Evidence of impaired neuromuscular responses in the support leg to a destabilizing swing phase perturbation in hemiparetic gait

Sharafi, Bahar; Hoffmann, Gilles; Tan, Andrew Q.; Dhaher, Yasin Y.

doi:10.1007/s00221-016-4743-0

“…However, further investigation is necessary to determine if reductions in asymmetry affect interlimb coordination during reactions to perturbations. The data from the current study illustrate how the intact neuromotor system modulates coordination between the upper and lower extremities in response to changes in asymmetry, and these data could serve as useful reference data to understand how sensorimotor impairments such as muscle weakness [40] and transmission delays [41] affect the ability to restore WBAM during perturbation recovery in people post-stroke.…”

Section: Discussionmentioning

confidence: 99%

Asymmetric Gait Patterns Alter the Reactive Control of Intersegmental Coordination Patterns during Walking

Liu

¹

,

Finley

²

2019

Preprint

1

7

0

View full text Add to dashboard Cite

18 19 20 21 22 23 24 provide further insight into how the healthy and impaired nervous system regulates dynamic 49 balance during walking. Introduction 51 Bipedal locomotion is inherently unstable due to the small base of support, long single-52 limb support times, and sensorimotor transmission delays [1]. As a result, we must frequently 53 generate corrective responses to maintain balance in response to both internal and external 54 perturbations [2,3]. For example, to recover from unexpected perturbations such as slips or trips 55 while walking, the nervous system generates reactive control strategies involving simultaneous, 56 coordinated responses of both the upper and lower limbs [4,5]. These reactive, interlimb 57 responses to perturbations can restore stability by generating changes in angular momentum that 58 counteract the body's rotation toward the ground. 59 One conventional method to capture whole-body rotational dynamics during perturbation 60 responses is to compute whole-body angular momentum (WBAM). WBAM reflects the net 61 influence of all the body segments' rotation relative to a specified axis, which is commonly taken 62 to project through the body's center of mass [6-8]. WBAM is highly regulated as its value 63 remains close to zero during normal, unperturbed walking [9,10]. During perturbed walking, 64 angular momentum dramatically deviates from that measured during unperturbed walking [6,7], 65 and this deviation captures the features of body rotation that, if not arrested, would lead to a fall.66 To regain balance when encountering unexpected perturbations, the central nervous system 67 activates muscles to accelerate body segments and restore angular momentum across multiple 68 recovery steps [11,12]. 69Angular momentum can also capture balance impairments in populations with gait 70 asymmetries and sensorimotor deficits such as amputees and stroke survivors. These individuals 71 often have a higher peak-to-peak range of angular momentum than healthy controls [13][14][15][16], and 72 the presence of gait asymmetries may contribute to balance impairments in these populations. 73 For example, the magnitude of step length asymmetry in people-post stroke is negatively 74 correlated with scores on the Berg Balance Scale, indicating that step length asymmetry is 75 associated with increased fall risk [17]. 76 An important question for clinical researchers is whether there is a causal relationship 77 between gait asymmetry and the ability to maintain balance in response to perturbations during 78 walking. Previous work demonstrated that whole-body dynamics, as measured by WBAM, do 79 not change in response to imposed gait asymmetries in healthy individuals [7]. However, the 80 strategy that the central nervous system uses to stabilize whole-body dynamics remains to be 81 determined. There are two distinct hypotheses capable of explaining the negligible influence of 82 asymmetry on whole-body angular momentum. First, the central nervous system may generate 83 stereotypical, invariant intersegmenta...

show abstract

“…As a result, there might not be sufficient time for stroke participants to reduce the angular impulse during the stance phase during the paretic perturbation step. Additionally, people post-stroke may have delayed reactions to paretic perturbations due to sensory transmission or processing deficits, which would contribute to the increased forward loss of balance during paretic perturbations ( 50 – 52 ).…”

Section: Discussionmentioning

confidence: 99%

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke

Liu

¹

,

McNitt-Gray

²

,

Finley

³

2022

View full text Add to dashboard Cite

People post-stroke have an increased risk of falls compared to neurotypical individuals, partly resulting from an inability to generate appropriate reactions to restore balance. However, few studies investigated the effect of paretic deficits on the mechanics of reactive control strategies following forward losses of balance during walking. Here, we characterized the biomechanical consequences of reactive control strategies following perturbations induced by the treadmill belt accelerations. Thirty-eight post-stroke participants and thirteen age-matched and speed-matched neurotypical participants walked on a dual-belt treadmill while receiving perturbations that induced a forward loss of balance. We computed whole-body angular momentum and angular impulse using segment kinematics and reaction forces to quantify the effect of impulse generation by both the leading and trailing limbs in response to perturbations in the sagittal plane. We found that perturbations to the paretic limb led to larger increases in forward angular momentum during the perturbation step than perturbations to the non-paretic limb or to neurotypical individuals. To recover from the forward loss of balance, neurotypical individuals coordinated reaction forces generated by both legs to decrease the forward angular impulse relative to the pre-perturbation step. They first decreased the forward pitch angular impulse during the perturbation step. Then, during the first recovery step, they increased the backward angular impulse by the leading limb and decreased the forward angular impulse by the trailing limb. In contrast to neurotypical participants, people post-stroke did not reduce the forward angular impulse generated by the stance limb during the perturbed step. They also did not increase leading limb angular impulse or decrease the forward trailing limb angular impulse using their paretic limb during the first recovery step. Lastly, post-stroke individuals who scored poorer on clinical assessments of balance and had greater motor impairment made less use of the paretic limb to reduce forward momentum. Overall, these results suggest that paretic deficits limit the ability to recover from forward loss of balance. Future perturbation-based balance training targeting reactive stepping response in stroke populations may benefit from improving the ability to modulate paretic ground reaction forces to better control whole-body dynamics.

show abstract

“…As a result, there might not be sufficient time for stroke participants to reduce the angular impulse during the stance phase during the paretic perturbation step. Additionally, people post-stroke may have delayed reactions to paretic perturbations due to sensory transmission or processing deficits, which would contribute to the increased forward loss of balance during paretic perturbations (Sharafi et al, 2016; C. Wutzke et al, 2013; C.…”

Section: Discussionmentioning

confidence: 99%

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke

Liu

¹

,

McNitt-Gray

²

,

Finley

³

2022

Preprint

View full text Add to dashboard Cite

People post-stroke have an increased risk of falls compared to neurotypical individuals, partly resulting from an inability to generate appropriate reactions to restore balance. However, few studies investigated the effect of paretic deficits on the mechanics of reactive control strategies following forward losses of balance during walking. Here, we characterized the biomechanical consequences of reactive control strategies following perturbations induced by the treadmill belt accelerations. Thirty-eight post-stroke participants and thirteen age-matched and speed-matched neurotypical participants walked on a dual-belt treadmill while receiving perturbations that induced a forward loss of balance. We computed whole-body angular momentum and angular impulse using segment kinematics and reaction forces to quantify the effect of impulse generation by both the leading and trailing limbs in response to perturbations in the sagittal plane. We found that perturbations to the paretic limb led to larger increases in forward angular momentum during the perturbation step than perturbations to the non-paretic limb or to neurotypical individuals. To recover from the forward loss of balance, neurotypical individuals coordinated reaction forces generated by both legs to decrease the forward angular impulse relative to the pre-perturbation step. They first decreased the forward pitch angular impulse during the perturbation step. Then, during the first recovery step, they increased the backward angular impulse by the leading limb and decreased the forward angular impulse by the trailing limb. In contrast to neurotypical participants, people post-stroke did not reduce the forward angular impulse generated by the stance limb during the perturbed step. They also did not increase leading limb angular impulse or decrease the forward trailing limb angular impulse using their paretic limb during the first recovery step. Lastly, post-stroke individuals who scored poorer on clinical assessments of balance and had greater motor impairment made less use of the paretic limb to reduce forward momentum. Overall, these results suggest that paretic deficits limit the ability to recover from forward loss of balance. Future perturbation-based balance training targeting reactive stepping response in stroke populations may benefit from improving the ability to modulate paretic ground reaction forces to better control whole-body dynamics.

show abstract

Evidence of impaired neuromuscular responses in the support leg to a destabilizing swing phase perturbation in hemiparetic gait

Cited by 10 publications

References 38 publications

Asymmetric Gait Patterns Alter the Reactive Control of Intersegmental Coordination Patterns during Walking

Asymmetric Gait Patterns Alter the Reactive Control of Intersegmental Coordination Patterns during Walking

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke

Contact Info

Product

Resources

About