Heart Rate and It's Role in Motocross

So first off I'm back to blogging on here and taking questions. I have been on a bit of a hiatus as those of you who follow and are close to me know that I have been doing some work this year for the Portland Timbers professional soccer team, with strength ad conditioning and data analytic's. So without further ado...

Heart rate in the world of motocross is a very tricky and complex thing. It requires that you have some amount of understanding of the topic before you can fully comprehend why I make my argument. This is because your heart rate can respond to different things and deceive us with this simplistic number that we've all seen.

Physiology of Heart Rate
Your heart rate is the result of your heart beating and pumping blood through your system to transport nutrients, move oxygen and remove waste(CO2). During exercise at low intensities we have an aerobic response where our body is using oxygen as its primary energy source to fuel work and we tend to see heart rates generally around 55-80% of your heart rate max. Your heart is beating at that pace primarily to expel the waste and bi-product of activity and not so much to take in and move oxygen, although this is a vital component.

Then if your working very hard like intense sprinting or high speed middle distance running (that term is used broadly and not based on track specific competition distances) then you are most likely using your anaerobic energy source, depending on how fit you are. This type of energy is where your body uses stored carbohydrates to fuel activity, with an obvious limited supply. But the amount of bi-product produced and the concentration of it tends to be higher, causing a higher heart rate response to more efficiently pump that waste out of the body.

This doesn't inherently mean that your heart rate is going to get up to 90% of its max for sure. You could do a single sprint and potentially only hit 80% of your heart rate max. This is because there is an accumulation effect that is required in most cases to elevate your heart rate to those levels. One sprint wont do the trick, something more like 8-10 and now you'll be getting your heart rate there. So already we have some complexities to how the heart rate responds to activity.

Another way your heart rate can get very high, is something that all of us are most likely addicted to if you're reading this post....Adrenaline! We all love motocross because of how cool it is but, also because of the adrenaline and that high you get when you're riding. This chemical in our body is extremely powerful and is a natural response to our natural animal instincts, your response to fight or flight. When your body senses danger, it responds in a manner to prepare yourself to either run at incredibly high intensities or to fight with ferocity. The huge rush of adrenaline makes your heart pound and gives you the ability to do things that normally you wouldn't. Now lets get into some more of the complexities of all of this.

Mechanisms/Complexities of Heart Rate
The more fit you are, the more work you are able to do at lower heart rates. Additionally, you can sustain and use more aerobic energy at higher levels of your max heart rate (this is only occurs at a small increase of your % max HR but it is possible). Your anaerobic system can get more efficient and recover faster allowing you to repeat similar high intensity efforts for a greater amount of time. In addition, the waste removal process of exercise bi-products by the Lactate shuttle system, can become more efficient and improve high intensity repeated efforts.

When lifting weights you can be working the anaerobic energy system with the weights however, your heart rate may be in the general categories of aerobic level heart rates. I don't know many people that do a set of bench and their heart rate gets to 90% + of their heart rate max. Not that it isn't possible, but it's just not the most common response. Considering though, I doubt most anyone would argue that if my max bench is 225 and I'm pushing 205 (91% 1RM) for 5 that I'm working on my aerobic capacity, even though my heart rate only hits 152 (74% of my max HR). The last complexity is that adrenaline like any dopamine, can produce a natural tolerance depending on frequency of exposure. Also it is highly reactionary to multiple stimuli and it's not just 1 thing that will ever cause it to rise.

Your training itself can lead to different responses and reactions during competition. You can train and specialize your body in aerobic capacity (endurance), anaerobic (fixed amount of endurance + strength and power) or anaerobic alactate (strength and power only). If you are more aerobic, your HR may stay lower but you could fatigue faster from the intensity of each effort on the back end of it. Then causing a quick rise in HR because of insufficient ability to recover from these other energy systems required for high intensity effort. You could be highly anaerobic and do very well with motocross but just have high heart rates from the adrenaline + work. Last you could be an anaerobic alactate athlete who has great strength but fatigues quickly because you cant recover from repeated efforts in a short duration of time. This also would cause your heart rate to spike as it suffers from inability to expel waste efficiently.

What All of This Means
I've had guys go up to the line just for practice and their heart rate is in the low 180's from the adrenaline alone. They also weren't horribly unfit individuals. Now you take that and you go out on the track and you do a series of high intensity repeated efforts that strongly mimic weight lifting in their intensity and demand of your muscles. You can see how these two things put together add up really quick to a high heart rate. But how do you know what percent of the work you're doing is actually a direct response to the amount of work you are doing on the bike? Is motocross really an endurance sport?

I will say that by classical definitions of endurance sports, motocross most certainly does not fit. By the classic definitions you would expect sports like marathons, ultra-marathons, triathlons, adventure racing (off road running), other running sports similar and endurance racing (12 hour + races). These sports more directly represent the endurance notion, more particularly the running based sports. This is one of the classic requisites of an endurance sport, running at sub-maximal efforts for long duration's of time. The efforts in these sports are definitely not full out effort for the entire duration. So is motocross an Endurance sport?

Technically speaking, no motocross is not an endurance sport. I think with further research over the years we will show definitively that it is an anaerobic based sport and not aerobic by endurance standards. Nothing about motocross is sub-maximal. It is anaerobic, strength endurance/power endurance based sport. The aura of these insane heart rates showing it's an endurance sport and that it is the hardest sport in the world is very inaccurate. The high heart rates even as a result of adrenaline can cause high levels of fatigue and make it even harder to perform but, the reality is that it is not derived from an aerobic specific response (sub-maximal repeated efforts for extended periods of time).

No one will ever prove that a single sport is the most physically demanding sport in the world. Also people are limited to and make these claims based on the most popular and broadsports they can think of. People always seem to forget sports, like Iron Man triathlons (2.5 mile swim, 112 mile bike ride and a full marathon after), decathlons (arguably the most overall fit/athletic individuals on the planet) and some adventure races spanning entire continents. There is even a race, that I cant remember the name where a team of people compete, they have to swim an insane amount of miles, run 100's of miles, climb mountains, kyak rivers and do this all in a single event.

So in closing, is motocross extremely difficult? YES! Is motocross the worlds more physically demanding sport? No! Will anyone ever classify one sport as the most physically demanding sport in the world? Probably not! Is HR in motocross a good measure of the intensity of the sport? No! We just simply aren't at a point in science in the sport to defend any one side of the argument 100% without question. However, we do have many other sports to compare the type of efforts required and we can make very good educated claims when it comes to what the sport demands.

Motocross is not an endurance sport by classical definitions, although it may require the endurance of the anaerobic and sometimes anaerobic alactate system. Motocross is very intense and we all know this to be true but, we cant just say its the most physically demanding sport in the world without evidence (which may never happen for any sport). Otherwise you end up being like that guy at the track that thinks he's the best of everyone out there and talks himself up to everyone but, he can never seem to win anything...ever.