Lactate Threshold Simplified

Lactate Threshold – What It Is and Why It Matters to Us

Lactate Threshold refers to an energy and production state in our bodies when we exercise. Essentially, it’s an exercise intensity that is sustainable for about 60 minutes.

Lactate, or lactic acid as it’s often called, is a chemical byproduct of muscular activity. Being highly efficient, our bodies immediately recycle lactate to fuel more activity while we exercise (or play). However, at a certain level of intensity, we produce lactate faster than we can recycle it. So, the muscles flush away the excess. When we reach this level of intensity, we start to feel fatigue and a muscular burning sensation. Depending on how far beyond this threshold we push, the fatigue and burning can become quite significant until we have no choice but to stop what we’re doing.

Now this is the ironic part. That burn is NOT caused by the lactate or lactic acid. True, it is an acidic response to the exercise intensity however, it is coincidental to the accumulation of lactate. Lactate is simply the chemical substrate we can measure and it just happens to correlate with the acidosis taking place in the tissues. How’s that for a fun fact to know and tell?

So, the threshold is sort of like a cliff. What’s interesting is that as our work intensity increases, our ability to maintain a sustained effort goes from multiple hours to a couple hours to about an hour. Then suddenly, our ability to maintain drops off the cliff and instead of going for about an hour, we can only make it about 10 – 15 minutes. That line between being able to go for about an hour and only about 10 minutes is the threshold.

Lactate threshold can be signaled using a variety of metrics: heart rate, power, pace, or oxygen saturation. Heart rate is the easiest, least expensive, and most accessible measurement device so that’s the one we choose at Vitruvian Fitness. We refer to the heart rate at threshold as LTHR.

In training, we use various percentages of that lactate threshold heart rate to improve different aspects of our fitness. For example, lower percentages of threshold can be used to improve general endurance. Higher percentages can be used to improve power, strength, and speed. Performing intervals of extra-high intensity followed by full recovery periods improves the mechanisms in our bodies that contribute to performance enhancement across the board, regardless of what we’re training for. A good program incorporates all of these training zones at various stages to reach peak fitness.

In sporting events (like a bike race or a 10k fun run), we can use these zones to help pace us for the activity we’re doing. Short race, intense pace. Long day, easy pace.

In days long past, we used to refer to a magical 80% of your maximum heart rate being the “aerobic threshold.” This idea was based on what we thought we knew was going on in the body. The “inventors” of this methodology had good intentions but were way off the mark. We were told that your maximum heart rate was a simple math equation based on your age and 80% of the max was the threshold and that was that. It was an oversimplification that was so wrong.

It turns out, your maximum heart rate is totally irrelevant. Blood volume, stroke volume, maximal oxygen uptake, mitochondrial density, capillary density, lactate utilization, recovery time, hydration, sleep quality, stress, . . . are all far more important, relevant, and totally trainable.

Before we go too far down the LTHR hole (as interesting as it is), let’s remind ourselves what we’re trying to accomplish. And that is, we want to get faster, stronger, healthier, more powerful and better looking. To measure this, we’ll compare two numbers and that’s how we gauge if and by how much we’ve improved.

On our indoor bikes (and in elite cycling outside), work output is measured in watts. To measure and train your threshold heart rate, we can compare your highest sustainable heart rate with the wattage you generate and then train to improve both numbers. Outside of the gym, in addition to your heart rate, you might observe your work output in miles per hour on the bike, wattage or what your pace per mile when running.

Here’s an example: in one season, a client of ours was able to increase his threshold heart rate by 14 beats per minute (10% improvement) and his power output by 60 watts (21.4% improvement). He was able to improve his cardio-vascular capacity while simultaneously improving his strength and speed. In terms that are more relevant to him, this means is he increased his cruising speed from 20 miles per hour to 24 miles per hour. In other words, he could go 4 more miles in 60 minutes without working any harder.

In summary, there are two types of objectives here. The first is to improve your general cardio-vascular fitness. This would be measured in an increase in LTHR. The second is to improve your performance at threshold. This can be measured in a variety of ways as mentioned above.

Lactate Threshold is still a topic that creates a lot of discourse because there is a fair amount of misunderstanding on the subject.  And frankly, scientists may learn more that could totally invalidate virtually everything we wrote here. Just remember why this matters – we’re trying to get healthier and go faster. Eat some good food. And have fun. In no particular order.

Want to learn more? Follow this link to a great in-depth article on the subject.


Lactate Threshold

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