Objective
To assess the prevalence and contributing factors for myofascial pain syndrome in male adolescents and to evaluate the association of thoracic kyphosis and myofascial pain syndrome.

Method
Four hundred thirteen male students of three high schools and one middle school were randomly selected. With the diagnostic criteria of palpable taut band, spot tenderness and pain recognition, myofascial pain syndrome in trapezius and infraspinatus were diagnosed. Thoracic kyphosis and pressure pain threshold were measured and contributing factors were collected with questionnaire. The relation between thoracic kyphosis and pressure pain threshold was evaluated and contributing factors for myofascial pain syndrome were compared.

Results
The prevalence of myofascial pain syndrome was 31.5% in trapezius and 1.0% in infraspinatus. Mean pressure pain thresholds were low in latent trigger point and myofascial pain syndrome group in comparison with normal group (p＜0.05). There was no statistically significant correlation between thoracic kyphosis and pressure pain threshold. Aging and uncomfortable desk and chair were associated with high risk of myofascial pain syndrome.

Conclusion
Myofacial pain syndrome is common in male adolescents and inadequate posture due to uncomfortable desk and chair rather than physical attributes like thoracic kyphosis is a contributing factor. Proper education and prevention are needed.