No abstract

Age-related deterioration of postural control resulted in slower reactive responses and reduced control of the direction of body movement during voluntary sway and orthogonal transitions. Slower postural reaction and movement time and reduced medial-lateral control of the centre of mass during voluntary sway movements are associated with increased fall-risk in community-living older people.

The slower and less effective balance responses of multiple fallers compared with nonfallers and the comparable sensitivity and specificity of PPA score and reactive voluntary sway measures indicate that postural reaction time is a strong determinant of falls risk.

During maximal effort contractions, intense serotonin release via the raphe-spinal pathway spills over from the somato-dendritic compartment to activate inhibitory 5-HT 1A receptors on the axon initial segment of motoneurons to reduce motoneuronal output.r We investigated whether the same mechanism of central fatigue is present for low-intensity contractions, whereby weak serotonergic drive over an extended period may cause accumulation of serotonin and exacerbate central fatigue.r Enhanced availability of serotonin did not directly influence motor pathways or motor performance during prolonged submaximal contraction.r However, perceptions of muscle fatigue were greater, and the fatigue-induced lengthening of the silent period elicited via motor cortical stimulation was reduced with enhanced availability of serotonin.r We propose that sustained low-intensity serotonergic neurotransmission influences supraspinal processes associated with fatigue, without directly influencing the output of the motor system during submaximal exercise.