Lactate Inflection Point Test
More than just a sports screening – you do not need to be a professional athlete to get a lactate test done. Establishing your lactate threshold is a key part of personalizing your exercise routine to suit your body’s needs.
What is the purpose of a lactate test?
Studies conducted on athletes have shown a link between aerobic low-intensity cardio (Zone 2 training), athletic performance, and longevity; Understanding your heart rate zones can help you optimize your workout to achieve the desired health benefits while preventing unnecessary injury and burnout.
A lactate test measures the increase in blood lactate concentration during progressively intensive exercise to determine the lactate inflection point/lactate threshold; As workout intensity is measured using “zones” based on your lactate threshold heart rate, knowing your lactate threshold is vital for accurately setting your athletic training zones.
What to expect during the test
The Lactate Inflection Point Test is conducted on a treadmill and consists of five stages of increasing intensities that the patient will be asked to exercise at. Small blood samples will be taken from the patient at regular time intervals during the test until the test is completed.
- The purpose of taking the blood samples is to measure the lactate levels in the blood to determine when blood lactate accumulation begins.
- The first stage of the test will be conducted at a relatively low intensity to ensure that blood lactate concentration remains at resting levels during the start of the test, establishing the baseline level of blood lactate to compare against to determine the point where blood lactate accumulation commences.
- Test data will be analyzed to determine the patient’s anaerobic threshold/lactate threshold and corresponding lactate threshold heart rate (LTHR).
- The patient’s specific LTHR will then be used to establish their training zones.
The main purpose of the Lactate Inflection Point Test is to analyze lactate and heart rate data collected to establish your anaerobic threshold and training zones to aid you in improving/optimizing your workout or sports related performance.
Zone 2 exercise, health, and longevity
Zone 2 training is defined as low-intensity aerobic exercises, also known as cardio-respiratory exercises due to the body’s dependency on the aerobic energy-generating process to fuel itself, that can be sustained over a long period of time. Examples Zone 2 activities include:
- Brisk walking
- Long-distance running
Zone 2 training involves low to moderate levels of cardiovascular exertion (low to moderate heart rate) and power output, with the heart-rate zones controlling the type of “fuel” the body burns during exercise:
- At lower heart rates (low-intensity aerobic exercise) the body preferentially burns fat
- At higher heart rates (high-intensity anaerobic exercise) the body starts burning glycogen (stored glucose) from the muscles to supplement the fat
During anaerobic exercise, the body goes into an oxygen deficit and produces more lactate than the muscles can clear. This build-up of blood lactate is what causes fatigue and muscle soreness.
Although Zone 2 training may not burn as many calories per unit time as high-intensity training, low-intensity exercise allows the body to build its aerobic base (capacity to utilize oxygen to generate energy) and avoid acute muscle fatigue, while still burning a moderate amount of fat. Instead of pushing yourself harder, a lower intensity workout may be more beneficial for building your long-term endurance, performance power, and overall health.
Cardio-respiratory exercise has many benefits such as improving long term overall health and reducing the risk of diabetes and heart disease. To elaborate on the benefits to cardiovascular health, Zone 2 training helps to:
- Strengthens the heart – Cardio training helps to increase the heart’s chamber size, strengthen heart muscles, and increase the thickness of the left ventricle, resulting in a healthier and stronger heart that can pump blood more efficiently (higher blood ejection fraction) and sustain physical activity for longer periods of time. Strengthening the heart also helps build resistance against heart diseases.
- Improve the resting heart rate (RHR) – Continuous contraction of the heart muscles for sustained periods of time during cardio improves the blood flow and function of the heart, gradually improving the RHR.
- Improves oxygen capacity – Maximal oxygen uptake is an indicator of aerobic capacity. During cardio exercise, there is a raise in the heart rate and breathing rate, allowing the body to increase its capacity for expelling waste products and transporting more oxygen to the muscles.
Mitochondrial and metabolic health
Zone 2 training is known to improve metabolic health via increasing mitochondrial quantity, efficiency, and metabolic flexibility. Mitochondrial health is linked to preventing ailments such as immune system dysfunction, dementia, heart disease, type 2 diabetes, and certain types of cancer, making it key for maintaining long term health and promoting longevity.
- Mitochondria are organelles present in all cells of the human body and are responsible for the generation of chemical energy, in the form of adenosine triphosphate (ATP), needed to power cell activity. Mitochondria in the muscle cells are what provides the energy for the muscles to perform during physical activity.
Metabolic flexibility is the mitochondria’s ability to adapt to changes in metabolic demand and switch between “fuel” sources to generate energy; metabolic inflexibility being linked to insulin resistance, obesity, and type 2 diabetes. Zone 2 training is known to:
- Increases metabolic health – At lower heart rates, the body relies on aerobic metabolism via the mitochondria in cells to fuel the body during exercise. In response to the increased demand for aerobic metabolism, the body adapts by producing more mitochondria (mitochondrial biogenesis) and improving mitochondrial function/efficiency, enhancing the body’s ability to produce energy over time.
- Increase metabolic flexibility – Studies indicate that mitochondria in sedentary individuals exhibit an inability to utilize fat as a fuel source instead of glucose even at low heart rates (metabolic inflexibility). Zone 2 heart rate training allows the body to use fat as an energy source more efficiently and for a longer period of time, ensuring that glucose is only used as a fuel source during higher intensity exercise.
- Improves insulin sensitivity – Mitochondrial function is closely linked to insulin sensitivity, and exercise in all training zones enhances insulin sensitivity. However, due to Zone 2 exercise being more sustainable and less strenuous compared to intensive exercise, Zone 2 exercise can be done for much longer periods of time and at higher frequencies due to the low recovery time between workouts.
Improves aerobic capacity
VO2 max is maximum rate of oxygen the body is able to utilize during exercise, also known as maximal aerobic capacity (the ability of the body to make use of oxygen to generate ATP). Maximal oxygen consumption is indicative of cardiorespiratory fitness and endurance capacity and is linked to cardiac output and muscle mitochondrial efficiency.
Due to Zone 2 training’s ability to improve both cardiovascular and mitochondrial health, Zone 2 training improves the body’s VO2 max, making it beneficial for both long term health, as well as important for athletes who are looking to improve their endurance.
What is the lactate inflection point?
The lactate inflection point (LIP) is the exercise intensity upon which the rate of lactate production by the body equals to the rate of lactate removal. Your LIP, also known as your Functional Threshold Power (FTP), functional capacity, or lactate threshold, is defined as the maximum output intensity you can sustain (in terms of physical performance/exercise) over 45 to 60 minutes.
Lactate threshold heart rate and training zones
LIP varies between individuals, and your lactate threshold heart rate (LTHR) is your heart rate measured at the point when you reach your LIP. The intensity of your workout can be measured/split into five zones based on your lactate threshold heart rate (LTHR):
- Zone 1 – less than 85% of your LTHR
- Zone 2 – 85% to 89% of your LTHR
- Zone 3 – 90% to 94% of your LTHR
- Zone 4 – 95% to 99% of your LTHR
- Zone 5 – 100% to 106% of your LTHR
Note that exercising above your LIP leads to lactate accumulation in the muscles and, subsequently, fatigue. Additionally, the LIP of all individuals can be improved via training/exercise; the Lactate Inflection Point Test can thus also be used to measure improvement in an individual’s health.
Am I suitable for lactate testing?
All individuals are suitable for lactate testing but do note that for the test to be conducted, the individual must be able to run on a treadmill. The Lactate Inflection Point Test is recommended for individuals who:
- Participate in endurance sports and want to know their LIP to improve their performance.
- Are professional athletes.
- Want to determine their training zones to optimize their workout routines.
- Want to lose weight.
- Are on a “workout journey” and are seeking to track their health progress.
Before the Lactate Inflection Point Test, you will be asked to change into your workout/gym attire. Thus, please bring along a pair of running shoes and a set of clothing that you are comfortable exercising in.
Slight discomfort is expected when the blood sample is extracted during the test, but the discomfort experienced is usually not perceived as severe by most patients. The discomfort is comparable to a pin prick or an ant bite when the needle is inserted into the skin.
Results of the test will be ready between 2 weeks to a month after the test.