Whether you're a sprinter or an endurance runner, working on your lactate threshold has a ton of benefits. We explore the threshold run and explain how it could improve your training and racing. 

What is a threshold run?

In order to understand threshold running, you first need to know about heart rate training. Training according to heart rate is very important and can help to maximise your performance as well as prevent injury and over training. Your lactate threshold, or anaerobic threshold, will be when you start to move into heart rate zone 5 from zone 4. Zone 4 is roughly 80-90% of your maximum heart rate and once you reach the top end of this, you start to approach your lactate threshold.

Your lactate threshold is the point at which your body accumulates more lactic acid than it can efficiently get rid of. At this point of effort, you will start to fatigue rapidly and your legs may start to feel sore, heavy, or achy. In general, the fitter you are, the higher your lactate threshold will be, which means you will be able to run faster for longer. Someone who is less fit will hit their lactate threshold sooner, which is why they will find running even at a seemingly slow pace quite difficult.

A threshold or tempo run is a specific workout wherein you run at and above your lactate threshold in order to improve your fitness. The overall aim for training and racing is for your heart rate to remain lower even at a faster pace as this means you can sustain this faster pace for longer. 

How to find your lactate threshold

World renowned running coach Jack Daniels says, "Intensity of effort, not necessarily distance of running or racing, is what determines the degree of stress being put on the body’s systems." What this means is that your lactate threshold will depend completely on your current level of fitness and won't necessarily take into account how far or fast you are running.

As mentioned above, someone who is not very fit will hit their lactate threshold fairly quickly after starting to run and will need to maintain a very slow, almost walking pace, in order not to go over it. This is why heavy and/or unfit people will find running difficult and suffer from sore legs and joints, because their heart is having to work much harder even at a slower pace.

Fitter runners will find they can run much faster and for longer before their heart rate reaches zone 4 and will rarely even reach zone 5 unless racing a hard 5k or similar. 

There are various ways you can find and test your lactate threshold. Some modern smart watches or running watches will have a test feature built-in, such as the Garmin family of running watches, some of which allow you to do a guided test and will give you a result after about 20-30 minutes of guided heart rate running. There are other self-guided tests you can do such as the VDOT test which involves running 2 miles (3.2km) and then checking your results against the chart provided.

How often to do threshold runs

Running at a pace that takes you above your lactate threshold puts a great deal of stress on the body and as such you should only do a couple of threshold runs each week. If you are training primarily for endurance (marathon or ultra marathon races), 80% of your runs should be 'easy' and only 20% should be 'hard' or at threshold level. These are your 'quality' sessions and will help to increase your fitness, while the easy runs are there to increase your aerobic base and facilitate recovery.

If you do all of your runs at or above threshold, you will not be able to recover properly and will be at risk of burnout or over training, which can lead to mental health problems and physical injuries and illnesses. One of the reasons beginner runners often quit is because most of their runs will take them above their lactate threshold, because simply the act of running instead of walking will make their heart rate shoot up. They then find it very difficult to carry on and will want to quit. In this instance, doing a combination of running and walking to maintain a steady heart rate is best. 

It's hugely important not to let ego get in the way of your training. If a 10-minute mile takes you to your threshold, you should be doing most of your running and training at 11 or 12 minute miles. Even though this seems slow, it is what is right for you. If you are constantly pushing to run 9 or 8 minute miles because that's what other people do, you will soon get injured and mentally burnt out. 

The benefits of threshold and tempo runs

The great thing about the lactate threshold is that you can train it to get higher, meaning you will be able to run faster for longer. By doing threshold or tempo runs as part of your training, you will imprvoe your overall fitness, your VO2 max, and your lactate threshold. Your body will become more efficient at removing lactic acid and your endurance will improve. This is ideal for almost every type of runner, whether you're training for a 5k, 10k, half marathon, marathon, or ultra marathon.

The benefits of threshold training:

• Improve your VO2 Max
• Run faster for longer
• Increase your lactate threshold
• Reduce fatigue at slower paces
• Improved performance when racing
• Easier running during training
• Body becomes more efficient