What are sub-threshold rides?

Sub threshold workouts are specifically designed to improve your body's ability to utilize fuel more efficiently for long rides and races. By riding at 80-85% of your threshold heart rate, you teach your body to improve free fatty acid oxidation, which essentially spares limited muscle glycogen. You also increase mitochondrial density, the structures within muscles cells that are responsible for producing energy. Riding at sub-threshold pace also increases your muscle glycogen storage capacity thus improving your ability to produce more intense work later in your ride. Sub-threshold rides are a crucial component of any training session. Begin with three sets of fifteen minutes of sub-threshold work with fifteen minutes of recovery between efforts. Increase the time of the interval to twenty minutes, and then twenty five minutes as you are able to hold longer and longer intervals at sub-threshold pace. The goal is to increase the total amount of time at sub-threshold pace to two to three hours for Ironman racers, as this is likely race pace for Ironman distance racing. Be sure to properly warm up and cool down with this workout.