Employee stated he was unloading supplies from the section supply cars onto the scoop. While doing so he lifted a large box of glue with his arms extended too far out. When he lifted he felt pain in his right arm on the inside of his elbow. The glue box was 36"" long, 8"" high & 10"" wide. Estimated weight 30 lbs. The box was in good shape, and the plastic bands were intact.