| Description |
Older adults experience age-related challenges including muscle weakness, impaired mobility, and increased fall risk. Further, controlling submaximal muscle forces may also be impaired, particularly with eccentric (ECC) contracions, as they demonstrate greater vaiability in maintaining steady and accurate force output, characterized as muscle force steadiness (MFS), and functional mobility in older who have fallen is very limited. The primary and secondary aims of this dissertation were to compare whether repeated bouts of concentric (CON) and ECC contractions of the knee extensors improves MFS in healthy young (HYA), old (HOA) and older adults who have fallen (OIA), and whether MFS differes between the groups. The tertiary aim was to examine relationships between MFS, MFA and four functional mobility tests (FMT). An exploratory aim was to compare whether resistance training (RT), either traditional or negative eccentric work, improves MFS in OIA in a falls reduction program. Three groups, HYA (age 18-30), HOA (≥65), two or more co-morbid conditions), were recruited. Maximal voluntary isometric contractions (MVIC) were performed. A submaximal target force (50% MVIC) was used when measuring MFS and MFA. The OIA group then performed four FMT, and participated in 12 weeks of RT. Each group demonstrated early improvements in MFS with repeated bouts and obtained stable measures within six to nine trials. The OIA group exhibited greater force variabiliy for both CON and ECC contractions compared to HOA and HYA. HOA exhibited greater force variability for only CON contractions compared to HYA. No significant associations were seen between MFS and FMT. However, MFA and FMT were significantly correlated with moderate to strong associations for only ECC contractions. Twelve weeks of RT was effective in improving MFS for both CON and ECC contractions, while improvement in MFA was attained only during ECC contractions. MFS improved for different age groups under certain conditions with practice, yet differe between age groups. As MFA was associated with EMT during ECC contractions, it may be linked to impaired mobility in OIA. Improvements in MFS and MFA are attainable with RT. |
