MUSCULOSKELETAL BACK PAIN

both neck and back pain were increased by higher physical activity in both genders, in comparison with average activity levels (13). In contrast, Sjolie found that the risk of back pain more than halved for those accustomed to walking or cycling for more than 45 minutes, after adjustment for other contributing factors (5). It is also possible that walking and cycling may place less strain than other activities on the lower back, meaning that high levels do not incur greater risk. In any event, all these studies were cross-sectional, and so Sjolie’s findings could relate to spinal pain inhibiting activity levels as much as vice versa. Some relevant longitudinal studies have been done, and their results seem to suggest that exercise is not harmful and may even be beneficial. A Canadian study observed 500 initially pain-free adolescents over 1 year and found that participation in sports did not affect the risk of neck pain, whether the sports were looked at generally or examined in separate categories (16). This analysis was quite rigorous as it corrected for other factors such as mental health and body size, and it characterised sports participation by both its intensity and frequency. A large-scale Finnish study showed that male adolescents participating in exercise more than twice a week had a reduced risk of back pain 25 years later, although this was not seen for females, and no such associations were observed for neck pain (17). These results should be viewed with some caution, as the very long follow-up makes links between baseline activity and later pain rather tenuous. Another prospective study was carried out in Belgium and showed that back pain at follow-up was less likely to arise in those who walked to school at baseline (18). Although this study was in pre-adolescents, its findings tally well with the cross-sectional findings described by Sjolie (5), supporting the notion that low-impact aerobic exercise appears to have a protective effect. A major limitation of most of this evidence has

been the poor measurement of sporting activity. Activity levels were often categorised into two broad groups, such as brisk and light (2) or passive and active (13). Moreover, they all relied on the adolescents to accurately and honestly recall activity when answering a questionnaire. There is some evidence that asking adolescents to recall and report their own activity levels over the past week or month, as these studies did, does not correlate with more objectively measured activity levels. Wedderkopp and colleagues noted less back pain with more self-reported activity in 325 adolescents, but this relationship was not observed when accelerometer measurements, which record the force and number of whole-body

movements over 24 hours, were used (19). With these drawbacks in mind, it is difficult to be sure of the true relationship between strenuous activities and spinal pain. It appears possible that walking and cycling may be beneficial, even at higher levels, but that highest levels of some activities may incur a risk. However, the vagueness of the study designs precludes any sport-specific advice as yet. Certainly it would seem premature to advise athletes against high-level sport on the basis of these findings.

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WORK Two longitudinal studies have investigated the effects of employment on adolescent spinal pain. In a study of 500 initially pain-free adolescents, Ehrmann-Feldman and colleagues found that those who worked had an almost two-fold risk of developing neck pain after 12 months (16). A similar study by the same group looked at the effect of the type of work on the later incidence of first-time back or neck pain and found that adolescents with white-collar jobs had an almost five-fold increased risk of developing back pain within the next year (20). Similarly, those involved in childcare jobs had over double the risk of developing neck symptoms. Surprisingly, more vigorous blue-collar work did not carry a significant risk for either complaint.

SCHOOL BAGS Carrying a school bag has long been thought to play a role in the development of adolescent spinal pain. Brackley and Stevenson reported an association between back pain and the carrying of bags heavier than 15% of body weight (21). An important factor may be the perception of how heavy the bag is. Haselgrove and colleagues showed that adolescents who perceived their bag to be heavy had a much greater risk of both back and neck pain (22). This may relate to trunk strength and endurance, with less well-conditioned adolescents perceiving a greater load and also being less able to withstand the spinal stresses imposed by the load. Grimmer and Williams showed that an increased duration of bag-carrying also relates to back pain (23). Similarly, Haselgrove and colleagues showed that carrying a bag for more than 30 minutes carried a greater risk for neck pain. They also showed that this risk was reduced in adolescents who walked or cycled to school (22). This suggests that the benefits of low-impact aerobic exercise described earlier may offset the negative effects of carrying a bag. The method of carrying the bag (over one shoulder, across both shoulders or in the hand) should, in theory, influence posture during carriage and thus might influence spinal pain, but so far this has not been shown (22,24,25). All of these studies were cross-sectional, but as it is

unlikely that spinal pain would actually lead to an increase in the carrying duration or bag load we can be reasonably confident of the direction of any causal effect. However, the findings could still be correlative rather than causal. For example, carrying a bag might simply be related to another factor, such as socioeconomic status, that is the real cause of any pain. Hence, definitive conclusions are not possible at this stage. Nevertheless, until evidence emerges confirming the safety of carrying a bag, caution would suggest not carrying a bag that feels too heavy for too long.

SUMMARY OF ACTIVITY ADVICE Although much of the evidence is limited, and further studies need to be carried out, the literature suggests that adolescent spinal pain development may be reduced by the following advice: n When engaging in sitting activities such as computer use and watching television, care should be taken to avoid postural extremes, especially excessive lumbar lordosis or a poking chin (Fig. 1). A neutral, well-supported posture is ideal (Fig. 2). Care should be taken to avoid tension in the shoulders, and active breaks should be taken regularly. These

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