Short- and long-term reliability of heart rate variability indices during repetitive low-force work

© 2014, Springer-Verlag Berlin Heidelberg. Purpose: Heart rate variability (HRV) is often monitored in occupational studies as a measure of cardiac autonomic activation, but the reliability of commonly used HRV indices is poorly understood. In the present study, we determined the variability between and within subjects of common HRV indices during a repetitive low-force occupational task, i.e., pipetting, and interpreted the results in terms of necessary sample sizes in studies comparing HRV between conditions or groups. Methods: Fourteen healthy female subjects performed a standardized pipetting task in the laboratory on three separate days within a short-time span ( < 2 weeks), and on one additional occasion 6 months later. A number of standard HRV indices were calculated in both time and frequency domains. For each HRV index, variance components were estimated between subjects, within subjects between occasions far apart in time, and within subjects between days within a 2-week period. Results: We found that the time interval between repeated measurements did not influence the extent of HRV variability, and that the reliability of the most HRV indices was sufficient for even small study samples (30 subjects or less) to be able to detect, with satisfying power ( > 0.80), a significant 10 to 20 % difference in HRV between groups, and between conditions within individuals. Conclusions: We conclude that HRV can be used as a reliable and feasible marker of autonomic activity in occupational studies of repetitive low-force work

Systematic review of quantitative imaging biomarkers for neck and shoulder musculoskeletal disorders

© 2017 The Author(s). Background: This study systematically summarizes quantitative imaging biomarker research in non-traumatic neck and shoulder musculoskeletal disorders (MSDs). There were two research questions: 1) Are there quantitative imaging biomarkers associated with the presence of neck and shoulder MSDs?, 2) Are there quantitative imaging biomarkers associated with the severity of neck and shoulder MSDs? Methods: PubMed and SCOPUS were used for the literature search. One hundred and twenty-five studies met primary inclusion criteria. Data were extracted from 49 sufficient quality studies. Results: Most of the 125 studies were cross-sectional and utilized convenience samples of patients as both cases and controls. Only half controlled for potential confounders via exclusion or in the analysis. Approximately one-third reported response rates. In sufficient quality articles, 82% demonstrated at least one statistically significant association between the MSD(s) and biomarker(s) studied. The literature synthesis suggested that neck muscle size may be decreased in neck pain, and trapezius myalgia and neck/shoulder pain may be associated with reduced vascularity in the trapezius and reduced trapezius oxygen saturation at rest and in response to upper extremity tasks. Reduced vascularity in the supraspinatus tendon may also be a feature in rotator cuff tears. Five of eight studies showed an association between a quantitative imaging marker and MSD severity. Conclusions: Although research on quantitative imaging biomarkers is still in a nascent stage, some MSD biomarkers were identified. There are limitations in the articles examined, including possible selection bias and inattention to potentially confounding factors. Recommendations for future studies are provided