4. Discussion
VF, lower extremity muscle strength, age-related deterioration, LEMS, visual, auditory, and somatosensory systems, cognitive and motor tests
This study investigated the effects of a 12-week dual-task physical–cognitive training on gait performance, balance, lower extremity muscle strength, and cognitive performance in a group of cognitively normal older adult women compared to a control group, who participated only in educational activities. Our two assumptions were confirmed. First, we found that DT training was able to generate significant time–group interaction effects after the 12-week intervention on the performance of BB, GP, LEMS, and EFs, except for the VF-category. Second, members of the DT training also reported better results on these same variables at the end of the 12-week follow-up. Thus, our findings were in line with previous investigations that showed concurrent physical–cognitive training as being capable for neutralizing age-related deterioration in physical and cognitive functions [A strength of our study was the training protocol. When it comes to DT training, the type of exercise applied is decisive for the creation of internal interference factors [It is noteworthy that although the performance of the CG members on all outcome variables (T2 and T3 assessments) was lower than the results of the DT group, except for BB, their performance levels were adequate for an age group between 60 and 79 years. In our study, while DT group members indicated an improvement in gait performance in a single task, motor dual task, and cognitive dual task, CG participants maintained gait speed in the three different conditions unchanged. Walking is a complex task that requires a mutual work of the sensorial and cognitive systems [In this study, the benefits of DT training became more evident after the follow-up period, when lasting effects (retention gains: Δ = T3 − T1) were revealed. Thus, members of the DT group indicated in the gait condition a single task (gain of 23.3%), motor dual task (gain of 20.9%), and cognitive dual task (gain of 12.2%). Similar results of DT training in GP among older adults have also been reported in previous experimental studies [In the present study, the greatest power effect revealed by DT training was observed in the BB test. The improvement in balance control can be attributed to the set of tasks experienced by the older adults in the DT group, which improved the functioning of the sensory system organs responsible for regulating postural control (i.e., visual, auditory, and somatosensory systems). Thus, over 24 weeks, while the CG members maintained their balance performance unchanged, those who participated in the DT training increased the efficiency of this motor skill by up to 300.0% from T1 to T2, and were able to retain the gains (Δ = T3 − T1) by up to 200% after follow-up. Our findings are in line with previous studies [The improvement in the BB performance was in agreement with a previous review study [Another positive effect of DT training was for LEMS. With aging, there is a gradual loss of related muscle strength that can compromise performance in ADLs, even reducing perceived quality of life [Regarding cognition—more specifically, a subcomponent of executive functions, which is verbal fluency—we found that, except for the VF category, while the cognitive performance of the CG members remained unchanged over 24 weeks, the members of the DT training indicated improvement in the performance of phonemic fluency and semantic memory functions. The effective gain can be verified after follow-up through retention effects (Δ = T3 − T1) of up to 26.6%, 176.7%, and 116.6%, respectively, in the categories VF-total, VF-category, and VF-grouping. The literature has highlighted the benefits of physical exercise under the principles of DT to increase the cognitive reserve of the older adult population [It is worth noting that, based on the MMSE test, all of our study population had a preserved cognitive state. Therefore, they experienced natural aging [The present study has some limitations. First, findings from the present study can only be generalized to a specific group of older adult women, and only for those who meet the same selection criteria adopted in this investigation. Second, considering that the cognitive and motor tests were applied three times over a period of six months, it is possible that some participants memorized the tasks, generating bias in the results. Third, neuroimaging techniques were not added to further monitor the neural changes caused by DT training. Thus, it must be considered that it is possible that the clinical instruments used did not offer an in-depth analysis of the underlying brain mechanisms that benefited from DT training. Fourth, the levels of complexity, specificity, and prioritization of the motor and cognitive task limit the comparability with previous studies. Thus, the effect sizes generated by our physical–cognitive DT training protocol may vary considerably from those presented by other studies. Fifth, the use of only one cognitive test is a limitation of this investigation. Therefore, it is suggested that future studies, in addition to the verbal fluency test, add other instruments to verify the effects of physical–cognitive DT training on executive functions. The measure can broaden the understanding of the underlying mechanisms of neural plasticity generated by this type of training. Finally, it is encouraged to carry out a longitudinal follow-up of the evaluated population in order to state more precisely the effects of DT training and natural aging on GP, BB, LEMS, and EFs.