Face validity of the single work ability item: comparison with objectively measured heart rate reserve over several days.
OBJECTIVE
The purpose of this study was to investigate the face validity of the self-reported single item work ability with objectively measured heart rate reserve (%HRR) among blue-collar workers.


METHODS
We utilized data from 127 blue-collar workers (Female = 53; Male = 74) aged 18-65 years from the cross-sectional "New method for Objective Measurements of physical Activity in Daily living (NOMAD)" study. The workers reported their single item work ability and completed an aerobic capacity cycling test and objective measurements of heart rate reserve monitored with Actiheart for 3-4 days with a total of 5,810 h, including 2,640 working hours.


RESULTS
A significant moderate correlation between work ability and %HRR was observed among males (R = -0.33, P = 0.005), but not among females (R = 0.11, P = 0.431). In a gender-stratified multi-adjusted logistic regression analysis, males with high %HRR were more likely to report a reduced work ability compared to males with low %HRR [OR = 4.75, 95% confidence interval (95% CI) = 1.31 to 17.25]. However, this association was not found among females (OR = 0.26, 95% CI 0.03 to 2.16), and a significant interaction between work ability, %HRR and gender was observed (P = 0.03).


CONCLUSIONS
The observed association between work ability and objectively measured %HRR over several days among male blue-collar workers supports the face validity of the single work ability item. It is a useful and valid measure of the relation between physical work demands and resources among male blue-collar workers. The contrasting association among females needs to be further investigated.
National Research Centre for the Working Environment, 2100, Copenhagen, Denmark. ngu@nrcwe.dk.
Nidhi
N
Gupta
National Research Centre for the Working Environment, 2100, Copenhagen, Denmark. ksogaard@health.sdu.dk.
Bjørn Søvsø
BS
Jensen
Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230, Odense M, Denmark. ksogaard@health.sdu.dk.
Karen
K
Søgaard
National Research Centre for the Working Environment, 2100, Copenhagen, Denmark. igc@nrcwe.dk.
Isabella Gomes
IG
Carneiro
National Research Centre for the Working Environment, 2100, Copenhagen, Denmark. carolinestordal@gmail.com.
Caroline Stordal
CS
Christiansen
Federal Institute for Occupational Safety and Health (BAuA) Nöldnerstr, 40-42, D-10317, Berlin, Germany. hanisch.christiana@baua.bund.de.
Christiana
C
Hanisch
National Research Centre for the Working Environment, 2100, Copenhagen, Denmark. aho@nrcwe.dk.
Andreas
A
Holtermann
D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D006339:Heart Rate; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D057566:Self Report; D012737:Sex Factors; D012959:Socioeconomic Factors; D014938:Work Capacity Evaluation; D016526:Workload; D055815:Young Adult