The influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination during weightlifting

Role of the Flexion Relaxation Phenomenon in the Analysis of Low Back Pain Risk in the Powerlifter: A Proof-of-Principle Study

INTRODUCTION

Unlike the most common training approaches for bodybuilding, powerlifting programs are generally based on maximum and submaximal loads, putting enormous stresses on the lumbar spine. The flexion relaxation phenomenon evaluation is a clinical tool used for low back pain (LBP) assessment. This study aimed to evaluate the role of the flexion relaxation phenomenon in the analysis of LBP in the powerlifters.

METHODS

Healthy professional powerlifters participated in the study. In fact, we divided the participants into a LBP-low-risk group and a LBP-high-risk group, based on a prior history of LBP. Outcome measures included flexion relaxation ratio (FRR) and trough surface electromyography collected during trunk maximum voluntary flexion; furthermore, during a bench press lifting, we measured the height of the arched back (ARCH), using a camera and the Kinovea video editing software, to consider a potential correlation with the risk of LBP.

RESULTS

We included a group of 18 male (aged 24-39 y) powerlifters of 93 kg category. We measured a nonsignificant mean difference of ARCH between low-risk LBP group and high-risk LBP subjects. Curiously, maximum voluntary flexions were both above the threshold of 3.2 μV; therefore, with an absence of appropriate myoelectric silence, on the contrary, the FRR ratios were higher than 9.5, considering the presence of the phenomenon, exclusively for the low-risk group. The lumbar arched back measurement data did not report any association with the LBP risk, regarding the maximum voluntary flexion value, and even more than the FRR there is a relationship with the presence or the absence of LBP risk.

CONCLUSIONS

FRR could be considered as a useful parameter for studying the risk of LBP in powerlifting. The FRR index not only refers to the possible myoelectric silence of the lumbar muscles in trunk maximum forward flexion but also takes into account the energy value delivered by the lumbar muscles during the flexion. Furthermore, we can indicate that the size of the powerlifter ARCH may not be a determining factor in the occurrence of LBP.

Influence of Repetitions-to-Failure Deadlift on Lumbo-Pelvic Coordination, With and Without Body Armor

ABSTRACT

Ramirez, VJ, Bazrgari, B, Spencer, A, Gao, F, and Samaan, MA. Influence of repetitions-to-failure deadlift on lumbo-pelvic coordination, with and without body armor. J Strength Cond Res XX(X): 000-000, 2024-Repetition-to-failure (RTF) deadlift is a training modality for building lifting capacity that is often implemented by service members to maintain a minimum level of physical fitness. Despite its physiological benefits, little is known about the effects of RTF on the biomechanics of lumbar spine. Additionally, the effects of heavy deadlift training with body armor are unknown. The aim of this study was to investigate the effects of RTF deadlift on lumbo-pelvic coordination and posture, with and without body armor. Twenty-three healthy subjects, recreational powerlifters, were recruited for this study. Kinematics of the trunk and pelvis were measured using a 3D motion capture system while subjects conducted RTF deadlifts with a 68-kg low-handle hexagonal bar with and without a simulated body armor (22.68 kg). Lumbo-pelvic coordination was characterized using a vector coding approach and coupling angle variability (CAV) using circular statistics, over 3 equally divided segments of the lifting phase. More specifically, the coupling angle values were used to determine the coordination pattern between the thorax and pelvis. Trunk and pelvis ranges of motion and the amount of in-phase lumbo-pelvic coordination pattern increased with RTF deadlift. Additionally, CAV of the first and the third segments of deadlift cycle increased with RTF deadlift. Increase in variability of lumbo-pelvic coordination and peak trunk flexion (i.e., indication of increased mechanical demand of lifting on the spine), as a result of RTF deadlifting, can have deleterious soft tissue responses and contribute to an increase in risk of lower back injury.

Lumbo-Pelvic Rhythm Monitoring Using Wearable Technology with Sensory Biofeedback: A Systematic Review

As an essential lower-back movement pattern, lumbo-pelvic rhythm (LPR) during forward trunk flexion and backward return has been investigated on a large scale. It has been suggested that abnormalities in lumbo-pelvic coordination are related to the risk of developing low back disorders. However, considerable differences in the approaches used to monitor LPR make it challenging to integrate findings from those investigations for future research. Therefore, the aim of this systematic review was to summarize the use of wearable technology for kinematic measurement with sensory biofeedback for LPR monitoring by assessing these technologies' specific capabilities and biofeedback capacities and exploring their practical viability based on sensor outcomes. The review was developed following the PRISMA guidelines, and the risk of bias was analyzed using the PREDro and STROBE scales. PubMed, Web of Science, Scopus, and IEEEXPLORE databases were searched for relevant studies, initially returning a total of 528 articles. Finally, we included eight articles featuring wearable devices with audio or vibration biofeedback. Differences in protocols and limitations were also observed. This novel study presents a review of wearable tracking devices for LPR motion-mediated biofeedback for the purpose of correcting lower back posture. More research is needed to determine the long-term effectiveness of these devices, as well as their most appropriate corresponding methodologies.

Exploring how metronome pacing at varying movement speeds influences local dynamic stability and coordination variability of lumbar spine motion during repetitive lifting

Auditory metronomes have been used to preserve movement consistency when examining local dynamic stability (LDS) and coordination variability (CV) of lumbar spine motion during repetitive movements. However, the potential influence of the metronome itself on these outcome measures has rarely been considered. Therefore, this study investigated the influence of different metronome paces (i.e., lifting speeds) on measures of lumbar spine LDS and thorax-pelvis CV during a repetitive lifting/lowering task in comparison to self-paced movements. Ten participants completed 5 repetitive lift/lower trials, where participants completed 35 consecutive repetitions (analysis on last 30 repetitions) at a self-selected pace for the first and last trial, and were paced by a 10 lift/min, 15 lift/min, and 20 lift/min metronome, in randomized order, for the remaining three trials. The average self-paced lift/lower speed before and after experiencing the three different metronome paced speeds was 16.2 (±1.02) and 17.2 (±0.73) lifts/min, respectively, and the most-preferred metronome pace trial was 15 lifts/min. Thorax-pelvis CV during the self-paced trials were similar (p > 0.05) to the 15 lift/min metronome paced trials, while greater thorax-pelvis CV was observed for the 10 lift/min compared to the 15 lift/min and 20 lift/min and second self-paced trial (all p < 0.026). This movement speed effect was not observed for lumbar spine LDS; however, more-dynamically stable movements were observed during all metronome paced trials in comparison to the self-paced trials. This study highlights that careful consideration is required when employing a metronome to control/manipulate movement characteristics while examining neuromuscular control using non-linear dynamical systems measures.

The effect of back muscle fatigue on EMG and kinematics based estimation of low-back loads and active moments during manual lifting tasks

This study investigated the effects of back muscle fatigue on the estimation of low-back loads and active low-back moments during lifting, using an EMG and kinematics based model calibrated with data from an unfatigued state. Fourteen participants performed lifting tasks in unfatigued and fatigued states. Fatigue was induced through semi-static forward bending. EMG, kinematics, and ground reaction forces were measured, and low-back loads were estimated using inverse dynamics and EMG-driven muscle model. A regression model was developed using data from a set of calibration lifts, and its accuracy was evaluated for unfatigued and fatigued lifts. During the fatigue-inducing task, the EMG amplitude increased by 2.8 %MVC, representing a 38% increase relative to the initial value. However, during the fatigued lifts, the peak EMG amplitude was found to be 1.6 %MVC higher than that observed during the unfatigued lifts, representing a mere 4% increase relative to the baseline unfatigued peak EMG amplitude. Kinematics and low-back load estimates remained unaffected. Regression model estimation errors remained unaffected for 5 kg lifts, but increased by no more than 5% of the peak active low-back moment for 15 kg lifts. We conclude that the regression-based estimation quality of active low-back moments can be maintained during periods of muscle fatigue, although errors may slightly increase for heavier loads.

Effect of Probiotic Yogurt Supplementation(Bifidobacterium animalis ssp. lactis BB-12) on Gut Microbiota of Female Taekwondo Athletes and Its Relationship with Exercise-Related Psychological Fatigue

OBJECTIVE

The gut microbiota plays a critical role in regulating human health and athletic performance. Probiotic supplementation has been shown to modulate gut microbiota composition and improve exercise performance. This study aimed to investigate the effect of probiotic yogurt supplementation on gut microbiota and its relationship with exercise-related psychological fatigue in female taekwondo athletes.

METHODS

Twenty female taekwondo athletes were randomly assigned to either a dietary intervention group (DK) or a control group (CK). The athletes' exercise-related psychological fatigue was measured using the Athlete Burnout Questionnaire (ABQ) before and after an 8-week intervention. High-throughput sequencing was used to profile the gut microbiota, and functional prediction of the microbial community was performed. The effect of the dietary intervention on the athletes' exercise-related psychological fatigue clearance rate and its relationship with the gut microbiota were explored.

RESULTS

(1) The probiotic supplementation of Bifidobacterium animalis ssp. lactis BB-12 for 8 weeks significantly increased the ABQ scores of the DK group compared to the CK group (p < 0.05). (2) The abundances of Bifidobacterium, Bacteroides, Lachnospiraceae, family _Lactobacillaceae, and genus _Lactobacillus were significantly higher in the DK group than in the CK group after probiotic supplementation, while Escherichia coli was significantly lower in the DK group than in the CK group. (3) The ABQa scores were positively correlated with Proteus; ABQb scores were positively correlated with Streptococcus and Enterococcus; and ABQc scores were positively correlated with Klebsiella, Bacteroides, and Streptomyces. (4) The DK group had significantly higher levels of L-arginine biosynthesis I (via L-ornithine), fatty acid biosynthesis and oxidation, and L-isoleucine biosynthesis III pathways compared to the CK group. Tyrosine degradation I (via 2,3-dihydroxyphenylpropionate) was significantly lower in the DK group than in the CK group.

CONCLUSIONS

Probiotic yogurt supplementation of Bifidobacterium animalis ssp. lactis can promote the clearance of exercise-related psychological fatigue in female taekwondo athletes by upregulating beneficial gut microbiota, inhibiting harmful gut microbiota, and regulating relevant metabolic pathways.

Task-specific fear influences abnormal trunk motor coordination in workers with chronic low back pain: a relative phase angle analysis of object-lifting

Background

Pain-related fear influences impaired trunk movement (e.g., limited movement of range and velocity), but it is unclear how fear relates to trunk motor coordination (e.g., a more “in-phase” upper-lower trunk motion pattern). We conducted the present study to: (1) identify the motor coordination pattern of the in-phase upper-lower lumbar movements during the lifting, and (2) determine how pain-related fear is related to the trunk coordination pattern in workers with chronic low back pain (CLBP).

Methods

We examined 31 male workers with CLBP (CLBP group) and 20 healthy controls with no history of CLBP (HC group). The movement task was lifting a box, the weight of which was 10, 30%, or 50% of the subject’s body weight. We used a 3D motion capture system to calculate the mean absolute relative phase angle (MARP) angle as an index of coordination and the mean deviation phase (DP) as an index of variability. We used a numerical rating scale to assess the subjects’ task-specific fear.

Results

The MARP angle during trunk extension movement in the 50% condition was significantly decreased in the CLBP group compared to the HCs; i.e., the upper lumbar movement was more in-phase with the lower lumbar movement. The hierarchical multiple regression analysis results demonstrated that a decreased MARP angle was associated with high task-specific fear.

Conclusions

A more ‘in-phase’ upper-lower lumbar movement pattern was predicted by task-specific fear evoked when performing a work-related activity. Our findings suggest that an intervention for task-specific fear may be necessary to improve an individual’s impaired trunk motor coordination.

The Effect of Social Support on Athlete Burnout in Weightlifters: The Mediation Effect of Mental Toughness and Sports Motivation

Objectives: Athlete burnout is a crucial concern affecting the development and athletic performance of young weightlifters. To reduce or relieve the prevalence of athlete burnout, this study examined the relationship across social support, sports motivation, mental toughness, and athlete burnout in weightlifters.

Methods: A total of 315 weightlifters aged 17–28 years old (151 males, 164 females; M_age = 18.89 years, SD = 3.66) from Sichuan, Chongqing, and Shanxi in China participated in this survey. The Perceived Available Support in Sport Questionnaire (PASS-Q), Sports Motivation Questionnaire (SMQ), Sports Mental Toughness Questionnaire (SMTQ), and Athlete Burnout Questionnaire (ABQ) were used in this study. SPSS Statistics 19.0, AMOS 21.0, and PROCESS 3.0 macro were used to analyze the collected data.

Results: The results indicated that weightlifters’ social support could negatively significantly affect athlete burnout [beta = −0.398; 95% confidence interval (CI): −0.3699, −0.2184; P < 0.05) via mental toughness and sports motivation. The mediation analysis revealed that they had partial mediating effect, including three paths: First, social support had a direct effect on athlete burnout (beta = −0.150; 95% CI: −0.1824, −0.0397; P < 0.05); second, sport mental toughness had a mediating effect on athlete burnout (beta = −0.113; 95% CI: −0.1703, −0.0631; P < 0.05); and finally, sports motivation had a mediating effect on athlete burnout (beta = −0.124; 95% CI: −0.1751, −0.0793; P < 0.05).

Conclusion: The findings revealed that social support could inhibit or prevent athlete burnout via mental toughness and sports motivation; thus, to decrease or relieve the prevalence of burnout in weightlifters, it is an important solution to enhance their social support.

Biomechanical assessment while using production tables on mast climbing work platforms

The objective of this study was to assess the impact of using alternative mast climbing work platform (MCWP) designs on trunk motion and postural stability with masonry workers while performing bricklaying and stepping down tasks using a conventional MCWP setting (i.e. with a step deck) as well as two types of production tables (straight- and L-shaped). The trunk angles and postural sway parameters of twenty-five masonry workers were recorded for the following tasks: (1) standing on a simulated MCWP and laying bricks on an adjacent wall, and (2) stepping down onto the step deck to get into position for doing the bricklaying task. Results indicated that the use of the L-shaped production table resulted in the lowest trunk ranges of motion and significantly reduced the workers' trunk angles in all three planes when compared to both the straight-shaped production table and the conventional approach of not using a production table. Data showed that both body sway velocity and area were significantly reduced when using either one of the production tables. The use of production tables significantly reduced impact sway forces when workers stepped from the main platform to the step deck. The use of production tables on MCWPs improved workers' postures and overall stability, which could reduce the risk of injury.

Enabling context aware data analysis for long-duration repetitive stooped work through human activity recognition in sheep shearing

There is evidence to suggest that changes in kinematics and neuromuscular control in activities that take place over long periods of time lead to increased injury risk. The collection of biometric data over long time periods could provide insight into these injuries. However, it is difficult to analyse long period biometric data for occupations as the analysis depends on the activity being performed, and it is not practical to manually label the amount of data required. A sufficiently accurate human activity recognition algorithm can provide a means to segment the activities and allow this analysis, but the classification must be robust to the inter-individual differences, as well as the intra-individual variations in movement over time that are the target of analysis. This work presents a person-independent human activity recognition algorithm for sheep shearing using a Hidden Markov Model with physical features that are identified to be relevant to spinal movement quality. The classifier achieved an F1 score of 96.47% in identifying the shearing task.

The immediate and prolonged effects of military body armor on the relative timing of thorax and pelvis rotations during toe-touch and two-legged squat tasks

Although military body armor is an effective life saver, it considerably loads more weight on the warfighters, increasing the risk of musculoskeletal injury. This study investigated the immediate and prolonged effects of wearing body armor on timing aspect of lumbo-pelvic coordination during the toe-touch (TT) and two-legged-squat (TLS) tests. A cross-over study design was used wherein twelve asymptomatic and gender-balanced individuals completed two experimental sessions with and without body armor. A session included two similar sets of tests, before and after exposure to a treadmill walk, containing a TT and a TLS test with ten cycles of fast bending and return. Reflective markers were attached on the participants to capture the kinematics of body segments in conjunction with a motion capture system. The mean absolute relative phase (MARP) and deviation phase (DP) between the thorax and pelvis were calculated for each test. The pre-walk MARP in the return was significantly larger with versus without body armor (p = 0.022), while there were no significant effects of body armor on the other outcome measures. In addition, the pre-walk MARP and DP in the bending and return, as well as the walk-induced changes in the MARP in the bending phase were significantly larger in TLS versus TT (p < 0.026). Therefore, using a body armor immediately made the lumbo-pelvic coordination less in-phase during return, but no prolonged effects were found. Further investigation is necessary to specify chances wearing a body armor increases the risk of musculoskeletal injuries in the lower back and lower extremities joints.

A Subject-Specific Approach to Detect Fatigue-Related Changes in Spine Motion Using Wearable Sensors

An objective method to detect muscle fatigue-related kinematic changes may reduce workplace injuries. However, heterogeneous responses to muscle fatigue suggest that subject-specific analyses are necessary. The objectives of this study were to: (1) determine if wearable inertial measurement units (IMUs) could be used in conjunction with a spine motion composite index (SMCI) to quantify subject-specific changes in spine kinematics during a repetitive spine flexion-extension (FE) task; and (2) determine if the SMCI was correlated with measures of global trunk muscle fatigue. Spine kinematics were measured using wearable IMUs in 10 healthy adults during a baseline set followed by 10 sets of 50 spine FE repetitions. After each set, two fatigue measures were collected: perceived level of fatigue using a visual analogue scale (VAS), and maximal lift strength. SMCIs incorporating 10 kinematic variables from 2 IMUs (pelvis and T8 vertebrae) were calculated and used to quantify subject-specific changes in movement. A main effect of set was observed (F (1.7, 15.32) = 10.42, p = 0.002), where the SMCI became significantly greater than set 1 starting at set 4. Significant correlations were observed between the SMCI and both fatigue VAS and maximal lift strength at the individual and study level. These findings support the use of wearable IMUs to detect subject-specific changes in spine motion associated with muscle fatigue.

Physiological and biomechanical comparison between electrically assisted bicycles and motorbikes during simulated mail delivery

Electrically assisted bicycles (EABs) and motorbikes were compared in terms of energy expenditure, internal and external forces, and technique when delivering mail with different loads at different distances from the mailbox. Twenty-two postal workers performed two simulated postal tasks (foot placement [close vs. far] and delivery, and simulated mail delivery circuit) while carrying 0 and 32 kg. Independent of mail load, delivering mail with EABs was classified as moderate intensity and resulted in 33% higher energy expenditure when compared to motorbikes. Ground reaction forces were larger (7-25%) for EAB when compared to motorbike. Larger ground reaction forces were observed when both EABs and motorbikes were positioned further from the mailbox (5-23%). Using EABs during mail delivery has potential to result in numerous health benefits that are associated with moderate intensity physical activity, but can lead to larger external forces when compared to motorbikes. Practitioner summary: In order to compare electrically assisted bicycles (EAB) and motorbikes, postal workers performed simulated deliveries in the laboratory whilst measurements of energy expenditure, body loads and movement patters were undertaken. Body loads and energy expenditure were larger using EAB, which result in health benefits associated with moderate intensity exercise. Abbreviations: EAB: electrically assisted bicycles; CI: confidence interval; UHEC: University Human Ethics Committee; MB: motorbike;SH: seat height; SF: seat to floor distance; VO2: oxygen uptake; VCO2: exhaled carbon dioxide; RER: respiratory exchangeratio; TTL signal: Transistor-Transistor Logic; MET: metabolic equivalent; 3D: three-dimensional; IIR: infinite impulse response; Hz:Hertz; N: Newtons; ROM: range of motion; SD: standard deviation; p: significance level; d: Cohen effect sizes.

Discriminating spatiotemporal movement strategies during spine flexion-extension in healthy individuals

BACKGROUND CONTEXT

The spine is an anatomically complex system with numerous degrees of freedom. Due to this anatomical complexity, it is likely that multiple motor control options exist to complete a given task.

PURPOSE

To identify if distinct spine spatiotemporal movement strategies are utilized in a homogenous sample of young healthy participants.

STUDY DESIGN

Kinematic data were captured from a single cohort of male participants (N=51) during a simple, self-controlled spine flexion-extension task.

METHODS

Thoracic and lumbar flexion-extension data were analyzed to extract the continuous relative phase between each spine subsection. Continuous relative phase data were evaluated using a principal component analysis to identify major sources of variation in spine movement coordination. Unsupervised machine learning (k-means clustering) was used to identify distinct clusters present within the healthy participants sampled. Once distinguished, intersegmental spine kinematics were compared amongst clusters.

RESULTS

The findings of the current work suggest that there are distinct timing strategies that are utilized, within the participants sampled, to control spine flexion-extension movement. These strategies differentiate the sequencing of intersegmental movement and are not discriminable on the basis of simple participant demographic characteristics (ie, age, height, and body mass index), total movement time or range of motion.

CONCLUSIONS

Spatiotemporal spine flexion-extension patterns are not uniform across a population of young healthy individuals.

CLINICAL SIGNIFICANCE

Future work needs to identify whether the motor patterns characterized with this work are driven by distinct neuromuscular activation patterns, and if each given pattern has a varied risk for low back injury.

Using a deep learning network to recognise low back pain in static standing

Low back pain (LBP) remains one of the most prevalent musculoskeletal disorders, while algorithms that able to recognise LBP patients from healthy population using balance performance data are rarely seen. In this study, human balance and body sway performance during standing trials were utilised to recognise chronic LBP populations using deep neural networks. To be specific, 44 chronic LBP and healthy individuals performed static standing tasks, while their spine kinematics and centre of pressure were recorded. A deep learning network with long short-term memory units was used for training, prediction and implementation. The performance of the model was evaluated by: (a) overall accuracy, (b) precision, (c) recall, (d) F1 measure, (e) receiver-operating characteristic and (f) area under the curve. Results indicated that deep neural networks could recognise LBP populations with precision up to 97.2% and recall up to 97.2%. Meanwhile, the results showed that the model with the C7 sensor output performed the best. Practitioner summary: Low back pain (LBP) remains the most common musculoskeletal disorder. In this study, we investigated the feasibility of applying artificial intelligent deep neural network in detecting LBP population from healthy controls with their kinematics data. Results showed a deep learning network can solve the above classification problem with both promising precision and recall performance.

Changes in movement variability and task performance during a fatiguing repetitive pointing task

Changes in neuromuscular strategies employed with fatigue during multi-joint movements are still poorly understood. Studies have shown that motor variability of individual joints increases when performing upper limb tasks to fatigue, while movement parameters related to the task goal remain constant. However, how the inter-limb coordination and its variability change during specific movement phases with fatigue is still unclear. The aim of this study was to assess the effects of neck-shoulder fatigue on shoulder and elbow kinematic variabilities, shoulder-elbow coordination and its variability, and endpoint characteristics during different phases of a forward pointing movement. Nineteen healthy young adults continuously performed a repetitive pointing task until fatigue (Borg rating of 8/10). Changes in elbow-shoulder coordination through the movement were assessed using the continuous relative phase and statistical nonparametric mapping methods. At the end of the task, muscle fatigue was evidenced by significant increases in anterior deltoid (+13%) and biceps brachii (+30%) activity. Shoulder horizontal abduction, elbow flexion variability and shoulder-elbow coordination variability were increased with fatigue at different moments of the movement cycle (shoulder: during the first 17% and most of the second half movement, elbow: from 73% to 91%, coordination: almost the whole movement). However, movement timing errors and endpoint spatial variability were mostly preserved, even with fatigue. We showed that increased variability with fatigue is not only observed in the fatigued joint (shoulder), but also in the elbow and shoulder-elbow coordination, and may have a goal of preserving global task performance.

Changes of lumbar posture and tissue loading during static trunk bending

Static trunk bending is an occupational risk factor for lower back pain (LBP). When assessing relative short duration trunk bending tasks, existing studies mostly assumed unchanged spine biomechanical responses during task performance. The purpose of the current study was to assess the biomechanical changes of lumbar spine during the performance of relatively short duration, sustained trunk bending tasks. Fifteen participants performed 40-s static trunk bending tasks in two different trunk angles (30° or 60°) with two different hand load levels (0 or 6.8 kg). Results of the current study revealed significantly increased lumbar flexion and lumbar passive moment during the 40 s of trunk bending. Significantly reduced lumbar and abdominal muscle activities were also observed in most conditions. These findings suggest that, during the performance of short duration, static trunk bending tasks, a shift of loading from lumbar active tissues to passive tissues occurs naturally. This mechanism is beneficial in reducing the accumulation of lumbar muscle fatigue; however, lumbar passive tissue creep could be introduced due to prolonged or repetitive exposure.

A data-driven approach to modeling physical fatigue in the workplace using wearable sensors

Wearable sensors are currently being used to manage fatigue in professional athletics, transportation and mining industries. In manufacturing, physical fatigue is a challenging ergonomic/safety "issue" since it lowers productivity and increases the incidence of accidents. Therefore, physical fatigue must be managed. There are two main goals for this study. First, we examine the use of wearable sensors to detect physical fatigue occurrence in simulated manufacturing tasks. The second goal is to estimate the physical fatigue level over time. In order to achieve these goals, sensory data were recorded for eight healthy participants. Penalized logistic and multiple linear regression models were used for physical fatigue detection and level estimation, respectively. Important features from the five sensors locations were selected using Least Absolute Shrinkage and Selection Operator (LASSO), a popular variable selection methodology. The results show that the LASSO model performed well for both physical fatigue detection and modeling. The modeling approach is not participant and/or workload regime specific and thus can be adopted for other applications.

Lumbar contribution to the trunk forward bending and backward return; age-related differences

Age-related differences in lumbar contribution to the trunk motion in the sagittal plane were investigated. Sixty individuals between 20-70 years old in five gender-balanced age groups performed forward bending and backward return with slow and fast paces. Individuals older than 50 years old, irrespective of the gender or pace, had smaller lumbar contribution than those younger than this age. The lumbar contribution to trunk motion was also smaller in female participants than male participants, and under fast pace than under the slow pace. Age-related differences in lumbar contributions suggest the synergy between the active and passive lower back tissues is different between those above and under 50 years old, differences that are likely to affect the lower back mechanics. Therefore, detailed modelling should be conducted in future to find the age-related differences in the lower back mechanics for tasks involving large trunk motion. Practitioner Summary: Lumbar contribution to the sagittal trunk motion was observed to be smaller in individuals above 50 years old than those below this age. This could be an indication of a likely change in the synergy between the active and passive lower back tissues, which may disturb the lower back mechanics.

Lumbopelvic rhythm in the sagittal plane: A review of the effects of participants and task characteristics

OBJECTIVES

Abnormalities of lumbopelvic coordination have been suggested to relate to risk of developing low back pain. The objective of this study is to review and summarize the findings of studies that have implemented and reported on lumbopelvic rhythm during trunk forward bending and backward return.

METHODS

The PUBMED and CINAHL databases were searched for studies related to LPR using appropriate keywords. The references of each study from the database search were further investigated to identify any missed study.

RESULTS

The findings includes results related to lumbopelvic rhythm, and how it varies due to participant characteristics such as age, gender, and presence of low back pain as well as due to variations in the experimental procedures such as pace of motion, presence of external load, and muscle fatigue.

CONCLUSION

In general, the magnitude of lumbar contribution is smaller in people with low back pain, in the elderly and females, as well as with greater pace of motion, but is larger with greater external load or back muscle fatigue. The compiled data in this review are expected to serve as a foundation for implementation of this kinematic-based measure in the conduct of future research.

Lumbopelvic rhythm during trunk motion in the sagittal plane: A review of the kinematic measurement methods and characterization approaches

Lumbopelvic rhythm during trunk forward bending and backward return has been widely investigated to have a better understanding of the pattern of trunk motion, as used in research on low back disorders. Considerable differences in the methods used to measure, and approaches used to characterize the lumbopelvic rhythm hinder the integration of findings of those studies for further research in the future. Thus, the purpose of this review was to summarize the methods for kinematic measurement as well as their characterization approaches for the lumbopelvic rhythm. PUBMED and CINAHL databases were searched for relevant studies. Several types of instruments were found to be used in the reviewed studies, mostly using markers or sensors, which were placed on different parts of spine, with different definitions to measure the lumbar and pelvic motion. Also, various characterization approaches were found to be used, of which some related to the magnitude, while the others to the timing aspects of lumbopelvic rhythm. Such a characterization was either qualitative or quantitative. In addition, the specified characterization approaches were applied on a sample of trunk kinematics data from our lab to demonstrate differences in the outcomes of these approaches.