Early running goals are often as simple as completing your first 5k or 10k race. It’s isn’t long, however, before these initial targets and the joy of conquering them are left in the dust behind you. Lactate Threshold is a perfect metric to master when the time comes to start exploring what you are truly capable of as runner.
Learning what your Lactate Threshold means, how to track it, and how to improve it unlocks important new perspectives that will help you become a better, smarter runner. Before getting into the complicated details, let’s start with a simple, functional definition that everyone can understand.
Lactate Threshold is roughly the level of intensity that you can sustain for about an hour. Already, from this simple definition, it should be clear why Lactate Threshold is an essential marker for anyone interested in endurance performance. It effectively describes your ability to tolerate hard exercise for extended periods of time.
You should also know that your Lactate Threshold can increase with regular training. As this happens, you will be able to run harder for longer periods of time before getting shut down by fatigue.
Starting with Running Physiology
You have a marvelously complex running machine at your disposal. The number of processes and systems working together is mind boggling. We continue to learn more every day as scientists and researchers make new discoveries and unravel old theories.
Human physiology is well suited for both short bursts of speed and long, even very long, runs. Though genetics determine much about the equipment we have, our bodies change and adapt to stress (exercise), giving us massive potential for improvement.
To tap into that potential and improve your running, it helps to know a bit more about how your body reacts to exercise. With a touch of science and a few numbers, you get the tools and understanding you need to start improving your running performance.
Aerobic Performance Fundamentals
Skeletal muscles have two principle types of fibers, slow-twitch and fast-twitch. These fibers get energy from different metabolic processes depending on one crucial factor: oxygen. We need oxygen to survive not least because our best process for creating energy, aerobic metabolism, requires it.
While we can sprint fairly well for a two-legged beast, our bodies are best suited for long, aerobic efforts. Aerobic metabolism produces the most energy and can use the widest range of fuels, such as sugars, fats, and even proteins. Your overall fitness covers many dimensions, but a primary indicator of your fitness level is your cardiorespiratory fitness. In scientific terms, this is your maximal oxygen uptake, known as VO2max.
VO2max – Aerobic Performance Capacity
VO2max is a measurement of your body’s ability to bring in oxygen through your lungs, transport it through your blood supply to your muscles, and use it for aerobic metabolism. It literally is the biggest volume of oxygen you can take in and use in your muscle cells during one minute of maximal exertion.
The VO2max measurement is expressed as milliliters of oxygen per kilogram per minute. This translates to a number usually in the 30-45 range if you exercise regularly. Professional athletes see scores in excess of 70. Age and gender are factors in your score, which is an interesting twist. We can also look at VO2 max as your “fitness age.” This ties into the fact that your aerobic fitness level plays a major role in your overall health.
Nowadays you don’t need to go to a laboratory to measure your VO2max. Sports watches and other devices have features like VO2max Fitness Level by Firstbeat analytics. These devices can give you a quite accurate score without lab equipment, and without having to put in absolute maximum effort.
The higher your VO2max score, the fitter you are. However, a high VO2max does not mean you are going to be a great athlete. The human body does not rely purely on aerobic metabolism. You are always doing some work that uses anaerobic processes which do not require oxygen. Normally, these aerobic and anaerobic processes are in balance.
If you run too fast for too long, you throw these processes out of balance and hit the proverbial wall. To avoid hitting that wall and still improve your running performance, you need to know another measurement – your lactate threshold.
Lactate Thresholds and What They Mean
Lactate, or lactic acid, used to be considered just a waste product of anaerobic metabolism that caused sore muscles and muscle fatigue. Today we know that is not the case at all. Lactate is something your body needs. Among other functions, it serves as a fuel source for certain organs, including your brain. You are producing small amounts of lactate all the time through glycolysis, the anaerobic process the breaks down sugar (glucose) for energy.
The burning you feel is caused by the general acidity in your muscles and blood due to intense activity. When that acidity gets really high, you not only feel the burn, your muscles stop working because your normal metabolic processes are disrupted by the imbalance. Lactate actually works as a buffer and protects your muscles from acidity.
LT1 and LT2
During low intensity runs, your body is not using anaerobic metabolism any more than if you were resting. At some point, though, anaerobic metabolism kicks in, either because you have been running so long or you increased your pace. You passed your first lactate threshold, LT1, also known as your aerobic threshold.
After LT1, your body is using anaerobic metabolism more, so there is more lactate in your system than normal. This isn’t a problem. The extra lactate is just an indicator that you are shifting gears. Some of the lactate is going to other organs as normal, and the excess is heading to your aerobic metabolism as an additional source of energy.
As you increase your pace, your body needs to augment aerobic metabolism with anaerobic metabolism more and more. Eventually, you reach a second lactate threshold, LT2, also known as the anaerobic threshold. LT2 is usually what people refer to when talking about “lactate threshold.” When you cross LT2, you are going to hit the wall pretty soon.
After LT2, you are producing so much lactate that your body cannot use it all. While lactate does not cause pain and fatigue, the amount of lactate in your blood correlates closely to the processes that do. You cannot sustain an effort above LT2 for very long, but you can keep going for a long time if you stay just below it. That is your maximal lactate steady-state workload (MLSS).
Your lactate threshold (LT2) is the primary indicator of your endurance performance. The higher your lactate threshold, the faster you can run for longer periods. Two people with the same VO2max score who have different lactate thresholds will perform differently. This also means that someone with a lower VO2max but higher lactate threshold can outperform a competitor with a higher VO2max but lower lactate threshold.
Your LT2 can be derived from heartbeat analysis. Firstbeat’s Lactate Threshold feature gives you an accurate threshold value, known as you lactate threshold heart rate (LTHR). Note, however, that such analysis requires a range of good heat rate data, above and below your current LTHR. You also need a chest worn heart rate sensor. The reason you need a chestbelt to get this insight isn’t to sell belts. Instead it is simply a need for high-quality heart rate variability data during vigorous physical activity. The ability to precisely locate exactly when a heartbeat occurs with an ecg-type belt makes this possible.
Training to Improve Your Fitness (VO2max) and Endurance Tolerance (Lactate Thresholds)
Once you know your LTHR, you can use it to adjust your heart rate zones. These zones are important for your training program. Set up your zones something like this:
With your personalized zones, you can keep track of how much time you spend in each zone. As you train and develop, though, keep in mind that your zones change as your VO2max and LTHR improve.
When you exercise, your body adapts to the repeated stress, much like your hands develop callouses from repetitive friction. Ask any guitar player. The adaptations in your body happen on many levels, from increased heart size and stroke volume to changes at the cellular level that all contribute to better performance.
Considerations for Future Training
The mistake that most of us make is training too hard. It may seem counter-intuitive, but the best way to improve your lactate threshold, and thus your MLSS is through endurance training. Running at easy to moderate intensity for lengthy periods increases your body’s ability to clear lactate. This corresponds to the ability to maintain higher intensity for longer periods. (Remember, lactate is not the problem.)
High volume endurance training lays the foundations for your running performance. Most of your running time should be in zones 1 and 2. Top runners spend as much as 80% of their total training time at low or moderate intensity.
Running in zones 3 and 4 improve your lactate threshold as well as your VO2max, but they stress your body more, so should not be a big part of your training. Zone 5 should be the smallest part of your program, like a few minutes compared to the hours spent in zone 2. High intensity interval training (and resistance training) help build fast-twitch muscle fibers, increasing your anaerobic capacity.
Your training program as such depends on your goal. Training to improve your 5K time is lot different than training for a half-marathon, for example. That said, regardless of your specific goal, it is important to keep things fresh and balanced. Always be sure to build your training program with a variety of different types of efforts.
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