For example, does a high Max HR mean that an athlete can push harder for longer than a similarly-trained athlete with a lower Max HR? Having a high or low LTHR does not directly relate to athletic performance; instead, HR values tend to relate to your previous athletic experience and your individual physiology. LTHR is also less age-specific than people think and are quite individually determined as well.
What Is LTHR?
In simplest terms, LTHR is the maximum HR you can sustain over a longer period of time – typically measured as a 1,500m swim, or 40k TT on the bike, or a 10k run. The fitter and the more experienced an athlete is, the longer he or she can sustain effort at LTHR.
Efforts above threshold are extremely intense and, thus, cannot be sustained for nearly as long. Glycogen (blood sugar) gets depleted at a much faster rate above LTHR, for example, while completing VO2max effort intervals. I refer to completing efforts above LTHR as “lighting the fuse”, because once you light the fuse, it burns and you only have a limited amount of time before the fuse burns out and you explode. Thus, these more intense efforts can only last a few minutes at the most before recovery is needed. On the flip side, efforts below and up to your threshold can be sustained for a much longer duration.
High or Low LTHR
HR values are very individual. Some athletes have a higher LTHR, while others have a lower threshold. These numbers can vary at any age. For example, a Masters athlete can have a LTHR in the 180’s while an athlete half his age can have the same. It is typical for younger athletes to have higher LTHR values, such as in the 180’s and higher. It is also common to see athletes in their 30s and 40s test out at lower LTHR values. Again, this is just the trend; it is possible that a higher or lower LTHR can exist at any age.
Multiple factor such as cardiac output, pulmonary function, strength, VO2max and the overall size of your body all factor into how fast your heart needs to beat to deliver oxygen to the working muscles. Remember, O2-rich blood is the fuel of the working muscles so the harder you work, the more O2 your muscles need to function properly. While there are many factors that go into determining LTHR, one of the main factors may be the heart itself, specifically the left ventricle.
During diastole (the relax stage), the left ventricle fills with oxygenated blood, and then, during systole, it contracts and pumps the oxygenated blood through the aorta and into the body. The size and strength of the left ventricle will determine how much volume of blood can be delivered with each beat. Life long athletes tend to have higher Max HR and LTHR values. This is because the heart is more adaptable to change at a younger age. As we age, the heart becomes less adaptable and more “fixed.” While not definitive, it is reasonable to say that Masters athletes with higher HR values probably established those values at much younger ages and then carried them forward through their lives as they continued to compete while growing up.
Those who are new to endurance training, at any age, may experience a change at LTHR after initial tests. This is common to see after initial gains in strength or cardiovascular fitness. Another reason for this is simply learning how to test as newer athletes learn the correlation between RPE (rate of perceived effort), HR and duration of effort. It is important for all newcomers to an endurance sport, as well as experienced athletes coming off an extended break, to test fairly often to confirm (or reestablish) threshold ranges.
Other variables which impact LTHR include medications you might be on as well as fatigue brought about by training as well as emotional and mental stressors. HR can also be suppressed due to muscle/overall fatigue. Carrying too much fatigue into a threshold test will result in less than stellar results and not provide you with an accurate representation of your fitness. Hence, tests are typically conducted at the end of recovery weeks.
Lastly, whether indoors or outdoors, pick a consistent venue for your tests, preferably a long uninterrupted hill for the bike and a running track for the run. For the swim, you will simply want to make sure you pick a day to test when you know the swim lanes will not be overrun with kids or water aerobic classes. Indoors, a stationary bike trainer or treadmill is convenient but just make sure you “stay in touch” with these training tools as the weather warms up, otherwise your results could get skewed a little bit from the lack of familiarity if you haven’t trained inside for a couple months.
HR values are different from one person to the next. The bigger your HR Range, one would think that would allow an athlete to push harder for longer. Does a HR of 155, for example, feel more comfortable to an athlete with a Max HR of 200 than it does to one with a Max HR of 185? It is not a simple math equation to answer this, as hopefully you’ve learned from this article. The better trained you are to handle efforts at or around your LTHR, the longer you will be able to hold a faster effort. And, the faster you will be able to race.