Muscle power as a countermeasure of functional ability decline during aging: age trajectories, assessment, training and application in the clinical setting
- Autores: Julian Alcazar
- Directores de la Tesis: LUIS MARIA ALEGRE DURAN (dir. tes.), Amelia Guadalupe Grau (codir. tes.)
- Lectura: En la Universidad de Castilla-La Mancha ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Joseph F. Signorile (presid.), Anthony J. Blazevich (secret.), Pedro E. Alcaraz Ramón (voc.)
- Programa de doctorado: Programa de Doctorado en Investigación Sociosanitaria y de la Actividad Física por la Universidad de Castilla-La Mancha
- Materias:
- Enlaces
- Tesis en acceso abierto en: RUIdeRA
- Resumen
Background The aging of the global population has led to a dramatic increase in the number and proportion of people experiencing mobility limitations at old age. The World Health Organization (WHO) has encouraged health systems to prioritize the healthy aging goals of building and maintaining functional ability in order to revert this situation. Muscle power has been found to decline with age at an earlier and faster rate than muscle mass and strength, and is more strongly related with mobility limitations, cognitive decline and mortality. Therefore, the main goals of the present PhD thesis were: 1) to evaluate the pattern and time course of changes in relative muscle power throughout the lifespan in healthy women and men (Study 1); 2) to systematically review the different protocols/instruments used in the literature to assess muscle power in older adults and compare the reliability and validity of several of these protocols (Studies 2 and 3); 3) to analyze the effects of a concurrent exercise training program combining high-intensity interval endurance training and power training on limb muscle dysfunction and systemic oxidative stress in older people with chronic obstructive pulmonary disease (COPD) (Studies 4 and 5); 4) to measure the validity and functional relevance of a clinical tool to assess muscle power in older people (the sit-to-stand (STS) muscle power test) (Studies 6, 7 and 8); and 5) to provide normative data, cut-off points and minimal clinically important difference values for power values obtained by the STS muscle power test (Studies 9 and 10).
Methods The present PhD thesis is composed by 10 studies in which voluntarily participated different cohorts (the “Copenhagen Sarcopenia Study”: 1305 subjects aged 20-93 years; the “EXERNET Multi-center Study”: 2662 subjects aged 65-91 years; a Belgian cohort: 1083 subjects aged 60-93 years; a Portuguese cohort: 4856 subjects aged 65-103 years; and the “Toledo Study for Healthy Aging”: 1804 subjects aged 67-101 years) and groups of older people (in total 79 subjects aged 65-90). Briefly, anthropometrics (body mass and height), body composition (assessed by bio-electrical impedance analysis or dual x-ray absorptiometry) and skeletal muscle size and architecture (assessed by ultrasonography or computed tomography) were evaluated. Muscle power was assessed with the Nottingham power rig and also using an instrumented (linear position transducer) leg press machine. Also, an equation based on the subject’s body mass and height, chair height and performance in the traditional STS test was created (called the STS muscle power test) to estimate muscle power, and its validation against the results obtained from the two above-mentioned instruments was tested. Physical performance and frailty were measured using various functional tests and batteries widely used in the literature (e.g. habitual gait speed, maximal gait speed, timed up-and-go test and 6-min walking test). Moreover, other health-related outcomes such as cognitive function and quality of life were evaluated using validated questionnaires. In the studies conducted in older people with COPD we further measured lung function (spirometry), peak aerobic capacity (incremental cardiopulmonary exercise test) and systemic oxidative stress (plasma protein carbonylation). The COPD subjects were randomly assigned to a 12-week exercise training (combining high-intensity interval training and power training) or a control group. Finally, the systematic review was conducted and reported in accordance with the PRISMA statement. All the statistical analyses were performed according to standard procedures and the level of significance was set at α = 0.05.
Results Relative muscle power declined above the age of 40 years in both women and men influenced by an increase in body mass index and a decrease in specific muscle power (p<0.05); while above the age of 75 years in women and 65 years in men the decline in relative muscle power was due to the loss of both specific muscle power and leg lean mass (p<0.05). The systematic review showed that major discrepancies in muscle power testing protocols existed in the literature, although they were proved to be relatively safe (one adverse event every 144-658 tests) in older people with a broad range of health and functional states. In this line, we found that registering mean values of force and velocity, conducting 3 attempts per load and assessing at least 3 loads was more reliable than other alternatives (p<0.05). On the other hand, the inclusion of a strength-shortening cycle muscle action increased force and power among older people with COPD (p<0.05), and was negatively correlated with physical performance, skeletal muscle size and pennation angle (p<0.05). Older people with COPD presented lower muscle power values than age-matched healthy controls (p<0.05). The 12-week concurrent exercise program produced positive changes among the COPD subjects in mid-thigh muscle cross-sectional area (+4%), vastus lateralis pennation angle (+19%), peak VO2 uptake (+14%), maximum muscle power (+51%), STS time (‒24%), self-reported health status (+20%) and systemic oxidative stress (‒27%) (p<0.05). Muscle power values derived from the STS muscle power test were observed to be correlated with those obtained from the instrumented leg press equipment (r=0.72) and the Nottingham power rig (r=0.75) (p<0.001). STS power was better correlated with lean mass, cognitive function and physical performance than other measures such as STS time, number of STS repetitions, handgrip strength and muscle power recorded with the Nottingham power rig (p<0.05). In addition, the pattern of decline in STS power values with age did not differ from that noted for power values registered with a previously validated instrument (p>0.05). Age-adjusted logistic regression analyses showed low relative STS muscle power to be associated with impaired physical function, frailty and poor quality of life in both older men and women and disability in older women, while sarcopenia was only associated with impaired physical function and frailty in older men and disability in older women (p<0.05). Receiver operator characteristic curves (ROC) yielded 2.1 W·kg-1 in women and 2.6 W·kg-1 in men as optimal cut-off points for low relative STS power according to their ability to discriminate between older people with and without mobility limitations (area under the curve = 0.85 and 0.89, respectively) (p<0.05).
Conclusions Relative muscle power declined above 40 years in both women and men, but the main reasons leading to this decline varied throughout the lifespan (Study 1). Importantly, the great variation in muscle power testing protocols noted across studies may limit consensus in the literature (Study 2). Some parameters related with data collection and the number of attempts and loads performed during testing were found to influence reliability and the association between muscle power and physical performance in older adults (Study 3). On the other hand, despite older people with COPD exhibited decreased muscle power values (Study 4), the application of an exercise training program combining high-intensity interval training and power training improved limb muscle dysfunction and systemic oxidative stress in older people with COPD (Study 5). Finally, our proposed STS muscle power test was found to be valid to assess muscle power in older adults, showed a higher functional relevance compared with other traditionally used measures, and its pattern of change with age did not differ from the one observed using a previously validated instrument (Studies 6, 7 and 8). Furthermore, low relative STS muscle power proved to be more clinically relevant than sarcopenia among older men and women (Study 9), and the reported sex-specific cut-off points for low relative STS muscle power were demonstrated to discriminate satisfactorily between older subjects with and without mobility limitations (Study 10).
