3) Plan fast workouts.
It doesn't matter if you're doing six workout sessions per week or nine; plan to go fast in some of them. Your body needs the stress of fast workouts—and recovery—in order to make gains.
In the offseason, make the fast segments of your workouts short with long recovery intervals. Miracle intervals on an indoor trainer are a good example of this principle or the speedy segments can be just simple 20-second accelerations. Because the fast segments are very short and you can keep the number of repeats low, you can include some speedy segments in nearly all of your workouts.
I will say there are some coaches that make the offseason completely aerobic—no efforts above the aerobic level, whatsoever. I am not one of those coaches and I believe keeping some fast training in your routine in the offseason is critical.
4) Remove threshold intervals in the offseason.
Though you should keep some fast segments in your training for most of the year, do not keep flogging yourself with the same old lactate threshold workouts year-round. Repeating high-intensity workouts day in and day out leads to boredom, risk of injury and certainly a plateau in performance.
When do you begin to add threshold training back into the fold? The answer depends on your short term and long term goals.
5) Plan key workouts.
Make your "hard" workouts count towards performance increases. These hard sessions should be considered key workouts. A key workout can work on improving your speed, endurance or in some cases both. Depending on what you're doing in the weight room, a key session may be a strength session in the offseason.
A good rule of thumb is to limit your key workouts to between two and four per week—total in all sports.
6) Consider a single-sport focus in the offseason.
If your swim is your weak link in your races, try swimming four or five days per week. Keep your swimming and cycling workouts easy and limit them to only one or two per week. If cycling is your weak link, try adding a weekly group ride as one of your key workouts. If running is your weak link, add one more run session per week, but keep an eye on injury indicators.
In all cases of single-sport focus, consider spending four to six months training for a single-sport event (a swim meet, a cycling event or a running race) while keeping the other sports maintained at a minimum level.
With some key changes to your training routine and consistency in the offseason, you will be a better—and faster—triathlete next season.
Take a strength training class in the offseason.