Article

Walking uphill and downhill can be challenging for community-dwelling old adults.
We investigated the effects of age on leg muscle activity amplitudes and timing
during level, uphill, and downhill walking. We hypothesized that old adults would
exhibit smaller increases in ankle extensor muscle activities and greater
increases in hip extensor muscle activities compared to young adults during
uphill vs. level walking. We also hypothesized that, compared to level walking,
antagonist leg muscle coactivation would be disproportionately greater in old vs.
young adults during downhill walking. Ten old (72+/-5yrs) and ten young
(25+/-4yrs) subjects walked at 1.25m/s on a treadmill at seven grades (0 degrees
, +/-3 degrees , +/-6 degrees , +/-9 degrees ).
We quantified the stance phase
electromyographic activities of the gluteus maximus (GMAX), biceps femoris (BF),
rectus femoris (RF), vastus medialis (VM), medial gastrocnemius (MG), soleus
(SOL), and tibialis anterior (TA). Old adults exhibited smaller increases in MG
activity with steeper uphill grade than young adults (e.g., +136% vs. +174% at 9
degrees ). A disproportionate recruitment of hip muscles led to GMAX activity
approaching the maximum isometric capacity of these active old adults at steep
uphill grades (e.g., old vs. young, 73% MVC vs. 33% MVC at +9 degrees ). Neither
uphill nor downhill walking affected the greater coactivation of antagonist
muscles in old vs. young adults. We conclude that the disproportionate
recruitment of hip muscles with advanced age may have critical implications for
maintaining independent mobility in old adults, particularly at steeper uphill grades.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS