Differences in lower-extremity muscular activation during walking between healthy older and young adults

Abstract

Previous studies have identified differences in gait kinetics between healthy older and young adults. However, the underlying factors that cause these changes are not well understood. The objective of this study was to assess the effects of age and speed on the activation of lower-extremity muscles during human walking. We recorded electromyography (EMG) signals of the soleus, gastrocnemius, biceps femoris, medial hamstrings, tibialis anterior, vastus lateralis, and rectus femoris as healthy young and older adults walked over ground at slow, preferred and fast walking speeds. Nineteen healthy older adults (age, 73 ± 5 years) and 18 healthy young adults (age, 26 ± 3 years) participated. Rectified EMG signals were normalized to mean activities over a gait cycle at the preferred speed, allowing for an assessment of how the activity was distributed over the gait cycle and modulated with speed. Compared to the young adults, the older adults exhibited greater activation of the tibialis anterior and soleus during mid-stance at all walking speeds and greater activation of the vastus lateralis and medial hamstrings during loading and mid-stance at the fast walking speed, suggesting increased coactivation across the ankle and knee. In addition, older adults depend less on soleus muscle activation to push off at faster walking speeds. We conclude that age-related changes in neuromuscular activity reflect a strategy of stiffening the limb during single support and likely contribute to reduced push off power at fast walking speeds.

Antagonist muscle co-activation during straight walking and its relation to kinematics: Insight from young, elderly and Parkinson's disease

“…The analysis of antagonist CAI during gait has been chiefly focused on the study of physiological aging (Hortobágyi et al, 2009;Peterson and Martin, 2010;Schmitz et al, 2009) and on some pathologies like stroke (Lamontagne et al, 2000), or knee osteoarthritis (Hubley-Kozey et al, 2009). Some of the above mentioned studies, and others (for example, Mian et al, 2006), evaluated CAI on thigh muscles.…”

“…One basic element to understand the increase in CAI when increasing velocity is to gain joint stability (Schmitz et al, 2009), and therefore aging, which is related to impairment in balance (Woollacott, 1993), would further increase the need for larger CAI. We meant to understand this point by reviewing literature on diseases impairing balance, like PD, but the relation between gait and antagonist CAI became further complex.…”

“…However it is not clear whether this pattern represents the actual sequence of activation, even in healthy humans. In fact, an increase in antagonist coactivation in the shank and thigh muscles, as a function of the gait velocity, has been reported (Hortobágyi et al, 2009;Schmitz et al, 2009). This suggests an adaptive process aimed at allowing greater stabilization around the joint (Peterson and Martin, 2010;Schmitz et al, 2009).…”

“…In fact, an increase in antagonist coactivation in the shank and thigh muscles, as a function of the gait velocity, has been reported (Hortobágyi et al, 2009;Schmitz et al, 2009). This suggests an adaptive process aimed at allowing greater stabilization around the joint (Peterson and Martin, 2010;Schmitz et al, 2009). This seems to be supported by the fact that aging can lead to loss of balance (Woollacott, 1993) and stability in gait (Hausdorff, 2007;Hausdorff et al, 2001).…”

“…We have evaluated different patterns of gait: physiological gait (young and elderly subjects), and pathological gait (advanced PD during ON-dose, and OFF-dose; with and without FOG). The group of patients, with marked postural instability during gait, was included because increasing CAI seems an adaptive process to gain joint stability while walking (Peterson and Martin, 2010;Schmitz et al, 2009). Subjects were asked to walk in synchrony to a metronome beat.…”