Threre is no convincing evidence that heavy backpacks is a cause of back pain in children. However, stress and psychosocial factors are better predictors of who has low back pain. (Photo via PxHere, public domain)
A 2018 systematic review on children and teens with back pain found “no convincing evidence that aspects of schoolbag use increase the risk of back pain in children and adolescents.” Published in the British Journal of Sports Medicine, the study pooled 69 trials with a total of more than 72,600 participants.
Led by Dr. Tiê Parma Yamato from The University of Sydney, the researchers found that none of the studies reported how long the students were carrying the bag, how many times they sought back pain care, or how many times they were absent from school. Some of these studies had high to moderate risks of bias due to high due to high attrition rate, mixed testing methods, confounding factors, and poor prognosis.
Most of the studies, which were a mix of cross-sectional studies and case-controls, “did not find an association between schoolbag characteristics and [low back pain],” despite having mixed sample sizes, different measurements in schoolbag weight, and definitions of back pain. Even so, Yamato and her colleagues suggested that the review should be “interpreted with caution.”
“There are few longitudinal cohort studies in children and adolescents in the literature, and in most of these cases identifying risk factors for back pain was not the primary aim,” they reported. “Consequently, the choice of exposure variables, measurement instruments and timing of data collection are not optimal to reveal causal relationships. These problems may explain why systematic reviews in this field do not have strong conclusions.”
Heavy backpacks may be a contributing factor to back pain for some youngsters, but it’s not likely a major one. More data revealed other factors that influence why some kids have back pain.
Psychosocial factors, such as stress and depression, are higher predictors of low back pain in children and teens than heavy backpacks. (Photo by Dmitrii Shironosov)
Back pain’s bigger picture
Previous reviews also found similar results. One systematic review from 2007 examined 10 studies with more than 17,000 children and teens on upper body pain (neck, upper back, shoulders).
The highest predictors of who is more likely to get upper body pain are:
- Static posture
- Depression
- Stress
- Psychosomatic symptoms
- Gender
- Age
The researchers found that girls had higher reports of pain than boys, especially those with depression.
In one study of that systematic review, somehow almost all the girls who participated reported weekly of having pain in association with sitting in a static posture while hardly any boys reported any pain.
Other studies included found that those who hunched while working or playing on a laptop for a long time have higher reports of shoulder pain as well as those who sit at school or at home for one to more than four hours.
Although having a kyphotic posture may lead to such pain, it’s likely less about the specific posture and more about being in one position for too long.
Because of the different methods of measurements used in the selected studies, the researchers reported that it’s hard to determine how much influence any one posture has upon pain development.
“The results of the selected studies should therefore be interpreted with caution,” they wrote, “especially the pain measurements because none of the studies defined the frequency, duration, or intensity of pain in the same manner.”
They also cited that self-reported pain measurements can be influenced by psychosocial and cultural factors that could vary among different populations of youths. Also, the recall period in the studies vary from a week to 12 months, which tends to reduce accuracy of reporting the longer the time and the increase of age.
Another review published in Journal in Physiotherapy in 2010 examined five trials on the first risk factors that are likely to contribute to chronic low back pain among children.
One of their findings is that spinal asymmetry increased the risk of back pain a year later among girls compared to those with less or no spinal asymmetry.
But when the same group was re-examined eight years later, there was no difference between the groups. Further studies also found that lumbar mobility was not associated with back pain risk.
“Many of the significant associations with future low back pain may have been chance findings,” Hill and Keating reported. “Although 13 risk factors were identified, none was confirmed as significant in an independent study. Four failed to be validated as predictive in a subsequent study, which amplifies the need for validation studies.”
A 2020 study for 123 elementary schoolchildren in Spain found “no significant correlation between the weight or type of backpack and the pressure pain threshold collected from shoulders muscles.
“Participants who carried backpacks heavier than 10% of their body weight did not have more musculoskeletal pain or a lower pressure pain threshold than the others, although they did report greater fatigue,” the researchers reported.
Also, 89% of backpack injuries did not affect the back, according to a study of 247 U.S. children who were admitted to the emergency room for backpack-related injuries.
“Eliminating heavy backpacks from children, or even reducing the load they carry therefore, may not be a panacea in reducing overall [back pain] rates,” the researchers wrote.
Factors that influence back pain among teens are not that different than children. Heavy backpacks and posture are still not a reliable predictors. (Photo by Haylad)
Past evidence on posture and pain
Much of the research do not find spine curvature and heavy backpacks are major contributors to back pain among teens and adults.
A 2008 Danish systematic review pooled data from 54 studies with more than 20,700 subjects and found “insufficient evidence” between the spinal curves in the sagittal plane and various health problems, such as low back pain, disc herniation, neck and upper back pain, bone mass loss, breathing disorders, fractures, and risk of falls.
Further studies since the 1990s also found various results:
1. Weak association between kyphosis and non-traumatic shoulder pain at the acromion based on 10 studies.
2. No association of low back pain with the size of the lumbar lordosis, pelvic tilt, leg length discrepancy, and the length of abdominal, hamstring, and iliopsoas muscles are not associated with the occurrence of low back pain among 600 young to older adults in Tehran, Iran.
3. A correlation was found between subjects having lower lordotic curve and low back pain vs. those with higher lordotic curve and no pain in a South Korean systematic review of 13 studies where nine of them found such correlation with “statistical significance” while the other four did not.
This only demonstrate correlation, not causation, since they do not know which came first: the pain or the lack of lordotic curve?
4. A systematic review cited six high-quality studies that do not find an association between “awkward occupational postures” and low back pain. If there is any, it would be “weak,” the researchers stated.
While there are some reports that such work postures could cause low back pain, such as prolonged kneeling or squatting, the evidence is conflicting because of the lack of reporting of duration, frequency, and different methods of measurements of posture and back pain.
In fact, one research found that cricket players with abdominal muscle symmetry had higher reportings of back pain than those with higher muscle development on one side of their body, and there is hardly any difference between abdominal muscle development and back pain among a sample of ballet dancers.
Where did the idea of heavy backpacks causes back pain started?
One of the earliest research on backpacks and back pain came from India with six boys between the ages of 9 to 15 that was published in Ergonomics in 1965.
Researchers M.S. Malhotra and J. Sen Gupta from the Defence Institute of Physiology and Allied Sciences gave the students a 6-pound schoolbag to carry, kind of like the one that Paddington Bear carries but with a long strap.
Four of the boys carried the bag and walked with a respiratory in their mouth over a certain distance, and during that four-day experiment, each boy carried the bag in a different way—between the shoulder blades (rucksack), hanging toward the lower back, one strap across the body, and carrying with one hand.
The two other boys carried a Douglas bag that measured oxygen consumption and basal metabolic rate as the other boys walked.
The researchers found that the rucksack position is the most energy efficient way to carry and walk and does not “lead to deformity of the body posture…no impediment in movement.” They also mentioned that the worse position to carry is with one hand.
While this preliminary study has plenty of methodological errors, (the biopsychosocial model of pain had not been developed yet and the gate control theory was still a novel idea), it may have fueled further beliefs among clinicians and the public at the time that back pain is biomechanical in nature.
In 2002, British physiotherapist Jenny Wigram wrote in Education and Health that many students blamed heavy schoolbags for their low back pain, in addition to sitting for long hours in a classroom. Around that time, some clinicians suggested that students should carry between 10-15% of their body weight, but no more than 20%.
Yamato and her colleagues wrote that their research “call into question the various guidelines and statements that endorse specific weight limits for school bags in children and adolescents. It seems that these recommendations are not based on the most reliable evidence on the subject.”
Nick Ng is the editor of Massage & Fitness Magazine and the managing editor for My Neighborhood News Network.
An alumni from San Diego State University with a bachelor’s degree in graphic communications, Nick had completed his massage therapy training at International Professional School of Bodywork in San Diego in 2014. In 2021, he earned an associate’s degree in journalism at Palomar College.
When he gets a chance, he enjoys weightlifting at the gym, salsa dancing, and exploring new areas in the Puget Sound area in Washington state.
