High-frequency mechanical strain seems to stimulate bone strength in animals. In this randomized controlled trial, hip BMD was measured in postmenopausal women after a 24-week whole body vibration (WBV) training program. Vibration training significantly increased BMD of the hip. These findings suggest that WBV training might be useful in the prevention of osteoporosis.Introduction: High-frequency mechanical strain has been shown to stimulate bone strength in different animal models. However, the effects of vibration exercise on the human skeleton have rarely been studied. Particularly in postmenopausal women-who are most at risk of developing osteoporosis-randomized controlled data on the safety and efficacy of vibration loading are lacking. The aim of this randomized controlled trial was to assess the musculoskeletal effects of high-frequency loading by means of whole body vibration (WBV) in postmenopausal women. Materials and Methods: Seventy volunteers (age, 58 -74 years) were randomly assigned to a whole body vibration training group (WBV, n ϭ 25), a resistance training group (RES, n ϭ 22), or a control group (CON, n ϭ 23). The WBV group and the RES group trained three times weekly for 24 weeks. The WBV group performed static and dynamic knee-extensor exercises on a vibration platform (35-40 Hz, 2.28 -5.09g), which mechanically loaded the bone and evoked reflexive muscle contractions. The RES group trained knee extensors by dynamic leg press and leg extension exercises, increasing from low (20 RM) to high (8 RM) resistance. The CON group did not participate in any training. Hip bone density was measured using DXA at baseline and after the 6-month intervention. Isometric and dynamic strength were measured by means of a motor-driven dynamometer. Data were analyzed by means of repeated measures ANOVA. Results: No vibration-related side effects were observed. Vibration training improved isometric and dynamic muscle strength (ϩ15% and ϩ 16%, respectively; p Ͻ 0.01) and also significantly increased BMD of the hip (ϩ0.93%, p Ͻ 0.05). No changes in hip BMD were observed in women participating in resistance training or age-matched controls (Ϫ0.60% and Ϫ0.62%, respectively; not significant). Serum markers of bone turnover did not change in any of the groups. Conclusion: These findings suggest that WBV training may be a feasible and effective way to modify wellrecognized risk factors for falls and fractures in older women and support the need for further human studies.

Locomotion in vertebrates and invertebrates has a long history in research as the most prominent example of interlimb coordination. However, the evolution towards upright stance and gait has paved the way for a bewildering variety of functions in which the upper limbs interact with each other in a context-specific manner. The neural basis of these bimanual interactions has been investigated in recent years on different scales, ranging from the single-cell level to the analysis of neuronal assemblies. Although the prevailing viewpoint has been to assign bimanual coordination to a single brain locus, more recent evidence points to a distributed network that governs the processes of neural synchronization and desynchronization that underlie the rich variety of coordinated functions. The distributed nature of this network accounts for disruptions of interlimb coordination across various movement disorders.

Functional imaging studies have shown that seniors exhibit more elaborate brain activation than younger controls while performing motor tasks. Here, we investigated whether this age-related overactivation reflects compensation or dedifferentiation mechanisms. "Compensation" refers to additional activation that counteracts age-related decline of brain function and supports successful performance, whereas "dedifferentiation" reflects age-related difficulties in recruiting specialized neural mechanisms and is not relevant to task performance. To test these predictions, performance on a complex interlimb coordination task was correlated with brain activation. Findings revealed that coordination resulted in activation of classical motor coordination regions, but also higher-level sensorimotor regions, and frontal regions in the elderly. Interestingly, a positive correlation between activation level in these latter regions and motor performance was observed in the elderly. This performance enhancing additional recruitment is consistent with the compensation hypothesis and characterizes neuroplasticity at the systems level in the aging brain.

Although functional imaging studies have frequently examined age-related changes in neural recruitment during cognitive tasks, much less is known about such changes during motor performance. In the present study, we used functional magnetic resonance imaging to investigate age-related changes in cyclical hand and/or foot movements across different degrees of complexity. Right-handed volunteers (11 young, 10 old) were scanned while performing isolated flexion-extension movements of the right wrist and foot as well as their coordination, according to the "easy" isodirectional and "difficult" nonisodirectional mode. Findings revealed activation of a typical motor network in both age groups, but several additional brain areas were involved in the elderly. Regardless of the performed motor task, the elderly exhibited additional activation in areas involved in sensory processing and integration, such as contralateral anterior insula, frontal operculum, superior temporal gyrus, supramarginal gyrus, secondary somatosensory area, and ipsilateral precuneus. Age-related activation differences during coordination of both segments were additionally observed in areas reflecting increased cognitive monitoring of motor performance, such as the pre-supplementary motor area, pre-dorsal premotor area, rostral cingulate, and prefrontal cortex. In the most complex coordination task, the elderly exhibited additional activation in anterior rostral cingulate and dorsolateral prefrontal cortex, known to be involved in suppression of prepotent response tendencies and inhibitory cognitive control. Overall, these findings are indicative of an age-related shift along the continuum from automatic to more controlled processing of movement. This increased cognitive monitoring of movement refers to enhanced attentional deployment, more pronounced processing of sensory information, and intersensory integration.

Several models propose Motor Imagery, Action Observation, and Movement Execution recruit the same brain regions. There is, however, no quantitative synthesis of the literature that directly compares their respective networks. Here we summarized data from neuroimaging experiments examining Motor Imagery (303 experiments, 4902 participants), Action Observation (595 experiments, 11,032 participants), and related control tasks involving Movement Execution (142 experiments, 2302 participants). Comparisons across these networks showed that Motor Imagery and Action Observation recruited similar premotor-parietal cortical networks. However, while Motor Imagery recruited a similar subcortical network to Movement Execution, Action Observation did not consistently recruit any subcortical areas. These data quantify and amend previous models of the similarities in the networks for Motor Imagery, Action Observation, and Movement Execution, while highlighting key differences in their recruitment of motor cortex, parietal cortex, and subcortical structures.

Patients with low back pain have a less refined position sense than healthy individuals, possibly because of an altered paraspinal muscle spindle afference and central processing of this sensory input. Furthermore, muscle vibration can be an interesting expedient for improving proprioception and enhancing local muscle control.

Behavioural and neurophysiological evidence convincingly establish that the left hemisphere is dominant for motor skills that are carried out with either hand or those that require bimanual coordination. As well as this prioritization, we argue that specialized functions of the right hemisphere are also indispensable for the realization of goal-directed behaviour. As such, lateralization of motor function is a dynamic and multifaceted process that emerges across different timescales and is contingent on task- and performer-related determinants.

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