Get Better Results with Lactate Threshold Testing



The most common and costly mistake that endurance athletes make in their training is getting caught in the “moderate-intensity rut,” where almost every workout is neither hard nor easy but somewhere in between. Research has shown that endurance athletes of all experience and ability levels get the best results when they spend about 80 percent of their training time at low intensity and the remainder at moderate to high intensity. But the vast majority of endurance athletes spend only 50 to 70 percent of their training time at low intensity and do most of the rest at moderate intensity.

Breaking out of the moderate-intensity rut will enable you to get better results from the same time commitment to training. This was shown in a 2014 study conducted by researchers at the University of Salzburg. Athletes who did about half of their training at low intensity and half at moderate intensity (as the typical endurance athlete does) improved their performance in time-to-exhaustion test by a modest 6.2 percent after nine weeks. But another group of athletes who did more training at low intensity and less at moderate intensity improved by an average of 17.4 percent in the same test.

The key to breaking out of the moderate-intensity rut is zone training, which involves dividing the intensity spectrum into distinct zones and targeting them in the ideal 80/20 balance in training. The only catch is that low, moderate, and high intensity aren’t the same for every athlete. In order for zone training to work, you need to identify zones that are based on your current fitness level.

Step one, then, is to assess your current fitness level. The best way to do this is with a lactate threshold (LT) test. The lactate threshold is the exercise intensity at which lactate, an intermediate product of aerobic metabolism, begins to accumulate rapidly in the blood. The fitter you are, the higher your heart rate, running pace, and cycling power will be at this threshold. This makes the lactate threshold an excellent marker of fitness and the perfect anchor for calculating personalized intensity zones.

Traditionally, LT testing is done in an exercise laboratory. The subject gets on a treadmill or stationary bike and exercises at incrementally increasing intensity until exhausted. At each step, a small blood sample is taken from a fingertip and its lactate concentration is measured. The results are then graphed and the graph is used to pinpoint the heart rate, running pace, and/or cycling power that corresponds to the lactate threshold. Intensity zones are prescribed as percentages of these numbers.

The disadvantages of traditional lactate threshold testing are accessibility and cost. Only a limited number of facilities provide the service, which is typically priced at $100 or more. That really starts to add up if you get tested every four to six weeks, as is recommended to keep your zones current.

A popular alternative to traditional lactate threshold testing is a field test. For example, a 30-minute time trial has been shown to estimate lactate threshold heart rate with reasonable accuracy. However, a 30-minute time-trial is essentially a 30-minute race. As such, it must be preceded by reduced training so the results aren’t affected by prior fatigue and it must also be followed by reduced training to allow for recovery. This makes the field-test method highly disruptive to the flow of training.

A better alternative to traditional lactate threshold testing is do-it-yourself lactate threshold with BSXInsight. It works exactly the same way as the laboratory version except that 1) the BSXInsight smartphone app guides you through the session instead of a human technician, 2) your blood lactate levels are measured indirectly with a sensor inserted in a sleeve worn on your lower leg instead of through blood samples, and 3) when you complete the workout, the app calculates your intensity zones automatically. Studies published in peer-reviewed scientific journals have found that the results of lactate threshold testing with BSXInsight are highly accurate. And although the tests do end in exhaustion, it’s really only the last couple of three-minute steps that are hard, so it doesn’t take long to recover.

Once you have your zones, breaking out of the moderate-intensity rut becomes a simple matter of following a training plan that features the right balance of intensities and monitoring your intensity throughout each workout to ensure you’re always in the right zone. Repeat the lactate threshold test every four to six weeks. This will not only keep your zones current but will supply real physiological proof that your training is working.

Learn more about how easy it is to use the BSXinsight sensor to improve and validate your training at

Thanks for visiting us and happy training.

Matt Fitzgerald
Nutritionist, Endurance Coach, and Author of How Bad Do You Want It and Racing Weight