Mike Guadango over on freakstrength.com posted an interesting variation on "split" training: splitting between postural and phasic muscles.
The idea of phasic vs. postural muscles seems to originate with Dr. Vladimir Janda, a Czech exercise physiologist.
What are postural muscles? Essentially, the muscles the keep you standing upright, breathing, and otherwise living. They are used to long, steady loads and continuous use.
What are phasic muscles? Muscles used for movement.
What would I get out of the article? The idea is to base your training intensity and frequency on the type of muscle. Postural muscles are used to long, steady loads and you would train them more often or for longer periods. Phasic muscles are used for shorter bursts of strength and you would train them less frequently but more intensely - basically, your normal "strength and mass gain" approaches.
It's an interesting approach, and it could help explain why it's beneficial to continually load certain muscles for gains while you need to do short-and-intense lifting for the rest of your muscles.