What is lactate and why should you care?
In one of our last post CLICK HERE we started to discuss some basic sport science. To recap:
Lactate is the end product of glucose metabolism within our fast twitch muscle fibers. The more work our muscles perform (i.e. the faster you run, swim, bike), the more lactate and acid is produced through glycolysis, which ultimately leads to changing the cellular environment and causing what we know as fatigue. In fact, the lactate itself does not cause fatigue. The fatigue comes from the acid build up. Lactate is actually transported from muscle fibers to the liver leading to production of more “fuel” in the form of glycogen (clumps of glucose). Blood lactate levels of approximately 1mM to 2 mM at rest or during easy exercise are typical. At that level, the body is able to utilise glucose and lactate as energy sources for many hours. For most under trained people, this is walking pace.
However, muscles also have a finite capacity to utilise lactate and remove lactate from the muscle fiber. During high intensity exercise, increasing glucose metabolism increases lactate production. Lactate therefore begins to accumulate in the muscle fibres and eventually in the bloodstream. Training above this point causes the body to quickly fatigue (within 8-12 minutes). Training below this point (anaerobic threshold) is far more sustainable (30-60 minutes), depending on the ability of the athlete.
With training, the body is able to increase its utilisation of lactate and thus maintain muscle function for longer periods before lactate starts to accumulate in the muscles and subsequently becomes elevated in the blood.
Increased endurance is therefore associated with an increased lactate threshold. The aerobic/lactate threshold definition is the first increase in blood lactate above the resting level, which is typically between 1 and 2 mM in healthy subjects. The second lactate threshold point occurs around 4mM and marks the point which the runner can only sustain for about 10 minutes as described earlier.
Why is this important?
If you are an endurance athlete, you should be measuring performance in order to determine if your training plan is working, and whether you’re improving. There are several ways including racing, but if your race is over an hour long, you may not be racing often. This is where sub threshold testing can play a role in measuring progress.
The only way to truly know these points is to perform a lactate threshold/subthreshold exercise test!
We will soon be performing the test in the clinic, so stay tuned!