The results of the present study revealed that listening to music, mainly Mozart’s symphony, has significant positive large main effects on both static, under sensory manipulation, (67% of the variance), and dynamic balance in middle-aged women. Although beneficial effects of auditory stimulation with music on postural performance have been evidenced in different populations, to the best of our knowledge, there is still a paucity of data on this topic in healthy middle-aged women. Yet, previous investigations in line with our findings have been found in other populations (i.e. healthy subjects (24, 25) young (26) and older adults (27), and patients (28, 29, 41)). It has been hypothesize that balance improvements following listing to music could be explained by the interaction between the auditory and equilibrium systems in the peripheral receptors of the inner ear as well as in the CNS (42, 43). Along with vestibular system activation, music has been revealed to stimulate the lateral pre-motor and supplementary motor areas (23) which may, in turn, enhance the muscular output of the postural balance system. Another factor may explain the balance improvement is the affective arousal aspect of music, which is likely to influence both motivational and emotional processing. The activation of the emotional neural-based network that involves the dopaminergic mesolimbic projections to the ventral striatum-intraccumbens nuclei, is believed to regulate motivational-incentive reinforcements of general behavior (21, 44). Thus, improvements in both static and dynamic balance in response to music listening could be explained by the emotional reactions that instantly activate the cortical-basal ganglia motor loop. Behavioral evidence for a functional interface between the limbic and motor systems (45) and the anatomical-functional sensorimotor integration of basal ganglia and cortical frontal regions (46, 47) further support this explanation.
Besides, in line with previous investigations, we revealed significant differences between the EO and EC conditions for all postural conditions, whatever the auditory condition was (48, 49). Surprisingly, postural balance continued to significantly increase in the EC when feedback was provided through listening to Mozart music (Table 1). However, these results indicates that independent of auditory inputs, no interaction between the visual and auditory systems was found.
Unlike our findings, a previous study showed that different types of music such as classical, pop and rock had no effects on either static or dynamic balance in healthy adults (26). The stochastic resonance” phenomenon may explain these controversial results. Indeed, Ross and Balasubramaniam hypothesized that the reduction of postural sways in response to auditory stimuli could be explained by the stochastic resonance phenomenon (50). Such phenomenon occurs when a sensory signal containing information is subthreshold which means too weak to be detected and integrated by the CNS.
Importantly, when standing on an unstable surface (foam surface), our results showed that listing to Mozart’s symphony enhanced postural balance only in the EC condition (where the visual inputs were deprived). In accordance, when auditory input was provided, Dozza et al. (2007) found greatest improvement in the subjects’ ability to maintain balance in the foam surface condition (51). These researchers suggested that when standing on a foam surface and received limited visual and somatosensory inputs, subjects benefited most from audio-biofeedback. In fact, the CNS integrates and processes information from the vestibular, visual and somatosensory systems in order to regulate postural stability.
Furthermore, it is well known that standing quietly requires cognitive processing and that the more difficult the postural task is, the more cognitive processing is needed (52). In combination, it has been revealed that music boosts cognitive functions by activating the brain areas that are mainly connected with emotional processing and higher cognitive process such as the limbic system and frontal lobes respectively (53, 54). Therefore, the postural balance enhancement found in our results in such challenging condition (foam surface/EC) may be explained by music benefits on cognitive processing.
Overall, our findings suggested that listening to music, particularly Mozart’ symphony, could be an alternative for both static and dynamic balance improvements in middle-aged women. Postural balance is crucial for daily life activities. Improving it induces significant better functional mobility, coordination (55, 56) and autonomy. Furthermore, postural balance improvement in response to music listening may reduce the risk and fear of falls as well as the falling incidence. This would, in turn, make a meaningful impact on the quality of life of middle-aged women, since not only falls but also the fear of falling may affect psychological and social behavior (57).
The study has some limits that should be addressed by future investigators. First, since we have suggested a mood and cognitive aspect may explain the postural balance improvements, future investigators may explore the music effect on the mood status and cognitive performance to confirm our hypothesize. Besides, future evaluation of long-term effects of music-listening would be of interest, since some long-term gains may be more likely to found.