Body Composition and gait speed.

"In older adults, every 0.1-m/s slower gait speed is associated with a 12% higher mortality. However, little research has identified risk factors for gait-speed decline."

Reduction in activity, particularly challenging difficult activity, stuff that asks a little more from you, the typical stuff that the elderly do not wish to engage in, is a bigger piece to their gait and movement decline that they likely think.

Conclusions: "High and increasing thigh intermuscular fat are important predictors of gait-speed decline, implying that fat infiltration into muscle contributes to a loss of mobility with age. Conversely, a decreasing thigh muscle area is also predictive of a decline in gait speed."

https://www.ncbi.nlm.nih.gov/pubmed/23364001

Am J Clin Nutr. 2013 Mar;97(3):552-60. doi: 10.3945/ajcn.112.047860. Epub 2013 Jan 30.

Associations between body composition and gait-speed decline: results from the Health, Aging, and Body Composition study.

Beavers KM1, Beavers DP, Houston DK, Harris TB, Hue TF, Koster A, Newman AB, Simonsick EM, Studenski SA, Nicklas BJ, Kritchevsky SB.