What is aerobic fitness?
What do we mean by being fit? There are different ways to consider it. In simple functional terms it might mean you can complete a park run or even walk into town to do your shopping, or it might be shaving 5 seconds off your half marathon PB. So there is certainly an individual nature to what you might call “aerobic fitness” and it will mean different things to different people. But we must also consider the more scientific definition too. I’m sure you’ve all heard of the term “aerobic fitness” or “aerobic capacity” but what does it mean exactly?
To start with it is important to understand that there are three main energy systems that the body utilises to fuel activity, these include two anaerobic pathways of the phosphocreatine
pathway and glycolysis as well as the aerobic system. Anaerobic merely means “without oxygen”, so for example, if you run up a flight of stairs and you complete the task within about 10 seconds you will have activated the anaerobic pathways as there isn’t enough time to involve oxygen in burning fuel to allow for muscle contractions etc. However, if you go for a long run, once you’ve been running for more than a few minutes you will be utilising the aerobic pathway. So aerobic fitness really relates to a) what the maximum amount of oxygen consumption you can achieve is and for how long you can maintain higher levels of this.
Aerobic capacity is a term commonly used but this, by definition, is a little inaccurate as it relates more to the total amount of oxygen consumed by a person in a lifetime. When discussing aerobic fitness, “oxygen consumption” is a more accurate term. Oxygen consumption at rest is about 0.3 L/minute, with an elite athlete able to reach up to 20 times this when performing maximally. Maximal oxygen consumption is commonly expressed as your VO2 Max. The higher your VO2 Max the greater your oxygen consumption and therefore the better your aerobic fitness.
How can you find out your aerobic fitness?
There are simple ways to estimate your VO2 Max, although I forewarn you – they are all brutal. The most accurate way is to be in a lab with a facemask attached that allows analysis of respiratory rate and volume and concentration of oxygen and carbon dioxide inhaled and exhaled. However, there are simpler ways to estimate your score.
For middle to long distance running the Maximal Aerobic Speed (MAS) Test can be done in the gym by yourself. For this you start the test running at a pace somewhere between 8 and 12 km/h depending on your baseline fitness. Those with a better starting level of fitness should start at a speed closer to 12km/h. From here you run at the same pace for two minutes before increasing the speed by 1km/h and then maintaining that speed for two minutes before once again increasing the speed by 1km/h. The last speed at which you can complete two full minutes of running is your MAS score. We then need just a small amount of maths to complete the equation:
3.5 x MAS score = VO2 Max (value in mL/kg/minute)
The tables below, taken from Powers & Howley 2012, show normative scores for VO2 max divided by age categories. How do you measure up?
Maximal oxygen uptake norms for men (ml/kg/min)
Maximal oxygen uptake norms for women (ml/kg/min)
For team sports that involve short bursts of speed with recovery periods over a prolonged period time the Yo-Yo test is a good option. This involves running 2 x 20-meter distance followed by 2 x 5 meter distance walk/jog at steadily increasing speeds. Timings for completion of each run are governed by automated bleeps. You continue this routine until you fail to get to the finishing line on two occasions within the bleeped time. You can then process your data using an online calculator such as at https://www.theyoyotest.com/calculator-yyir1.htm.
How can you improve your aerobic fitness?
There are several factors you need to consider when planning how to improve your aerobic fitness:
- Your starting point
- The frequency you need to train
- The intensity you should train at
- The duration you train for
- The specificity of your training
- What mechanisms you are trying to influence
This can all be answered fairly easily with just a bit of understanding of what the requirements are for the sport you are participating in and some basic principles of physiology.
The lower your baseline fitness the greater the potential for improvement. If you are beginning your regular exercise venture after years of being relatively sedentary then you will most likely have a low VO2 Max rating. The degree of difficulty to increase this from 35ml/kg/min to 45ml/kg/min, for example, would be fairly straight forwards. However, if you’re at a more elite level, turning 75ml/kg/min to 80ml/kg/min, for example, requires much more specific training methods. It is recommended that you train at least twice a week if you are coming from a more sedentary background and three times a week for more advanced performers.
The intensity relates to how you are training which relates to what you are trying to achieve from your training and also the method you are implementing. Training at 90-100% of your VO2 Max is currently thought to give you maximum gains in aerobic fitness. Whilst low intensity continuous training will give an improvement in aerobic capacity, it is thought that a well-designed intermittent training programme is more effective due to an individual spending more time at a high percentage of VO2 Max. A training session is recommended to last between 35 and 45 minutes for optimal gains.
Parameters for interval training
Lets suppose you are long distance runner or training for a long distance race. To improve performance developing your endurance and VO2 Max are important. For this you may wish to implement any of the below methods, but are likely to favour either “long-long” or medium-medium” methods due to the longevity of the task.
Joyce & Lewindon, 2014
Depending on your base line level of fitness the parameters you train at will need to be more specific. Clearly you can manipulate the parameters to make them more demanding, but they should also be achievable and not put you at risk of overtraining. You can use a Rate of Perceived Exertion chart (such as the Borg scale) or track your heart rate with smart watches etc to monitor your heart rate. A reasonable rule to apply when selecting your regime is to apply a 1:1 exercise : rest ratio. I.e. 1 minute of exercise to 1 minute of recovery.
A real-life example of a client of mine who is training for a half marathon is seen below:
MAS = 14.5km/h
VO2 Max = 14.5 x 3.5 = 50.75ml/kg/min
Long – Long parameters selected:
4-minutes exercise (13.1km/h) : 4 minutes active recovery x 5 reps x 1 set
Total duration: 40 minutes (excluding warm up)
Medium – Medium training parameters selected:
1-minute exercise (15.9km/h) : 1 minute active recovery x 4 followed by 5 minutes rest x 3 sets
Total duration: 42 minutes (excluding warm up)
Athlete X will be participating in one long-long and one medium-medium aerobic capacity session a week for the first 4 weeks of training. As his fitness and training progresses the parameters will be modified to facilitate progress, prevent monotony and accommodate for race day.
If you are primarily participating in team sports then short-short training will be both essential and far more applicable to you. Depending on your base line I would suggest starting on lower parameters and then building as fitness and performance improves. It would also be worth including either long-long or medium – medium training into your overall plan as although team sports are often made up of short bursts of sprinting followed by rest periods this sequence happens over and over again and so you need to be able to sustain your aerobic fitness for prolonged periods too.
There are many ways of training aerobic fitness and indeed at times it is pertinent to train aerobically in a sport specific way such as with small sided games in team sports. Your goals, needs, requirements of your sport and baseline fitness will all have a bearing on this. This blog presents just a brief overview of what aerobic fitness is, some low cost and simple ways to approximate your current aerobic fitness level relating to your VO2 Max and how you could make your training specific to influence and improve on your aerobic fitness. There are many other ways to influence aerobic capacity and make the training individualised to the sport, but hopefully from reading this blog you have something relatively tangible to take away and apply to your training and start improving your performance.
Joyce D, Lewinden D. High-performance training for sports. 2014; Human Kinetics, USA.
Powers SK, Howley ET. Exercise Physiology: Theory and Applications to Fitness and Performance, 8th Edition. 2012; McGraw Hill: New York, NY.