Purpose: Several studies have reported that musculoskeletal disorders and discomforts experienced by children and adolescent students are closely related to the weight of bags or backpacks carried by them. Since students are at growth and spinal development age, attention to the pressures on their bodies is important. These pressures can cause musculoskeletal problems and various growth disorders. This study aimed to investigate the prevalence of Low Back Pain (LBP) and its relation with the backpack weight among students. Methods: This cross-sectional study with non-experimental design was conducted on 2000 elementary and secondary school students (1000 boys and 1000 girls) who were randomly selected from schools in 5 regions of Tehran City, Iran. Students with LBP for more than 6 weeks during the study or during the last 3 years at 3 intervals that each lasted for 1 week or more were listed in a group with LBP and others in a group with no LBP (the control group). The weight of their bags or backpacks was measured over a week, and the average was recorded as the weight of carrying load. The intensity of pain was measured using the Visual Analogue Scale. To examine the prevalence of LBP in students, absolute and relative frequency distribution tests, and for examining the correlation between LBP and weight of backpacks, Independent t test were employed. Furthermore, the Pearson correlation coefficient was used to determine the relationship between the weight of backpacks and the intensity of pain. In addition, logistic regression analysis was used to assess the predictability of LBP based on the backpack weight. Results: Based on the results, 26% of students had LBP (29.6% girls, and 21.8% boys). Mean±SD scores of LBP in girl and boy students were reported as 3.4±2.8 and 2.3±5.8, respectively. According to t test results, there was a significant difference between the two groups in terms of backpack weight both in girls and boys (P<0.05). The Pearson correlation test results showed a significant correlation between the weight of backpacks and intensity of LBP among boys (r=0.26, P=0.007) and girls (r=0.31, P<0.001). Furthermore, results of logistic regression analysis indicated that the variable of backpack weight can predict LBP (B=0.52, P=0.01). Conclusion: The weight of the bags or backpacks carried by children and adolescent students has a significant relationship with the prevalence and intensity of LBP in this age group.

In recent years, many people show interest to Paralympics competition because it is dedicated to athletes with disabilities. In order to affect the throwing, static stretching can be applied on the two muscles, i.e. pectoralis major and latissimus dorsi that play an important role in the arm acceleration phase. Normally, before sport activities, static stretching is applied. Stretching increases the flexibility that is effective in the throwing. The important point is the effect of this type of stretching on the throwing function, which is a combination of muscular strength, range of motion and productive torque. This study is going to examine this issue. Methods: In this study, 45 disabled male athletes (15 discus throwers, 15 shot put throwers, and 15 javelin throwers) participated. Before stretching, each athlete did 3 throws, then a static stretching session consisting of 5 sets of 30 seconds stretching followed by 30 seconds of rest between each set, was performed. One minute after the stretching, the athletes did throwing 3 more times. Static type of stretching is performed on pectoralis major and latissimus dorsi muscles. Results: Based on study results, no significant change was observed in the amount of throw before and after the stretching (Discus: P=0.47, Shot put: P=0.46, Javelin: P=0.14). Conclusion: Considering data analysis, one session of static stretching of pectoralis major and latissimus dorsi muscles does not create a significant change in the magnitude of throw in disabled athletes engaged in discus, shot put, and javelin throw.