Elsevier

Gait & Posture

Volume 62, May 2018, Pages 497-504
Gait & Posture

Full length article
Electromyographic and biomechanical analysis of step negotiation in Charcot Marie Tooth subjects whose level walk is not impaired

https://doi.org/10.1016/j.gaitpost.2018.04.014Get rights and content

Highlights

  • We studied the step negotiation in CMT subjects who do not show abnormal gait.

  • Kinematics and kinetics of step negotiation were altered in CMT subjects.

  • During the step ascending and descending CMT subjects showed distal muscle weakness.

  • Step negotiation revealed adaptive motor strategies related to muscle weakness.

  • Step negotiation should be evaluated in the early stage of CMT disease.

Abstract

Background

Charcot-Marie-Tooth (CMT) is a slowly progressive disease characterized by muscular weakness and wasting with a length-dependent pattern. Mildly affected CMT subjects showed slight alteration of walking compared to healthy subjects (HS).

Research question

To investigate the biomechanics of step negotiation, a task that requires greater muscle strength and balance control compared to level walking, in CMT subjects without primary locomotor deficits (foot drop and push off deficit) during walking.

Methods

We collected data (kinematic, kinetic, and surface electromyographic) during walking on level ground and step negotiation, from 98 CMT subjects with mild-to-moderate impairment. Twenty-one CMT subjects (CMT-NLW, normal-like-walkers) were selected for analysis, as they showed values of normalized ROM during swing and produced work at push-off at ankle joint comparable to those of 31 HS. Step negotiation tasks consisted in climbing and descending a two-step stair. Only the first step provided the ground reaction force data. To assess muscle activity, each EMG profile was integrated over 100% of task duration and the activation percentage was computed in four phases that constitute the step negotiation tasks.

Results

In both tasks, CMT-NLW showed distal muscle hypoactivation. In addition, during step-ascending CMT-NLW subjects had relevant lower activities of vastus medialis and rectus femoris than HS in weight-acceptance, and, on the opposite, a greater activation as compared to HS in forward-continuance. During step-descending, CMT-NLW showed a reduced activity of tibialis anterior during controlled-lowering phase.

Significance

Step negotiation revealed adaptive motor strategies related to muscle weakness due to disease in CMT subjects without any clinically apparent locomotor deficit during level walking. In addition, this study provided results useful for tailored rehabilitation of CMT patients.

Introduction

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder with a prevalence of one case in 2500 [1]. Despite high genetic heterogeneity, CMT neuropathies are clinically characterized by symmetrical, slowly progressive and length-dependent muscular weakness and wasting, as well as sensory impairment [2]. Therefore, distal lower limb segments are affected earlier and to a greater extent [3], reducing balance and locomotor function [[4], [5]]. Common daily life activities, such as ascending and descending a staircase, are challenging and demanding tasks, due to the degenerative progression of the disease [6]. While the walking of CMT population has already been studied in some follow-up studies [[7], [8], [9], [10], [11]], the changes in muscle function and motor performances during challenging tasks have not yet been addressed. Considering that stairs are frequently encountered during daily activities, it is worthy studying the biomechanics of such tasks.

Biomechanical analyses have shown that, compared with level walking, the ranges of motion of the joints and muscle moments in the lower limbs are greater when ascending and descending stairs [12]. For this reason it would be interesting to study CMT subjects who do not show any alterations during level walking [[8], [10]]. Previous studies have shown that muscular weakness and balance problems impact walking ability of CMT subjects [[4], [5]], consequently we expect that more challenging tasks like ascending and descending stairs, which require both abilities, are able to highlight the disease related-problems also in individuals with CMT who show normal level walking. Step negotiation tasks are mostly based on mechanical coupling between the knee and ankle joints, with knee and ankle extensor muscles playing a dominant role. In particular, stair ascending differs from level walking because the forces needed to accomplish ascent are twice as great as those needed to control level gait and the knee extensors generate most of the energy to move the body forward and upward during the stair ascent [[13], [14]]. The knee muscles are secondarily aided by hip and ankle extensors during body elevation on the step. Differently from level walking, where the role of the plantarflexors is primarily body propulsion [13], during stair ascending the ankle joint contributes to greater dorsiflexion and allows proper positioning of the lower limb for an efficient lifting action on the step. From an energy point of view, stair climbing requires the energy production from one step to the next through concentric contractions of muscles, whereas stair descending is dominated by the absorption of energy at both the ankle and knee joints. Here, the extensor muscles provide control of the movement with respect to the force of gravity through eccentric muscular contractions [15]. In addition, recently biomechanical parameters have yielded promising results in terms of reliability and responsiveness in CMT [[16], [17]].

Based on the above premises, the aim of this study was to investigate the biomechanics and motor function of step ascending and descending of CMT subjects who show a normal level walking.

Section snippets

Subjects and instrumental setup

All the CMT subjects were clinically evaluated through the disease-specific scale, Charcot–Marie–Tooth Examination Score (CMTES [18]).

Kinematic, kinetic, and surface electromyography (EMG) data were collected from 98 CMT subjects (50 males, mean ± SD: age 33.1 ± 18.3 years, weight 59.8 ± 18.7 kg, height 162.0 ± 15.6 cm), affected by the two most common CMT subtypes: CMT1A (associated with the peripheral myelin protein-22, PMP22, gene duplication; 82 subjects, 34 males) and CMTX1 (caused by

Results

All CMT-NLW performed step ascending and step descending tasks independently, without any assistance. The mean value ±SD of CMTES was 4.1 ± 3.2. The time course of the main kinematic and kinetic variables of step ascending and descending are reported for CMT-NLW, superimposed to the range (±SD) of HS in Fig. 1, Fig. 2, respectively.

During level walking no significant differences were found between CMT-NLW and HS on spatio-temporal parameters (See Table 1, upper part). With regard to step

Discussion

The purpose of this study was to investigate the influence of CMT disease in its early stage, when level walking is still not affected, on EMG activity and on the kinetimatics and kinetics of the lower limbs during more challening locomotor tasks, like step negotiation.

In the step ascending task during the first part of the stance phases, which is crucial from an energy point of view to optimize the climbing performance, CMT-NLW showed proximal locomotor alterations likely related to the knee

Conclusion

We performed a comprehensive analysis of locomotor pattern and compensatory strategies during step negotiation in CMT subjects who did not show alterations in level walking. The results of this study provide useful information on their motor skills. In fact, adaptive motor strategies of CMT subjects to overcome the challenge of stair ascending and descending were detected, even though the enrolled CMT subjects had no apparent level walking abnormalities. CMT has no disease-modifying drug

Availability of data and materials section

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests

None of the authors report a conflict of interest.

Acknowledgements

This work was funded by Telethon-Italy (GUP10010) and by Italian Ministry of Health (Fondi IRCCS Ricerca Corrente). The funding sources had no involvement in study design, data collection, analysis and interpretation, writing of the report, and decision to submit the article for publication.

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