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Capacity & Power

“Most triathletes are doing too much [high-intensity work]. You don’t need more than 1 HIT session per week.”
~Jan Olbrecht PhD

“Many recreational athletes are scared [that they’re] not training hard enough. What they need to be thinking about is training easy enough, and long enough in the low-intensity sessions to build biological durability so that the high-intensity sessions really can be developmental.”
~Dr. Stephen Seiler

Dr’s Olbrecht & Seiler, two highly respected leading sport scientists, are very clear that most people place too much emphasis on high-intensity training (HIT). Let’s take a look at the reasoning.

The physiological engine has two key aspects: capacity and power. Simply put, capacity is the size of one’s engine, i.e. the number & volume of the cylinders in an engine. Power is the degree to which that engine can be utilised.

The durability that Dr Seiler mentions refers to how robust an athlete’s hormonal, musculoskeletal, and cardiovascular systems are and the extent to which they can respond to and recover from training. Thus, engine capacity is a combination of size (how much horsepower it has) and its resiliency to the demands asked of it.

Building capacities *before* building power is important because power work can break the engine (i.e. injury and overtraining) if it’s not prepared for it. And the best way to *optimise* capacity is through a lot of volume at low intensity mixed with a few short intensive bouts at high speed. The reason is that we want to provide a stimulus to all the mitochondria—the energy-producing organelles in the body. 80-90% of the mitochondria are active at low intensity. The rest are recruited by short, high-intensity efforts.

It might seem reasonable, then, to try and activate all the mitochondria at the same time by doing a lot of work in the moderate-intensity range. However, moderate-intensity work triggers the development of power. Power is what allows us to use *the existing engine* but it is not effective at building a larger engine. In fact, doing too much high-intensity work leads to a reduction in engine capacity. As I described above, it’s important to build a large and durable engine before stressing it too hard.

Q: When do we build power?
A: In the build phase(s) of our season.

Power development comes after the base mesophase, during which training volume was increased, and right before the race phase when capacity and power will be pushed to their maximum. The goal of the build phase is to improve the maximal output of capacities that will be needed throughout the duration of a race.

Maximise the effect of your training time by continually strengthening your foundation, then spice it up appropriately.

(For more about the phases read Prep & Base. And for building endurance capacity check out Endurance Training.)