How to Calculate Your Lactate Threshold

Learning your blood lactate level is relatively easy, and can really help you hone in your training.

Danielle Kosecki |

Learning your blood lactate level is relatively easy, and can really help you hone in your training. – By Danielle Kosecki

Chances are you’ve heard cyclists say they’re “training at ninety per cent of max heart rate,” or some similar figure. Sounds kind of impressive, doesn’t it? After all, athletes like to do everything to the max.Although maximum heart rate is a useful benchmark for determining how intense your training should be, it isn’t as effective as lactate threshold, the border between high- and low-intensity work, or roughly the effort experienced in a flat-out, 30-minute time trial. Lactate threshold is a better baseline than maximum heart rate for determining training zones, because two cyclists with the same maximum heart rate may have widely varying lactate thresholds due to genetic or training differences. Sedentary people can have lactate thresholds as low as 50 per cent of maximum heart rate, while elite athletes can maintain 90 to 95 per cent for an hour.Once you determine your individual lactate threshold, every workout can be based on a reference point that yields safe, repeatable, focused bicycling training that’s tailored to your fitness level at that moment. Fortunately, it isn’t hard to determine your lactate threshold.

How to Determine Your Blood Lactate Level

1. In the Lab

Many coaches and fitness labs offer lactate threshold tests. The test takes 30 to 40 minutes. While wearing a heart rate strap, you’ll start pedaling easily on a stationary bike set up for a specific power output. Every few minutes, the resistance increases until you can no longer keep going. At each increase, the technician pricks your finger for a drop of blood, which a machine then analyses for lactate, or lactic acid—the prime marker of muscular fatigue. All the data is logged via a desktop computer, which plots the graph of your results.

2. The 30-Minute Time Trial

Most cyclists, however, don’t have access to lab facilities to determine their lactate threshold. You can still find yours, though, with a simple 30-minute time trial that’s best done outdoors on a flat road. The average heart rate you can maintain for the ride – about 16km – is a good working approximation of your lactate threshold.

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3. An Indoor Test at Home

You can also find your lactate threshold at home with this indoor workout test. First, calculate a range from 80 to 90 per cent of your maximum heart rate. So for instance, if your maximum heart rate is 180 bpm, 80 per cent is 144 bpm and 90 per cent is 162. Most cyclists’ lactate threshold will be somewhere between these two numbers, depending on conditioning.

Once you’ve estimated your lactate threshold range, perform an indoor test to find what resistance or gear keeps you in your lactate threshold range while pedaling a constant 90 rpm. (You’ll need a cadence function on your power meter or bike computer, your heart rate monitor, and a friend.) Warm up well, then maintain 90 rpm in your chosen gear. Pedal for 15 minutes and have your helper jot down your heart rate each minute. If you’ve chosen a gear that’s too high (your heart rate soars and you gasp for breath), stop, decrease gearing, and do another test on a different day using a lower gear.

When you complete a test during which you are pedaling at the highest gear that allows your heart rate to stay fairly level over the 15-minute test, note that heart rate – it will be very close to your lactate threshold. But remember not to go too easy: you are trying to find the highest heart rate you can maintain for 15 minutes, so your breathing should become moderately labored.

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Now – and this is important – when you’ve found your final number, subtract two to five beats for your final figure. Why? Because most cyclists overestimate their lactate threshold, resulting in training ranges that are too high. Test your estimate on rides. How does this intensity feel? Can you maintain your goal heart rate? Remember that this isn’t a precise science; you’re merely trying to find a good number upon which to base your training plan. By following these steps, riders can get an accurate home measure of their lactate threshold within a couple of beats per minute.

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