Spatio-temporal parameters and intralimb coordination patterns describing hemiparetic locomotion at controlled speed

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Spatio-temporal parameters and intralimb coordination patterns describing hemiparetic locomotion at controlled speed

• Lucio A Rinaldi &
• Vito Monaco 

Journal of NeuroEngineering and Rehabilitation volume 10, Article number: 53 (2013) Cite this article

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Abstract

Background

Comparison between healthy and hemiparetic gait is usually carried out while subjects walk overground at preferred speed. This generates bias due to the lack of uniformity across selected speeds because they reflect the great variability of the functional level of post-stroke patients. This study aimed at examining coordinative adaptations during walking in response to unilateral brain damage, while homologous participants walked at two fixed speeds.

Methods

Five patients with left and five with right chronic hemiparesis, characterized by similar level of motor functioning, were enrolled. Ten non-disabled volunteers were recruited as matched control group. Spatio-temporal parameters, and intralimb thigh-leg and leg-foot coordination patterns were used to compare groups while walking on a treadmill at 0.4 and 0.6 m/s. The likelihood of Continuous Relative Phase patterns between healthy and hemiparetic subjects was evaluated by means of the root mean square of the difference and the cross correlation coefficient. The effects of the group (i.e., healthy vs. hemiparetics), side (i.e., affected vs.unaffected), and speed (e.g., slow vs. fast) were analyzed on all metrics using the Analysis of Variance.

Results

Spatio-temporal parameters of all hemiparetic subjects did not significantly differ from those of healthy subjects nor showed any asymmetry between affected and unaffected limbs. Conversely, both thigh-leg and foot-leg coordination patterns appeared to account for pathology related modifications.

Conclusion

Comparisons between hemiparetic and healthy gait should be carried out when all participants are asked to seek the same suitable dynamic equilibrium led by the same external (i.e., the speed) and internal (i.e., severity of the pathology) conditions. In this respect, biomechanical adaptations reflecting the pathology can be better highlighted by coordinative patterns of coupled segments within each limb than by the spatio-temporal parameters. Accordingly, a deep analysis of the intralimb coordination may be helpful for clinicians while designing therapeutic treatments.

Background

Compensatory strategies adopted by post-stroke patients to increase stability and efficiency of locomotion have been widely described in literature by spatio-temporal parameters, kinematic, and kinetic measures referring to walking both overground [1–3] and on treadmill [4, 5]. On the whole, the gait of post-stroke patients is mainly characterized by reduced speed, stride length, and cadence, decreased angular excursions at leg joints, increased energetic cost, and asymmetry in kinematic and kinetic variables [3]. Furthermore, a recent study highlighted that post-stroke patients walk with different patterns between treadmill and overground and, in particular, the treadmill enhances the asymmetry between affected and unaffected limbs, decreases the self-selected speed and the step length, and increases stance and double support percentages [6].

A cerebrovascular accident has been also shown to significantly modify the coordinative relationship of segments within (i.e., intralimb coordination) and between (i.e., interlimb coordination) lower limbs [7–9]. Specifically, previous authors have noticed that the intralimb coordinative patterns of chronic hemiparetics walking overground at their preferred speed can be characterized by asymmetry between unaffected and affected sides [7], and that the botulinum toxin injections into the rectus femoris of the paretic side can improve the thigh-leg coordination patterns of both limbs [8]. In addition, it was observed that the increase in speed positively influences the interlimb coordination of both arm and lower limb movements of acute patients undergoing intense rehabilitative treatments [9].

One of the common features of all mentioned studies [4, 6–9] is that participants were asked to walk at their self selected speeds, that is – as acknowledged by some authors [3, 4, 10] – the walking speed was not uniform across subjects, basically due to the inherent variability related to the cerebrovascular accident (i.e., different clinical picture, rehabilitative training, neuromuscular adaptation across patients).

Actually, previous authors have already highlighted the importance of considering gait metrics in relation to the walking speed when attempting to classify gait abnormality [11, 12]. This is because the velocity can be viewed as a control parameter of the dynamic system that, when scaled, involves changes of coordination even within the gait of walking alone [7, 13]. Furthermore, in a previous study, Monaco and colleagues [14] demonstrated that the gait analysis, when carried out at controlled and comparable speed, can better pinpoint features between young and elderly healthy subjects than the comparison at self-selected pace.

Concerning post-stroke patients, it is well known that the self-selected speed reflects specific compensative strategies related to their own degree of impairment such that patients walking in a wide range of preferred velocities are characterized by very different functional deficit [15]. However, the speed, per se, affects in a significant fashion gait patterns inducing relevant modifications of the hemiparetic locomotion [12, 15, 16]. As matter of the fact, the inherent instability of the affected limb prompts the patients to an early shift of the weight on the unaffected one inducing an asymmetric duration of stance and swing phases [15, 16]. In spite of this, when patients are asked to walk at faster speeds, i.e., pace comparable to healthy subjects, they show a bilateral increment of joint angular excursions and muscle activation [17], an improved symmetry in double and single support portions [15, 17], and a significant modification of the coordination of pelvis and trunk rotations [12]. The speed-related improvements of the hemiparetic gait seem to be due to more appropriate timing of lower limb muscles, better suited movement coordination, and possibly facilitation of intralimb and interlimb energy transfers [17].

According to these results, it is possible to hypothesize that part of data variability leading previous authors to characterize motor performance of post-stroke patients may have been ascribed to the wide range of speeds rather than to the pathology itself. Specifically, metrics used to describe motor deficits of locomotion, may lack of a suitable sensitivity when different groups of homogenous subjects (e.g., similar age, anthropometric features, severity of the deficit) are observed while walking at the same pace.

This methodological study aimed at investigating the attitude of both spatio-temporal parameters and intralimb coordination patterns to capture some of the neuromuscular adaptations of the hemiparetic locomotion. This goal has been achieved by comparing gait patterns of affected and unaffected sides in post-stroke hemiparetic patients to those of healthy subjects while walking on a treadmill at the same speeds.

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