Publisher Correction: Co-contraction of ankle muscle activity during quiet standing in individuals with incomplete spinal cord injury is associated with postural instability

Intensive treadmill training after incomplete spinal cord injury can improve functional walking abilities. To determine the changes in muscle activation patterns that are associated with improvements in walking, we measured the electromyography (EMG) of leg muscles in 17 individuals with incomplete spinal cord injury during similar walking conditions both before and after training. Specific differences were observed between subjects that eventually gained functional improvements in overground walking (responders), compared with subjects where treadmill training was ineffective (nonresponders). Although both groups developed a more regular and less clonic EMG pattern on the treadmill, it was only the tibialis anterior and hamstring muscles in the responders that displayed increases in EMG activation. Likewise, only the responders demonstrated decreases in burst duration and cocontraction of proximal (hamstrings and quadriceps) muscle activity. Surprisingly, the proximal muscle activity in the responders, unlike nonresponders, was three- to fourfold greater than that in uninjured control subjects walking at similar speeds and level of body weight support, suggesting that the ability to modify muscle activation patterns after injury may predict the ability of subjects to further compensate in response to motor training. In summary, increases in the amount and decreases in the duration of EMG activity of specific muscles are associated with functional recovery of walking skills after treadmill training in subjects that are able to modify muscle activity patterns following incomplete spinal cord injury.

Download Full-text

Swing Phase Resistance Enhances Flexor Muscle Activity During Treadmill Locomotion in Incomplete Spinal Cord Injury

Neurorehabilitation and Neural Repair ◽

10.1177/1545968308315595 ◽

2008 ◽

Vol 22 (5) ◽

pp. 438-446 ◽

Cited By ~ 60

Author(s):

Tania Lam ◽

Markus Wirz ◽

Lars Lünenburger ◽

Volker Dietz

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Muscle Activity ◽

Swing Phase ◽

Incomplete Spinal Cord Injury ◽

Flexor Muscle ◽

Cord Injury ◽

Treadmill Locomotion

Download Full-text

Comparison of muscle activity and kinematics during treadmill walking with and without manual assistance in individuals with incomplete spinal cord injury

Journal of Biomechanics ◽

10.1016/s0021-9290(06)83328-2 ◽

2006 ◽

Vol 39 ◽

pp. S108

Author(s):

A. Domingo ◽

G.S. Sawicki ◽

D.P. Ferris

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Muscle Activity ◽

Treadmill Walking ◽

Incomplete Spinal Cord Injury ◽

Cord Injury ◽

Manual Assistance

Download Full-text

Use of the integrated profile for voluntary muscle activity detection using EMG signals with spurious background spikes: A study with incomplete spinal cord injury

Biomedical Signal Processing and Control ◽

10.1016/j.bspc.2015.09.004 ◽

2016 ◽

Vol 24 ◽

pp. 19-24 ◽

Cited By ~ 8

Author(s):

Jie Liu ◽

Qiuping Liu

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Muscle Activity ◽

Activity Detection ◽

Incomplete Spinal Cord Injury ◽

Voluntary Muscle ◽

Cord Injury

Download Full-text

Co-contraction of ankle muscle activity during quiet standing in individuals with incomplete spinal cord injury is associated with postural instability

Scientific Reports ◽

10.1038/s41598-021-99151-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Kai Lon Fok ◽

Jae W. Lee ◽

Janelle Unger ◽

Katherine Chan ◽

Kristin E. Musselman ◽

...

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Postural Sway ◽

Computational Simulation ◽

Joint Stiffness ◽

Medial Gastrocnemius ◽

Quiet Standing ◽

Incomplete Spinal Cord Injury ◽

Mechanical Joint ◽

Cord Injury

AbstractPrevious findings indicate that co-contractions of plantarflexors and dorsiflexors during quiet standing increase the ankle mechanical joint stiffness, resulting in increased postural sway. Balance impairments in individuals with incomplete spinal cord injury (iSCI) may be due to co-contractions like in other individuals with reduced balance ability. Here we investigated the effect of co-contraction between plantar- and dorsiflexors on postural balance in individuals with iSCI (iSCI-group) and able-bodied individuals (AB-group). Thirteen able-bodied individuals and 13 individuals with iSCI were asked to perform quiet standing with their eyes open (EO) and eyes closed (EC). Kinetics and electromyograms from the tibialis anterior (TA), soleus and medial gastrocnemius were collected bilaterally. The iSCI-group exhibited more co-contractions than the AB-group (EO: 0.208% vs. 75.163%, p = 0.004; EC: 1.767% vs. 92.373%, p = 0.016). Furthermore, postural sway was larger during co-contractions than during no co-contraction in the iSCI-group (EO: 1.405 cm/s2 vs. 0.867 cm/s2, p = 0.023; EC: 1.831 cm/s2 vs. 1.179 cm/s2, p = 0.030), but no differences were found for the AB-group (EO: 0.393 cm/s2 vs. 0.499 cm/s2, p = 1.00; EC: 0.686 cm/s2 vs. 0.654 cm/s2, p = 1.00). To investigate the mechanism, we performed a computational simulation study using an inverted pendulum model and linear controllers. An increase of mechanical stiffness in the simulated iSCI-group resulted in increased postural sway (EO: 2.520 cm/s2 vs. 1.174 cm/s2, p < 0.001; EC: 4.226 cm/s2 vs. 1.836 cm/s2, p < 0.001), but not for the simulated AB-group (EO: 0.658 cm/s2 vs. 0.658 cm/s2, p = 1.00; EC: 0.943 cm/s2 vs. 0.926 cm/s2, p = 0.190). Thus, we demonstrated that co-contractions may be a compensatory strategy for individuals with iSCI to accommodate for decreased motor function, but co-contractions may result in increased ankle mechanical joint stiffness and consequently postural sway.

Download Full-text

Cosine tuning determines plantarflexors' activities during human upright standing and is affected by incomplete spinal cord injury

Journal of Neurophysiology ◽

10.1152/jn.00123.2020 ◽

2020 ◽

Author(s):

Kai Lon Fok ◽

Jae W Lee ◽

Janelle Unger ◽

Katherine Chan ◽

Daichi Nozaki ◽

...

Keyword(s):

Spinal Cord ◽

Central Nervous System ◽

Spinal Cord Injury ◽

Nervous System ◽

Knee Extension ◽

Medial Gastrocnemius ◽

Quiet Standing ◽

Incomplete Spinal Cord Injury ◽

Cord Injury ◽

The Central Nervous System

Plantarflexors such as the soleus (SOL) and medial gastrocnemius (MG) play key roles in controlling bipedal stance; however, how the central nervous system controls the activation levels of these plantarflexors is not well understood. Here we investigated how the central nervous system controls the plantarflexors' activation level during quiet standing in a cosine tuning manner where the maximal activation is achieved in a preferred direction (PD). Further, we investigated how spinal cord injury affects these plantarflexors' activations. Thirteen healthy adults (AB) and thirteen individuals with chronic, incomplete spinal cord injury (iSCI) performed quiet standing trials. Their body kinematics, kinetics as well as electromyography signals from the MG and SOL were recorded. In the AB-group, we found that the plantarflexors followed the cosine tuning manner during quiet standing. That is, MG was most active when the ratio of plantarflexion torque to knee extension torque was approximately 2:-3, while SOL was most active when the ratio was approximately 2:1. This suggests that the SOL muscle despite being a monoarticular muscle is sensitive to both ankle plantarflexion and knee extension during quiet standing. The difference in the PDs accounts for the phasic activity of MG and for the tonic activity of SOL. Unlike the AB-group, the MG's activity was similar to the SOL's activity in the iSCI-group, and the SOL PDs were similar to the ones in the AB-group. This result suggests that chronic iSCI affects the control strategy, i.e., cosine tuning, for MG, which may affect standing balance in individuals with iSCI.

Download Full-text