As exercise habits before the start of the exercise class did not significantly differ between the non-LS and LS groups (p = 0.9176; Table 2), the difference found in the amount of physical activity in this study was considered to be the result of the effort of each participant in aiming to achieve the target number of steps presented at the beginning of the study. In this study, increased cognitive function during the 13-week study period was associated with higher average physical activity in the LS population, and the ROC analysis showed a threshold of 2.29 Ex. On the hand, no significant relationship was found between physical activity and cognitive function in the non-LS population. When the LS population was classified into < 2.29 and ≥ 2.29 Ex groups, a significant decrease in Locomo 25 scores and a significant increase in ACE-R scores were observed in the ≥ 2.29 Ex group. From these results, it is considered that ≥ 2.29 Ex was effective in improving LS and restoring cognitive function in the LS population. As 2.29 Ex is extremely light exercise and a large amount of time spent in sedentary is associated with low cognitive function , it is expected that the time spent in sedimentary is strongly involved in cognitive decline in the LS.
Exercise has been shown to be effective for all of three strategies for preventing dementia: 1) increase cognitive reserve; 2) reduce brain damage; and 3) reduce neuroinflammation. There have been many reports on the relationship between exercise/physical activity and events related to cognitive function . Clinical studies have reported a correlation between low levels of motor function and high amyloid β deposition . Cohort studies have reported that a high level of physical activity reduces the risk of cognitive decline and Alzheimer’s disease (AD) [24, 25, 26].
Exercise promotes the production of vascular endothelial growth factor and insulin-like growth factor-1 in skeletal muscle, and enhances cerebrovascular plasticity and neuroplasticity . Exercise has also been reported to increase the production of neuroprotective brain-derived neurotrophic factor in skeletal muscle  and kynurenine aminotransferase, and to reduce kynurenine-induced neurotoxicity . Thus, myokines secreted from skeletal muscle act on the brain and mediate the enhancement of cognitive reserve through exercise. However, no relationship has been found between physical activity levels and amyloid-β image level or the cerebrospinal fluid biomarker for AD [30, 31]. Thus, there are two aspects of a high level of physical activity: one suppresses or delays the development of AD pathology, and the other increases other cognitive functions independently of AD pathology, i.e., it compensates for impaired cognitive function and promotes high brain plasticity . It is speculated that these mechanisms are involved in the relationship between physical activity and cognitive function identified in this study.
The effect of Ex on changes in Locomo 25 scores was observed when using repeated-measures ANCOVA adjusted for gender. This result suggested that 2.29 or more physical activity had the effect of reducing the level of LS. Locomo 25 mainly includes questions about the degrees of physical pain and daily activities. According to a recent survey by the Ministry of Health, Labour and Welfare of Japan , chronic pain in the locomotive organs is severe, and usually at sites necessary for movement, such as the hip and lower limb joints, so pain is strongly associated with LS. As with various types of exercise-induced analgesia during and after exercise, such as aerobic, resistance, and isometric exercise [34, 35], exercise has also been reported effective for chronic low back pain associated with LS . It has also recently been reported that active middle-aged and older persons are more resistant to pain , and that exercise interventions for osteoarthritis improve ADL . Based on the above, it was considered that the decrease in Locomo 25 scores in ≥ 2.29 Ex group with LS was due to an increase in physical activity, a decrease in pain, and an increase in the ability to carry out ADL.
Moderate to severe persistent pain, which reflects chronic pain, has been reported to be associated with accelerated cognitive decline and increased dementia onset in the aged . This report supports the relationship between decreased LS scores and increased cognitive function in the present study.
According to the Ministry of Health, Labour and Welfare’s “Physical Activity Standards for Health Promotion 2013” , a physical activity level of 10 Ex/week should be maintained regardless of strength. However, the results of the present study suggest that a physical activity level of ≥ 16 Ex/week is needed to improve cognitive function; 10 Ex/week had no effect on improving cognitive function in people with LS.
In the present study, a significant increase was observed in the memory score domain of the ACE-R in the group with 2.29 or more physical activity in the LS population. It has been reported that moderate physical activity is positively correlated with hippocampal capacity, as is physical activity and memory . It has also been reported that smaller hippocampal volume in the healthy aged is associated with severe acute and chronic pain . Furthermore, it has been reported that persistent pain in a longitudinal cohort of older people is associated with decreased memory and an increased likelihood of dementia . The results of the present suggest that the LS population may have increased memory owing to increased physical activity and pain relief.
In this study, no relationship was found between physical activity and cognitive function the non-LS population. In this population, factors other than physical activity may be involved in the recovery of cognitive function. In this study, Locomo 25 scores were therefore used as an index for lifestyle interventions to improve cognitive function.
This study did have several limitations. First, the number of study participants (n = 70) was small. The criteria for LS in terms of Locomo 25 scores have two levels: ≥ 7 points and ≥ 16 points. However, in this study, few people in the target population had a Locomo 25 score of ≥ 16 points, so a score of ≥ 7 was considered to indicate LS. In the future, exercise intervention times can be expected to be identified more accurately by conducting surveys on more participants and categorizing them into more severe and milder groups in the LS population. In addition, since this study involved only Japanese participants, caution should be taken when generalizing the results to other populations.