Role of sit-to-stand muscle power in healthy ageing: assessing validity, clinical relevance, decline and interventions in older adults with and without chronic conditions (PhD Academy Award)

Abstract

This PhD thesis aimed: (i) to assess the validity of the sit-to-stand (STS) muscle power test and compare it with other equations available in the literature; (ii) to investigate the functional implications of having low relative STS power (ie, normalised by body mass) in older individuals with and without Parkinson’s disease (PD); (iii) to assess longitudinal changes in relative STS power and its contributing factors, providing clinically relevant cut-off points for low relative STS power; and (iv) to evaluate the short-term and residual effects of power-oriented resistance training (RT) combined with high-intensity interval training (HIIT) in frail older adults and in those with chronic obstructive pulmonary disease (COPD). Muscle power, a critical component of the neuromuscular system, declines more rapidly than muscle mass and strength with ageing and is a stronger predictor of adverse health outcomes, including frailty, disability, and falls. However, the lack of feasible and valid tests, normative values and cut-off points has so far prevented its evaluation in the clinical setting. Given the WHO’s emphasis on healthy ageing and maintaining functional ability, it is essential to identify and implement effective strategies to assess and enhance muscle power, thereby supporting independence and well-being in older populations. Thus, the validity and clinical relevance of the STS muscle power test deserved to be investigated. My PhD thesis comprised eight studies, including cross-sectional (studies 1–4), an 8-year longitudinal (study 5) and interventional (studies 6–8) designs. Participants included 2183 community-dwelling older adults (>65 years), 46 age- and sex-matched individuals with and without PD (>60 years), 59 older adults with frailty (>70 years) and 21 older adults with COPD (>65 years). Relative STS power was evaluated using the STS muscle …