[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to investigate the nature of inter-joint coordination at different levels of skilled performance to: (1) distinguish learners who were successful versus unsuccessful in terms of their task performance; (2) investigate the pathways of change during the learning of a new coordination pattern and (3) examine how the learner's coordination patterns relate to those of experts in the longswing gymnastics skill. Continuous relative phase of hip and shoulder joint motions was examined for longswings performed by two groups of novices, successful (n = 4) and unsuccessful (n = 4) over five practice sessions, and two expert gymnasts. Principal component analysis showed that during longswing positions where least continuous relative phase variability occurred for expert gymnasts, high variability distinguished the successful from the unsuccessful novice group. Continuous relative phase profiles of successful novices became more out-of-phase over practice and less similar to the closely in-phase coupling of the expert gymnasts. Collectively, the findings support the proposition that at the level in inter-joint coordination a technique emerges that facilitates successful performance but is not more like an expert's movement coordination. This finding questions the appropriateness of inferring development towards a "gold champion" movement coordination.
Journal of Sports Sciences 06/2015; DOI:10.1080/02640414.2015.1057209 · 2.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated timing and coordination during the swing phase of swing leg, body center of mass (CoM) and head during walking in n=19 people with multiple sclerosis (MS; n=19) and controls (n=19). The MS group showed differences in swing phase timing at all speeds. At imposed but not preferred speeds, the MS group had less time to prepare for entry into the unstable equilibrium, as the CoM entered this phase of swing earlier. Time-to-contact coupling, quantifying the coordination between the CoM and the swing foot, was not different between groups. The projection of head motion on the ground occurred earlier after toe-off and was positioned closer to the body in the MS group, illustrating increased reliance on visual exproprioception in which vision of the body in relation to the surface of support is established. Finally, prospective control, linking head movements to the swing foot time-to-contact and next step landing area, was impaired in the MS group at higher gait speeds.
Motor control 02/2015; DOI:10.1123/mc.2013-0106 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Excessive pronation, because of its coupling with tibial internal rotation (TIR), has been implicated as a risk factor in the development of anterior knee pain (AKP). Traditionally this coupling has been expressed as a ratio between the eversion range of motion and the TIR range of motion (Ev/TIR) that occurs during stance. Currently, this technique has not been used to evaluate specific injuries or the effects of gender. Additionally, Ev/TIR is incapable of detecting coupling changes that occur throughout stance. Therefore, the purpose of this study was to compare the coupling between eversion and TIR in runners with (n = 19) and without AKP (n = 17) and across gender using the Ev/TIR ratio, and more continuously using vector coding. When using vector coding, significant coupling differences were noted in runners with AKP (34-38% stance), with runners with AKP showing relatively more TIR than eversion. Similarly significant differences were noted across gender (14-25 & 36-47% stance) with males transitioning from a loading to propulsive coordination pattern using a proximal to distal strategy, while female runners used a distal to proximal strategy. These differences were only detected when evaluating this coupling relationship using a continuous technique such as vector coding.
[Show abstract][Hide abstract] ABSTRACT: Background: Clinically, plantar fasciitis (PF) is believed to be a result and/or prolonged by overpronation and excessive loading, but there is little biomechanical data to support this assertion. The purpose of this study was to determine the differences between healthy individuals and those with PF in (1) rearfoot motion, (2) medial forefoot motion, (3) first metatarsal phalangeal joint (FMPJ) motion, and (4) ground reaction forces (GRF). Methods: We recruited healthy (n=22) and chronic PF individuals (n=22, symptomatic over three months) of similar age, height, weight, and foot shape (p > 0.05). Retro-reflective skin markers were fixed according to a multi-segment foot and shank model. Ground reaction forces and three dimensional kinematics of the shank, rearfoot, medial forefoot, and hallux segment were captured as individuals walked at 135 ms(-1). Results: Despite similarities in foot anthropometrics, when compared to healthy individuals, individuals with PF exhibited significantly (p < 0.05) (1) greater total rearfoot eversion, (2) greater forefoot plantar flexion at initial contact, (3) greater total sagittal plane forefoot motion, (4) greater maximum FMPJ dorsiflexion, and (5) decreased vertical GRF during propulsion. Conclusion: These data suggest that compared to healthy individuals, individuals with PF exhibit significant differences in foot kinematics and kinetics. Consistent with the theoretical injury mechanisms of PF, we found these individuals to have greater total rearfoot eversion and peak FMPJ dorsiflexion, which may put undue loads on the plantar fascia. Meanwhile, increased medial forefoot plantar flexion at initial contact and decreased propulsive GRF are suggestive of compensatory responses, perhaps to manage pain.
Journal of Biomechanics 06/2014; 47(11). DOI:10.1016/j.jbiomech.2014.06.003 · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study examined the prospective control of the swing phase in young healthy adults while walking at preferred speed over unobstructed ground and during obstacle clearance. Three aspects of swing were examined: (1) the relation of the body Center of Mass (CoM) to the stability boundaries at the base of support; (2) a dynamic time-to-contact analysis of the CoM and swing foot to these boundaries; and (3) the role of head movements in the prospective control of gait and field of view assessment. The time-to-contact analysis of CoM and swing foot showed less stable swing dynamics in the trail foot compared to the lead foot in the approach to the unstable equilibrium, with the CoM leading the swing foot and crossing the anterior stability boundary before the swing foot. Compensations in temporal coupling occurred in the trail limb during the late swing phase. Time-to-contact analysis of head movement showed stronger prospective control of the lead foot, while fixation of the field of view occurred earlier in swing and was closer to the body in the obstacle condition compared to unobstructed walking. The dynamic time-to-contact analysis offers a new approach to assessing the unstable swing phase of walking in different populations.
Human Movement Science 05/2014; 36. DOI:10.1016/j.humov.2014.04.001 · 2.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Recent literature has related differences in pelvis-trunk coordination to low back pain (LBP) status. In addition, repetitive motions involving bending and twisting have been linked to high incidence of LBP. The purpose of this study was to examine trunk sagittal motion - axial rotation ('bend and twist') coordination during locomotion in three groups of runners classified by LBP status (LBP: current low back pain; RES: resolved low back pain and CTR: control group with no history of LBP). Trunk kinematic data were collected as running speed was systematically increased on a treadmill. Within-segment coordination between trunk sagittal and transverse planes of motion (trunk lean and axial rotation, respectively) was calculated using continuous relative phase (CRP), and coordination variability was defined as the between stride cycle standard deviation of CRP (CRPvar). Bend-twist coordination was more in-phase for the LBP group than CTR (p = 0.010) regardless of running speed. No differences in CRPvar were found between the groups. The results from our coordination (CRP) analysis were sensitive to LBP status and suggest that multi-plane interactions of the trunk should be considered in the assessment of LBP. This analysis also has potential for athletically oriented tasks that involve multi-plane interactions of the trunk, particularly ones that contain asymmetric action, such as sweep rowing or a shot on goal in field hockey or ice hockey.
[Show abstract][Hide abstract] ABSTRACT: Soldier equipment compromises task performance as temporal constraints during critical situations and load increase inertial and interactive forces during movement. Methods are necessary to optimise equipment that relate task performance to underlying coordination and perception-action coupling. Employing ecological task analysis and methods from dynamical systems theory, equipment load and coordination was examined during two sub-tasks embedded in combat performance, threat discrimination and dynamic marksmanship. Perception-action coupling was degraded with load during threat discrimination, leading to delays in functional reaction time. Reduced speed and accuracy during dynamic marksmanship under load was related to disrupted segmental coordination and adaptability during postural transitions between targets. These results show how reduced performance under load relates to coordination changes and perception-action coupling. These changes in functional capability are directly related to soldier survivability in combat. The methods employed may aid equipment design towards more optimised performance by modifying equipment or its distribution on humans. Practitioner Summary: The combat equipment necessary for soldier survival and mission accomplishment significantly impedes task performance. Understanding relations among equipment, task performance, situational awareness and segmental coordination is necessary to define the trade space for design optimisation. This article begins to define this trade space in terms of perception-action coupling and survivability in combat.
[Show abstract][Hide abstract] ABSTRACT: Little biomechanical evidence exists to support the association between excessive foot pronation and anterior knee pain (AKP). One issue could be the way excessive pronation has been defined. Recent evidence has suggested that evaluating pronation in the context of the joint's available range of motion (ROM, anatomical threshold) provides greater insight on when pronation contributes to injury. Theoretically, quantifying the amount of time the joint has to respond before reaching end range (neuromuscular threshold) could provide additional insight. Therefore the purpose of this study was to use a neuromuscular threshold, the time to contact (TtC) the ankle joint complex's ROM boundary, to evaluate runners with and without AKP.
Nineteen healthy and seventeen runners with AKP had their ROM and running biomechanics evaluated. The TtC was calculated using each individual's angular distance from end range (eversion buffer) and eversion velocity. Data were recorded over ten stance phases and evaluated using a one way analysis of variance and 95% confidence intervals.
Runners with AKP had significantly shorter TtC the joint's ROM boundary when compared to healthy runners (64.0ms vs. 35.6ms, p=0.01). While not statistically significant, this shorter TtC was in large part due to having a smaller eversion buffer, however velocity was found to have a substantial influence on the TtC of select individuals. These results provide evidence that a link between pronation and AKP exists when using anatomical and neuromuscular based thresholds.
[Show abstract][Hide abstract] ABSTRACT: The aim of this paper was to present a review on the role that movement variability (MV) plays in the analysis of sports movement and in the monitoring of the athlete's skills. MV has been traditionally considered an unwanted noise to be reduced, but recent studies have re-evaluated its role and have tried to understand whether it may contain important information about the neuro-musculo-skeletal organisation. Issues concerning both views of MV, different approaches for analysing it and future perspectives are discussed. Information regarding the nature of the MV is vital in the analysis of sports movements/motor skills, and the way in which these movements are analysed and the MV subsequently quantified is dependent on the movement in question and the issues the researcher is trying to address. In dealing with a number of issues regarding MV, this paper has also raised a number of questions which are still to be addressed.
[Show abstract][Hide abstract] ABSTRACT: Overuse injuries are generally defined as a repetitive micro-trauma to tissue. Many researchers have associated particular biomechanical parameters as an indicator of such injuries. However, while these parameters have been reported in single studies, in many instances, it has been difficult to verify these parameters as causative to the injury. We have investigated overuse injuries, such as patella-femoral pain syndrome, using a dynamical systems approach. Using such methods, the importance of the structure of coordinative variability (i.e. the variability of the interaction between segments or joints) becomes apparent. We view coordinative variability as functionally important to the movement and different from end-point or goal variability. Using concepts derived from the work of Bernstein, we conducted studies using a continuous relative phase and/or modified vector coding approaches to investigate the coordinative variability of overuse injuries. Consistently, we have found that the higher variability state of a coordinative structure is the healthy state while the lower variability state is the unhealthy or pathological state. It is clear that very high coordinative variability could also result in injury and that there must be a window of 'higher variability' in which non-injured athletes function. While this finding that coordinative variability is functional has been shown in several studies, it is still not clear if reduced variability contributes to or results from the injury. Studies are currently underway to determine the potential reasons for the reduced variability in injured athletes. Nevertheless, our laboratory believes that this understanding of how joints interact can be important in understanding overuse injuries.
Sports Medicine Arthroscopy Rehabilitation Therapy & Technology 11/2012; 4(1):45. DOI:10.1186/1758-2555-4-45
[Show abstract][Hide abstract] ABSTRACT: Variability–stability relationships are the very foundation of flexible biological movements. For footwear design, stability is best defined as pattern stability at the level of segmental relationships with regard to goal-oriented performance. Footwear design should seek to optimize the variation in segmental relationships while maintaining the overall locomotion pattern, providing a system that is both adaptable to upcoming events and stable to unanticipated perturbations. As footwear is designed for a variety of uses other than forward, continuous running on a flat terrain, an examination of the fundamental assumptions and applicability of traditional gait dynamics is necessary. Expanding evaluation of gait dynamics to non-forward, non-continuous motion across different terrains would seem appropriate, given the ubiquity of these movements in everyday life. Optimizing footwear design for different tasks requires trade-offs between design and material selection and a principled scientific approach to understanding these trade-offs is required. Evaluation of these non-traditional gait dynamics and incorporation of goal-oriented performance requires consideration of the behavioural consequences of design and perception–action coupling. Understanding variability–stability relationships remains at the center of any attempt to understand footwear performance and design implications in these expanded gait dynamics. The basis for changing historical perspectives on variability–stability relationships is discussed with regard to maintaining and changing coordinative patterns, information–movement relationships, injury prevention, and optimizing performance through footwear design. A principled approach to building a footwear performance space from empirical data is provided, and it is suggested that such an approach offers objective metrics for making appropriate trades in footwear design to optimize performance across categories of intended use.
[Show abstract][Hide abstract] ABSTRACT: Orientation toward one's surroundings is necessary for prospective control of action, and constraints on orienting activity have consequences for animal survival. Physically coupled load is a constraint for humans wearing protective equipment (firefighters, soldiers, etc.). The consequences of load on postural affordances while transitioning to upright stance was used to quantify the impact of different soldier configurations. Eight participants established upright posture in 4 relevant load configurations (5.0 to 79.2 lb). Load affected the accessibility of optical information at a distance as evidenced by increasing downward head angles and reductions in postural coordination. Reductions in the variability of time to establish upright stance with load suggests a loss of functional adaptability. Load asymmetries played a significant role as the most asymmetric configuration (not the heaviest) had the most detrimental effect on postural affordances. Center of Pressure (CoP) dynamics reflected the consequences of asymmetric loading on postural regulation as greater power and fluctuations across frequencies were observed. Physically coupled load induces significant constraints on orienting activity, and load asymmetry contributes significantly to the detrimental effects of protective equipment on action-perception coupling during whole-body movements.
[Show abstract][Hide abstract] ABSTRACT: To investigate (1) whether previously observed changes in gait parameters in individuals with multiple sclerosis (MS) are the result of slower preferred walking speeds or reflect adaptations independent of gait speed; and (2) the changes in spatiotemporal features of the unstable swing phase of gait in people with MS.
Cross-sectional study assessing changes in gait parameters during preferred, slow (0.6m/s), medium (1.0m/s), and fast (1.4m/s) walking speeds.
Gait laboratory with instrumented walkway and motion capture system.
MS group with mild to moderate impairment (n=19, 16 women) with a median Expanded Disability Status Scale score of 3.75 (range, 2.5-6), and a sex- and age-matched control group (n=19).
Gait speed, stride length, stride width, cadence, dual support time, swing time, and timing of swing foot and body/head center of mass during swing phase.
Individuals with MS walked at slower preferred speeds with longer dual support times compared with controls. In fixed-speed conditions, dual support times were longer and swing times were shorter in MS compared with controls. Stride width was wider for all speed conditions in the MS group. In fixed-speed conditions, the MS group positioned their head and body centers of mass closer to the anterior base of support boundary when entering the unstable equilibrium of the swing phase.
Longer dual support time is part of a gait strategy in MS that is apparent even when controlling for the confounding effect of slower preferred speed. However, a gait strategy featuring longer dual support times may have limitations if potentially destabilizing swing dynamics exist, which especially occur at walking speeds other than preferred for people with MS.
Archives of physical medicine and rehabilitation 03/2012; 93(9):1637-42. DOI:10.1016/j.apmr.2012.02.019 · 2.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: During stance, head extension increases postural sway, possibly due to interference with sensory feedback. The sit-to-stand movement is potentially destabilizing due to the development of momentum as the trunk flexes forward and the body transitions to a smaller base of support. It is unclear what role head orientation plays in the postural and movement characteristics of the sit-to-stand transition. The authors assessed how moving from sitting to standing with head-on-trunk extension compared with moving with the head neutral or flexed, or with moving with the head facing forward in space (which would involve head-on-trunk extension, but not head-in-space extension) in healthy, young participants. Head-on-trunk extension increased center of pressure variability, but decreased movement velocities, movement duration, and trunk flexion compared with flexed and neutral head-on-trunk orientations. Similarities in movement characteristics between head-on-trunk extension and the forward head-in-space orientation suggest that stabilizing the head in space does not fully counteract the postural and movement changes due to head-on-trunk extension. Findings suggest that proprioceptive feedback from the neck muscles contributes to the regulation of posture and movement, and therefore should not be overlooked in research on the role of sensory feedback in postural control.
Journal of Motor Behavior 11/2011; 43(6):491-8. DOI:10.1080/00222895.2011.631954 · 1.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Studies have suggested that proper postural control is essential for the development of reaching. However, little research has examined the development of the coordination between posture and manual control throughout childhood. We investigated the coordination between posture and manual control in children (7- and 10-year-olds) and adults during a precision fitting task as task constraints became more difficult. Participants fit a block through an opening as arm kinematics, trunk kinematics, and center of pressure data were collected. During the fitting task, the precision, postural, and visual constraints of the task were manipulated. Young children adopted a strategy where they first move their trunk toward the opening and then stabilize their trunk (freeze degrees of freedom) as the precision manual task is being performed. In contrast, adults and older children make compensatory trunk movements as the task is being performed. The 10-year-olds were similar to adults under the less constrained task conditions, but they resembled the 7-year-olds under the more challenging tasks. The ability to either suppress or allow postural fluctuations based on the constraints of a suprapostural task begins to develop at around 10 years of age. This ability, once developed, allows children to learn specific segmental movements required to complete a task within an environmental context.