If your Masters swimming group meets in the evening and you run in the morning that's fine. Stick to your specified workout, however, if it calls for a bike/run brick.
Be careful not to start "stacking" workouts on top of each other if you miss one. Missing several workouts during the week can't be made up in a couple of days on the weekend.
There is no absolute minimum number of hours you can train and still complete the Ironman. The plan I developed, along with the modifiers already suggested, is along the lines of minimum. The absolute answer really depends on each individual athlete. The more you cut training hours, the longer and more torturous the race will be, and you put yourself at greater risk for injury.
More: Stay on Track
Training for an Ironman is intended to keep you burning fuel at an aerobic rate. This is when you are trying to teach your body to be an efficient fat-burning machine. When you get into the heart-rate zones near lactate threshold, your body prefers to use more glycogen as fuel, as opposed to fat and oxygen. At the same time, short bouts into sprint-pace hear-rate zones will not send you into flameout status. Although heart-rate monitoring is a good tool, it is not a precise measure of aerobic metabolism. A few beats either side of the zones won't be a problem.
Going the Distance
Training for an event like this requires a commitment to proper nutrition and especially hydration. For workouts over an hour long, you'll need to consume about one water bottle per hour and a minimum of 150 to 250 calories per hour. You can find more information on hydration here.
Training for an Ironman can be an extremely rewarding and life-changing journey. However, it requires a strong commitment and some sacrifices. Ultimately, I want you to be successful. To help you along, you can find additional free information within the "Downloads" on the right-hand corner of my Active Trainer site.
Over the years, I've received many emails and letters from people telling me about their success. The goal of an Ironman is possible, you just need to make it a reality.
More: How to Choose a Long-Distance Race
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