The blow-by-blow workout diaries of exuberant P90X host Tony Horton and the Average Joe tend to tell a very different tale on the first day of that program. If you've experienced P90X Day 1 - "Chest and Back" - you'll understand. If not, here's your heads-up. P.S.: I'm a P90X cast member and success story. It's a great program, and Tony Horton is an old buddy. But I switched to TheDailyHiit this year and haven't looked back. Why? My 10 reasons are listed here.