To prevent the onset and progression of frailty syndrome, multi-factorial exercise programs can be effective, including resistance exercise, balance training, and functional training health in older adults who live in the community. In addition, fall-rate reduction has been reported through a combination of balance exercise, functional exercise, and resistance exercise [5] [6]. In addition to multi-factorial exercise, intensified training with trainers [7] or multi-professional teams [8] could lead to optimal effects.
Although AWs are used in gymnastics classes for older adults in some areas of Japan, there are various risks involved, and no guidelines currently exist for safe personal use by older individuals.
AWs have been found to have a beneficial effect on gait factors when properly used by healthy adults[
9]. However, the effects of simple programs, including resistance training to prevent falls, dance and walking, are unknown [
10].
Because we targeted older people living in the community, there was a relatively low change of falling, and our outcomes were focused on frailty prevention, particularly muscle strengthening effects.
The effectiveness of measures to improve locomotor function among older people has been reported using elastic bands [11], iron arrays [12], and machine-based muscle strengthening exercises [13].
In an intervention using AWs in healthy older women, performing muscle strengthening of the lower limbs using an elastic band and AWs three times a week for 12 weeks, including an instruction session once a week, resulted in a significant improvement in isometric knee extension muscle strength, isometric elbow flexion muscle strength, grip force, and weight ratio leg extension power, but no improvement in movement ability, such as standing up and stepping up/down [14].
The recent prevalence of the COVID-19 pandemic has led to a decrease in exercise classes with instructors.
In future, the utilization of internet technology including video, remote instruction and virtual reality may be important as effective substitutes for face-to-face classes with a trainer [7] or multi-professional team [8]. Thus, it is important to investigate safe and sustainable exercise environments at home. The current study produced primary data verifying the effect of AWs as a wearable muscle load device. We sought to contribute to the development of environments in which exercise can be safely continued at home with AWs. However, depending on the method employed, this approach could cause health problems, and some products warn against use by older adults alone. There is currently no specified safe environment for older adults to voluntarily incorporate AWs as a frailty prevention measure.
In the current study, we implemented a 3-month intervention with minimum requirements of use during the intervention period.
Data regarding usage frequency and pre-falling incidents, obtained from sensors attached to AWs or self-recording, were not connected to individual anthropometry and performance data.
Thus, the current study is considered an interim report in a larger project. There were no serious accidents or incidents during the study period, and the AW intervention induced significant increases in lower limb circumference and CS-30 performance in older subjects, verifying the beneficial effects of the AW intervention on strengthening lower limb muscle.
Compared with other intervention studies [14] [15], the focus of the current study was not strict, and the sample size was not sufficient.
Nevertheless, the lower leg circumference of older participants and CS-30 performance in both groups exhibited a significant improvement.
A previous study reported that the CS-30 is a highly reproducible test that is significantly correlated with leg extension muscle strength, and can be used to evaluate lower extremity muscle strength among people aged 60 years and over living in the community [4]. Figure 2 shows that, although there was no overall improvement, there was an average trend toward improvement, and it is possible that differences in individual effort are reflected in the measured values after the intervention. No improvement was observed in other performance items. In TUG, some studies have reported positive effects [16] while other studies have reported negative effects [17]. In future studies, it would be useful to collate each individual’s sensor data and activity diary with these measurement data.
Although no significant differences were observed in bilateral lower limbs, trunk muscle mass (Table 2), or tongue pressure (Table 3), future studies should conduct trials with a longer intervention period and more participants. The sway of the center of gravity also integrates complex functions, such as deep sensation and the extrapyramidal tract, and improvement is not only exhibited by improvement of lower limb strength. Previous studies have reported that gravity changes are not directly affected by muscle strength [18] [19] [17] [20].
Considering the attachment site of AWs, the load would be expected to particularly affect the swing motion of the lower limbs and the flexion motion of the hip joint during walking motion. These movements tend to be weakened with aging, and if additional stress can be selectively applied to these movements, it could not only serve as an exercise load but also suppress the deterioration of walking function among older people. It is also possible that this method could be applied as a high-quality exercise therapy.
Because the study regime was not strict, various factors may have affected individual effort.
Furthermore, it was difficult to control for confounding factors, such as the effects of participating in regular individual exercise classes and sports activity, such as yoga and personal gym use.
Currently, while staying at home to contain the COVID-19 pandemic, inactivity among older people has become a serious problem. Frailty prevention approaches are moving toward self-restraint and outdoor activities that avoid close contact. Outdoor activities such as walking while avoiding contact with others are preferred options for strengthening physical fitness. Walking has been widely adopted for physical strengthening. However, although walking may have an effect on improving cardiopulmonary function, it has been reported to have little effect on muscle strengthening and fall prevention [21]. However, incorporation of walking combined with wearing AWs has the potential to be effective for lower limb muscle strengthening. In the case of older adults, however, because there is a large difference in individual abilities, it is necessary to propose measures that are suitable for each individual’s physical characteristics, muscle mass, muscle strength, and exercise abilities. To provide feedback, a system for formulating a menu that suits each individual according to guidelines for proper use would be useful.
Finally, one participant remarked that taking part in the study motivated them to exercise, and to walk.
This comment suggests the importance of fostering and maintaining motivation in healthy older adults.
The present study involved several limitations. First, it is difficult to conduct ideal exercise intervention research in older adults’ daily lives. Therefore, various data regarding daily activity and AW-wearing records that we intended to collect were not possible to measure in this study. It would be valuable for future studies to develop a research system that collects and collates these data sources automatically.
We asked participants to select the wearing conditions of AWs according to the appropriate situation for each individual and advised a minimum use requirement of 20 minutes at least once to twice per week.
However, it was difficult for some participants to understand the self-administration conditions.