Guess what readers? Your PE teachers, coaches, gym instructors, TV presenters & Colin Jackson are all wrong! It was yesterday evening around about 7 o clock when Colin Jackson was providing his glitzy overview of the physiological/biochemical underpinnings behind the 400 metres. A passing note from Colin went along the lines of ’….and that is when the lactic acid builds up, causing fatigue to set in’. Colin’s victimization of lactic acid angered me, prompting me to act, in order to defend and repair the broken reputation of our very own Mr Lactic acid. Everyone is entitled to a defence lawyer!
Since the early 1900′s it has been known that isolated muscles made to contract until fatigue accumulate lactic acid. In addition, if oxygen is present in recovery, lactic acid levels decline while glycogen concentration & contractile function are restored. Hence, the rise of the well publicised association between oxygen insufficiency, lactic acid and fatigue.
More recently, beneficial effects of lactate and lactate acidosis have been reported. For example, lactate can act as a substrate for energy production and is involved in cell-cell signalling. Further, lactic acid clearance during exercise has been thought to provide a beneficial, alkalising, effect on blood pH. Lactate transport across membrane barriers are now known to be facilitated by lactate transport proteins that co-transport lactate and hydrogen ions (hydrogen ions are a major cause of fatigue). More over, several lactate transporter isoforms are expressed in different tissues and occupy specific cells. Therefore, production and exchange of lactate infact has many beneficial roles, with some aiding the reversal of fatigue.
Results for Nielsen et al (2001) require us to once again re-evaluate our notions of lactate and its acidosis as some sort of fatigue inducing monster. Granted the study was performed on rats, Nielsen et al describe how muscular contractions cause both lactic acidosis and loss of intracellular potassium ions with accumulation of extracellular potassium ions. They observed that high potassium ion levels lead to a loss in muscular force. However, when lactic acid levels were high muscle fatigue wasn’t evident. In contrast, lactic acid actually countered the effects of potassium ions, that are observed with fatigue.
Such discoveries challenge the notion that lactic acid is the main cause of fatigue. I suggest we all stop victimising lactic acid and start ganging up on those nasty potassium ions and hydrogen ions instead! (Note – Science2Sport doesn’t promote victimising, bullying or any related behaviours).
‘Your honour, I propose my client, Mr Lactic Acid innocent’
Thanks for reading! Keep tuned for your next dose of Science2Sport! Coming up we have an exclusive interview with a GB handball player, courtesy of our very own guest blogger Mubz (follow on twitter @MubzKamaluddin).