Differentiating lifting technique between those who develop low back pain and those who do not

Gender and body height discriminate spinal movement patterns during lifting and lowering tasks

This study aimed to explore the relationships between gender, anthropometrics, and spinal movement patterns (SMP) during lifting and lowering tasks. Thirty adults lifted and lowered a 15 kg-box using a freestyle, squat, and stoop technique. A stepwise segmentation approach, along with the timing of main inflection points of relative angles, was used to distinguish various spinal movement patterns. Temporal multi-segmental interactions were categorised, and their frequencies were analysed based on segments and lifting techniques. SMP's demonstrated varying associations with gender and anthropometric factors during lifting and lowering phases. Notably, during stoop lifting, females tended towards a bottom-up pattern, contrasting with males' preference for a simultaneous pattern. Cluster analysis highlighted the bottom-up pattern in the thoracic spine as the most prominent discriminating factor among females. This SMP categorisation method holds potential for designing tailored manual material handling strategies and re-evaluating therapeutic and exercise programs in occupational, clinical, and sport contexts.

Analyzing gait data measured by wearable cyborg hybrid assistive limb during assisted walking: gait pattern clustering

Introduction

The wearable cyborg Hybrid Assistive Limb (HAL) is a therapeutic exoskeletal device that provides voluntary gait assistance using kinematic/kinetic gait data and bioelectrical signals. By utilizing the gait data automatically measured by HAL, we are developing a system to analyze the wearer's gait during the intervention, unlike conventional evaluations that compare pre- and post-treatment gait test results. Despite the potential use of the gait data from the HAL's sensor information, there is still a lack of analysis using such gait data and knowledge of gait patterns during HAL use. This study aimed to cluster gait patterns into subgroups based on the gait data that the HAL automatically collected during treatment and to investigate their characteristics.

Methods

Gait data acquired by HAL, including ground reaction forces, joint angles, trunk angles, and HAL joint torques, were analyzed in individuals with progressive neuromuscular diseases. For each measured item, principal component analysis was applied to the gait time-series data to extract the features of the gait patterns, followed by hierarchical cluster analysis to generate subgroups based on the principal component scores. Bayesian regression analysis was conducted to identify the influence of the wearer's attributes on the clustered gait patterns.

Results

The gait patterns of 13,710 gait cycles from 457 treatments among 48 individuals were divided into 5-10 clusters for each measured item. The clusters revealed a variety of gait patterns when wearing the HAL and identified the characteristics of multiple sub-group types. Bayesian regression models explained the influence of the wearer's disease type and gait ability on the distribution of gait patterns to subgroups.

Discussion

These results revealed key differences in gait patterns related to the wearer's condition, demonstrating the importance of monitoring HAL-assisted walking to provide appropriate interventions. Furthermore, our approach highlights the usefulness of the gait data that HAL automatically measures during the intervention. We anticipate that the HAL, designed as a therapeutic device, will expand its role as a data measurement device for analysis and evaluation that provides gait data simultaneously with interventions, creating a novel cybernics treatment system that facilitates a multi-faceted understanding of the wearer's gait.

The Effects of Cadence Manipulation on Joint Kinetic Patterns and Stride-to-Stride Kinetic Variability in Female Runners

Altering running cadence is commonly done to reduce the risk of running-related injury/reinjury. This study examined how altering running cadence affects joint kinetic patterns and stride-to-stride kinetic variability in uninjured female runners. Twenty-four uninjured female recreational runners ran on an instrumented treadmill with their typical running cadence and with a running cadence that was 7.5% higher and 7.5% lower than typical. Ground reaction force and kinematic data were recorded during each condition, and principal component analysis was used to capture the primary sources of variability from the sagittal plane hip, knee, and ankle moment time series. Runners exhibited a reduction in the magnitude of their knee extension moments when they increased their cadence and an increase in their knee extension moments when they lowered their cadence compared with when they ran with their typical cadence. They also exhibited greater stride-to-stride variability in the magnitude of their hip flexion moments and knee extension moments when they deviated from their typical running cadence (ie, running with either a higher or lower cadence). These differences suggest that runners could alter their cadence throughout a run in an attempt to limit overly repetitive localized tissue stresses.

The effect of head movement restriction on the kinematics of the spine during lifting and lowering tasks

This study aimed to examine the effects of head movement restriction on relative angles and their derivatives using the stepwise segmentation approach during lifting and lowering tasks. Ten healthy men lifted and lowered a box using two styles (stoop and squat), with two loads (i.e. 10% and 20% of body weight); they performed these tasks with two instructed head postures [(1) Flexing the neck to keep contact between chin and chest over the task cycle; (2) No instruction, free head posture]. The neck flexion significantly affected the flexion angle of all segments of the spine and specifically the lumbar part. Additionally, this posture significantly affected the derivatives of the relative angles and manifested latency in spine segments movement, that is, cephalad-to-caudad or caudad-to-cephalad patterns. Conclusively, neck flexion as an awkward posture could increase the risk of low back pain during lifting and lowering tasks in occupational environments. Practitioner summary: Little information is available about the effects of neck flexion on other spine segments' kinematics and movement patterns, specifically about the lumbar spine. The result of this experimental study shows that neck flexion can increase the risk of low back pain by increasing lumbar flexion angle and spine awkward posture.

New Insights for the Design of Bionic Robots: Adaptive Motion Adjustment Strategies During Feline Landings

Felines have significant advantages in terms of sports energy efficiency and flexibility compared with other animals, especially in terms of jumping and landing. The biomechanical characteristics of a feline (cat) landing from different heights can provide new insights into bionic robot design based on research results and the needs of bionic engineering. The purpose of this work was to investigate the adaptive motion adjustment strategy of the cat landing using a machine learning algorithm and finite element analysis (FEA). In a bionic robot, there are considerations in the design of the mechanical legs. (1) The coordination mechanism of each joint should be adjusted intelligently according to the force at the bottom of each mechanical leg. Specifically, with the increase in force at the bottom of the mechanical leg, the main joint bearing the impact load gradually shifts from the distal joint to the proximal joint; (2) the hardness of the materials located around the center of each joint of the bionic mechanical leg should be strengthened to increase service life; (3) the center of gravity of the robot should be lowered and the robot posture should be kept forward as far as possible to reduce machine wear and improve robot operational accuracy.

Kinematic characteristics during gait in frail older women identified by principal component analysis

Frailty is associated with gait variability in several quantitative parameters, including high stride time variability. However, the associations between joint kinematics during walking and increased gait variability with frailty remain unclear. In the current study, principal component analysis was used to identify the key joint kinematics characteristics of gait related to frailty. We analyzed whole kinematic waveforms during the entire gait cycle obtained from the pelvis and lower limb joint angle in 30 older women (frail/prefrail: 15 participants; non-frail: 15 participants). Principal component analysis was conducted using a 60 × 1224 input matrix constructed from participants’ time-normalized pelvic and lower-limb-joint angles along three axes (each leg of 30 participants, 51 time points, four angles, three axes, and two variables). Statistical analyses revealed that only principal component vectors 6 and 9 were related to frailty. Recombining the joint kinematics corresponding to these principal component vectors revealed that frail older women tended to exhibit greater variability of knee- and ankle-joint angles in the sagittal plane while walking compared with non-frail older women. We concluded that greater variability of knee- and ankle-joint angles in the sagittal plane are joint kinematic characteristics of gait related to frailty.

Competitive and Recreational Running Kinematics Examined Using Principal Components Analysis

Kinematics data are primary biomechanical parameters. A principal component analysis (PCA) of waveforms is a statistical approach used to explore patterns of variability in biomechanical curve datasets. Differences in experienced and recreational runners' kinematic variables are still unclear. The purpose of the present study was to compare any differences in kinematics parameters for competitive runners and recreational runners using principal component analysis in the sagittal plane, frontal plane and transverse plane. Forty male runners were divided into two groups: twenty competitive runners and twenty recreational runners. A Vicon Motion System (Vicon Metrics Ltd., Oxford, UK) captured three-dimensional kinematics data during running at 3.3 m/s. The principal component analysis was used to determine the dominating variation in this model. Then, the principal component scores retained the first three principal components and were analyzed using independent t-tests. The recreational runners were found to have a smaller dorsiflexion angle, initial dorsiflexion contact angle, ankle inversion, knee adduction, range motion in the frontal knee plane and hip frontal plane. The running kinematics data were influenced by running experience. The findings from the study provide a better understanding of the kinematics variables for competitive and recreational runners. Thus, these findings might have implications for reducing running injury and improving running performance.

Multivariate functional principal component analysis identifies waveform features of gait biomechanics related to early-to-moderate hip osteoarthritis

Clinicians often examine movement patterns to design hip osteoarthritis (OA) interventions, yet traditional biomechanical analyses only report a single timepoint. Multivariate principal component analysis (MFPCA) analyzes the entire waveform (i.e., movement pattern), which clinicians observe to direct treatment. This study investigated hip OA indicators, by (1) employing MFPCA to characterize variance across the hip, knee, and ankle angles in healthy and early-to-moderate hip OA participants; and (2) investigating relationships between these waveform features and hip cartilage health. Bilateral hip magnetic resonance images from 72 participants with Kellgren-Lawrence grades ranging from 0 to 3 were used to calculate mean T _1ρ and T ₂ relaxation times in the femoral and acetabular cartilage. MFPCA was performed on lower-limb gait biomechanics and used to identify primary modes of variation, which were related to T _1ρ and T ₂ relaxation times. Here, a MFPC = mode of variation = waveform feature. In the femoral cartilage, transverse plane MFPCs 3 and 5 and body mass index (BMI) was related to T _1ρ , while MFPC 2 and BMI were related to T ₂ relaxation times. In the acetabular cartilage, sagittal plane MFPC 1 and BMI were related to T _1ρ , while BMI was related to T ₂ relaxation times. Greater internal rotation was related to increased T _1ρ and T ₂ relaxation times in the femoral cartilage, while the greater extension was related to increased T _1ρ relaxation times in the acetabular cartilage. This study established a data-driven framework to assess relationships between multi-joint biomechanics and quantitative assessments of cartilage health and identified waveform features that could be evaluated in future hip OA intervention studies.

The effects of incremental changes in rucksack load on lower extremity joint Kinetic patterns during ruck marching

Injuries are often attributed to ruck marching. Therefore, it is important to examine how load carriage influences gait mechanics. The purpose of this study was to examine how subtle changes in rucksack load influence joint torque patterns during marching. Fourteen Army ROTC cadets marched with light, moderate, and heavy rucksack loads. Kinetic and kinematic data were recorded via an instrumented treadmill and motion capture system and principal component analysis was used to analyse the joint torque waveforms. Cadets exhibited moderate-large increases in knee extension torques during early stance (effect sizes ≥0.45) and small-moderate increases in ankle plantarflexion torques during push off (effect sizes ≥0.23) with each incremental increase in rucksack load. The lighter load also resulted in lower hip extension torques during early stance and flexion torques during late stance, vs. the moderate and heavier loads (effect sizes ≥0.23). It appears that subtle changes in rucksack load influence marching mechanics. Practitioner Summary: The purpose of this study was to examine how relatively subtle changes in rucksack load influence marching mechanics. Army ROTC cadets marched with relatively light, moderate, and heavy rucksack loads. Our results indicate that even subtle changes in rucksack load influence joint torque patterns of the hip, knee, and ankle. Abbreviations: ROTC: reserve officer training corps; RoF: rating-of-fatigue; PC: principal component; ICC: intraclass correlation coefficient; ES: effect size.

Lower Limb Movement Pattern Differences Between Males and Females in Squatting and Kneeling

Movement pattern differences may contribute to differential injury or disease prevalence between individuals. The purpose of this study was to identify lower limb movement patterns in high knee flexion, a risk factor for knee osteoarthritis, and to investigate kinematic differences between males and females, as females typically develop knee osteoarthritis more commonly and severely than males. Lower extremity kinematic data were recorded from 110 participants completing 4 variations of squatting and kneeling. Principal component analysis was used to identify principal movements associated with the largest variability in the sample. Across the tasks, similar principal movements emerged at maximal flexion and during transitions. At maximal flexion, females achieved greater knee flexion, facilitated by a wider base of support, which may alter posterior and lateral tibiofemoral stress. Principal movements also detected differences in movement temporality between males and females. When these temporal differences occur due to alterations in movement velocity and/or acceleration, they may elicit changes in muscle activation and knee joint stress. Movement variability identified in the current study provides a framework for potential modifiable factors in high knee flexion, such as foot position, and suggests that kinematic differences between the sexes may contribute to differences in knee osteoarthritis progression.

Exploring the Application of Pattern Recognition and Machine Learning for Identifying Movement Phenotypes During Deep Squat and Hurdle Step Movements

Background

Movement screens are increasingly used in sport and rehabilitation to evaluate movement competency. However, common screens are often evaluated using subjective visual detection of a priori prescribed discrete movement features (e.g., spine angle at maximum squat depth) and may not account for whole-body movement coordination, or associations between different discrete features.

Objective

To apply pattern recognition and machine learning techniques to identify whole-body movement pattern phenotypes during the performance of exemplar functional movement screening tasks; the deep squat and hurdle step. Additionally, we also aimed to compare how discrete kinematic measures, commonly used to score movement competency, differed between emergent groups identified via pattern recognition and machine learning.

Methods

Principal component analysis (PCA) was applied to 3-dimensional (3D) trajectory data from participant's deep squat (DS) and hurdle step performance, identifying emerging features that describe orthogonal modes of inter-trial variance in the data. A gaussian mixture model (GMM) was fit and used to cluster the principal component scores as an unsupervised machine learning approach to identify emergent movement phenotypes. Between group features were analyzed using a one-way ANOVA to determine if the objective classifications were significantly different from one another.

Results

Three clusters (i.e., phenotypes) emerged for the DS and right hurdle step (RHS) and 4 phenotypes emerged for the left hurdle step (LHS). Selected discrete points commonly used to score DS and hurdle step movements were different between emergent groups. In regard to the select discrete kinematic measures, 4 out of 5, 7 out of 7 and 4 out of 7, demonstrated a main effect (p < 0.05) between phenotypes for the DS, RHS, and LHS respectively.

Conclusion

Findings support that whole-body movement analysis, pattern recognition and machine learning techniques can objectively identify movement behavior phenotypes without the need to a priori prescribe movement features. However, we also highlight important considerations that can influence outcomes when using machine learning for this purpose.

Effect of changes in the lumbar posture in lifting on trunk muscle and spinal loads: A combined in vivo, musculoskeletal, and finite element model study

Irrespective of the lifting technique (squat or stoop), the lumbar spine posture (more kyphotic versus more lordotic) adopted during lifting activities is an important parameter affecting the active-passive spinal load distribution. The advantages in either posture while lifting remains, however, a matter of debate. To comprehensively investigate the role on the trunk biomechanics of changes in the lumbar posture (lordotic, free or kyphotic) during forward trunk flexion, validated musculoskeletal and finite element models, driven by in vivo kinematics data, were used to estimate detailed internal tissue stresses-forces in and load-sharing among various joint active-passive tissues. Findings indicated that the lordotic posture, as compared to the kyphotic one, resulted in marked increases in back global muscle activities (~14-19%), overall segmental compression (~7.5-46.1%) and shear (~5.4-47.5%) forces, and L5-S1 facet joint forces (by up to 80 N). At the L5-S1 level, the lordotic lumbar posture caused considerable decreases in the moment resisted by passive structures (spine and musculature, ~14-27%), negligible reductions in the maximum disc fiber strains (by ~0.4-4.7%) and small increases in intradiscal pressure (~1.8-3.4%). Collectively and with due consideration of the risk of fatigue and viscoelastic creep especially under repetitive lifts, current results support a free posture (in between the extreme kyphotic and lordotic postures) with moderate contributions from both active and passive structures during lifting activities involving trunk forward flexion.

Biomechanical analysis of common solid waste collection throwing techniques using OpenSim and an EMG-assisted solver

The solid waste collection industry is one of the most common occupations resulting in low back pain (LBP). Lumbar peak joint reaction forces and peak and integrated moments are strong correlates of LBP. To investigate these risks, this study compared three common waste collection throwing techniques of varying lumbar symmetry: the symmetric (SYM) technique, the asymmetric fixed stance (AFS) technique, and the asymmetric with pivot (AWP) technique. Lumbar moments and joint reaction loads were computed for throwing garbage bags of 3, 7, and 11 kg to quantify the effects that technique and object weight have on LBP risk. LBP risk factors were computed using a full-body musculoskeletal model in OpenSim. Muscle activations were estimated using two methods: the EMG-assisted method, which included electromyography data in the solution, and the conventional static optimization method, which did not. The EMG-assisted method more accurately reproduced measured muscle activation, resulting in significantly larger peak compressive and shear forces (p < 0.05) of magnitudes indicative of LBP risk. Risk factors associated with the SYM technique were either larger or not statistically different compared to the asymmetric techniques for the 3 kg condition; however, the opposite result occurred for the 7 and 11 kg conditions (p < 0.05). These results suggest using rapid, asymmetric techniques when handling lightweight objects and slower, symmetric techniques for heavier objects to reduce LBP risk during waste collection throwing techniques. Results indicating increased risk between asymmetric techniques were mostly inconclusive. As expected, increasing bag mass generally increased LBP risk factors, regardless of technique (p < 0.05).

Muscle force characteristics of male and female collegiate cross-country runners during overground running

Males and females demonstrate unique running mechanics that may contribute to sex-related differences in common running related injuries. Understanding differences in muscle forces during running may inform intervention approaches, such as gait retraining addressing muscle force distribution. The purpose of this study was to compare muscle force characteristics and inter-trial variability between males and females during running. Twenty female and 14 male collegiate cross-country runners were examined. Three-dimensional kinetic and kinematic data were collected during overground running and used to estimate muscle forces via musculoskeletal modelling. Principle components analysis was used to capture the primary sources of variance from the muscle force waveforms. The magnitude of the forces for the hamstrings, gastrocnemius, and soleus muscles were higher across the majority of stance in male runners regardless of footstrike pattern. Males also demonstrated greater inter-trial variability in the timing of the peak gluteus maximus force and the magnitude of local peaks in the gastrocnemius force waveform. Male and female collegiate cross-country runners appear to employ unique lower extremity muscle force characteristics during overground running.

Are there differences in lifting technique between those with and without low back pain? A systematic review

Background and aims

To systemically review the literature to compare freestyle lifting technique, by muscle activity and kinematics, between people with and without low back pain (LBP).

Methods

Five databases were searched along with manual searches of retrieved articles by a single reviewer. Studies were included if they compared a freestyle lifting activity between participants with and without LBP. Data were extracted by two reviewers, and studies were appraised using the CASP tool for case-control studies.

Results

Nine studies were eligible. Heterogeneity did not allow for meta-analysis. Most studies (n = 8 studies) reported that people with LBP lift differently to pain-free controls. Specifically, people with LBP lift more slowly (n = 6 studies), use their legs more than their back especially when initiating lifting (n = 3 studies), and jerk less during lifting (n = 1 studies). Furthermore, the four larger studies involving people with more severe LBP also showed that people with LBP lift with less spinal range of motion and greater trunk muscle activity for a longer period.

Conclusions

People with LBP move slower, stiffer, and with a deeper knee bend than pain-free people during freestyle lifting tasks. Interestingly, such a lifting style mirrors how people, with and without LBP, are often told how to lift during manual handling training. The cross-sectional nature of the comparisons does not allow for causation to be determined.

Implications

The changes described may show embodiment of cautious movement, and the drive to protect the back. There may be value in exploring whether adopting a lifting style closer to that of pain-free people could help reduce LBP.

Identifying generalised segmental acceleration patterns that contribute to ground reaction force features across different running tasks

OBJECTIVES

To support future developments of field-based biomechanical load monitoring tools, this study aimed to identify generalised segmental acceleration patterns and their contribution to ground reaction forces (GRFs) across different running tasks.

DESIGN

Exploratory experimental design.

METHODS

A multivariate principal component analysis (PCA) was applied to a combination of segmental acceleration data from all body segments for 15 team-sport athletes performing accelerated, decelerated and constant low-, moderate- and high-speed running, and 90° cutting trials. Segmental acceleration profiles were then reconstructed from each principal component (PC) and used to calculate their specific GRF contributions.

RESULTS

The first PC explained 48.57% of the acceleration variability for all body segments and was primarily related to the between-task differences in the overall magnitude of the GRF impulse. Magnitude and timing of high-frequency acceleration and GRF features (i.e. impact related characteristics) were primarily explained by the second PC (12.43%) and also revealed important between-task differences. The most important GRF characteristics were explained by the first five PCs, while PCs beyond that primarily contained small contributions to the overall GRF impulse.

CONCLUSIONS

These findings show that a multivariate PCA approach can reveal generalised acceleration patterns and specific segmental contributions to GRF features, but their relative importance for different running activities are task dependent. Using segmental acceleration to assess whole-body biomechanical loading generically across various movements may thus require task identification algorithms and/or advanced sensor or data fusion approaches.

Biomechanical analysis of manual material handling movement in healthy weight and obese workers

The risk of back injury during work remains high today for manual materials handler. The purpose of this study is to identify the potential presence of compensatory strategies in obese and non-obese handlers and evaluate the impact these strategies have on trunk kinematics and kinetics. The biomechanical and ergonomic impacts in 17 obese and 20 healthy-weight handlers were evaluated. The task studied consisted in moving boxes from a conveyor to a hand trolley and back. The results show that the anthropometric characteristics of obese handlers are linked to a significant increase in peak lumbar loading during lifting and lowering of boxes. Few postural differences between the two groups were observed. These results suggest that the excess weight of an obese worker has a significant added effect on the musculoskeletal structures of the back, which exposes obese handlers to a higher risk of developing a musculoskeletal disorder during load handling.

Evaluation of plantar pressures in people with hallux valgus using principal component analysis

BACKGROUND

Foot deformities are serious problems in the elderly as they increase the risk of falling.

OBJECTIVE

This study aimed to examine the relationship between foot plantar pressure during gait and hallux valgus (HV).

METHODS

Foot-pressure data were recorded using an F-scan II system. We analyzed the entire waveform of plantar pressure during gait from 37 healthy adults using principle component analysis (PCA), conducted using a 370 × 357 matrix of time-normalized plantar data of 7 areas during gait (5 gait trials × 2 (both feet) of 37 participants × 51 data points × 7 plantar areas). Two-way (plantar pressure × presence or absence of HV) analyses of variance were conducted on the principal component scores (PCSs) of principal component vectors (PCVs) 1 through 5, each of which exhibited more than 5% variance.

RESULTS

The PCA clarified that the 2nd, 3rd, and 5th PCVs (PCV 2, 3, and 5) were related to HV (p< 0.01). These PCVs exhibit a significant interaction between plantar pressure area and HV presence.

CONCLUSIONS

The larger plantar pressure of the HV group around the hallux area during walking compared with the non-HV group is a dominant difference in plantar pressure features due to HV.

Association between the gait pattern characteristics of older people and their two-step test scores

BACKGROUND

The Two-Step test is one of three official tests authorized by the Japanese Orthopedic Association to evaluate the risk of locomotive syndrome (a condition of reduced mobility caused by an impairment of the locomotive organs). It has been reported that the Two-Step test score has a good correlation with one's walking ability; however, its association with the gait pattern of older people during normal walking is still unknown. Therefore, this study aims to clarify the associations between the gait patterns of older people observed during normal walking and their Two-Step test scores.

METHODS

We analyzed the whole waveforms obtained from the lower-extremity joint angles and joint moments of 26 older people in various stages of locomotive syndrome using principal component analysis (PCA). The PCA was conducted using a 260 × 2424 input matrix constructed from the participants' time-normalized pelvic and right-lower-limb-joint angles along three axes (ten trials of 26 participants, 101 time points, 4 angles, 3 axes, and 2 variable types per trial).

RESULTS

The Pearson product-moment correlation coefficient between the scores of the principal component vectors (PCVs) and the scores of the Two-Step test revealed that only one PCV (PCV 2) among the 61 obtained relevant PCVs is significantly related to the score of the Two-Step test.

CONCLUSIONS

We therefore concluded that the joint angles and joint moments related to PCV 2-ankle plantar-flexion, ankle plantar-flexor moments during the late stance phase, ranges of motion and moments on the hip, knee, and ankle joints in the sagittal plane during the entire stance phase-are the motions associated with the Two-Step test.

Relationships Between Trunk Movement Patterns During Lifting Tasks Compared With Unloaded Extension From a Flexed Posture

OBJECTIVES

The purpose of this study was to investigate between movement patterns of trunk extension from full unloaded flexion and lifting techniques, which could provide valuable information to physical therapists, doctors of chiropractic, and other manual therapists.

METHODS

A within-participant study design was used. Whole-body kinematic and kinetic data during lifting and full trunk flexion were collected from 16 healthy male participants using a 3-dimensional motion analysis system (Vicon Motion Systems). To evaluate the relationships of joint movement between lifting and full trunk flexion, Pearson correlation coefficients were calculated.

RESULTS

There was no significant correlation between the amount of change in the lumbar extension angle during the first half of the lifting trials and lumbar movement during unloaded trunk flexion and extension. However, the amount of change in the lumbar extension angle during lifting was significantly negatively correlated with hip movement during unloaded trunk flexion and extension (P < .05).

CONCLUSIONS

The findings that the maximum hip flexion angle during full trunk flexion had a greater influence on kinematics of lumbar-hip complex during lifting provides new insight into human movement during lifting. All study participants were healthy men; thus, findings are limited to this group.

Principal components analysis to characterise fatigue-related changes in technique: Application to double under jump rope

The upper extremities play an important role in managing the rope-turning technique required to perform continuous double unders. However, acute adaptions in this technique may occur as a jumper fatigues. The purpose of this study was to examine how turning technique is adapted with fatigue. Three-dimensional kinematic data of the upper extremity were collected from 10 trained athletes as they performed consecutive double unders to volitional fatigue. Time series wrist, elbow and shoulder joint angles were calculated where joint angle waveforms representing 10 unique trials from the beginning ("fresh") and end ("fatigued") of the continuous jumping protocol for all participants were analysed using principal component analysis. Participants reported stopping due to cardiovascular and shoulder muscular fatigue. From a kinematics perspective, with fatigue athletes used a more internally rotated range of motion at the shoulder, which we believe prompted a series of more distal adaptions in order to maintain rope turning, preserving consecutive double under performance. The presence of a maladaptive adaptation at the shoulder may increase the risk of developing shoulder injuries. Coaches should consider helping jumpers develop appropriate shoulder muscle endurance such that they can continue to maximise their training and proficiency, while protecting against potential fatigue-related maladaptation.

Age-independent and age-dependent sex differences in gait pattern determined by principal component analysis

Although various studies have reported significant sex differences in pelvic and/or hip-joint motion during normal walking in healthy adults, it is still unclear whether such differences are among the most dominant age-independent sex differences. This study was conducted to analyze the whole waveform of lower-extremity joint kinematics obtained from 191 healthy adults using a principal component analysis (PCA). The PCA was conducted using a 955×1212 input matrix constructed from the participants' time-normalized pelvic and right-lower-limb-joint angles along three axes (five trials of 191 participants×101 data points×4 angles×3 axes). Two-way (age×sex) analyses of variance were conducted on the principal component scores (PCSs) of principal component vectors (PCVs) 1 through 6, each of which explained more than 5% of the variance. We identified a PCV that exhibits a significant age-sex interaction (PCV 1). The characteristics of sex differences reported in previous studies could be observed in the reconstructed waveforms of this PCV. Thus, we can conclude that the sex differences in the gaits reported in previous studies are not consistent across age groups. Furthermore, we also found a PCV that exhibited only a significant sex difference (PCV 6). This PCV was the first and only PCV to exhibit a sex difference without any age-related effect or age-sex interaction. Therefore, we concluded that the movement related to this PCV is age-independent and is the most dominant sex difference in the gaits observed during normal walking.

Gait deviations and compensations in pediatric patients with increased femoral torsion

Coxa antetorta describes an abnormal torsion of the femur. It is commonly considered a cosmetic problem and is treated surgically only in severe cases and the presence of physical complaints. The purpose of this study was to identify deviations in gait kinematics and kinetics in pediatric patients caused by coxa antetorta and to categorize these deviations into primary and secondary deviations. We conducted a retrospective, cross-sectional three-dimensional (3D) gait analysis study to detect gait deviations in adolescents (n = 18; age range 10.5-17.5 years) with coxa antetorta compared to age-matched healthy control subjects (n = 17). Principal component (PC) analysis was used for data reduction. Linear mixed models applied to PC-scores were used to estimate the main effects within retained PCs followed by a post-hoc subgroup analysis. Patients walked with smaller external foot progression angle, greater knee adduction, more internally rotated and flexed hips and greater anterior pelvic tilt. Subgroup analysis revealed that-depending on knee alignment-patients had higher knee and hip adduction moments. These deviations in joint kinematics and kinetics may be associated with physical complaints and accelerated development of osteoarthritis. Assessment of gait deviations related to coxa antetorta using 3D gait analysis may be an additional tool in individual clinical decision-making.

Key joint kinematic characteristics of the gait of fallers identified by principal component analysis

It has been reported that fallers have a higher risk of subsequent falls than non-fallers. Therefore, if the differences between the movements of recent fallers and non-fallers can be identified, such could be regarded as the basis of the high risk of falling of the former. The objective of the present study was the identification of the key joint kinematic characteristics of human gait related to the risk of falling while walking on level ground. For this purpose, joint kinematics data obtained from 18 recent fallers and 19 non-fallers were analyzed using principal component analysis (PCA). The PCA was conducted using an input matrix constructed from the time-normalized average and standard deviation of the lower limb joint angles on three planes (101 data×2 parameters×3 angles×3 planes). The PCA revealed that only the 5th principal component vector (PCV 5) among the 23 generated PCVs was related to the risk of falling (p<0.05, ES=0.71). These findings as well as those of previous studies suggest that the joint kinematics of PCV 5 is the key characteristic that affects the risk of falling while walking. We therefore recombined the joint kinematics corresponding to PCV 5 and concluded that the variability of the joint kinematics for fallers was larger than that for non-fallers regardless of the joint. These observations as well as the findings of previous studies suggest that the risk of falling can be reduced by reducing the variability of the joint kinematics using an intervention such as external cues or a special garment.

Quantification of the safe maximal lift in functional capacity evaluations: comparison of muscle recruitment using SEMG and therapist observation

INTRODUCTION

This study aimed to identify any correlation between muscle activity using surface electromyography (SEMG) and therapist determined safe maximal lift (SML) during the bench to shoulder lift of the WorkHab FCE. This would support construct (convergent) validity of SML determination in the WorkHab FCE.

METHOD

An experimental laboratory based study design was used. Twenty healthy volunteers performed the bench to shoulder lift of the WorkHab FCE whilst SEMG of upper trapezius, mid deltoid, thoracic, brachioradialis and bicep muscles were recorded. A summary of the data is presented using descriptive statistics and differences between groups were tested using generalised linear mixed models.

RESULTS

Results showed a significant difference in activity and duration of muscle activation with increasing weight lifted [p = 0.000 and p = 0.024 (brachioradialis)]. There was a significant difference between the up lift (bench to shoulder) and the down lift (shoulder to bench) for all muscles (p = 0.000) except the brachioradialis (p = 0.819). No significant change was found in muscle activity before or after the SML.

CONCLUSION

Convergent validity of the bench to shoulder lift of the WorkHab FCE was not established as no relationship between the muscle recruitment using SEMG and SML, as determined by therapist observation was identified during this lift.

Patterns of hip flexion motion predict frontal and transverse plane knee torques during a single-leg land-and-cut maneuver

BACKGROUND

Impulsive frontal plane knee joint torques directly strain the anterior cruciate ligament and therefore may contribute to injury risk. Because deleterious torques may in part be related to aberrant kinematic movement patterns the primary purpose of this study was to establish a prediction model for frontal plane knee joint torques based on motion characteristics derived from Principal Component Analysis.

METHODS

Eighteen healthy NCAA Division I female athletes performed a single-leg land-and-cut maneuver (n=5 trials) with their dominant limb. Ensemble average lower extremity joint angles for the hip, knee, and ankle along with normalized external knee abduction torques were calculated for the entire stance phase. The ensemble kinematic data were individually submitted to a Principal Component Analysis. Principal component scores were used in a forward step-wise regression model to establish a prediction equation for peak ensemble-averaged knee abduction torque.

FINDINGS

Approximately 31% of the variance in knee abduction torque was explained by a principal component that captured relative magnitudes of hip flexion motion during early stance. Likewise, approximately 32% of the variance in knee internal rotation torque was explained by a principal component that captured overall hip flexion during stance.

INTERPRETATION

Rapid hip flexion motion during the first half of the stance phase of a single-leg land-and-cut maneuver is associated with greater knee abduction joint torques, whereas greater overall flexion during the entire stance phase is associated with smaller internal rotation torques.

The personal lift-assist device and lifting technique: a principal component analysis

The personal lift-assist device (PLAD) is a non-motorised, on-body device that acts as an external force generator using the concept of stored elastic energy. In this study, the effect of the PLAD on the lifting kinematics of male and female lifters was investigated using principal component analysis. Joint kinematic data of 15 males and 15 females were collected using an opto-electronic system during a freestyle, symmetrical-lifting protocol with and without wearing the PLAD. Of the 31 Principal Components (PCs) retained in the models, eight scores were significantly different between the PLAD and no-PLAD conditions. There were no main effects for gender and no significant interactions. Results indicated that the PLAD similarly affected the lifting kinematics of males and females; demonstrating significantly less lumbar and thoracic flexion and significantly greater hip and ankle flexion when wearing the PLAD. These findings add to the body of work that suggest the PLAD may be a safe and effective ergonomic aid. STATEMENT OF RELEVANCE: The PLAD is an ergonomic aid that has been shown to be effective at reducing low back demands during manual materials handling tasks. This body of work establishes that the PLAD encourages safe lifting practices without adversely affecting lifting technique.

How to lift a box that is too large to fit between the knees

Many studies compared lifting techniques such as stoop and squat lifting. Results thus far show that when lifting a wide load, high back loads result, irrespective of the lifting technique applied. This study compared four lifting techniques in 11 male subjects lifting wide loads. One of these techniques, denoted as the weight lifters' technique (WLT), is characterised by a wide foot placement, moderate knee flexion and a straight but not upright trunk. Net moments were calculated with a 3-D linked segment model and spinal forces with an electromyographic-driven trunk model. When lifting the wide box at handles that allow a high grip position, the WLT resulted in over 20% lower compression forces than the free, squat and stoop lifting technique, mainly due to a smaller horizontal distance between the l5S1 joint and the load. When lifting the wide box at the bottom, none of the lifting techniques was clearly superior to the others. STATEMENT OF RELEVANCE: Lifting low-lying and large objects results in high back loads and may therefore result in a high risk of developing low back pain. This study compares the utility of a WLT, in terms of back load and lumbar flexion, to more familiar techniques in these high-risk lifting tasks.

Analysis of multiple waveforms by means of functional principal component analysis: normal versus pathological patterns in sit-to-stand movement

This paper presents an application of functional principal component analysis (FPCA) to describe the inter-subject variability of multiple waveforms. This technique was applied to the study of sit-to-stand movement in two groups of people, osteoarthritic patients and healthy subjects. Although STS movement has not been extensively applied to the study of knee osteoarthritis, it can provide relevant information about the effect of osteoarthritis on knee joint function. Two waveforms, knee flexion angle and flexion moment, were analysed simultaneously. Instead of using the common multivariate approach we used the functional one, which allows working with continuous functions with neither discretization nor time-scale normalization. The results show that time-scale normalization can alter the FPCA solution. Furthermore, FPCA presents better discriminatory power compared with the classical multivariate approach. This technique can, therefore, be applied as a functional assessment tool, allowing the identification of relevant variables to discriminate heterogeneous groups such as healthy and pathological subjects.

The identification of age-related differences in kinetic gait parameters using principal component analysis

Background. The age of onset of adult-like kinetic gait patterns is controversial. A potential cause of discrepant results between studies is the statistical analyses used to test for differences in kinetic parameters between age groups. Therefore, the purpose of this study was to identify age-related differences in kinetic gait parameters across children aged 3-13 years using principal component analysis. Methods. Principal component analysis was applied to seven kinetic waveform variables (N=7) from each of four age groups (3-4 years (n=13); 5-6 years (n=10); 7-8 years (n=12); and 9-13 years (n=12)). The principal component scores for each kinetic variable were used to test for group differences using one-way ANOVA and Kruskal-Wallis tests. Findings. Significant group differences (P<0.05) were found for five of the principal component scores. Plantarflexion moments increased with age and the oldest group of children (9-13 years old) demonstrated significantly larger plantarflexor moment patterns compared to all other age groups. The 9-13 years old showed significantly larger knee flexor and extensor moments for the first half of the cycle and a later reversal to extensor moments in terminal stance compared to 3-6 years old. The older group also showed decreased hip extensor moments for the first third of the cycle and increased flexor moments in the second third of the cycle compared to the 3-4 and 7-8 years old. Larger stance phase hip abduction moments were observed in the older group compared to all other groups. This was followed by a more complex pattern of alternating moments. Hip power also showed a complex series of differences between age-groups. Interpretation. Compared to parameterization techniques, principal component analysis identified different characteristics in kinetic gait data to discriminate between paediatric age groups. This is the first study to identify age-related differences in gait kinetics using waveform analysis.

Neuromuscular and lower limb biomechanical differences exist between male and female elite adolescent soccer players during an unanticipated side-cut maneuver

BACKGROUND

Female athletes are 2 to 8 times more likely than male athletes to injure the anterior cruciate ligament during a non-contact athletic maneuver. Identifying anterior cruciate ligament injury risk factors in female athletes may help with the development of preventive training programs aimed at reducing injury rates.

HYPOTHESIS

Differences between genders in lower limb kinematics, kinetics, and neuromuscular patterns will be identified in an adolescent soccer population during an unanticipated side-cut maneuver.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-two elite adolescent soccer players (21 male and 21 female) performed an unanticipated side-cut maneuver, with the 3-dimensional kinematic, kinetic, and electromyographic lower limb data being analyzed using principal component analysis.

RESULTS

The female athletes had higher gastrocnemius activity, normalized to maximal voluntary isometric contractions, and a mediolateral gastrocnemius activation imbalance that was not present in the male athletes during early stance to midstance of the side-cut. Female athletes demonstrated greater rectus femoris muscle activity throughout stance, and the only hamstring difference identified was a mediolateral activation imbalance in male athletes only. Female athletes performed the side-cut with less hip flexion and more hip external rotation and also generated a smaller hip flexion moment compared with the male athletes.

CONCLUSION

This is the first study to identify gender-related differences in gastrocnemius muscle activity during an unanticipated cutting maneuver.

CLINICAL RELEVANCE

The increased and imbalanced gastrocnemius muscle activity, combined with increased rectus femoris muscle activity and reduced hip flexion angles and moments in female subjects, may all have important contributing roles in the higher noncontact ACL injury rates observed in female athletes.

Muscular and postural demands of using a massage chair and massage table

OBJECTIVE

The aim of this study was to determine the difference in muscular and postural demands of performing manual therapy using a massage chair and a massage table.

METHODS

Twelve female senior massage therapy students performed two 10-minute regional back massages on a fully clothed client using both a massage chair and massage table. The root mean square was used to determine the mean activation from the electromyographic signal collected from 8 upper extremity muscles. Integrated electromyography was used to compare activation between the 14 massage techniques used. Eight electromagnetic motion capture sensors were attached: the head, trunk, and upper arm, forearm, and hand bilaterally to track segment kinematics and determine total time spent in different postures.

RESULTS

There was higher activation in lumbar erector spinae when using the table and anterior deltoid when using the chair. The anterior deltoid showed a significant condition x period interaction for mean muscle activation for 6 of the 14 massage techniques. The therapists spent significantly more time in mild trunk flexion when using the massage table and significantly more time in severe radial deviation and mild shoulder flexion when using the massage chair.

CONCLUSIONS

The chair and table were more demanding of the anterior deltoid and lumbar erector spinae, respectively. Therapists adopted trunk and wrist postures that would increase the risk of upper extremity injury while using either the massage chair or table.

Knee biomechanics of moderate OA patients measured during gait at a self-selected and fast walking speed

Osteoarthritis (OA) is a chronic disorder resulting in degenerative changes to the knee joint. Three-dimensional gait analysis provides a unique method of measuring knee dynamics during activities of daily living such as walking. The purpose of this study was to identify biomechanical features characterizing the gait of patients with mild-to-moderate knee OA and to determine if the biomechanical differences become more pronounced as the locomotor system is stressed by walking faster. Principal component analysis was used to compare the gait patterns of a moderate knee OA group (n=41) and a control group (n=43). The subjects walked at their self-selected speed as well as at 150% of that speed. The two subject groups did not differ in knee joint angles, stride length, and stride time or walking speed. Differences in the magnitude and shape of the knee joint moment waveforms were found between the two groups. The OA group had larger adduction moment magnitudes during stance and this higher magnitude was sustained for a longer portion of the gait cycle. The OA group also had a reduced flexion moment and a reduced external rotation moment during early stance. Increasing speed was associated with an increase in the magnitude of all joint moments. The fast walks did not, however, increase or bring out any biomechanical differences between the OA and control groups that did not exist at the self-selected walks.

Principal component analysis of lifting waveforms

BACKGROUND

One limiting factor in lifting research design has been the inability to effectively analyze waveform data, especially when differences in body mass, height, and load magnitude influence the derived kinetic variables. The purpose of this study was to demonstrate the sensitivity of principal component analysis to quantify clinically relevant differences in kinetic lifting waveforms over three load magnitudes and between two separate populations.

METHODS

Principal component analysis was applied to five kinetic lifting waveforms. The derived principal component scores were used as the dependent measures in a two-way (clinical status x load magnitude) MANOVA.

FINDINGS

Significant low back pain group differences (P<0.05) were found for three of the principal component scores on extension moment generation in the sacral and thoracic regions and for trunk compression. Significant differences were found for each variable with respect to the magnitude across the entire lift time between the three load conditions, as well as four significant differences related to inferred mechanical changes that resulted from lifting increasingly heavier loads.

INTERPRETATION

Principal component analysis of kinetic lifting waveforms was shown to be insensitive to a confounding factor of different load magnitudes when attempting to identify previously determined clinically relevant differences in the waveform trajectories. The analysis was able to partition the variability attributed to the direct influence of different external load magnitudes, versus those differences in spinal loading that arose from the variations in the lifting mechanics of increasing loads. The technique could be beneficial for other kinetic analyses where confounding magnitude modifiers like body size are present.