TY - GEN
T1 - Daily fluctuations in low-back pain, fatigue, and stress among warehouse and construction workers
AU - Bláfoss, Rúni
PY - 2024/2/28
Y1 - 2024/2/28
N2 - Background: Physical and mental factors are important determinants for well-being among workers. Working at warehouses and construction sites involve physically demanding work tasks that increase the risk of developing low-back pain (LBP). LBP is the single most debilitating and costly musculoskeletal disorder in Denmark and globally. Besides increasing pain, physically demanding work may increase perceived symptoms as bodily fatigue and mental stress.Aims: This Doctoral Dissertation investigates associations between daily lifting loads (kg)
with LBP intensity, bodily fatigue, and mental stress (Paper 2) and the effects of consecutive workdays and days off from work on the above-mentioned outcome variables (Paper
3). Furthermore, the Dissertation aims to investigate whether pressure pain threshold
(PPT) is lower at the end compared to the beginning of the working week, and which individual, biomechanical, and functional parameters are associated with the difference in PPT
and mean PPT (Paper 4).Methods: This prospective cohort study invited 383 warehouse and construction workers
to reply a baseline questionnaire on general characteristics, lifestyle, health, and the working environment, of which 278 replied (72.6%). Subsequently, the workers received short
daily questionnaires before and after work for 21 consecutive days (including days off from
work) about LBP intensity, bodily fatigue, and mental stress (all questions used 0-10 a
numeric rating scale), as well as number of hours at work that day. During these 21 days,
warehouse supervisors provided company records with information on daily lifting loads
(kg) per day for each warehouse worker. Furthermore, a sub-sample of the workers were
invited to measure PPT in m. erector spinae with m. tibialis anterior as the remote painfree reference muscle, maximal back extensor strength (MVC), and back extensor endurance. Linear mixed models tested associations in Paper 2 and Paper 3 while controlling
for relevant confounders. Paired Student’s t-test tested the within-subject differences in
PPT between the beginning and end of the working week, while multiple linear regression
investigated whether MVC and back extensor endurance influenced the difference in PPT
and mean PPT while controlling for various confounders (Paper 4).Results: Compared to lifting 0-499 kg, lifting 500-1999 kg was associated with 0.59 points
(95% CI 0.10 to 1.08) higher LBP intensity after work, while lifting ≥5000 kg was associated
with an elevated LBP intensity of 1.26 points (95% CI 0.48 to 2.03). Furthermore, lifting
≥5000 kg resulted in 0.72 points (95% CI 0.08 to 1.36) higher mental stress levels after
work. While mental stress was lower the following morning, LBP intensity remained elevated with no differences between lifting intervals (Paper 2). Consecutive workdays gradually increased LBP intensity after work, with one, two, and three workdays increasing LBP
intensity by 1.34 points (95% CI 1.11 to 1.57), 1.33 points (95% CI 1.07 to 1.58), and 1.76
points (95% CI 1.48 to 2.03), respectively. LBP intensity remained elevated the following
mornings with no differences between mornings. After one workday, bodily fatigue increased by 2.06 points (95% CI 1.80 to 2.32) while mental stress increased 0.97 points
(95% CI 0.77 to 1.17), and both remained at the same level for three consecutive workdays. Both bodily fatigue and mental stress remained elevated the following morning after
one, two, and three consecutive workdays, with no differences between mornings. After
one day off from work, bodily fatigue decreased -1.82 points (95% CI -2.03 to -1.61) while
mental stress decreased -0.88 points (95% CI -1.05 to -0.71). Neither bodily fatigue nor mental stress decreased further following two consecutive days off from work. LBP intensity decreased -1.09 points (95% CI -1.27 to -0.91) after one day off while two consecutive
days off resulted in a further decrease of -1.45 points (95% CI -1.67 to -1.24) (Paper 3).
No differences existed between PPT in the beginning compared to the end of the working
week. While back extensor endurance represented was associated with the difference in
PPT (Estimate 0.76 kPa (95% CI 0.07-1.45), p=0.037), particularly MVC was a strong
predictor for mean PPT (Estimate 1.14 kPa (95% CI 0.79-1.49, p=0.004) (Paper 4).
Conclusions: Daily lifting loads and consecutive workdays and days off were differently
associated with LBP, bodily fatigue, and mental stress. Higher lifting loads were particularly associated with higher LBP intensity after work in a progressive manner while remaining elevated the following morning. No linear exposure-response association was observed. LBP intensity progressively increased after consecutive workdays while bodily fatigue and mental stress increased after one workday and remained at the same level.
While bodily fatigue and mental stress were reduced after one day off from work, workers
needed (at least) two days off to recover from the accumulated LBP intensity from the
preceding consecutive workdays. Workload did not affect PPT, and back extensor endurance represented a predictor variable for the difference in PPT, while MVC was strongly
associated with mean PPT. Workplaces should consider total daily lifting loads when organizing the working week, while also ensuring proper rest within and during the days to
reduce LBP, bodily fatigue, and mental stress. Future research could investigate the feasibility in developing the logistic systems to distribute the lifting loads more equally between the workers, while also ensuring sufficient recovery for the workers. . Lastly, ensuring high physical capacity, particularly back extensor strength, seems vital to reduce pain
sensitivity.
AB - Background: Physical and mental factors are important determinants for well-being among workers. Working at warehouses and construction sites involve physically demanding work tasks that increase the risk of developing low-back pain (LBP). LBP is the single most debilitating and costly musculoskeletal disorder in Denmark and globally. Besides increasing pain, physically demanding work may increase perceived symptoms as bodily fatigue and mental stress.Aims: This Doctoral Dissertation investigates associations between daily lifting loads (kg)
with LBP intensity, bodily fatigue, and mental stress (Paper 2) and the effects of consecutive workdays and days off from work on the above-mentioned outcome variables (Paper
3). Furthermore, the Dissertation aims to investigate whether pressure pain threshold
(PPT) is lower at the end compared to the beginning of the working week, and which individual, biomechanical, and functional parameters are associated with the difference in PPT
and mean PPT (Paper 4).Methods: This prospective cohort study invited 383 warehouse and construction workers
to reply a baseline questionnaire on general characteristics, lifestyle, health, and the working environment, of which 278 replied (72.6%). Subsequently, the workers received short
daily questionnaires before and after work for 21 consecutive days (including days off from
work) about LBP intensity, bodily fatigue, and mental stress (all questions used 0-10 a
numeric rating scale), as well as number of hours at work that day. During these 21 days,
warehouse supervisors provided company records with information on daily lifting loads
(kg) per day for each warehouse worker. Furthermore, a sub-sample of the workers were
invited to measure PPT in m. erector spinae with m. tibialis anterior as the remote painfree reference muscle, maximal back extensor strength (MVC), and back extensor endurance. Linear mixed models tested associations in Paper 2 and Paper 3 while controlling
for relevant confounders. Paired Student’s t-test tested the within-subject differences in
PPT between the beginning and end of the working week, while multiple linear regression
investigated whether MVC and back extensor endurance influenced the difference in PPT
and mean PPT while controlling for various confounders (Paper 4).Results: Compared to lifting 0-499 kg, lifting 500-1999 kg was associated with 0.59 points
(95% CI 0.10 to 1.08) higher LBP intensity after work, while lifting ≥5000 kg was associated
with an elevated LBP intensity of 1.26 points (95% CI 0.48 to 2.03). Furthermore, lifting
≥5000 kg resulted in 0.72 points (95% CI 0.08 to 1.36) higher mental stress levels after
work. While mental stress was lower the following morning, LBP intensity remained elevated with no differences between lifting intervals (Paper 2). Consecutive workdays gradually increased LBP intensity after work, with one, two, and three workdays increasing LBP
intensity by 1.34 points (95% CI 1.11 to 1.57), 1.33 points (95% CI 1.07 to 1.58), and 1.76
points (95% CI 1.48 to 2.03), respectively. LBP intensity remained elevated the following
mornings with no differences between mornings. After one workday, bodily fatigue increased by 2.06 points (95% CI 1.80 to 2.32) while mental stress increased 0.97 points
(95% CI 0.77 to 1.17), and both remained at the same level for three consecutive workdays. Both bodily fatigue and mental stress remained elevated the following morning after
one, two, and three consecutive workdays, with no differences between mornings. After
one day off from work, bodily fatigue decreased -1.82 points (95% CI -2.03 to -1.61) while
mental stress decreased -0.88 points (95% CI -1.05 to -0.71). Neither bodily fatigue nor mental stress decreased further following two consecutive days off from work. LBP intensity decreased -1.09 points (95% CI -1.27 to -0.91) after one day off while two consecutive
days off resulted in a further decrease of -1.45 points (95% CI -1.67 to -1.24) (Paper 3).
No differences existed between PPT in the beginning compared to the end of the working
week. While back extensor endurance represented was associated with the difference in
PPT (Estimate 0.76 kPa (95% CI 0.07-1.45), p=0.037), particularly MVC was a strong
predictor for mean PPT (Estimate 1.14 kPa (95% CI 0.79-1.49, p=0.004) (Paper 4).
Conclusions: Daily lifting loads and consecutive workdays and days off were differently
associated with LBP, bodily fatigue, and mental stress. Higher lifting loads were particularly associated with higher LBP intensity after work in a progressive manner while remaining elevated the following morning. No linear exposure-response association was observed. LBP intensity progressively increased after consecutive workdays while bodily fatigue and mental stress increased after one workday and remained at the same level.
While bodily fatigue and mental stress were reduced after one day off from work, workers
needed (at least) two days off to recover from the accumulated LBP intensity from the
preceding consecutive workdays. Workload did not affect PPT, and back extensor endurance represented a predictor variable for the difference in PPT, while MVC was strongly
associated with mean PPT. Workplaces should consider total daily lifting loads when organizing the working week, while also ensuring proper rest within and during the days to
reduce LBP, bodily fatigue, and mental stress. Future research could investigate the feasibility in developing the logistic systems to distribute the lifting loads more equally between the workers, while also ensuring sufficient recovery for the workers. . Lastly, ensuring high physical capacity, particularly back extensor strength, seems vital to reduce pain
sensitivity.
KW - low-back pain
KW - Pain
KW - Working environment
KW - Fatigue
KW - Stress
KW - Warehouse workers
KW - Construction workers
KW - Lifting load
KW - Workdays
KW - Restitution
U2 - 10.21996/9s17-kf51
DO - 10.21996/9s17-kf51
M3 - Ph.D. thesis
PB - Syddansk Universitet. Det Sundhedsvidenskabelige Fakultet
ER -