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.

How Rest Improves Your Performance

So this topic became a big deal of conversation for me two times this past week. The idea of rest and unloading your body from the stress you are putting on it to increase performance. It was a shock to me to hear this lack of understanding of the importance of rest and recovery. But none the less lets start from the beginning.

The first thing you need to understand is the Theory of Supercompensation. This theory states that you start at a certain baseline. To take from Patrick Ward we will refer to this as the starting point of our stress bank account. We start at a base line level and we invest that money into some product for our workout. That investment then puts us at a low in our bank account until we get some return from that investment. It then puts us in the positive once it begins to pay us back.

So if we apply this directly to the model above we get the following. We start at baseline and we apply a stress to our body like a workout, riding or racing. This stress then depletes our reserve to a certain point and now our body compensates to that stress and we then have a slightly greater capacity. If you put this into light of a workout its really simple. If I want to improve my bench press, I lift and challenge myself. The next day my arms and chest may be sore and a bit weak but, a couple of days later I'm just a little bit stronger.

Now a big thing to recognize is that there are different kinds of stressors and of different intensities. These different stressors can impact the length of time it takes to come back up above baseline. Below is a good example of this extracted from Olbrecht (2000).

The chart here shows how these different types of stress impact the time that it takes for your stress bank account to go positive from your physical investment. The big thing you need to disseminate from the titles on the chart are this. Extensive refers to a greater amount and duration but maybe not as intense for your overall capacity. Intensive refers to very high intensity like big heavy lifts or a max but, you cant do these for a long duration or for many reps.

Now there are an insane amount of what ifs and modifications that can be made to this model and idea based on your own genetic abilities, your physical fitness and quality of life related to stressful events not directly associated to physical activity. For now just assume that you meet the this chart at it's very basic level.

Each time you go riding the stress that your body endures can be pretty severe. A full race weekend is equivalent to the last box of Intensive/Strength Training/Competition. It can take you between 48 to 72 hours to fully recover. Now when you ride really hard even when training, you incur this same kind of stress. However most of the time your not riding at 100% all out effort which means you may be more along the Sprints/Short Sets on medium intensity riding days or in the Extensive/Anaerobic to Intensive Anaerobic range; depending on your intensity of riding that day. So riding at a decent pace to help improve your ability to race will land you somewhere between 30 to 60 hours to fully recover.  Don't think that just going out and riding the track and hitting some jumps for fun meets this. We all know when we're riding hard and when we're just letting the bike work for us to hit some jumps and have a good time.

So now back to why does rest matter so much? You have a necessity for rest every day and I think we all understand each week also. Most people leave 1 day as their rest day. However us motocrosser's don't have that same luxury. We ride Saturday and Sunday just to get any amount of track time and then we return to the stress of the regular week. Now think about that accumulating day after day, week after week and month after month. Now your trying to work out during the week to get your fitness up to get faster. How do you think that looks over time?

Eventually if you compile this together across time you realize all that stress adds up. At a certain point your body cant return back above its baseline and adapt to make you better. This is when we apply an unload week. In strength training periodization this is a very formal process that occurs somewhere around the 4th or 5th week depending on different variables. However if you think about it, we work out maybe 2 or 3 times a week and ride maybe 1 or 2 times in the week for a total of about 4 of 5 days of training focus; then we try to get some rest. We just did 3 or 4 weeks of hard work why don't we get a week of rest just the same?

This doesn't mean that we take a whole week off by any means but we definitely reduce the overall volume of our work. We still give it some stress to make sure that we don't lose our progress we just achieved, but we allow our-self to fully recover and improve. This becomes a huge factor long term because of how intense motocross can be.

I don't know this for a scientific fact but I assume that guys racing outdoor nationals can take up to 5 days to fully recover. The reality is that certain types of stress can go beyond the models above for time of recovery. Doing a true max lift for something like squats or deadlift's could take you up to 5 to 7 days to recover completely. Now think 30 minutes +2 laps twice while its 100 degrees out, you better believe that's equivalent. 

The last major thing is that people don't realize your body makes its adaptations during rest and especially sleep. When you sleep your body is able to fully repair itself. The other really cool thing that happens when you sleep is the movement patterns that you just practiced or learned become ingrained into your permanent memory bank. All sorts of cool things happen in our sleep. Just check out this Discovery Channel excerpt below.

The real take home points are this, plan yourself some rest time. It is important to improving your overall performance. This doesn't mean quit exercise completely for a whole week, just scale back the total volume of work. Think about the type of stress your body is undergoing and better plan your training. You can use the chart above with the different times as a general guideline to improve your training. Then go ahead and start adapting this chart to fit you and create some personal zones based off your own intensity and observations. Then you're able to better plan your overall training and better plan your rest to improve performance.

Vibration and Bike Setup - Arm Pump Science

We all know that bike setup is important for your speed, comfort and to not wear you down so fast. I'm not here to tell you exactly how to setup the bike but, to educate you on why that setup impacts your physical performance so much.

We all have dealt with the revered arm-pump. This horrible mechanism comes to haunt you in the late stages of a race and can cause your lap times to seriously increase and you lose positions. This mechanism is fairly complex and we have some real challenges in dealing with it. The first thing that I will state is why I don't think it's lactic-acid.

I have heard this before from people and lactic-acid is argued to potentially not even exist in the human body because, it requires a level of acidity the body cant achieve or maintain life at. Regardless we know that Lactate does exist, which helps to shuttle out negative bi-products from exercise and also free Hydrogen ions (H+). These H+ cause your body to be more acidic and can cause that burning sensation you feel. Additionally, the presence of increased H+ concentrations can cause muscles to fatigue faster by inhibiting part of the process that allows them to contract or by competing with part of the complex chemical process of initiating a muscle contraction.

So now.....we all in the motocross world know that your suspension can increase this arm pump and your grip choice for your bars can reduce some of it. The key is why? Vibration!!

Your bike itself when you roll the throttle creates a certain amount of vibration. This vibration then resonates through your body. Additionally, a rough track with bad suspension will put a large volume of high impact stress into your arms from lack of effective absorption from the forks themselves. This in essence acts similar to vibration when the bars are jerking around in your hands, though this would be at a small scale level. This is insanely critical to your performance and this is why.

Bovenzi and Griffin (1997), found that high frequency vibration caused a reduction in blood flow to the fingers, when the hands were tested for blood flow during different vibration frequencies. Additionally Bovenzi et al. (1999), found a reduction in grip strength from the vibration caused by loggers using hand saws. This research shows that high vibration can potentially reduce blood flow to your hands, deprive you of required nutrients to maintain strong muscular contractions and lead to fatigue. This is one potential reason. Some conflicting evidence states a different idea.

According to Nakamura et al. (1995), blood circulation was increased when exposed to whole body vibration and grasping bars. Now additionally what we know in the training world is that high frequency vibration can cause greater amounts of motor neuron activation. In layman's terms; the higher the rate of vibration the greater amount of muscle activation over all and the faster your body learns to do that. This is of course is only true and studied up to somewhere around 80Hz or slightly more.

According to Hazell et al. (2007), higher frequencies of vibration increased muscle EMG activity in general. An average of 3.5% increase in muscle activity was observed across multiple exercises for different parts of the body. This then supports the findings of Nakamura et al. (1995) that blood flow is most likely increased during vibration. Increased blood flow during increased muscle activity seems logical. This though means a shorter time to fatigue from working harder and an increase in H+ that leads to faster fatigue/muscle acidity from more work.

Think of when you were hurt and hadn't been on the bike for a long time. When you first got on and those first few weeks riding, you get arm pump pretty bad until you ride more and it slowly dissipates. The rougher the track the worse it is but, overall it is less the more frequently you ride. It's just like weight training, the more you work the more your body adapts to the stress.

Now this isn't revolutionary science. We've all played a game or been in some situation where you held onto something that was vibrating and it caused your hands to cramp up. I remember playing an Adams Family game at the arcade where you had to hold onto the handles as long as you could while they vibrated at higher and higher frequencies. Eventually it was too intense and you couldn't bear it. Then your hands hurt for a while after. It's the exact same thing just on a larger scale and for greater duration's of time.

In conclusion, I believe that the evidence more clearly supports the idea that the vibration from the bike increases the amount of work the muscles are doing in a very short amount of time, which leads to greater fatigue based on the mechanisms mentioned above. Your arms work harder and create more H+ to increase the muscle acidity. The time to fatigue is already naturally going to be less but, the now secondary effects of increased H+ makes things far worse. The kicker is that your body can only produce so much lactate and transport bi-product out of your body so fast. While the process to get rid of this bad stuff moves along at about the pace of a little Chevy Geo, your muscles are working at about the pace of a Ferrari 458.

Considering all of this and the simplicity of it, you can see why bike setup becomes so critical. You could inadvertently sabotage your own physical performance on the track. The key is to take this simple idea and apply it to your bike setup, to optimize your performance.

References:

Bovenzi M., Zadini A., Franzinelli A., & Borgogni F. (1991). Occupational musculoskeletal disorders in the neck and upper limbs of forestry workers exposed to hand-arm vibration. Ergonomics, 34, 547-562.

Bovenzi M., & Griffin M.J., (1997). Haemodynamic changes in ipsilateral and contralateral fingers caused by acute exposures to hand transmitted vibration. Occupational Environmental Medicine, 54, 566-576.

Bovenzi M., Lindsell C.J., & Griffin M.J., (1999). Magnitude of acute exposures to vibration and finger circulation. Scandinavian Journal of Work Environment Health, 25, 278-284.

Hazell, T.J., Jakobi, J.M., & Kenno, K.A. (2007). Effects of whole-body vibration on upper and lower body EMG during static and dynamic contractions. Journal of Applied Physiology, Nutrition and Metabolism, 32, 1156-1163

Nakamura H., Ariizumi M., Okazawa T., Nagase H., Yoshida M., & Okada A. (1995). Involvement of endothelin in peripheral circulatory induced by hand-arm vibration. Central European Journal of Public Health, 3 (suppl), 27-30.