Interval advise from Dr. Mirkin - Triathlon Week

sfricks · 07-21-2006, 05:10 AM

Dr. Gabe Mirkin's Fitness and Health e-Zine
July 23, 2006

Intervals Teach Your Muscles to Use Lactic Acid

You exercise so intensely that your muscles burn and
you gasp for breath. Then you slow down for a minute or two,
catch your breath, and then go very fast again. This training
technique has been used in all endurance sports since the
1920's. Now George Brooks of the University of California at
Berkeley has shown why interval training makes you a better
athlete (American Journal of Physiology-Endocrinology and
Metabolism, June 2006).
Inside each muscle cell are mitochondria, the little
furnaces that burn fuel for energy. A major fuel for your muscles
during exercise is the sugar, glucose. In a series of chemical
reactions, glucose is broken down step by step, with each step
releasing energy. When enough oxygen is available, the glucose
releases all of its energy until only carbon dioxide and water
remain; these are blown off through your lungs. However, if not
enough oxygen is available, the chemical reactions stop at lactic
acid which accumulates in the muscles and spills over into the
bloodstream. Lactic acid makes muscles acidic and causes a
burning feeling. This recent research shows that lactic acid is the
most efficient source of energy for muscles. Anything that helps
muscles to break down lactic acid faster will make you a better
athlete because it will increase your endurance and allow you to
move faster when you are tired.
Since lactic acid is burned for energy in the mitochondria,
anything that enlarges the mitochondria builds a bigger furnace
and helps to increase endurance. Lactic acid is carried from the
cells into the mitochondria by special proteins called lactate
transporter molecules, so anything that increases these
molecules will build endurance. An enzyme called lactic acid
dehydrogenase is needed to start the reaction, so anything that
increases this enzyme will also help. Interval training does all
three: it enlarges the furnace (mitochondria), increases lactic acid
transporter molecules, and increases the amount of lactic acid
dehydrogenase.