At the Movement Assessment Technologies we have always been big believers in assessing and training the body in 3 planes of motion. The importance of this is particularly revealed when we look at the structure of the lower limbs and their transverse nature.
For example, the Gastrocnemius is a muscle commonly only stretched and trained in the Sagittal plane of motion but its insertion into the calcaneus is not evenly distributed in the frontal and transverse plane to allow for more effective loading of the lower shank through the subtalar joint.
Effective stretching and strengthening programs should take into account this frontal and transverse plane nature.
If you would like to learn more about how to assess the Gastrocnemius muscle in 3 planes of motion check out: