Lighten Up! Postural Instructions Affect Static and Dynamic Balance in Healthy Older Adults.

BACKGROUND AND OBJECTIVES: Increased fall risk in older adults is associated with declining balance. Previous work showed that brief postural instructions can affect balance control in older adults with Parkinson's disease. Here, we assessed the effects of brief instructions on static and dynamic balance in healthy older adults. RESEARCH DESIGN AND METHODS: Nineteen participants practiced three sets of instructions, then attempted to implement each instructional set during: (1) quiet standing on foam for 30 s with eyes open; (2) a 3-s foot lift. "Light" instructions relied on principles of reducing excess tension while encouraging length. "Effortful" instructions relied on popular concepts of effortful posture correction. "Relax" instructions encouraged minimization of effort. We measured kinematics and muscle activity. RESULTS: During quiet stance, Effortful instructions increased mediolateral jerk and path length. In the foot lift task, Light instructions led to the longest foot-in-air duration and the smallest anteroposterior variability of the center of mass, Relax instructions led to the farthest forward head position, and Effortful instructions led to the highest activity in torso muscles. DISCUSSION AND IMPLICATIONS: Thinking of upright posture as effortless may reduce excessive co-contractions and improve static and dynamic balance, while thinking of upright posture as inherently effortful may make balance worse. This may partly account for the benefits of embodied mindfulness practices such as tai chi and Alexander technique for balance in older adults. Pending larger-scale replication, this discovery may enable physiotherapists and teachers of dance, exercise, and martial arts to improve balance and reduce fall risk in their older students and clients simply by modifying how they talk about posture.

Reductions in co-contraction following neuromuscular re-education in people with knee osteoarthritis.

BACKGROUND: Both increased knee muscle co-contraction and alterations in central pain processing have been suggested to play a role in knee osteoarthritis pain. However, current interventions do not target either of these mechanisms. The Alexander Technique provides neuromuscular re-education and may also influence anticipation of pain. This study therefore sought to investigate the potential clinical effectiveness of the AT intervention in the management of knee osteoarthritis and also to identify a possible mechanism of action. METHODS: A cohort of 21 participants with confirmed knee osteoarthritis were given 20 lessons of instruction in the Alexander Technique. In addition to clinical outcomes EMG data, quantifying knee muscle co-contraction and EEG data, characterising brain activity during anticipation of pain, were collected. All data were compared between baseline and post-intervention time points with a further 15-month clinical follow up. In addition, biomechanical data were collected from a healthy control group and compared with the data from the osteoarthritis subjects. RESULTS: Following AT instruction the mean WOMAC pain score reduced by 56 % from 9.6 to 4.2 (P < 0.01) and this reduction was maintained at 15 month follow up. There was a clear decrease in medial co-contraction at the end of the intervention, towards the levels observed in the healthy control group, both during a pre-contact phase of gait (p < 0.05) and during early stance (p < 0.01). However, no changes in pain-anticipatory brain activity were observed. Interestingly, decreases in WOMAC pain were associated with reductions in medial co-contraction during the pre-contact phase of gait. CONCLUSIONS: This is the first study to investigate the potential effectiveness of an intervention aimed at increasing awareness of muscle behaviour in the clinical management of knee osteoarthritis. These data suggest a complex relationship between muscle contraction, joint loading and pain and support the idea that excessive muscle co-contraction may be a maladaptive response in this patient group. Furthermore, these data provide evidence that, if the activation of certain muscles can be reduced during gait, this may lead to positive long-term clinical outcomes. This finding challenges clinical management models of knee osteoarthritis which focus primarily on muscle strengthening. TRIAL REGISTRATION: ISRCTN74086288 , 4th January 2016, retrospectively registered.

Neuromechanical interference of posture on movement: evidence from Alexander technique teachers rising from a chair.

While Alexander technique (AT) teachers have been reported to stand up by shifting weight gradually as they incline the trunk forward, healthy untrained (HU) adults appear unable to rise in this way. This study examines the hypothesis that HU have difficulty rising smoothly, and that this difficulty relates to reported differences in postural stiffness between groups. A wide range of movement durations (1-8 s) and anteroposterior foot placements were studied under the instruction to rise at a uniform rate. Before seat-off (SO) there were clear and profound performance differences between groups, particularly for slower movements, that could not be explained by strength differences. For each movement duration, HU used approximately twice the forward center-of-mass (CoM) velocity and vertical feet-loading rate as AT. For slow movements, HU violated task instruction by abruptly speeding up and rapidly shifting weight just before SO. In contrast, AT shifted weight gradually while smoothly advancing the CoM, achieving a more anterior CoM at SO. A neuromechanical model revealed a mechanism whereby stiffness affects standing up by exacerbating a conflict between postural and balance constraints. Thus activating leg extensors to take body weight hinders forward CoM progression toward the feet. HU's abrupt weight shift can be explained by reliance on momentum to stretch stiff leg extensors. AT's smooth rises can be explained by heightened dynamic tone control that reduces leg extensor resistance and improves force transmission across the trunk. Our results suggest postural control shapes movement coordination through a dynamic "postural frame" that affects the resistive behavior of the body.

Prolonged weight-shift and altered spinal coordination during sit-to-stand in practitioners of the Alexander Technique.

The Alexander Technique (AT) is used to improve postural and movement coordination and has been reported to be clinically beneficial, however its effect on movement coordination is not well-characterized. In this study we examined the sit-to-stand (STS) movement by comparing coordination (phasing, weight-shift and spinal movement) between AT teachers (n=15) and matched control subjects (n=14). We found AT teachers had a longer weight-shift (p<0.001) and shorter momentum transfer phase (p=0.01), than control subjects. AT teachers also increased vertical foot force monotonically, rather than unweighting the feet prior to seat-off, suggesting they generate less forward momentum with hip flexors. The prolonged weight-shift of AT teachers occurred over a greater range of trunk inclination, such that their weight shifted continuously onto the feet while bringing the body mass forward. Finally, AT teachers had greatly reduced spinal bending during STS (cervical, p<0.001; thoracic, p<0.001; lumbar, p<0.05). We hypothesize that the low hip joint stiffness and adaptive axial postural tone previously reported in AT teachers underlies this novel "continuous" STS strategy by facilitating eccentric contractions during weight-shift.

Method to measure tone of axial and proximal muscle.

The control of tonic muscular activity remains poorly understood. While abnormal tone is commonly assessed clinically by measuring the passive resistance of relaxed limbs, no systems are available to study tonic muscle control in a natural, active state of antigravity support. We have developed a device (Twister) to study tonic regulation of axial and proximal muscles during active postural maintenance (i.e. postural tone). Twister rotates axial body regions relative to each other about the vertical axis during stance, so as to twist the neck, trunk or hip regions. This twisting imposes length changes on axial muscles without changing the body's relationship to gravity. Because Twister does not provide postural support, tone must be regulated to counteract gravitational torques. We quantify this tonic regulation by the restive torque to twisting, which reflects the state of all muscles undergoing length changes, as well as by electromyography of relevant muscles. Because tone is characterized by long-lasting low-level muscle activity, tonic control is studied with slow movements that produce "tonic" changes in muscle length, without evoking fast "phasic" responses. Twister can be reconfigured to study various aspects of muscle tone, such as co-contraction, tonic modulation to postural changes, tonic interactions across body segments, as well as perceptual thresholds to slow axial rotation. Twister can also be used to provide a quantitative measurement of the effects of disease on axial and proximal postural tone and assess the efficacy of intervention.

Multi-segmental torso coordination during the transition from sitting to standing.

BACKGROUND: Research into the multi-segmental mobility of the torso could add to our understanding of the contributions of the head and torso to human movement. The purpose of this study was to determine the motion and temporal coordination of the head and multiple torso segments during the sit-to-stand task. METHODS: Thirty-two young, healthy participants performed five trials of the sit-to-stand movement and 6s of sitting. Range of motion and patterns of peak flexion and extension of six segments and joints and cross correlation of pairs of the six torso segments were analyzed from 3-D kinematic data. FINDINGS: Sagittal range of motion for torso joints during the sit-to-stand task was greater than during sitting trials; motion at the lumbar/pelvis joint was greater than at other torso joints. Peak flexion of torso joints occurred earlier than peak extension. Cross correlations at zero lag and time lags of maximum cross correlations varied such that there was greater temporal coordination of intermediate torso segments compared to pairs including the head and pelvis. There was greater temporal coordination of adjacent segment pairs than for pairs that were less proximal to each other. INTERPRETATION: A high degree of mobility occurs within the torso during the sit-to-stand task. Varying coordination patterns suggest that there are regional differences in movement timing within the torso that may relate to segmental differences in functional roles. Employing multi-segmental torso models may indicate different movement strategies within a healthy population and could highlight differences between clinical populations.

Postural muscle tone in the body axis of healthy humans.

Across the entire human body, postural tone might play its most critical role in the body's axis because the axis joins the four limbs and head into a single functioning unit during complex motor tasks as well as in static postures. Although postural tone is commonly viewed as low-level, tonic motor activity, we hypothesized that postural tone is both tonically and dynamically regulated in the human axis even during quiet stance. Our results describe the vertical distribution of postural muscle tone in the neck, trunk, and hips of standing human adults. Each subject stood blindfolded on a platform that axially rotated the neck, trunk, or pelvis at 1 degrees /s and +/-10 degrees relative to the neutral position (i.e., facing forward). The measured resistance to axial rotation was highest in the trunk and lowest in the neck and was characterized by several nonlinear features including short-range stiffness and hysteresis. In half of the subjects, axial muscle activity was relatively constant during axial rotation, and in the other half, muscle activity was modulated by lengthening and shortening reactions, i.e., decreasing activity in lengthening muscles and increasing activity in shortening muscles, respectively. Axial resistance to rotation was reduced in subjects whose muscle activity was modulated. The results indicate that axial tone is modulated sensitively and dynamically, this control originates, at least in part, from tonic lengthening and shortening reactions, and a similar type of control appears to exist for postural tone in the proximal muscles of the arm.

Improvement in automatic postural coordination following alexander technique lessons in a person with low back pain.

BACKGROUND AND PURPOSE: The relationship between abnormal postural coordination and back pain is unclear. The Alexander Technique (AT) aims to improve postural coordination by using conscious processes to alter automatic postural coordination and ongoing muscular activity, and it has been reported to reduce low back pain. This case report describes the use of the AT with a client with low back pain and the observed changes in automatic postural responses and back pain. CASE DESCRIPTION: The client was a 49-year-old woman with a 25-year history of left-sided, idiopathic, lumbrosacral back pain. Automatic postural coordination was measured using a force plate during horizontal platform translations and one-legged standing. OUTCOMES: The client was tested monthly for 4 months before AT lessons and for 3 months after lessons. Before lessons, she consistently had laterally asymmetric automatic postural responses to translations. After AT lessons, the magnitude and asymmetry of her responses and balance improved and her low back pain decreased. DISCUSSION: Further research is warranted to study whether AT lessons improve low back pain-associated abnormalities in automatic postural coordination and whether improving automatic postural coordination helps to reduce low back pain.