Adaptive behaviour of the spinal cord in the transition from quiet stance to walking.

BACKGROUND: Modulation of nociceptive withdrawal reflex (NWR) excitability was evaluated during gait initiation in 10 healthy subjects to investigate how load- and movement-related joint inputs activate lower spinal centres in the transition from quiet stance to walking. A motion analysis system integrated with a surface EMG device was used to acquire kinematic, kinetic and EMG variables. Starting from a quiet stance, subjects were asked to walk forward, at their natural speed. The sural nerve was stimulated and EMG responses were recorded from major hip, knee and ankle muscles. Gait initiation was divided into four subphases based on centre of pressure and centre of mass behaviours, while joint displacements were used to categorise joint motion as flexion or extension. The reflex parameters were measured and compared between subphases and in relation to the joint kinematics. RESULTS: The NWR was found to be subphase-dependent. NWR excitability was increased in the hip and knee flexor muscles of the starting leg, just prior to the occurrence of any movement, and in the knee flexor muscles of the same leg as soon as it was unloaded. The NWR was hip joint kinematics-dependent in a crossed manner. The excitability of the reflex was enhanced in the extensor muscles of the standing leg during the hip flexion of the starting leg, and in the hip flexors of the standing leg during the hip extension of the starting leg. No notable reflex modulation was observed in the ankle muscles. CONCLUSIONS: Our findings show that the NWR is modulated during the gait initiation phase. Leg unloading and hip joint motion are the main sources of the observed modulation and work in concert to prepare and assist the starting leg in the first step while supporting the contralateral leg, thereby possibly predisposing the lower limbs to the cyclical pattern of walking.

Gait pattern in inherited cerebellar ataxias.

Our aim was to perform a comprehensive analysis of the global and segmental features of gait in patients with genetically confirmed inherited ataxias. Sixteen patients with autosomal dominant (spinocerebellar ataxia, SCA1 or 2) or recessive (Friedreich's ataxia, FRDA) ataxia were studied. We used a motion analysis system to record gait kinematic and kinetic data. We measured the mean values of global (time-distance parameters, COM displacement, support moment) and segmental gait parameters (joint displacement and inter-joint coordination), as both discrete and continuous variables, and their variability and correlations with International Cooperative Ataxia Rating Scale (ICARS) scores. We found a marked difference in all global gait parameters between the ataxic patients and the controls and close correlations between longer stride and stance duration and lower gait, posture and total ICARS scores. The only difference between the two patient groups was a shorter step length in the FRDA patients. As regards the segmental features, we found a significantly different waveform shape for all continuous kinematic and kinetic measures between the ataxic patients and the healthy controls, but only minor differences for the discrete measures. Intersegmental coordination evaluated using the continuous relative phase method revealed an irregular alternating joint behaviour without clear evidence of the synchronous pattern of alternating proximal/distal joint seen in healthy subjects. For almost all gait parameters we observed a markedly higher intra-subject variability in the ataxic patients versus the controls, which was strongly related to the clinical ICARS scores. Patients with chronic, progressive inherited ataxias lose the ability to "stabilize" a walking pattern that can be repeated over time. The most peculiar aspect of the gait of inherited ataxia patients, regardless the different genetic forms, seems to be the presence of increased variability of all global and segmental parameters rather than an invariant abnormal gait pattern.

Four-week trunk-specific rehabilitation treatment improves lateral trunk flexion in Parkinson's disease.

People with Parkinson's disease (PD) often have a posture characterized by lateral trunk flexion poorly responsive to antiparkinsonian drugs. To examine the effects of a rehabilitation programme (daily individual 90-minute-sessions, 5-days-a-week for 4-consecutive weeks) on lateral trunk flexion and mobility, 22 PD patients with mild to severe lateral trunk flexion, and 22 PD patients without trunk flexion were studied. Patients were evaluated using the Unified Parkinson's Disease Rating Scale motor subscale (UPDRS-III) score, and the kinematic behavior of the trunk was recorded by means of an optoelectronic system to determine: a) trunk flexion, inclination and rotation values in the erect standing posture; b) ranges of trunk flexion and inclination during trunk movements. After the treatment, significant decreases in trunk flexion [24 degrees (4) vs. 14 degrees (3), P < 0.001] and inclination in the static condition [23 degrees (5) vs. 12 degrees (4), P < 0.001)] were observed, both of which were maintained at the 6-month follow up. During the trunk flexion task, a significantly increased range of trunk flexion [64 degrees (15) vs. 83 degrees (15), P < 0.001] was observed; similarly, during the lateral bending task, the range of trunk inclination was found to be significantly increased, both toward the side of the trunk deviation [29 degrees (8) vs. 42 degrees (13), P < 0.01] and toward the contralateral side [14 degrees (6) vs 29 degrees (11), P < 0.01]. No further significant changes were observed at the 6-month follow-up. Trunk flexion and inclination values in the upright standing posture correlated slightly with the UPDRS-III score. Our findings show that significant improvements in axial posture and trunk mobility can be obtained through the 4-week rehabilitation programme described, with a parallel improvement in clinical status.

Modulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movement.

In the present study we investigated the probability, latency and duration of the inhibitory component of the withdrawal reflex elicited by painful electrical stimulation of the index finger in humans. The stimulus consisted of a train of high-intensity pulses. The investigation was carried out in several upper limb muscles during isometric contractions of different strengths and during a motor sequence consisting of reaching, picking up and transporting an object. We used a new algorithm to detect and characterize the inhibitory reflex. The reflex was found in all muscles except the brachioradialis at all the isometric contraction strengths, and showed a distal-to-proximal gradient of latency and duration. Conversely, during movement the reflex probability was high (> 80%) in the anterior deltoid and triceps muscles during reaching, in the extensor carpi radialis muscle during transporting of the object, and in the first interosseous muscle during both picking up and transporting of the object. This modulation of inhibitory reflex transmission in the upper limb muscles suggests that the motor response is organized in such a way as to inhibit the overall ongoing motor task by interrupting motion during reaching and by releasing the object during transporting. This pattern of modulation appears to differ markedly from that previously reported for the excitatory component of the withdrawal reflex. Study of the nociceptive inhibitory reflexes during movement offers new and more profound insights into the functional anatomical organization of the spinal interneuronal network mediating sensory-motor integration.

Long-term effects on motor cortical excitability induced by repeated muscle vibration during contraction in healthy subjects.

OBJECTIVE: The effects of a novel repeated muscle vibration intervention (rMV; 100 Hz, 90 min over 3 consecutive days) on corticomotor excitability were studied in healthy subjects. METHODS: rMV was applied over the flexor carpi radialis (FCR) during voluntary contraction (experiment 1), during relaxation and during contraction without vibration (experiment 2). Focal transcranial magnetic stimulation (TMS) was applied before rMV and one hour, and one, two and three weeks after the last muscle vibration intervention. At each of these time points, we assessed the motor map area and volume in the FCR, extensor digitorum communis (EDC) and abductor digiti minimi (ADM). Short-interval intracortical inhibition (SICI) and facilitation (ICF) were tested for the flexor/extensor muscles alone. RESULTS: Following rMV under voluntary contraction, we observed a significant reduction in the FCR map volumes and an enhancement in the EDC. SICI was increased in the FCR and reduced in the EDC. These changes persisted for up to two weeks and occurred at the cortical level in the hemisphere contralateral to the side of the intervention. CONCLUSION: We conclude that rMV, applied during a voluntary contraction, may induce prolonged changes in the excitatory/inhibitory state of the primary motor cortex. These findings may represent an important advance in motor disorder rehabilitation.

Effects of 8-week strength training with two models of chest press machines on muscular activity pattern and strength.

The purposes of this study were to assess: (i) the effects of 8-week training programs with constrained-path and unconstrained-path chest press machines on 1-RM; (ii) the different activity patterns of selected arm and shoulder girdle muscles during push movement performed on the different machines; (iii) the transfer of the training effects from one machine to the other. Twenty healthy, sedentary women (mean+/-SD age, 24.8+/-1.0yrs), randomized to either the FM or CM strength training protocols were evaluated before and after the strength training program. Muscular activity signals were recorded by surface electromyography (sEMG) from eight muscles while each subject performed the exercise on each machine. Muscle strength was defined by a 1 repetition maximum (1-RM) test for each subject on each machine. Both machines were effective in improving 1-RM, but the 1-RM increased more in the FM than the CM. Adaptive change in the sEMG was observed in all muscles after training on the FM machine, but not within the stabilizers when training on the CM machine. The results suggest that training in an unconstrained condition provides a more effective method for improving inter-muscular coordination via adaptation of the motor strategy aimed at optimising muscular efforts.

Kinematic and electromyographic study of the nociceptive withdrawal reflex in the upper limbs during rest and movement.

This study set out to evaluate nociceptive withdrawal reflex (NWR) excitability and the corresponding mechanical response in the upper limbs during rest and movement. We used a three-dimensional motion analysis system and a surface EMG system to record, in 10 healthy subjects, the NWR in eight upper limb muscles and the corresponding mechanical response in two experimental conditions: rest and movement (reaching for, picking up, and moving a cylinder). The NWR was elicited through stimulation of the index finger with trains of pulses delivered at multiples of the pain threshold (PT). We correlated movement types (reach-to-grasp, grasp-and-lift), movement phases (acceleration, deceleration), and muscle activity types (shortening, lengthening, isometric) with the presence/absence of the NWR (reflex-muscle pattern), with NWR size values, and with the mechanical responses. At rest, when the stimulus was delivered at 4x PT, the NWR was present, in all muscles, in >90% of trials, and the mechanical response consisted of wrist adduction, elbow flexion, and shoulder anteflexion. At this stimulus intensity, during movement, the reflex-muscle pattern, reflex size, and mechanical responses were closely modulated by movement type and phase and by muscle activity type. We did not find, during movement, significant correlations with the level of EMG background activity. Our findings suggest that a complex functional adaptation of the spinal cord plays a role in modulating the NWR in the transition from rest to movement and during voluntary arm movement freely performed in three-dimensional space. Study of the upper limb NWR may provide a window onto the spinal neural control mechanisms operating during movement.

Relationship between recovery of calf-muscle biomechanical properties and gait pattern following surgery for achilles tendon rupture.

BACKGROUND: The relationship between ankle plantar flexor biomechanical properties and gait pattern following surgery for acute rupture of the Achilles tendon has not yet been fully investigated. METHODS: Forty-nine young adults (27 men and 22 women) who underwent surgical repair of a complete Achilles tendon rupture were evaluated at 3, 6, 12 and 24 months by clinical assessment, biomechanical evaluation and gait analysis. FINDINGS: Ankle range of motion, plantar flexor passive stiffness and concentric strength were recovered within 12 months. Gait abnormalities related to these factors took longer to disappear owing to the presence of anomalous muscle patterns. At 24 months, a deficit in calf-muscle eccentric strength was still present, determining adaptive changes in gait strategy that involved ankle motion and coordinated muscular activity. INTERPRETATION: Improvement of gait pattern is slower than recovery of plantar flexor mechanical properties. Persisting mechanical impairment resulting in gait adaptations may be detrimental to the healing structures by increasing stress on the Achilles tendon. Restoration of calf-muscle eccentric strength and coordinated antagonist muscle activity should be key points in postoperative rehabilitation following surgical repair of Achilles tendon rupture.

Foot drop and plantar flexion failure determine different gait strategies in Charcot-Marie-Tooth patients.

OBJECTIVE: To describe the temporal, kinetic, kinematic, electromyographic and energetic aspects of gait in Charcot-Marie-Tooth patients with foot drop and plantar flexion failure. METHODS: A sample of 21 patients fulfilling clinical, electrodiagnostic and genetic criteria for Charcot-Marie-Tooth disease were evaluated by computerized gait analysis system and compared to a group of matched healthy subjects. Patients were classified as having isolate foot drop (group 1) and association of foot drop and plantar flexion failure (group 2). RESULTS: While it was impossible to detect a reliable gait pattern when the group of patients was considered as a whole and compared to healthy subjects, we observed two distinctive gait patterns when patients were subdivided as group 1 or 2. Group 1 showed a gait pattern with some characteristics of the "steppage pattern". The complex motor strategy adopted by this group leads to reduce the swing velocity and to preserve the step length in spite of a high energy consumption. Group 2 displayed a "clumsy pattern" characterized by very slow gait with reduced step length, a broader support area and great reduction in the cadence. This group of patients is characterized by a low energy consumption and greater energy recovery, due above all to the primary deficit and the various compensatory mechanisms. CONCLUSIONS: Such between-group differences in gait pattern can be related to both primary motor deficits and secondary compensatory mechanisms. Foot drop and plantar flexion failure affect the overall gait strategy in Charcot-Marie-Tooth patients.

Effectiveness of radial shock-wave therapy for calcific tendinitis of the shoulder: single-blind, randomized clinical study.

BACKGROUND AND PURPOSE: Radial shock-wave therapy (RSWT) is a pneumatically generated, low- to medium-energy type of shock-wave therapy. This single-blind, randomized, "less active similar therapy"-controlled study was performed to evaluate the effectiveness of RSWT for the management of calcific tendinitis of the shoulder. SUBJECTS: Ninety patients with radiographically verified calcific tendinitis of the shoulder were tested. METHODS: Subjects were randomly assigned to either a treatment group (n=45) or a control group (n=45). Pain and functional level were evaluated before and after treatment and at a 6-month follow-up. Radiographic modifications in calcifications were evaluated before and after treatment. RESULTS: The treatment group displayed improvement in all of the parameters analyzed after treatment and at the 6-month follow-up. Calcifications disappeared completely in 86.6% of the subjects in the treatment group and partially in 13.4% of subjects; only 8.8% of the subjects in the control group displayed partially reduced calcifications, and none displayed a total disappearance. DISCUSSION AND CONCLUSION: The results suggest that the use of RSWT for the management of calcific tendinitis of the shoulder is safe and effective, leading to a significant reduction in pain and improvement of shoulder function after 4 weeks, without adverse effects.

Modelling the spine as a deformable body: Feasibility of reconstruction using an optoelectronic system.

The aims of this study were to develop a kinematic model of the spine, seen as a continuous deformable body and to identify the smallest set of surface markers allowing adequate measurements of spine motion. The spine is widely considered as a rigid body or as a kinematic chain made up of a smaller number of segments, thereby introducing an approximation. It would be useful to have at our disposal a technique ensuring accurate and repeatable measurement of the shape of the whole spine. Ten healthy subjects underwent a whole-spine radiographic assessment and, simultaneously, an optoelectronic recording. Polynomial interpolations of the vertebral centroids, of the whole set of markers were performed. The similarity of the resulting curves was assessed. Our findings indicate that spine shape can be reproduced by 5th order polynomial interpolation. The best approximating curves are obtained from either 10- or 9-marker sets. Sagittal angles are systematically underestimated.

Reorganization of multi-muscle and joint withdrawal reflex during arm movements in post-stroke hemiparetic patients.

OBJECTIVES: To investigate the behavior of the nociceptive withdrawal reflex (NWR) in the upper limb during reaching and grasping movements in post-stroke hemiparetic patients. METHODS: Eight patients with chronic stroke and moderate motor deficits were included. An optoelectronic motion analysis system integrated with a surface EMG machine was used to record the kinematic and EMG data. The NWR was evoked through a painful electrical stimulation of the index finger during a movement which consisted of reaching out, picking up a cylinder, and returning it to the starting position. RESULTS: We found that: (i) the NWR is extensively rearranged in hemiparetic patients, who were found to present different kinematic and EMG reflex patterns with respect to controls; (ii) patients partially lose the ability to modulate the reflex in the different movement phases; (iii) the impairment of the reflex modulation occurs at single-muscle, single-joint and multi-joint level. CONCLUSIONS: Patients with chronic and mild-moderate post-stroke motor deficits lose the ability to modulate the NWR dynamically according to the movement variables at individual as well as at multi-muscle and joint levels. SIGNIFICANCE: The central nervous system is unable to use the NWR substrate dynamically and flexibly in order to select the muscle synergies needed to govern the spatio-temporal interaction among joints.

Kinematic and neurophysiological models: future applications in neurorehabilitation.

This paper emphasizes the importance of developing kinematic and neurophysiological methods for evaluating motor and functional recovery in the field of neurorehabilitation. From a review of the literature, it is concluded that optoelectronic motion analysis and neurophysiological techniques, such as the study of nociceptive withdrawal reflex, might constitute useful applications for future research.

Comparison between kinematic and kinetic methods for computing the vertical displacement of the center of mass during human hopping at different frequencies.

Kinematic and kinetic methods (sacral marker, reconstructed pelvis, segmental analysis, and force platform methods) have been used to calculate the vertical excursion of the center of mass (COM) during movement. In this study we compared the measurement of vertical COM displacement yielded by different methods during able-bodied subjects' hopping at different frequencies (varying between 1.2 and 3.2 Hz). ANOVA revealed a significant interaction between hopping frequency and method (p < 0.001), showing that increasing hopping frequency reduced the differences between methods. A post hoc analysis revealed a significant difference between all methods at the lowest hopping frequency and between the force platform and both the sacral marker and reconstructed pelvis methods at the intermediate hopping frequencies, with differences ranging from 16 to 67 millimeters (all p < 0.05). Results are discussed in view of each methods' limits. We conclude that the segmental analysis and force platform methods can be considered to provide the most accurate results for COM vertical excursion during human hopping in a large range of hopping frequency.