What is Lactate?
Lactate is a bi-product constantly produced in the body during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal which is governed by a number of factors. The concentration of blood lactate is usually 1-2 mmol/L at rest, but can rise to greater than 20 mmol/L during intense exertion. Blood lactate levels essentially serve as an indirect marker for biochemical events such as fatigue within exercising muscle.
Whay and how are lactate levels assessed?
Lactate levels are assessed for several different reasons such as determining sustainable threshold, peak, tolerance and clearance values. The reason to assess is relative to the desired performance outcome and the lactate levels are often related to speed, power or heart rate. Sustainable threshold values are the most common assessment outcome and are used by endurance athletes primarily. To determine sustainable lactate levels, subjects perform exercise at incremental loads, for 12 to 15 minutes, while having blood drawn in droplets either from a finger or earlobe. A stationary bicycle, a personalized bike and Computrainer or a treadmill are typically used. The test starts with an easy-moderate work load which is maintained for a 3-5 minutes. The load is increased gradually every 3-5 minutes until reaching 1 testing stage above when lactate levels reach 4 mmol/L blood. This is done by increasing the cycling resistance or the speed and/or grade of the treadmill. The lactate levels, heart rate, speed and/or watts are measured at the lactate threshold and maximal load.
The most significant value obtained from this assessment is the Onset of Blood Lactate Accumulation (OBLA) value. OBLA is the point at which lactate begins to accumulate in the blood at an accelerated rate. This is the point at which the body can sustain a particular effort for 20-60 minutes on average and can be a good guide to one’s performance abilities. At this point, HR, speed and/or watts are also calculated and it is from this data that training parameters can be developed.
To determine peak, tolerated or clearance lactate levels involves other maximal effort tests and will not be reviewed in this document.
How are results incorporated into training?
Lactate values cannot be used in every-day training but follow-up lactate values can be used as a measure of progress. However, since heart rate, speed and/or power is typically measured during a lactate test, these training parameters can then applied to everyday training. Other information such as lactate endurance levels (lactate values at a given heart rate or power output) can also be tested and compared to subsequent tests.
One of the better ways to incorporate this information into training is to use the OBLA data to establish field time trail parameters. Once those are established the time trails can be re-assessed periodically to determine improvements in the field with lab reassessments used to establish new training parameters.
How does training affect lactate levels?
After training you can perform at a higher rate of work without raising your blood lactate levels above initially tested levels. In other words, blood lactate concentrations at various training intensities are lower and your speed or power at OBLA is faster or greater respectively. This is in part due to the fact that, training results in a decrease in lactate production and an increase of lactate re-uptake within the body.
How often an OBLA value at a certain power or speed will change significantly, will depend in part on an individual's training history and habits - for example, someone who is just beginning in and/or returning to cycling or running for instance, may see large and rapid changes in their threshold power or speed, whereas an experienced rider or runner who has been training for many years and/or an athlete who maintains a high level of conditioning year round will probably experience much less variation.
Health and performance considerations
There is limited research regarding health status and lactate. McArdle’s disease is a condition involving lactate production and the individuals who suffer from this condition cannot produce lactate during exercise. In general, a high lactate level also represents a high H+ concentration, which can lead to metabolic acidosis, a serious condition and is to be avoided as all costs. Metabolic acidosis is typically is seen in conditions such as in the kidney and chronic renal failure.