What is blood lactate?
Lactate or ‘lactic acid’ often has a bad press and considered to be bad for the body by increasing the acidity of the blood and therefore causing fatigue. It tends to be anecdotally associated with the intense ‘burn’ or pain in the legs and soreness in the days following exercise.
However, these are just myths and lactate actually plays a very important role in prolonging endurance performance by ‘consuming’ hydrogen ions which are the real culprit for acidifying the blood. So rather than cause fatigue, lactate does its best to prevent fatigue!
Lactate is actually being produced by our bodies at all times. During rest or low intensity exercise, the rate of lactate production is being balanced by its use as an aerobic fuel source. However, as we begin to exercise at a higher intensity (i.e. running up a hill) there is an increased energy demand which is met by the breakdown of carbohydrate. If there is insufficient oxygen, the increasing rate of lactate production will result in a build-up of hydrogen in the blood. At this first threshold point, training could, in theory, continue at the same intensity for a prolonged period of time provided you were fuelled and hydrated.
The problems occur when exercise intensity continues to increase and the increasing amount of hydrogen in the blood is then unable to be removed by lactate. We reach a tipping point which is the second lactate threshold. It is usually determined by a sudden and dramatic increase in blood lactate and represents the upper limit of lactate production and clearance. Fatigue will set in very quickly if exercise continues at the same, or at an increasing intensity.
Why measure blood lactate and not VO2max?
1) Helps monitor/modify training
Although VO2max is often used for assessing endurance capability, the lactate thresholds are seen as a good predictor of performance particularly amongst a group of athletes with similar VO2max values. The blood lactate test are sub-maximal and so they tend to less disruptive to your normal training because the recovery period is a lot quicker.
2) Good indicator of training adaptations
The whole idea of training is to shift your lactate thresholds so they occur at a higher work rate. Key adaptations from aerobic training allow for less lactate to be produced within the muscles, and more lactate to be cleared by different organs, when performing at a given work rate around the first lactate threshold. Examples of the adaptations to your body would be an enhanced muscular ability to mobilise fat for energy production and greater oxygen delivery to the muscles thanks to an increased network of capillaries.
3) Correlates well with endurance performance
Studies have shown that a rightward shift in the lactate thresholds is a better indication of endurance performance than maximal aerobic capacity.
4) Helps identify optimal training status
You will be able to structure your training around clear training zones which helps maximise training and mitigate possible overtraining.
What does the test involve?
You will be asked to wear a heart rate monitor throughout the test.
Resting blood lactate and heart rate will be taken before your begin the test. The capillary blood lactate sample is taken by making a small puncture in your finger with a lancet (similar to the type used by diabetics). A small amount of blood is then transferred to the portable analyser via a test strip.
The test will commence at a relatively easy work rate which will be used as your warm-up.
Each test stage is 3 minutes long.
At the end of each 3 minute stage, your heart rate and subjective measure of effort is taken. A blood lactate sample is also taken.
The treadmill speed or power output is then increased and you commence the next 3 minute stage.
This process is repeated until the second lactate threshold point has been reached or you are no longer able to maintain the current work rate.
After the test, you will be provided with a full report detailing the training zones and bespoke training paces.