PurposeEpidemiological research has identified women to be more susceptible to developing neck–shoulder musculoskeletal disorders when performing low-force, repetitive work tasks. Whether this is attributable to gender differences in fatigability and motor control is currently unclear. This study investigated the extent to which women differ from men in fatigability and motor control while performing a short-cycle repetitive task.Methods113 healthy young adults (58 women, 55 men) performed a standardized repetitive pointing task. The task was terminated when the subject’s perceived exertion reached 8 on the Borg scale. The time to task termination, and changes in means and cycle-to-cycle variabilities of surface electromyography signals from start to end of the task, were compared between women and men, for the upper trapezius, anterior deltoid, biceps and triceps muscles.ResultsWomen and men terminated the task after 6.5 (SD 3.75) and 7 (SD 4) min on average (p > 0.05). All four muscles showed an increase of 25–35 % in average muscle activity with fatigue (no significant sex differences). However, men exhibited a higher increase than women in trapezius muscle variability with fatigue (31 vs. 7 %; p < 0.05), and a decrease in biceps muscle variability where women had an increase (−23 vs. 12 %; p < 0.05).ConclusionsOur results suggest that women and men may not differ in the ability to perform repetitive tasks at low-to-moderate force levels. However, differences in motor control strategies employed in task performance may explain gender differences in susceptibility to developing musculoskeletal disorders when performing repetitive work for prolonged periods in occupational life.

2a.

The overall aim of this study was to measure the physiological responses of firefighters from a single fire service during simulated functional firefighting tasks and to establish the relationship between physical fitness parameters and task performance. 46 males and 3 females firefighters were recruited. Firefighters' aerobic capacity levels were estimated using the Modified Canadian Aerobic Fitness Test (mCAFT). Grip strength levels, as a measure of upper body strength levels, were assessed using a calibrated J-Tech dynamometer. The National Institute for Occupational Safety and Health (NIOSH) protocol for the static floor lifting test was used to quantify lower body strength levels. Firefighters then performed two simulated tasks: a hose drag task and a stair climb with a high-rise pack tasks. Pearson's correlation coefficients (r) were calculated between firefighters' physical fitness parameters and task completion times. Two separate multivariable enter regression analyses were carried out to determine the predictive abilities of age, sex, muscle strength, and resting heart rate on task completion times. Our results displayed that near maximal heart rates of ≥88% of heart rate maximum were recorded during the two tasks. Correlation (r) ranged from −0.30 to 0.20. For the hose drag task, cardiorespiratory fitness and right grip strength (kg) demonstrated the highest correlations of −0.30 and −0.25, respectively. In predicting hose drag completion times, age and right grip strength scores were shown to be the statistically significant (p < 0.05) independent variables in our regression model. In predicting stair climb completion times, age and NIOSH scores were shown to be the statistically significant (p < 0.05) independent variables in our regression model. In conclusion, the hose drag and stair climb tasks were identified as physiological demanding tasks. Age, sex, resting heart rate, and upper body/lower body strength levels had similar predictive values on hose drag and stair climb completion times.

Introduction: The objective of this cross-sectional study is to describe the prevalence and severity of self-reported musculoskeletal disorders (MSDs) in firefighters and how these vary by demographics and length of service (LOS). Methods: A cohort of 294 active-duty firefighters completed a body diagram to indicate the location and pain intensity of their MSK complaints. Where painful sites were indicated, they completed the relevant region-specific self-report disability measure – Neck Disability Index (NDI), Roland Morris Disability Questionnaire (RMDQ), Lower Extremity Functional Scale (LEFS), or the Short Form of Disabilities of the Arm, Shoulder and Hand (QuickDASH) – to quantify severity. Prevalence was determined from the body diagrams and severity from the site-specific self-report questionnaires. Differences in MSK severity based on demographics or LOS were determined using ANOVA. Results: The 294 active-duty firefighters had a mean age of 42.6 (SD 9.7) years and mean duration of service of 15.1 (SD 10.1) years. The prevalence of neck, back, upper-limb, and lower-limb complaints was 20%, 33%, 44%, and 45% respectively. Firefighters 42 years or older reported significantly more severe lower-extremity disability (median (IQR) LEFS: 71 (65, 77) vs. 75 (69.5, 78.5), p=0.03) and more severe back disability (median (IQR) RMDQ: 2 (1, 3) vs. 1 (0, 2), p=0.04). Firefighters with 15 years or more of firefighting service reported significantly more severe lower extremity disability (median (IQR) LEFS: 71 (64, 77) vs. 76 (70, 79), p=0.0005). Firefighters reporting >1 MSDs were significantly older than firefighters reporting no MSD ( F(5,285)=3.3, p=0.002). Discussion: The rate of MSDs is high in firefighters, and their severity is elevated with greater age and LOS, suggesting cumulative exposures/injuries and highlighting the need for ongoing assessment of the musculoskeletal system and interventions to reduce injury throughout firefighters' careers.

Little was known about the effectiveness of organizational or psychosocial work interventions to prevent work-related musculoskeletal disorders (MSD). We found moderate evidence of the effectiveness of supplementary rest breaks. We also identify key elements of ergonomic interventions lacking in the interventions reviewed that, if integrated into future studies and shown to be effective, may lead to advances in MSD prevention.

BackgroundTechnological development and improvements in Wearable Physiological Monitoring devices, have facilitated the wireless and continuous field-based monitoring/capturing of physiologic measures in healthy, clinical or athletic populations. These devices have many applications for prevention and rehabilitation of musculoskeletal disorders, assuming reliable and valid data is collected. The purpose of this study was to appraise the quality and synthesize findings from published studies on psychometric properties of heart rate measurements taken with the Zephyr Bioharness device.MethodsWe searched the Embase, Medline, PsycInfo, PuMed and Google Scholar databases to identify articles. Articles were appraised for quality using a structured clinical measurement specific appraisal tool. Two raters evaluated the quality and conducted data extraction. We extracted data on the reliability (intra-class correlation coefficients and standard error of measurement) and validity measures (Pearson/Spearman’s correlation coefficients) along with mean differences. Agreement parameters were summarised by the average biases and 95% limits of agreement.ResultsA total of ten studies were included: quality ratings ranged from 54 to 92%. The intra-class correlation coefficients reported ranged from 0.85–0.98. The construct validity coefficients compared against gold standard calibrations or other commercially used devices, ranged from 0.74–0.99 and 0.67–0.98 respectively. Zephyr Bioharness agreement error ranged from − 4.81 (under-estimation) to 3.00 (over-estimation) beats per minute, with varying 95% limits of agreement, when compared with gold standard measures.ConclusionGood to excellent quality evidence from ten studies suggested that the Zephyr Bioharness device can provide reliable and valid measurements of heart rate across multiple contexts, and that it displayed good agreements vs. gold standard comparators – supporting criterion validity.Electronic supplementary materialThe online version of this article (10.1186/s13102-018-0094-4) contains supplementary material, which is available to authorized users.

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Nazari, G, MacDermid, JC, Sinden, KE, Richardson, J, and Tang, A. Reliability of Zephyr Bioharness and Fitbit Charge measures of heart rate and activity at rest, during the modified Canadian Aerobic Fitness Test, and recovery. J Strength Cond Res 33(2): 559–571, 2019—The purpose of this study was to determine the intrasession and intersession reliability of Zephyr Bioharness (ZB) and Fitbit Charge variables in both healthy men and women at rest, during the Modified Canadian Aerobic Fitness Test (mCAFT), and throughout recovery. Stratified convenience and snowball sampling were used to recruit 60 participants (30 women, 48 ± 15 years) and (30 men, 48 ± 15 years) from McMaster University student, staff, and faculty population. At rest, intrasession average heart rate (b·min−1). Intraclass correlation coefficients (ICCs) and Standard Error of Measurement [SEM] for Zephyr ranged from (0.94–0.97) [1.17–1.70] to (0.92–0.97) [1.45–2.10] for Fitbit Charge. During the mCAFT, the Zephyr ICCs and (SEM) ranged from 0.31–0.99 (1.28–8.10) to 0.45–0.99 (1.45–8.71) for the Fitbit Charge. Throughout the recovery, the ICCs and (SEM) ranged from 0.44–0.98 (1.26–10.47) to 0.45–0.98 (1.15–11.90) for Zephyr and Fitbit devices, respectively. At rest, intersession ICCs (SEM) for Zephyr and Fitbit ranged from 0.90–0.94 (1.73–2.37) to 0.88–0.94 (1.83–2.67), respectively. At mCAFT, the Zephyr ICCs (SEM) ranged from 0.91–0.97 (3.12–4.64) to 0.85–0.98 (3.28–4.88) for the Fitbit. Throughout the recovery, the ICCs (SEM) ranged from 0.93–0.97 (2.65–4.66) to 0.76–0.91 (3.17–4.67) for Zephyr and Fitbit devices, respectively. To conclude, both the ZB and Fitbit Charge devices demonstrated excellent reliability measures throughout the 3 phases. The findings from our study add to the existing pool of literature regarding the reliability parameters of wearable devices and suggest that stable and consistent measures of heart rate and physical activity can be obtained using ZB and Fitbit Charge devices among healthy male and female participants at rest, during a standardized submaximal fitness test (mCAFT), and throughout recovery.