occupational health care and in rehabilitation for assessing the effects of balance training. This study aimed to investigate the predictive value of functional, postural and perceived balance in respect to work ability among firefighters at baseline and after a 3-year follow-up. METHODS: The subjects were 135 male firefighters aged 33-56 years. The outcome variables were the work ability index and perceived physical work ability (PWA), determined by questionnaire in 1996 and 1999. The predictors assessed in 1996 were postural balance (tested with a force platform), functional balance (measured during walking on a wooden plank), and perceived balance abilities, enquired about through a questionnaire. RESULTS: Most of the balance test results and the perceived balance ability were associated with the perceived PWA at baseline. The final logistic regression models showed that the best predictors of decreased work ability among firefighters after 3 years were poor-to-moderate perceived balance [odds ratios (ORs) 2.4, 95% confidence interval (CI) 0.9-6.6]; more than one error in the functional balance test (OR 3.6, 95% CI 1.0-12.7); and a high mean amplitude of postural sway with the eyes closed (OR 2.7, 95% CI 0.9-6.1). CONCLUSIONS: The results support the work-related and predictive validity, in terms of perceived work ability, perceived balance, errors in the functional balance test and amplitude of postural sway with the eyes closed, of measuring balance among firefighters.

Adult↗
PubMed2005

Long-term exposure to solvents impairs vigilance and postural control in serigraphy workers.

OBJECTIVES: To investigate the effects of solvent exposure (mainly aromatic hydrocarbons) on central regulation of vigilance and postural control, particularly in occasional difficult situations that provide sensorial conflicts. METHODS: Twenty-two workers occupationally exposed to solvents for an average of approximately 6 years and 21 controls were compared by the use of a questionnaire on their state of vigilance and quality of sleep and on performance measurements of postural control under six different sensorimotor conditions. Their current median exposure levels to aromatic hydrocarbons was 80.1 mg/m(3). RESULTS: Exposed workers reported reduced alertness but not disturbance of sleep quality compared with controls. Moreover, they had the worst postural performance in all sensory conditions and demonstrated a reduced ability to resolve sensory conflict situations. The precision of stance was clearly affected by solvent exposure in contrast with energy consumption required to regulate proper balance control. CONCLUSIONS: The depressive effect of aromatic hydrocarbon exposure on cortical and subcortical structures controlling vigilance and postural stability could lead to increased risk of occupational accident, especially due to falls. The detection of central neurotoxic effects by posturographic and vigilance tests could be useful in preventive strategies.

Adult↗
PubMed1998

The effects of an ergonomic-educational course. Postural load, perceived physical exertion, and biomechanical errors in nursing.

OBJECTIVES: To evaluate the results of an ergonomic-educational course for nurses we assessed the number and percentage of harmful postures and of ergonomic and biomechanical errors made before and after the course. We also studied the perceived physical exertion. MEANS AND METHODS: In all, 12 nurses who had participated in the course (trainees) and 12 who had not (controls) were recorded on video while performing standardized nursing tasks. The wards from which the two groups of nurses came were comparable, as were the patient populations. The nurses were also comparable in some personal characteristics. The tasks they performed included washing, lifting, and repositioning a patient as well as certain tasks other than patient handling. Video recordings were made once before (1-2 weeks) and twice after the course (after 3 months and after 15 months). The harmful postures, the errors made, and the ratings of perceived exertion were measured by means of the Ovako Working-posture Analysis System (OWAS), a checklist, and Borg scores, respectively. RESULTS: When the first and last measurements of all the above tasks taken as a whole were analyzed the trainees showed a significant improvement in the number and percentage of harmful postures and errors, whereas the controls did not. The same could be concluded for lifting alone. After the course the new work routine did not appear to have caused any extra perceived physical exertion. CONCLUSION: It can be concluded that the course was successful, although it should be carefully investigated as to whether nurses remain capable of working safely in daily practice. The work pressure that nurses experience during their normal duties could prevent them from working safely during everyday work.

Adult↗
PubMed1999

Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units.

OBJECTIVE: A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG. Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. METHODS: Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions. After the first and again after the second hour there was a break of 15 min. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. RESULTS: The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. On average, the distance between C7 and the left and right acromion decreased within each working an hour. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right). CONCLUSION: The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.

Adult↗
PubMed2002

Isometric axial rotation of the human trunk from pre-rotated postures.

The purpose of this investigation was to study the torque and electromyogram (EMG) in axial rotation from pre-rotated postures. A group of 50 young adults (27 men and 23 women) volunteered for the study. These prepared subjects carried out axial rotation with pre-rotated postures in the direction of pre-rotation and away from it. Torque and EMG were recorded bilaterally from latissimus dorsi, erector spinae at L(3) and T(10) levels, pectoralis, rectus abdominis, external and internal oblique. In 15 degrees pre-rotated posture the axial rotation in the direction of pre-rotation reduced the torque by between 11% and 17% and away from it increased the torque by 12% to 16%. In 30 degrees pre-rotated posture the decrement in torque in the direction of pre-rotation was 24%-33%, and in the opposite direction the gain was between 21% and 32%. Even with decreased torque with rotation in the pre-rotation direction the EMG increased up to 123%. The EMG magnitude and slopes of EMG in these activities demonstrated significant increases while in the opposite direction slight decreases were observed. The EMG of each muscle was significantly different from all other muscles ( P<0.001). A significant ( P<0.01) but low correlation between EMG and torque was obtained. Significant linear regressions between torque and EMG of different muscles were obtained ( P<0.01; r=up to 0.70).

Adolescent↗
PubMed2003

The serum angiotensin-converting enzyme and angiotensin II response to altered posture and acute exercise, and the influence of ACE genotype.

The deletion (D) rather than insertion (I) allele of the angiotensin-converting enzyme (ACE) gene is associated with greater ACE activity. We examined: (1) the influence of posture change (recumbent to seated) and acute exercise on serum ACE and angiotensin II (Ang II) activity; (2) the relationship between ACE and Ang II levels; and (3) the influence of ACE genotype on changes in ACE and Ang II levels with posture and exercise. Recreationally active young male Caucasians (10 each of II, ID and DD genotypes) rested for 35 min supine then 15 min upright, took 20 min bicycle ergometric exercise at 70% maximum oxygen uptake, then rested for 40 min. Samples were taken throughout for ACE activity and Ang II levels. Supine ACE levels were dependent upon ACE genotype [24.8 (5.7), 26.9 (4.5), 45.5 (6.4) nmol His-Leu ml(-1) min(-1); II, ID, DD, respectively; P<0.00005] and thereafter. ACE activity rose with assumption of a seated posture [from 32.4 (10.9) nmol His-Leu ml(-1) min(-1) to 35.0 (11.5) nmol His-Leu ml(-1) min(-1), P<0.00001], the absolute rise being independent of genotype [3.22 (1.92), 1.6 (1.6), 2.4 (2.3) nmol His-Leu ml(-1) min(-1); II, ID, DD; P=0.22], unlike percentage change [12.8 (6.8), 5.6 (5.5), 5.3 (5.0)%; II, ID, DD; P<0.01, and P=0.004 for II vs presence of the D allele]. A further genotype-independent rise occurred with exercise [+2.9 (3.7) units, P<0.0003]. An associated rise in Ang II levels [30.3 (15.9), or 2587.9 (489.76)%, P<0.00001] was independent of ACE genotype or activity. Upright posture increases ACE activity, and this may be influenced by ACE genotype. ACE activity and Ang II levels rise independently with exercise in a non-genotype-dependent fashion.

Adaptation, Physiological↗
PubMed2004

Postural control in athletes participating in an ironman triathlon.

We studied the degree of dependence on vision of static postural control among ten male adult ironmen and ten healthy subjects (firemen, control group) who took part in regular physical activity, and the perturbations of equilibrium after prolonged exercise in ironmen. Static postural stability was measured during standing on a single-force platform alternating between eyes open and eyes closed. First, body sway was analysed on a force plate in both groups, and the athletes then took part in an ironman triathlon. The measurement was repeated after the race. The sway in both directions was subjected to spectral analysis. The frequency spectrum of the platform oscillations was calculated by fast Fourier transformation in the intervals 0-0.3, 0.3-1 and 1-3 Hz. The sway path in both directions and the total path were significantly lower in the ironmen than in the control group without vision, and the absence of visual control caused a significant increase in sway in both directions in the control group, but not in the ironmen. The frequency analysis revealed a higher level of stability in the medio-lateral direction with closed eyes. The endurance race caused increases in both the total sway path only with closed eyes, and these changes were significant at higher frequency bands. These results indicate that ironmen are more stable and less dependent on vision for postural control than the control subjects, and the prolonged stimulation of the proprioceptive, vestibular and visual inputs in the endurance race causes a significant disturbance in postural control.

Adult↗