While the Gas Exchange Test offered by many physiology labs, if administered correctly, can be held up as the gold standard for determining your metabolic response to exercise, a simpler and cheaper alternative exists. Many labs offer lactate tests and lots of coaches who have their own meter can conduct this test as well. As you saw last week, we recently connected Morgan Sjogren with a coach in her area who did this simple test on a hill.
Measuring the concentration of lactate in the blood during a graded (stepped) exercise test has been a standby for coaches and athletes ever since portable lactate analyzers hit the market 15 years ago. These hand held devices are the same size and work on similar principles to the much more common glucose meters used by diabetics. A tiny blood (almost painless) sample is collected on a test strip that is inserted into the meter. Depending on the meter, the result will be displayed in 10 to 60 seconds.
By gradually increasing the intensity of the exercise and recording the heart rate when the sample is taken you can end up with a lactate versus heart rate graph. What’s this tell you?
Since lactate is a product of glycolytic metabolism and the rate of glycolytic metabolism increases with intensity of exercise, lactate can be used as a proxy for intensity. When the lactate concentration in the blood rises 1 mmol/L above the base rate or when the lactate concentration reaches 2 mmol/L the aerobic threshold has been reached. We’ve spent considerable time and ink talking about why all endurance athletes need to know where this point occurs for them. In essence it defines the upper limit for aerobic base training.
These tests are often given to help athletes determine the ANaerobic or lactate threshold. The is the endurance limit, a pace you can sustain for around 45 minutes. This is close to 10km running race-pace for a fairly fit athlete. In other words; IT IS HARD!. And it will help you in your training to know this too. But, you really want to know the lower or AEROBIC threshold. The lab tech is likely to ask: “Why do you want to know that?” Tell him you want to define your Zone 2 intensity. If you have an option, we’d suggest doing this test fasted or at least don’t eat a high carb meal with a couple of hours. Also make every effort get 15 minute easy warm up before beginning the test.
No fancy lab or treadmill necessary for this, only a moderate hill you can run and walk up, a lactate meter, and a buddy to take the blood samples and record the data. You can self-administer this test but its easier with a partner. After your 15 minute warm at quite low intensity begin by walking fast up the hill for 3 minutes. At the top of the hill your partner will take the blood sample and you will walk back down and repeat. Start with a pace that puts your heart rate in the 110-120 range. Each succeeding stage should be done with a heart rate about 7-10 beats higher. It is important to hold the HR as steady as possible through out each stage. If you get a bad reading you should repeat that stage before moving to the next higher HR. Follow the above recommendations for eating and warm up.
In the end you should end up with something that looks like this if you are fit:
And this is what your graph will look like if you need to build up your aerobic capacity:
Some guidelines for DIY testing:
- For about the cost of 2 treadmill tests you can own your own meter. You won’t need it often but sharing it with other athletes who want to test for progress every couple of months is an idea worth considering.
- Lactate.com is currently the only source we know of in the US selling meters. They sell the Lactate Plus, which we use, and the Lactate Scout along with the test strips needed. The old Lactate Pro which we also use and like a lot has been discontinued. Both meters and test strips are becoming harder to find.
- It is frustratingly common to get error readings when you test a sweat contaminated sample. This is especially true with the Lactate Plus which uses a very small blood sample. Wipe the first drop of blood away with alcohol and then dry the area with a dry paper towel and test the second drop to lessen the chance of errors.
- Climbers often have very calloused finger tips so can be hard to get a sample from. We like to use ear lobes.
Happy testing, happy training!