Morphological changes of the lateral abdominal muscles in adolescent soccer players with low back pain: A prospective cohort study

Background:Most papers examining the lateral abdominal muscles(LAMs)and low back pain(LBP)are cross-sectional,with groups of participants being divided into a control and an LBP group.We hypothesized that morphological measurements of the LAMs in adolescent soccer players may predict future LBP incidence.The aim of this study was to examine the associations between the morphology of LAMs and LBP incidence rate among adolescent soccer players.Methods:Ninety-seven adolescent male soccer players with no LBP at baseline were recruited into the prospective cohort study.The thickness of the LAMs was measured at baseline by ultrasound imaging in a supine rest position.Nine cases of LBP occurred during the follow-up 6-month observation.Results:An obliquus internus(OI)asymmetry was related to increasing LBP risk(odds ratio=19.99;95%CI:2.4-167.9).Spearman correlation also showed a linear relationship between OI asymmetry value and duration of LBP(R=0.75,p=0.02).An OI side-to-side difference greater than 1.25 mm suggests possible LBP incidence in the 6-month observation among adolescent soccer players.Conclusion:The morphological changes of the OI may be related to LBP’s incidence in adolescent soccer players.The presence of OI asymmetry increases the odds of LBP by at least 2.4 times.Hypertrophy of the OI on one side of the body may contribute to trunk muscle imbalance.

Recommendation on unbiased estimation of population attributable fraction calculated in"prevalence and risk factors of active pulmonary tuberculosis among elderly people in China:a population based cross-sectional study"

Population attributable fraction(PAF)refers to the proportion of all cases with a particular outcome in a population that could be prevented by eliminating a specific exposure.The authors of a recent paper evaluated the prevalence and estimated the PAFs for risk factors of TB among elderly people in China[Inf Dis Poverty.2019;8:7].Confounding is inevitable in observational studies and Levin’s formula is of limited use in practice for unbiasedly estimating PAF.In a complex survey design,an unbiased estimation of the PAF can be calculated using a sample-weighted version of the Miettinen formula or a sample weighed parametric g-formula.With respect to causal interpretation of PAF in public health setting,computation of PAF is logical and practical when the exposure is amenable to intervention.