When working with athletes the question often comes up “should I train by time or by distance?”. This is a legitimate question but doesn’t have the simplest of answers. Like many endurance athletes my mind works off of miles best. Knowing how far you have gone is a key component in training but this is just one variable, it also helps to know how much time it took you. We all know that it takes a lot more work to cover a given distance fast. This also leads us to yet another variable, intensity. If you know how far you went and how long it took you and at what intensity, you know have what we call “training load”.
I write training programs for dozens of people throughout the year. Some are done based of mileage while others are based of time. Either one is manly chosen based on personal preference. If a person is only training one specific discipline, then either or will suffice. If a person is training multiply disciplines now things get a little tricky. It’s difficult if not impossible to quantify “x”miles of running equals “x” miles of biking. In this case using time makes the most sense for training because 30 minutes of running and 30 minutes of biking are the same, as long as they are at the same intensity level. This makes for an easier way to progress the training by adding minutes or intensity to the workouts.
This all comes back to training load which I had mentioned earlier. This is the ideal way to keep track of your training. Training Load = Time x Intensity. The tough part of this equation is figuring out how to put a number to the “intensity” aspect. You can use heart rate or perceived rate of exertion or percent of max intensity but you have to come up with a number system that you can be consistent with. An example would be if you did a tough threshold workout for 20 minutes and on a scale of 1-10 it was an 8.
(20 minutes’ x 8 = 160 Training load).
Now if I go out for a casual paced workout of 20 minutes the training load would look more like this.
(20 minutes’ x 6 = 120 Training load).
Whenever I write a training program this is the equation that is running in the back of head when writing the workouts, doesn’t matter if the training plan is written in miles or minutes I can progress them at the correct rate.
Bottom line is this. If you like miles for training, stick with it. If you prefer minutes, stick with that. But either way try figuring out what your daily and weekly training load is. You might start to see patterns of why some weeks feel harder than others. It will lead to better training and better results in the long run.