Empowering Older Adults: Power Assessment Based On Type IIx Muscle Fiber Abundance In Aging

Abstract

Older adults lose power as they age from the result of multiple aging processes. Older adults loose muscle mass, in particular type IIx muscle fibers, as they age which results in a loss of power. The loss of power is different than just a loss of strength. Power is the product of force and velocity, whereas strength is force alone and at its peak when velocity is zero. Power loss is associated with poor balance and risk of falling. Research has found that specific interventions can increase power output in older adults, but there is not a substantial amount of research that has quantified how much of the change in power from the interventions is the result of the change in MHC IIx abundance. There are also no current models on the relationship between power and type IIx content. Therefore, I compared the ability of two prominent methods of assessing fiber type composition in muscle samples to model fiber type contribution to power production. Finding an accurate model would allow health care providers to better assess the mechanisms contributing to enhanced power output with intervention. I compared the two main methods used for finding muscle fiber abundance, immunohistochemistry (IHC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), to see which would better predict power. Together, these contributed to an algebraic predictor of muscle power, formulated based on seven healthy subjects. We measured peak power output of each subject using dynamometry. We then took muscle biopsies from the vastus lateralis of each subject and ran SDS-PAGE and IHC on their samples. I used a linear regression analysis to compare each methods prediction ability of power Surprisingly, neither IHC nor SDS PAGE were effective in predicting power output in our cohort. Alternate approaches to assessing the expression of MHC IIx may be necessary to better predict peak power output from voluntary contractions.