Purpose Incidence and prevalence of Korean teenager cheerleading injuries were surveyed. Methods A total of 769 junior cheerleaders who participated in National Sport Cheerleading Competitions responded to a questionnaire, and 435 reported experiences of injuries. Results Risk factors for injury included older age (p<0.001), increased experience (p<0.001), and higher BMI (p<0.05). The most frequent injury occurred at wrist, ankle, knee, shoulder and waist. And the most responded types of injury were muscular pain and contusion. Cheerleading experience affected on injury prevalence. They were injured when they perform Elevator (<0.5 yrs), Cradle (0.5-1 yrs), Cradle and Basket toss (1-2 yrs), Cradle and Pyramid (2-3 yrs). These techniques involved in bodily movements of going up and cradle. About 56% of injury was treated at home or not treated at all, and 60% of injury was either self-treated or not intervened. And only 32% of cheerleaders practiced on a formal mattress. Conclusion Safety measures for these youth cheerleaders are necessary and guidelines for securing safety and preventing and treating injuries for these population are urgent.
Whether a nocturnal exercise with concomitant increase of body temperature (Tb) would intensify circadian phase delay compare to exercise with a suppressed Tb increase was examined. Seven healthy men (20.57 ± 2.88 yrs, 174.43 ± 4.05 cm, 70.13 ± 6.07 kg, 10.74 ± 1.92% fat) participated in two tests. Each lasted 5-days. On the day of 1 of each test, subjects maintained habitual sleep time (23:00-07:00, 0.2 lux) in laboratory. From day 2 thru 5, they biked for 60 min at 55% of maximal capacity beginning at 01:30 (15 lux). Then they went to bed at 04:00 and woke at 12:00. During test, they exercised either at 26℃ with elevating Tb (ET) or at 17℃ with cooling devices for suppressing Tb (ST). Two tests were counter balanced and separated by 2 weeks. During exercise, rectal (Tre) and skin (Tsk) temperatures, and heart rate were continuously recorded. Body weight changes during exercise were measured. Urine volume and saliva sample were collected. Blood samples were taken at 23:00, 03:30, 07:00, and 12:00 on day 1 and 5 of tests and analyzed for melatonin. The average weight loss for 4 days of exercise in ET and ST was 0.62 ± 0.09 and 0.22 ± 0.07 kg, respectively (p<.001). Tre increased during exercise but not different between conditions. Tsk maintained at 32℃ in ET and 24℃ in ST (p<.001). Tb were higher in ET than ST during exercise (p<.05). The average total urine volume passed was 0.07 ± 0.07 in ET and 0.11 ± 0.07 liter in ST (p<.05). The melatonin concentration at day 1 was 23 ± 26, 107 ± 45, 98 ± 46, and 14 ± 5 in ET and 18 ± 10, 108 ± 65, 103 ± 75, and 14 ± 12 pg/ml in ST for each time period. At day 5, it was 9 ± 3, 64 ± 41, 122 ± 73, and 54.1 ± 17.8 in ET and 8 ± 1, 68 ± 21, 111 ± 52, and 32 ± 14 pg/ml in ST. Differences of melatonin between ET and ST at day 5 of 12:00 as well as between day 1 and 5 at 12:00 of both conditions were noticed (p<.05). Salivary cortisol and immunoglobulin-A were not different. A nocturnal exercise induced a circadian phase delay in both conditions. However, body temperature increase during exercise intensified the shift indicating the importance of thermal load during exercise for circadian shift.
