[header] How to protect yourself from an acl tear [title] Warm up your muscles before exercising. [step] As you prepare to practice or play a game that may strain your acl, be sure to warm up fully. This should happen about 10-15 minutes before activity. 
Warm up with a series of stretching and exercises intended to enhance blood flow and bring oxygen to the knee joint muscles. These will also increase the flow of lubricating synovial fluid, which helps your knee joints function smoothly.