Physical activity, muscle mass and physical function in older adults

Ageing is accompanied by a decline in physical function, including loss of muscle mass and muscle strength, which leads to impaired ability to perform activities of daily living and loss of independence. Physical activity (PA) is currently viewed as a key lifestyle factor with potential to mitigate these age-related deteriorations. Therefore, public health organizations have issued guidelines about amounts and types of physical activity for health benefits, where reductions in daily time spent sedentary in favour of more time in aerobic-type moderate-to-vigorous PA (MVPA) are emphasized. In addition, regular engagement in musclestrengthening activities (MSA) are recommended to promote maintenance of muscle mass and strength in ageing populations. However, to what extent different amounts and types of PA impact on different indicators of physical function, including muscle mass and strength, remains currently unclear. Therefore, the overall aim of this thesis was to investigate the impact of PA behaviours on muscle mass and physical function in older adults. In study I, it was shown that regular engagement in exercise activities during middle age was associated with a significantly higher muscle mass and a better cardiorespiratory fitness at old age. In study II, replacement of daily sedentary time with PA of at least light intensity was associated with a significantly lower sarcopenia risk in older adults, with greater benefits above the moderate PA intensity. Study III revealed that engagement in MSA at least twice a week was linked to a significantly lower sarcopenia risk in older adults who already perform at least 150 weekly minutes of MVPA. Finally, study IV showed that older adults who accumulate at least 300 weekly minutes of MVPA have a significantly better overall physical function than those who accumulate at least 150 but less than 300 minutes of MVPA per week. Overall, the findings from this thesis highlight the importance of adherence to the aerobic-type MVPA guideline alongside recommended engagement in MSA for mitigating age-related decline in physical function in older adults. Notably, accumulation of MVPA time beyond the minimum recommended amount provides additional functional benefits