Exposure Variation Analysis Research Articles

Exposure to inclined trunk postures in surgical staff

In surgical staff, low-back pain (LBP) is prevalent and prolonged trunk inclination is hypothesized to be one of its potential causes. The aim of this study was to evaluate the magnitude and duration of trunk inclination in the sagittal plane of surgical assistants during surgical procedures. The three-dimensional trunk orientation was measured in 91 surgical assistants across four medical facilities during surgical procedures using an inertial measurement unit on the thorax. Per participant, Exposure Variation Analysis was used to evaluate the percentage of the total time of trunk inclination (< -10° (backward inclination); -10–10° (upright posture); 10–20° (light inclination); 20–30° (moderate inclination); >30° (strong inclination)) taking into account posture duration (< 10 s; 10–60 s; 60–300 s; > 300 s). Participants reported their LBP history and perceived low-back load during the procedure via a questionnaire. Participants were in an upright posture for 75% [63–84%] (median [interquartile range]) of the total surgery time (average surgery time: 174 min). Trunk inclination was beyond 20° and 30° for 4.3% [2.1–8.7%] and 1.5% [0.5–3.2%] of the surgery time, respectively. In most of the participants, the duration of trunk inclination beyond 20° or 30° was less than 60 s. Questionnaire response rate was 81%. Persistent or repeated LBP was reported by 49% of respondents, and was unrelated to the exposure to inclined trunk postures. It is concluded that other factors than prolonged trunk inclination, for instance handling of loads or prolonged standing may be causally related to the reported LBP in the investigated population.

Characterization of Occupational Lifting Patterns with Exposure Variation Analysis. Cross-sectional Workplace Study among Blue-Collar Workers.

To investigate and characterize the influence of sex, age, muscle strength, and cardiovascular fitness on manual lifting patterns using exposure variation analysis (EVA) during a full working day among blue-collar workers. Muscular activity (surface electromyography [sEMG]) of the thigh, low-back, and shoulder was measured throughout the working day in 173 employees with manual lifting tasks from 14 workplaces. Relative sEMG loading was expressed as % of maximal voluntary contraction (MVC). As an additional and more practically oriented analysis, calibration of load from standardized box lifts (5, 10, 20, and 30 kg) identified corresponding sEMG values in kg. Using an EVA 'lifting periods' of [1 to 5, >5 to 10, >10 to 20, >20 to 30, and >30] kg in time intervals [0 to 0.5, >0.5 to 1, >1 to 2, >2 to 5, >5 to 10, and >10] s were identified. Arm elevation and back inclination were measured using accelerometers. Females and older workers (≥50 years) primarily used the thighs for lifting and were exposed to more frequent thigh muscle 'lifting periods' of varying duration and load and performed more thigh lifts >30 kg and >60% of MVC compared with males and younger workers (P < 0.05). Females had less brief shoulder lifting periods and more work with bent back >30° than the males (P < 0.05), whereas stronger workers performed more work with elevated arm >60° and >90° than workers with low muscle strength (P < 0.05). However, besides a single difference where workers with lower cardiovascular fitness were exposed to more light (1-5 kg) and moderate duration (5-10 s) trapezius loading, the number of lifting periods was not affected by muscle strength nor cardiovascular fitness (P > 0.05). This EVA demonstrated sex- and age-related differences in exposure to lifting periods involving shoulder and thigh muscles.

Comparison between two mobile applications measuring shoulder elevation angle–A validity and feasibility study

Pain in the shoulder complex affects the working population where work with elevated arms is a risk factor. The aim of the present study was to compare a mobile application for measurements of arm elevation, ErgoExposure, against an existing mobile application, ErgoArmMeter, in a laboratory setting and to test the feasibility in a field trial. Eleven persons performed three tasks in the laboratory setting: static, dynamic, and simulated work tasks, where the applications were validated against an optical tracking system (OTS). Also, ErgoExposure was tested by a teacher in a real-world situation. Limits of agreement for the static task varied between -6.1° to 4.2° (ErgoExposure) and between -7.6° to 5.2° (ErgoArmMeter). The average root mean square difference for dynamic and simulated work tasks was 3.4° (ErgoExposure) and 7.7° (ErgoArmMeter). From the field trial, different work tasks produced distinct exposure variation analysis patterns. Both apps showed similar results compared to OTS, but ErgoExposure was more accurate than ErgoArmMeter.

Trunk Flexion Monitoring among Warehouse Workers Using a Single Inertial Sensor and the Influence of Different Sampling Durations.

Trunk flexion represents a risk factor for the onset of low-back disorders, yet limited quantitative data exist regarding flexion exposures in actual working conditions. In this study, we evaluated the potential of using a single inertial measurement unit (IMU) to classify trunk flexion, in terms of amplitude, frequency, and duration, and assessed the influence of alternative time durations on exposure results. Twelve warehouse workers were monitored during two hours of an actual shift while wearing a single IMU on their low back. Trunk flexion data were reduced using exposure variation analysis integrated with recommended exposure thresholds. Workers spent 5.1% of their working time with trunk flexion of 30–60° and 2.3% with flexion of 60–90°. Depending on the level of acceptable error, relatively shorter monitoring periods (up to 50 min) might be sufficient to characterize trunk flexion exposures. Future work is needed, however, to determine if these results generalize to other postural exposures and tasks.

Surgeons' posture and muscle strain during laparoscopic and robotic surgery.

It is assumed that conventional laparoscopy (LAP) and robotic-assisted laparoscopic surgery (RALS) differ in terms of the surgeon's comfort. This study compared muscle workload, work posture and perceived physical exertion of surgeons performing LAP or RALS. Colorectal surgeons with experience in advanced LAP and RALS performed one of each operation. Bipolar surface electromyography (EMG) recordings were made from forearm, shoulder and neck muscles, and expressed relative to EMG maximum (%EMGmax ). The static, median and peak levels of muscle activity were calculated, and an exposure variation analysis undertaken. Postural observations were carried out every 10 min, and ratings of perceived physical exertion before and after surgery were recorded. The study included 13 surgeons. Surgeons performing LAP showed higher static, median, and peak forearm muscle activity than those undertaking RALS. Muscle activity at peak level was higher during RALS than LAP. Exposure variation analysis demonstrated long-lasting periods of low-level intensity muscle activity in the shoulders for LAP, in the forearms for RALS, and in the neck for both procedures. Postural observations revealed a greater need for a change in work posture when performing LAP compared with RALS. Perceived physical exertion was no different between the surgical modalities. Minimally invasive surgery requires long-term static muscle activity with a high physical workload for surgeons. RALS is less demanding on posture.

Trapezius muscle activity variation during computer work performed by individuals with and without neck-shoulder pain

This study aimed at determining the extent to which individuals with neck-shoulder pain and non-symptomatic individuals differ in muscle activation patterns, when performing computer work, as quantified by exposure variation analysis (EVA). As a secondary aim, we also aimed to quantify the day-to-day reliability of EVA variables describing trapezius muscle activation in a non-symptomatic control group. Thirteen touch-typing computer users (pain: n = 5, non-symptomatic: n = 8) completed three pre-selected computer tasks in the laboratory. Upper trapezius muscle activity was recorded using electromyography and analyzed using EVA with five amplitude and five duration categories. Individuals with neck-shoulder pain spent less time at low amplitudes and exhibited longer uninterrupted periods of muscle activation compared to their non-symptomatic counterparts. Thus, non-symptomatic workers tended to switch between exposure levels more often than individuals with pain. For a majority of EVA variables, ICCs ranged from 0.6 to 0.9, and between-days coefficients of variation were between 0.4 and 2.2.

The Influence of Pleasure and Attentional Focus on Performance and Pacing Strategies in Elite Individual Time Trials.

To determine the impact of pacing strategies on cyclists' mean PO during an elite TT championship and to identify the relationships between these pacing strategies and psychological parameters. Mean PO, projected frontal area, attentional focus, and pleasure were recorded for 9 male cyclists during an official individual TT national championship. Pacing regulations were quantified from PO using the new exposure variation analysis, which determines times spent at adapted PO for optimal constant-pacing strategy (APO) and inaccurate PO for optimal constant-pacing strategy (IPO). Relationships between mean PO, times spent at APO and IPO, and psychological variables were analyzed. Significant relationships were found between mean PO and exposure variation analysis pacing parameters (r2 .56-.86, P > .05). Time spent at IPO was negatively related to pleasure during the individual TT (r = -.746, P = .016). Conversely, time spent at APO was significantly related to cyclists' attentional focus (r = .827, P = .006). Mean PO during elite individual TTs is directly related to athletes' ability to optimally regulate pace throughout the event. This pacing regulation is influenced by attentional focus and pleasure, underlining that coaches and athletes should devote greater attention to these psychological parameters to improve their performances.

The new Exposure Variation Analysis (EVA) method to compare pacing strategy and performance during professional time-trial competitions

Abstract: Several studies underlined the impact of pacing strategy on cycling time-trial performance. It has been reported that under steady environmental conditions, maintaining a constant power output (PO) is the most efficient strategy to improve performance (Wells et al. 2013). The Exposure Variation Analysis (EVA) method has recently been proposed to evaluate these pacing strategies, quantifying for an optimal constant pacing strategy the times spent at an accurate PO (APO), at an inappropriate PO (IPO), and the short-time regulations of inappropriate PO (REG) (Ouvrard et al. 2017). It has been demonstrated that increasing time spent at APO and decreasing time spent at IPO allows cyclists to develop higher mean PO and improve performance (Ouvrard et al. 2018. Under review). However, as these indexes are influenced by time-trials course, they were never used to monitor pacing strategies and performance for several time-trials performed by the same cyclists yet. The aim of this study was to analyse the relationships between changes of performance, mean PO and EVA pacing parameters in two professional cyclists during seven official competitive time-trials.  Methods: PO were collected for two professional cyclists (mean VO 2 max 79.0 ± 8.5 mL.min -1 .kg -1 ) during the seven-same time-trials (performed between April 2013 and June 2017 and ranged from 18.7 to 51.6 km). PO fluctuations were analysed from EVA to quantify times spent at APO (PO between 90 and 110 % of mean time-trial PO), IPO (PO lower than 90 % or higher than 110 % of mean PO for more than 10 s) and REG (PO lower than 90 % or higher than 110 % of mean PO for less than 10 s). Relationships between I” meanPO (differences between subject 1 and subject 2 mean PO for each time-trial) and I” meanPO% (differences between subject 1 and subject 2 mean PO, each expressed as a percentage of the subject’s record PO on the time trial duration) and I” APO (differences between subject 1 and subject 2 times spent at APO), I” IPO (differences between subject 1 and subject 2 times spent at IPO), and I” REG (differences between subject 1 and subject 2 REG) were assessed thanks to Pearson correlation coefficients.  Results: I” meanPO ranged from -24 to +39 W for similar physical potentials (20-min record PO 432 vs 428 W). A trend to a negative relationship was identified between I” meanPO and I” IPO (r = -0.70, p = 0.08). Stronger and significant relationships were identified between I” meanPO% and I” IPO (r = -0.94, p = 0.002) and I” APO (r = 0.86, p = 0.01, Figure 1).  Discussion: The main finding of this study is that, when comparing two cyclists during several time-trials, changes of EVA pacing parameters were related to changes of cyclists’ ability to develop high mean PO. The more the cyclists were able to decrease their time spent at IPO and increase their time spent at APO, the more they had a maximal use of their physical capacity during the time-trial, allowing them to develop higher mean PO expressed as a percentage of their record PO. These results are in accordance with Wells et al. (2013), who demonstrated that maintaining a constant PO, and thus increasing time spent at APO, is optimal for time-trial performance under steady environmental conditions. Conversely, increasing PO variations, and consequently time spent at IPO or REG, reflect poor adherence to constant speed, increasing biomechanical losses or fatigue.  Conclusion: EVA seems to be a valuable method to monitor pacing and performance changes for two cyclists during several time-trials.  Values of times spent at IPO and APO can be compared between cyclists to determine if their pacing strategy were optimal to achieve the best performance possible.

Differences in trapezius muscle activation patterns in office workers with and without chronic neck-shoulder pain, as quantified through exposure variation analysis

The purpose of this study was to quantify upper-trapezius muscle activation patterns using exposure variation analysis (EVA) in healthy computer workers and those with chronic neck-shoulder pain. Eight healthy and five chronic pain participants were asked to complete three computer-based tasks (TYPE, CLICK, and FORM) in two pacing conditions (self-paced and control-paced). EVA was used to quantify variation using five amplitude classes and five duration classes. Performance in each task was also quantified. Healthy workers and those with chronic pain did not differ in performance, and they both exhibited similarly low levels of muscle activation amplitude. Pain participants, however, were found to spend less time in lower duration classes across tasks and conditions. These results indicate that individuals with chronic neck-shoulder pain utilize movement strategies involving sustained durations of continuous muscle activation. This may be suggestive of decreased temporal variation in muscle activation patterns in those with chronic pain.

Estimation of physical workload of the low-back based on exposure variation analysis during a full working day among male blue-collar workers. Cross-sectional workplace study

This study aims to quantify physical workload of the low-back using exposure variation analysis (EVA) during a full working day among blue-collar workers with manual lifting tasks. One hundred and ten male employees (39 warehouse workers, 27 operators, 24 postal workers and 20 slaughterhouse workers) with manual lifting tasks from 12 workplaces participated. The workers performed standardized box lifts using 5, 10, 20 and 30 kg before and after a working day. Muscular activity of the low-back was measured throughout the working day using surface electromyography (sEMG). Corresponding sEMG-values for 0–30 kg lifts were identified using linear regression. EVA at exposure levels corresponding to “lifting periods” of [1-5, 5-10, 10-20, 20-30 and >30] kg in time intervals [0–0.5, 0.5–1, 1-2, 2-5, 5-10, >10] sec was computed. Back inclination was measured using tri-axial accelerometers. Compared to the other job groups, the operators’ low-back muscles were exposed to more short duration “lifting periods” with varying loads and more frequent medium duration high load “lifting periods”, respectively. The operators also worked more with their back inclined (>30°, >60°, and >90°) than the remaining job groups. Nonetheless, more than 41% of the workers performed heavy “lifting periods” that exceeded Danish lifting guidelines. This EVA demonstrates that almost half of the blue-collar workers were exposed to heavy low-back loading which puts them at risk of developing musculoskeletal disorders and low-back injury. Operators are, in particular, exposed to more short duration and medium duration “lifting periods” with varying load compared to warehouse-, postal- and slaughterhouse workers.

Can exposure variation be promoted in the shoulder girdle muscles by modifying work pace and inserting pauses during simulated assembly work?

This study investigated the acute effects of changing the work pace and implementing two pause types during an assembly task. Eighteen healthy women performed a simulated task in four different conditions: 1) slow or 2) fast work pace with 3) passive or 4) active pauses every two minutes. The root mean square (RMS) and exposure variation analysis (EVA) from the trapezius and serratus anterior muscles, as well as the rate of perceived exertion (RPE) from the neck-shoulder region, were observed. Decreased RMS and RPE as well as more variable muscle activity (EVA) were observed in the slow work pace compared with the fast one. The pause types had a limited effect, but active pauses resulted in increased RMS of the clavicular trapezius. The findings revealed the importance of work pace in the reduction of perceived exertion and promotion of variation in muscle activation during assembly tasks. However, the pause types had no important effect on the evaluated outcomes.

Exposure Variation Analysis (EVA) method to monitor ability to optimally regulate exercise intensity of professional cyclists during time-trial competitions

Introduction Pacing strategies during endurance performance is becoming one of the main topics in sport sciences. Several studies proved that a constant pacing strategy, adjusted from course main difficulties, is optimal for individual time-trial (ITT) performance. However, the regulation mechanisms that allow athletes to maintain a constant power output (PO) remain poorly studied (Abbiss and Laursen 2008). The “Exposure Variation Analysis” (EVA) was recently proposed as a new innovative method to quantify short-time PO fluctuations during ITT (Abbiss et al. 2010; Peiffer and Abbiss 2011). This method appears to offer an interesting way to investigate the athlete ability to optimally regulate exercise intensity during ITT in order to maintain a constant optimal pacing strategy. The aim of this study was to assess the relationship between the exercise intensity regulation mechanisms quantified thanks to the EVA method and the evolutions of performance of Word-Tour cyclists during an official competitive ITT performed on the same course during two consecutive years.  Methods After a maximal exhaustive aerobic test, a group of physically active individuals and trained cyclists (N= 12; MAP 352 ± 49 W) in randomized order performed one FTP test over 20 minutes (FTP20) and one CP test, comprising of maximal time trial efforts (TT) of 12 min, 7 min and 3 min, interspersed by 30 min rest (9). Tests were performed on a Cyclus2 ergometer (RBM Elektronik GmbH, Leipzig, Germany). During TTs and FTP test, participants utilised a self-pacing strategy were gearing was adjusted throughout efforts using the virtual gear changer mounted to the handlebars. CP was determined using the power-inverse time model (P = Wi‚¢(1/t) + CP) and FTP60 was calculated as 95% of the FTP20 mean PO. Differences of statistical significance between CP and FTP values were tested using a paired samples t-tests. Relationships were assessed using Pearson product moment correlation coefficients. The agreement between CP and FTP60 values was assessed using Limits of Agreement (LoA). Linear regression was used to calculate the standard error of estimate (SEE) associated with predicting FTP60 values as well as for individual CP values.  Results The mean difference between CP and FTP60 values was 5 ± 11 W, which was non-significant (t(11) = 1.7, p = .108). LoA between values were -38 – 29 W (Fig 1A). The standard error associated with the prediction of FTP60 was 18 W (Cl, 13 - 28W), when expressed as percentage error resulted in 7.9% (Cl, 5.8 – 12.9%). The correlation between CP and FTP60 values was r = 0.93, P ≤ 0.001 (Fig 1B). The mean SEE for CP values was 4 ± 2 W.  Discussion Results demonstrate low LoA between CP and FTP60 values and a high prediction error when using a group of mixed trained athletes. This suggests that CP and FTP60 results cannot be used interchangeably. By using more than one data point, an advantage of CP over FTP60 is a reduction in random error (expressed as SEE). This can be useful for coaches as it minimizes the biological re-test variability caused by the athlete. CP testing also allows the determination of W', i.e. the maximum amount of work that can be expended above the intensity of CP. It therefore offers more information about the performance capabilities of an athlete. With some agreement present for the trained cyclists, future studies should focus on this population.  Conclusion For a same ITT, mean PO of a professional cyclist remain extremely stable over years. Accordingly, he will be more able to improve his performance thanks to a better effort regulation than by increasing his mean PO. EVA method appears to be an innovative tool to evaluate cyclists’ ability to optimally regulate exercise intensity during ITT.

The variability of the trunk forward bending in standing activities during work vs. leisure time

High level of occupational physical activity (PA), contrary to leisure time activities, is generally associated with detrimental health outcomes. We hypothesized that this contrast may be associated with a different pattern of exposure variability in PA, e.g., forward bending of the trunk. The study was conducted on 657 blue-collar workers. Two accelerometers were used to identify the body posture and forward bending of the trunk during work and leisure time. The pattern of forward bending was analyzed using exposure variation analysis (EVA). The recordings comprised of 2.6 ± 0.97 working days in average, with 19.9 ± 8.1 h work and 22.9 ± 8.9 h leisure. The standard deviation and entropy of the EVA profile indicated 11% and 6% (for about 80% of subjects) less variable pattern during work compared with the leisure time, respectively. These new findings contribute to the understanding the paradoxical outcomes of PA during work and leisure.

Differences between work and leisure in temporal patterns of objectively measured physical activity among blue-collar workers.

BackgroundLeisure time physical activity (LTPA) is generally associated with favorable cardiovascular health outcomes, while occupational physical activity (OPA) shows less clear, or even opposite, cardiovascular effects. This apparent paradox is not sufficiently understood, but differences in temporal patterns of OPA and LTPA have been suggested as one explanation. Our aim was to investigate the extent to which work and leisure (non-occupational time) differ in temporal activity patterns among blue-collar workers, and to assess the modification of these patterns by age and gender.MethodsThis study was conducted on a cross-sectional sample of male (n = 108) and female (n = 83) blue-collar workers, aged between 21 and 65 years. Physical activity and sedentary behavior were assessed using accelerometers (Actigraph GT3X+) worn on the thigh and trunk for four consecutive days. Temporal patterns of OPA and LTPA were retrieved using Exposure Variation Analysis (EVA), and expressed in terms of percentage of work and leisure time spent in uninterrupted periods of different durations (<1 min, 1–5 min, 5–10 min, 10–30 min, 30–60 min and > 60 min) of sitting, standing, and walking. Repeated measures ANOVA and linear regression analyses were used to test a) possible differences between OPA and LTPA in selected EVA derivatives, and b) the modification of these differences by age and gender.ResultsOPA showed a larger percentage time walking in brief (<5 min) periods [mean (SD): 33.4 % (12.2)], and less time in prolonged (>30 min) sitting [7.0 % (9.3)] than LTPA [walking 15.4 % (5.0); sitting 31.9 % (15.3)], even after adjustment for the difference between work and leisure in total time spent in each activity type. These marked differences in the temporal pattern of OPA and LTPA were modified by gender, but not age.ConclusionWe found that the temporal patterns of OPA and LTPA among blue-collar workers were markedly different even after adjustment for total physical activity time, and that this difference was modified by gender. We recommend using EVA derivatives in future studies striving to disentangle the apparent paradoxical cardiovascular effect of physical activity at work and during leisure.

A new way of assessing arm function in activity using kinematic Exposure Variation Analysis and portable inertial sensors – A validity study

Portable motion systems based on inertial motion sensors are promising methods, with the advantage compared to optoelectronic cameras of not being confined to a laboratory setting. A challenge is to develop relevant outcome measures for clinical use. The aim of this study was to characterize elbow and shoulder motion during functional tasks, using portable motion sensors and a modified Exposure Variation Analysis (EVA) and evaluate system accuracy with optoelectronic cameras.Ten healthy volunteers and one participant with sequel after stroke performed standardised functional arm tasks. Motion was registered simultaneously with a custom developed motion sensor system, including gyroscopes and accelerometers, and an optoelectronic camera system. The EVA was applied on elbow and shoulder joints, and angular and angular velocity EVA plots was calculated.The EVA showed characteristic patterns for each arm task in the healthy controls and a distinct difference between the affected and unaffected arm in the participant with sequel after stroke. The accuracy of the portable system was high with a systematic error ranging between −1.2° and 2.0°. The error was direction specific due to a drift component along the gravity vector.Portable motion sensor systems have high potential as clinical tools for evaluation of arm function. EVA effectively illustrates joint angle and joint angle velocity patterns that may capture deficiencies in arm function and movement quality. Next step will be to manage system drift by including magnetometers, to further develop clinically relevant outcome variables and apply this for relevant patient groups.

Physical Demands of Sprinting in Professional Road Cycling.

The aim of this study was to quantify the demands of road competitions ending with sprints in male professional cycling. 17 races finished with top-5 results from 6 male road professional cyclists (age, 27.0±3.8 years; height, 1.76±0.03 m; weight, 71.7±1.1 kg) were analysed. SRM power meters were used to monitor power output, cadence and speed. Data were averaged over the entire race, different durations prior to the sprint (60, 10, 5 and 1 min) and during the actual sprint. Variations in power during the final 10 min of the race were quantified using exposure variation analysis. This observational study was conducted in the field to maximize the ecological validity of the results. Power, cadence and speed were statistically different between various phases of the race (p<0.001), increasing from 316±43 W, 95±4 rpm and 50.5±3.3 km·h(-1) in the last 10 min, to 487±58 W, 102±6 rpm and 55.4±4.7 km·h(-1) in the last min prior to the sprint. Peak power during the sprint was 17.4±1.7 W·kg(-1). Exposure variation analysis revealed a significantly greater number of short-duration high-intensity efforts in the final 5 min of the race, compared with the penultimate 5 min (p=0.010). These findings quantify the power output requirements associated with high-level sprinting in men's professional road cycling and highlight the need for both aerobic and anaerobic fitness.

It's A-bout Time: Detailed Patterns of Physical Activity in Obese Adolescents Participating in a Lifestyle Intervention.

The detailed patterns of physical activity and sedentary behaviors of overweight and obese adolescents are unknown, but may be important for health outcomes and targeted intervention design. Participants completed Curtin University's Activity, Food and Attitudes Program (CAFAP), an 8-week intervention with 12 months of maintenance intervention. Physical activity and sedentary time were assessed at 6 time periods with accelerometers and were analyzed by 1) time and type of day, 2) intensity bout patterns using exposure variation analysis, and 3) individual case analysis. Participants (n = 56) spent a lower percentage of time at baseline in light activity during school days compared with weekend days (24.4% vs 29.0%, P = .004). The majority of time was in long uninterrupted sedentary bouts of greater than 30 minutes (26.7% of total time, 36.8% of sedentary time at baseline). Moderate activity was accumulated in short bouts of less than 5 minutes (3.1% of total time, 76.0% moderate time). Changes varied by individuals. Exposure variation analysis revealed specific changes in activity patterns in overweight and obese adolescents who participated in a lifestyle intervention. A better understanding of these patterns can help to design interventions that meaningfully affect specific behaviors, with unique health consequences.

Pacing strategies during the swim, cycle and run disciplines of sprint, Olympic and half-Ironman triathlons.

This study investigated the influence of distance on self-selected pacing during the swim, cycle and run disciplines of sprint, Olympic and half-Ironman (HIM) distance triathlon races. Eight trained male triathletes performed the three individual races in <2 months. Participants' bikes were fitted with Schoberer Rad Meßtechnik to monitor speed, power output and heart rate during the cycle discipline. Global positioning system was worn to determine speed and heart rate during the swim and run disciplines. An even swim pacing strategy was adopted across all distances. A more stochastic pacing was observed during the HIM cycle [standard deviation of exposure variation analysis (EVASD) = 3.21 ± 0.61] when compared with the sprint cycle discipline (EVASD = 3.84 ± 0.44, p = 0.018). Only 20.9 ± 4.1 % of the cycling time was spent more than 10 % above the mean power output in the HIM, compared with 43.8 ± 2.9 % (p = 0.002) and 37.7 ± 11.1 % (p = 0.039) during the sprint and Olympic distance triathlons, respectively. Conversely, 13.6 ± 5.1 % of the cycling time was spent 5-10 % below the mean power output during the HIM, compared with 5.9 ± 1.2 % (p = 0.034) and 8.0 ± 5.1 % (p = 0.045) during the sprint and Olympic distance triathlons, respectively. A negative pacing strategy was adopted during the sprint distance run, compared with positive pacing strategy during the Olympic and HIM. Results of this study suggest that pacing strategies during triathlon are highly influenced by distance and discipline, and highlight the importance of developing pacing strategies based on distance, strengths and individual fitness.

Changing the sedentary time and physical activity trajectories of obese adolescents: Results from the CAFAP controlled clinical trial

Introduction: Adolescents are typically on trajectories of increasing sedentary timeanddecreasingmoderate/vigorousphysical activity. Overweight and obese adolescents may have poorer activity profiles than normal weight adolescents and therefore be at increased risk of activity-related physical and mental health problems. As activity behaviours tend to track from adolescence to adulthood, altering adolescent activity trajectories is likely to have long-term health consequences. This study aimed to evaluate the immediate and 12 month post-intervention effectiveness of an intervention focused on changing the sedentary and physical activity behaviours of obese adolescents. Methods: Sixty nine adolescents aged 14.1 (SD 1.6) years participated in awithin-subjects staggered-entrywaitlist controlled trial ofCurtinUniversity’sActivity, FoodandAttitudesProgram(CAFAP). CAFAP involved an 8 week intensive multi-disciplinary familybased community intervention with tapered text message and phone support for 12 months. Sedentary time and light, moderate and vigorous activity were measured using Actical accelerometers worn on the hip for a week. Fifty six participants provided adequate accelerometer data in at least two assessments and were included in linear mixed model analysis. Activity profile patterns were assessed with Exposure Variation Analysis. Results: On entry to the study adolescents were sedentary for 70.3% of their awake wear day, with 25.4% spent in light activity, 4.2% in moderate activity and just 0.2% spent in vigorous activity. 28.1% of their wear day was spent in bouts of sedentary time of at least 30min duration, with 9.8% spent in sedentary bouts of 60min ormore. During the control period adolescents showed trajectories of increasing daily sedentary time (mean 532.3 [SE 3.3] to 548.2 [3.7], p=0.003) and decreasing daily light activity (199.7 [2.7] to 186.4 [3.5], p=0.007) with decreasing trends for moderate (31.1 [1.3] to 29.4 [1.1], p=0.147) and vigorous (1.5 [0.2] to 1.3 [0.2], p=0.470) activity. During the intervention period these trajectories were reversedwithmonthly rates of change showing a decrease for sedentary time (−5.1 [95% CI −11.0, 0.8]) and an increase for moderate physical activity (1.8 [−0.04, 3.6]). Sedentary time and light, moderate and vigorous activity levels remained stable over the 12month maintenance period. There were no significant reductions in prolonged bouts of sedentary time following the intervention. Discussion: The CAFAP intervention was effective in changing the sedentary time and physical activity trajectories of obese adolescents suggesting behavior focused interventions have the potential to create long-term health changes. However trajectories of prolonged sedentary time were not changed in the intervention and thus further development of interventions targeting the pattern of sedentary behaviour is required.

Development of three-dimensional shoulder kinematic and electromyographic exposure variation analysis methodology in violin musicians

A total of 11 male and 19 female violinists performed 30-second random-ordered slow and fast musical repertoire while right shoulder three-dimensional kinematic, and upper trapezius and serratus anterior surface electromyography (EMG) data were summarised using exposure variation analysis (EVA), a bivariate distribution of work time spent at categories of signal amplitude, and duration spent at a fixed category of amplitude. Sixty-two per cent of intraclass correlation coefficients [1,1] for all kinematic and EMG variables exceeded 0.75, and 40% of standard error of the measurement results were below 5%, confirming EVA reliability. When fast repertoire was played, increases in odds ratios in short duration cells were seen in 23 of 24 possible instances, and decreases in longer duration cells were seen in 17 instances in all EVA arrays using multinomial logistic regression with random effects, confirming a shift towards shorter duration. A reliable technique to assess right shoulder kinematic and EMG exposure in violinists was identified.