Slower walking in the elderly and calf strength.

"Conclusions: In older men, walking at preferred speed allows triceps surae muscles to generate force with more favorable shortening velocity and to enhance use of tendinous tissue elasticity compared to walking at young men's preferred speed. The results suggest that older men may prefer slower walking speeds to compensate for decreased plantarflexor strength."

Slower Walking Speed in Older Men Improves Triceps Surae Force Generation Ability.
Stenroth, Lauri; Sipilä, Sarianna; Finni, Taija; Cronin, Neil J.

http://journals.lww.com/acsm-msse/Abstract/publishahead/Slower_Walking_Speed_in_Older_Men_Improves_Triceps.97437.aspx