What is the Difference Between Aerobic and Anaerobic Exercise?

I have received a lot of questions regarding this topic as of late, soooo here comes some sciencey stuff!

Aerobic can be defined as INVOLVING oxygen, whereas anaerobic can be defined as NOT INVOLVING oxygen.  If we remember from a past post regarding cellular energy production, we burn different amounts of pyruvate and lactate depending upon how much oxygen is present in our cells at the time of glycolysis.

Aerobic exercise can be defined as INVOLVING oxygen.  The primary fuel for this type of exercise is pyruvate.

If oxygen is plentiful at the time of glycolysis, our cells will produce high levels of pyruvate and low levels of lactate to be used by the mitochondria for ATP production.  This type of energy production is extremely efficient and can be repeated literally all day long as long as you are fueling properly during exercise, hydrating, and have enough chamois cream :-).  This is aerobic exercise.

Anaerobic exercise can be defined as NOT INVOLVING oxygen.  The primary fuel for this type of exercise is lactate.

If oxygen is not plentiful at the time of glycolysis, our cells will begin to produce increased lactate.  The ratio of lactate to pyruvate produced will continue to change as the intensity becomes higher and/or oxygen levels decrease.  Eventually, you hit your lactate threshold which is the level at which your body cannot process the lactate being produced effectively and it begins to accumulate rapidly in the bloodstream.  As the body tries to utilize more and more lactate, hydrogen is produced as a byproduct.  The issue here is hydrogen lowers the pH of the blood present in the muscle (makes it more acidic) which is why your muscles burn with high intensity exercise (acidosis).  As the pH of the muscle continues to lower and become more acidic, muscular contractions will become less forceful and eventually cease if the muscle pH becomes low enough.  This is anaerobic exercise.

One of the most interesting aspects of cycling is it involves both aerobic and anaerobic efforts at times.  So, when you are training for your goal event or race, be sure to include both long steady efforts to improve aerobic capacity, but also short and hard efforts (with plenty of rest between) to improve anaerobic capacity.

What is lactate and does it really cause our muscles to burn during high intensity exercise?

“Are we feeling the lactic acid build-up in our legs and feeling the burn everyone!?”  A younger and more ignorant me used to say to my cycling classes and patients.  I, like most fitness professionals, was under the impression that lactate build-up in muscles from intense exercise caused the awful burn (acidosis) to occur.  How does this lactate build-up occur though?

Lactate is a product of glycolysis.  Glycolysis is an energy system used by the body to break down glucose (stored as glycogen in the liver) into pyruvate and lactate.  Think of pyruvate and lactate as teeny-tiny molecules that the mitochondria use to produce ATP (energy).  The amount of pyruvate or lactate produced depends upon how much oxygen is present in the cells at the time of glycolysis.

In exercise where lots of oxygen is present (aerobic) your body will produce more pyruvate and less lactate.  When you continue to push yourself into the higher power zones and above your lactate threshold (LT), the oxygen level in the cells will decrease and you will go into anaerobic energy production, thus producing increased lactate and decreased pyruvate.  Continue to push harder and the levels of lactate produced will continue to increase while pyruvate levels decrease.  For this reason,  exercise physiologists used to attribute lactate to fatigue due to the increasing amount of it present during intense activities.  Plus, a study from 1976 conducted on frog legs found the contractile force of the frogs decreased as lactate levels increased (1).   I am not sure how the connection was made between human legs and frog legs, but this is the point where everyone started saying lactate causes the muscle burn and fatigue associated with intense exercise.

Jump forward to 2008, and the scientific community began to question the old adage that lactate was the bad guy.  The new studies were all pointing to an increase of hydrogen (which is a by-product of mitochondria using lactate as fuel) causing a decrease of blood pH and resulting in acidosis (2).  Let’s put this all together…

  • Stay below your LT and your mitochondria will use more pyruvate to produce ATP and little lactate will accumulate.  You will feel little to no muscle burn and your body will have enough oxygen present to stay in the aerobic energy system.  Whatever lactate is produced can be used efficiently.
  • Push harder and above your LT, your body will start to produce more lactate and less pyruvate.  Less oxygen will be present in the cells and your body will switch to the anaerobic energy system.
  • As your body begins to produce and use lactate for ATP, hydrogen ions will begin to accumulate in the muscle.
  • Hydrogen ions present in the muscle will lower the blood pH (increased acidity).
  • Lower blood pH will result in acidosis (burning muscles).
  • Keep pushing, and this cycle will continue until the burn becomes unbearable and fatigue sets in, ceasing exercise and allowing your body to recover.

So, what is lacate?  An energy source for your muscles!

Does lacate cause your muscles to burn?  No!  An increase of hydrogen ions decreases the pH of your blood which causes the burn.

For more information on GC Coaching and how we can help you increase your fitness, please visit www.gaffneycyclingcoaching.com


1. Lactate and contractile force in frog muscle during development of fatigue and recovery
RH Fitts, JO Holloszy
2. Skeletal Muscle Fatigue: Cellular Mechanisms
D. G. Allen, G. D. Lamb, H. Westerblad

What are the power training zones and what do they mean?

Power training zones can be broken up into many or few depending on who you talk to and what “kool aid” you are drinking.  For this blog, we will be using the 7 zones developed by Dr. Andy Coggan as they are the zones I train with and prescribe to my athletes with great success.  Before reading further though, please go back and read my previous posts “What is power and why do we use it?” as well as “What is FTP, how do we test it, and why do we use it?“.  This will save you a lot of confusion reading this article 🙂

Without further ado…

Zone 1 – Active Recovery – <55% of FTP or <81% of LTHR

This is the easiest zone on the continuum and is employed for times when you want to keep your legs open, but do not want to add any fatigue to them.  During times of intense training, active recovery workouts can help athletes recover faster because you are mobilizing blood-flow to the muscles and joints which will help deliver nutrients to them faster versus just taking a rest day.  Active recovery can be very hard for some people to adhere to however and I will sometimes prescribe a day of rest instead of active recovery if the athlete cannot keep their wattage output <55% of their FTP.  So, if you are one of those athletes who can’t just spin the legs easy and need to crush every workout, active recovery days would not be of benefit to you.

Zone 2 – Endurance – 56-75% of FTP or 81-89% of LTHR

This is the “all day zone” where you could literally spin forever as long as you have enough water, fuel, and chamois cream…Zone 2 is the zone I tend to spend the most amount of time in and heavily prescribe it to my athletes in the volume and endurance building phases (base I and base II).  I like this zone because you can spend a ton of time in it, increase base fitness, and be able to recover in <24 hours to be ready for the next workout.

Zone 3 – Tempo – 76-90% of FTP or 90-93% of LTHR

Tempo is another one of those buzz words in cycling that can have different meanings based on who is saying it.  To me, tempo is the pace in which you ride while sitting in the peloton getting to the more exciting parts of the race.  You aren’t exactly spinning easy, but you definitely aren’t crushing it either.  You can also spend a lot of time in this zone, but you probably wouldn’t want to either.  Tempo is  the black sheep of power zones; it’s not easy enough to spend a lot of time in, but it’s also not hard enough to generate a decent amount of training stress and the fitness gained is usually not worth the fatigue generated.

Zone 4 – Threshold – 91-105% of FTP or 94-99% LTHR

Now we are getting to the fun stuff!  The threshold zone is where most TT, cyclocross, and crit racers spend the majority of their time.  A highly-motivated and well-rested athlete can maintain threshold for upwards of 1 hour.  This zone is usually prescribed during the build through peak phases of periodization and is almost always broken down into intervals with periods of rest between.  This is a crucial zone for the “time-crunched” athlete and can generate a high amount of training stress in a short amount of time.  Be aware though that rest periods are required after multiple days of threshold work to avoid over training and injury.

Zone 5 – VO2 Max – 106-120% of FTP or 100-105% of LTHR

The track pursuiter zone!  Now we are talking short, but very intense efforts.  This zone is also a little misleading because you can’t improve upon your VO2 max once you hit your genetic ceiling.  That is to say each one of us has a different amount of oxygen we can utilize at a maximal effort based on our genetic makeup.  We can train to increase this up to a point, but eventually it will reach a ceiling where it will not increase any more.  Unsurprisingly, professional cyclists have crazy high VO2 Max’s and usually come from an ideal gene pool where the family has other professional athletes in it, i.e. Taylor Phinney.

Zone 6 – Anaerobic – >121% of FTP

Even harder, but reduced efforts here.  Think of a short (<3 minutes) final climb in a road race or a kilo effort on the track.  In this zone we are working to increase an athletes anaerobic capacity (duh!) and functional reserve capacity by doing short but very hard efforts with a lot of rest between to allow for full recovery.  As an athlete’s anaerobic capacity increases, so will their lactate tolerance and ability to push harder for longer above their FTP.  This is the difference between making the race winning break or summiting the climb with the front group versus being shelled.

Zone 7 – Neuromuscular – ALL OUT!

This zone is where you are literally improving the neural connection between your brain and muscles, plus increasing the density of your ligaments and tendons.  You are doing maximal intensity effort for <10 seconds.  Think of a track cycling sprint race when the athletes are winding up the gears for the final lap.  They are going from ~30 RPM to well over 120 RPM in a huge gear in a very short amount of time.  Being able to produce this amount of effort requires a tremendous amount of muscle, tendon, and ligament strength as well as excellent brain->muscle connection, a.k.a. neuromuscular power!

What is FTP, how do we test it, and why do we use it?

FTP, what?  FTP, who?

FTP has been the buzz word in cycling for the past few years now and can mystify, irritate, and exhilarate athletes (and their coaches) all at the same time.

FTP stands for Functional Threshold Power and can be defined as the maximum power output an athlete can maintain in a quasi-steady state without fatiguing for 1 hour.  A good example is to think of the red line on your car’s tachometer…

Tachometer 590x590

The red line represents your FTP.  You can push up to the ride line and hold this output for an hour (if your fitness and freshness are good and you are extremely motivated mentally), but push just a little bit over the red line and you run the risk of fatiguing early.  So, now that we have a basic understanding of what FTP is, how do we test it?

The gold standard of FTP testing would be to ride for 1 hour ALL OUT and whatever your average power is for the hour would equal your FTP.  Simple, right?  Ha!  This would obviously be awful both mentally and physically for any athlete and you would need to be super motivated to be able to sustain the abuse of a full gas effort for 1 hour.  This also would take a substantial amount of recovery afterwards and may even decrease your fitness in the process because you would not be able to resume normal training for a couple of days.  So, the 1 hour test is very accurate, but not the best for repeated tests and may not be appropriate for all athletes.  The good news is people way smarter than me (yeah right!) have developed other ways of testing athletes’ FTP in a better way.

My personal favorite is the 20 minutes ALL OUT test.  This test was developed by Dr. Andy Coggan who has evaluated literally thousands of athletes ranging from cyclists, to rowers, to XC skiers and has also produced many journal articles on the topic.  The test goes like this:

  • Warm up for 10-15 minutes
  • Ride ALL OUT for 20 minutes
  • Record what your average power was for the 20 minutes
  • Multiply that number by .95
  • Voila!  You have your FTP
  • You can also use this above test to determine your lactate threshold heart rate (LTHR), just record your average heart rate for the 20 minute test instead.

I like this test best because it is easier (read less painful) than the 1 hour test, it has greater repeat-ability, and will not require a long recovery afterwards so the athlete can resume normal training immediately.

Why do we as coaches and athletes use FTP?  Simple!  Because it makes our training more precise and enhances the functionality of the power meter we invested in.  Be aware though, your FTP in June will not be the same as in January and your FTP outdoors will differ from the trainer.  This is why testing should be done throughout the year and ideally before each phase of periodized training.  This ensures you are getting the most out of your training and the best return on investment of your time.

Further Reading:

What are the training zones?

For more information on GC Coaching and how we can help you increase your fitness using power, please visit www.gaffneycyclingcoaching.com

What is power and why do we use it?

What is power?

First things first, let’s go back to Physics class…

Power is a measurement of work and more so the rate at which said work is done.  To make this specific to cycling, power is force (how hard you are pushing the pedals) multiplied by velocity (how fast you are spinning the pedals).  This equation will result in a wattage output.  So, to produce more wattage you either need to increase your cadence (Chris Froome) or churn a larger gear (Andre Greipel).

Why do we train using power?

Training with power is currently the most objective and immediate measurement of what your effort is on a bike.  Said another way, power trumps all other training tools (RPE, heart rate, etc.) because it gives instant and precise analysis of how hard you are working physiologically to propel yourself forward.  Power also does not change based upon stress (both emotional and thermal), hydration status, or altitude.  These factors will all drastically affect RPE and heart rate however.  Power is always what it is!

Another thing to consider about training based on heart rate, especially for the competitive athlete, is heart rate takes around 3 minutes to respond and level out when producing a given effort.  So, if your coach or training plan instructs you to do “3 times, 2 minutes at Lactate Threshold”, but you only have heart rate, you really won’t be sure if you are indeed training at your LT zone.  Whereas if you have a power meter, you can simply hit the lap button on your computer, and keep your average power in your LT zone, simple!

However, the biggest advantage to training using a power meter is the amount of data it provides all about YOU.  This data can also be translated into much easier to understand graphs and charts via Strava and Training Peaks as compared to years past.  Training with power gives you insights into:

  • Current fatigue, fitness, and form.
    • Yes, heart rate can provide this too, but power data is far more precise.  This monitoring tells if you are providing your system with enough stress to cause a training response, but also when you need to rest to decrease your fatigue and to prevent overtraining.
  • Objective progress.
    • Is your FTP improving?  Can you produce more power at a lower or the same heart rate?  Are your watts/kg improving?
  • Goal achievement.
    • Goals and achieving said goals are made easier with a power meter as you know what your body needs to be able to do simply by looking at others who have competed in similar events.
  • Pacing of events/races
    • Hello IronMan!
  • Race analysis.
    • Were you dropped on a certain hill?  Did you bonk at a certain point in the event?  A power meter, and a coach, can give provide you with the “why”.
  • The list goes on!  You get the idea though.

Disadvantages of power

With that being said though, power meters are expensive, complex, and can be unreliable at times (batteries dying, forgetting to calibrate/zero out before each ride, producing huge spikes in power occasionally, etc.).  Plus, few people actually understand how to utilize one to the best of its abilities and they can be very overwhelming initially.  Fortunately though, the price of power meters decrease each year along with their reliability and accuracy increasing alongside it and, besides working with a coach, nothing will enhance your training more than a power meter.

What do you think?  Is power worth the investment?  Have you experienced an increase of fitness using one?  Or is it all just some sort of sorcery!?

Interested in taking the leap into training with power?  Check out our partner, PowerTap!

For more information on GC Coaching and how we can help you increase your fitness using power, please visit www.gaffneycyclingcoaching.com