Do Older Adults and Those Recovered from Low Back Injury Share Common Muscle Activation Adaptations?

Abstract

Theoretical models suggest trunk muscle activation compensates for spinal systems impairments. The purpose of this study was to determine if two populations (older adults and those recovered from a lower back injury (rLBI)) with spinal system impairments have similar muscle activation patterns to each other, but differ from controls. Trunk electromyograms collected from 12 older adults, 16 rLBI, and 19 controls during two dynamic tasks showed that older adults and rLBI had higher activation amplitudes, sustained temporal and more synergistic activation relative to controls. However, differences found between older adults and rLBI suggest that spinal system impairments differed between groups or that recent pain (rLBI) uniquely influenced muscle activation. This sheds light on our understanding of the relationship between spinal system impairments and muscle activation.

Trunk Muscle Activation Patterns Differ Between Those With Low and High Back Extensor Strength During a Controlled Dynamic Task

“…Given PC2 captured both the directionality (positive or negative Table 4) and magnitude (coefficient) of the responsiveness to the lateral flexion moment, data were transformed to absolute values to explore whether the magnitude of responsiveness, regardless of direction, differed between strength groups (Quirk and Hubley-Kozey, 2018) but there were no significant differences ( Table 3).…”

“…However, many factors contribute to this relationship and controversy exist whether this relationship is linear (Larivière et al, 2002;Brown and McGill, 2007) or curvilinear (Larivière et al, 2002). Thus, in agonist muscles, after considering activation necessary to overcome increased antagonist activation amplitudes (Larivière et al, 2002;Brown and McGill, 2007), individuals who recruit greater EMG amplitudes, normalized to maximum voluntary contractions, to perform a task likely have reduced strength (Quirk and Hubley-Kozey, 2018).…”

“…It is theorized that these changes persist following the resolution of pain (Hodges et al, 2013). A cross-sectional study in those suspected to have similar deficits in spinal system function (older adults vs. younger LBI), found that those with a recent experience of pain had measurable differences in trunk muscle activation patterns during a functional task than those who did not (Quirk and Hubley-Kozey, 2018). This suggests that the recent experience of pain could interact with spinal system function to alter muscle activation patterns, but direct measures of spinal system function are needed.…”