For sudden onset elbow tendonitis, use of cold for the first 3-5 days is ideal. This is because it helps limit the swelling and inflammation in the area, which can contribute to pain. Ice can also be used after the first 5 days for pain relief. However, after the first 5 days of a sudden onset tendonitis, or for tendinopathies that have been painful over a longer period, heat may be better. This is because the heat increases circulation to the elbow, which aids in healing and decreases the tightness and guarding of muscles at the elbow. Despite these guidelines, more and more research is showing that when it comes down to heat vs cold, the best to use is the one that feels the best to you.