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IRONMAN 70.3 - 12-week Base Build (Intermediate)

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IRONMAN 70.3 - 12-week Base Build (Intermediate)


Dr. Chris Myers

All plans by this Coach


13 Weeks

Plan Description

Welcome to the 3 Sports Science IRONMAN 70.3 12-week (Intermediate) – Base Phase Training Plan. This 12-week plan is a balanced training plan across the sports of swim, bike, and run with the goal of increasing your aerobic endurance. This plan assumes you have a low to moderate fitness and fits well early in the base period of an Annual Training Plan. This plan is written for you to utilize running power, heart rate, pace, or rate of perceived exertion (RPE) as your pacing guide. The general outline of the plan is as follows:

Monday – Day off
Tuesday – Bike cadence drills and broken tempo run
Wednesday – Short to middle distance swim intervals and resistance training
Thursday – Moderate endurance to tempo cycling and short endurance run
Friday – Short distance swim intervals
Saturday – Brick
Sunday – Long run and endurance swim

This entire program is written by Dr. Chris Myers who has a Ph.D. in Exercise Physiology, specializing in endurance physiology, and has a background in sports nutrition. He is the Head Coach and founder of 3 Sports Science, USAC Level 1 Coach, USA Swimming Level 4, USAT Level IIE, and IMU Certified coach.

Thank you for your interest in this training plan. If you have any questions, comments, or need clarification, feel free to email Chris at

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Training Plan Sample Week


Average Weekly Breakdown

Workouts Weekly Average Longest Workout
Bike x3
03:55:00 02:30:00
Swim x3
01:57:00 01:40:00
Run x2
00:42:00 01:07:00
Custom x1
—— ——
Day Off x1
—— ——
Strength x1
01:09:00 01:00:00
Workouts Per Week Weekly Average Longest Workout
03:55:00 02:30:00
01:57:00 01:40:00
00:42:00 01:07:00
—— ——
Day Off
—— ——
01:09:00 01:00:00

Training Load By Week

This plan works best with the following fitness devices:

  • Power Meter
  • Heart Rate Monitor
  • GPS

All supported devices

Christopher Myers

3 Sports Science

My coaching concentration is in power-based workouts for swimming, cycling, and running. I have the ability to tie all these together for multisport athletes too.

I offer coaching services for cyclists and triathletes from recreational to the elite. This includes all cycling disciplines and short and long course triathlon. Additionally, I offer coaching services for triathletes and swimmers.

Please go to for the pricing of services.

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Refund Policy

This plan is protected by our Refund Policy and may, with the author's approval, be exchanged for a plan of equal value from the same author.

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