Age and gender, two key factors in the associations between physical activity and strength during the ageing process
Objectives The aims of this study were to identify if the associations of physical activity (PA) and muscle strength may vary throughout the ageing process; to study the differences among genders in the relationships between PA and strength in elderly people and to test whether these differences are explained by the hormonal, nutritional and inflammatory status. Study design A total of 1741 people ≥65 years of age participated in this cross-sectional study. Main outcome measures Upper- and lower-limbs maximal voluntary isometric strength was obtained using standardized techniques and equipment. PA was recorded by a validated questionnaire. The associations of PA with strength were assessed using generalized linear regression models with a Gamma-distributed dependent variable. Results A significant gender by PA interaction was found for all strength-related variables (all P < 0.01). Moreover, when sexual hormones, albumin or C-Reactive protein were taken into account in the model, the results did not significantly change. In women, PA was positively associated with upper and lower-body strength; however in men, PA was only associated with grip and knee strength (both P < 0.01). Higher strength values were associated with higher levels of PA, especially in women. However, this tendency had a different pattern across the age range, showing a stronger association in the ‘young’ elderly compared with the ‘old’ elderly. Conclusion Higher levels of PA are related to greater muscle strength, especially in women and those who were younger.