## 4 Discussion
Based on TDMS (Figure 3), Pilates positively changed the mood of late-stage seniors, possibly due to ease of engagement, conditioning of the mind (i.e., breathing, control and concentration), and a sense of participation in a group activity [19; 20]. While effectiveness is essentially required for intervention strategies to enhance the health of senior late-stage adults, it is arguably more important that they continue as a routine activity. For safety, the current study limited intervention to 30 min per session and eight sessions over eight weeks in total. As no dropouts were observed, increased volume (frequency and duration) of Pilates exercise is recommended for future studies. Executive functions measured by TMT-A, for example, showed remarkable improvements but did not reach statistical significance. With the extended Pilates program, cognitive functions may possibly be enhanced. The current study was unique and important in investigating late-stage frail adults (>75 years) with locomotive and cognitive impairments, but there are some fundamental limitations to acknowledge. First, the sample size was small due to difficulty in recruiting frail late-stage adults. For conclusive evidence in every aspect of the current study, a larger sample size needed to be tested. Biomechanical assessment also required special adaptations for the frail participants to minimize the time taken in testing. More comprehensive marker setups, however, particularly whole-body modeling, allowed for a better understanding of their movement functions. Gait testing was conducted on the treadmill at a constant 0.3 km/h across all participants. In the pilot stage of experimental design, frail late-stage adults struggled with maintaining consistent walking patterns. Treadmill walking was, therefore, selected to provide a constant belt speed as the external pacemaker. Controversy, however, still exists in treadmill gait testing, especially for older adults [40]. For a sustainable aging society, reversibility of frailty among senior adults is an important topic in addition to prevention and conventional medical practice [9; 10]. In the case of Japan, locomotive and cognitive functions are considered the main determinants to maintain independent lifestyles [24]. Healthcare science is, therefore, expected to quantify these abilities and systematically evaluate seniors' health, which, in turn, helps to select effective intervention strategies. While Pilates can be applied in seniors and other vulnerable populations, there are a few fundamental challenges to mass utilization. First of all, it is necessary to establish a method that can be operated by practitioners after the systematic learning process. It cannot be a complete approach if Pilates effects excessively depend on each practitioner's skills. This issue can be overcome by establishing legitimate training programs and qualifications [43], but, currently, there are many random and unofficial certificates that can be obtained by attending seminars for a few days. There might be certain benefits with such short and intensive courses, but it may take years of practice before Pilates exercise can be prescribed for vulnerable populations, including late-stage adults. Further research efforts are thus essential, but the current study revealed the potential benefit of Pilates intervention for late-stage frail adults. Previous studies [35; 44] supported Pilates intervention for falls prevention among older adults based on simple assessments (e.g., timed up and go). This study employed biomechanical research methods, and found a reduced risk of tripping due to improved swing foot clearance at MFC and greater dynamic balance against slipping-related balance loss. In the future, Pilates programs should focus on fine-movement control and core training for fall-prevention purposes. Furthermore, Pilates sessions enhanced the participants' mood, probably due to engagement in the exercise program. It is expected that future studies be undertaken to investigate the benefits in various population groups.