This sponsored post is produced by Garmin.

Running holds a special place in many people’s hearts, in part because of the emotional toughness it requires (and inspires). Whether you’re training for a marathon or doing it just for pure enjoyment, managing expectations, enthusiasm, and determination is half the battle. However, to achieve athletic and personal goals, you also must also monitor your body.

Three key physiological metrics that runners should measure regularly are stress score, performance condition and lactate threshold. Together, these measurements can shed light on your capacity and performance– whether the end game is training for a race or generally improving your fitness level. They also give you the information you need to stay within a healthy and efficient performance range.

Enter technology: with the advances in sport watches, and by following the guidelines below, runners can learn how to measure these three essential thresholds to help maximize form and fitness — and avoid burning out.

1. Stress Score

Stress score measures heart rate variability to assess your physical stress levels. This is a great indicator of a runner’s long-term tolerance to– and targets for– training load. It can also be used to accurately determine the ideal length, intensity and scheduling of runs, taking into account adequate recovery times and the physiological costs of running.

With a sport training watch like the fēnix 3, runners can analyze their heart rate variability during a three-minute standing test to determine the overall stress score. Stress scores can range from 1 to 100, with 1 being a very low stress state and 100 being a very high stress state. Knowing stress scores can help decide if the body is ready for a tough training run or some restorative yoga.

To get the most accurate stress score measurement, it’s best to measure it at approximately the same time and under the same conditions every day. This helps runners see the trend line of their stress scores across time so they can make better training decisions.

To make this process as simple as possible, you want to make sure you’re leveraging optimal heart rate technology you no longer need to wear a cumbersome chest strap while they train.

2. Performance Condition

Just like an individual’s energy and mood differs from day to day, so does the capacity to take on physically intense exercises. That’s why measuring performance condition allows runners to determine their readiness for a day’s workout or race, relative to their average baseline.

Performance condition can be determined within the first 6 to 20 minutes of a run, enabling runners to make adjustments to their workouts if needed. The fēnix 3, for example, calculates this using heart rate, heart rate variability, and pace– the three indicators of physiological readiness to take on aerobic activity.

Whereas one day a runner’s performance condition may indicate it’s a great time for a fast, competitive run, another day might show the body can only tolerate a shorter jog.

3. Lactate Threshold

Lactate threshold is the third key to the kingdom when it comes to avoiding burnout. Many runners can sense their bodies fatiguing more rapidly some days than others, but it’s important to consistently monitor lactate threshold, because it can give a much more accurate picture of a runner’s condition.

Essentially, lactate threshold estimates the level of effort at which fatigue sets in based on a runner’s heart rate and pace. It’s the point at which lactic acid is being created faster than it can be used by the body. When a runner is operating at or below their lactate threshold, any lactic acid produced by the muscles is removed by the body without building up, allowing the runner to maintain that level of output indefinitely. Operating above the lactate threshold means the liver isn’t able to metabolize lactic acid fast enough, leading to fatigue, and over time, burnout. This can be monitored during a run using a GPS training watch that measures heart rate variability.

It’s a good idea to measure this systematically because it can vary between individuals and can be increased with training. For experienced runners, the lactate threshold occurs at approximately 90 percent of your maximum heart rate and between a 10k and half marathon race pace. For average runners, the lactate threshold usually occurs well below 90 percent of your maximum heart rate. Knowing this can help you determine how hard to train and when to push (or not) during a race.

Training Smarter

There are many — perhaps infinite– factors that impact the overall performance of a runner. Alongside the three factors listed above, runners should also pay attention to their sleeping patterns, nutrition, and environmental stressors. When kept in balance, these lifestyle factors can improve many of the metrics above, ensuring optimal performance and continuous improvement. At the end of the day, the very best way for you to avoid burnout is to regularly keep in check with your body’s physiological signals using finely-tuned technology– coupled, of course, with valuable human intuition.

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