This plan was designed by Joe Friel using the principles of the The Triathletes Training Bible. The major difference between this and the "Half-Ironman Base Period (Over 50) 9-14hrs/wk" is that in this plan there is a R&R week every 4th week instead of every 3rd week. Over-50 athletes may also use this plan if they typically recover quickly after challenging workouts. You may use either heart rate or power on the bike to manage workout intensity.
This plan is best started about 23 weeks prior to your first A race of the season. Following this 12-week plan will get you ready to start the Half-Ironman Build-Peak-Race period (see Half IM Build-Peak-Race plans) which specifically prepares you for your A-priority race in the last few weeks prior.
This plan is intended for the under-age-50 triathlete who has been racing for two or more years. To start this plan you should be able to swim 1 hour, bike 1.5 hours, and run 1 hour. Over 12 weeks you will increase your weekly volume from about 9.5 hours to 14 hours including 3 swims, 2 to 4 bikes, 3 to 4 runs, and 1 to 2 strength workouts each week. The exceptions are the R&R weeks every fourth week with volume significantly reduced for 4 to 5 days and self-testing at the end of the week to measure progress.
The plan uses common language to describe the workouts and is easy to follow. By the end of 12 weeks you will have excellent Base fitness and be ready to start the Build period 11 weeks prior to your A-priority, half-Ironman race.
(For detailed description of how to set your zones for heart rate, power or pace go to http://www.trainingbible.com/joesblog/2009/11/quick-guide-to-setting-zones.html.)