[header] How to safely strengthen hamstrings after an injury [title] Visit your doctor. [step] Even if you don't believe your injury is severe you will want to visit with your doctor. Your doctor will be able to accurately gauge the severity of your injury, offer treatment, and get you started towards a quick recovery. 
If you have a hamstring injury visit your doctor before beginning any treatment or recovery exercise regime. [substeps] There are three grades of hamstring injury.