Human movement science

Publications in this journal

• Article: The effectiveness of voluntary modifications of gait pattern to reduce the knee adduction moment.

  Josien C van den Noort, Ilse Schaffers, Jasper Snijders, Jaap Harlaar
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  ABSTRACT: It has been suggested to use gait modifications in the retraining of patients with knee osteoarthritis (OA), in order to reduce the external knee adduction moment (KAdM). This study focused on the effect of walking speed, foot position and trunk sway, and on the 3D knee moments. Gait analyses of fourteen healthy volunteers were performed in a gait laboratory. Subjects walked at three different speeds in their normal gait pattern, as well as with toe-in and toe-out gait and with medio-lateral trunk sway at a self-selected speed. Fast walking speed increased the KAdM (17-30%) and flexion moment (32%). A slower walking speed did not decrease the KAdM. Toe-in mainly decreased the KAdM (45%) and the transverse moment (38%) during early stance. Toe-out decreased the KAdM during late stance (56%), but increased the KAdM during early stance and midstance (21-24%), due to decreased endorotation of the hip with knee flexion. Trunk sway decreased the KAdM during early stance and midstance (31-33%). Gait modifications mainly affected the KAdM, but changes in sagittal and transverse knee moments and kinematics were also observed. This indicates that, when estimating knee load, taking only the frontal plane kinetics into consideration may lead to erroneous simplifications. No conclusive beneficial effects were found in any of the gait modifications throughout the entire stance phase.
  Human movement science 05/2013;
• Article: EMG and tibial shock upon the first attempt at barefoot running.

  Evan D Olin, Gregory M Gutierrez
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  ABSTRACT: As a potential means to decrease their risk of injury, many runners are transitioning into barefoot running. Habitually shod runners tend to heel-strike (SHS), landing on their heel first, while barefoot runners tend to mid-foot or toe-strike (BTS), landing flat-footed or on the ball of their foot before bringing down the rest of the foot including the heel. This study compared muscle activity, tibial shock, and knee flexion angle in subjects between shod and barefoot conditions. Eighteen habitually SHS recreational runners ran for 3 separate 7-minute trials, including SHS, barefoot heel-strike (BHS), and BTS conditions. EMG, tibial shock, and knee flexion angle were monitored using bipolar surface electrodes, an accelerometer, and an electrogoniometer, respectively. A one-way MANOVA for repeated measures was conducted and several significant changes were noted between SHS and BTS, including significant increases in average EMG of the medial gastrocnemius (p=.05), average and peak tibial shock (p<.01), and the minimum knee flexion angle (p<.01). Based on our data, the initial change in mechanics may have detrimental effects on the runner. While it has been argued that BTS running may ultimately be less injurious, these data indicate that habitually SHS runners who choose to transition into a BTS technique must undertake the process cautiously.
  Human movement science 05/2013;
• Article: Independence and control of the fingers depend on direction and contraction mode.

  Kia Sanei, Peter J Keir
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  ABSTRACT: Both biomechanical and neural factors are suggested to contribute to the limited independence of finger movement and involuntary force production. The purpose of this study was to evaluate finger independence by examining the activity of the four compartments of extensor digitorum (ED) and flexor digitorum superficialis (FDS) and involuntary force production in the non-task fingers using the "enslaving effect" (EE). Twelve male participants performed a series of 5s sub-maximal exertions at 5%, 25%, 50% and 75% of maximum using isometric isotonic and ramp flexion and extension exertions. Ramp exertions were performed from 0% to 85% of each finger's maximum force with ascending and descending phases taking 4.5s. EE was lower in flexion exertions likely due to the higher activity of the antagonist ED compartments counterbalancing the involuntary activation of the non-task FDS compartments. Minimal FDS activity was seen during extension exertions. At forces up to and including 50%, both EE and muscle activity of the non-task compartments were significantly higher in descending exertions than isotonic or ascending exertions. Up to mid-level forces, both finger proximity and contraction mode affect involuntary force production and muscle activation while only finger proximity contributed to finger independence at higher forces.
  Human movement science 05/2013;
• Article: Upper-limb motor control in patients after stroke: Attentional demands and the potential beneficial effects of arm support.

  Annemieke Houwink, Bert Steenbergen, Gerdienke B Prange, Jaap H Buurke, Alexander C H Geurts
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  ABSTRACT: The goal of this study was to investigate the attentional load of using the upper limb in moderately and mildly affected patients after stroke, with and without arm support. Ten patients with stroke (4 mild and 6 moderate paresis) and ten healthy, gender- and age-matched control subjects performed a dual-task experiment that consisted of a circle drawing task and an auditive Stroop task. Complexity of the motor task was manipulated by supporting the arm against gravity. Individual motor (area×speed) and cognitive (accuracy/reaction time) scores during the dual-task conditions were converted into percentage scores relative to the respective single-task scores and then combined in a single measure of net dual-task performance. Without arm support, only moderately affected patients showed significantly greater side differences in dual-task performance to the detriment of the affected upper limb. With arm support, no side differences were found for any of the three groups. Thus, the hypothesis that patients with moderate upper-limb paresis suffer from a lack of automaticity of motor control was substantiated by the dual-task condition. Furthermore, supporting the arm reduced the attentional load of using the affected side.
  Human movement science 04/2013;
• Article: Effects of spatial-memory decay and dual-task interference on perturbation-evoked reach-to-grasp reactions in the absence of online visual feedback.

  Kenneth C Cheng, Jay Pratt, Brian E Maki
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  ABSTRACT: Recent findings suggest that rapid perturbation-evoked reach-to-grasp balance-recovery reactions can be (and often are) guided by visuospatial information stored in working memory. To further our understanding, the present study examined the influence of memory-decay and concurrent cognitive-task performance on the speed, accuracy and effectiveness of these reactions by using liquid-crystal goggles to initiate occlusion of vision at various "recall-delay" times prior to perturbation-onset, in ten healthy young-adults. A small handhold was moved unpredictably to one of four locations 2s prior to vision-occlusion; reactions to recover balance by grasping the handhold were evoked by unpredictable antero-posterior platform-translation perturbations. Recall-delay time (0s/2s/5s/10s) was randomized, and subjects performed a spatial- or non-spatial-memory task during the delay-time in a subset of trials. Consistent with studies of volitional reach-to-grasp, recall-delay led to some reduction in endpoint accuracy; however, unlike those studies, the present results showed no evidence that recall-delay led to slowing of the arm movement. Both spatial and non-spatial cognitive tasks had similar effects (slowing of movement initiation and execution), suggesting these effects were related to generic attentional demands rather than competition for specific resources related to spatial working memory. Further work is needed to determine effects of age-related impairments in visuospatial memory and attentional capacity.
  Human movement science 04/2013;
• Article: Imitation of an action course in preschool and school-aged children: A hierarchical reconstruction.

  Lazhar Labiadh, Marie-Martine Ramanantsoa, Eveline Golomer
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  ABSTRACT: Imitation is commonly considered as a hierarchical process. The current study explored the reproduction of a multi-task course in deferred imitation. Eighty-five children between 3.5 and 7.5 years old were divided into five groups and instructed to watch a live human adult demonstrator who performed simple successive actions, such as walking, jumping, grasping, carrying objects from one location to another through six sessions. After a five-minute delay, the children were individually instructed to reproduce the course. Their responses were videotaped and coded in dichotomous data at two hierarchical levels, namely goals and their spatial location. The main findings showed no improvement in the replication of goals due either to age or trials. However, there was an improvement in the integration of the goals' spatial location over trials. This signifies that imitation is an active reconstruction mechanism hierarchically organized.
  Human movement science 04/2013;
• Article: The relationship between the motor system activation during action observation and adaptation in the motor system following repeated action observation.

  Matthew Ray, Deborah Dewey, Libbe Kooistra, Timothy N Welsh
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  ABSTRACT: Repeated action observation has been shown to alter the cortical representation of the observed movement in the motor system. This change in cortical representation is thought to reflect a motor adaptation to observational training (observational training effect). One factor that may impact the observational training effect is the degree of motor system activation that occurs during the observation of the action (i.e., individual differences in the responsiveness of the motor system during action observation). The present study was conducted to test this hypothesis by assessing the relationship between the change in motor system activity during action observation and the change in cortical representation of action following repeated action observation. To this end, transcranial magnetic stimulation (TMS) was used to evoke contractions of thumb muscles in two different protocols: 1) during the observation of thumb movements to assess the responsiveness of each individual's corticospinal system during action observation; and, 2) after the observation of 1800 thumb movements to assess the amount of adaptation in the representation of the thumb following repeated action observation. The key finding was the significant positive relationship between the level of corticospinal system activation during action observation and the amount of change in the direction of TMS evoked thumb movements. These data support the hypothesized relationship between motor system activation during action observation and the motor systems adaptation following observational training. They are also consistent with the notion that a common neural mechanism underlies these effects.
  Human movement science 04/2013;
• Article: Unilateral and bilateral fatiguing contractions similarly alter postural stability but differently modify postural position on bipedal stance.

  Thierry Paillard, Liliane Borel
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  ABSTRACT: The aim of the present study was to compare the effects of unilateral and bilateral muscle fatigue on bipedal postural control and neuromuscular activities. Nineteen subjects completed bilateral fatiguing contractions (BI group), and seventeen subjects completed unilateral fatiguing contractions (UNI group) of the quadriceps femoris. Postural control, maximal voluntary contraction (MVC) and central activation ratio (CAR) were measured before and after the completion of fatiguing tasks for both groups. Postural control was evaluated by using a force platform, which recorded the center of foot pressure (COP). MVC was quantified with an ergometer and CAR was determined with the superimposed electrical stimulation technique. Spatio-temporal COP parameters were used to evaluate postural stability (displacements of COP) and postural position (coordinates of COP) and a frequency analysis of COP excursions (wavelet transform) was performed to estimate the contribution of different neuronal loops. Postural stability, MVC and CAR were similarly affected after unilateral and bilateral fatiguing contractions. Moreover, the impairment of postural position was higher after unilateral fatiguing contractions than after bilateral fatiguing contractions. The study's results indicated that unilateral and bilateral fatigue equally disturbs postural control as well as central drive. However, unilateral muscle fatigue creates postural asymmetries while bilateral muscle fatigue does not engender any.
  Human movement science 04/2013;
• Article: Object use affects motor planning in infant prehension.

  Annarita Contaldo, Elisabetta Cola, Fabrizio Minichilli, Alessandra Crecchi, Maria Chiara Carboncini, Bruno Rossi, Luca Bonfiglio
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  ABSTRACT: The purpose of this study was to investigate the factors underlying the ability to plan object-oriented grasping movements in the first two years of life. In particular, we were interested in evaluating the relationship between manual motor planning, object use and infant-parent interaction. In order to achieve this aim, grasping behaviors of nineteen healthy infants, aged nine to 25months, were examined during naturalistic play sessions with a standard set of toys. Our main finding was that, regardless of age, infants perform a better manual planning when they use an object in a functional rather than non-functional way, suggesting that the planning of an action also depends on knowing the functional properties of an object. In addition, we found that the ability to use objects in a functional way was strongly affected by infant-parent interaction. Thus, level of object use and environmental role must be taken into account in order to understand the development of manual motor planning.
  Human movement science 04/2013;
• Article: Postural sway in volleyball players.

  Valentina Agostini, Emma Chiaramello, Lorenzo Canavese, Carla Bredariol, Marco Knaflitz
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  ABSTRACT: The aim of this work was to analyze the postural sway of volleyball players in bipedal quiet stance. The center of pressure (CoP) was measured in 46 athletes and 42 non-athlete controls. Each subject was tested in 10 different conditions, 5 with their eyes open and 5 with their eyes closed. Volleyball players showed greater CoP ellipses, suggesting a different model of sensory integration in their postural stability. A multivariate approach to data analysis demonstrated that the postural sway of the two groups was different when the subjects kept their eyes open, but it was not with visual deprivation. This could partially be explained by the better 'dynamic' visual acuity of athletes, since possible ('static') refractive errors were corrected for both groups. Furthermore, we expected that national players, engaged in more intensive training programs, were more different from controls than regional ones, and that defensive players, whose role requires the quickest reaction times, were more different from controls than hitters. Our results confirmed these hypothesis. The protocol presented might be useful to assess the efficacy of intensive sport training programs and/or to select elite players with an aptitude for a specific playing position.
  Human movement science 04/2013;
• Article: Effects of model orientation on the visuomotor imitation of arm movements: The role of mental rotation.

  Daniel Krause, Sven Kobow
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  ABSTRACT: An experiment was conducted to examine whether visual perspective has an effect on visuomotor imitation. The experiment presented varied visual perspectives in terms of spatial disparity between a model and an observer (model-observer-disparity) on six levels. Female participants were asked to imitate different arm movements presented in videos by animated models. These arm movements were elbow-extension-flexion movements with one (lower complexity) or three (higher complexity) reversals of movement direction. The results showed that model-observer-disparity affects spatial trajectories and velocities in the performance of motor imitations. The movements' complexity did not affect orientation dependence. Due to the non-linearity of the data, it is questionable if orientation dependence can be at least partially explained by mental rotation processes or differential ideomotor effects. According to these results, high model-observer-disparity should be avoided when using visual instructions in visuomotor imitation.
  Human movement science 04/2013;
• Article: The effects of an adopted narrow gait on the external adduction moment at the knee joint during level walking: Evidence of asymmetry.

  Brian D Street, William Gage
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  ABSTRACT: The external knee adduction moment is an accurate estimation of the load distribution of the knee and is a valid predictor for the presence, severity and progression rate of medial compartment knee osteoarthritis. Gait modification strategies have been shown to be an effective means of reducing the external adduction moment. The purpose of this study was to test narrow gait as a mechanism to reduce the external adduction moment and investigate if limb dominance affects this pattern. Fifteen healthy male participants (mean age: 23.8 (SD=3.1) years, mean height: 1.8 (SD=0.1) m, and mean body mass: 82.9 (SD=16.1kg) took part in this study. Five walking trials were performed for each of the three different gait conditions: normal gait, toe-out gait, and narrow gait. Adoption of the narrow gait strategy significantly reduced the early stance phase external knee adduction moment compared to normal and toe-out gait (p<.002). However, it was observed that this reduction only occurred in the non-dominant limb. Gait modification can reduce the external knee adduction moment. However, asymmetrical patterns between the dominant and non-dominant limbs, specifically during gait modification, may attenuate the effectiveness of this intervention. The mechanism of limb dominance and the specific roles of each limb during gait may account for an asymmetrical pattern in the moment arm and center of mass displacement during stance. This new insight into how limb-dominance effects gait modification strategies will be useful in the clinical setting when identifying appropriate patients, when indicating a gait modification strategy and in future research methodology.
  Human movement science 04/2013;
• Article: Prediction of postural risk of fall initiation based on a two-variable description of body dynamics: Position and velocity of center of mass.

  Mohammad Hadi Honarvar, Motomu Nakashima
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  ABSTRACT: This research addresses the question: what is the risk of fall initiation at a certain human posture? There are postures from which no one is able to keep their balance and a fall will surely initiate (risk=1), and others from which everyone may regain their stability (risk=0). In other postures, only a portion of people can control their stability. One may interpret risk to chance of a fall to be initiated, and based on the portion of fallers assign a risk value to a given human posture (postural risk). Human posture can be mapped to a point in a 2-dimensional space: the x-v plane, the axes of which are horizontal components of the position and velocity of the center of mass of the body. For every pair of (x, v), the outcome of the balance recovery problem defines whether a person with a given strength level is able to regain their stability when released from a posture corresponding to that point. Using strength distribution data, we estimated the portion of the population who will initiate a fall if starting at a certain posture. A fast calculation approach is also introduced to replace the time-consuming method of solving the recovery problem many times. Postural risk of fall initiation for situations expressed by (x, v) pairs for the entire x-v plane is calculated and shown in a color-map.
  Human movement science 04/2013;
• Article: Performance of remote target pointing hand movements in a 3D environment.

  Yung-Hui Lee, Shu-Kai Wu, Yan-Pin Liu
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  ABSTRACT: In this study, we investigated and modeled the performance of target pointing hand movements in a hand free, touchless 3D environment. The targets had different positions, sizes and distances. Performance measurements included total movement time and movement trajectories. The total movement time consisted of a "primary submovement time" and a "secondary submovement time". Results indicated that the total movement time for targets with depth in the upper part of the spherical framework (3.10s) was shorter than for targets without depth (3.79s). The time for targets without depth in the lower part of the spherical framework (2.94s) was shorter than for targets with depth (3.57s). Within a 3D perspective display, the perception of distance and size depends on its depth position. Our results confirmed the adequacy of the 3D information in the display by showing the longest total movement time was observed for the reach of the "forward" target (3.94s). Fitts' model explained the total movement time (for targets without depth r(2)=.72; for targets with depth r(2)=.72). This study showed that participants navigated the 3D space naturally and could move the cursor using both sequential a axis moving strategy and a straight line moving strategy. Real-life applications of the proposed method include interface design for 3D perspective displays and hand movements in 3D environments.
  Human movement science 04/2013;
• Article: Co-variation between graphic pattern stability and attentional cost: A clue for the difficulty to produce handwritten traces.

  Viviane Kostrubiec, Jeremy Danna, Pier-Giorgio Zanone
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  ABSTRACT: Attentional cost incurred for generating handwritten graphic patterns was investigated using a classic dual-task procedure, in which a concurrent reaction time (RT) task was used as an index of the attentional cost incurred by the primary graphic task. Eight right-handed adults had to trace graphic patterns, characterized by a 0°, 45°, 90°, 135° or 180° relative phase and corresponding to shapes ranging from lines to ellipses to circles, while responding by a key press as fast as possible to an auditory signal. The results evidenced a strong and significant correlation between the stability of the produced pattern and the associated attentional cost. The amplitude of the minor and major axes of the produced ellipsoids decreased with the increase of movement frequency, as expected by nonlinear models of oscillatory pattern generation. These findings pave the way to the study for the (coordinative) processes for letter (mal)formation in cursive handwriting.
  Human movement science 04/2013;
• Article: Contribution of the six major gait determinants on the vertical center of mass trajectory and the vertical ground reaction force

  Chris Hayot, Sophie Sakka, Patrick Lacouture
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  ABSTRACT: Saunders et al. (1953) stated that the introduction of six gait determinants (pelvic rotation, pelvic obliquity, stance knee flexion, foot and ankle mechanisms, and tibiofemoral angle) to a compass gait model (two rigid legs hinged at the hips) provides an accurate simulation of the actual trajectory of the whole body center of mass (CoM). Their respective actions could also explain the shape of the vertical ground reaction force (GRF) pattern. Saunders’ approach is considered as a kinematic description of some features of gait and is subject to debate. The purpose of this study is to realize a rigorous mechanical evaluation of the gait determinants theory using an appropriated mathematical model in which specific experimental data of gait trials are introduced. We first simulate a compass-like CoM trajectory using the proposed 3D mathematical model. Then, factorizing the model to introduce successively the kinematic data related to each gait determinant, we assess their respective contribution to both the CoM trajectory and the pattern of vertical GRF at different gait speeds. The results show that the stance knee flexion significatively decreases the estimated position of the CoM during midstance. Stance knee extension and pelvic obliquity contribute to the appearance of the pattern of vertical GRF during stance. The stance ankle dorsiflexion significatively contributes to CoM vertical excursion and the ankle plantarflexion contributes to the vertical GRF during terminal stance. The largest contribution towards the minimization of the CoM vertical amplitude during the complete gait step appears when considering the foot mechanisms and the pelvic obliquity in the proposed model.
  Human movement science 04/2013; 32(2):279-289.
• Article: Age-related changes in executive control and their relationships with activity performance in handwriting.

  Sara Rosenblum, Batya Engel-Yeger, Yael Fogel
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  ABSTRACT: Deterioration in the frontal and prefrontal cortex associated with executive functions (EF) occurs with age and may be associated with changes in daily performance. The aim of the present study was to describe changes occurring with age in Executive Functions (EF) and handwriting activity, as well as to analyze relationships between age, EF and handwriting performance. The study population included 80 healthy participants (aged 31 to 76+) living in the community. After answering five questions about their writing habits, the participants completed the Behavioral Assessment of the Dysexecutive Syndrome (BADS). In addition, they performed a handwriting task on a digitizer included in the Computerized Penmanship Evaluation Tool (ComPET), which provides kinematic measures of the handwriting process. Significant differences were found between the four age groups for both EF and temporal and spatial handwriting measures. A series of regressions indicated that age predicted 35% of the variance of the BADS profile score (EF control) and 32% of the variance of in-air time while writing. The results of this study indicated age effect on both EF control and handwriting performance. Possible implications for further research and clinical evaluation and intervention are discussed.
  Human movement science 04/2013;