Relative Phase Variability Research Articles

Relationship between coordination variability and Osgood-Schlatter disease in male junior youth soccer players -cross-sectional study using an inertial measurement unit-

BackgroundOsgood-Schlatter disease is a common overuse injury, and motor coordination is discussed as a risk factor; however, no reports have examined motor coordination in young soccer players with Osgood-Schlatter disease. This study aimed to investigate the difference in motor coordination between Osgood-Schlatter disease-affected and non-affected soccer players on a junior youth soccer team. MethodsThis cross-sectional study investigated 35 young soccer players of 12–15 years of age, who completed a self-administered questionnaire covering general information, injury history, and athletic experience. An inertial measurement unit was attached to the participant's thoracic spine, lumbar spine, pelvis, thigh, and lower leg. The sagittal plane tilt angle of each body segment during squatting was analyzed. The continuous relative phase was calculated using the sagittal plane tilt angle. The mean absolute relative phase and continuous relative phase variabilities were calculated and compared between Osgood-Schlatter disease-affected and non-affected players. FindingsThe sagittal plane tilt angle of each body segment during static standing and maximum flexion did not differ between the two groups. However, the Osgood-Schlatter disease group had significantly less continuous relative phase variability between the lumbar spine and pelvis (P < 0.01, Cohen's d = 0.91). The Osgood-Schlatter disease group had significantly fewer participants with other sports experience (P = 0.032, φ = 0.36). InterpretationDysfunctional lower trunk and hip muscles may be leading to Osgood-Schlatter disease. It is suggested that a variety of physical activities should be performed in the junior age group to allow players to acquire a variety of movement patterns.

Effects of rowing stroke rates on lower extremity intra-joint coordination variability in experienced young rowers.

The purpose of this study was to examine the effects of rowing stroke rates on lower extremity intra-joint coordination variability in professional rowers. Fifteen experienced young rowers volunteered to participate in this study. Kinematic data were recorded at different rowing speeds with seven Vicon cameras. The continuous relative phase (CRP) and CRP variability (CRPV) were used to calculate joint coordination and coordination variability, respectively, for the hip, knee, and ankle in the sagittal and horizontal planes, and a comparison was made among different rowing stroke rates. A vector analysis repeated measure ANOVA using statistical parametric mapping revealed that there were statistically significant differences in the hip-ankle, hip-knee, and knee-ankle CRPs for rowing at different stroke rates. Moreover, there was higher CRPV in the mid-drive and mid-recovery phases and less variability in the transition from the drive phase to the recovery phase. The results demonstrate the importance of knee joint in rowing tasks in experienced rowers during submaximal rowing stroke rate and the shift of movement to the hip at higher rowing stroke rate. Moreover, there was a smaller variability during drive-to-recovery transition, which may suggests an increased risk for overuse injuries.

Effects of aging on arm coordination at different walking speeds

BackgroundPrevious work has shown that the mean continuous relative phase and coordination variability of lower limbs are modified in older adults when walking. Research questionHere, we propose to understand the extent to which such control mechanisms for upper limbs are present during gait. Specifically, we seek to understand if aging and gait speed constraints influence the interjoint control of upper limbs during walking. MethodsThis observational study evaluated thirty-three participants, divided into older (n = 20, age 66.4 ± 4.3 years; mass: 77.2 ± 14.2 kg; height: 165 ± 9.20 cm) and young adults (n = 13, age 29.5 ± 4.7 years; mass 75.5 ± 9.6 kg; height: 172 ± 6.24 cm) were asked to walk at 0.28, 0.83, 1.38 m.s−1 on a level treadmill while their segmental movements were simultaneously registered with 3D motion capture system. We calculated the mean continuous relative phase and coordination variability (continuous relative phase variability) in elbow-shoulder and shoulder-hip pairs, and a generalized estimating equation was used to test the main and interaction effects of age and speed. ResultsOlder adults had a reduced continuous relative phase (more in-phase coordination) of upper limbs at whole stance for elbow-shoulder, at loading response for shoulder-hip, at mid-stance and terminal stance for elbow-shoulder and shoulder-hip in comparison to young adults at different speeds (p < 0.05). The coordination variability of upper limbs was greater (higher continuous relative phase variability) in older than young adults at 0.28 and 1.38 m.s−1. SignificanceThese findings substantiate the altered motor control role of upper limbs in gait aging, suggesting that lower self-selected speed may be related to the reduced ability to control arm movement during the intermediate phases of gait.

The effect of elastic and viscous force fields on bimanual coordination

Bimanual in-phase and anti-phase coordination modes represent two basic movement patterns with distinct characteristics—homologous muscle contraction and non-homologous muscle contraction, respectively. A method to understand the contribution of each limb to the overall coordination pattern involves detuning (Δω) the natural eigenfrequency of each limb. In the present experiment, we experimentally broke the symmetry between the two upper limbs by adding elastic and viscous force fields using a Kinarm robot exoskeleton. We measured the effect of this symmetry breaking on coordination stability as participants performed bimanual in-phase and anti-phase movements using their left and right hand in 1:1 frequency locking mode. Differences between uncoupled frequencies were manipulated via the application of viscous & elastic force fields and using fast and slow oscillation frequencies with a custom task developed using the Kinarm robotic exoskeleton. The effects of manipulating the asymmetry between the limbs were measured through the mean and variability of relative phase (ϕ) from the intended modes of 0 ° or 180 °. In general, participants deviated less from intended phase irrespective of coordination mode in all matched conditions, except for when elastic loads are applied to both arms in the anti-phase coordination. Second, we found that when force fields were mismatched participants exhibited a larger deviation from the intended phase. Overall, there was increased phase deviation during anti-phase coordination. Finally, participants exhibited higher variability in relative phase in mismatched force conditions compared to matched force conditions, with overall higher variability during anti-phase coordination mode. We extend previous research by demonstrating that symmetry breaking caused by force differences between the limbs disrupts stability in each coordination mode.

Acute effects of Kinesio Taping on lower-limb coordination of gait in hemiplegic patients

BackgroundKinesio taping can effectively strengthen weakened muscles, increase walking speed, and improve dynamic balance in hemiplegic patients, but its effect on lower-limb coordination is not clear. Improving lower-limb coordination in hemiplegic patients can decrease risk of fall during walking. Research questionThis study utilized continuous relative phase to depict the pattern and variability of lower-limb coordination in hemiplegic patients and healthy subjects during walking, and investigate whether it has the acute effect of Kinesio Taping on lower-limb coordination in hemiplegic patients during walking. MethodsGait was measured by a three-dimensional motion capture system for 29 hemiplegic patients (KT group) and 15 healthy subjects (control group). Mean continuous relative phase (MCRP) and mean continuous relative phase variability (MCRPV) were calculated to describe and evaluate lower-limb coordination. ResultsKT intervention only changed the coordination between the bilateral ankle joints in hemiplegic patients. Before the intervention, the MCRP of the two ankles (AA-MCRP) in the stance period of the control group was greater than the KT group (P < 0.001), the MCRPV of the two ankles (AA-MCRPV) in the swing period was lower than that in KT group (P < 0.001). After the intervention, the AA-MCRP in the stance period of the KT group increased (P < 0.001), the AA-MRPV in the swing period of KT group significantly decreased (P = 0.001). SignificanceImmediate ankle KT intervention can result in the in-phase or anti-phase coordination between the two ankles developing to out-of-phase coordination during the stance period of the affected limb during walking, and increase the stability of the out-of-phase coordination between the two ankles during the swing period of the affected limb. KT can be used in rehabilitation treatment for hemiplegic patients to improve acute coordination between the patients' ankles.

Margins of stability and trunk coordination during Nordic walking

Although it has already been demonstrated that Nordic walking has some peculiar biomechanical features with respect to walking, the effects on balance and trunk coordination are still unknown. Our aim here was to compare margins of stability, hip stabilizer muscle activation and scapular-pelvis coordination (mean and variability of continuous relative phase) between walking and two different pole walking techniques (observational design). Eleven Nordic walking instructors were asked to walk at 5.5 km·h−1 on a flat treadmill while 1) walking, 2) Nordic walking and 3) pole walking with just elbow flexion–extension motion allowed and constrained shoulder motion (elbow technique). The 3D movements of limbs and poles were measured by an optoelectronic motion capture system, and gluteus medius activation was measured through surface electromyography. Both techniques using poles show larger mediolateral margins of stability and similar anterior-posterior margins of stability in comparison with walking (p < 0.001). The larger mediolateral margin of stability using poles (conditions 2 and 3) is accompanied by greater trunk coordination stability (greater continuous relative phase variability) than walking. Although the Nordic walking (condition 2) technique results in a similar range of scapular and pelvis transverse rotation, the general pattern of scapular-pelvis coordination was temporally delayed by approximately 20% of the gait cycle in relation to other conditions (1 and 3). In conclusion, Nordic walking provides enhanced mediolateral support and coordination stability of trunk compared with walking, suggesting that it could be proposed as a safer exercise modality than walking.

Lumbopelvic coordination while walking in service members with unilateral lower limb loss: Comparing variabilities derived from vector coding and continuous relative phase

BackgroundContinuous relative phase and vector coding are two common approaches for quantifying lumbopelvic coordination and variability. Evaluating the application of such methodologies to the lower limb loss population is important for better understanding reported asymmetrical movement dynamics of the lumbopelvic region. Research QuestionHow do coordination variabilities derived from trunk-pelvic coupling angles and continuous relative phases compare among individuals with and without unilateral lower limb loss walking at self-selected speeds? MethodsFull-body kinematics were obtained from thirty-eight males with unilateral lower limb loss (23 transtibial and 15 transfemoral) and fifteen males without limb loss while walking along a 15 m walkway. Coordination variabilities were derived from trunk-pelvic coupling angles and continuous relative phases and compared using a multivariate approach, as well as in unilateral outcome measures between control participants and participants with lower limb loss. ResultsOverall, tri-planar measures of continuous relative phase variability were 19–43% larger compared to coupling angle variabilities for individuals without limb loss and individuals with transtibial limb loss. Individuals with transfemoral limb loss had 27% and 31% larger sagittal and transverse variabilities from continuous relative phases compared to coupling angles, respectively. During both prosthetic and intact limb stance, individuals with transtibial limb loss had 19–35% greater tri-planar measures of continuous relative phase variability compared to coupling angle variabilities. During intact stance phase, tri-planar measures of continuous relative phase variability were 27%− 42% larger compared to coupling angle variabilities for individuals without limb loss. SignificanceWhile both methods provide valid estimates of lumbopelvic movement variability during gait, continuous relative phase variability may provide a more sensitive estimate in the lower limb loss population capturing velocity-specific motions of the trunk and pelvis.

Effect of badminton shoe sole on the lunge skill performance: in the viewpoint of coordination

Badminton lunge requires rapid coordination between the knee and ankle joints and it is accompanied by fast contact between the shoe’s sole and the floor. Phase angle analysis is a protocol with high resolution and relating to the coordination, but how the shoe’s sole would affect the lunge performance was not clear in terms of coordination. Thereby, the aim of this study was to applied phase angle analysis to insight the lunge process, then to disclose the effect of badminton shoe’s sole on the lunge skill performance. Eleven elite badminton players performed five left-forward maximum lunge trials with wearing Rounded Heel Shoe (RHS), Flattened Heel Shoe (FHS), and Standard Heel Shoes (SHS). The motion capturing system was used to measure the knee and ankle kinematics information. The Phase Angle (PA), continuous relative phase (CRP) and variability of continuous relative phase (VCRP) between the knee and ankle joints were then calculated for both forward lunge phase and recovery phase in each of the three shoes. Current findings indicated that players wearing RHS had certain advantages on better movement coordination than other shoes, as indicated by better PA and CRP. The findings of this study would be helpful to understand the coordination of badminton lunges and explain the synergy between the lower extremity ankle and knee joint to minimize the possibility of injury in badminton. Furthermore, the coordination between the knee and ankle joints was greatly affected by the structure of the shoe heel design.

Coordination of lower limbs in patients with knee osteoarthritis during walking

BackgroundThe movement coordination in patients with knee osteoarthritis may be impaired and the identification of the deficits in lower limb inter-segmental coordination is crucial to understand the effect of knee osteoarthritis on knee function. Research questionThis study utilizes continuous relative phase to investigate the pattern and variability of lower limb inter-segmental coordination in patients with knee osteoarthritis and in healthy subjects during walking, and to evaluate inter-segmental coordination alterations in patients. MethodsGait was measured by a three-dimensional motion capture system for 44 patients with late-stage knee osteoarthritis and 22 healthy subjects. Segmental kinematic parameters, continuous relative phase and its variability were calculated. Independent samples t-tests were used to detect differences between patients and healthy subjects. ResultsThigh-shank continuous relative phase of patients is significantly decreased by 16.04° and 16.18° during late stance and swing phase as compared with healthy subjects (P < 0.05). Shank-foot continuous relative phase of patients is significantly decreased by 6.89° during early stance and significantly increased by 5.49° and 6.39° during late stance and swing phase (P < 0.05). Patients also exhibit increased variability of thigh-shank continuous relative phase during late stance and swing phase by 1.90° and 1.65° respectively, and increased variability of shank-foot continuous relative phase during early stance and swing phase by 0.83° and 0.88° respectively as compared to healthy subjects (P < 0.05). SignificancePatients with knee osteoarthritis exhibit altered coordination patterns and increased coordination variability of thigh-shank and shank-foot. Knee dysfunction results in altered lower limbs coordination and unstable motor control during walking. Investigation of inter-segmental coordination could therefore provide insights into changes in neuromuscular control of gait in patients with knee osteoarthritis.

The construction of common treadmills significantly affects biomechanical and metabolic variables

ABSTRACT Surface compliance has been shown to affect leg stiffness and energetics. It is unknown if compliance differences between common treadmills would elicit such changes. Therefore, the purpose of this study was to determine if compliance design differences of common treadmills would affect the mechanics and energetics of running. Eleven runners ran at moderate, self-selected, matched belt speeds for three minutes on two treadmills: compliant (CT) and rigid (RT) decks. During the last minute of each trial, oxygen consumption and six markers describing the torso, thigh, shank and foot, and one marker to determine treadmill deflection were recorded. Leg stiffness, continuous relative phase (CRP) and CRP variability were calculated. Compared to RT, running on CT resulted in a significantly more compliant leg (8.591 kN•m−1 > 9.063 kN•m−1), lower oxygen consumption (34.69 ml•kg−1•min−1 < 36.86 ml•kg−1•min−1), different coordination patterns and greater variability, particularly during the push-off phase. These results are inconsistent with the literature because the deck of CT rebounds back at the runner during the absorption phase and away from the runner during the push-off phase. Therefore, care should be taken when using treadmills for research and comparing mechanical and energetic measures between studies.

Lesser magnitudes of lower extremity variability during terminal swing characterizes walking patterns in children with autism

BackgroundAnecdotally, children with Autism Spectrum Disorder have highly variable lower extremity walking patterns, yet, this has not been sufficiently quantified. As such, the purpose of this study was to examine walking pattern variability by way of lower extremity coordination and spatio-temporal characteristics in children with autism compared with individuals with typical development during over-ground walking. MethodsBilateral continuous relative phase variability was computed for the thigh-leg, leg-foot, and thigh-foot segment couples for 11 children with autism and 9 children with typical development at each gait sub-phase. Furthermore, left and right stride lengths and stride width were computed and compared. The Model Statistic was utilized to test for statistical differences in variability between each child with autism to an aggregate group with typical development. Effect sizes were computed to determine the meaningfulness between responses for children with autism and typical development. Coefficient of variation and effect sizes were computed for stride lengths and stride width. FindingsAnalysis revealed that children with autism exhibited differences in variability in each gait sub-phase. Notably, all but two children with autism exhibited lesser variability in all segment couples during terminal swing. Differences in stride lengths were relatively minimal, however, greater coefficient of variation magnitudes in stride width were observed in children with autism. InterpretationThis finding reveals that children with autism may have limited or a preferred movement strategy when preparing the foot for ground contact. The findings from this study suggest variability may be an identifiable characteristic during movement in children with autism.

Leg-amplitude differentiation guided by haptic and visual feedback to detect alterations in motor flexibility due to Total Knee Replacement.

Following total knee replacement (TKR), patients often persist in maladaptive motor behavior which they developed before surgery to cope with symptoms of osteoarthritis. An important challenge in physical therapy is to detect, recognize and change such undesired movement behavior. The goal of this study was to measure the differences in clinical status of patients pre-TKR and post-TKR and to investigate if differences in clinical status were accompanied by differences in the patients'' motor flexibility. Eleven TKR participants were measured twice: pre-TKR and post-TKR (twenty weeks after TKR). In order to infer maladaptation, the pre-TKR and post-TKR measurements of the patient group were separately compared to one measurement in a control group of fourteen healthy individuals. Clinical status was measured with the Visual Analogue Scale (VAS) for pain and knee stiffness and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Furthermore, Lower-limb motor flexibility was assessed by means of a treadmill walking task and a leg-amplitude differentiation task (LAD-task) supported by haptic or visual feedback. Motor flexibility was measured by coordination variability (standard deviation (SD) of relative phase between the legs) and temporal variability (sample entropy) of both leg movements. In the TKR-group, the VAS-pain and VAS- stiffness and the subscales of the KOOS significantly decreased after TKR. In treadmill walking, lower-limb motor flexibility did not significantly change after TKR. Between-leg coordination variability was significantly lower post-TKR compared to controls. In the LAD-task, a significant decrease of between-leg coordination variability between pre-TKR and post-TKR was accompanied by a significant increase in temporal variability. Post-TKR-values of lower-limb flexibility approached the values of the control group. The results demonstrate that a clinically relevant change in clinical status, twenty weeks after TKR, is not accompanied by alterations in lower-limb motor flexibility during treadmill walking but is accompanied by changes in motor flexibility towards the level of healthy controls during a LAD-task with visual and haptic feedback. Challenging patients with non-preferred movements such as amplitude differentiation may be a promising tool in clinical assessment of motor flexibility following TKR.

Sex differences in lower extremity coordinative variability during running

BackgroundDifferences in coordinative variability have been previously reported between healthy and injured runners. Many running-related injuries have a sex bias, particularly patellofemoral pain (PFP), as female runners are approximately twice as likely to develop PFP compared to males. However, very little is currently known regarding sex differences in coordinative variability during running. Research QuestionAre there sex differences in continuous relative phase (CRP) variability for pelvis-thigh and thigh-shank couplings during the stance phase of running? MethodsPelvis, thigh, and shank segment kinematics were collected on 15 female and 15 male subjects during overground running at a self-selected easy pace (2.39–3.56 m/s) using a 10-camera 3D motion capture system. Continuous relative phase (CRP) variability was calculated between the pelvis-thigh and thigh-shank, and averaged during four distinct stance sub-phases. A mixed effects linear model compared CRP variability between sexes at each stance sub-phase. ResultsCompared to males, females displayed significantly lower pelvis-thigh CRP variability in the transverse plane during the loading response phase, and significantly lower thigh-shank CRP variability in the sagittal plane during the loading response and pre-swing phases. SignificanceLower coordinative variability in females during the loading response for two couplings may provide additional insight into the sex bias for developing certain running-related injuries. However, any injury implications from these results are speculative and should be interpreted with caution.

Influence of Aging on Lower Extremity Sagittal Plane Variability During 5 Essential Subphases of Stance in Male Recreational Runners.

Interjoint coordination variability is a measure of the ability of the human system to regulate multiple movement strategies. Normal aging may reduce variability, resulting in a less adaptive system. Additionally, when older runners are asked to run at speeds greater than preferred, this added constraint may place older runners at greater risk for injury. To examine the influence of normal aging on coordination variability across 5 distinct subphases of stance in runners during preferred and fixed speeds. Twelve older (60 years of age or older) and 12 younger (30 years of age or younger) male recreational runners volunteered for this cross-sectional study. Three-dimensional gait analyses were collected at preferred and fixed speeds. Stance phase was divided into 5 subphases: (SP1) loading response, (SP2) peak braking, (SP3) peak compression, (SP4) midstance, and (SP5) peak propulsion. Continuous relative phase variability for sagittal plane joint pairs-hip-knee, knee-ankle, and hip-ankle-was calculated. Repeated-measures linear mixed models were employed to compare variability for each joint pair. An age-by-stance subphase interaction was found for knee-ankle (P<.01) and hip-ankle (P<.01) pairs, while main effects for age and stance subphase were found for the hip-knee pair (P<.05). Specifically, loading response and peak braking variability were lower in older runners and greater across stance for knee-ankle and hip-ankle pairs, while midstance was lowest in the hip-knee pair for older and younger runners. No effects for running pace were found. Less adaptive movement strategies seen in older runners may partially contribute to the increased eccentric stresses during periods of high load. J Orthop Sports Phys Ther 2019;49(3):171-179. Epub 30 Nov 2018. doi:10.2519/jospt.2019.8419.

Effects of lumbar tissue viscoelastic changes on lumbar-pelvic motion pattern

Lumbar passive tissue elongation is a potential risk factor for the development of low back pain. In this study, we explored the effect of lumbar passive tissue elongation on lumbar-pelvic coordination pattern during trunk flexion/extension task. Thirteen participants performed 5 trials of trunk flexion/extension task both before and after a lumbar passive tissue elongation protocol. Trunk kinematics were recorded to calculate lumbar–pelvic continuous relative phase (CRP) and CRP variability. Results showed that passive tissue elongation significantly decreased the mean lumbar-pelvic CRP and CRP variability. Our results indicate that prolonged experienced lumbar passive tissue elongation should be avoided in an occupational environment.

Expert monitoring and verbal feedback as sources of performance pressure

The influence of monitoring-pressure and verbal feedback on the performance of the intrinsically stable bimanual coordination patterns of in-phase and anti-phase was examined. The two bimanual patterns were produced under three conditions: 1) no-monitoring, 2) monitoring-pressure (viewed by experts), and 3) monitoring-pressure (viewed by experts) combined with verbal feedback emphasizing poor performance. The bimanual patterns were produced at self-paced movement frequencies. Anti-phase coordination was always less stable than in-phase coordination across all three conditions. When performed under conditions 2 and 3, both bimanual patterns were performed with less variability in relative phase across a wide range of self-paced movement frequencies compared to the no-monitoring condition. Thus, monitoring-pressure resulted in performance stabilization rather than degradation and the presence of verbal feedback had no impact on the influence of monitoring pressure. The current findings are inconsistent with the predictions of explicit monitoring theory; however, the findings are consistent with studies that have revealed increased stability for the system's intrinsic dynamics as a result of attentional focus and intentional control. The results are discussed within the contexts of the dynamic pattern theory of coordination, explicit monitoring theory, and action-focused theories as explanations for choking under pressure.

The impact of walking speed on interlimb coordination in individuals with Parkinson's disease.

[Purpose] Interlimb coordination can be affected by the symptoms associated with Parkinson’s disease and may result in an increased risk of falls. The purpose of the current study was to compare changes in interlimb coordination in individuals with Parkinson’s disease to healthy older adults while systematically manipulating walking speed. [Subjects and Methods] Participants walked on a treadmill while systematically increasing and decreasing the walking speed between 0.22 and 1.30 m/s. Kinematic data were collected by means of a three dimensional motion capture system. Dependent variables included the phase relation between arm and leg movements as well as between pelvic and thoracic rotation. [Results] Compared to healthy controls, an increased variability in relative phase between left and right arm swing, and smaller amplitude with arm, leg as well as less variability for the phase relation between thoracic and pelvic rotations were shown in individuals with Parkinson’s disease. [Conclusion] The increased variability of phase relation between left and right arm swing may be related to the reduced out-of-phase forcing of the arm movements at the shoulders as a result of axial rigidity in Parkinson’s disease. It deserves further investigation whether the improvement of the coordination between arms could result in the normalization of parkinsonian gait.

Bimanual coordination patterns are stabilized under monitoring-pressure.

The influence of monitoring-pressure on the performance of anti-phase and in-phase bimanual coordination was examined. The two bimanual patterns were produced under no-monitoring and monitoring-pressure conditions at self-paced frequencies. Anti-phase coordination was always less stable than in-phase coordination, with or without monitoring. When performed under monitoring-pressure, the coordination patterns were performed with less variability in relative phase for both patterns across a range of self-paced movement frequencies compared to performance without monitoring. Thus, while monitoring-pressure did induce a behavioral change, it consisted of performance stabilization rather than degradation, a finding inconsistent with explicit-monitoring theory. However, the findings are consistent with the theory of coordination dynamics and studies that have revealed increased stability for the system's intrinsic dynamics as a result of attentional focus and intentional control.

Comparison of Lumbopelvic Coordination between Trunk Flexion and Extension

Lumbopelvic coordination describes the relative contributions of lumbar and pelvis to the total trunk flexion/extension motion, which has been identified as a major influential factor to spinal loading. The current study investigated the differences in lumbopelvic coordination between trunk flexion and extension. Thirteen subjects performed pace-controlled trunk flexion/extension motions in the sagittal plane while lumbopelvic continuous relative phase and phase variability were quantified. The results demonstrated that compared with trunk extension, lumbopelvic continuous relative phase and phase variability were 28% and 117% greater in trunk flexion motion, respectively, which indicated a more anti-phase and unstable coordination pattern. Quantifying these coordination patterns helps identifying abnormal patterns and serves as normative benchmarks during low back pain rehabilitation.

Investigating the effects of movement speed on the lumbopelvic coordination during trunk flexion

Movement speed during trunk flexion has long been reported to affect task performance and biomechanical responses. The current study investigated how movement speed changed lumbopelvic coordination, especially lumbopelvic continuous relative phase and phase variability during trunk flexion. Eighteen subjects executed a paced trunk flexion routine over time periods of 3, 7, 11 and 15seconds. The results demonstrated that compared with the 3-s condition, lumbopelvic continuous relative phase was 98.8% greater in the 15-s condition, indicating a more anti-phase coordination pattern. This pattern is suggested to mitigate the increased spinal loading associated with the longer duration of muscle exertion. Additionally, phase variability was 18.8% greater in the 15-s trials than the 3-s trials, such an unstable coordination pattern is likely caused by the more active neuromuscular control. Findings of this study provide important information about the effects of movement speed on lumbopelvic coordination during trunk flexion.