Updated: Nov 2
The lactate threshold test is a valuable tool for runners who want to focus on developing their fitness. It can help us to determine optimal training intensity in order to dial in our training and improve performance.
We often discuss heart rate zones a percentage of maximum heart rate. This number can be hard to determine and is generally fixed: you cannot train it to get higher. Many running watches use the age related formula (220-age) to work out the 5 heart rate training Zones. This number can be, for some, wildly inaccurate. In these cases, the heart rate Zones 1 to 5, will therefore be off target.
Unlike calculating Zones from the maximum heart rate number, it is possible to work them out by identifying your heart rate (in bpm) at lactate threshold, the boundary between Zones 4 and 5. What does this mean? As you work out your body produces lactate. The harder you work out, the more lactate it produces. The point at which the body begins to accumulate lactate faster than it can be cleared (indicating the transition from aerobic to anaerobic metabolism) is your lactate threshold. It is around point where you start to feel a noticeable burn in your muscles and a rapid increase in fatigue. Many new or inexperienced runners push themselves past this point; burning out, rather than completing their workout. Too hard, too fast, too soon.
Unlike maximum heart rate, lactate threshold is trainable – you can increase it with training. As you improve the clearance of lactate (raising the threshold) the top end of your Zone 4 heart rate gets higher, closing the gap with your maximum heart rate. You are fitter than before!
Please note that whilst I am a keen runner, I am not a running coach. If you have any concerns about your health or are under treatment, talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle.
How to Test Your Lactate Threshold
The lactate threshold test can be done in a running lab, however, a basic version of the lactate threshold test can be conducted during a run, with reasonable accuracy and without the need for specialised gear. You will need a heart rate monitor / GPS watch. Ideally with a chest strap for best results but my running watch seems to be accurate enough. Here's how you can perform a lactate threshold test:
Choose the Route
Choose a flat area to run, free from road crossings.
The test itself is 30 minutes, not including warm-up or cool-down.
Begin with a thorough warm-up to prepare your body for the test. Include 10 to 15 minutes of jogging with some strides.
After warming up you will run for 30 minutes. The important measurement is your average heart rate between minute 10 and minute 30. We will discuss how to use this number below.
This data can be extracted from your running watch. Alternatively, note the measurements at both time points, add them together and divide by 2.
The aim is to run at a pace that you can sustain without burning out, approaching an 8 out of 10 effort.
Running close to threshold is the intensity just before you feel like you can't sustain the pace for much longer.
If you are struggling to maintain the pace then you are running too hard.
Jog for another 10-15 minutes to cool down.
Use the Data; Analyse and Adjust
Once you have identified your lactate threshold heart rate, you can train to it rather than using max heart rate. Using the lactate threshold heart rate (LTHR, in bpm) from the test, your revised Zones are as follows:
Zone 1, Recovery runs, 65-85% LTHR
Zone 2, Easy Runs or Endurance Running, 85-90% LTHR
Zone 3, Hard endurance runs, 90-95% LTHR
Zone 4, Lactate threshold runs, 95-100% LTHR
Zone 5, Maximum Effort, VO2max runs, 100-110% LTHR
A reasonably hard 30 minute run requires a decent level of strength and fitness. If you are a newcomer to running, build up your fitness before trying this. There is no pressing reason to do this test unless you are already running regularly and want to take your running to the next level, perhaps as part of your journey to increasing distance and greater fitness.
Many people are likely to run too hard when they first try the test. The test is not to run as hard as possible, it is to run comfortably hard - at a sustainable pace that you could hold for up to 40 minutes or even, for fitter people, an hour. Use the initial 10 minutes to build up to the the correct pace.
I calculated my lactate threshold to be 150bpm. Therefore, I set my Zone 4 runs (by manual input into my phone/watch) at 143 to 150bpm.
Soon after that initial test I completed a heart rate max test, with an all-out 10 out of 10 effort. This gave me a heart rate max of 167bpm. Working out my zones based on percentages of heart rate max, this put my Zone 5 (>90% max heart rate) at 150bpm and higher, tallying nicely with the results of my lactate threshold test.
Improve Lactate Threshold: Tempo Running
Training at or just below your lactate threshold can significantly enhance your endurance and speed over time. For this you need to do tempo runs (20 to 30 minutes continuous effort) or cruise intervals at or around threshold heart rate.
Cruise intervals are sets of shorter tempo runs, say 10 minutes per set, with a couple of minutes rest between each. These allow you to run for a total 30 minutes at threshold pace without the demands placed on the body by a single, hard paced run.
Try a tempo workout once per week, see how you feel. If you are an older runner – listen to your body and be sure to recover properly before the next hard run.
As your improve your body's ability to clear lactate from your blood, your lactate threshold rises. You will need to retest in order to measure (see) the improvement. You should notice that for a set distance run, say a 10km, your time will decrease as your fitness improves.
Remember, while this lactate threshold test doesn't require equipment, it relies on your body's perception of effort and fatigue. Regularly conducting this test can help you gauge your progress and optimise your training regimen for better running performance. Plus it feels great to be running at threshold!
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