Discussion
involuntary movements, deterioration of motor capabilities, fatigue, pain
RECRUITMENT, TOTALLY BLIND
This study aimed to evaluate the effectiveness of a VR treatment combined with specific PE compared to placebo VR treatment combined with PE in improving functionality, tone and stiffness, and pain in pre-frail and frail elderly people. It was based on the hypothesis that VR therapy could potentiate the effects of conventional exercise in a pre-frail and frail population, even when failing to reach the minimum exercise capacity threshold as per WHO recommendations because of their fatigue (assessed with the Borg Rating of Perceived Exertion). Therefore, this is the first study to provide the scientific community with an understanding on how the mechanisms of neuroplasticity and specifically mirror neurons can influence the effect of the physical training on functionality in frail and pre-frail elderly people.For this reason, functionality, and muscle tone and stiffness were assessed since the expected improvement in physical condition could imply an improvement in certain physical capacities and muscle tone. Specifically, this study assessed aerobic capacity with 2MWT; functional lower-limb strength with 5XSTS test; static balance, gait performance and velocity, standing-up power, sitting-to-standing and standing-to-sitting times, and reaction time with inertial sensors (FallSkip tool); and tone and stiffness with Myoton. All these outcomes become important in pre-frail and frail elderly people during activities of daily living [In general, people from the CI group failed to achieve significant functional improvements. This lack of significant improvements using only a PE programme could be due to the fact that the latter was adapted to their level of fatigue, taking into consideration their frailty state, as explained at the methods section.Nevertheless, when mirror neuron-based therapy was applied in the EI group, an overall improvement in voluntary movement-related capacities was achieved (i.e., aerobic capacity, functional lower-limb strength, and reaction time), with the exception of gait performance and velocity, standing-up power, and sitting-to-standing and standing-to-sitting times. Further, capacities associated with involuntary movements (i.e., static balance, and muscle tone and stiffness) remained similar between assessments in both groups.As reported in previous studies, mirror neuron system-based therapies could help to reduce the deterioration of motor capabilities by evoking a greater neural activation of the cortical-subcortical network that supervises motor control [Regarding involuntary movements, specifically those registered during the static balance phase, no significant differences were found between assessments in either group (i.e., ML displacement, AP displacement, displacement area). This was probably because balancing requires rapid and accurate involuntary movements responding to visual, vestibular, and proprioceptive information [With regard to tone (i.e. natural oscillation frequency) and stiffness, no significant differences were found after the interventions. We decided to include the analysis of the impact of physical intervention on muscle tone, since physical exercise has been considered important for muscle elasticity [Different peripheral and central mechanisms are associated with tone changes [Regarding pain outcome, previous studies have shown promising results for the treatment of pain using movement imagery [This study has some limitations. Firstly, because of the nature of therapy, it was difficult to totally blind therapists and participants. Secondly, the sample has a greater representation of women than men, therefore, this must be taken into account for the generalisation of results. Finally, purposive sampling for the recruitment of the volunteers was used instead of simple randomisation.