Lactate testing information

What is a lactate threshold test?

A lactate threshold test is a sub-maximal progressive step test. Intervals between 3 and 5 minutes are performed at progressively quicker paces. After each interval, a measurement of the lactate level in capillary blood is made through drawing a small amount of blood from a finger prick. Although this is a sub-maximal test, it will be a significant amount of work and you should be prepared to run between 8 and 12 km (5-7 miles).

The aim is to identify two key changes in your physiology as you exercise. We are looking to identify your aerobic threshold or lactate threshold 1 (LT1) and your anaerobic threshold or lactate threshold 2 (LT2). These break-points mark useful metrics that can guide your training and racing. Aerobic means with oxygen and anaerobic without oxygen.

We can estimate these markers of how your body produces energy during exercise through a variety of ways. The two thresholds can be measured using a face mask and gas analyser to measure your intake of oxygen and expiration of the waste gas carbon dioxide. In this method the break-points are expressed as the ventilatory threshold VT1 & VT2. We can also use a technique where we can indirectly measure the amount of oxygen within the muscles using a small device that emits and detects infra-red light (near infra-red spectroscopy or NIRS). Break-points determined in this way are then termed NIRS break-points 1 & 2. In the case of a lactate threshold test we use the amount of lactate within small blood vessels called capillaries.

Aerobic threshold (LT1)

Lactate threshold 1 (aerobic threshold) is the maximal intensity that can be maintained for an extended time with little or no increase of lactate in the blood. This is a sustainable exercise intensity, which theoretically can be maintained for events of 2 hours + in duration.

Anaerobic Threshold (LT2)

Lactate threshold 2 (anaerobic threshold) is the intensity at which lactate begins to accumulate in the blood at a faster rate than it can be removed, used or processed by the body. Depending on your durability as an athlete, efforts around LT2 can be maintained for around 1 hour.

We will aim to identify at which intensities the thresholds occur and express them in terms of your heart rate, pace and how hard you feel you are working using the Rated Perceived Exertion (RPE) scale.

At the end of this introduction is an simplified and brief overview of some exercise physiology. It is not necessary to read this but it can be helpful to understand what lactate is and what we are measuring. We will discuss this in brief before your test so that you can be more able to interpret the results of the test yourself.

How should I prepare for a test?

Fatigue will influence the test - be well rested

It is important to be well rested, fatigue will influence the results. We suggest not performing high-intensity exercise at least 48 hours before your test. Within 24 hours of the test keep any exercise short and low intensity. Since individuals recover at different rates, depending on your level of fitness and training history you made need to refrain from intense exercise for a longer period and consider a rest day prior to testing. Please be sensible and ensure that you are well rested for the test.

Your diet will influence lactate levels - not too much carbohydrate before

Eating a large amount of carbohydrate will increased your resting and exercise lactate levels as your body tries to process the carbohydrate. Therefore it is important not to consume large amounts of carbohydrate before the tests. We would recommend not eating 2.5 hours before testing and avoid very heavy carbohydrate meals. Smoking and caffeine can also influence the test.

What you eat and drink depends on the goal of the test. If we are seeking to understand what your race pace might be, then eating and drinking what you plan to do on race day might be sensible. If the goal of the test is to determine your training zones then it makes sense to eat what you normally eat a lest 2.5 hours before the test.

Running shoes may influence your results

If you are having a running lactate threshold test, your choice of footwear can influence the results. Some runners respond well to wearing carbon plated running shoes and will run more efficiently, using less energy for a given pace. Your choice of flatware depends on the aim of the test. If we are looking for insights into your physiology before a race, it is sensible to wear the shoes you plan to race in. If setting training zones is our goal then wearing a shoe that you typically do most of your daily training in would be best.

What to bring on the day

Since we wish to inform your training and racing then you will need some way of monitoring your pace and heart rate. If you use a GPS watch or device to monitor your training then please bring it with you. We would recommend a heart rate monitor if you wish to know at what heart rates your thresholds occur. The most accurate would be a chest strap heart rate monitor such a Garmin HRM. We can provide this on the day and may ask you to wear one of our devices so that we can be confident in the results.

What about the results?

After the test we will have an indication of the general trend of the results. However, the full results will take some time. We spend a lot of effort ensuring that the data that we analyse is representative of what happened during the test. Once we are happy with the underlying data we will carefully determine your thresholds. Rather than choosing the traditional values of 2 mmol/L for LT1 and 4 mmol/L for LT2 we will set the lactate break-points to an appropriate level depending on your results.

We will give you the raw data from your test, the analysis and report this is in a meaningful way so that you can use the results to inform your training and racing. We can prescribe training zones for you using our preferred zone model or another model of your choosing. We will express your zones and thresholds in terms of pace, heart rate, and if it is useful to you, running power and speed.

If you have a coach we would be very happy to discuss our view of your physiology with them and will provide suggestions to you and your coach on what we think you should be doing in training to reach your goals.

An overview of the physiology of energy production - what is lactate anyway?

The body needs to produce energy; a significant amount of it to exercise. The currency of energy in all cells of the body is a molecule called ATP. ATP can be produced in the body through a variety of ways. The different energy systems produce different amounts of ATP at different speeds. It is important to remember that all energy systems are used at all exercise intensities, but the relative contribution of each system changes at different efforts. Lactate is produced by your body at all times, even at rest and is a marker that you are using more carbohydrates for energy production.

At rest and slower paces the predominant energy system contributing to ATP production is the oxidation of fats. This produces a large amount of ATP, however it is a relatively slow process that occurs in the presence of oxygen.

As exercise intensity increases, a faster source of ATP is required and the importance of a process of glycolosis to energy production is greater. Glycolysis is where a molecule of glucose, a six carbon carbohydrate molecule, is split (lysed) in to two three carbon molecules called pyruvate. If there is sufficient oxygen within your muscles, then pyruvate can be used to produce energy. Some pyruvate is converted lactate during this process. If there is insufficient oxygen within your muscles then energy production can still continue but at a cost and more lactate is produced as a result; this is termed anaerobic metabolism. Lactate can be thought of as a buffer to buy the muscles extra time to produce the energy required for a given intensity. Lactate has several fates:

Lactate itself can be used for energy production directly
Lactate can be converted back into pyruvate in order to produce energy

If the demand for energy outweighs the muscles ability to produce it, then lactate levels can rise and spill over into the blood. Once in the blood, we can measure the level.

Lactate can then be transported to distant (non-working) muscles to be processed
Lactate can be converted back into glucose by the liver

Lactate is not responsible for you fatiguing during exercise. Fatigue is caused by an net acidic environment within your muscle cells amongst other factors. Lactate is a helpful molecule to allow you to exercise at a high intensity. It is constantly being produced and used by your body and does not hang around long after exercise. It is therefore a misnomer to consider a recovery session after a hard effort as "flushing out the lactate".

Resting levels of lactate are highly influenced by the amount of carbohydrate you have eaten. It is possible to significantly increase lactate after ingesting a high carbohydrate meal. This is the reason that we will ask you not to eat a heavy carbohydrate meal before your test and not to eat 2.5 hrs beforehand.