The pain in the arm after practicing dumbbells is mostly due to muscle fatigue or increased lactic acid formation in the muscles after strenuous or prolonged exercise during dumbbell practice. The pain is usually reduced in the flexion position, but becomes more pronounced in the extension. If you need pain relief, you can take oral pain medications such as ibuprofen or celecoxib, or non-opioid painkillers such as tramadol. At the same time, you should stop practicing dumbbells during the days of pain, that is, stop producing some strenuous movements of the arm, and you can also take a warm bath or hot bath to promote local blood circulation, to accelerate the receding of lactic acid and reduce pain.