Claudine J.C. Lamoth

Effects of chronic low back pain on trunk coordination and back muscle activity during walking: changes in motor control

Low back pain (LBP) is often accompanied by changes in gait, such as a decreased (preferred) walking velocity. Previous studies have shown that LBP diminishes the normal velocity-induced transverse counter-rotation between thorax and pelvis, and that it globally affects mean erector spinae (ES) activity. The exact nature and causation of these effects, however, are not well understood. The aim of the present study was to examine in detail the effect of walking velocity on global trunk coordination and ES activity as well as their variability to gain further insights into the effects of non-specific LBP on gait. The study included 19 individuals with non-specific LBP and 14 healthy controls. Gait kinematics and ES activity were recorded during treadmill walking at (1) a self-selected (comfortable) velocity, and (2) sequentially increased velocities from 1.4 up to maximally 7.0xa0km/h. Pain intensity, fear of movement and disability were measured before the experiment. The angular movements of thorax, lumbar and pelvis were recorded in three dimensions. ES activity was recorded with pairs of surface electrodes. Trunk–pelvis coordination and mean amplitude of ES activity were analyzed. In addition, invariant and variant properties of trunk kinematics and ES activity were studied using principal component analysis (PCA). Comfortable walking velocity was significantly lower in the LBP participants. In the transverse plane, the normal velocity-induced change in pelvis–thorax coordination from more in-phase to more antiphase was diminished in the LBP participants, while lumbar and pelvis rotations were more in-phase compared to the control group. In the frontal plane, intersegmental timing was more variable in the LBP than in the control participants, with additional irregular movements of the thorax. Rotational amplitudes were not significantly different between the LBP and control participants. In the LBP participants, the pattern of ES activity was affected in terms of increased (residual) variability, timing deficits, amplitude modifications and frequency changes. The gait of the LBP participants was characterized by a more rigid and less variable kinematic coordination in the transverse plane, and a less tight and more variable coordination in the frontal plane, accompanied by poorly coordinated activity of the lumbar ES. Pain intensity, fear of movement and disability were all unrelated to the observed changes in coordination, suggesting that the observed changes in trunk coordination and ES activity were a direct consequence of LBP per se. Clinically, the results imply that conservative therapy should consider gait training as well as exercises aimed at improving both intersegmental and muscle coordination.

Gait coordination after stroke: Benefits of acoustically paced treadmill walking

Background and Purpose: Gait coordination often is compromised after stroke. The purpose of this study was to evaluate the efficacy of acoustically paced treadmill walking as a method for improving gait coordination in people after stroke. Participants: Ten people after stroke volunteered for the study and comprised the experimental group. Nine elderly people who were healthy served as a control group. Methods: Gait cycle parameters, interlimb coordination, and auditory-motor coordination were examined while participants walked on a treadmill with and without acoustic pacing. Results: Stride frequency was adjusted to different acoustic pacing frequencies in all participants. In people after stroke, gait symmetry improved with acoustic pacing. They predominantly coordinated movements of the nonparetic limb to ipsilateral tones. Discussion and Conclusion: The results suggest that acoustically paced treadmill walking provides an effective means for immediately modifying stride frequency and improving gait coordination in people after stroke and, therefore, may be usefully applied in physical therapist practice. Future research directions for developing guidelines for using acoustically paced treadmill walking in physical therapist practice are discussed.

Characteristics of instructed and uninstructed interpersonal coordination while walking side-by-side.

We examined how people synchronize their leg movements while walking side-by-side on a treadmill. Walker pairs were either instructed to synchronize their steps in in-phase or in antiphase or received no coordination instructions. Frequency and phase analysis revealed that instructed in-phase and antiphase coordination were equally stable and independent of walking speed and the difference in individually preferred stride frequencies. Without instruction we found episodes of frequency locking in three pairs and episodes of phase locking in four pairs, albeit not always at (or near) 0 degrees or 180 degrees. Again, we found no difference in the stability of in-phase and antiphase coordination and no systematic effects of walking speed and the difference in individually preferred stride frequencies. These results suggest that the Haken-Kelso-Bunz model for rhythmic interlimb coordination does not apply to interpersonal coordination during gait in a straightforward manner. When the typically involved parameter constraints are relaxed, however, this model may largely account for the observed dynamical characteristics.

Pelvis-thorax coordination in the transverse plane during gait

The coordination between horizontal pelvic and thoracic rotations during treadmill walking was studied in ten subjects. Previous studies have considered the relative phase using the mean to characterize coordination mode, and the S.D. as an index of its stability. However, to use S.D. of relative phase as a measure for coordinative stability, the underlying oscillations have to be phase-locked at a certain value. Random fluctuations around this value can then be viewed as stochastic perturbations of a stable fixed point, resulting in a unimodal distribution of relative phase. Using methods of circular statistics this study shows that these conditions were not met in pelvis-thorax coordination. Spectral analyses revealed that, as walking velocity increased, a triphasic component emerged in the pelvic rotations, while the thoracic rotations remained harmonic across all walking velocities. These findings refute the use of standard relative phase measures to capture pelvis-thorax coordination. An alternative measure is introduced, namely the difference between the continuous Fourier phases of the component oscillations as determined for the main frequency of the thorax oscillation. With this measure, pelvis-thorax coordination was found to evolve from in-phase coordination towards antiphase coordination as walking velocity increased. This method may be used to assess reliably the properties of pelvis-thorax coordination in both healthy and pathological gait patterns in the future.

Athletic skill level is reflected in body sway: A test case for accelometry in combination with stochastic dynamics

Recent studies on postural control have shown that the variability of body sway during quiet standing may provide valuable information to characterize changes in postural control due to age, pathology, skill and task. The aim of the present study was to determine - as spade work for possible clinical applications - whether body sway measured with a three-axial accelerometer at the trunk can differentiate between three healthy young populations that differ in athletic skill level. The three groups in question (group size: n=22) consisted of regular bachelor students, physical education students and physical education students specialized in gymnastics. Data were recorded during tandem stance with eyes open or closed and while standing on foam. The acceleration time-series were analysed in anteriorposterior and mediolateral direction. Differences in postural control were quantified in terms of variability, spectral properties and stochastic dynamical measures, i.c., regularity (sample entropy, long-range correlations) and local stability (largest Lyapunov exponent). The results were clear-cut. Standing with eyes closed and on foam increased variability. Compared to standing with eyes open, standing with eyes closed resulted in less regular sway patterns but with greater local stability, whereas standing on foam had an opposite effect. With greater gymnastic skills, acceleration time-series were less variable, less regular and more stable. These results imply that quantifying the stochastic-dynamical structure of postural sway using ambulant accelerometry may provide a useful diagnostic tool.

Online gait event detection using a large force platform embedded in a treadmill

Gait research and clinical gait training may benefit from movement-dependent event control, that is, technical applications in which events such as obstacle appearance or visual/acoustic cueing are (co)determined online on the basis of current gait properties. A prerequisite for successful gait-dependent event control is accurate online detection of gait events such as foot contact (FC) and foot off (FO). The objective of the present study was to assess the feasibility of online FC and FO detection using a single large force platform embedded in a treadmill. Center-of-pressure, total force output and kinematic data were recorded simultaneously in 12 healthy participants. Online FC and FO estimates and spatial and temporal gait parameters estimated from the force platform data--i.e., center-of-pressure profiles--were compared to offline kinematic counterparts, which served as the gold standard. Good correspondence was achieved between online FC detections using center-of-pressure profiles and those derived offline from kinematic data, whereas FO was detected 31 ms too late. A good relative and absolute agreement was achieved for both spatial and temporal gait parameters, which was improved further by applying more fine-grained FO estimation procedures using characteristic local minima in the total force output time series. These positive results suggest that the proposed system for gait-dependent event control may be successfully implemented in gait research as well as gait interventions in clinical practice.

Effects of attention on the control of locomotion in individuals with chronic low back pain

BackgroundPeople who suffer from low back pain (LBP) exhibit an abnormal gait pattern, characterized by shorter stride length, greater step width, and an impaired thorax-pelvis coordination which may undermine functional walking. As a result, gait in LBP may require stronger cognitive regulation compared to pain free subjects thereby affecting the degree of automaticity of gait control. Conversely, because chronic pain has a strong attentional component, diverting attention away from the pain might facilitate a more efficient walking pattern.MethodsTwelve individuals with LBP and fourteen controls participated. Subjects walked on a treadmill at comfortable speed, under varying conditions of attentional load: (a) no secondary task, (b) naming the colors of squares on a screen, (c) naming the colors of color words (color Stroop task), and (d) naming the colors of words depicting motor activities. Markers were attached to the thorax, pelvis and feet. Motion was recorded using a three-camera SIMI system with a sample frequency of 100 Hz. To examine the effects of health status and attention on gait, mean and variability of stride parameters were calculated. The coordination between thoracic and pelvic rotations was quantified through the mean and variability of the relative phase between those oscillations.ResultsLBP sufferers had a lower walking speed, and consequently a smaller stride length and lower mean thorax-pelvis relative phase. Stride length variability was significantly lower in the LBP group but no significant effect of attention was observed. In both groups gait adaptations were found under performance of an attention demanding task, but significantly more so in individuals with LBP as indicated by an interaction effect on relative phase variability.ConclusionGait in LBP sufferers was characterized by less variable upper body movements. The diminished flexibility in trunk coordination was aggravated under the influence of an attention demanding task. This provides further evidence that individuals with LBP tighten their gait control, and this suggests a stronger cognitive regulation of gait coordination in LBP. These changes in gait coordination reduce the capability to deal with unexpected perturbations, and are therefore maladaptive.

Rhythm perturbations in acoustically paced treadmill walking after stroke

Background. In rehabilitation, acoustic rhythms are often used to improve gait after stroke. Acoustic cueing may enhance gait coordination by creating a stable coupling between heel strikes and metronome beats and provide a means to train the adaptability of gait coordination to environmental changes, as required in everyday life ambulation. Objective. To examine the stability and adaptability of auditory—motor synchronization in acoustically paced treadmill walking in stroke patients. Methods. Eleven stroke patients and 10 healthy controls walked on a treadmill at preferred speed and cadence under no metronome, single-metronome (pacing only paretic or nonparetic steps), and double-metronome (pacing both footfalls) conditions. The stability of auditory—motor synchronization was quantified by the variability of the phase relation between footfalls and beats. In a separate session, the acoustic rhythms were perturbed and adaptations to restore auditory—motor synchronization were quantified. Results. For both groups, auditory—motor synchronization was more stable for double-metronome than single-metronome conditions, with stroke patients exhibiting an overall weaker coupling of footfalls to metronome beats than controls. The recovery characteristics following rhythm perturbations corroborated the stability findings and further revealed that stroke patients had difficulty in accelerating their steps and instead preferred a slower-step response to restore synchronization. Conclusions. In gait rehabilitation practice, the use of acoustic rhythms may be more effective when both footfalls are paced. In addition, rhythm perturbations during acoustically paced treadmill walking may not only be employed to evaluate the stability of auditory—motor synchronization but also have promising implications for evaluation and training of gait adaptations in neurorehabilitation practice.

Gait in Pregnancy-related Pelvic girdle Pain: amplitudes, timing, and coordination of horizontal trunk rotations

Walking is impaired in Pregnancy-related Pelvic girdle Pain (PPP). Walking velocity is reduced, and in postpartum PPP relative phase between horizontal pelvis and thorax rotations was found to be lower at higher velocities, and rotational amplitudes tended to be larger. While attempting to confirm these findings for PPP during pregnancy, we wanted to identify underlying mechanisms. We compared gait kinematics of 12 healthy pregnant women and 12 pregnant women with PPP, focusing on the amplitudes of transverse segmental rotations, the timing and relative phase of these rotations, and the amplitude of spinal rotations. In PPP during pregnancy walking velocity was lower than in controls, and negatively correlated with fear of movement. While patients’ rotational amplitudes were larger, with large inter-individual differences, spinal rotations did not differ between groups. In the patients, peak thorax rotation occurred earlier in the stride cycle at higher velocities, and relative phase was lower. The earlier results on postpartum PPP were confirmed for PPP during pregnancy. Spinal rotations remained unaffected, while at higher velocities the peak of thorax rotations occurred earlier in the stride cycle. The latter change may serve to avoid excessive spine rotations caused by the larger segmental rotations.

Gait in patients with pregnancy-related pain in the pelvis: an emphasis on the coordination of transverse pelvic and thoracic rotations.

OBJECTIVEnTo quantify gait impairments in women with pregnancy-related pain in the pelvis which persisted post-partum.Design. Nine patients and nine healthy subjects were studied during treadmill walking at different velocities.nnnBACKGROUNDnWalking problems in patients with pregnancy-related pain in the pelvis have been known to exist for a long time. To date, no quantitative gait studies have been conducted in this population.nnnMETHODSnMaximum attainable walking velocity was determined, amplitudes of pelvic and thoracic rotations were calculated, and spectral analysis was used to assess the harmonicity of these rotations. Coordination between pelvic and thoracic rotations was characterized as mean relative Fourier phase and weighted coherence.nnnRESULTSnMaximum attainable walking velocity was highly variable between patients, but on average significantly lower than in healthy controls. Moreover, patients had a significantly lower mean relative Fourier phase (again, highly variable) and higher weighted coherence. The other parameters did not differ significantly between groups.nnnCONCLUSIONSnCoordination between pelvic and thoracic rotations in the transverse plane was affected in patients with pregnancy-related pain in the pelvis. Individual patients may apply different strategies during walking to cope with the underlying problems.nnnRELEVANCEnPregnancy-related pain in the pelvis is poorly understood. Patients with this condition are known to have problems with locomotion. The present study reveals that gait coordination is altered. Theoretically, this underlines the importance of analysing coordination in pathological movement. Clinically, better understanding the gait problems of women with pregnancy-related pain in the pelvis may contribute to more appropriate treatments.