Muscle strain or tear Muscles are strained or torn when some or all the fibres are unable to cope with the force. Muscle injuries commonly occur in sports. This can affect muscles such as the quadriceps, hamstrings, calves (gastrocnemius or soleus) or the rotator cuffs. Muscles are more prone to tears from training error, sudden acceleration or deceleration. Risk factors involve insufficient warm-up, inadequate rest periods, muscle or joint ...