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What VO2 Max is

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VO2 Max is all about your body's ability to get Oxygen to the working muscles, to prevent them from fatiguing over prolonged periods of exercise. Having a good VO2 Max is essential for a firefighter, when work conditions may demand high levels of physical output, such as during BA wear.

 

VO2 Max is largely determined by genetics. Being naturally blessed with a big, efficient heart and lungs is essential if you want to be an elite endurance athlete... But most of us are not worried about elite performance - we just want to be the best that we can be and reach our own potential - which hopefully is above the minimum standard of 42 ml/kg/min required by the fire service! 

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How VO2 Max is measured

 

VO2 Max can be tested maximally or sub-maximally ie, by exercising you at your highest capacity, or at a relatively comfortable capacity below your maximum exertion. In fire services, VO2 Max is often measured a number of different ways within a brigade and between different brigades. Some services use a step test (though this is gradually being phased out), some use a treadmill test known as the Chester Treadmill Test, and some use a Fireground Fitness Test. Other tests may also be available. Details of these tests can be found here.

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VO2 Max can be trained!

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There are a number of physiological processes that we can change through training to improve our VO2 Max score. There is also a fairly easy win... we'll come to that last!

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Change number 1. We can increase the volume and contractility of our heart muscle. This means that we can deliver more blood filled with Oxygen to the working muscles with each beat.

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Change number 2. We can improve our body's ability to deal with the lactic acid that is produced during higher intensity efforts. This means that we can work harder, for longer, as we are more comfortable at higher intensities.

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There are other physiological changes too - but the above are the main changes.

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Training methods

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There are two main training methods to affect these physiological changes:

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1. Increase the volume of your low intensity activity. Slowly and steadily adding minutes or hours to your activity will make improvements - but only if you are relatively untrained to begin with. Government guidelines are that you should do 150 minutes per week of moderate to vigorous exercise. However, that volume of training is not actually going to make a huge difference to your physical capacity - it's simply not enough. Instead, try to build slowly towards 6-10 hours weekly of low intensity steady state activity such as swimming, cycling, walking or jogging. It'll take approximately 8-10 weeks for you to realise the VO2 Max improvement this way - but it will definitely work! Training this way you could expect to see improvements of 5-10% within a 12 week period.

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2. If you have a good level of fitness already, consider doing some HIIT (High Intensity Interval Training). HIIT training has been evidenced to give you the best 'bang for your buck' in terms of VO2 Max improvements per minute spent exercising. HIIT training will make all the physiological changes to your body listed above and will make the changes pretty quickly! You should feel improvements within 4-8 weeks of perhaps up to 10-18% improvement! A 20 minute HIIT session 1, 2 or 3 times per week should be enough depending upon your fitness level.

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If you would like free examples of training sessions you could do, please message us!

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The easy win?!

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So what is this easy win (we all like easy wins!)... Well the answer is body fat weight loss! Here's the sciencey bit:

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VO2 Max can be expressed 2 ways:

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1). a 'raw' score for example you may be able to push 4500 millilitres/oxygen around your body in one minute.

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Or more commonly...

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2). The raw score divided by your bodyweight in kilograms. This is the method that the fire service use. This expression of VO2 Max is more meaningful, as it takes into account your 'power to weight ratio'. A good analogy for this, would be that the raw score is the size of your car engine. Let's say that you have a 2.0 litre engine. A 2.0 litre engine in a big truck would not be very useful. It wouldn't produce much speed and would be under constant strain. A 2.0 litre engine in a small car however, would have 'Vavavoom'!

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EG. 

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Raw score is 4500 ml/min

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If bodyweight is 75 kgs, then the VO2 Max would be 60 ml/kg/min (very good club athlete).

If bodyweight is 110 kgs,  then with the same raw score the VO2 Max would be 41 ml/kg/min (national average VO2 Max for males (average for females is approx 36 ml/kg/min), this would not pass the firefighter fitness test.

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Let's imagine that a firefighter fails the firefighter treadmill test... they last 10 minutes out of the 12 required to pass. According to the table below, their VO2 Max would be approx 36 ml/kg/min. Let's imagine they completed the test at 95 kgs bodyweight. If we do some maths, we can see that the raw score for VO2 Max must therefore be around 3420 ml/min. (95 x 36 = 3420 ml)

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So how much weight would this firefighter need to lose in order to pass the VO2 Max standard? Here's the maths:

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3420 ml / 80 kg = 42.75...... ie PASS! So the firefighter would need to lose 15kgs of weight. Obviously, if possible this should be bodyweight that serves little functional purpose ie body fat!

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A combined approach

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VO2 Max improvement for firefighters will most likely be best effected by a combination of fitness increase and body fat weight loss. 

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In this same example, a fitness increase of 10% would mean a raw score of 3762 ml. If the fire fighter lowered their body weight to 88 kgs from 95 kgs, then they would pass the firefighter fitness test with a score of 42.75 ml/kg/min. (3762/88=42.75).

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The combination approach is easier to achieve than fitness gain or body fat weight loss alone!

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In conclusion

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As the old adage goes; 'You cannot out-train a bad diet'! So if you're looking to make a difference to a firefighter's (or your own!) VO2 Max, be sure to keep stay accountable in both activity and nutrition!

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If you would like any advice on improving a firefighter's VO2 Max, then please send us a message! 

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