Aerobic Threshold Training

by Chad on January 21, 2010

Using your VO2 max/sub-max results for training that can lead to better performance and fat loss.

Aerobic threshold is marked by the Heart Rate at which the body goes from burning all fat as the main fuel source to mixture of fuel that includes some sugar. At this point the body begins working too hard in its present physical condition to get enough oxygen to the muscles to metabolize fat as the only fuel.  Getting oxygen to the muscles is part one of the equation, the muscles actually being efficient at up taking the oxygen is the second part. The more oxygen being utilized at the Aerobic threshold the more energy that can be created via fat! This is why building a solid “aerobic” base is imperative to overall performance and/or fat loss. Most of us go to the gym to beat ourselves up for the burning of calories and hopefully the weight loss that accompanies this. Athletes think about beating themselves up because that’s what racing endurance events is all about. Becoming a better fat burner overall is the best way to become healthier, leaner and faster no matter what outcome your looking for.

Running Ultimate Test Lab has exposed us to a lot of different athletes as well as people  just trying to get into better general health. What we’ve found since 2006 has been extremely enlightening. We’ve tested some people multiple times with our VO2-MAX/Sub-max test and found that a lot of “high end” athletes are really bad fat burners because they’ve been training too intense for too long. We’ve always suggested that a portion of their training has got to be scaled back into their fat burning zone so as to re-train their bodies to use fat as a fuel. Fat, as much as Gatorade, Powerade, Accelerade and a dozen other companies don’t want you to know, is the ultimate fuel source. Ultimate because even the leanest of people have enough fat on their body to last hours upon hours while sugar has a limited supply! Another HUGE advantage of using fat for a fuel is that there are no harmful byproducts. Two byproducts of fat metabolism are Water and Carbon Dioxide which are completely harmless substances to a healthy body that will either be perspired out or leave the body via the breath or urine. Glycogen, otherwise known as muscle sugar, on the other hand has a nasty byproduct of Lactic Acid or more precisely excess hydrogen atoms which is what causes the burning sensation in the muscles. Now the more we train at higher sugar burning levels the more tolerant of lactic acid we become. This of course is a good thing for athletes and non-athletes alike. The athlete will encounter times during en event that they’re aerobic and anaerobic thresholds will be crossed and being tolerant of lactic acid is mandatory for performance. The non-athlete will also have times that they will cross their aerobic and anaerobic thresholds and need to be somewhat tolerant of the burning muscles. Training/exercising above aerobic and anaerobic thresholds will also push the heart and help strengthen the cardiovascular system as a whole. Once a person goes beyond their anaerobic threshold they will start to build up what’s called oxygen debt. They are operating without oxygen and will need to pay that oxygen back once going under their anaerobic and aerobic threshold. The higher above their anaerobic threshold they are working the more debt they cause. Paying off oxygen debt is a function of recover y and why some people pant and pant with an elevated heart rate for longer periods of times while others seem to be back at rest in seconds. Heart rate will not return to normal or at least lower until oxygen debt has been paid off. The stronger and more developed a person’s heart is the more oxygen they can pump in general and at their thresholds the quicker the debt gets paid off and the quicker the recovery.

There are all types of measurements/calculations for aerobic/anaerobic thresholds and although many of them are based upon sound scientific principals they will always put a person into a bell curve. A bell curve simply states what the majority of people “should” be! The problem with all bell curves is that the human body is too complex and individual to be averaged out. A person’s background, genes, diet, body-fat percentage, past and present physiology make the bell curve for averaging a person’s aerobic and anaerobic threshold impossible to be even moderately accurate. We’ve tested people that are excellent athletes per their VO2-Max that have had extremely low aerobic thresholds and we’ve tested mediocre athletes with a low VO2-Max that have had higher then normal thresholds. When performing a VO2 test with a machine that is measuring the amount of oxygen being utilized by the body we can determine that person’s exact heart rate and oxygen consumption at their aerobic and anaerobic thresholds for their present condition.  This of course can change over time and the goal of being tested and discovering thresholds is for the purpose of improving or keeping them the same. Knowing accurate thresholds creates training zones that need to be acknowledged.

Upon first acquiring a heart rate monitor in the early 90’s my way of using it and the way of a lot of athletes was simple; find out our average heart rate during a race or endurance event and then set our monitors to beep if we fell more then ten heart beats below that average during training. It was a way to be accountable to our high intensity outputs during our races. The problem with that philosophy of no pain, no gain is that we really learned to force our bodies to perform at higher levels but not necessarily perform more efficient and/or effective which in the long run can cause injury and ultimately the lowering of energy thresholds. If that average racing heart rate was greater than our anaerobic threshold, which for most of us it was, we were teaching the body to burn sugar!

It’s fairly simple, if a person trains their body to be a sugar burner, going above anaerobic threshold for longer durations, they will become a better sugar burner and in the process lose fat burning potential! If the body is trained in fat burning zone it will learn to become more efficient and effective at burning fat. This can possibly raise the Heart Rate at which they cross Aerobic Threshold, but will always increase the amount of oxygen they can uptake up to and beyond their aerobic threshold. Training above anaerobic threshold is training it to be more efficient at burning sugar which has already been shown to be less then desirable because of the byproducts but also for the fact that the human body can only store so much sugar in usable form. Glycogen, which is the body’s usable sugar, is stored within the muscles and liver of the body and is there for use when there isn’t enough oxygen to use fat for energy. Performing above aerobic threshold will cause the body to slowly use up glycogen and performing above anaerobic threshold will more quickly cause the body to use up it’s supply of glycogen.  Once the body runs out of glycogen it cannot perform at high levels and the person will hit the proverbial “wall.” If depletion of glycogen is severe enough they might literally shutdown physically. Fat, even the amount on lean people, is in limitless supply on the body and running out is virtually impossible. For example, a 160lb man who is 8% body fat, lean by all standards, still has 12.8lbs of fat on his frame. If he was physically prepared to perform a six hour event and were to stay within their aerobic threshold for 100% of a six hour event and burn a high 1100 calories per hour he would only metabolize 1.9 pounds of fat! That same person going above aerobic and anaerobic threshold will run out of glycogen, depending on how much their particular body can store within a few hours. Many athletes try to ward off the inevitable depletion of glycogen with sugary/starchy products that quickly raise blood sugar and hopefully get converted to glycogen to be delivered to the muscle cells for energy. In a perfect world this would be possible. Unfortunately the body is limited on how much of this ingested food can be absorbed and ultimately converted. Under the physical stress of an event the efficiency of this conversion/absorption exponentially decreases leaving the participant on a one-way path into the wall.

The best way to become a better athlete is to become a better fat burner! Finding aerobic and anaerobic thresholds for the purpose of training zones is what getting tested is all about. Improving the aerobic threshold is best done by training in that zone so as to be able to perform more work in that zone. Whether or not the Heart Rate of the aerobic threshold is low or high truly doesn’t matter for training purposes.  If the heart rate is low at this threshold, which is relative to your present condition, the prescribed method to raise it would be to train up to it the majority of the time. If the heart rate is on the higher side the recommended training would be to train up to it the majority of the time. Training within the low, fat burning zone, will increase oxygen uptake over time and allow the person to workout at higher and higher levels while still being in their low zone.

Interval training for athletes and non-athletes is a must! Although the goal of an athlete would be to stay within aerobic and anaerobic thresholds during an event they will no doubt go above and sometimes WAY beyond  them because of a hill, headwind, or an uncontrollable rush of adrenaline when they see that competitor up in the distance. Training the heart and cardiovascular system at higher levels is a must so that recovery and oxygen debt can be paid off while still in “race” mode. The person that comes to Ultimate Test Lab with a great VO2 Max, a great recovery, but a lower then “average” aerobic threshold will be given the advice to spend more time training in their low zone to build up that aerobic base. Sometimes this can be up to 80-90% of their training time. A person with high aerobic threshold but lower then average VO2-max and slow recovery might be put on a regimen that calls for 60% low and 40% intense to help build VO2 max as well as recovery. A person’s thresholds will change over time, but usually takes months to have any significant change occur. Once the Heart Rate at aerobic threshold increases the person can then train at the new higher intensity and still be in their “low zone.” If the Heart Rate doesn’t increase, which can be the case, we can still show performance gains by the volume of oxygen at their threshold increasing by ml. More oxygen means more fat being metabolized into energy equaling more speed.  The goal of any athlete should be to increase the intensity of what they can do while staying in a fat burning mode!

Leave a Comment

Previous post: