Muscle fatigue from prolonged standing can cause back pain.
Nearly half of all workers worldwide have to stand for more than three quarters of their working day, say researchers who warn prolonged standing can result in fatigue, leg cramps and back ache - problems that not only cause discomfort but also affect work performance and productivity.
In the longer term, this type of sustained muscle fatigue can lead to more serious joint problems and back pain, they note in a report of a study published in Human Factors, the journal of the Human Factors and Ergonomics Society.
First author María Gabriela García, who is working towards her doctorate in the department of health sciences and technology at ETH Zürich in Switzerland, says:
"The work-related musculoskeletal implications that can be caused by prolonged standing are a burden not only for workers but also for companies and society."
Despite this, she notes that the long-term muscle fatigue caused by prolonged standing has not received much attention in research.
Younger and older workers affected
For their study, García and colleagues invited 14 men and 12 women in two age groups to simulate standing work for periods lasting 5 hours at a time. These periods included seated breaks lasting no more than 5 minutes and a 30-minute lunch break.
The researchers measured muscle fatigue with a system that uses electrical stimulation to cause muscle twitching and then measures the muscle twitch force (MTF). They also measured postural stability and asked the volunteers to assess their level of discomfort.
The results showed that even when they had regular breaks, the volunteers experienced significant long-term fatigue following their 5-hour simulated working day.
Symptoms of long-term fatigue lasted for at least 30 minutes following a seated recovery period, the authors note.
Moreover, younger participants (age 18-30) were just as likely to show signs of long-term fatigue as older workers (age 50 and over).
'Fatigue may be present but not perceived'
The researchers also found a discrepancy between the physically measured results and the perceptions of the volunteers, who did not perceive fatigue as lasting more than 30 minutes after the end of the 5-hour standing work day.
García says that "long-term fatigue after prolonged standing work may be present without being perceived," and concludes:
"Current work schedules for standing work may not be adequate for preventing fatigue accumulation, and this long-lasting muscle fatigue may contribute to musculoskeletal disorders and back pain."
According to the Canadian Center for Occupational Health and Safety (CCOHS), working in a standing position on a regular basis can lead not only to fatigue and lower back pain but can also cause other health problems such as sore feet, swollen legs, varicose veins and stiffness in the neck and shoulders.
These are common complaints among workers whose jobs require them to stand for long periods, such as assembly-line workers, sales people and machine operators.
The CCOHS also note that:
"In a well-designed workplace, the worker has the opportunity to choose from among a variety of well-balanced working positions and to change between them frequently."
They add that even in jobs that require workers to remain standing to carry out tasks, seats "should be provided in any case" to allow them to sit occasionally.
In February 2015, Medical News Today reported another study led by the University of Sydney in Australia that found performing manual tasks involving awkward postures can increase the chance of low back pain by as much as eight times. Writing in the journal Arthritis Care & Research, the team also identifies some triggers that can be modified to prevent acute episodes of low back pain.