Kelelahan kerja merupakan salah satu masalah kesehatan pekerja yang dapat menimbulkan kecelakaan kerja dan produktivitas menurun. Penelitian ini bertujuan untuk menhetahui faktor internal yang paling dominan diantara jenis kelamin, aktivitas fisik, lama tidur, kualitas tidur, IMT, persen lemak tubuh, asupan energi, dan kebiasaan merokok yang dihubungkan dengan kelelahan kerja pegawai pengemasan. Penelitian ini menggunakan data sekunder dari pengumpulan data mengenai kelelahan yang dilakukan oleh bagian quality control PT. X Tangerang. Penelitian ini dilakukan pada bulan Juni -Juli 2016. Penelitian bersifat kuantitatif dengan menggunakan metode pendekatan potong lintang. Hasilnya menunjukkan bahwa 13% respondonden mengalami kelelahan kerja ringan, 47% responden mengalami kelelahan kerja sedang, dan 40% responden mengalami kelelahan kerja berat. Hasil perhitungan statistik chi - square diketahui terdapat hubungan yang bermakna antara aktivitas fisik, kualitas tidur, dan persen lemak tubuh dengan kelelaham kerja. Hasil analisis regresi logistik ganda menyatakan bahwa kualitas tidur merupakan faktor paling dominan terhadap kelelahan kerja. Maka dari itu pegawai dan manajemen PT. X Tangerang perlu memperhatikan aktivitas fisik , persen lemak tubuh, dan khususnya kualitas tidur pekerja untuk mengurangi terjadinya kasus kelelahan kerja

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Work fatigue is one of the workers’ health problems that can cause accidents and decreased productivity. This research aims to determine the most dominant factor among gender, physical activities, sleep duration, sleep quality, IMT, percent of body fat, energy intake, and smoking habits which related with work fatigue of employee. This research is using secondary data from the data collection about fatigue which conducted by quality control section PT. X Tangerang. This research was held on June – July 2016. This research is a quantitative which uses approach method. The result shows that 13% of respondents had a small work fatigue, 47% of respondents had a medium work fatigue, and 40% of respondents had a heavy work fatigue. The result of statistic calculations chi-square shows that there is a significant relationship between physical activities, sleep quality, percent of body fat, and work fatigue. The result of double logistic relation analysis chi-square shows that there is a significant relationship between physical activities, sleep quality, and percent of body fat with work fatigue. The result of double logistic regretion analysis shows that sleep quality is the most dominant factor against work fatigue. Therefore, employee and management PT. X Tangerang need to be concerned about physical activities, percent of body fat, and especially sleep quality of the employee to decrease the number of work fatigue cases.