Effect of Backpack Weight on Postural Angles in Preadolescent Children.
From: Indian Pediatr. 2009 Oct 14
Backpack use is an appropriate way for carrying loads on the spine, closely and symmetrically, while maintaining stability. Students carry their educational loads mostly in backpacks, without the workplace standards that have been developed for adults. The daily physical stresses associated with carrying backpacks cause significant forward lean of the head and trunk. It is assumed that daily intermittent abnormal postural adaptations could result in pain and disability in school going children.
The peak rate of growth occurs during puberty and the growth of the appendicular skeletal system ceases around 16 years of age for females and 18 years for males. However secondary ossification of vertebrae is not complete until the mid twenties. Therefore, the spine may be susceptible to injury for a greater length of time and therefore, proper backpack use should be emphasized during these years. When the backpack load is positioned posterior to the body, the center of gravity shifts posteriorly, over the base of the support; the area covered by the feet. This shift is accomplished by either leaning forward at the ankle or hip or inclining the head and the rigidity of postural muscles controlling these adjustments increases to support the load. Children have relatively larger heads and also have higher center of mass at about T12, compared to L5-S1 in adults.
Carrying posterior loads by young people has been linked with spinal pain, and the amount of postural change produced by load carriage has been used as a measure of the potential to cause tissue damage. Back pain in children appears to be more common than was previously thought. Studies have indicated that 10%-30% of healthy children experience back pain, especially low back pain, by their teenage years. Hence, investigating postural responses to load carrying will help us to understand the impact of school backpacks on children.
Postural angles used in this study:
Craniovertebral angle:
Formed at the intersection of the horizontal line through the spinous process of C7 and a line through the tragus of the ear.
Head on neck angle:
Formed by the line drawn through the anatomical markers at C7 and the tragus of the ear, and the line through the canthus of the eye and the tragus of the ear.
Head and neck on trunk angle:
Formed by a line drawn through the anatomical markers at C7 and the tragus of the ear, and the line drawn through the anatomical markers at C7 and the greater trochanter.
Trunk angle:
Formed between the line drawn through the markers at C7 and the greater trochanter, and a vertical line through the greater trochanter.
Lower limb angle:
Formed by the line drawn through the anatomical markers placed at the greater trochanter and the ankle, and the vertical line drawn through the greater trochanter.
A lesser craniovertebral angle and higher head on neck angle and head and neck on trunk angle with increasing backpack loads found in our study is supported by many previous studies. The smaller craniovertebral angle, higher head on neck angle and head and neck on trunk angles indicate the forward head position in response to posterior backpack load. Persistent forward head posture was found to be the major cause for many musculoskeletal disorders around neck and shoulder region in adults. Lesser craniovertebral angle or forward head position has been associated with greater neck disability, tension type headaches, syndromes of the neck, temporomandibular disorders, increased incidence of cervical and interscapular pain and headache etc.
The striking finding in this study was that decrease in trunk angle and an increase in lower limb angle in response to 5% of backpack load. This sagittal trunk shift may aggravate the dorsal and low back pain. These significant alterations in postural angles may cause or precipitate pain related musculoskeletal dysfunction, significant changes in respiratory parameters and metabolic cost measures.
Grimmer, et al. reported similar changes in sagittal position of body segments to adjust the body’s center of gravity to accommodate a posterior load. They, however, could not find evidence to support the rule-of-thumb that loads should be limited to 10% of body weight. Further, Haselgrove and Straker reported carrying backpack less than 30 minutes actively to school may decrease the odds of back and neck pain.
Absence of female participants was the limitation of this study and this aspect warrants further exploration in terms of higher reports of neck or back pain in female students carrying backpacks. Awareness should be created among health care professionals, teachers, parents to restrict backpack load less than 5% of bodyweight by using school locker shelves, compact discs, USB flash drives and need to regularly monitor the musculoskeletal problems associated with carrying heavy backpack load in preadolescent children. So musculoskeletal dysfunction and its relation to preadolescent postural responses to backpack load need to be further explored through longitudinal and prospective studies, respectively to determine whether carrying backpack increases the incidence of regional pain and to correlate these clinical implications on school children.
