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Let’s first define “building your base.” It is a term that is thrown around in the triathlon world, but seems to have many definitions and meanings. For the sake of this article we will define base as your “aerobic development, or increasing the ability to utilize oxygen in the process of creating energy.” This, in theory, improves our ability to use stored fat for energy and allows improved overall efficiency and endurance.
Most people would agree that a great aerobic capacity is critical to an athlete’s performance, and one train of thought believes that the only way to gain this ability is with long duration training at very low intensity. While I most certainly agree with the importance of aerobic development, I do not subscribe to that methodology. It should be noted that I do believe that aerobic development takes years, and this is a major reason that I always try to lay out a multi-year plan for any athlete, which will allow progression and benefits from consistent and progressive training.
Any training plan that suggests sticking entirely to one low intensity for an extended duration defies what we know about how the body responds best to the stimulus of training. It responds well to variance in intensity and a balance of stress with recovery (to allow adaptations). The biggest negative hormonal stress comes from high volume and duration of training—which is what is needed for the stated approach to be beneficial—combined with monotony, or one intensity. Low intensity and higher volume training actually places plenty of stress on the system without providing additional gains that it often claims.
The claim is often made that it is critical to keep intensity low to improve fat utilization, but this is only partially true. Various factors can affect fat utilization, including diet, state of fatigue and training at much higher intensity, thus aiding buffering of lactate and increasing fat uptake. It is very hard to pinpoint the optimal intensity for fat uptake, and not even really needed to improve aerobic ability in training. Through consistent training at a range of intensities you will increase aerobic development and your uptake of stored fat. What is worth knowing is what those intensity ranges are as well as how to monitor or feel them in training, hence one of the benefits of physiological testing.
I would suggest to always hit every intensity, from high to low, each week. That said, the ratio of your training load that is made up of high or low intensity should change as you go through your phases of training. Early in the season, which could be called your base phase, you should be preparing the body for heavier training loads later in the season while ensuring that you remain injury-free. You should therefore have the greatest portion of your training at a lower intensity, but still include some medium and higher intensity training to maintain speed, neuromuscular firing and hormonal balance. As you progress there should be an increasing focus on intensity, with subsequent drop in volume, before becoming specific to your race intensity in the weeks before your race.
The concept of aerobic “base,” or development, is certainly key, but don’t be fooled into thinking that the only way to gain it is through miles and miles of very low intensity. While training should be highly individual, with a focus on needs of the athlete versus a “one size fits all” methodology, there is no doubt that every athletes always needs to hit each intensity, each week, to become the most well-rounded and successful competitor possible.
Matt Dixon is an exercise physiologist, former professional triathlete, elite coach and the owner of the San Francisco-based professional coaching company Purplepatch Fitness.
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