Support surface related changes in feedforward and feedback control of standing posture

The aim of the study was to investigate the effect of different support surfaces on feedforward and feedback components of postural control. Nine healthy subjects were exposed to external perturbations applied to their shoulders while standing on a rigid platform, foam, and wobble board with eyes open or closed.Electrical activity of nine trunk and leg muscles and displacements of the center of pressure were recorded and analyzed during the time frames typical of feedforward and feedback postural adjustments. Feedforward control of posture was characterized by earlier activation of anterior muscles when the subjects stood on foam compared to a wobble board or a firm surface. In addition, the magnitude of feedforward muscle activity was the largest when the foam was used. During the feedback control, anterior muscles were activated prior to posterior muscles irrespective of the nature of surface. Moreover, the largest muscle activity was seen when the supporting surface was foam. Maximum CoP displacement occurred when subjects were standing on a rigid surface.Altering support surface affects both feedforward and feedback components of postural control. This information should be taken into consideration in planning rehabilitation interventions geared towards improvement of balance.     

Changes in muscle strength,endurance, and reaction of the lower extremities with Tai Chi intervention

This study examines the effects of a 16-week Tai Chi (TC) training program on the muscle strength, endurance, and reaction time of the lower extremities of elderly people. A total of 40 elderly individuals (aged ?60 years) completed the study. They were divided into two groups: the TC group (11 men and 11 women) underwent a supervised TC exercise program for 16 weeks, while the control group (9 men and 9 women) received general education for a comparable time period. Pre- and post-intervention measurements were conducted. An isokinetic dynamometer was used to measure the maximum concentric strength and dynamic endurance of the knee flexors and the extensors, and the maximum concentric strength of the ankle plantarflexors and dorsiflexors. The neuromuscular response of the rectus femoris, semitendinosus, gastrocnemius, and anterior tibialis muscles was measured by the onset latency to sudden perturbations using an electromyography system. After 16 weeks, the TC group showed a 19.9% increase in muscle strength of the knee flexors (p<.000) that was significantly greater than that in the control group (p=.046). There was also a significant decrease in semitendinosus muscle latency (6.6%, p=.014) that was significantly shorter than that in the control group (p=.042). No significant training effects were found in other measures. These results suggest that improving biomechanical characteristics of lower extremity muscles may need longer TC intervention for elderly people.     

健康青年静态立位平衡功能的研究

目的:完善健康青年静态立位平衡参数常模和探讨人处于不利站立条件下姿势控制变化规律。方法:从某军校本科学员中随机抽取108名,对8种不同站立条件下的立位平衡功能进行测试,同时比较不同站立姿势下重心晃动的变化。结果:与睁眼站立相比,闭眼站立和闭眼站立于脚垫上,人体重心会不自主地向脚掌移动,同时重心晃动的轨迹长度和面积明显增加,而单位面积轨迹长度明显降低。另外,人体前后方向晃动的程度较大,而左右晃动的程度稍小。结论:健康人姿势控制由视觉、前庭和下肢本体感觉等共同维持的,任何系统受到限制,都会影响平衡功能。当人处于不利站立条件时,人的身体会本能地向前倾斜来维持平衡,同时本研究为涉及人体立位平衡方面的研究提供了新的研究方法和思路。     

The relationship between dynamic balancing ability and posture-related modulation of the soleus H-reflex

Soleus H-reflex reveals down modulation with increased postural difficulty. Role of this posture-related reflex modulation is thought to shift movement control toward higher motor centers in order to facilitate more precise postural control. Present study hypothesized that the ability to modulate H-reflex is related to one’s ability to dynamically balance while in an unstable posture. This study examined the relationship between dynamic balancing ability and soleus H-reflex posture-related modulation. Thirty healthy adults participated. The soleus maximal H-reflex (Hmax), motor response (Mmax), and background EMG activity (bEMG) were obtained during three postural conditions: prone, open-legged standing, and closed-legged standing. Hmax/Mmax ratios were normalized via the corresponding bEMG in order to remove the effects of background muscle activity from the obtained H-reflex. Reflex modulation was calculated as the ratio of the normalized Hmax/Mmax ratios in one postural condition to another posture in a more difficult condition. Dynamic balancing ability was assessed by testing stability while standing on a wobble board. A significant negative correlation was observed between balancing scores and reflex modulation from open-legged standing to closed-legged standing. This suggests that the ability to modulate monosynaptic stretch reflex excitability in response to a changing posture is a significant factor for dynamic balancing.     

An application of scissored-pair control moment gyroscopes in a design of wearable balance assistance device for the elderly

Impaired balance control ability and degraded functional mobility increases the risk of falling in elderly people. The elderly show more postural sway when standing compared with young people. A sway fall occurs when the center of gravity moves outside the limit of stability. In order to reduce the fall risk from the excessive sway, this study presents the design of wearable balance assistance device for the elderly. Scissored-pair control moment gyroscopes were selected as a torque actuator. A two-axis inclination sensor was used to detect the inclined angle of the wearer’s body. The direction of sway was calculated from the detected inclined angle. The designed device weighs 8.2 kg with a height of 32 cm × width of 40 cm × depth of 22 cm. A multi-segment model of a standing human was used to investigate the device’s performance for balance recovery. According to the simulations, balance recovery in any direction was successfully accomplished with the appropriate initial angle. The relationship between the effective initial angle and detected inclined angle was subsequently established. The stability provided by activation of the device was able to limit the unstable user’s sway boundary. The designed device shows promise for use as a balance assistance device for the elderly.     

平衡功能训练联合肌内效贴对脑卒中偏瘫患者平衡功能、步行功能和生活质量的影响

摘要 目的：观察脑卒中偏瘫患者经肌内效贴联合平衡功能训练治疗后,其步行功能、生活质量及平衡功能的变化。方法：于2018年6月~2020年8月期间,选取我院收治的300例脑卒中偏瘫患者,根据随机数字表法分为对照组（150例,常规康复训练和平衡功能训练）和研究组（150例,常规康复训练、平衡功能训练联合肌内效贴）,均治疗4周。对比两组平衡功能、步行功能、生活质量、睁眼站立、脚前后站立、闭眼站立的重心摆动速度及动态稳定时间。结果：治疗4周后,两组Fugl-Meyer下肢运动功能评定量表（FMA）、Berg平衡量表（BBS）评分较治疗前升高,且研究组高于对照组（P<0.05）。治疗4周后,两组步行功能指标：步频、步长、步速、步幅较治疗前升高,且研究组高于对照组（P<0.05）。治疗4周后,两组SF-36各维度评分较治疗前升高,且研究组高于对照组（P<0.05）。治疗4周后,两组睁眼站立、脚前后站立、闭眼站立的重心摆动速度和动态稳定时间较治疗前降低,且研究组低于对照组（P<0.05）。结论：脑卒中偏瘫患者经肌内效贴联合平衡功能训练治疗后,平衡功能得到较好的恢复,步行能力提高,其生活质量得到改善。     

An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability

Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance.     

Effect of ageing and vision on limb load asymmetry during quiet stance

Although the identification and characterization of limb load asymmetries during quiet standing has not received much research attention, they may greatly extend our understanding of the upright stance stability control. It seems that the limb load asymmetry factor may serve as a veridical measure of postural stability and thus it can be used for early diagnostic of the age-related decline in balance control. The effects of ageing and of vision on limb load asymmetry (LLA) during quiet stance were studied in 43 healthy subjects (22 elderly, mean age 72.3+/-4.0 yr, and 21 young, mean age 23.9+/-4.8 yr). Postural sway and body weight distribution were recorded while the subject was standing on two adjacent force platforms during two 120 s trials: one trial was performed with the eyes open (EO), while the other trial was with the eyes closed (EC). The results indicate that LLA was greater in the old adults when compared with the young control subjects. The LLA values were correlated with the postural sway magnitudes especially in the anteroposterior direction. Eyes closure which destabilized posture resulted in a significant increase of body weight distribution asymmetry in the elderly but not in the young persons. The limb load difference between EO and EC conditions showed a significantly greater effect of vision on LLA in the elderly compared to the young subjects. The observed differences in the LLA may be attributed to the decline of postural stability control in the elderly. Ageing results in the progressive decline of postural control and usually the nervous system requires more time to complete a balance recovery action. To compensate for such a deficiency, different compensatory strategies are developed. One of them, as evidenced in our study, is preparatory limb unload strategy (a stance asymmetry strategy) which could significantly shorten reaction time in balance recovery.     

Not all instability training devices enhance muscle activation in highly resistance-trained individuals

The objective of this study was to measure the electromyographic (EMG) activity of the soleus, bicep femoris, rectus femoris, lower abdominal, and lumbosacral erector spinae (LSES) muscles with a variety of (a) instability devices, (b) stable and unstable (Dyna Disc) exercises, and (c) a fatiguing exercise in 16 highly conditioned individuals. The device protocol had participants assume standing and squatting postures while balancing on a variety of unstable platforms (Dyna Disc, BOSU ball, wobble board, and a Swiss ball) and a stable floor. The exercise protocol had subjects performing, static front lunges, static side lunges, 1-leg hip extensions, 1-leg reaches, and calf raises on a floor or an unstable Dyna Disc. For the fatigue experiment, a wall sit position was undertaken under stable and unstable (BOSU ball) conditions. Results for the device experiment demonstrated increased activity for all muscles when standing on a Swiss ball and all muscles other than the rectus femoris when standing on a wobble board. Only lower abdominals and soleus EMG activity increased while squatting on a Swiss ball and wobble board. Devices such as the Dyna Disc and BOSU ball did not exhibit significant differences in muscle activation under any conditions, except the LSES in the standing Dyna Disc conditions. During the exercise protocol, there were no significant changes in muscle activity between stable and unstable (Dyna Disc) conditions. With the fatigue protocol, soleus EMG activity was 51% greater with a stable base. These results indicate that the use of moderately unstable training devices (i.e., Dyna Disc, BOSU ball) did not provide sufficient challenges to the neuromuscular system in highly resistance-trained individuals. Since highly trained individuals may already possess enhanced stability from the use of dynamic free weights, a greater degree of instability may be necessary.     

Does whole-body vibration training have acute residual effects on postural control ability of elderly women?

The purpose of this study was to investigate acute residual effects of a single vibration session on balance control in a group of elderly women. Several studies, in fact, have shown that whole-body vibration (WBV) training may improve balance in the elderly, but possible side effects of acute exposure to WBV, such as temporary reduction of balance control ability because of perturbations of the vestibular system, have not been investigated. Twenty-two healthy elderly women (71.8 ± 4.7 years of age) were trained with a 9.5-minute bout of static and dynamic knee-extensor exercises executed on a vibrating platform (Well-net Vibe Revolution). The vibration frequency was set at 35 Hz. A subgroup of 14 subjects performed the same exercise protocol also without the vibrations to discriminate between vibration and exercise effects. Balance control ability was assessed through computerized posturography: a force plate (Bertec Co, Columbus, OH, USA) was used to measure the center of pressure trajectories during 4 different experimental trials: before, immediately after, 15 minutes after, and 60 minutes after the training. A set of postural parameters, typically adopted to assess elderly subjects, was then computed and 2-way analysis of variance was used to determine differences between values found in the 4 postural tests (level of significance p = 0.05) in the 2 groups. The results showed no significant variations in the postural parameters recorded during the 4 sessions. A significant group effect was found for 2 postural parameters, with no interaction between the 2 factors. In conclusion, the proposed single bout of WBV does not induce dangerous acute effects on elderly women balance control ability and could be safely administered as part of a long-term intervention program.     

Monocyte and T-cell responses to exercise training in elderly subjects

The purpose of this study was to examine the effects of exercise training on age-related impairment of immune parameters related to T-cell activation in elderly individuals. Twenty-four elderly subjects were assigned to an exercise training group (EXC: 3 men, 9 women; age 61-76 years) or a nonexercise control group (CON: 4 men, 8 women; age 62-79 years). Subjects in EXC participated in exercise sessions 2 d·wk(-1) for 12 weeks. The training session included stretching and endurance exercise (10 minutes), resistance training comprised leg extension, leg press, hip abduction, and hip adduction using exercise machine and each subject's body weight. Subjects in CON maintained their normal physical activity levels during the study period. Blood samples were collected before and after the training period. Samples were measured for the numbers of leukocytes, lymphocytes, and monocytes, and for CD3(+), CD4(+), CD8(+), CD28(+)CD4(+), CD28(+)CD8(+), TRL-4(+)CD14(+), and CD80(+)CD14(+) cells. The number of leukocytes, lymphocytes, monocytes, CD3(+), CD4(+), and CD8(+) cells did not change after 12 weeks in either EXC or CON. The number of CD28(+)CD8(+) cells increased significantly after training in EXC (p ≤ 0.05), although CON showed no significant change. In the EXC group, CD80(+)CD14(+) cell counts were significantly higher after training (p ≤ 0.05), but the TLR-4(+)CD14(+) cell counts were unchanged. In the CON group, no significant alteration existed in TLR-4(+)CD14(+) and CD80(+)CD14(+) cell numbers. In conclusion, exercise training in elderly people is associated with increased CD28-expressing Tc cells and CD80-expressing monocytes. Therefore, exercise training might upregulate monocyte and T-cell-mediated immunity in elderly people.     

Effects of a low-intensity conditioning programme on V˙O2max and maximal instantaneous peak power in elderly women

The effects of 12 weeks of a low-intensity general conditioning programme on maximal instantaneous peak power (Wpeak) and maximal oxygen uptake (VO2max) were examined in 20 elderly women. After medical, familiarisation, and ethical procedures, the subjects were randomly divided into either a training and or a control group. The training group [n = 11; mean (SD) age 63.0 (3.1) years] agreed to take part in a 12-week training programme at an exercise intensity kept under 60% of the heart rate reserve for about 60 min, 3 times a week. The control group [n = 9; mean (SD) age 63.5 (3.3) years] did not perform any particular physical training. Before and after the training period, all participants underwent anthropometric measures and a maximal cycling test to exhaustion to measure their VO2max. In addition, Wpeak was determined 1 week later by the subjects performing a vertical jump from a squatting position on a force platform. Following training, neither the anthropometric characteristics nor the VO2max changed in either of the groups. In contrast, Wpeak increased significantly (P < 0.001) in the training group, but did not change in the control group. This result could be interpreted as the result of an improved level of neuromuscular activation. Furthermore, it shows that although muscle power declines with age at a faster rate than does aerobic power, its sensitivity to training seems to be higher than that of the aerobic system.     

The assessment of posture control in the elderly using the displacement of the center of pressure after forward platform translation

We investigated the change of the center of pressure (COP) after forward platform translations in healthy subjects. These studies were performed on 26 normal young subjects and 20 healthy elderly subjects, who had a normal neurologic examination. Subjects stood barefoot on a three dimensional force plate on the platform, with feet parallel. The duration of the forward platform translations was 0.15 s, and the displacements were 3.75, 7.5, 10, 15, 20, and 30 mm. Six trials were carried out at random. The COP data were recorded for 35 s during standing, and were analyzed for 5 s after translation. With the platform translation displacements from 3.75 to 15 mm, displacement of the COP showed a tendency to increase in all subjects. Whereas with the stimuli between 20 and 30 mm, the results were more varied. The elderly group showed significantly (p<0.05) larger sway than the young group. These results indicate that the individual ability of posture control may be assessed by means of measuring the sway of the center of gravity after platform translation. Electromyography was carried out simultaneously, it showed that elderly people contrary to young subjects used proximal biceps femoris and distal foot muscles at an early stage of the platform translation (p<0.05), suggesting lack of ankle stability with aging.     

The relationship between physical fitness and ambulatory activity in very elderly women with normal functioning and functional limitations

The effect of daily ambulatory activity on physical fitness has not yet been identified by quantitatively measuring the time spent on the intensity levels of ambulatory activity in elderly women over 75 with different functional capacity levels. The subjects consisted of 147 elderly women over 75 years old (82.8±4.3 years old) who were all capable of performing basic daily activities by themselves. Physical fitness was measured for 7 items (handgrip strength, knee extensor strength, postural stability, stepping, one-legged standing time with eyes open, 10 m walking, and the Timed Up and Go Test). The subjects wore a triaxial accelerometer for 2 consecutive weeks to measure their daily physical activities. The functional capacity level was assessed by the Tokyo Metropolitan Institute of Gerontology Index of Competence. The subjects were divided into two groups, a group with a score ≥10 points (high functional capacity group, n=59) and a score <10 points (low functional capacity group, n=88), and the relationship between physical fitness and physical activity was examined in both groups. In both the high and low functional capacity groups, 10 m walking, the Timed Up and Go Test, and one-legged standing time with eyes open significantly correlated with either the total steps/day or the ambulatory activity intensity. In the high functional capacity group, the knee extensor strength also significantly correlated with the total steps/day and moderate ambulatory activity. It is suggested that very elderly women with a reduced functional capacity should maintain their mobility by simply increasing their daily ambulatory activity.     

10周核心力量练习对男性中老年人平衡能力的影响

目的：探讨核心力量练习对中老年男性平衡能力的影响,为运动锻炼改善老年人平衡能力和降低跌倒风险提供依据。方法：选取16名50~60岁男性中老年人,随机分为试验组（核心力量练习）和对照组,每组8人。利用悬吊绳和瑜伽垫进行动、静态支撑与推拉练习以及徒手下肢力量等间歇性组合核心力量训练,共练习10周,每周4~5次,每次50~60 min。对照组保持原有生活习惯。锻炼前后测定受试者静态平衡和动态平衡等指标。结果：①锻炼后试验组闭眼单脚站立时间和动态平衡得分较锻炼前显著升高分别为（9.00±2.27） s、（10.63±1.69） s,P<0.01;（77.38±10.94）、（89.50±5.53）,P<0.01。②锻炼后试验组星形伸展平衡测试（SEBT）,右腿支撑时左腿在8个方向、左腿支撑时右腿在6个方向的SEBT值均较锻炼前显著增加（P<0.01）。结论：10周核心力量练习显著提高男性中老年人的动、静态平衡能力。     

Modulation of the Cutaneous Silent Period in the Upper-Limb with Whole-Body Instability

The silent period induced by cutaneous electrical stimulation of the digits has been shown to be task-dependent, at least in the grasping muscles of the hand. However, it is unknown if the cutaneous silent period is adaptable throughout muscles of the entire upper limb, in particular when the task requirements are substantially altered. The purpose of the present study was to examine the characteristics of the cutaneous silent period in several upper limb muscles when introducing increased whole-body instability. The cutaneous silent period was evoked in 10 healthy individuals with electrical stimulation of digit II of the right hand when the subjects were seated, standing, or standing on a wobble board while maintaining a background elbow extension contraction with the triceps brachii of ~5% of maximal voluntary contraction (MVC) strength. The first excitatory response (E1), first inhibitory response (CSP), and second excitatory response (E2) were quantified as the percent change from baseline and by their individual durations. The results showed that the level of CSP suppression was lessened (47.7 ± 7.7% to 33.8 ± 13.2% of baseline, p = 0.019) and the duration of the CSP inhibition decreased (p = 0.021) in the triceps brachii when comparing the seated and wobble board tasks. For the wobble board task the amount of cutaneous afferent inhibition of EMG activity in the triceps brachii decreased; which is proposed to be due to differential weighting of cutaneous feedback relative to the corticospinal drive, most likely due to presynaptic inhibition, to meet the demands of the unstable task.     

Down training of the elderly soleus H reflex with the use of a spinally induced balance perturbation.

The purpose of this study was to determine the ability of the elderly central nervous system to modulate spinal reflex output to functionally decrease a spinally induced balance perturbation. In this case, the soleus H reflex was used as the source of perturbation. Therefore, decreasing (down training) of the soleus H reflex was necessary to counteract this perturbation and to better maintain postural control. In addition to assessing the effect of this perturbation on the H reflex, static postural stability was measured to evaluate possible functional effects. Ten healthy young subjects (age: 27.0 +/- 4.6 yr) and 10 healthy elderly subjects (age: 71.4 +/- 5.1 yr) participated in this study. Subjects underwent balance perturbation on 2 consecutive days. On day 1 of perturbation, significant down training of the soleus H reflex was demonstrated in both young (-20.4%) and elderly (-18.7%) subjects. On day 2 of perturbation, significant down training of the soleus H reflex was again demonstrated in both young (-24.6%) and elderly (-21.0%) subjects. Analysis of static stability after the 2 days of balance perturbation revealed a significant 10.1% decrease in the area of sway in elderly subjects. In conclusion, this study demonstrated that healthy, elderly subjects compared with young subjects were equally capable of down training the soleus H reflex in response to a balance perturbation. Furthermore, the improvement in static stability through balance training may provide further evidence that balance can be retrained and rehabilitated in subjects with decreased reflex function.     

Dynamic balance control during sit-to-stand movement: an examination with the center of mass acceleration

The purpose of this study was to establish the region of stability of balance control using the center of mass (COM) acceleration and to characterize age-related differences during sit-to-stand (STS) movement. Whole body motion data were collected from 10 young and 10 elderly subjects while performing STS at their self-selected manners. In addition, young subjects were asked to perform another block of trials with their trunk purposely bent forward prior to seat-off. With the use of a single-link-plus-foot inverted pendulum model, boundaries for the region of stability were determined based on the COM position at seat-off and its instantaneous velocity or its peak acceleration (ROSv or ROSa, respectively). No significant group differences were detected in COM velocities at seat-off. However, peak COM accelerations differed significantly between groups and conditions. This suggested that even though a similar COM momentum was observed at seat-off, this momentum was controlled differently prior to seat-off. Young and elderly subjects utilized similar strategies but with different COM acceleration profiles to perform STS. Furthermore, data from an elderly subject who complained of difficulty in STS during the experiment were located outside the forward boundary of the ROSa, demonstrating a potential use of ROSa to differentiate individuals with declined balance control ability. The ROSa could provide insights into how the COM is controlled prior to seat-off, which may allow us to better identify elderly individuals who are most likely at a risk for imbalance or falls.     

The effects of plyometric vs. dynamic stabilization and balance training on power, balance, and landing force in female athletes

Neuromuscular training protocols that include both plyometrics and dynamic balance exercises can significantly improve biomechanics and neuromuscular performance and reduce anterior cruciate ligament injury risk in female athletes. The purpose of this study was to compare the effects of plyometrics (PLYO) versus dynamic stabilization and balance training (BAL) on power, balance, strength, and landing force in female athletes. Either PLYO or BAL were included as a component of a dynamic neuromuscular training regimen that reduced measures related to ACL injury and increased measures of performance. Nineteen high school female athletes participated in training 3 times a week for 7 weeks. The PLYO (n = 8) group did not receive any dynamic balance exercises and the BAL (n = 11) group did not receive any maximum effort jumps during training. Pretraining vs. posttraining measures of impact force and standard deviation of center of pressure (COP) were recorded during a single leg hop and hold. Subjects were also tested for training effects in strength (isokinetic and isoinertial) and power (vertical jump). The percent change from pretest to posttest in vertical ground reaction force was significantly different between the BAL and PLYO groups on the dominant side (p < 0.05). Both groups decreased their standard deviation of center of pressure (COP) during hop landings in the medial/lateral direction on their dominant side, which equalized pretested side to side differences. Both groups increased hamstrings strength and vertical jump. The results of this study suggest that both PLYO and BAL training are effective at increasing measures of neuromuscular power and control. A combination of PLYO and BAL training may further maximize the effectiveness of preseason training for female athletes.     

Learning Upright Standing on a Multiaxial Balance Board

Upright stance on a balance board is a skill requiring complex rearrangement of the postural control. Despite the large use of these boards in training the standing posture, a comprehensive analysis of the learning process underlying the control of these devices is lacking. In this paper learning to maintain a stable stance on a multiaxial oscillating board was studied by analyzing performance changes over short and long periods. Healthy participants were asked to keep the board orientation as horizontal as possible for 20 sec, performing two sessions of 8 trials separated by 15-min pause. Memory consolidation was tested one week later. Amplitude and variability of the oscillations around horizontal plane and area and sway path of the board displacement decreased rapidly over the first session. The performance was stable during the second session, and retained after 1 week. A similar behavior was observed in the anterior-posterior and medial-lateral directions for amplitude and variability parameters, with less stable balance in the anterior-posterior direction. Approximate entropy and mean power frequency, assessing temporal dynamics and frequency content of oscillations, changed only in the anterior-posterior direction during the retention test. Overall, the ability to stand on a balance board is rapidly acquired, and retained for long time. The asymmetric stability between anterior-posterior and medial-lateral directions replicates a structure observed in other standing stances, suggesting a possible transfer from previous postural experiences. Conversely, changes in the temporal dynamics and the frequency content could be associated with new postural strategies developed later during memory consolidation.