Fractional anisotropy values of calf muscles in normative state after exercise: preliminary results.

Purpose: We measured fractional anisotropy (FA) of calf muscles from diffusion tensor (DT) images from simultaneous scanning of bilateral calves and determined changes in values after unilateral exercise loading.

Method: We obtained DT images of both calves of 10 healthy male volunteers and measured FA of the anterior tibialis, gastrocnemius, and soleus muscles. Two of the ten were subjected to loaded exercise in their right calves; we recorded FA values immediately after exercise and 24 hours, 72 hours, and 1 week later.

Results: At rest, the mean FA values of the 20 calves were 0.63+/-0.02 in the anterior tibialis, 0.56+/-0.05 in the gastrocnemius, and 0.57+/-0.04 in the soleus muscles. The differences were statistically significant (P<0.001) by analysis of variance (ANOVA), and differences between anterior tibialis and gastrocnemius (corrected P<0.01) and anterior tibialis and soleus (corrected P<0.01) muscles were significant by Bonferroni post hoc test. The FA values of the exercise-loaded soleus and gastrocnemius muscles of the 2 volunteers decreased just after exercise but gradually recovered to the baseline after one week.

Conclusion: Our method may be useful for assessing minimal muscle damage related to muscle fatigue.