Wednesday, May 15, 2013

Fun fact: Scientists have identified a protein important for endurance trained muscles

 Longitudinal cryosection of quadriceps from 7 month
old mice stained with Rabbit 2 polyclonal antibody
to dystrophin. Nuclei are stained with hematoxylin (blue).
 Cropped from doi:10.1371/journal.pone.0002604.g003
Exercise physiologists have long understood that strength training and endurance training result in muscles with very different capabilities. White muscle fibers are developed during strength training have a lower density of mitochondria and capillaries. They consume creatine phosphate to perform short-term anaerobic work that is capable of producing a high-level of power for a short amount of time. In contrast, red muscle fibers are developed during aerobic exercise, have a high density of mitochondria / capillaries and can consume tri-glycerides. They produce less power but can do so for extended periods of time. The classic examples of the two ends of the muscle type spectrum are the sprinter (white muscle) and the marathoner (red). Each has an abundance of the specialized muscle type that is best suited to their task.

In addition to consuming triglycerides, red muscle can also consume lactic acid. Lactic acid is produced during exercise, and its build up is associated with the fatigue we feel as a result of exercise. Scientists at the University of Basel have shown that a protein, PGC-1 a, exhibits increased expression in endurance trained muscle. 

To test the effects of PGC-1 a the scientists created mice that continuously expressed high levels of PGC-1 a. Endurance was monitored in mice for 1 hour on a treadmill. Mice that had previous endurance training were able to complete the tests without loss of performance and had low lactic acid levels while those without prior training had high lactic acid levels and were unable to complete test without loss of performance. Mice created that express PGC-1 a at high levels had low levels of lactic acid and were able to maintain performance until the end of training even though they not had previous endurance training.