What is threshold?
To start this conversation, we need to first point out that there are many different types of threshold and this is where the confusion begins. To give a few examples:
1. Lactate threshold
2. Aerobic / Anaerobic threshold
3. Ventilatory threshold
4. Functional threshold
There's lots of magazine articles which outline the benefits of calculating your threshold and how you can use it for training purposes, but many of them are poorly written and incorrect, so here's our low down:
You can complete a lactate threshold test by cycling or running, gradually increasing your pace and taking finger prick blood samples at regular intervals to measure lactate in the blood. As the exercise gets harder, the lactate levels will increase.
There are technically 2 lactate threshold points. The first one is very early in the test, when your lactate levels start to rise above their resting levels. In practical terms, if you can hold a full conversation whilst riding your bike, then suddenly you feel that your breathing rate rises slightly, this is your true 'lactate threshold'. This occurs very early and generally the heart rate at your lactate threshold will be the border of zone 1 and zone 2, so relatively comfortable.
As the test continues your breathing will get harder and harder and then you'll reach a second lactate threshold. Up until this time your lactate has been steadily rising, but this is follows by a sudden and sharp kick upwards. As the test continues, your lactate will continue to rise sharply and you're on borrowed time... you will be stopping soon as the lactate accumulates in your muscles. This second and sharp 'kick up' or 'deflection point' is what we tend to incorrectly refer to as 'lactate threshold'. This is the figure that most people have completed the test for, technically, this is the 'lactate turnpoint' or 'Onset of Blood Lactate Accumulation' (OBLA).
So why should I measure my lactate threshold / lactate turnpoint?
Well, your lactate threshold is a very good marker for many endurance events. Optimal Ironman bike pace tends to be very close to lactate threshold for many people (for training zones we use, it's the border of zone 1 / 2, but this is not the case for other calculated zones).
The lactate turnpoint is the measurement that most people really want to find out. When does my lactate start to rapidly accumulate, what's the running speed / heart rate / power output at that point? Many magazine articles generally state that your hard / sustained exercise pace coincides with lactate turnpoint, but in practical terms, we've found that not to be the case.
Let's give an example of a runner who completes a lactate turnpoint test and we calculate the heart rate at lactate turnpoint to be 165bpm. If we ask this runner what their heart rate generally is during a 5-10k race, they will generally give is a figure 5-8 beats higher than the lactate turnpoint. Initially this is confusing, as most people think that the heart rates will match. In terms of calculating heart rate training zones, we will therefore have to estimate by adding 5-8 beats to the lactate turnpoint, to predict heart rate for racing.
So why do a lactate threshold / lactate turnpoint test?
Lactate testing does provide some information, but it can also be relatively limited in it's use. One of the key things it does provide is a bench mark. If you repeat the test and the turnpoint occurs at a later speed or power output, then your fitness has improved. From a coaching perspective, if we want to use the test results to provide coaching advice and training zones, then it's not the best option for us to choose.
So what's the other options?
Aerobic/Anaerobic and Ventilatory thresholds can be calculated by measuring expired gases and breathing rates during testing. These tend to fall much more accurately as predictors or training intensities. Functional threshold, is a completely different concept. We'll discuss these topics over the next 2 weeks, so make sure you tune in!!
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