The Dynamic Motor Control Index as a Marker of Age-Related Neuromuscular Impairment

Abstract

Biomarkers that can identify age-related decline in walking function have potential to promote healthier aging by triggering timely interventions that can mitigate or reverse impairments. Recent evidence suggests that changes in neuromuscular control precede changes in walking function; however, it is unclear which measures are best suited for identifying age-related changes. In this study, non-negative matrix factorization of electromyography data collected during treadmill walking was used to calculate two measures of the complexity of muscle co-activations during walking for 36 adults: (1) the number of muscle synergies and (2) the dynamic motor control index. Study participants were grouped into young (18–35 years old), young-old (65–74 years old), and old–old (75+ years old) subsets. We found that the dynamic motor control index [χ2(2) = 9.41, p = 0.009], and not the number of muscle synergies [χ2(2) = 5.42, p = 0.067], differentiates between age groups [χ2(4) = 10.62, p = 0.031, Nagelkerke R2 = 0.297]. Moreover, an impairment threshold set at a dynamic motor control index of 90 (i.e., one standard deviation below the young adults) was able to differentiate between age groups [χ2(2) = 9.351, p = 0.009]. The dynamic motor control index identifies age-related differences in neuromuscular complexity not measured by the number of muscle synergies and may have clinical utility as a marker of neuromotor impairment.

Altered neural control of gait and its association with pain and joint impairment in adults with haemophilic arthropathy: Clinical and methodological implications

“…number of synergies, variance accounted for, motor modules and motor primitives), the Walk-DMC index is a metric that can be interpreted rapidly. [14][15][16][17]21 Hence, it may be applied clinically, for example to evaluate the effects of orthopaedic interventions. 15 The Walk-DMC has been assessed using the sEMG signals of 5-11 muscles.…”

“…Hence, it may be applied clinically, for example to evaluate the effects of orthopaedic interventions 15 . The Walk‐DMC has been assessed using the sEMG signals of 5–11 muscles 14–17,22 . However, it is unknown if the number of muscles selected affects this metric.…”

“…15 The Walk-DMC has been assessed using the sEMG signals of 5-11 muscles. [14][15][16][17]22 However, it is unknown if the number of muscles selected affects this metric.…”

“…Using sEMG, a new tool called the Walking Dynamic Motor Control (Walk‐DMC) index has been proposed as a summary metric of neural control of gait. The Walk‐DMC index has been used to assess synergistic and antagonistic co‐activation changes in response to neurological diseases, following orthopaedic surgeries, in the elderly and in people with haemophilic arthropathy (PWHA) 14–17 . However, whether PWHA and an abnormal Walk‐DMC also have different levels of pain and joint impairment than those with a normal Walk‐DMC and whether the Walk‐DMC is associated with the clinical measures of pain and joint impairment are currently unknown.…”

“…In comparison to complete synergy analysis (i.e. number of synergies, variance accounted for, motor modules and motor primitives), the Walk‐DMC index is a metric that can be interpreted rapidly 14–17,21 . Hence, it may be applied clinically, for example to evaluate the effects of orthopaedic interventions 15 .…”