Complex sentence: Though not the best position for prolonged meditative contemplation--the reclined position dulls the mind too much for the kind of discernment necessary to achieve deeper meditative states, this can be a successful introductory practice for those not yet ready for formal meditation.
Split into simpler sentences: Though not the best position for prolonged meditative contemplation, Shavasana dulls the mind enough that the discernment necessary to achieve deeper meditative states becomes more difficult. This reclination can be a successful introductory practice for those practitioners who are not yet ready for formal meditation.