Physiology
The (Not So) Bleeding Obvious
Blood lactate, an analysis
Words: Dr Mark Homer
Helen Glover and Heather Stanning didn’t put a foot wrong over two Olympic cycles, on their way to consecutive gold medals in the W2-. Not in the eyes of this physiologist though. During a pre-2016 BBC documentary, one of the two referred to the ‘burn of lactic acid’ during the final stages of a race (or words to that effect). As the sports scientist working with the Great Britain team during this time, I was disappointed that I hadn’t managed to instruct the pair on the physiology of cellular respiration to a standard sufficient for them to understand how wrong this statement was.
In their defence, they were not the first to fall into the trap of blaming lactic acid (or blood lactate – more on this distinction later) for the pain they experienced during competition. The metabolite has long been associated with discomfort, the metallic taste in our mouths and, as one rower once explained to me, sepia coloured tunnel vision in the last 250m. This, however, is not the case. This article will attempt to explain why – in as simple terms as possible, before delving into how it can still be a useful tool to guide training as part of a structured rowing programme.
First, the science. Human beings have three main ‘systems’ for the production of energy, all of which are useful for rowing performance due to the high intensity nature of 2000 metre racing. The ATP-PC system yields a large amount of energy but for a very limited time – up to ten seconds of ‘full gas’ effort and is fuelled by stores of phosphocreatine within the muscle (hence its limited supply). This system is most utilised during the first and last ten strokes of a race. Secondly, anaerobic glycolysis involves the breakdown and conversion of the energy stored within carbohydrates (glucose) to useable energy for muscular contraction. Again, most useful during the start and end, but contributes throughout as a rowing race is completed at an intensity above that associated with maximal endurance capacity. Anaerobic glycolysis is a multi-step process and the first stage of our third energy system aerobic glycolysis, that relies on the presence of oxygen to produce large quantities of energy. Fuel permitting, at relatively low intensities, this system can provide us with the energy to exercise for extended periods.