Purpose: The purpose of this study was to investigate Chinese old adults' different body compositions in response to various levels of physical activity (PA). To the best of our knowledge, this is the first study to demonstrate the dose-response relationship between PA and body composition in old adults.
Methods: 2664 participants older than 60 years (males: n = 984, females: n = 1680) were recruited for this cross-sectional health survey. PA was assessed by the short form of the International Physical Activity Questionnaire (IPAQ), and the body composition was measured by bioelectrical impedance analysis (BIA) instruments. The differences of separate body composition indices (lean body mass, LBM; bone mass, BM; and fat mass, FM) of older participants with different PA levels (below PA recommendation and over PA recommendation) were examined using the one-way analysis of variance (ANOVA). To compare the differences of three body composition indices with six different multiples of PA recommendation (0-1 REC, 1-2 REC, 2-4 REC, 4-6 REC, >6 REC), the one-way ANOVA and Turkey's test was used for the post hoc analysis to identify the upper PA-benefit threshold in different indices of body composition.
Results: The LBM and BM are significantly higher and the FM are significantly lower in old adults performing more PA volume than the WHO recommendation, compared with individuals performing less PA volume than the WHO recommendation. There were significant increases in LBM for males in "1-2 REC", "2-4 REC", and ">6 REC" groups, compared with the "0-1 REC" group; and there were significant increases in BM for males in "1-2 REC", "2-4 REC", compared with the "0-1 REC" group. The best PA volume for LBM and BM in females was the PA volume of "2-4 REC". Additionally, whether males or females, there was no significant difference in FM between the "0-1 REC" group and other separate groups.
Conclusion: The PA volume that causes best benefit for body composition of the elderly occurs at 1 to 2 times the recommended minimum PA for males, while it occurs at 2 to 4 times that recommended for females. No additional harms for old adults' body composition occurs at six or more times the recommended minimum PA.
Keywords: IPAQ; aging; body composition; old adults; physical activity.