Long-term participation in community-based group resistance exercises delays the transition from robustness to frailty in older adults: a retrospective cohort study

BACKGROUND: How community-based group resistance exercises affect the transition from robustness to frailty remains unclear. Thus, we conducted a retrospective cohort study to determine whether the trajectory from robustness to frailty over age differed depending on the duration of participation in group exercises. METHODS: We analyzed the Kihon Checklist (KCL) score of community-dwelling elderly residents of Sumoto city, Hyogo prefecture, who participated in community-based group resistance exercises between April 2010 and December 2019. Finally, 2567 older individuals were analyzed using multilevel modeling. The explanatory variables of interest were the frailty score measured using the KCL for each individual, where 0–3, 4–7, and ≥8 points denoted robustness, pre-frailty, and frailty, respectively. We considered age, sex, systolic blood pressure, pulse, duration of participation, and change in KCL score from baseline as possible confounders. Participants were classified as follows based on the duration of participation in the exercises: <3 times, short-term participation group; 4–6 times; mid-term participation group; and 7–13 times, long-term participation group. The mean duration from the baseline physical test for the total sample was 2.35 years (SD=2.51). RESULTS: The participants’ mean total KCL score at baseline was 4.9±3.7. Multilevel modeling analysis revealed that the KCL scores changed by 0.82 points for each additional year of age (p<0.001) and changed by − 0.93 points for long-term participate group (p<0.001). The Estimated Marginal Means (EMM) of the KCL score was 3.98 (95%CI: 3.69, 4.28) points in the short-term participation group and was significantly worse than that of the long-term participation group at 70 years of age (p=0.001). The EMM was 4.49 (95%CI: 4.24, 4.74) at 75 years of age in the mid-term participation group and was significantly worse than that of the long-term participation group. The EMM was 3.87 (95%CI: 3.57, 4.16) in the long-term participation group and significantly better than that of the short-term (p<0.001) and mid-term (p=0.002) participation groups. CONCLUSION: Participation in community-based group resistance exercises prolongs the transition from robustness to frailty. The improved KCL scores at baseline in the long-term participation group remained in the robust range at 75 years of age, which suggests the importance of initiating participation before the onset of functional decline. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12199-021-01028-x.