I had a spark today while working on my Exercise Physiology readings.  I am loving this section because it is all the microscopic things that my brain understand.  I dont know why but I “get” thinks if they are measured in microns and whatnot.  I can visulaize the actin filaments sliding from the myosin head binding so much better than I can understand a map or even which way is north or south at times.  But that is me and my brain- I like it and have a lot of fun with the way it works.

This is what I learned today:

I am studying the different types of muscle fibers.  I’m sure many of you know about slow twitch and fast twitch muscle fibers.  Slow twitch are generally associated with long distance runners whereas fast twitch are said to be those of sprinters.  Muscle fibers are categorized by their twitch speed as well as their metabolic capacity.

We all have both types of fibers in different proportions by our genetics.  There is proof that you can change your muscle fibers from one type to anther with very specific and intense training which change the metaobolic features (power capacity during aerobic and anaerobic stages) and/or the contractile features (twitch speed).

The spark moment came when I learned that adaptive responses of the fiber differs.  Atrophy from immobilization, say due to a broken leg, or are in extreme detraining, is well known however your slow twitch fibers tend to atrophy to a greater degree than your fast twitch.  Slow twitch fibers have more more associated capillaries and thus more blood flow.  I believe that this has something to do with it but have to still research more.  If this is true, I am extremely interested in knowing more in relation to Type II Diabetics.

Also with age, your fast and slow twich fibers start to look more like each other.  The fast become slower and the slow become faster.  This is called functional dedifferentation.  This is why the elderly have smaller range of functional capacities and reduced muscular abilities.  My question here is why?  Is it just age or is it inactivity?  If you took a muscular cross section of Jack Lelane’s thigh, would it look relatively the same as other 94 year olds?  (Hey, this could play in with my stats class and I could find if the comparison was statistically significant.)

I’ll research these and ask my prof and hopefully post up again.