Boosts from Below

Entertain this for a moment. You want to improve your back squat. You sit down and look for the best way to do it. You review 5 x 5 programs, 8 x 3, and even heavy single protocols. You choose one and commit to eight weeks of progression, working at 80 to 90 percent of your one rep max. 

Over time, the body adapts. It recruits more motor units, coordinates muscle fibers more efficiently, and improves force production. The weight begins to move better. After eight weeks of deliberate training, you step under the bar and hit a new personal record.

You improved by working below your maximum, not above it.

This seems obvious in the gym, but the logic often disappears when we apply it to endurance training for Soldiers.

The endurance system works the same way. If we want to improve a specific system, we must train just below its limit. Too often, Soldiers train well above their current ability because hard work is emphasized over effective work. The result is the opposite of what we want. Progress slows, fatigue increases, and performance stagnates.

Just as you would not attempt to lift 110 percent of your one rep max to improve your squat, running at 110 percent of your current ability will not improve your endurance. It will only break you down.

There is a place for high intensity work. Strides and short finishers can be valuable additions. In these cases, we operate in a controlled state, introduce fatigue, and then briefly recruit high power output before ending the session. This is a stable way to improve.

What often happens instead is less controlled. Consider a simple workout such as 8 x 400 meters at slightly slower than 2-mile pace with two minutes of recovery. The first repetition is too fast. The second is still too fast. By the third and fourth, the pace drops off significantly. The remainder of the workout continues to degrade.

This is often labeled as toughness. In reality, tough athletes are usually just better trained. In this scenario, the athlete has overstressed the system and reduced the effectiveness of the session. Recovery takes longer, injury risk increases, and consistency suffers.

Up to this point, we have discussed targeted systems in terms of race pace. Now let’s expand that idea.

If we want to improve the body’s ability to use fat as a fuel source and expand Zone 2, we must train just below that system’s limit. This is the point where fuel use shifts from primarily fat to a greater reliance on carbohydrates. Training at this level is controlled but demanding over time.

In these sessions, the effort often feels steady at the start and becomes challenging as fatigue builds. This is where we improve muscular durability and the body’s ability to sustain work using fat as a primary fuel source.

What happens when we rely on frequent sprint sessions without this foundation? We limit the system we are trying to build. We choose workouts that feel hard over workouts that are actually useful. This delays long term development.

High intensity work should support the program, not define it. It should be applied with purpose, either to recruit additional muscle fibers or to sharpen performance once a foundation has been built. Too often, it is used as a weekly test with no clear benefit.

In the previous articles, we introduced key concepts to build a framework for training. Now that we have started to define systems and their roles, we need another lens to understand intensity.

Enter lactate.