Amity Campbell

The Effects of Walking and Cycling Computer Workstations on Keyboard and Mouse Performance

Objective: This study aimed to determine the effects of active workstation designs on speed and error during typing, mouse pointing, and combined type and mouse-use tasks. Background: Office ergonomics has focused on musculoskeletal disorder prevention; however, increasing computer-based work also increases health risks associated with inactivity. Workstations allowing computer users to walk or cycle while performing computer tasks have been shown to demand sufficient energy expenditure to result in significant health benefits. However the performance effects of being active while using a computer have not been documented. Method: Thirty office workers (16 female, 15 touch typists) performed standardized computer tasks in six workstation conditions: sitting, standing, walking at 1.6 km/h and 3.2 km/h, and cycling at 5 and 30 watts. Performance, perceived performance, and heart rate were measured. Results: Computer task performance was lower when walking and slightly lower when cycling, compared with chair sitting. Standing performance was not different from sitting performance. Mouse performance was more affected than typing performance. Performance decrements were equal for females and males and for touch typists and nontouch typists. Conclusion: Performance decrements maybe related to both biomechanical and cognitive processes. Active workstations may be less suitable for mouse-intensive work and susceptible users. Application: Although active workstations may result in some decrement in performance, their ability to increase daily energy expenditure may make them a feasible solution for workplace inactivity.

MRI development and validation of two new predictive methods of glenohumeral joint centre location identification and comparison with established techniques.

Identification of the centre of the glenohumeral joint (GHJ) is essential for three-dimensional (3D) upper limb motion analysis. A number of convenient, yet un-validated methods are routinely used to estimate the GHJ location in preference to the International Society of Biomechanics (ISB) recommended methods. The current study developed a new regression model, and simple 3D offset method for GHJ location estimation, employing easy to administer measures, and compared the estimates with the known GHJ location measured with magnetic resonance imaging (MRI). The accuracy and reliability of the new regression and simple 3D offset techniques were compared with six established predictive methods. Twenty subjects wore a 3D motion analysis marker set that was also visible in MRI. Immediately following imaging, they underwent 3D motion analysis acquisition. The GHJ and anatomical landmark positions of 15 participants were used to determine the new regression and simple 3D generic offset methods. These were compared for accuracy with six established methods using 10 subjects data. A cross validation on 5 participants not used for regression model development was also performed. Finally, 10 participants underwent a further two MRIs and subsequent 3D motion analysis analyses for inter-tester and intra-tester reliability quantification. When compared with any of the other established methods, our newly developed regression model found an average GHJ location closer to the actual MRI location, having an GHJ location error of 13+/-2 mm, and had significantly lower inter-tester reliability error, 6+/-4 mm (p<0.01).

Translation equations to compare ActiGraph GT3X and Actical accelerometers activity counts

BackgroundThis study aimed to develop a translation equation to enable comparison between Actical and ActiGraph GT3X accelerometer counts recorded minute by minute.MethodsFive males and five females of variable height, weight, body mass index and age participated in this investigation. Participants simultaneously wore an Actical and an ActiGraph accelerometer for two days. Conversion algorithms and R2 were calculated day by day for each subject between the omnidirectional Actical and three different ActiGraph (three-dimensional) outputs: 1) vertical direction, 2) combined vector, and 3) a custom vector. Three conversion algorithms suitable for minute/minute conversions were then calculated from the full data set.ResultsThe vertical ActiGraph activity counts demonstrated the closest relationship with the Actical, with consistent moderate to strong conversions using the algorithm: y = 0.905x, in the day by day data (R2 range: 0.514 to 0.989 and average: 0.822) and full data set (R2 = 0.865).ConclusionsThe Actical is most sensitive to accelerations in the vertical direction, and does not closely correlate with three-dimensional ActiGraph output. Minute by minute conversions between the Actical and ActiGraph vertical component can be confidently performed between data sets and might allow further synthesis of information between studies.

The Relationship Between Back Muscle Endurance and Physical, Lifestyle, and Psychological Factors in Adolescents

STUDY DESIGN Cross-sectional investigation. BACKGROUND There is some evidence that interventions directed to improving back muscle endurance (BME) in adolescents are effective in reducing low back pain, with anecdotal evidence of improved performance. However, the mechanisms responsible for this improvement remain unclear. OBJECTIVE To identify the relationship between physical, lifestyle, and psychological variables and BME in a large adolescent population, while controlling for back pain and gender. METHODS One thousand four-hundred thirty-five adolescents (702 females, 733 males; mean +/- SD age, 14.0 +/- 0.2 years) completed a range of physical, lifestyle, and psychological assessments. The group mean +/- SD height and body mass were 164 +/- 8 cm and 57.1 +/- 12.6 kg, respectively. Linear regression was used to investigate the univariate association between each of the physical, lifestyle, and psychological variables and BME. Backwards stepwise multivariate linear regression was used to determine statistically significant independent correlates of BME. RESULTS The final multivariate model explained 15.3% of the variance in BME and included at least 1 variable from the physical, lifestyle, and psychological domains. Adolescents who exercised less, watched more television, had a higher body mass index, sat in a more flexed trunk posture (more slumped), and had lower self-efficacy had lower BME. CONCLUSIONS All the physical and lifestyle variables linked with poorer BME performance in this investigation are indicative of reduced back muscle activation and/or deconditioning. Psychological predictors may have direct and/or indirect links with BME.

Self-reported prevalence, pain intensity and risk factors of low back pain in adolescent rowers.

OBJECTIVES The primary objective of this study was to determine the lifetime and point prevalence of low back pain, the related pain intensity and the rowing-related aggravating factors for low back pain in adolescent rowers who participated in school-level competitions. The secondary objective was to determine whether between-gender differences existed in these data. DESIGN Retrospective cross-sectional survey METHODS 130 adolescent male and 235 adolescent female rowers aged between 14 and 16 years were recruited in this study. Participants completed a questionnaire to determine their lifetime and point prevalence of low back pain, their pain intensity and rowing-related factors that aggravated their low back pain. RESULTS A high lifetime and point prevalence of low back pain were found in both adolescent male (93.8% and 64.6%, respectively) and female (77.9% and 52.8%, respectively) rowers. A significant between-gender difference was reported for both statistics (p<0.001). A significantly lower (p=0.003) level of pain intensity via a visual analog scale was found for males (4.1/10) when compared to females (5.0/10). Similar rowing-related aggravating factors were reported by males and females although fewer males reported that lifting the rowing shell aggravated their low back pain. CONCLUSIONS A high lifetime and point prevalence of low back pain was reported by the adolescent rowers recruited in this study. While a greater proportion of adolescent male rowers reported low back pain, they reported a lower intensity of pain when compared to their female counterparts. Coaches, clinicians and rowers should be made aware of these findings such that future research and development can focus on promoting pain management strategies in this sport.

Capturing the Pattern of Physical Activity and Sedentary Behavior: Exposure Variation Analysis of Accelerometer Data

BACKGROUND Capturing the complex time pattern of physical activity (PA) and sedentary behavior (SB) using accelerometry remains a challenge. Research from occupational health suggests exposure variation analysis (EVA) could provide a meaningful tool. This paper (1) explains the application of EVA to accelerometer data, (2) demonstrates how EVA thresholds and derivatives could be chosen and used to examine adherence to PA and SB guidelines, and (3) explores the validity of EVA outputs. METHODS EVA outputs are compared with accelerometer data from 4 individuals (Study 1a and 1b) and 3 occupational groups (Study 2): seated workstation office workers (n = 8), standing workstation office workers (n = 8), and teachers (n = 8). RESULTS Line graphs and related EVA graphs highlight the use of EVA derivatives for examining compliance with guidelines. EVA derivatives of occupational groups confirm no difference in bouts of activity but clear differences as expected in extended bouts of SB and brief bursts of activity, thus providing evidence of construct validity. CONCLUSIONS EVA offers a unique and comprehensive generic method that is able, for the first time, to capture the time pattern (both frequency and intensity) of PA and SB, which can be tailored for both occupational and public health research.

The lumbar spine of the young cricket fast bowler: An MRI study

OBJECTIVES To describe the prevalence and nature of lumbar spinal abnormalities in adolescent cricket fast bowlers. DESIGN Observational study. METHODS 46 asymptomatic fast bowlers aged 13-18 years participated in the study and were grouped into under-15 (U15), under-17 (U17) and under-19 (U19) classifications. All participants underwent magnetic resonance imaging of the lumbar spine and abnormalities of the pars interarticularis and intervertebral discs were graded according to type and severity. Other abnormalities were also noted. RESULTS Fifteen bowlers (33%) had at least one pars interarticularis abnormality. Six bilateral and 10 unilateral defects were identified. Of the 10 unilateral pars abnormalities, 6 occurred on the non-dominant side. Nineteen of the abnormalities occurred at the L5 vertebral level, 2 at L4 and 1 at L3. The most common type of pars abnormality was the subtotal stress fracture, which was found in 38% of bowlers aged 16 years and under. Sixteen participants (35%) were found to have degeneration of at least 1 lumbar disc and the prevalence increased with each successive age group (29% U15, 33% U17 and 43% U19). Of the 25 discs with signs of degeneration, 9 occurred at L4/5 and 7 at L5/S1. Eleven of these were classified as mild degeneration, 13 as moderate, and 1 as severe. Disc bulges were found in 33% of participants. CONCLUSIONS Lumbar radiological abnormalities are common in asymptomatic adolescent fast bowlers. Acute bone stress reactions of the lumbar pars interarticularis are visible on magnetic resonance imaging and, in some instances, occur before the onset of activity-related pain.

In vivo laboratory validation of the physiometer: a measurement system for long-term recording of posture and movements in the workplace

Posture and movement are thought to be important risk factors for the development of work-related musculoskeletal disorders. Whole day occupational exposure assessment has typically used self-report or observation techniques, but the need for more accurate measurement is now recognised. The aim of this study was to compare the kinematic recordings of a frequently used field system (physiometer) with two laboratory-based systems (Fastrak and Peak) in vivo. Head, thorax and right arm kinematics were recorded simultaneously by the three systems whilst a subject performed 27 single and multiple plane physiological and simulated daily living task movement trials. Errors observed in the Fastrak and Peak data included gimbal lock and quadrant errors. Physiometer data errors included undervalues, overvalues and temporal errors of slow response and resonance. All three systems showed some cross-talk. Agreement between the physiometer and the other systems was generally high for physiological movements (R2 > 0.8) and less for functional movements (R2 > 0.5). Statement of Relevance: The physiometer recording device can provide an indication of posture across time in the workplace; however, its accuracy is limited, particularly during functional movements. Further technology should be developed to unobtrusively capture accurate all day 3-D kinematics.

Lumbar load in adolescent fast bowlers: A prospective injury study

OBJECTIVES This study aimed to identify modifiable mechanisms associated with low back injury in adolescent cricket fast bowlers. DESIGN A prospective study design examined the association between intrinsic risk factors, workload, bowling kinematics, lumbar load and low back injury incidence. METHODS Twenty-five injury free fast bowlers, aged 14-19 years, were assessed prior to the start of a cricket season and observed during the season for low back injuries. RESULTS The twelve bowlers who suffered a low back injury displayed; decreased hip flexion at front foot contact (46±6° vs 51±6°), increased pelvis rotation (287±11° vs 277±11°) increased thorax lateral flexion (50±6° vs 40±8°) at ball release, and larger peak lumbar flexion (10.5±4.9Nmkg(-1)m(-1) vs 6.9±2.5Nmkg(-1)m(-1)) and lateral flexion moments (12.5±2.6Nmkg(-1)m(-1) vs 10.6±1.9Nmkg(-1)m(-1)). They also exhibited reduced muscular endurance of the back extensors (103±33s vs 132±33s) and increased knee valgus angle during a single leg decline squat on the dominant (9±3° vs 5±4°) and non-dominant leg (9±4° vs 6±3°) in comparison to uninjured bowlers. CONCLUSIONS Bowlers who experience greater lumbar loads during bowling, have reduced back extensor muscle endurance, and demonstrate impaired control of the lumbo-pelvic-hip complex, are at increased risk of low back injury. This combination of strength, control and biomechanical factors may be key mechanical elements of low back injury causation in adolescent fast bowlers.

Lumbo-Pelvic Biomechanics and Quadratus Lumborum Asymmetry in Cricket Fast Bowlers

PURPOSE This study aimed to analyze lumbo-pelvic lateral flexion kinematics and kinetics in junior fast bowlers and compare bowlers with varying quadratus lumborum (QL) cross-sectional area (CSA) asymmetry profiles. METHODS Magnetic resonance imaging was used to determine QL CSA of 39 participants who also underwent three-dimensional analysis of their bowling action. RESULTS Bowlers with greater than 10% QL asymmetry (n = 26) experienced a larger peak lumbo-pelvic lateral flexion; angle (21.6° ± 4.2°), angular velocity (314.9°·s ± 86.6°·s), moment (12.8 ± 2.5 N·m·kg·m), positive power (25.6 ± 12.6 W·kg·m), and negative power (48.6 ± 20.9 W·kg·m) compared with the bowlers with less than 10% asymmetry (n = 13) (angle = 18.1° ± 1.9°, angular velocity = 243.8°·s ± 64.9°·s, moment = 10.4 ± 2.8 N·m·kg·m, positive power = 14.7 ± 7.4 W·kg·m, and negative power = 33.8 ± 17.7 W·kg·m; P < 0.05). CONCLUSION Fast bowlers with QL CSA asymmetry in excess of 10% experience increased lumbo-pelvic lateral flexion loads during bowling. As increased lateral flexion loads may increase the risk of spondylolysis development, the presence of large QL asymmetry may be a useful screening tool for identifying bowlers at risk of developing lumbar spondylolysis.