A 2021 systematic review of 14 trials (27,846 participants total) found a strong link between heavy backpack use and pain or musculoskeletal issues in teenagers, especially girls.
Led by Dr. Nazila NeJhaddadgar from the Department of Health Promotion and Education at Ardabil University in Iran, the researchers wrote that some of the common issues reported were pain in the back, neck, and shoulders as well as some spinal deviations, such as kyphosis and lordosis.
Several studies described muscle strain and altered activation patterns, showing that abdominal and trunk muscles worked harder under heavier loads. Others observed shoulder tilt or asymmetry when bags were carried unevenly, and changes in balance, head and neck angles, or gait as students adjusted to carrying the weight.
They added that previous studies indicated that backpacks should not exceed 10-15% of a student’s body weight.
While most of the studies pointed to the risks, some research found weak associations between pain intensity, body weight and backpack-to-body-weight ratio. NeJaddadgar and her colleagues also pointed out the studies often did not track how pain intensity changes with the duration of backpack use, and the study duration is one to two weeks long. They stressed the need for better research that follows students over time and directly measures pain and muscle strain.
Study design, snapshot in time
NeJaddadgar and her colleagues used the Crombie Checklist to appraise the studies’ risk of bias and the value of the findings in health care, and they used the Lloyd- Smith hierarchy of evidence to evaluate the strength of the evidence. Most of the studies fall into the category of “one well-designed, non-randomised controlled study,” which means the evidence is considered moderate in strength.
For example, nine of the 14 studies are cross-sectional, which shows associations, not causal relationships, because they only show a snapshot of the data at one point in time. Two other studies—Siambanes et al. and Haselgrove et al.—are prospective cohorts in design that tracked backpack load and carriage over time.
Also, the sample sizes in the review vary from very small (13 or 48 participants) to huge (20,359). Larger studies tend to carry more statistical weight, and small sample studies tend to be less reliable of their certainty.
The studies were from various countries, including the U.S. (California), Australia, Kuwait, Saudi Arabia, Japan, Uganda, India and Malaysia, which makes the findings more generalizable. However, cultural and school system differences may affect results.
Compared to other studies
While heavy backpacks can be a risk factor for developing chronic back pain among teens, a 2018 systematic review of 69 trials (72,600+ participants) failed to find a strong relationship between heavy backs and back among teens and children.
Most of the studies were a mix of cross-sectional studies and case-controls. 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.
Details of the study are covered in a separate story.
Some of these studies had high to moderate risks of bias due to high attrition rate, mixed testing methods, confounding factors, and poor prognosis.
While carrying a heavy backpack for a long time is a risk factor to getting back pain, pain itself is a multifactorial experience, encompassing biological, psychological, social, and environmental factors. Heavy backpacks are just one piece of the pain puzzle.
Nick Ng, BA
Nick Ng is the editor of Massage & Fitness Jounal 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.
