Differential decline of physical fitness with age according to Body Mass Index levels.

Background: The main objective of this study was to assess the association between age and physical fitness and motor fitness components according to BMI levels, in men and women separately, and to test if this association is different between BMI levels.

Methods: This cross-sectional study was based on a pre-existing database from the DiagnoHealth battery, a French series of physical fitness and motor fitness tests designed by the Institut des Rencontres de la Forme (IRFO; Wattignies, France). Analyses were perfomed on 6830 women (65.8%) and 3356 men (34.2%) aged from 50 to 80 years. In this French series several physical fitness and motor fitness components were measured: cardiorespiratory fitness (CRF), speed, upper muscular endurance, lower muscular endurance, lower body muscular strengh, agility, balance, and flexibility. From the results of these tests, a specific score named Quotient of Physical Condition was calculated. Associations between age and physical fitness and motor fitness components according to BMI levels were modelized using linear regression for quantitative components, and ordinal logistic regression for ordinal components. Analyses were performed separately for women and men.

Results: A significant association of age with physical fitness and motor fitness performance in each BMI levels were observed in women except for lower muscular endurance, muscular strength and flexibility in obese women. A significant association of age with physical fitness and motor fitness performance in each BMI levels were observed in men except for upper/lower muscular endurance and flexibility in obese men.

Conclusions: The present results shown that most of physical fitness and motor fitness decrease with age in women and men. Lower muscular endurance, muscular strength and flexibility did not change in obese women, thereas upper/lower muscular endurance and flexibility did not change in obese men. This finding is particularly revelant for guiding prevention strategies for maintaining physical fitness and motor fitness performance, which is one of the most important component of healthy aging and wellbeing.