Clinical tests predictive of temporary low back pain development during the prolonged standing test in physical therapy students.

Low back pain among physical therapists is a common musculoskeletal disorder that first occurs early in their career or as a student. This observational prospective study assessed the ability of hip and lumbopelvic neuromuscular control, endurance and hip range of motion tests to predict the development of transient low back pain development during a standing task. Seventy-two physical therapy students without low back pain completed nine performance tests and a 2-hour standing test on two separate days. Participants were classified as transient pain developers (PD) if they reported a ≥ 10mm increase in low back pain on a visual analog scale. Transient back pain was reported by 37.5% of students during the standing test. A cluster of three positive tests, self-rated active hip abduction (somewhat difficult or more), bilateral total hip internal rotation greater than 81 degrees, and non-dominant limb single-leg squat (moderate deviations), demonstrated an increased probability (94.9%) of identifying PDs. Negative findings on the same three tests decreased the probability to 10.7%. Overall, the classification accuracy for the three-test model was 72.2%. The sensitivity for the model was 63% and the specificity was 77.8%.

A 3-test cluster of poor hip and lumbopelvic neuromuscular control and increased hip internal rotation range of motion is an effective screening tool for identifying physical therapy students who are most likely and least likely to develop transient LBP during 2 hours of standing.

Hip Joint Contact Loading and Muscle Forces During Running With a Transtibial Amputation.

People with unilateral transtibial amputations (TTA) have greater risks of bilateral hip osteoarthritis, related to asymmetric biomechanics compared to people without TTA. Running is beneficial for physical health and is gaining popularity. However, people with TTA may not have access to running-specific prostheses (RSPs), which are designed for running, and may instead run using their daily-use prosthesis (DUP). Differences in joint loading may result from prosthesis choice; thus, it is important to characterize changes in peak and impulsive hip joint contact loading during running. Six people with and without TTA ran at 3.5 m/s while ground reaction forces, kinematics, and electromyography were collected. People with TTA ran using their own RSP and DUP. Musculoskeletal models incorporating prosthesis type of each individual were used to quantify individual muscle forces and hip joint contact forces (HJCFs) during running. People using RSPs had smaller bilateral peak hip joint contact forces compared to when wearing DUPs during stance and swing, and a smaller impulse over the entire gait cycle. Greater amputated leg peak hip joint contact forces for people wearing DUPs compared to RSPs occurred with greater forces from the ipsilateral gluteus maximus during stance. People with TTA also had greater bilateral peak hip joint contact forces during swing compared to people without TTA, which occurred with greater peak gluteus medius forces. Running with more compliant RSPs may be beneficial for long-term joint health by reducing peak and impulsive hip loading compared to DUPs.

Office-workers maintain decreased workplace sitting time long-term following participation in a sit-stand desk intervention study.

Previous studies report decreased workplace sitting time when standing desk interventions are provided to office workers. It is unclear whether decreased sedentary behaviours are maintained long-term. This was a follow-up to a previous intervention study to investigate whether observed sitting time decreases of 30-50% were sustained 12-24 months later. A secondary aim was to compare overall physical activity between office workers with and without standing desks. Although sitting time increased over the follow-up period, this did not reach significance and reductions in workplace sitting remained significantly lower (23.5% decrease) from baseline values. There were no differences in the physical activity measures between workers with and without access to standing desks, although this was a small sample size and further research is needed. Individuals who are motivated to try standing desks at work can benefit through decreased sitting time long-term, however this may not extend to increased overall physical activity levels. Practitioner summary: Providing standing desk options to office-based employees can have long-lasting impacts with reducing sitting time at work. Office workers who choose to stand at work do not appear to compensate with overall activity level reduction outside of work.Abbreviations: LBP: low back pain; OSPAQ: occupational sitting and physical activity questionnaire; VAS: visual analog scale; ANOVA: analysis of variance; BMI: body mass index; ICC: intraclass correlation coefficient.

Hip and Trunk Muscle Activity and Mechanics During Walking With and Without Unilateral Weight.

Pelvic drop is caused by decreased hip abductor muscle activity and is associated with lower-extremity injury. Hip abductor strengthening exercises are well established; however, no standard method exists to increase hip abductor activity during functional activities. The purpose of this research was to study the effects of walking with a unilateral weight. A total of 26 healthy adults walked on an instrumented treadmill with and without handheld weight (15%-20% body weight). Muscle activity, kinematic, and kinetic data were collected using surface electromyography, motion capture, and force plates, respectively. Average hip and trunk muscle activity, hip, pelvic, and trunk angles, and peak internal hip moments during stance were compared for each side (contralateral/ipsilateral to the weight) between conditions (unweighted/weighted) using a generalized linear model with generalized estimating equation correction. Interactions between condition and side were observed for muscle activity, frontal plane pelvic and trunk angles, and frontal plane hip moments (P ≤ .003). Compared with the unweighted condition, the weighted condition had higher hip abductor activity contralateral to the weight (P < .001), while no change was found ipsilateral to the weight (P ≥ .790). Similar changes were found for kinematic and kinetic variables. Walking with a unilateral weight may be a therapeutic option to increase functional hip abductor activity.

Increasing standing tolerance in office workers with standing-induced back pain.

Sit-stand desks are popular however many people have standing-induced low back pain (LBP). People with LBP have fewer standing weight shifts compared with back-healthy people. Participants were classified as standing-tolerant or intolerant. Participants were provided sit-stand desks for 12 weeks. Participants were assigned to intervention (graded standing exposure and exercise) or control (no instruction) conditions. Participants reported weekly sitting time and average/worst LBP. Standing weight shifts and LBP were re-assessed post-intervention. All groups decreased sitting time (range: 30-50%) over 12 weeks. Sitting time and average LBP were correlated in all standing-intolerant individuals, worst LBP and sitting time were correlated for intervention group only. All standing-intolerant individuals increased standing weight shifts and decreased LBP after 12-weeks. Standing-intolerant individuals benefitted from 12-weeks of sit-stand desk use regardless of intervention. Motivated individuals with standing-induced LBP may increase standing tolerance with sit-stand desk use. Additional benefits may exist when structured guidance is provided. Practitioner summary: Many people are standing-intolerant due to low back pain (LBP). This lab and field-based study showed some benefits from structured approaches to gradually progress standing time when transitioning to standing work. Using a sit-stand desk for 12 weeks resulted in decreased LBP and sitting time in standing-intolerant people. Abbreviations: LBP: low back pain; OSPAQ: Occupational Sitting and Physical Activity Questionnaire; VAS: visual analog scale; GRF: ground reaction force; WeekVASMAX: worst low back pain reported on visual analog scale for prior week; WeekVASAVE: average low back pain reported on visual analog scale for prior week; ICC: intraclass correlation coefficient; LabVASMAX: worst low back pain reported on visual analog scale during lab-based standing; LabVASAVE: average low back pain reported on visual analog scale during lab-based standing; FvR,L: vertical ground reaction force for right and left force plate; BWSSMALL: small (10-29% body weight) body weight shift; BWSLARGE: large (> 30% body weight) body weight shift; ActivPALSED: ActivePAL data for sedentary time; ActivPALSTND: ActivePAL data for standing time; ANOVA: analysis of variance; Standing Intolerant-INT: standing intolerant participants assigned to intervention condition; Standing Intolerant-CON: standing intolerant participants assigned to control condition; Standing Tolerant-INT: standing tolerant participants assigned to intervention condition; Standing Tolerant-CON: standing tolerant participants assigned to control condition; SI: standing intolerant; ST: standing tolerant; INT: intervention; CON: control.

Lumbar Intervertebral Kinematics During an Unstable Sitting Task and Its Association With Standing-Induced Low Back Pain.

People developing transient low back pain during standing have altered control of their spine and hips during standing tasks, but the transfer of these responses to other tasks has not been assessed. This study used video fluoroscopy to assess lumbar spine intervertebral kinematics of people who do and do not develop standing-induced low back pain during a seated chair-tilting task. A total of 9 females and 8 males were categorized as pain developers (5 females and 3 males) or nonpain developers (4 females and 5 males) using a 2-hour standing exposure; pain developers reported transient low back pain and nonpain developers did not. Participants were imaged with sagittal plane fluoroscopy at 25 Hz while cyclically tilting their pelvises anteriorly and posteriorly on an unstable chair. Intervertebral angles, relative contributions, and anterior-posterior translations were measured for the L3/L4, L4/L5, and L5/S1 joints and compared between sexes, pain groups, joints, and tilting directions. Female pain developers experienced more extension in their L5/S1 joints in both tilting directions compared with female nonpain developers, a finding not present in males. The specificity in intervertebral kinematics to sex-pain group combinations suggests that these subgroups of pain developers and nonpain developers may implement different control strategies.

A Comparison of Clinical Spinal Mobility Measures to Experimentally Derived Lumbar Spine Passive Stiffness.

Spinal stiffness and mobility assessments vary between clinical and research settings, potentially hindering the understanding and treatment of low back pain. A total of 71 healthy participants were evaluated using 2 clinical assessments (posteroanterior spring and passive intervertebral motion) and 2 quantitative measures: lumped mechanical stiffness of the lumbar spine and local tissue stiffness (lumbar erector spinae and supraspinous ligament) measured via myotonometry. The authors hypothesized that clinical, mechanical, and local tissue measures would be correlated, that clinical tests would not alter mechanical stiffness, and that males would demonstrate greater lumbar stiffness than females. Clinical, lumped mechanical, and tissue stiffness were not correlated; however, gradings from the posteroanterior spring and passive intervertebral motion tests were positively correlated with each other. Clinical assessments had no effect on lumped mechanical stiffness. The males had greater lumped mechanical and lumbar erector spinae stiffness compared with the females. The lack of correlation between clinical, tissue, and lumped mechanical measures of spinal stiffness indicates that the use of the term "stiffness" by clinicians may require reevaluation; clinicians should be confident that they are not altering mechanical stiffness of the spine through segmental mobility assessments; and greater resting lumbar erector stiffness in males suggests that sex should be considered in the assessment and treatment of the low back.

Influence of Sacroiliac Bracing on Muscle Activation Strategies During 2 Functional Tasks in Standing-Tolerant and Standing-Intolerant Individuals.

People who develop low back pain during standing (standing-intolerant) are a subclinical group at risk for clinical low back pain. Standing-intolerant individuals respond favorably to stabilization exercise and may be similar to people with sacroiliac joint dysfunction that respond to stabilization approaches including sacroiliac joint (SIJ) bracing. The purpose was to characterize muscle activation and response to SIJ bracing in standing-tolerant and standing-intolerant individuals during forward flexion and unilateral stance. Trunk and hip electromyography data were collected from 31 participants (17 standing-tolerant and 14 standing-intolerant) while performing these tasks with and without SIJ bracing. Kinematics were captured concurrently and used for movement phase identification. Cross-correlation quantified trunk coactivation and extensor timing during return-to-stand from forward flexion; root mean square amplitude quantified gluteal activity during unilateral stance. The standing-intolerant group had elevated erector spinae-external oblique coactivation without bracing, and erector spinae-internal oblique coactivation with bracing during return-to-stand compared with standing-tolerant individuals. Both groups reversed extensor sequencing during return-to-stand with bracing. Standing-tolerant individuals had higher hip abductor activity in nondominant unilateral stance and increased hip extensor activity with bracing. SIJ bracing could be a useful adjunct to other interventions targeted toward facilitating appropriate muscle activation in standing-intolerant individuals.

Acute Surgical Injury Alters the Tensile Properties of Thoracolumbar Fascia in a Porcine Model.

Recent work utilizing ultrasound imaging demonstrated that individuals with low back pain (LBP) have increased thickness and decreased mobility of the thoracolumbar fascia (TLF), an indication that the TLF may play a role in LBP. This study used a porcine injury model (microsurgically induced local injury)-shown to produce similar results to those observed in humans with LBP-to test the hypothesis that TLF mechanical properties may also be altered in patients with LBP. Perimuscular TLF tissue was harvested from the noninjured side of vertebral level L3-4 in pigs randomized into either control (n = 5) or injured (n = 5) groups. All samples were tested with a displacement-controlled biaxial testing system using the following protocol: cyclic loading/unloading and stress relaxation tests at 25%, 35%, and then 45% of their resting length. Tissue anisotropy was also explored by comparing responses to loading in longitudinal and transverse orientations. Tissues from injured pigs were found to have greater stretch-stretch ratio moduli (measure of tissue stiffness), less energy dissipation, and less stress decay compared to tissues from control pigs. Responses across these variables also depended on loading orientation. CLINICAL SIGNIFICANCE: these findings suggest that a focal TLF injury can produce impairments in tissue mechanical properties away from the injured area itself. This could contribute to some of the functional abnormalities observed in human LBP.

Rater Reliability and Concurrent Validity of Single and Dual Bubble Inclinometry to Assess Cervical Lateral Flexion.

OBJECTIVE: The purpose of this study was to assess interrater and intrarater reliability and validity for single inclinometry (SI) and dual inclinometry (DI) assessment of cervical lateral flexion (CLF) range of motion and compare reliability in a practicing physical therapist (PT) and student PTs (SPTs). METHODS: Twenty-four subjects performed right and left CLF while SI, DI, and 3-dimensional kinematics were concurrently recorded. Subjects were reassessed by 2 SPTs and 1 PT using both SI and DI. Each subject was measured twice per rater in round-robin fashion. RESULTS: There were significant positive relationships between DI and motion capture for both right (r = 0.841; P < .01) and left lateral flexion (r = 0.838; P < .01). Single inclinometry also had a significant correlation with motion capture for right (r = 0.927, P < .01) and left (r = 0.834, P < .01) lateral flexion. Interrater reliability was good for both SI and DI methods. For SI, intraclass correlation coefficient (ICC) (3,1) was 0.905 and 0.870 for right and left CLF, respectively. For DI, ICC(3,1) was 0.803 and 0.757 for right and left CLF, respectively. Intrarater reliability was good for both methods. Average SI values were ICC(2,1) of 0.928 and 0.897 for right and left CLF, respectively. Average DI values were ICC(2,1) of 0.882 and 0.851 for left and right, respectively. Although not significant, the PT had slightly higher reliability in all measures (range, 0.881-0.935) compared to the SPTs (range, 0.880-0.925). CONCLUSIONS: Both SI and DI are acceptable for clinical use and both are reliable measurement methods for CLF between raters and for repeated measures. There are minimal differences in reliability between a PT with experience and SPTs with minimal experience.

Distinctive characteristics of prolonged standing low back pain developers' and the associated risk factors: systematic review and meta-analysis.

Pain developers (PDs) are considered a pre-clinical low back pain (LBP) population at risk of clinical LBP development and thus exacting great social and economic costs. Therefore, it is necessary to comprehensively investigate their distinctive characteristics and the risk factors of standing-induced LBP based on which appropriate preventive measures can be planned. Scopus, Web of Science, and PubMed databases as well as Google Scholar and ProQuest were systematically searched from inception through 14 July 2022 using a combination of terms relevant to 'standing' and 'LBP'. Studies with low risk of bias in English and Persian using a methodological quality scoring system were deemed eligible for inclusion if they were laboratory studies using prolonged standing duration greater than 42 min to classify adult PDs and non-pain developers (NPDs) without a history of LBP. PDs were compared with NPDs in demographics, biomechanical, and psychological outcomes. Weighted or standardized mean differences, and Hedge's g were generated to determine the pooled effect sizes using STATA software version 17. 52 papers and theses involving 1070 participants (528 PDs and 542 NPDs) were eligible for inclusion in the systematic review 33 of which were used in meta-analyses. Significant differences between PDs and NPDs in terms of movement patterns, muscular, postural, psychological, structural, and anthropometric variables were evidenced. The following factors were found to have a statistically significant association with standing-induced LBP: lumbar fidgets (Hedge's g - 0.72, 95% CI - 1.35 to - 0.08, P = 0.03), lumbar lordosis in participants over 25 years (Hedge's g 2.75, 95% CI 1.89-3.61, P < 0.001), AHAbd test (WMD 0.7, 95% CI 0.36-1.05, P < 0.001), GMed co-activation (Hedge's g 4.24, 95% CI 3.18-5.3, P < 0.001), and Pain Catastrophizing Scale (WMD 2.85, 95% CI 0.51-5.19, P = 0.02). Altered motor control displayed in AHAbd test and higher lumbar lordosis in individuals over 25 years seem to be probable risk factors for standing-induced LBP. In order to detect standing-induced LBP risk factors, future researchers should investigate the association of the reported distinctive characteristics to the standing-induced LBP and that whether they are manipulable through various interventions.

Task type, preference, and occupation affect standing desk utilization in office workers.

BACKGROUND: Adjustable height sit-stand desks are becoming the norm in many workplaces. It is not known how task type, worker preference, and occupation impact utilization of the adjustable height feature. OBJECTIVE: This survey-based study aimed to determine how task type, preference and occupation affect office workers' sitting and standing behaviors at work. METHODS: Office workers (n = 123) from different occupations completed surveys about actual and preferred positions (sit, stand, either/both) during 39 common tasks from 4 different categories, as well as barriers to use. Each position was analyzed by task type, behavior, and occupation. RESULTS: There were differences between actual and preferred behavior for each position, with participants sitting more and standing less than preferred across all task categories. There were differences between task categories with participants sitting less for generative and routine, and standing more for communication tasks. The highest rates of either/both responses were for routine tasks. Engineers reported the lowest standing rates, and also indicated standing more than preferred. Information Tech and Engineering had the highest either/both responses. Finance reported the highest sitting rates. Personal, task-based and workplace limitations were cited as barriers to preferred use. CONCLUSION: Office workers would prefer to stand more at work. Occupation-specific needs and preferences, as well as types of tasks should be considered when providing workplace standing options.

Increased fall risk is associated with elevated co-contraction about the ankle during static balance challenges in older adults.

Falls are a leading contributor to disability in older adults. Increased muscle co-contraction in the lower extremities during static and dynamic balance challenges has been associated with aging, and also with a history of falling. Co-contraction during static balance challenges has not been previously linked with performance on clinical tests designed to ascertain fall risk. The purpose of this study was to investigate the relationship between co-contraction about the ankle during static balance challenges with fall risk on a commonly used dynamic balance assessment, the Four Square Step Test (FSST). Twenty-three volunteers (mean age 73 years) performed a series of five static balance challenges (Romberg eyes open/closed, Sharpened Romberg eyes open/closed, and Single Leg Standing) with continuous electromyography (EMG) of bilateral tibialis anterior and gastrocnemius muscles. Participants then completed the FSST and were categorized as 'at-risk' or 'not-at-risk' to fall based on a cutoff time of 12 s. Co-contraction was quantified with co-contraction index (CCI). CCI during narrow base conditions was positively correlated with time to complete FSST. High CCIs during all static balance challenges with the exception of Romberg stance with eyes closed were predictive of being at-risk to fall based on FSST time, odds ratio 19.3. The authors conclude that co-contraction about the ankle during static balance challenges can be predictive of performance on a dynamic balance test.

Acute biomechanical responses to a prolonged standing exposure in a simulated occupational setting.

Prolonged occupational standing has previously been associated with low back pain (LBP) development. The immediate effects of a bout of prolonged standing on subsequent functional movement performance have not been investigated. It is possible that including a period of prolonged standing may have acute, detrimental effects. The purpose of the study is to investigate the impact of a prolonged standing exposure on biomechanical profiles (trunk muscle activation, joint stiffness and kinematics) during three functional movements. A total of 23 volunteers without history of LBP performed lumbar flexion, single-leg stance and unloaded squat movements pre- and post 2 h of standing exposure. It was found that 40% of the participants developed LBP during the standing exposure. There was a decrease in vertebral joint rotation stiffness in lateral bending and increased centre of pressure excursion during unilateral stance following standing exposure. There may be adverse effects to prolonged standing if followed by activities requiring precise balance or resistance of side loads. STATEMENT OF RELEVANCE: Prolonged standing may result in decreases in balance reactions during narrow base conditions as well as in the capacity to effectively resist side-loads at the trunk. Consideration should be given when prolonged standing is included in the workplace.

Joint work and ground reaction forces during running with daily-use and running-specific prostheses.

Some individuals with a transtibial amputation (TTA) may not have access to running-specific prostheses and therefore choose to run using their daily-use prosthesis. Unlike running-specific prostheses, daily-use prostheses are not designed for running and may result in biomechanical differences that influence injury risk. To investigate these potential differences, we assessed the effect of amputation, prosthesis type, and running speed on joint work and ground reaction forces. 13 people with and without a unilateral TTA ran at speeds ranging from 2.5 m/s to 5.0 m/s. People with TTA ran using their own daily-use and running-specific prostheses. Body kinematics and ground reaction forces were collected and used to compute joint work. People with TTA had smaller peak braking, propulsive and medial/lateral ground reaction forces from the amputated leg compared to people without TTA. People wearing running-specific prostheses had smaller peak amputated leg vertical ground reaction forces compared to daily-use prostheses at speeds above 3.5 m/s. Medial/lateral forces were also smaller in running-specific prostheses, which may present balance challenges when running on varied terrain. Running-specific prostheses stored and returned more energy and provided greater propulsion, resulting in more similar positive hip work between legs compared to daily-use prostheses. Increases in positive hip work, but not device work, highlight the importance of the hip in increasing running speed. Running-specific devices may be beneficial for joint health at running-speeds above 3.5 m/s and provide advantages in propulsion and energy return at all speeds compared to daily-use prostheses, helping people with TTA achieve faster running speeds.

A comparison of trunk control in people with no history, standing-induced, and recurrent low back pain during trunk extension.

Objectives: This study compares people with recurrent low back pain (rLBP) and people with pre-clinical low back pain (standing-induced low back pain developers; PDs) to each other and back-healthy controls (non-pain developers; NPDs). Movement variability and muscular co-activity related to coordination are important for both rLBP and PDs, and these two groups also have altered static spine extension.Methods: Eleven participants with recurrent low back pain, and twenty-one asymptomatic participants, categorized as PDs (11) and NPDs (10) through an established standing protocol, volunteered for this study. Three phases of standing extension motion (lean, hold, and return to neutral) were analyzed. Root mean square angular jerk was calculated from trunk and pelvis kinematics, co-activation of the trunk and hip musculature were assessed in four-muscle sets.Results: Root-mean-square jerk was greater when returning to neutral than when leaning back during standing extension in all three groups. People with rLBP had reduced co-activity in their trunk extensors, people classified as PD had more co-activity in their hip extensors compared with the other groups, and anterior trunk co-activity was phase-dependent, and similar between groups.Discussion: Movement control alterations with low back pain may start as an over-protective co-activation strategy in those with standing-induced LBP and progress to an under-protective strategy in those with recurrent low back pain. Level of Evidence: 3.

Running-specific prostheses reduce lower-limb muscle activity compared to daily-use prostheses in people with unilateral transtibial amputations.

People with unilateral transtibial amputation (TTA) have biomechanical differences between the amputated and intact legs and compared to people without TTA during running. Additional biomechanical differences emerge between running with running-specific (RSPs) and daily-use prostheses (DUPs), but the associated underlying muscle activity is unclear. We collected surface electromyography from the biceps femoris long head, rectus femoris, vastus lateralis, and gastrocnemius as well as body kinematics and ground reaction forces in six people with and six people without TTA. We compared stance phase muscle activity and peak activation timing in people with and without TTA and between people using RSPs compared to DUPs during running at 3.5 m/s. Peak amputated leg hamstring activity occurred 34% (RSP) and 31% (DUP) earlier in stance phase compared to the intact leg. Peak amputated leg rectus femoris activity of people wearing DUPs occurred 8% and 9% later in stance phase than the intact leg of people wearing DUPs and amputated leg of people wearing RSPs, respectively. People with TTA had 45% (DUP) and 61% (RSP) smaller peak amputated leg knee extension moments compared to people without TTA, consistent with observations of quadriceps muscle activity. Using RSPs decreased overall muscle activity compared to DUPs.

Development of active hip abduction as a screening test for identifying occupational low back pain.

STUDY DESIGN: Analytic observational prospective study performed in a controlled laboratory setting. OBJECTIVES: To assess the ability of a new screening tool, the active hip abduction test, to predict low back pain development during prolonged standing in previously asymptomatic individuals. BACKGROUND: Most screening tools used for a patient with low back pain do not assess the patient's ability to maintain postural control in the frontal plane, when placed in an unstable position. Postural-control differences in pain developers, as compared to non-pain developers, during standing have been found previously. An attempt was made to predict pain development with a simple screening test. METHODS: Forty-three previously asymptomatic volunteers underwent a clinical assessment prior to a 2-hour standing protocol designed to induce low back pain. Participants rated low back pain with a visual analog scale and were classified into pain developers or non-pain developers. RESULTS: Forty percent of participants developed low back pain. The active hip abduction test was the only test that discriminated between pain-developer groups. When the examiner scored the test, the odds ratio was 3.85 (95% confidence interval [CI]: 1.05-19.07), and when the test was self-rated, the odds ratio was 6.55 (95% CI: 1.14-37.75) for pain development during standing. CONCLUSION: The active hip abduction test appears to show promise for predicting individuals who are at risk for low back pain development during prolonged standing. More work is required to validate the test in clinical populations, and to assess interrater and intrarater reliability.

Application of autocorrelation and cross-correlation analyses in human movement and rehabilitation research.

STUDY DESIGN: Technical note. OBJECTIVES: To provide background theory and information and to describe relevant applications of autocorrelation and cross-correlation methodology as they apply to the field of motor control in human movement and rehabilitation research. BACKGROUND: Commonly used methodologies for pattern and event recognition, determination of muscle activation timing for investigation of movement coordination, and motor control are generally difficult to implement, particularly with large datasets. A brief description of the underlying mathematical theory of correlation analyses is given, followed by 4 different examples of how this methodology is useful for research in the movement sciences. METHODS: Examples demonstrating the utility of correlation analyses are presented from several different studies conducted at the University of Waterloo. RESULTS: Autocorrelation was used to demonstrate the presence of 60-Hz noise in an electromyography signal that was not visible in the raw data. A "top-down" paraspinal muscle activation pattern was demonstrated for healthy adults during gait, with the use of cross-correlation. Cross-correlation was also used to quantify coactivation of bilateral gluteus medius muscles during standing in individuals who developed low-back pain. Gender differences in gluteus medius control of mediolateral center of pressure were seen with the use of cross-correlation. CONCLUSION: Autocorrelation and crosscorrelation have been shown to be an effective tool for several different applications in the movement sciences. Examples of the method's utility include noise detection within a signal, determination of relative muscle activation onsets for postural control, objective quantification of muscle coactivation, and relating muscle activations with mechanical events.

Dynamic balance during running using running-specific prostheses.

Running is beneficial for physical, social, and emotional health, and participating in physical activity, including running, is becoming more popular for people with an amputation. However, this population has a greater risk of falling relative to people without an amputation, which may be a barrier to running. Understanding how dynamic balance is maintained during running is important for removing this barrier. To investigate dynamic balance, we quantified whole-body angular momentum in eight people with a unilateral transtibial amputation (TTA) using running-specific prostheses (RSPs) compared to eight people without TTA during running at 2.5, 3.0, and 3.5 m/s. People with TTA had greater ranges of whole-body angular momentum compared to people without TTA in the frontal and sagittal planes (p < 0.01). These greater ranges resulted from smaller peak medial, lateral, and braking ground reaction forces from the amputated leg compared to the intact leg and people without TTA. Reduced RSP mass relative to the biological leg also influenced whole-body angular momentum as evidenced by smaller ranges of amputated leg angular momentum compared to the intact leg in the frontal and sagittal planes. Smaller amputated leg angular momentum corresponded with smaller contralateral arm angular momentum in the sagittal plane (p < 0.01). People with TTA maintain balance during running with altered muscle coordination and prosthesis characteristics. Restoring mediolateral force generation through prosthetic design advances may help in regulating the frontal plane component of whole-body angular momentum for people with TTA, with potential to improve their ability to maintain balance during running.