The Physiology of Physical Training

Meera -   We're investigating what it takes to become an elite athlete.  As important as innate talent is, it's not enough to make it at the top.  A good understanding of how your body works and responds to exercise and to your particular sport is key.  Which is where the work of exercise physiologists like Chris Easton from Kingston University comes in...

Chris -   The typical things that we measure are things like heart rates, energy expenditure, the amount of oxygen that one uses during exercise, and lactate production, that kind of thing, to monitor physiological status, physical fitness, and then that can feed back into training to help improve performance.

Meera -   So people generally know that things like your recovery rate, so how well your heart rate perhaps recovers to normal after exercise, can be a good indicator of fitness.  But what's the step up for elite sport?  What are the type of things you have to monitor there?

Chris -   If you talk about endurance running in particular, one of the things that will be measured is something called running economy or running efficiency.  That is the amount of oxygen that one uses during a particular running speed, and that's really nice for tracking change before and after a training programme, before and after altitude acclimatisation for example. Other things, like something we call 'critical velocity' or 'critical power', that's the speed or the maximum speed or power that one can maintain indefinitely, have been shown to be quite good predictors of particularly endurance performance.

Other markers such as VO₂ max which is the aerobic capacity, the maximum amount of oxygen you can consume in a single minute, had been shown to be reasonable predictors in performance but less so than things like critical velocity.  In other sports, such as rowing, they'll look at things like the maximal power that can be generated.

Meera -   So training needs to be quite homed in on what a particular athlete is training in to really advance them to the elite level?

Chris -   Yes, absolutely.  The sports scientists, the coaches and nutrition staff tailor their programme specifically for those athletes in the different sports.

Meera -   Everybody at London 2012 is going to have their eyes firmly placed on Usain Bolt.  What is someone like his training schedule going to be to get him going as fast as possible?

Chris -   They tend to keep these things fairly secretive, but they'll be looking at things like the biomechanical assessment of his gait, the forces that he can produce, particularly out of the blocks, his reaction time and of course, the things that he'll be working on predominantly will be strength and speed.  Those are the two primary factors that will determine how fast that one could run 100 meters.

Meera -   And comparing sprinting to other sports, could you give some examples of sports that would have very different physiological factors monitored?

Chris -   Three good examples to compare will be something like running the marathon; in which world records are just over 2 hours for males, rowing; in which the time to complete the 2,000-meter track will be somewhere between 360-240 seconds.  In weightlifting, which only requires 1 to 2 seconds maximal effort.  

So, if you look at the endurance sports, the things that will be monitored and measured there will very much focus on the cardiovascular system, the aerobic energy systems, the VO₂ max, critical velocity, and something called the maximal lactic steady state, and lactic threshold measurements as well.  Whereas things like the rowing will look more at the maximum power that one can generate.  At weightlifting, they look at measurements of strength and of course, the amount of mass they have in comparison to fat.  So that's the lean muscle mass.  Those prompters will be fundamental in lifting heavy weights.

Meera -   So with the things like lactate for endurance sports, this is something you don't want to build up because it could hinder performance?

Chris -   Well, that is a little bit of a myth and in fact, lactate can be positive thing.  

Lactate is formed from glucose which breaks down to something called pyruvate and then is broken down further into lactate and that lactate can actually go in the reverse direction.  So that lactate can actually be used to generate substrate for exercise metabolism.  The thing that may have a negative impact is the hydrogen ions, the acid component that's produced along with the lactate - increased production of hydrogen ions, of acid, can reduce the efficiency of the muscle contractions.

Meera -   How would this be monitored and tweaked to improve performance?

Chris -   Well, one of the things you can measure is something called the lactate threshold and that is basically the point at which lactate begins to build up in the blood.  And what you're using lactate for is really a marker of the increase in hydrogen ions.  It's just that lactate is easier to measure.  You can measure it using portable systems taking a very small amount of capillary blood and additionally, we can also get an idea of the lactate threshold simply by measuring your expired air during exercise.  So, one of the consequences of an increased production of hydrogen ions is that the body's response to that is to produce something called sodium bicarbonate and that then goes through a reaction that, in the end, produces water and carbon dioxide.  So when we pick up that increase production of carbon dioxide, we know that that is going to be close to the point of what we call lactate threshold.

Meera -   Is this threshold something that can be moved?

Chris -   Absolutely, yes.  So, one of the common responses to a training programme is that you shift the lactate threshold to the right.  What that means is that the lactate threshold occurs at higher running speeds or higher cycling power, and clearly, that's going to be beneficial to the athlete because obviously, they can then maintain a higher speed or higher power before that build-up of lactate and hydrogen ions.

Meera -   Chris Easton from Kingston University who we'll be hearing from again later in the programme when we visit his lab to see just how an athlete's physiology is monitored.