Exploring social determinants of health and physical activity levels in older adults living with mild cognitive impairment and dementia in the Upper Midwest of the United States.

BACKGROUND: Physical activity can improve physical health for people living with mild cognitive impairment (MCI) and dementia and may have cognitive benefits. Identifying modifiable social factors inhibiting physical activity among this group is needed. We sought to examine the relationship between reported physical activity levels and social determinants of health (SDOH) in a population of older adults living with MCI or dementia. METHODS: This descriptive study included people with a diagnosis of MCI or dementia followed by Community Internal Medicine at Mayo Clinic (Rochester, Minnesota, United States), aged over 55 years, who had a clinic visit between June 1, 2019 and June 30, 2021 and had completed a SDOH questionnaire. We focused on 8 SDOH domains: education, depression, alcohol use, stress, financial resource strain, social connections, food insecurity, and transportation needs. Data were analyzed based on physical activity level (inactive, insufficiently active, sufficiently active). SDOH domains were compared according to physical activity level using the χ2 test and multinomial logistic regression. RESULTS: A total of 3224 persons with MCI (n = 1371) or dementia (n = 1853) who had completed questions on physical activity were included. Of these, 1936 (60%) were characterized as physically inactive and 837 (26%) insufficiently active. Characteristics associated with an increased likelihood of physical inactivity were older age, female sex, obesity, lower education, dementia diagnosis, screening positive for depression and increased social isolation (p < 0.001). CONCLUSIONS: Physical inactivity is common among people living with MCI and dementia. Physical activity levels may be influenced by many factors, highlighting potential areas for intervention.

Intraprocedural ergonomics of vascular surgeons.

OBJECTIVE: The objective of this study was to estimate the ergonomic postural risk (EPR) for musculoskeletal posture of vascular surgeons performing open and endovascular procedure types and with various adjunctive equipment using wearable inertial measurement unit (IMU) sensors. The hypothesis was that EPR will increase with increased physical and mental demand as well as with procedural complexity. METHODS: A prospective, observational study was conducted at a large, quaternary academic hospital located at two sites. Sixteen vascular surgeons (13 male) participated in the study. Participants completed a presurgery and postsurgery survey consisting of a body part discomfort scale and a modified NASA-Task Load Index. Participants wore IMU sensors on the head and upper body to measure EPR during open and endovascular procedures. RESULTS: Vascular surgeons have increased EPR scores of the neck as measured by the IMUs and increased lower back pain when performing open surgery compared with non-open surgery (P < .05). Open procedures were rated as more physically demanding. The use of loupes resulted in increased EPR scores for the neck and torso (P < .05), and they were significantly associated with higher levels of lower back pain during procedures (P < .05) as well as with higher levels of physical demand (P < .05). The use of headlights also resulted in increased subjectively measured levels of physical demand and lower back pain. In comparing survey responses with IMU data, surveyed physical demand was strongly and significantly correlated with the neck (r = 0.61; P < .0001) and torso (r = 0.59; P < .0001) EPR scores. The use of lead aprons did not affect EPR or most surveyed measures of workload but resulted in significantly higher levels of distraction (P < .01). The data presented highlight the potential of using wearable sensors to measure the EPR of surgeons during vascular surgical procedures. CONCLUSIONS: Vascular surgeons should be aware of EPR during the performance of their duties. Procedure type and surgical adjuncts can alter EPR significantly.

Application and Reliability of Accelerometer-Based Arm Use Intensities in the Free-Living Environment for Manual Wheelchair Users and Able-Bodied Individuals.

Arm use in manual wheelchair (MWC) users is characterized by a combination of overuse and a sedentary lifestyle. This study aimed to describe the percentage of daily time MWC users and able-bodied individuals spend in each arm use intensity level utilizing accelerometers. Arm use intensity levels of the upper arms were defined as stationary, low, mid, and high from the signal magnitude area (SMA) of the segment accelerations based on in-lab MWC activities performed by eight MWC users. Accelerometry data were collected in the free-living environments from forty MWC users and 40 sex- and age-matched able-bodied individuals. The SMA intensity levels were applied to the free-living data and the percentage of time spent in each level was calculated. The SMA intensity levels were defined as, stationary: ≤0.67 g, low: 0.671-3.27 g, mid: 3.27-5.87 g, and high: >5.871 g. The dominant arm of both MWC users and able-bodied individuals was stationary for most of the day and less than one percent of the day was spent in high intensity arm activities. Increased MWC user age correlated with increased stationary arm time (R = 0.368, p = 0.019). Five and eight days of data are needed from MWC users and able-bodied individuals, respectively, to achieve reliable representation of their daily arm use intensities.

Validation of Inertial Measurement Units for Upper Body Kinematics.

The purpose of this study was to validate a commercially available inertial measurement unit (IMU) system against a standard lab-based motion capture system for the measurement of shoulder elevation, elbow flexion, trunk flexion/extension, and neck flexion/extension kinematics. The validation analyses were applied to 6 surgical faculty members performing a standard, simulated surgical training task that mimics minimally invasive surgery. Three-dimensional joint kinematics were simultaneously recorded by an optical motion capture system and an IMU system with 6 sensors placed on the head, chest, and bilateral upper and lower arms. The sensor-to-segment axes alignment was accomplished manually. The IMU neck and trunk IMU flexion/extension angles were accurate to within 2.9 ± 0.9 degrees and 1.6 ± 1.1°, respectively. The IMU shoulder elevation measure was accurate to within 6.8 ± 2.7° and the elbow flexion measure was accurate to within 8.2 ± 2.8°. In the Bland-Altman analyses, there were no significant systematic errors present; however, there was a significant inversely proportional error across all joints. As the gold standard measurement increased, the IMU underestimated the magnitude of the joint angle. This study reports acceptable accuracy of a commercially available IMU system; however, results should be interpreted as protocol specific.

Posture and movement classification: the comparison of tri-axial accelerometer numbers and anatomical placement.

Patient compliance is important when assessing movement, particularly in a free-living environment when patients are asked to don their own accelerometers. Reducing the number of accelerometers could increase patient compliance. The aims of this study were (1) to determine and compare the validity of different accelerometer combinations and placements for a previously developed posture and dynamic movement identification algorithm. Custom-built activity monitors, each containing one tri-axial accelerometer, were placed on the ankles, right thigh, and waist of 12 healthy adults. Subjects performed a protocol in the laboratory including static orientations of standing, sitting, and lying down, and dynamic movements of walking, jogging, transitions between postures, and fidgeting to simulate free-living activity. When only one accelerometer was used, the thigh was found to be the optimal placement to identify both movement and static postures, with a misclassification error of 10%, and demonstrated the greatest accuracy for walking/fidgeting and jogging classification with sensitivities and positive predictive value (PPVs) greater than 93%. When two accelerometers were used, the waist-thigh accelerometers identified movement and static postures with greater accuracy than the thigh-ankle accelerometers (with a misclassification error of 11% compared to 17%). However, the thigh-ankle accelerometers demonstrated the greatest accuracy for walking/ fidgeting and jogging classification with sensitivities and PPVs greater than 93%. Movement can be accurately classified in healthy adults using tri-axial accelerometers placed on one or two of the following sites: waist, thigh, or ankle. Posture and transitions require an accelerometer placed on the waist and an accelerometer placed on the thigh.

Assessment of gait kinetics using triaxial accelerometers.

Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations, and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 [19-34] years) performed 8-10 walking trials at velocities ranging from 0.19 to 3.05 m/s while wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r² > .53, P < .001), ankle peak vertical accelerations were the most correlated (r² > .75, P < .001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r² > .57, P < .001), with waist peak resultant acceleration being the most correlated (r² > .70, P < .001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health.

Accelerations of the waist and lower extremities over a range of gait velocities to aid in activity monitor selection for field-based studies.

This study aimed to define accelerations measured at the waist and lower extremities over a range of gait velocities to provide reference data for choosing the appropriate accelerometer for field-based human activity monitoring studies. Accelerations were measured with a custom activity monitor (± 16g) at the waist, thighs, and ankles in 11 participants over a range of gait velocities from slow walking to running speeds. The cumulative frequencies and peak accelerations were determined. Cumulative acceleration amplitudes for the waist, thighs, and ankles during gait velocities up to 4.8 m/s were within the standard commercial g-range (± 6g) in 99.8%, 99.0%, and 96.5% of the data, respectively. Conversely, peak acceleration amplitudes exceeding the limits of many commercially available activity monitors were observed at the waist, thighs, and ankles, with the highest peaks at the ankles, as expected. At the thighs, and more so at the ankles, nearly 50% of the peak accelerations would not be detected when the gait velocity exceeds a walking velocity. Activity monitor choice is application specific, and investigators should be aware that when measuring high-intensity gait velocity activities with commercial units that impose a ceiling at ± 6g, peak accelerations may not be measured.

Development and evaluation of the ARM algorithm: A novel approach to quantify musculoskeletal disorder risk factors in manual wheelchair users in the real world.

This study aimed to develop and evaluate the ARM (arm repetitive movement) algorithm using inertial measurement unit (IMU) data to assess repetitive arm motion in manual wheelchair (MWC) users in real-world settings. The algorithm was tested on community data from four MWC users with spinal cord injury and compared with video-based analysis. Additionally, the algorithm was applied to in-home and free-living environment data from two and sixteen MWC users, respectively, to assess its utility in quantifying differences across activities of daily living and between dominant and non-dominant arms. The ARM algorithm accurately estimated active and resting times (>98%) in the community and confirmed asymmetries between dominant and non-dominant arm usage in in-home and free-living environment data. Analysis of free-living environment data revealed that the total resting bout time was significantly longer (P = 0.049) and total active bout time was significantly shorter (P = 0.011) for the non-dominant arm. Analysis of active bouts longer than 10 seconds showed higher total time (P = 0.015), average duration (P = 0.026), and number of movement cycles per bout (P = 0.020) for the dominant side. These findings support the feasibility of using the IMU-based ARM algorithm to assess repetitive arm motion and monitor shoulder disorder risk factors in MWC users during daily activities.

Estimation of manual wheelchair-based activities in the free-living environment using a neural network model with inertial body-worn sensors.

Shoulder pain is common in manual wheelchair (MWC) users. Overuse is thought to be a major cause, but little is known about exposure to activities of daily living (ADLs). The study goal was to develop a method to estimate three conditions in the field: (1) non-propulsion activity, (2) MWC propulsion, and (3) static time using an inertial measurement unit (IMU). Upper arm IMU data were collected as ten MWC users performed lab-based MWC-related ADLs. A neural network model was developed to classify data as non-propulsion activity, propulsion, or static, and validated for the lab-based data collection by video comparison. Six of the participants' free-living IMU data were collected and the lab-based model was applied to estimate daily non-propulsion activity, propulsion, and static time. The neural network model yielded lab-based validity measures ≥0.87 for differentiating non-propulsion activity, propulsion, and static time. A quasi-validation of one participant's field-based data yielded validity measures ≥0.66 for identifying propulsion. Participants' estimated mean daily non-propulsion activity, propulsion, and static time ranged from 158 to 409, 13 to 25, and 367 to 609 min, respectively. The preliminary results suggest the model may be able to accurately identify MWC users' field-based activities. The inclusion of field-based IMU data in the model could further improve field-based classification.

Duration of Static and Dynamic Periods of the Upper Arm During Daily Life of Manual Wheelchair Users and Matched Able-Bodied Participants: A Preliminary Report.

Background: Manual wheelchair (MWC) users with spinal cord injuries (SCI) are at a significantly higher risk of experiencing rotator cuff pathology than able-bodied individuals. A deeper understanding of where the arm is used dynamically within the humeral workspace during daily life may help explain why MWC users have higher shoulder pathology rates than able-bodied individuals. The purpose of this study was to report the daily percentage and consecutive durations MWC users and matched able-bodied individuals (controls) spent static and dynamic across the humeral elevation workspace. Methods: MWC users with SCI and controls wore three inertial measurement units on their bilateral arms and torso for 1 or 2 days. The percentages of time and average consecutive duration individuals were static or dynamic while in five humeral elevation ranges (0-30°, 30-60°, 60-90°, 90-120°, and >120°) were calculated and compared between cohorts. Results: Forty-four MWC users (10 females, age: 42.8 ± 12.0, time since injury: 12.3 ± 11.5) and 44 age- and sex-matched controls were enrolled. The MWC cohort spent significantly more time dynamic in 60-90° (p = 0.039) and 90-120° (p = 0.029) and had longer consecutive dynamic periods in 30-60° (p = 0.001), 60-90° (p = 0.027), and 90-120° (p = 0.043) on the dominant arm. The controls spent significantly more time dynamic in 0-30° of humeral elevation (p < 0.001) on both arms. Although the average consecutive static durations were comparable between cohorts across all humeral elevation ranges, the MWC cohort spent a significantly higher percentage of their day static in 30-60° of humeral elevation than controls (dominant: p = 0.001, non-dominant: p = 0.01). The MWC cohort had a moderate association of increased age with decreased time dynamic in 30-60° for both arms. Discussion: Remote data capture of arm use during daily life can aid in understanding how arm function relates to shoulder pathology that follows SCI and subsequent MWC use. MWC users spent more time dynamic in higher elevations than controls, and with age, dynamic arm use decreased in the 30-60° humeral elevation range. These results may exemplify effects of performing activities from a seated position and of age on mobility.

Humeral elevation workspace during daily life of adults with spinal cord injury who use a manual wheelchair compared to age and sex matched able-bodied controls.

Shoulder pain and pathology are extremely common for individuals with spinal cord injuries (SCI) who use manual wheelchairs (MWC). Although risky humeral kinematics have been measured during wheelchair-based activities performed in the lab, little is known about arm kinematics in the free-living environment. The purpose of this study was to measure the humeral elevation workspace throughout a typical day for individuals with SCI who use a MWC and matched able-bodied controls. Thirty-four individuals with SCI who use a MWC (42.7±12.7 years of age, 28 males/6 females, C6-L1) and 34 age-and sex-matched controls were enrolled. Participants wore three inertial measurement units (IMU) on their upper arms and torso for one to two days. Humeral elevation angles were estimated and the percentage of time individuals spent in five elevation bins (0-30°, 30-60°, 60-90°, 90-120°, and 120-180°) were calculated. For both arms, the SCI cohort spent a significantly lower percentage of the day in 0-30° of humeral elevation (Dominant: SCI = 15.7±12.6%, Control = 32.1±15.6%, p<0.0001; Non-Dominant: SCI = 21.9±17.8%, Control = 34.3±15.5%, p = 0.001) and a significantly higher percentage of time in elevations associated with tendon compression (30-60° of humeral elevation, Dominant: SCI = 62.8±14.4%, Control = 49.9.1±13.0%, p<0.0001; Non-Dominant: SCI = 58.8±14.9%, Control = 48.3±13.6%, p = 0.003) than controls. The increased percentage of time individuals with SCI spent in elevations associated with tendon compression may contribute to increased shoulder pathology. Characterizing the humeral elevation workspace utilized throughout a typical day may help in understanding the increased prevalence of shoulder pain and pathology in individuals with SCI who use MWCs.

Intraoperative posture and workload assessment in vascular surgery.

Quantifying the workload and postural demand on vascular surgeons provides valuable information on the physical and cognitive factors that predispose vascular surgeons to musculoskeletal pain and disorders. The aim of this study was to quantify the postural demand, workload, and discomfort experienced by vascular surgeons and to identify procedural factors that influence surgical workload. Both objective (wearable posture sensors) and subjective (surveys) assessment tools were used to evaluate intraoperative workload during 47 vascular surgery procedures. Results demonstrate unfavorable neck and low back postures as well as high pain scores for those body segments. Additionally, workload from subjective surveys increased significantly as a function of operative duration, and mental workload was high across all procedure types. Neck postural risk exposure and physical demand were among the variables that increased with surgical duration, procedure type, and loupes used by the surgeons. Correlations among postural angles and pain scores showed consistency between the objective assessment and the subjective surveys for neck and trunk. The authors believe that the results of this study highlight the need for developing mitigating measures such as ergonomic interventions for vascular surgery.

Quality over quantity: skeletal loading intensity plays a key role in understanding the relationship between physical activity and bone density in postmenopausal women.

OBJECTIVE: Increasing physical activity (PA) is regularly cited as a modifiable target to improve health outcomes and quality of life in the aging population, especially postmenopausal women who exhibit low bone mineral density (BMD) and high fracture risk. In this cross-sectional study, we aimed to quantify real-world PA and its association with BMD in postmenopausal women. METHODS: Seventy postmenopausal women, aged 46 to 79 years, received a dual-energy X-ray absorptiometry scan measuring total hip BMD and wore bilateral triaxial accelerometers on the ankles for 7 days to measure PA in their free-living environment. Custom step detection and peak vertical ground reaction force estimation algorithms, sensitive to both quantity and intensity of PA, were used to calculate a daily bone density index (BDI) for each participant. Multiple regression was used to quantify the relationship between total hip BMD, age, step counts, and mean BDI over the span of 7 days of data collection. RESULTS: All participants completed the full 7 days of PA monitoring, totaling more than 7 million detected steps. Participants averaged 14,485 ±â€Š4,334 steps daily with mean peak vertical ground reaction force stepping loads of 675 ±â€Š121 N during daily living. Across the population, total hip BMD was found to be significantly correlated with objective estimates of mean BDI (r = 0.44), as well as participant age (r = 0.285). CONCLUSION: Despite having higher-than-expected PA, the low stepping loads observed in this cohort, along with half of the participants having low BMD measures, underscores the need for PA intensity to be considered in the management of postmenopausal bone health.

Differences in Physical Activity and Sedentary Behavior Patterns of Postmenopausal Women With Normal vs. Low Total Hip Bone Mineral Density.

Purpose: Recent evidence suggests that sedentary behavior (SB) may be associated with bone health. This study compares free-living physical activity (PA) and SB distribution patterns of postmenopausal women with normal vs. low total hip bone mineral density (BMD). Methods: Sixty nine post-menopausal women [mean (min-max) age: 61 (46-79) years] wore ActiGraph GT3X+ activity monitors on the bilateral ankles for 7 days in free-living. Participants were split into two groups: those with normal hip BMD (T-scores ≥-1.0; N = 34) and those with low hip BMD (T-scores <-1.0; N = 35) as defined by the World Health Organization. Daily active time, step counts, sedentary time, sedentary break number, and median sedentary bout length were estimated from ankle acceleration data. The distribution and accumulation patterns of time spent in sedentary bouts, sedentary breaks, and stepping bouts, and sedentary break and stepping bout lengths' variability were also investigated. Group differences were assessed using two-sampled t-tests and Mann-Whitney U-tests with significance levels of 0.5. Results: Significant between group differences (p < 0.05) were in total daily active time [median (IQR): 257 (209-326) vs. 249 (199-299) min], step count [14,188 (10,938-18,646) vs. 13,204 (10,337-16,630) steps], sedentary time [669 (584-731) vs. 687 (615-753) min], and sedentary break number [93 (68-129) breaks vs. 88 (64-113) breaks], as well as median sedentary bout length [15.1 (11.9-22.1) vs. 15.8 (12.1-24.9) min]. Participants' sedentary bouts were found to be power law distributed with 52% of sedentary time occurring in bouts ≥20 min for the normal BMD group, and 58% for the low BMD group. Significant differences were observed between groups in sedentary bouts' and sedentary breaks' power distribution exponents (p < 0.0001) and patterns of sedentary and stepping time accumulation using the Gini index (p ≤ 0.0014). Variability was significantly lower for sedentary break and stepping bout lengths for the low BMD group (p ≤ 0.0001). Participants with lower hip BMD have longer sedentary bouts with shorter and less complex activity bouts compared to participants with normal hip BMD. Conclusion: The results suggest healthier hip BMD may be associated with PA distributed more evenly throughout the day with shorter sedentary bouts. PA distribution should be considered in exercise-based bone health management programs.

Comparing supraspinatus to acromion proximity and kinematics of the shoulder and thorax between manual wheelchair propulsion styles: A pilot study.

BACKGROUND: Repetitive glenohumeral joint movement during manual wheelchair propulsion has been associated with shoulder pain in individuals with spinal cord injury. Clinical guidelines for shoulder health maintenance encourage semi-circular over arc propulsion to reduce loading frequency. This study aimed to determine the difference in estimated supraspinatus to acromion compression risk, and shoulder, thorax kinematics between (1) arc and semi-circular propulsion; and (2) self-selected and coached strategies. METHODS: Shoulder and thorax kinematics were captured during wheelchair propulsion, noting individually self-selected styles. Participants were then coached to perform the other style(s) of interest, arc and/or semi-circular. CT bone models of the humerus and scapula were animated using glenohumeral kinematics to estimate the minimum distance between the supraspinatus humeral attachment and the acromion. Compression risk was defined as the proportion of each propulsion phase where the minimum distance fell below 5 mm. Comparisons were made between conditions evaluating compression risk, minimum distances and kinematics at events throughout propulsion. FINDINGS: Ten individuals with spinal cord injury (9 male) participated. Arc and semi-circular propulsion did not significantly differ in compression risk or minimum distance across propulsion phases. Self-selected styles yielded lower compression risk and larger proximity values compared to coached styles. Glenohumeral horizontal abduction and thorax flexion differed between arc and semi-circular propulsion. Multiple glenohumeral and humerothoracic differences emerged between self-selected and coached conditions. INTERPRETATION: Supraspinatus compression was observed during both arc and semi-circular propulsion, suggesting risk may be unavoidable in this task. Self-selected styles yield less risk, likely related to coached style unfamiliarity.

Adaptive gait segmentation algorithm for walking bout detection using tri-axial accelerometers.

Gait analysis has many potential applications in understanding the activity profiles of individuals in their daily lives, particularly when studying the progression of recovery following injury, or motor deterioration in pathological conditions. One of the many challenges of conducting such analyses in the home environment is the correct and automatic identification of bouts of gait activity. To address this, a novel method for determining bouts of gait from accelerometer data recorded from the shank is presented. This method is fully automated and includes an adaptive thresholding approach which avoids the necessity for identifying subject-specific thresholds. The algorithm was tested on data recorded from 15 healthy subjects during self-selected slow, normal and fast walking speeds ranging from 0.48 ± 0.19 to 1.38 ± 0.33m/s and a single subject with PD walking at their normal walking speed (1.41 ± 0.08m/s) using accelerometers on the shanks. Intra-Class Correlation (ICC) confirmed high levels of agreement between bout onset/offset times and durations estimated using the algorithm, experimentally recorded stopwatch times and manual annotation for the healthy subjects (r=0.975, p <; 0.001; r=0.984, p<; 0.001) and moderate agreement for the PD subject (r=0.663, p<; 0.001). Mean absolute errors between accelerometer-derived and manually-annotated times were calculated, and ranged from 0.91 ± 0.05 s to 1.17 ± 2.26 s for bout onset detection, 0.80 ± 0.23 s to 2.41 ± 3.77 s for offset detection and 1.27 ± 0.13 s to 3.67 ± 4.59 s for bout durations.

Impact of Procedure Type, Case Duration, and Adjunctive Equipment on Surgeon Intraoperative Musculoskeletal Discomfort.

BACKGROUND: Surgeons are at high risk of developing musculoskeletal disorders. STUDY DESIGN: This study was designed to identify risk factors and assess intraoperative physical stressors using subjective and objective measures, including type of procedure and equipment used. Wearable sensors and pre- and postoperation surveys were analyzed. RESULTS: Data from 116 cases (34 male and 19 female surgeons) were collected across surgical specialties. Surgeons reported increased pain in the neck, upper, and lower back both during and after operations. High-stress intraoperative postures were also revealed by the real-time measurement in the neck and back. Surgical duration also impacted physical pain and fatigue. Open procedures had more stressful physical postures than laparoscopic procedures. Loupe usage negatively impacted neck postures. CONCLUSIONS: This study highlights the fact that musculoskeletal disorders are common in surgeons and characterizes surgeons' intraoperative posture as well as surgeon pain and fatigue across specialties. Defining intraoperative ergonomic risk factors is of paramount importance to protect the well-being of the surgical workforce.

Outcome Measures of Free-Living Activity in Spinal Cord Injury Rehabilitation.

PURPOSE OF REVIEW: The purpose of this article was to describe the utilization of body worn activity monitors in the SCI population and discuss the challenges of using body worn sensors in rehabilitation research. RECENT FINDINGS: Many activity monitor-based measures have been used and validated in the SCI population including stroke number, push frequency, upper limb activity counts and wheelchair propulsion distance measured from a sensor attached to the wheelchair. SUMMARY: The ability to accurately measure physical activity in the free-living environment using body-worn sensors has the potential to enhance the understanding of barriers to adequate activity and identify possible effective interventions. As the use of activity monitors used in SCI rehabilitation research continues to grow, care must be taken to overcome challenges related to participant adherence and data quality.

Assessment of gait kinetics in post-menopausal women using tri-axial ankle accelerometers during barefoot walking.

BACKGROUND: Physical activity (PA) interventions, designed to increase exposure to ground reaction force (GRF) loading, are a common target for reducing fracture risk in post-menopausal women with low bone mineral density (BMD). Unfortunately, accurate tracking of PA in free-living environments and the ability to translate this activity into evaluations of bone health is currently limited. RESEARCH QUESTION: This study evaluates the effectiveness of ankle-worn accelerometers to estimate the vertical GRFs responsible for bone and joint loading in post-menopausal women at a range of self-selected walking speeds during barefoot walking. METHODS: Seventy women, at least one year post-menopause, wore Actigraph GT3X + on both ankles and completed walking trials at self-selected speeds (a minimum of five each at fast, normal and slow walking) along a 30 m instrumented walkway with force plates and photocells to measure loading and estimate gait velocity. Repeated measures correlation analysis and step-wise mixed-effects modelling were performed to evaluate significant predictors of peak vertical GRFs normalized to body weight (pVGRFbw), including peak vertical ankle accelerations (pVacc), walking velocity (Velw) and age. RESULTS: A strong repeated measures correlation of r = 0.75 (95%CI [0.71-0.76] via 1000 bootstrap passes) between pVacc and pVGRFbw was observed. Five-fold cross-validation of mixed-model predictions yielded an average mean-absolute-error (MAE[95%CI]) and root-mean-square-error (RMSE) rate of 5.98%[5.61-6.42] and 0.076 [0.069-0.082] with a more complex model (including Velw,) and 6.80%[6.37-7.54] and 0.087BW[0.081-0.095] with a simpler model (including only pVacc), when comparing accelerometer-based estimations of pVGRFbw to force plate measures of pVGRFbw. Age was not found to be significant. SIGNIFICANCE: This study is the first to show a strong relationship among ankle accelerometry data and high fidelity lower-limb loading approximations in post-menopausal women. The results provide the first steps necessary for estimation of real-world limb and joint loading supporting the goals of accurate PA tracking and improved individualization of clinical interventions.