Lactate Threshold - what is it, and why do I care?

With summer approaching, long distance events like triathlons, marathons, and good old fashioned weekend warrior outings are coming up. That means it’s time to put on those running shoes, jump on your bikes, or go for a swim and start training. But what’s this you keep hearing about the lactate threshold from your tri-geek buddies?

The basic concepts surrounding the lactate threshold hold true for any bout of exercise no matter the length, but the goal of most of these types of races is to be able to continue for long periods without rest in order to post a decent time. For short bouts of exercise, the lactate threshold isn’t really an issue, but as the duration increases, so does the importance of this often misunderstood concept.

The lactate threshold is the point during exercise at which lactate (a by-product of physical exertion) builds up in the blood stream faster than the body can remove it. If a person working above their lactate threshold continues with their exercise bout, the concentration of lactic acid in the blood increases. This can contribute to a state called lactic acidosis, in which general fatigue and compromised muscular contraction make physical activity progressively more difficult to maintain.

Lactate threshold can be expressed as a percentage of an athlete’s maximum oxygen uptake ability (a complicated and expensive measurement), or estimated as a threshold heart rate. Below this athlete-specific “line in the sand”, lactate can be readily eliminated while, above it, lactate will accumulate.

Ideally, throughout a long distance event like a marathon the participant will stay under this heart rate until the last portion of the race where the athlete can afford to build up lactic acid.

Determining your lactate threshold can be done in a lab (if you have endless time and money) or estimated on your own with only a heart rate monitor and your cardio equipment of choice. It is usually safer to do this test on a stationary piece of equipment (i.e. a treadmill or stationary bike instead of road running or biking).

• To perform the test a 30-minute trial at a high sustained pace will be completed.
• To begin, warm up sufficiently for 10-15 minutes with light activity like a walk and gentle stretch (this time does not count towards your 30 minutes).
• Begin your exercise bout and work up to your peak sustained intensity within the first 10 minutes. This would be the maximum intensity/speed that you estimate you can sustain for the final 20 minutes.
• Record your heart rate each minute for the last 20 minutes (some heart rate monitors can be set to do this automatically, or you can have a friend or your trainer help you)
• When finished, calculate your average heart rate over the last 20 minutes.
• This figure is your estimated lactate threshold heart rate.
• For a more accurate determination, complete the test a few times and take the average; this will allow you to more precisely tune your estimate of your peak sustained intensity when choosing your speed for the last 20 minutes.

It would be beneficial to perform the test in the style of your planned event (e.g. for a marathon perform the test on a treadmill). Lactate threshold is not a set figure; you may want to test repeatedly over time so you always have the most accurate estimation possible.

Increasing your lactate threshold is also possible through various training methods, which will allow you to increase your peak sustained intensity/speed, and finish your events faster! Two examples…

 Interval training:

• Perform three to five 10 minute high intensity intervals at 95%-105% of your lactate threshold heart rate with 3 minutes of active rest (slow walking) between intervals. When finished, do an active cool down of about 10 minutes of slow walking and a stretch.

 Continuous training:

• Perform one 20-30 minute high intensity bout at 95%-105% of your lactate threshold heart rate. When finished, do an active cool down of about 10 minutes of slow walking and a stretch.

No matter your chosen event or training method, be sure to work within your own limitations. The lactate threshold can only be pushed so far. Now get out there and be faster and acidosis free!