The calf muscle consists of two main muscles, the more superficial two-headed gastrocnemius and the deeper soleus. The muscles unite at the bottom to form the Achilles tendon. The combined action of the calf muscles are  critical to the running stride as the calf first acts to provide shock absorption for the impact of foot strike and then contracts to propel push off.   

Exercise induced calf strains are most commonly found in the medial head of the gastrocnemius. 1 The gastrocnemius is considered at high risk for strains because it crosses two joints (the knee and ankle) and has a high density of fast twitch muscle fibers which are associated with power and speed. When the muscle is fatigued, sudden stretch or forceful contraction of fast twitch fibers can result in sudden strain. Muscle fibres can tear at a microscopic grade I level or more severely as a grade III strain. Pain is of immediate onset, followed by muscle spasm and tightness of the calf that can last for several days.  Gastrocnemius strain will appear to recover quickly but will tend to reoccur with early return to running unless full strength and flexibility is regained.

The soleus muscle is considered at lower risk for injury. 1 It crosses only the ankle and is largely comprised of slow twitch muscle fibers associated with endurance function. Soleus strains also tend to be less dramatic in clinical presentation when compared to injuries of the gastrocnemius. Classic symptoms are of lateral calf tightness, stiffness, and pain that slowly worsens over days to weeks. 

Calf strains tend to occur either because of weakness or tightness in either of the gastrocnemius or soleus muscles. Running faster or longer than normal, fatigue and running style can all contribute to calf strain onset.

For either gastrocnemius or soleus strain, treatment over the first three to five days should consist of rest, compression, elevation and ice to manage pain and swelling. After five to seven days, stretching and gentle muscle activation exercise should begin. Ten to 14 days after the injury, the developing scar tissue is strong enough to tolerate more aggressive rehabilitative exercises. Single leg heel raises and heel raises on a step are typical early phase exercises.  Progression to adding weights and hopping/jumping exercises (plyometrics) will help rebuild the strength of the muscle fibres and connective tissues as well as retrain neuromuscular coordination required for running. Conservative resumption of running is generally safe when single leg hopping is painfree.  Time frame for recovery is usually two to six weeks depending on extent of initial tissue damage.

Calf Cramp

Calf cramping is different from the calf strain in that no muscle fibres are actually injured.  Exercise- associated muscle cramps are generally described as a sudden, painful involuntary muscle contraction that occurs during or immediately after exercise.  2 Traditional beliefs have been that muscle cramping was caused by overheating, dehydration and electrolyte depletion but current research has not supported this hypothesis. An alternative theory is that of ‘altered neuromuscular control’. 2, 3  This hypothesis is based on evidence that suggests that the development of muscular fatigue results in altered muscle control that leads to the involuntary reflex contraction or cramp

Muscle cramps during running seem to occur with higher intensity of activity and are consequently associated with racing more than training. Cramping also tends to occur toward the end of races and with races that have hillier profiles. Poor pacing strategies are also predictive of cramping.  3  A 2011 research study on muscle cramping in Ironman Triathletes found higher incidence in faster racers, those with previous soft tissue injuries, taller athletes and those with a family history of cramping. 2  Muscles that are most likely to cramp are those that cross two joints like the gastrocnemius (crosses knee and ankle) and the hamstring (crosses hip and knee).

Not to say that proper hydration is unimportant, but the best way to prevent cramping may be to focus on appropriate and even race pace. Race specific training like hill repeats, speed intervals and tempo runs will help strengthen muscles and prepare them for race efforts. Specific strength exercises for the calf as described in the calf strain section (heel raises and plyometrics) also make preventative sense.

If you experience cramping in a race or training, the best treatment is stretching.  Ice and massage can also help with post effort management.


1.  JB Dixon Gastrocnemius and soleus strain.  How to differentiate and deal with calf muscle injury.  Curr Rev Musculoskeletal Med. 2009;2:74-77

2.  G Shang, M Collins, MP Schwellnus.  Factors associated with self reported history of exercise associated muscle cramps in Ironman triathletes: A case control study.  J Sports med. 2011; 21(3). 204-210

3.  The Runner’s Body:  How the latest exercise science can help you run stronger, longer and faster.  R. Tucker, J. Dugas, M. Fitzgerald.  Rodale Inc. 2009.  USA

(Originally published in No Limits Blog, 2012)