The calf is made up of two muscles (gastrocnemius and soleus) at the back of the lower leg that melts together to form the Achilles tendon (TA) and attaches to the heel bone. The gastrocnemius muscle provides the sudden explosive drive for the initial ‘take off’ in running. It is the more commonly injured of the two muscles, especially in people in their forties. A strain refers to a tear in this large powerful muscle forming the bulk of the calf.
CAUSE 
A gastrocnemius strain typically occurs when the muscle is forcibly contracted whilst in a stretched position. This can occur when accelerating from a stationary position or when lunging forward, such as in tennis or squash.
A gastrocnemius strain may also occur following stepping in a pot-hole or unexpectedly down a step whilst running or walking. This may cause the heel to drop suddenly, overstretching this muscle. Factors which may contribute to this type of strain include an inadequate warm up, muscle stiffness or tightness, fatigue or overuse, an inadequate recovery period between training sessions, reduced muscle strength and faulty biomechanics.
SYMPTOMS
The first sensation you feel is a sudden pain in the calf which may be associated with a stabbing or tearing sensation. In minor tears, you may be able to continue participating with minimal hindrance. However, as the muscle cools down following completion of participation the pain may gradually worsen as bleeding and swelling around the injured muscle takes place. In more severe tears, you are unable to continue participating immediately following injury due to excessive pain, and muscle tightness. In these cases, the pain may be so intense that you may be unable to walk or correctly bear weight on the leg.
TREATMENT
Physiotherapy is the most important part of conservative treatment. It includes various treatment modalities including manual therapy, mobilisation techniques, electrotherapy modalities(laser, ultrasound, interferential therapy), exercise/technique modification, strengthening and stretching, dry needling, sports taping etc.
Other treatments include:
- Anti-inflammatory medication
- Heat or ice
- Rest from sport