Journal of the Medical Association of Thailand Vol 100, No 2:FEBRUARY 2017 0125-2208 100 2 2017 Apr Physical Fitness and Muscular Discomfort among Informal Garment Female Workers in Udon Thani Province, Thailand 230 EN Thanyawat Homsombat Sunisa Chaiklieng Original Article This cross-sectional study aimed to investigate the prevalence of muscular discomfort and to assess the physical fitness of informal garment female workers. The subjects were 1,674 informal garment female workers in Udon Thani Province. Data were collected by using a structured questionnaire including complaints of muscular discomfort. Physical fitness tests were done by using standard tools for testing back-leg strength, flexibility and hand grip strength. The highest complaint of muscular discomfort during the last month was located at the low back (41.75%), followed by the shoulders (41.21%). Considering the severity as severe discomfort, the highest prevalence was found at the low back (61.47%), followed by neck (61.23%). Those two areas were also presented as the highest frequency of discomfort for every day pain. In general, the majority of workers had physical fitness at fair level and low back strength significantly correlated with muscular discomfort. The significant findings among informal garment workers were muscular discomfort predominantly located on the low back and the factor of low back strength correlated with that muscular discomfort. The suggestion is there should be a supporting surveillance program for prevention of chronic low back pain by a prospective cohort study as well as maintaining the physical fitness by an exercise program for these informal garment workers. Informal workers Low back pain Back strength Prevalence Garment