A Rugby Player Case and the Mismatch Between MVIC and Tendon Strain

The case is a professional rugby player with a medial soleus muscle tendon junction injury on a background of mid-portion Achilles tendinopathy. He could hold heavy loads in plantar flexion but less, with more pain, in 10 degrees of dorsiflexion. Rehabilitation moved him from inner range holds to plantargrade, then dorsiflexion and push isometrics, monitored with a seated MVIC test, before pushes in risky positions and eccentric work. Peter then explains that the strain range thought to drive adaptation, about 4.5 to 6.5%, is reached at very different MVIC levels in different people. Data from a research group in Berlin show wide variation in maximal Achilles strain. Since strain is not yet measured in clinics, near maximal efforts of 80 to 100% are the safest way to ensure enough strain. A strong muscle with a compliant tendon, common in elastic athletes, may raise injury risk and calls for high intensity, short isometrics. A weak muscle with a stiff tendon may suit blood flow restriction or isotonic training.