The impact of incline and speed of treadmill on ankle muscle activity in middle-aged adults.

OBJECTIVE

Additional demands associated with changing walking incline and speed combined with normal aging related changes in muscle recruitment can make walking difficult. This study examined the effects of walking on a treadmill at different inclines and speeds on ankle muscles in healthy middle-aged adults.

METHODS

Fifteen healthy subjects (10M/5F) walked on a standard treadmill at three different inclines (0°, 3°, and 6°) and speeds (self-selected, self-selected+20%, self-selected+40%). The electromyographic activity of Medial Gastrocnemius (MG), and Tibialis anterior (TA) muscles was measured during the push off phase of the gait.

RESULTS

Bilateral MG muscle activity increased when subjects walked uphill compared with level walking (p < 0.05), but no changes were seen with increasing walking speed (p > 0.05). Right MG (dominant side) activity increased at all inclines, but only at 6° on left side and also MG muscle activity was delayed on the left side at faster speed (p < 0.05).

CONCLUSION

The bias towards using muscles in the dominant leg in middle-aged subjects to overcome challenging walking conditions may be an age-related adaptation. These results suggest that future studies in the stroke population are needed to examine the impact of hemiparesis of the dominant leg as this group of persons post-stroke may be more likely to experience greater impairment of muscle activation patterns during walking on sloped surfaces.