Neck muscle fatigue and spatial orientation during stepping in place in humans

Balance alterations are associated with neck pain and neck muscle endurance in migraine

BACKGROUND

Migraine patients may present with both cervical and balance dysfunctions. The neck plays an important role in balance by providing substantial proprioceptive input, which is integrated in the central nervous system and influences the balance control systems. Whether balance and neck dysfunctions are associated in patients with migraine is still to be explored.

OBJECTIVES

This study aimed to assess the association between the sensory organization test of balance with neck pain features, cervical strength, endurance, and range of motion in patients with migraine.

METHODS

Sixty-five patients with migraine underwent the sensory organization test assessed with the Equitest-Neurocom® device. Maximum voluntary isometric contraction, cervical flexion and extension range of motion, and cervical flexor and extensor endurance were assessed. In addition, the features of migraine and neck pain were collected. Patients were dichotomized according to cut-off scores of balance performance and the association between outcomes were explored.

RESULTS

Patients with reduced balance performance presented a higher frequency of migraine (p = 0.035), a higher frequency of aura (p = 0.002), greater neck pain intensity (p = 0.013), and decreased endurance of cervical flexors (p = 0.010) and extensors (p < 0.0001). The total balance score was correlated with age (r = -0.33; p = 0.007), migraine frequency (r = -0.29; p = 0.021), neck pain intensity (r = -0.26; p = 0.038), and endurance of the cervical flexors (r = 0.39; p = 0.001) and extensors (r = 0.36; p = 0.001). Migraine frequency, neck pain intensity, and endurance of the cervical flexors can predict 21% of the sensory organization test variability.

CONCLUSION

Neck pain features and endurance of the cervical muscles are related to reduced balance performance in patients with migraine. These results shed light to a better understanding of balance alterations in migraine patients.

Podokinetic After-Rotation Is Transiently Enhanced or Reversed by Unilateral Axial Muscle Proprioceptive Stimulation

Unilateral axial muscle vibration, eliciting a proprioceptive volley, is known to incite steering behavior. Whole-body rotation while stepping in place also occurs as an after-effect of stepping on a circular treadmill (podokinetic after-rotation, PKAR). Here, we tested the hypothesis that PKAR is modulated by axial muscle vibration. If both phenomena operate through a common pathway, enhancement or cancellation of body rotation would occur depending on the stimulated side when vibration is administered concurrently with PKAR. Seventeen subjects participated in the study. In one session, subjects stepped in place eyes open on the center of a platform that rotated counterclockwise 60°/s for 10 min. When the platform stopped, subjects continued stepping in place blindfolded. In other session, a vibratory stimulus (100 Hz, 2 min) was administered to right or left paravertebral muscles at lumbar level at two intervals during the PKAR. We computed angular body velocity and foot step angles from markers fixed to shoulders and feet. During PKAR, all subjects rotated clockwise. Decreased angular velocity was induced by right vibration. Conversely, when vibration was administered to the left, clockwise rotation velocity increased. The combined effect on body rotation depended on the time at which vibration was administered during PKAR. Under all conditions, foot step angle was coherent with shoulder angular velocity. PKAR results from continuous asymmetric input from the muscles producing leg rotation, while axial muscle vibration elicits a proprioceptive asymmetric input. Both conditioning procedures appear to produce their effects through a common mechanism. We suggest that both stimulations would affect our straight ahead by combining their effects in an algebraic mode.

Disturbance of neck proprioception and feed-forward motor control following static neck flexion in healthy young adults

The highly complex proprioceptive system provides neuromuscular control of the mobile cervical spine. Static neck flexion can induce the elongation of posterior tissues and altered afferent input from the mechanoreceptors. The purpose of this study was to examine the effect of prolonged static neck flexion on neck proprioception and anticipatory postural adjustments. Thirty-eight healthy participants (20 females and 18 males) between the ages of 20-35 years with no history of neck, low back, and shoulder pain enrolled in this study. Neck proprioception and anticipatory muscle activity were tested before and after 10-min static neck flexion. For assessment of neck proprioception, each participant was asked to perform 10 trials of the cervicocephalic relocation test to the neutral head position after active neck rotation to the left and right sides. Anticipatory postural adjustments were evaluated during a rapid arm flexion test. Following the flexion, the absolute and variable errors in head repositioning significantly increased (p < 0.05). The results also showed that there was a significant delay in the onset of myoelectric activity of the cervical erector spinae muscles after flexion (p = 0.001). The results of this study suggested that a 10-min static flexion can lead to changes in the neck proprioception and feed-forward control due to mechanical and neuromuscular changes in the viscoelastic cervical spine structures. These changes in sensory-motor control may be a risk factor for neck pain and injury.

Disturbed cervical proprioception affects perception of spatial orientation while in motion

The proprioceptive, visual and vestibular sensory systems interact to maintain dynamic stability during movement. The relative importance and interplay between these sensory systems is still not fully understood. Increased knowledge about spatial perception and postural orientation would provide better understanding of balance disorders, and their rehabilitation. Displacement of the body in space was recorded in 16 healthy subjects performing a sequence of stepping-in-place tests without any visual or auditory cues. Spatial displacement and orientation in space were determined by calculating two parameters, “Moved distance (sagittal + lateral displacement)” and “Rotation”. During the stepping-in-place tests vibration were applied in a randomized order on four different cervical muscles, and the effects were compared between muscles and to a non-vibration baseline condition. During the tests a forward displacement (“Moved distance”) was found to be the normal behavior, with various degrees of longitudinal rotation (“Rotation”). The moved distance was significantly larger when the vibration was applied on the dorsal muscles (916 mm) relative to on ventral muscles (715 mm) (p = 0.003) and the rate of displacement was significantly larger for dorsal muscles (36.5 mm/s) relative to ventral (28.7 mm/s) vs (p = 0.002). When vibration was applied on the left-sided muscles, 16° rotation to the right was induced (p = 0.005), whereas no significant rotation direction was induced with right-sided vibration (3°). The rate of rotation was significantly larger for vibration applied on ventral muscles (0.44°/s) relative to on dorsal (0.33°/s) (p = 0.019). The results highlight the influence of cervical proprioception on the internal spatial orientation, and subsequent for postural control.

The effect of neurac training in patients with chronic neck pain

[Purpose] This study aimed to investigate the effects of neurac training on pain, function, balance, fatigability, and quality of life. [Subjects and Methods] Subjects with chronic neck pain who were treated in S hospital were included in this study; they were randomly allocated into two groups, i.e., the experimental group (n = 10) and the control group (n = 10). Both groups received traditional physical therapy for 3 sessions for 30 min per week for 4 weeks. The experimental group practiced additional neurac training for 30 min/day, for 3 days per week for 4 weeks. All subjects were evaluated using the visual analogue scale (VAS), the neck disability index (NDI), the biorescue (balance), the questionnaire for fatigue symptoms (fatigue), and the medical outcome 36-item short form health survey (SF-36) pre- and post-intervention. [Results] The experimental group effectively improved their pain, function, balance, fatigability, and quality of life. [Conclusion] Neurac training is thus considered an effective training program that enhances body functionality by improving pain, function, balance ability, fatigability, and quality of life in patients with chronic neck pain.

Long-lasting effects of neck muscle vibration and contraction on self-motion perception of vestibular origin

OBJECTIVE

To show that neck proprioceptive input can induce long-term effects on vestibular-dependent self-motion perception.

METHODS

Motion perception was assessed by measuring the subject's error in tracking in the dark the remembered position of a fixed target during whole-body yaw asymmetric rotation of a supporting platform, consisting in a fast rightward half-cycle and a slow leftward half-cycle returning the subject to the initial position. Neck muscles were relaxed or voluntarily contracted, and/or vibrated. Whole-body rotation was administered during or at various intervals after the vibration train. The tracking position error (TPE) at the end of the platform rotation was measured during and after the muscle conditioning maneuvers.

RESULTS

Neck input produced immediate and sustained changes in the vestibular perceptual response to whole-body rotation. Vibration of the left sterno-cleido-mastoideus (SCM) or right splenius capitis (SC) or isometric neck muscle effort to rotate the head to the right enhanced the TPE by decreasing the perception of the slow rotation. The reverse effect was observed by activating the contralateral muscle. The effects persisted after the end of SCM conditioning, and slowly vanished within several hours, as tested by late asymmetric rotations. The aftereffect increased in amplitude and persistence by extending the duration of the vibration train (from 1 to 10min), augmenting the vibration frequency (from 5 to 100Hz) or contracting the vibrated muscle. Symmetric yaw rotation elicited a negligible TPE, upon which neck muscle vibrations were ineffective.

CONCLUSIONS

Neck proprioceptive input induces enduring changes in vestibular-dependent self-motion perception, conditional on the vestibular stimulus feature, and on the side and the characteristics of vibration and status of vibrated muscles. This shows that our perception of whole-body yaw-rotation is not only dependent on accurate vestibular information, but is modulated by proprioceptive information related to previously experienced position of head with respect to trunk.

SIGNIFICANCE

Tonic proprioceptive inflow, as might occur as a consequence of enduring or permanent head postures, can induce adaptive plastic changes in vestibular-dependent motion sensitiveness. These changes might be counteracted by vibration of selected neck muscles.

Neck proprioception shapes body orientation and perception of motion

This review article deals with some effects of neck muscle proprioception on human balance, gait trajectory, subjective straight-ahead (SSA), and self-motion perception. These effects are easily observed during neck muscle vibration, a strong stimulus for the spindle primary afferent fibers. We first remind the early findings on human balance, gait trajectory, SSA, induced by limb, and neck muscle vibration. Then, more recent findings on self-motion perception of vestibular origin are described. The use of a vestibular asymmetric yaw-rotation stimulus for emphasizing the proprioceptive modulation of motion perception from the neck is mentioned. In addition, an attempt has been made to conjointly discuss the effects of unilateral neck proprioception on motion perception, SSA, and walking trajectory. Neck vibration also induces persistent aftereffects on the SSA and on self-motion perception of vestibular origin. These perceptive effects depend on intensity, duration, side of the conditioning vibratory stimulation, and on muscle status. These effects can be maintained for hours when prolonged high-frequency vibration is superimposed on muscle contraction. Overall, this brief outline emphasizes the contribution of neck muscle inflow to the construction and fine-tuning of perception of body orientation and motion. Furthermore, it indicates that tonic neck-proprioceptive input may induce persistent influences on the subject's mental representation of space. These plastic changes might adapt motion sensitiveness to lasting or permanent head positional or motor changes.

Avaliação dos distúrbios do controle sensório-motor em pessoas com dor cervical mecânica: uma revisão

INTRODUÇÃO: A dor cervical mecânica é problema comum na população em geral e engloba a dor cervical aguda, as lesões em chicote, as disfunções cervicais e a dor cervical-ombro. A limitação da amplitude de movimento, a sensação de aumento da tensão muscular, a cefaleia, a braquialgia, a vertigem e outros sinais e sintomas são manifestações comuns e podem ser agravados por movimentos ou pela manutenção de posturas da coluna cervical. Estudos recentes mostram comprometimento no controle sensório-motor em pessoas com dor cervical manifestando-se por alterações da cinestesia cervical com dificuldade no reconhecimento da posição da cabeça, do movimento dos olhos e do equilíbrio. OBJETIVOS: Descrever, com base na revisão da literatura, as manifestações e os métodos de avaliação dos distúrbios sensório-motores relacionados à dor cervical mecânica. MÉTODOS: Para a revisão foram utilizadas as bases de dados de literatura científica indexada no período de 1965 a 2009. Considerou-se para a inclusão os artigos que abordassem a dor cervical mecânica e os distúrbios da propriocepção cervical, da coordenação dos movimentos dos olhos e do equilíbrio. Não houve restrição quanto à língua de publicação. O processo de seleção foi realizado por dois examinadores independentes, considerando a evidência científica em ordem decrescente, havendo preferência para as meta-análises e os estudos randomizados controlados. RESULTADOS: Dos 119 artigos encontrados, 69 preenchiam os critérios de inclusão. DISCUSSÃO: A presença de alterações dos músculos e das articulações cervicais, o processo de envelhecimento e a presença de dor cervical são descritos como fatores que alteram o sistema somatossensorial cervical e devem ser considerados também como perpetuantes. CONCLUSÃO: As alterações dos sistemas visual, do equilíbrio e proprioceptivo não podem ser desprezadas e devem ser consideradas durante a avaliação fisioterapêutica dos distúrbios cervicais, visto que existe uma integração entre os sistemas.

Influence of prolonged unilateral cervical muscle contraction on head repositioning--decreased overshoot after a 5-min static muscle contraction task

The ability to reproduce a specified head-on-trunk position can be an indirect test of cervical proprioception. This ability is affected in subjects with neck pain, but it is unclear whether and how much pain or continuous muscle contraction factors contribute to this effect. We studied the influence of a static unilateral neck muscle contraction task (5 min of lateral flexion at 30% of maximal voluntary contraction) on head repositioning ability in 20 subjects (10 women, 10 men; mean age 37 years) with healthy necks. Head repositioning ability was tested in the horizontal plane with 30 degrees target and neutral head position tests; head position was recorded by Zebris((R)), an ultrasound-based motion analyser. Head repositioning ability was analysed for accuracy (mean of signed differences between introduced and reproduced positions) and precision (standard deviation of the differences). Accuracy of head repositioning ability increased significantly after the muscle contraction task, as the normal overshoot was reduced. An average overshoot of 7.1 degrees decreased to 4.6 degrees after the muscle contraction task for the 30 degrees target and from 2.2 degrees to 1.4 degrees for neutral head position. The increased accuracy was most pronounced for movements directed towards the activated side. Hence, prolonged unilateral neck muscle contraction may increase the sensitivity of cervical proprioceptors.

Cervicogenic dizziness – musculoskeletal findings before and after treatment and long-term outcome

PURPOSE

To explore musculoskeletal findings in patients with cervicogenic dizziness and how these findings relate to pain and dizziness. To study treatment effects and long-term symptom progress.

METHOD

Twenty-two patients (20 women, 2 men; mean age 37 years) with suspected cervicogenic dizziness underwent a structured physical examination before and after physiotherapy guided by the musculoskeletal findings. Questionnaires were sent to the patients six months and two years after treatment.

RESULTS

Dorsal neck muscle tenderness and tightness was found in a majority of the patients. Zygapophyseal joint tenderness was found at all cervical levels. Cervical range of motion was equal to or larger than expected age and gender matched values. The cervico-thoracic region was often hypomobile. Most patients had postural imbalance. Dynamic stabilization capacity was reduced. Suboccipital muscles tightness correlated with posture imbalance and poor neck stability. The treatment resulted in reduced tenderness in levator scapula, high and middle paraspinal and temporalis muscles and zygapophyseal joints at C4-C7 and increased cervico-thoracic mobility. Reduction of middle paraspinal muscle tenderness correlated with neck pain relief. Postural alignment improved, as did dynamic stabilization in trunk, neck and shoulders. After 6 months, 13 of the 17 patients had still no or less neck pain and 14 had no or less dizziness. After 2 years, 7 patients had no or less neck pain and 11 no or less dizziness.

CONCLUSION

Patients with suspected cervicogenic dizziness have some musculoskeletal findings in common. Treatment based on these findings reduces neck pain as well as dizziness long-term but some patients might need a maintenance strategy.

Sensorimotor function and dizziness in neck pain: implications for assessment and management

SYNOPSIS

The term sensorimotor describes all the afferent, efferent, and central integration and processing components involved in maintaining stability in the postural control system through intrinsic motor-control properties. The scope of this paper is to highlight the sensorimotor deficits that can arise from altered cervical afferent input. From a clinical orthopaedic perspective, the peripheral mechanoreceptors are the most important in functional joint stability; but in the cervical region they are also important for postural stability, as well as head and eye movement control. Consequently, conventional musculoskeletal intervention approaches may be sufficient only for patients with neck pain and minimal sensorimotor proprioceptive disturbances. Clinical experience and research indicates that significant sensorimotor cervical proprioceptive disturbances might be an important factor in the maintenance, recurrence, or progression of various symptoms in some patients with neck pain. In these cases, more specific and novel treatment methods are needed which progressively address neck position and movement sense, as well as cervicogenic oculomotor disturbances, postural stability, and cervicogenic dizziness. In this commentary we review the most relevant theoretical and practical knowledge on this matter and implications for clinical assessment and management, and we propose future directions for research.

LEVEL OF EVIDENCE

Level 5.

Post-effect of forward and backward locomotion on body orientation in space during quiet stance

Neural circuits responsible for stance control serve other motor tasks as well. We investigated the effect of prior locomotor tasks on stance, hypothesizing that postural post-effects of walking are dependent on walking direction. Subjects walked forward (WF) and backward (WB) on a treadmill. Prior to and after walking they maintained quiet stance. Ground reaction forces and centre of foot pressure (CoP), ankle and hip angles, and trunk inclination were measured during locomotion and stance. In WF compared to WB, joint angle changes were reversed, trunk was more flexed, and movement of CoP along the foot sole during the support phase of walking was opposite. During subsequent standing tasks, WB induced ankle extension, hip flexion, trunk backward leaning; WF induced ankle flexion and hip extension. The body CoP was displaced backward post-WB and forward post-WF. The post-effects are walking-direction dependent, and possibly related to foot-sole stimulation pattern and trunk inclination during walking.

Sensorimotor disturbances in neck disorders affecting postural stability, head and eye movement control

The receptors in the cervical spine have important connections to the vestibular and visual apparatus as well as several areas of the central nervous system. Dysfunction of the cervical receptors in neck disorders can alter afferent input subsequently changing the integration, timing and tuning of sensorimotor control. Measurable changes in cervical joint position sense, eye movement control and postural stability and reports of dizziness and unsteadiness by patients with neck disorders can be related to such alterations to sensorimotor control. It is advocated that assessment and management of abnormal cervical somatosensory input and sensorimotor control in neck pain patients is as important as considering lower limb proprioceptive retraining following an ankle or knee injury. Afferent information from the cervical receptors can be altered via a number of mechanisms such as trauma, functional impairment of the receptors, changes in muscle spindle sensitivity and the vast effects of pain at many levels of the nervous system. Recommendations for clinical assessment and management of such sensorimotor control disturbances in neck disorders are presented based on the evidence available to date.

A musculoskeletal model of low grade connective tissue inflammation in patients with thyroid associated ophthalmopathy (TAO): the WOMED concept of lateral tension and its general implications in disease

Background

Low level connective tissue inflammation has been proposed to play a role in thyroid associated ophthalmopathy (TAO). The aim of this study was to investigate this postulate by a musculoskeletal approach together with biochemical parameters.

Methods

13 patients with TAO and 16 controls were examined. Erythrocyte levels of Zn, Cu, Ca²⁺, Mg, and Fe were determined. The musculoskeletal evaluation included observational data on body posture with emphasis on the orbit-head region. The angular foot position in the frontal plane was quantified following gait observation. The axial orientation of the legs and feet was evaluated in an unloaded supine position. Functional propioceptive tests based on stretch stimuli were done by using foot inversion and foot rotation.

Results

Alterations in the control group included neck tilt in 3 cases, asymmetrical foot angle during gait in 2, and a reaction to foot inversion in 5 cases. TAO patients presented facial asymmetry with displaced eye fissure inclination (mean 9.1°) as well as tilted head-on-neck position (mean 5.7°). A further asymmetry feature was external rotation of the legs and feet (mean 27°). Both foot inversion as well as foot rotation induced a condition of neuromuscular deficit. This condition could be regulated by gentle acupressure either on the lateral abdomen or the lateral ankle at the acupuncture points gall bladder 26 or bladder 62, respectively. In 5 patients, foot rotation produced a phenomenon of moving toes in the contra lateral foot. In addition foot rotation was accompanied by an audible tendon snapping. Lower erythrocyte Zn levels and altered correlations between Ca²⁺, Mg, and Fe were found in TAO.

Conclusion

This whole body observational study has revealed axial deviations and body asymmetry as well as the phenomenon of moving toes in TAO. The most common finding was an arch-like displacement of the body, i.e. eccentric position, with foot inversion and head tilt to the contra lateral side and tendon snapping. We propose that eccentric muscle action over time can be the basis for a low grade inflammatory condition. The general implications of this model and its relations to Zn and Se will be discussed.

Posturographic testing and motor learning predictability in gymnasts

PURPOSE

One aim of this study was to find if there was a difference between balance and stability between elite level gymnasts and non-gymnasts. Another aim was to find if there was a relationship between dynamic posturographic scores associated with sway fatigue or adaptability and the ability to learn new gymnastic routines. The ultimate aim of the study was to improve gymnastic performance while reducing the probability of injury.

METHODS

Computer dynamic posturography (CDP) provided stability scores, fatigability ratios and adaptation ratios in elite level gymnasts and non-gymnasts controls. Relationships between the postural integrity of gymnasts and non-gymnasts were calculated. The gymnasts were trained in a novel gymnastic routine and performance outcomes were compared to the CDP outcomes.

RESULTS

Tests of postural stability have shown that gymnasts have greater postural stability than non-gymnasts. Gymnasts whose adaptability scores were higher were able to learn and perform new motor routines better than those with lower adaptability scores or high fatigability ratios.

CONCLUSIONS

While gymnasts have greater postural integrity than do non-gymnasts, CDP can identify individuals whose ability to perform new motor activities might be impaired. Methodology to improve functional stability not associated with the motor task may contribute to increased sports performance and decreased probability of injury.

The postural disorientation induced by neck muscle vibration subsides on lightly touching a stationary surface or aiming at it

The aim of this study was to investigate whether the standing body spatial disorientation, induced by neck muscle vibration, and the related post-effects can be suppressed by light finger touch (LFT) of a stationary surface. Continuous (60 s) vibration of dorsal neck or sternocleidomastoid muscle was administered with eyes closed. The center of foot pressure (CFP) displacement, measured by a stabilometric platform, indicated the degree of vibration-induced body tilt. We also investigated whether sensory information from LFT itself was necessary or anticipation of a more secure posture was enough for reducing vibration effects. To this aim, we administered a vibration pulse (5 s) to dorsal neck or sternocleidomastoid muscle and during reaching to the stationary surface. CFP was recorded during both vibration and post-vibration condition and during the aiming task. Neck vibration induced significant CFP displacement in the direction opposite to vibration site. Post-vibration, CFP slowly returned to control values with ample oscillations. LFT during vibration reduced body tilt. LFT was more effective when fingertip contact was in the plane of the greatest tilt. LFT applied during either vibration or post-vibration period reduced post-vibration effects. Reaching toward the stationary surface was enough for reducing vibration-induced body tilt to values close to those observed during actual LFT. The novel conclusions of this study are: 1) LFT is able to relieve the effects of vibration-induced abnormal proprioceptive input from the neck, a segment central to postural control and orientation; 2) LFT during vibration also attenuates vibration post-effects, further suggesting that its action is not merely mechanical; 3) the intention to stabilize the body generates a new postural 'set' sufficient for diminishing body tilt.

Lumbar and cervical erector spinae fatigue elicit compensatory postural responses to assist in maintaining head stability during walking

The purpose of this study was to examine how inducing fatigue of the 1) lumbar erector spinae and 2) cervical erector spinae (CES) muscles affected the ability to maintain head stability during walking. Triaxial accelerometers were attached to the head, upper trunk, and lower trunk to measure accelerations in the vertical, anterior-posterior, and mediolateral directions during walking. Using three accelerometers enabled two adjacent upper body segments to be defined: the neck segment and trunk segment. A transfer function was applied to root mean square acceleration, peak power, and harmonic data derived from spectral analysis of accelerations to quantify segmental gain. The structure of upper body accelerations were examined using measures of signal regularity and smoothness. The main findings were that head stability was only affected in the anterior-posterior direction, as accelerations of the head were less regular following CES fatigue. Furthermore, following CES fatigue, the central nervous system altered the attenuation properties of the trunk segment in the anterior-posterior direction, presumably to enhance head stability. Following lumbar erector spinae fatigue, the trunk segment had greater gain and increased regularity and smoothness of accelerations in the mediolateral direction. Overall, the results of this study suggest that erector spinae fatigue differentially altered segmental attenuation during walking, according to the level of the upper body that was fatigued and the direction that oscillations were attenuated. A compensatory postural response was not only elicited in the sagittal plane, where greater segmental attenuation occurred, but also in the frontal plane, where greater segmental gain occurred.

Effect of fatigue on the precision of a whole-body pointing task

We addressed the issue of the possible degradation of the aiming precision of a whole-body pointing task, when movement coordination is deranged by selective fatigue of the postural task component. The protocol involved continuous repetition (0.1 Hz frequency) of rapid whole-body pointing trials toward a target located beyond arm length, starting from stance and requiring knee flexion. Six healthy human subjects repeated the trials until exhaustion. Such repetition led to electromyography signs of fatigue in rectus femoris (active in body lowering and raising), but not in deltoid (prime mover for arm reaching component). Rectus femoris fatigue affected the equilibrium control strategy, since the anteroposterior displacement of the center of foot pressure was reduced during the fatigued compared with the initial trials. Conversely, the precision of the aiming movement was unaffected by the rectus femoris fatigue in spite of changes in finger trajectory. Trunk inclination at the end of whole-body pointing task and hip and shoulder marker trajectories were unaffected by rectus femoris fatigue. Control experiments were made, whereby fatiguing repetitions of the postural component of the task were performed without finger pointing, except in the first and last five complete whole-body pointing trials. The results were not different from those of the main protocol, except for a transient change in finger trajectory in the very first trial after fatigue. The CNS takes into account the state of postural muscles' fatigue and the concurrently ensuing equilibrium constraints in order to appropriately modify whole-body pointing strategy and keep pointing precision at the target.