Abstract
Locomotor movements are accommodated to various surface conditions by means of specific locomotor adjustments. This study examined underlying age-related differences in neuromuscular control during level walking and on a positive or negative slope, and during stepping upstairs and downstairs. Ten elderly and eight young adults walked on a treadmill at two different speeds and at three different inclinations (0°, +6°, and −6°). They were also asked to ascend and descend stairs at self-selected speeds. Full body kinematics and surface electromyography of 12 lower-limb muscles were recorded. We compared the intersegmental coordination, muscle activity, and corresponding modifications of spinal motoneuronal output in young and older adults. Despite great similarity between the neuromuscular control of young and older adults, our findings highlight subtle age-related differences in all conditions, potentially reflecting systematic age-related adjustments of the neuromuscular control of locomotion across various support surfaces. The main distinctive feature of walking in older adults is a significantly wider and earlier activation of muscles innervated by the sacral segments. These changes in neuromuscular control are reflected in a reduction or lack of propulsion observed at the end of stance in older adults at different slopes, with the result of a delay in the timing of redirection of the centre-of-mass velocity and of an unanticipated step-to-step transition strategy.
Highlights
Aging causes various motor (McGibbon, 2003; Perry et al, 2007) and sensory deficits (Skinner et al, 1984; Seidler et al, 2010)
Locomotor Adjustment in Older Adults to young, older adults’ gait is characterized by shorter step length, longer relative duration of the stance phase, wider burst of muscle activity (Monaco et al, 2010; Santuz et al, 2020), and a distal to proximal shift of joint moments (DeVita and Hortobagyi, 2000; Silder et al, 2008; Anderson and Madigan, 2014; Franz and Kram, 2014). This modification of distal joint moment has an impact on gait kinetics and kinematics (Noble and Prentice, 2008; Bleyenheuft and Detrembleur, 2012; Hafer and Boyer, 2018; Dewolf et al, 2019b; Gueugnon et al, 2019)
Locomotor movements can be accommodated to various situations, such as walking slopes (Hong et al, 2014a,b; Dewolf et al, 2017) or stepping on stairs (McFadyen and Winter, 1988; Silverman et al, 2014), by means of appropriate changes in the intersegmental coordination and muscle activations (Dewolf et al, 2018, 2020b)
Summary
Aging causes various motor (McGibbon, 2003; Perry et al, 2007) and sensory deficits (Skinner et al, 1984; Seidler et al, 2010). Locomotor Adjustment in Older Adults to young, older adults’ gait is characterized by shorter step length, longer relative duration of the stance phase, wider burst of muscle activity (Monaco et al, 2010; Santuz et al, 2020), and a distal to proximal shift of joint moments (DeVita and Hortobagyi, 2000; Silder et al, 2008; Anderson and Madigan, 2014; Franz and Kram, 2014) This modification of distal joint moment has an impact on gait kinetics and kinematics (Noble and Prentice, 2008; Bleyenheuft and Detrembleur, 2012; Hafer and Boyer, 2018; Dewolf et al, 2019b; Gueugnon et al, 2019). Because biomechanical mechanisms of locomotion are tightly correlated with specific motor pool activations in the spinal cord (Cappellini et al, 2010), slope walking is associated with a different involvement of the lumbar and sacral motor pools (Dewolf et al, 2019a)
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