Relation of arterial stiffness with postural control in older people.

PURPOSE: Arterial stiffness generates vascular alterations that may cause balance disorders and falls. This study aimed to investigate the possible link between arterial stiffness and postural control under different sensorial conditions in patients over 65 years. METHODS: Carotid-femoral pulse wave velocity (PWV) was measured in 47 participants aged over 65 years to evaluate their arterial stiffness (high PWV). Twenty-seven participants (mean age = 70.52 ± 4.02 years, 22 females) had a normal PWV (< 10 m s-1) and 20 participants (mean age = 75.93 ± 6.11 years; 15 females) had a high PWV (≥ 10 m s-1). Postural control was evaluated using a force platform in four postural conditions: eyes open (EO) 1, eyes closed (EC), eyes open with a dual task (DT) and eyes open again (EO2). Using sway path traveled and surface covered by the center of foot pressure, we calculate the length function of surface (LFS). This ratio provides information about the precision (surface) of postural control and the effort made (length) by the subjects. RESULTS: After an age-adjustment, LFS was lower in EO than in EC and DT in both groups (p ≤ 0.001). LFS was higher in participants with high PWV both in eyes open and eyes closed conditions (p < 0.05). LFS increased when PWV increased in EO (p < 0.01) and EC conditions (p < 0.001) but not when a dual task was performed. CONCLUSION: Difficulties in maintaining equilibrium under a dual-task condition are more pronounced in people with increased arterial stiffness. These data suggest that understanding of the influence of the arterial stiffness level on specific balance control parameters could contribute to propose better balance-oriented rehabilitation programs in older adults in an attempt to prevent fall.

The trunk's contribution to postural control under challenging balance conditions.

BACKGROUND: The double inverted pendulum model is imprecise when applied to studies of postural control. Although multijoint analyses have improved our understanding of how balance is maintained, the exact role of the trunk remains unclear. RESEARCH QUESTIONS: What is the trunk's contribution in postural control with respect to the other joints and how do trunk muscles control trunk kinematics? METHODS: Thirty-six healthy athletes (handball, karate, long jump) performed a highly challenging balance task while the ground support was dynamically tilted in the sagittal plane. The center of force (CoF) as well as lower limb joint angles and the trunk-pelvis angle were respectively measured with a force platform and inertial measurement units. The amplitude, sway path and standard deviation of the CoF and the joint angles were then calculated. Electromyography was used to record the activity of the rectus abdominis, external obliquus, and erector spinae muscles. Multiple linear regressions were computed to determine the joints' and muscles' contributions (ß-coefficients) in predicting CoF variables and trunk kinematics, respectively. RESULTS: The linear combination of joint kinematic variables accounted for between 33 % and 75 % of the variance in the CoF. The ankle had the highestß and was a significant predictor of all CoF variables. The trunk yielded the second highest ß-coefficient and was a significant predictor of the CoF sway path. Electromyography variables accounted for no more than 35 % of the variance in the trunk kinematics, and erector spinae activity was the only significant predictor. SIGNIFICANCE: The trunk appears to be the second most important element during this specific postural task, in the magnitude of body sway in particular. But neuromuscular control of these trunk processes is difficult to characterize with surface electromyography only. The trunk should be taken into account when seeking to improve overall postural control (e.g. during training, rehabilitation).

Comparison of high-frequency intensive balneotherapy with low-frequency balneotherapy combined with land-based exercise on postural control in symptomatic knee osteoarthritis: a randomized clinical trial.

Knee osteoarthritis (KOA) can generate postural control impairments which can increase fall risk. Land-based exercise (LBE) and balneotherapy are two modalities currently prescribed, but the impact of the latter on balance control has not been studied. This study aimed to compare two programs of balneotherapy with or without LBE to improve postural control, looking at frequency and duration of treatment. A total of 236 KOA patients (mean age = 64 years) were included in this prospective and randomized study: 122 patients went through 3 weeks of standardized continuous balneotherapy (high frequency/short duration) program (Gr1) and 114 went through 3 weeks of discontinuous (low frequency) balneotherapy program followed by 3 weeks of LBE (Gr2). The total number of treatment sessions was the same for both groups. Posturography was carried out before balneotherapy (W0) and at 3 (W3), 6 (W6), and 12 (W12) weeks after the beginning of treatment. Postural control increased in Gr1 from W0 to W3 and from W0 to W12 and in Gr2 from W0 to W6 and from W3 to W6. The improvement was greater in Gr1 from W0 to W3 and from W6 to W12 and in Gr2 from W3 to W6. High-frequency intensive balneotherapy improved posture control at 3 weeks, while low-frequency balneotherapy did not. This improvement persisted over a 12-week assessment period at the same level. LBE generated an improvement that did not persist over time. Sustained improvement of postural control requires high-frequency repetition of consecutive balneotherapy sessions.

Influence of meteorological elements on balance control and pain in patients with symptomatic knee osteoarthritis.

This study aimed to determine if pain and balance control are related to meteorological modifications in patients with knee osteoarthritis (OA). One hundred and thirteen patients with knee OA (mean age = 65 ± 9 years old, 78 women) participated in this study. Static posturography was performed, sway area covered and sway path traveled by the center of foot pressure being recorded under six standing postural conditions that combine three visual situations (eyes open, eyes closed, vision altered) with two platform situations (firm and foam supports). Knee pain score was assessed using a visual analog scale. Balance control and pain measurements recorded in the morning were correlated with the meteorological data. Morning and daily values for temperature, precipitation, sunshine, height of rain in 1 h, wind speed, humidity, and atmospheric pressure were obtained from the nearest data collecting weather station. The relationship between postural control, pain, and weather variations were assessed for each patient on a given day with multiple linear regressions. A decrease of postural stability was observed when atmospheric pressure and maximum humidity decreased in the morning (p < 0.05) and when atmospheric pressure decreased within a day (p < 0.05). Patient's knee pain was more enhanced when it is warmer in the morning (p < 0.05) and when it is wetter and warmer within a day (p < 0.05). The relationship between weather, pain, and postural control can help patients and health professionals to better manage daily activities.

Prediction of Balance Compensation After Vestibular Schwannoma Surgery.

Background Balance compensation after vestibular schwannoma (VS) surgery is under the influence of specific preoperative patient and tumor characteristics. Objective To prospectively identify potential prognostic factors for balance recovery, we compared the respective influence of these preoperative characteristics on balance compensation after VS surgery. Methods In 50 patients scheduled for VS surgical ablation, we measured postural control before surgery (BS), 8 (AS8) days after, and 90 (AS90) days after surgery. Based on factors found previously in the literature, we evaluated age, body mass index and preoperative physical activity (PA), tumor grade, vestibular status, and preference for visual cues to control balance as potential prognostic factors using stepwise multiple regression models. Results An asymmetric vestibular function was the sole significant explanatory factor for impaired balance performance BS, whereas the preoperative PA alone significantly contributed to higher performance at AS8. An evaluation of patients' balance recovery over time showed that PA and vestibular status were the 2 significant predictive factors for short-term postural compensation (BS to AS8), whereas none of these preoperative factors was significantly predictive for medium-term postoperative postural recovery (AS8 to AS90). Conclusions We identified specific preoperative patient and vestibular function characteristics that may predict postoperative balance recovery after VS surgery. Better preoperative characterization of these factors in each patient could inform more personalized presurgical and postsurgical management, leading to a better, more rapid balance recovery, earlier return to normal daily activities and work, improved quality of life, and reduced medical and societal costs.

Vertigo in downhill mountain biking and road cycling.

Vertigo has been described after the practice of mountain bike. This study aimed to investigate the prevalence of vertigo following competitions or training sessions of downhill mountain biking (DMB) or road cycling (RC). One hundred and two DMB riders, 79 road cyclists and 73 control participants filled in a survey intended to evaluate the prevalence of vertigo in daily living activities and following competitions or training sessions. Vertigo causal factors (crashes, head trauma, fatigue, characteristics of the path/road ridden) were recorded. DMB riders and road cyclists did not report more vertigo during daily living activities than controls. But DMB riders older than 30 had more risk to report vertigo than age-matched road cyclists (OR: 5.06, 95% CI: 1.23-20.62). Road cyclists aged between 20 and 29 were 2.59-fold (95% CI: 1.06-6.27) more likely to report vertigo than controls. After competitions and training sessions, DMB riders were 2.33-fold (95% CI: 1.22-4.41) more likely to report vertigo than road cyclists. Vertigo causal factors were crash with head trauma in DMB riders and fatigue in road cyclists. Vertigo during daily living activities may be of concern for cyclists, particularly older DMB riders. The accumulation of impacts (crashes, vibrations) during the career of a DMB rider may generate micro-traumatisms of the central nervous system and/or peripheral vestibular structures, particularly the otolith organs. In RC, the pathophysiological mechanisms generating vertigo might be effort-related disturbance of homeostasis. To avoid injuries, DMB riders should be aware that vertigo may occur at the end of training sessions or competitions.

Diurnal variation on balance control in patients with symptomatic knee osteoarthritis.

OBJECTIVE: Increasing evidence supports balance control impairment in older adult patients with knee osteoarthritis (OA). However, there is limited data on diurnal variation of balance control in these patients. This study aimed to investigate postural stability in older adult patients with symptomatic knee OA during different periods in a daytime. METHODS: Two-hundred and forty-one patients with OA knee (median age=65 ± 12 years; 82 males) were enrolled in this study. Static posturography was performed under four standing conditions: eyes open and eyes closed, without and with foam support. To assess diurnal postural variations, testing sessions were defined as follows: 8-10 am, 10-12 am, 1 pm-3 pm, 3 pm-5 pm. Influence of sex, age, height, weight, and body mass index on postural stability was evaluated. Knee pain was also assessed in these four testing sessions. RESULTS: Postural control was in particular less efficient in the late morning than in the early afternoon (p<0.05). Diurnal variation of balance control was more noticeable in older, heavier, and male patients (p<0.05). Patients' knee pain was more pronounced in the morning than in the afternoon (p<0.001). CONCLUSION: Balance stability of patients with OA knee was different during a daytime. Altered postural performance in the morning could be explained by joint pain. This diurnal variation should be taken into account in the daily management of knee OA.

Does calculating impair postural stabilization allowed by visual cues?

In many daily situations, balance control is associated with a cognitive activity such as reading or a simple calculation. The objective of this study was to investigate the relationship between these two specific human activities, especially the influence of visual cues and support surface stability on body sway during a calculation task. A Sensory Organization Test, which can disrupt or suppress sensory inputs, was performed on 71 healthy young adults. The evaluations were performed both with and without mental arithmetic tasks which consisted of backward counting by three or thirteen. Our results showed that the addition of a calculation task induced an increase in body sway only when visual cues were available. They also showed the same instability effect of the support surface on the amount of body sway no matter what the associated cognitive task was. Moreover, no difference in body sway was observed between the two calculation tasks no matter what the visual context and/or the stability of the support surface were. We suggest that focusing on fulfilling the requirements of the mental calculation challenge may be responsible for the increase in body sway. This increase may be related to the use of oculomotor activity as unintentional attempts to increase arousal by self-generated body movement. Thus, this activity facilitates information processing rather than minimizing unbalance by a visual anchor point.

"Postural first" principle when balance is challenged in elderly people.

Human cognitive processing limits can lead to difficulties in performing two tasks simultaneously. This study aimed to evaluate the effect of cognitive load on both simple and complex postural tasks. Postural control was evaluated in 128 noninstitutionalized elderly people (mean age = 73.6 ± 5.6 years) using a force platform on a firm support in control condition (CC) and mental counting condition (MCC) with eyes open (EO) and eyes closed (EC). Then, the same tests were performed on a foam support. Sway path traveled and area covered by the center of foot pressure were recorded, low values indicating efficient balance. On firm support, sway path was higher in MCC than in CC both in EO and EC conditions (p < 0.001). On foam support, sway path was higher in CC than in MCC in EC condition (p < 0.001), area being higher in CC than in MCC both in EO (p < 0.05) and EC (p < 0.001) conditions. The results indicate that cognitive load alters balance control in a simple postural task (i.e. on firm support), which is highlighted by an increase of energetic expenditure (i.e. increase of the sway path covered) to balance. Awareness may not be increased and the attentional demand may be shared between balance and mental task. Conversely, cognitive load does not perturb the realization of a new complex postural task. This result showed that postural control is prioritized ("postural first" principle) when seriously challenged.

Clinical interest of postural and vestibulo-ocular reflex changes induced by cervical muscles and skull vibration in compensated unilateral vestibular lesion patients.

Skull vibration induces nystagmus in unilateral vestibular lesion (UVL) patients. Vibration of skull, posterior cervical muscles or inferior limb muscles alters posture in recent UVL patients. This study aimed to investigate the postural effect of vibration in chronic compensated UVL patients. Vibration was applied successively to vertex, each mastoid, each side of posterior cervical muscles and of triceps surae in 12 UVL patients and 9 healthy subjects. Eye movements were recorded with videonystagmography. Postural control was evaluated in eyes open (EO) and eyes closed (EC) conditions. Sway area, sway path, anteroposterior and medio-lateral sways were recorded.A vibration induced nystagmus (VIN) beating toward the healthy side was obtained for each UVL patient during mastoid vibration. In EO, only sway path was higher in UVL group during vibration of mastoids and posterior cervical muscles.The EO postural impairments of UVL patients could be related to the eye movements or VIN, leading to visual perturbations, or to a proprioceptive error signal, providing an erroneous representation of head position. The vibration-induced sway was too small to be clinically useful. Vestibulo-ocular reflex observed with videonystagmography during mastoid vibration seems more relevant to reveal chronic UVL than vestibulo-spinal reflex observed with posturography.

Specific injuries induced by the practice of trampoline, tumbling and acrobatic gymnastics.

PURPOSE: The recreational and competitive practice of acrobatic sports, that is, trampoline, tumbling and acrobatic gymnastics (ACRO), is growing rapidly around the world. Many studies described the injuries affecting young artistic gymnasts, but only few concerned acrobatic sports. METHODS: During a 5-year period, 357 traumatic events were collected in young acrobats practicing trampoline, tumbling or ACRO. Accident characteristics, level of expertise and training, injury location (upper limb, spine and lower limb), type of tissue injured (bone, cartilage, muscle, ligament and tendon) and provoking factors (intrinsic/behavioural and extrinsic) were investigated. RESULTS: Acrobats of national and international levels were mostly injured. Injuries occurring in acrobatic sports concerned predominantly the lower limbs and concerned in this body part mainly damages to ligaments. Forearm and knee injuries were preferentially related to trampoline. Ankle injuries were preferentially related to tumbling. Wrist injuries were preferentially related to ACRO. Upper limb bone damage and upper limb tendon damage were preferentially related to trampoline and ACRO, respectively. Intrinsic/behavioural factors were the main injury determinant in the three acrobatic sports. CONCLUSIONS: The main injuries in acrobatic sports (i.e. lower limbs) are similar to those observed in artistic gymnastics. Specific injuries may result from falls and incomplete and/or erroneous figure's landing and may also depend to the type of the landing surface. LEVEL OF EVIDENCE: II.

Impact of pre-operative regular physical activity on balance control compensation after vestibular schwannoma surgery.

Vestibular compensation after unilateral vestibular deafferentation is modulated by certain individual characteristics, such as pre-operative visual neurosensory preference or vestibular pattern. Physical activity (PA) allows the implementation of new sensorimotor and behavioral strategies leading to an improvement of balance control. This study aimed to evaluate the effect of the level of PA before surgery on balance compensatory mechanisms in patients after vestibular schwannoma (VS) surgery. Thirty patients with VS, 15 considered as regularly physically active and 15 as sedentary participated in this study, including an evaluation of gaze control by videonystagmography and postural control by a sensory organization test. Patients considered as physically active before surgery presented the best pattern of postural compensation, with the classical decrease in postural performances at short term (i.e. eight days) and the increase in postural performances at middle and long terms (i.e. 90 and 180 days, respectively) after surgery. For the sedentary patients, the consequences of surgery were more difficult to manage at short term, even though this did not prevent the ability to compensate well later on. Pre-operative practice of PA promotes the neuroplasticity of neural networks involved in motor learning, which allows to benefit of physical therapy more rapidly and efficiently.

Visuo-oculomotor deficiency at early-stage idiopathic scoliosis in adolescent girls.

STUDY DESIGN: Cross-sectional study. OBJECTIVE: To determine whether adolescent idiopathic scoliosis (AIS) at onset is associated with oculomotor dysfunction and whether these oculomotor anomalies are correlated to the amplitude of the spine deformation. SUMMARY OF BACKGROUND DATA: AIS is related to abnormalities of postural control. To date, few studies have focused on visuo-oculomotor and vestibulo-ocular functions at early-stage AIS. METHODS: Fifty-three adolescent girls were diagnosed with AIS (mean age: 11.6 ± 2.1 yr) on clinical and radiological criteria (mean Cobb angle: 14.8° ± 5.0°). Visuo-oculomotor and vestibulo-ocular functions were studied with video-oculography, including saccades, smooth pursuit, caloric test, and pendular rotation, with visual vestibular ocular reflex and vestibulo-ocular reflex sequences. Two patient groups were defined according to the mean Cobb angle: group 1 included 29 patients with a Cobb angle from 5° to 14° and group 2 included 24 patients with a Cobb angle from 15° to 25°. RESULTS: The group 2 showed different saccade characteristics than group 1: higher latencies for saccade sequences characterized by temporal uncertainty and predictive direction; lower velocity regardless of the type of the saccades. No difference was observed for saccadic accuracy and smooth-pursuit gain. For the visual vestibular ocular reflex, group 2 showed lower total maximal slow-phase velocity than group 1, whereas the vestibulo-ocular reflex (tested in dark) did not differ between groups. No difference was observed concerning the caloric vestibular test. CONCLUSION: Patients with a Cobb angle of 15° or more presented normal vestibulo-ocular responses but altered visuo-oculomotor functions, especially for the saccadic latency and velocity. This could be the result of a dysfunction of oculomotor pathways at cerebellar and/or brainstem level. These central disorders may be incriminated in the development of AIS.

Biological determinants of postural disorders in elderly women.

Postural control impairments and dizziness, which are major health problems with high secondary morbidity and mortality, increase with aging. Elevated homocysteine (Hcy) level is an age-related metabolic disorder, known to be involved in cardiovascular, neurological, and multisensory dysfunctions. Elevated Hcy level might be involved in sensory balance control systems impairment and dizziness occurrence. Dizziness, fitness Instrumental Activity of Daily Living scale (fitness IADL), systolic arterial pressure with ankle-brachial blood pressure index and homocysteinemia were studied in 61 noninstitutionized elderly women. Clinical balance tests (timed "Up and Go", 10-m walking and one-leg balance) and posturography (including sensory conflicting situations [SCS] and cognitive conflicting situations [CCS]) were performed. Clinical balance control was lower in dizzy women who presented particularly poor stability in SCS. Dizziness was related to low fitness IADL scores (odds ratio [OR] 0.452, 95% CI 0.216-0.946) and to elevated Hcy (OR 8.084, 95% CI 1.992-32.810). Elevated Hcy was correlated with balance disorders both in SCS and CCS. Dizziness is associated with a reduced ability in balance control management. Hcy is related both to dizziness and low postural performance. This relation between elevated Hcy levels and balance impairments, resulting in dizziness, may be explained by its angiotoxicity and neurotoxicity.

Influence of age on postural compensation after unilateral deafferentation due to vestibular schwannoma surgery.

OBJECTIVES/HYPOTHESIS: To evaluate the age-related effects of vestibular schwannoma (VS) on postural control and whether the postoperative postural strategies differ according to age. STUDY DESIGN: Longitudinal, transversal study. METHODS: Forty-seven VS patients were split into three groups according to age (group I, 14 patients aged from 30 to 44 years; group II, 21 patients aged from 45 to 59 years; and group III, 12 patients aged from 60 to 75 years). All patients underwent vestibular and posturographic testing shortly before as well as 8 days and 3 months after surgical tumor removal. RESULTS: Vestibular and postural performance followed a classical time course with degradation just after surgery and recovery 3 months after surgery, whatever the age group. However, in the elderly the improvement of postural performances compared to preoperatively was more important, especially in conflicting situations. CONCLUSIONS: Despite of age-related decline in postural control and cognitive processes, neuroplasticity allowed not only a recovery but even an improvement of balance after surgical VS removal in the elderly. This study highlights the interest of VS surgery even at a more advanced age.

Stocktaking on the development of posturography for clinical use.

This report identifies fundamental problems to be addressed in order to build relevant clinical tests of human balance while standing. The stated purpose of these tests is identification of lesion site and/or definition of functional balance deficits in a specific patient. During a recent consensus meeting (ESCEBD), 60 researchers and experienced clinical users of posturography (14 European countries, 9 different disciplines) inventoried and critically analyzed the various methodologies of posturography currently used for clinical evaluation. To complement posturography, alternative methods of assessment of balance control were considered. The indications for the clinical use of posturography were defined as well as recommendations regarding measurement parameters, type of perturbations and signal analysis techniques to improve assessment of balance control. Consensus was reached that a force platform cannot be considered as a technique which is sufficient on its own to perform a clinically relevant test for the assessment of neuro-otological and musculo-skeletal conditions, evaluation of compensation or treatment (rehabilitation) or prediction of falls. It should be supported by complementary methods, such as segment motion analysis, body-fixed 2D or 3D accelerometer-gyroscope or electromyography. At present, no generally applicable posturography test is available with reasonable sensitivity and specificity for the diagnosis of balance disorders. Perturbation techniques are most likely needed to enhance the diagnostic yield of posturography.

Postural instability in early-stage idiopathic scoliosis in adolescent girls.

STUDY DESIGN: Cross-sectional study. OBJECTIVE: To evaluate whether the amplitude of spine deformation in adolescent idiopathic scoliosis (AIS) is an important factor for postural control at disease onset. SUMMARY OF BACKGROUND DATA: AIS is related to disorders of postural control with potential involvement of vestibular, proprioceptive, and visual input. So far no assessment of postural control has been done in an AIS population at the onset of spine deformation. METHODS: Sixty-five female patients with AIS (mean age: 11.4 ± 2.3 years) were clinically and radiologically assessed at the time of diagnosis and evaluated in posturography, including static tests-with and without sensory conflict-and dynamic tests. Two groups were formed according to the mean Cobb angle of the primary curve. RESULTS: The mean Cobb angle was 14.8° ± 5.1°; 35 patients were included in group I with a Cobb angle of 5° to 14°, and 30 patients into group II with a Cobb angle of 15° to 25°. The latter group displayed higher body sways in static tests, characterized by a larger area covered by center of foot pressure in both eyes open and eyes closed conditions, and by higher lateral oscillations in only the eyes closed condition. Group II patients displayed poorer balance control, mainly in visual and somatosensory conflict conditions. Group II patients used fewer anticipatory strategies to stabilize body oscillations than Group I patients, especially in the more challenging sensory conflict and dynamic situations. CONCLUSION: Poorer postural performance, especially in sensory conflict situations, observed in patients with a Cobb angle greater or equal to 15°, reflect less effective central information processing.

Exercise and dehydration: A possible role of inner ear in balance control disorder.

To study the effect of exercise and dehydration on the postural sensory-motor strategies, 10 sportsmen performed a 45 min-exercise on a cycle ergometer at intensity just below the ventilatory threshold without fluid intake. They performed, before, immediately and 20 min after exercise, a sensory organization test to evaluate balance control in six different sensory situations, that combine three visual conditions (eyes open, eyes closed and sway-referenced visual surround motion) with two platform conditions (stable platform, sway-referenced platform motion). Blood samples were collected before and after exercise. Exercise induced a mild dehydration, characterized by body mass loss and increase in proteinemia. Postural performances decreased immediately after exercise, mainly in the standard situation (eyes open, stable visual surround and platform) and when only the vestibular cue was reliable (eyes closed and sway-referenced platform). Moreover, the decreased use of vestibular input was correlated with the dehydration level. Finally, postural performances normalized 20 min after exercise. Even though muscular fatigue could explain the decrease in postural performances, vestibular fluid modifications may also be involved by its influence on the intralabyrinthine homeostasis, lowering thus the contribution of vestibular information on balance control.

Long-term effects of vestibular compensation on balance control and sensory organisation after unilateral deafferentation due to vestibular schwannoma surgery.

The time-course of central adaptive mechanisms after vestibular schwannoma surgical removal allows, 3 months after surgery (middle term), a satisfactory recovery of balance control. However, the long-term evolution of postural control beyond the end of usual medical follow-up remains unknown. This longitudinal prospective study aimed to assess the long-term effects of vestibular compensation on balance control and sensory organisation in patients operated on for vestibular schwannoma. Thirty-six patients with vestibular schwannoma underwent vestibular and sensory organisation tests, shortly before and 3 months, 6 months and 1 year after surgery. Postural control performances improved 3 months after surgery compared with before surgery; they continued to improve at 6 and 12 months after surgery, especially in conditions highly soliciting vestibular information. In the long term, strategies based on sensorimotor and/or behavioural substitution seem to be reinforced and fine-tuned, particularly in complex postural situations, for which only vestibular information is reliable to control balance.