How long does it take to heal a muscle strain?

Depends on tear: This really depends on what muscle was involved and what grade of tear (strain) is involved. Rather than immobilization, gentle mobilization exercises are helpful to prevent scarring and possible chronic pain. Typically, a grade 3 tear, it can take 8-12 weeks to completely heal. Obviously, with lesser injury. Working with a physical therapist or certified athletic trainer can be helpful.