Article

Compared to level walking, additional muscle actions are required to raise and
lower the center of mass during uphill and downhill walking, respectively.
However, it remains unclear which muscle recruitment strategies are employed at
typical grades when walking over a range of speeds. Based on previous reports, we
hypothesized that, across a range of walking speeds, hip, knee, and ankle
extensor muscle activations would increase with steeper uphill grade, but only
knee extensor muscle activations would increase with steeper downhill grade. We
also hypothesized that these changes in muscle activations with grade would
become more pronounced at faster walking speeds.
To test these hypotheses,
10 young adults (5M/5F) walked on a standard treadmill at seven grades (0 degrees ,
+/- 3 degrees , +/- 6 degrees , and +/- 9 degrees ) and three speeds (0.75, 1.25,
and 1.75 ms(-1)). We quantified the stance phase electromyographic activities of
the gluteus maximus (GMAX), biceps femoris (BF), rectus femoris (RF), vastus
medialis (VM), medial gastrocnemius (MG), and soleus (SOL) muscles. On average,
compared to level walking, hip (BF: 635%, GMAX: 345%), knee (RF: 165%, VM: 366%),
and ankle (MG: 175%, SOL: 136%) extensor muscle activities increased to walk up 9 degrees , but only knee (RF: 310%, VM: 246%) extensor muscle activities increased
to walk down 9 degrees . Further, these changes in muscle activations with grade
became greater with faster walking speed. We conclude that people employ distinct
uphill (hip, knee, and ankle extensors) and downhill (knee extensors) muscle
recruitment strategies generally across walking speeds and progressively with steeper grade.
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Langue : ANGLAIS