Posted: December 1, 2005

Training: Basic Sport Physiology - An Overview

These pages are meant for cyclists that want to test themselves physically through competition with others. These pages try to help you understand the sports physiology that lies behind training. Once you understand the basic physiology, you will more easily see why training needs to be structured for good race performances.

Distinguishing between the aerobic and anaerobic system

There are two fundamental systems called upon for exercise within the human body. The first is the aerobic system. This aerobic system runs with oxygen, i.e. from the air we breathe. We can categorise sports as aerobic if they last for more than 2 minutes. An example of this would be going for a long bike ride, swim, walk, or cross-country ski, mountain bike, even sitting around, studying, ironing etc. This system fundamentally takes in oxygen at the same rate as it is used, almost like ‘paying as you go'.

The anaerobic system runs without oxygen. In general it is needed for sports that last for less than 2 minutes. An example could be the 100m sprint, or a 25-meter swim sprint, or a cycle-track sprint.

It is also used if you are cycling easily along the road and you then sprint very hard for 30 seconds or more. As you do these high accelerations, your heart and lungs (cardiovascular system) does not have time to supply your muscles with oxygen. If you continue for about a minute like this, you start to feel lactic acid kicking in as the oxygen system starts to play ‘catch up'. Up to two minutes and your legs are full of lactic acid and you have to stop with exhaustion, or slow down to recover from oxygen debt. So the anaerobic system is a ‘buy now, pay later' system, independent of the aerobic system.

The aerobic system and development

A fundamental index of physical fitness is called ‘VO2 max', which is the maximum rate at which your body can take up oxygen and burn it in the muscles. A cyclist with a higher VO2 max than his rival should in theory have a bigger ‘engine', allowing him in principle to readily beat his less fortunate opponent. A simple theoretical approach to this says that the larger your capacity to carry oxygen to the muscles, i.e. the larger your ‘VO2 max engine', the faster you should go. But is it that simple?

No. It requires years of dedicated, short and long-term structured training to increase your physical fitness levels to the ‘elite' level. It is also important to realise that VO2 max development is primarily based on your core cardiovascular system, i.e. your heart and lungs, and is dependent on your muscle adaptations to specific exercise.

This means that it will take years to actually race at your real potential. The largest gains in fitness are usually made in the first two weeks of training! It then seems to tail off quickly after a few months and may take another 6-8 years to race very near your VO2 max potential. It would seem as though we have our ‘pre-determined' engine already, and that by training year by year we're able to use a higher and higher percentage of it.

But there is another process in the body that will help you win races, other than a high VO2 max, even if it does go along way towards good cycle results. As I explain soon, there is the “lactate threshold” which is based more on your ‘peripheral' muscles rather than your heart and lungs. This development is slower to plateau than the VO2 max, so the improvements are more noticeable over a very long time period. This means that you could beat a cyclist with a higher VO2 max than yourself, if you have worked carefully on your lactate threshold!

It is also important to realise that top cycling performances are made up of a balanced combination of physiological, psychological, biomechanical and nutritional trainings that must be addressed and worked on for many years before top results in International sports will show up. This could be termed as your ‘global efficiency' to enhance your performances. For example, if you work on your aerodynamics and your cycling pedal technique (see my “skills” section), you will race at a significantly lower percentage of your VO2 max, greatly helping towards winning races. This is one of the reasons why masters (older) athletes can still out perform younger less ‘globally efficient' athletes!

So it would seem that VO2 max is pretty much pre-determined for us, and plateaus quickly. Gains are a matter of a few percent for a lot of hard work over the years . Lactate threshold training plateaus much later, many years later, so gains in training are noticeable throughout your career. Finally, ‘ global efficiency' across all areas is arguably the greatest area for improved performances.

The aerobic system and its three energy systems

An appropriate approach to sports training includes an analysis of the sport in terms of its specific energy components. It is then a case of training these specific systems to ensure optimal adaptations to the body. Remember, the human body is highly sensitive. It only adapts optimally to the exercise you are giving it. If you are bicycle racer, then stick to riding your bike. If you are a runner, stick to running to improve your running.

There are three energy systems that work within the aerobic system, depending on the intensity that you work. The graph below shows which systems are working at certain intensities. Intensity is measured in % of your maximum heart rate.

Graph 1

1. Fat Oxidation System: This is your fat burning zone at 55-70% of your maximum heart rate and you can train for a long time without tiring. The oxygen supplied to your muscles is ample. You feel very comfortable. The body is using primarily fat for fuel as the body spares valuable carbohydrate. It is interesting to note that the human body has many thousands of calories of stored fat, whereas it only has a few thousand stored as carbohydrate.

2. Aerobic Glycolysis System : As you start to go faster, so does your heart rate, and thus you move you into the next system. This is called the aerobic glycolysis at approximately 70-90% of your maximum heart rate. The body is now combining fats and carbohydrate to fuel you. Oxygen is still making this an enjoyable ride, even though you feel you could tire soon.

Lactic threshold or MLSS (maximal level steady state) is defined as the highest heart rate you can hold where the demand for oxygen from the muscles balances its input. This effort is somewhere between the 80-90% of your maximum heart rate. You may hold this for an hour or so, like time trailing for example. The by-product you are oxidising or keeping in ‘equilibrium' is called lactic acid. This is a toxin that is within us, even at rest, but becomes more noticeable with exercise, especially within the aerobic glycolysis MLSS level and above.

3. Lactic Glycolysis System: As you increase your intensity to go from 90% to 100% of your maximum heart rate , you progressively feel burning in your legs. This burning is because the rate of oxygen you breathe in is not keeping up with your muscles demand for oxygen. Lactic acid now starts to accumulate in the muscles quickly. You are now primarily using carbohydrates for fuel. This is becoming more and more uncomfortable. The cells within your muscles start to close down and you indeed start to slow down too with muscle tiredness. Eventually you have to stop because you are near physical exhaustion. This point of exhaustion is called your “aerobic capacity” or VO2 maximum.

**Many people like to term this lactic glycolysis system the ANAEROBIC system, but I think this is highly confusing. The aerobic capacity is dependent on your cardiovascular system – your heart and lungs – and your VO2 max has a close relationship with your maximum heat rate. Remember, the anaerobic system does NOT use your cardiovascular system. It will therefore NOT train your VO2 max.

So there are three systems within the aerobic system. It depends on the aim of your training as to which systems you choose to train. The systems do not ‘switch on' or ‘switch off', but rather they overlap smoothly. The higher the intensity you train, the more lactic acid builds up.

Does always training hard increase my ‘cruising' threshold and VO2 max?

It is tempting to think that the more lactic acid we can build equals the most rapid fitness gains. Wrong!

If you were to train to exhaustion or at least push hard all the time, you would find that you would seriously ‘over-train'. Your legs would constantly feel heavy, your immune system could break down and you could easily catch any cold or illness going. You won't sleep well either, and your appetite will be depressed. So instead of building you up, training hard all the time will break you down.

Lower doses of lactic acid are not so bad though. In fact, the way to acquire the greatest gains during training is to maintain a small amount of lactate in the blood during exercise. This way your body is getting the message to adapt, whilst not being damaged in anyway. I'll shortly explain how we can accomplish this.

So how do I bring about the best adaptations to training, and why?

The best way to know which system you are training is to use a heart rate monitor. See the section on finding your maximum heart rate. If you have access to a sports doctor you may want to go for a VO2 max test to establish your maximum heart rate instead. Going for a VO2 max test will also indicate where your lactate threshold heart rate lies. Subjectivity alone for the lactate threshold probably won't be accurate enough.

Because there is a positive correlation between heart rate and lactic acid in the blood, we can categorize intensity into what is known as ‘zones of intensity'. The one I like has 4 zones that help you train for specific adaptations, based on the aerobic systems above. Before I explain how to train for specific adaptations, take a look at the following pyramid:

The Pyramid showing the four training zones:

Diagram 1

An important point to remember is that the levels of intensity are based on time NOT mileage. As you can see from diagram 1, the shape is that of a pyramid. You will be able to spend more time at level 1 than level 2; more at level 2 than level 3; more at level 3 than level 4. After all, you can adapt quicker to a long slow ride than a high intensity one.

It is also the case that when starting your training you should start with longer rides rather than short intensive ones. Physiological adaptations need to be built up in a pyramid fashion. The larger your ‘base' of training, the higher you will ‘rise'. This means that the longer time you spend doing easier foundation rides, the higher you can launch off your intensity rides, taking you to a much higher level of fitness than pushing hard all the time. This is key to top racing performances. This brings us on to looking at the specific adaptations that are brought about by training at each zone of intensity.

Back to basics

The aim of structured physical training is to improve your physiological ‘efficiency' on the bike. As mentioned earlier, this should be combined with your biomechanical, psychological and nutritional training, to bring about good bike performances during the season. Physiological ‘efficiency' is brought about through the following specific adaptations:

• Zone 1 : training within zone 1 intensity does not improve flat-out speed, but it builds what is termed as ‘endurance'. Endurance comes about by training your fat system to ‘postpone' the point at which glycolysis is turned on. In other words, training the fat system to be more efficient will spare you from using up valuable carbohydrate during racing. For example during a 3 hr race, you can draw on your carbohydrate store much later in the race than your rivals can. They have already depleted their carbohydrate stores and are feeling tired.

So time in the saddle really counts. You need discipline to ride like this for the first few months of winter. How many of you race your mates every weekend over winter, then wonder why summer performances drop off?

A very well trained fat-burning system will automatically supply power at very high intensities too. The top professional cyclists are good examples of this. They can maintain high power outputs in summer for a long period of time. It will also mean that you will recover quicker after hard races and training.

Zone 1 endurance rides are also good as recovery rides . The rides should last 30 minutes and you must be disciplined to turn the pedals over easily. Remember that after a hard bike ride or race, your carbohydrate stores will need to be replenished over a few days, so take it easy on active recovery days and let the fat system take over. I dedicate a whole section on recovery if you want to read more detail on this important subject.

• Zone 2 : you will find that when you ride within the top end of zone 1, you will naturally move into zone 2 on the hills or if you speed up a bit. This is also classed as ‘endurance' so this is fine. Zone 2 enables both the fat and glycogen burning systems to be trained at the same time. You will find that this is the zone of greatest physiological adaptation. This is because you are making lactic acid slightly more significant within the muscles.

Your rides don't hurt you, yet you are stimulating growth within your muscle fibres. You recover quickly and can get out on your bike the next day and repeat the process. This will give you a greater improvement in the summer months than going hard every day in the hills now. Let the fitness come to you! The human body adapts best to small, consistent amounts of quality training over a long time-period.

So, most of your winter training needs to be dedicated to zone 1 and zone 2 rides. This means that you are building the base to your training. This is the foundation or what some cyclists term “conditioning”. The heart rate is kept low. You should be riding with a high cadence (see my “Skills” section) keeping within this zone. Remember to monitor and log how long you have been riding, not the mileage. This is because the body does not understand ‘mileage', but rather ‘time'. A good three-hour bike ride should be a great average winter conditioning ride.

• Zone 3: once we have trained most of the winter season in zones 1 and 2, it is now time to introduce zone 3. This is your “power development” zone. It is still just within the aerobic glycolysis system. This is because it maintains equilibrium with lactic acid production and its dispersal through oxidation. This builds the necessary power on top of your base to make you faster. Normally this is done in the hills or it can be done on the static indoor trainer. Either way, you will be using carbohydrates for fuel and lactic acid will be fairly high in the blood. These rides train your MLSS – maximum level steady state or “lactate threshold”.

As you train consistently and carefully at the MLSS heart rates, you will find that your climbing speed and time trialing pace will start to improve – you will have increased your power output for the same heart rate. You will recruit new, stronger muscle fibres and as a consequence you can ‘oxidise' or tolerate a higher level of lactic acid – literally ‘buffering this equilibrium' to a higher level.

As mentioned previously, if you have a lower VO2 max, you can still beat a cyclist with a higher VO2 max if your MLSS is higher than his! A high VO2 max is not the only attribute that wins races! This makes the assumption that everything about you two apart from engine size is equal, though.

As this zone is tough on your system, you will have to plan for recovery. In February or so it is good to introduce power work once a week, then make it more frequent in spring. The rides should be shorter than your level 1 and 2 rides as carbohydrate will become depleted quickly.

• Zone 4: this is a special zone and should ideally be introduced in spring and/or before the peak of your most important races. This is known as your “aerobic capacity training” or “speed endurance training”. It hurts because we are using the lactic glycolysis system. With the combination of all your base work, cadence skill and threshold work over a period of 4 months or so, you should be ready for top-end capacity training.

Because you'll be working near to exhaustion over the tops of hills, it is better to use this training through ‘interval training' with recovery in-between. The efforts are still using the aerobic system and you should ideally work for a minimum of between 4 to 6 minutes pushing to near maximum heart rate in the last minute. You should recover when the heart rate comes down to zone 1. Repeat once or twice or as many times before you lose any form. Remember, it is quality adaptations we want – so don't teach the body ‘bad form'!

If you push hard within 2 minutes instead of 4 to 6 minutes, you will be using your ANAEROBIC system. This means you won't maximise specific top-level adaptations of your aerobic system come race day.

Although this zone 4 training is important for annual speed endurance training, I can't stress enough how important training sessions within the other zones are in contributing to your VO 2 max development. You must train your other systems optimally over many years to maximise an increase in your engine capacity. Remember the ‘pyramid shape' applied to the short-term as well as the long-term and you won't go far wrong.

Understanding the Anaerobic system

The anaerobic system, as mentioned in the introduction, does not use oxygen. For this reason the anaerobic system is separate from the aerobic system. It therefore uses different fuels for energy than are used by the aerobic system. Depending on the duration of your effort, the anaerobic system will help you to sprint better at the end of a race, or react and “jump” quickly to close a gap between two cyclists. It trains your “anaerobic capacity”.

The anaerobic system has two energy systems: the first is known as the “immediate system”. The immediate system will provide you with energy for your first 10 seconds. There is no lactic acid build-up at this stage. Your effort is explosive and very short. You may use this to catch up a cyclist quickly.

If you continue to hold your explosive effort longer then 10 seconds, you start to use your “short-term” energy system. This is when you may start to push even harder on the pedals up to your absolute maximum power output on the road. You might then be able to hold this power for another 30 seconds, or if well-trained, up to 2 minutes at the very most. This could be your very hard, explosive sprint at the end of the road race. This system differs from the immediate system in that you will start to build up large quantities of lactic acid in the body.

The heart rate is still not a measure of your all-out effort, but as the duration of the sprint continues past two minutes, you either have to slow down to let your aerobic system kick in, or recover fully. In the case of the road cyclist sprinting, it depends therefore how you time your sprint!

If you go sooner to sprint, your chances are that you will use your aerobic capacity and hit maximum heart rate as you cross the line. If you go right to the last 100m of the race and know you have a super-explosive anaerobic capacity, then you will certainly be using your anaerobic system to win the race.

As you can see, it is important to train your strengths and weaknesses. In training, you should practice training your anaerobic capacity in brief durations a few weeks out from your peak races. Start short and easy and experiment. Technique and form are very important to maintain at all times.

So it is not about going hard all the time all year round. It is about developing your aerobic and anaerobic system in a structured manner from year to year. Physical training makes up only one part of your global efficiency trainings. It is therefore consistency, discipline and patience in training that will take you to being the best that you can be.

Easycycling's take home points:

Physical training is only one aspect of preparing for a good season or career ahead. Know that physical training only makes up a part of your ‘global efficiency'.

VO2 max is the maximum rate at which your body can take up oxygen and burn it in the muscles. It takes years to reach your ‘engine's' full potential.

If done properly, you can beat a rival with a higher VO2 max than yourself. This can be done through training your lactate threshold to rise to a higher level than your rival's.

Understand the three energy systems working within the aerobic system: the fat oxidation system, the aerobic glycolysis system and the lactic glycolysis system.

Understand the heart rate zones 1-4 and how they should be applied to your training: remember the pyramid structure at all times! Know that zone 2 is the area of greatest physiological adaptations.

Distinguish clearly between the anaerobic system and the aerobic system. They are very different to each other and adapt the body in different ways for road cycling.

Above all, be consistent in your training. Respect your body and let the fitness ‘come to you'!

Easycycling is owned by Rebecca Bishop: author, designer and webmaster; copyright January 2004.

This article was posted with permission.