uhh, forget what I said yesterday
Yesterday I told Jason I would never be able to run like I used to and that I had come to grips with it. Well, I have definitely come to grips with it but I went out today and ran a 5:58 mile at the end of my 3.5 mile run. Not bad for an aging wannabee athlete. No way I could hold that pace for 3.1 but still, it is my first sub-6 mile in 8 years. I ran a 5:24 in 1998 at the end of training for West Valley College soccer, right after my mission. The only other sub-6 mile that I remeber specifically recording was freshman year in high school, 1990-1991, when I ran a 5:01. I missed that sub-5 by a lousy 2 seconds. Not really important but it is hard to believe that there are high schoolers running close to the 4:00 mile.
I learned something interesting about heart rate, stroke volume and cardiac output this afternoon. Jason and I have often compared heart rates and it has always struck us as interesting that Jason's heart rate is consistently around 180 during regular runs and mine is usually around 150-160. Well, as it turns out, as we suspected, heart rate is mainly determined by genetics. Of course, if you want, I could drone on about specific cells and molecules which actually regulate the rythmic excitatory nature of cardiac musccle cells, but I digress. Anyway, the sympathetic and parasympathetic nervous systems can speed up and slow down the heart rate but it is largely controlled by predetermined genetics. I am getting to the point, I promise. So, when we excercize, our heart rate increases in an attempt to return blood more quickly to the lungs where it can be perfused with oxygen. But as Jason and I can both attest to, the heart rate can only increase so much, this is based on the rate at which Na and Ca can diffuse across the cell membrane, how fast the membrane can depolarize, and how fast the membrane can repolarize. So,...what allows for adaptation during exercize is an actual increase in stroke volume, meaning the amount of blood the heart can move with each cycle. This requires the heart muscle to increase in size with training so it can pump harder and more, meaning increased cardiac output. This is what varies in trained athletes, not how fast their heart can beat but how hard, and how much blood. This is actually the limiting factor, how much blood can be pumped through the lungw. The heart is the weak link in the chain. The lungs will accept up to 4x the amount of blood as at rest. Even during strenous exercize the amount of blood flowing to the lungs is only 2-2.5 xs more than as at rest. So, more speed workouts that challenge our hearts ability to pump enough blood, with adequate rest in between, goes a long way towards building that needed cardiac muscle.
Okay, so I ended up droning on and on anyway, but it was at least helpful to me, creating those neural pathways for my finals which are rapidly approaching.
I learned something interesting about heart rate, stroke volume and cardiac output this afternoon. Jason and I have often compared heart rates and it has always struck us as interesting that Jason's heart rate is consistently around 180 during regular runs and mine is usually around 150-160. Well, as it turns out, as we suspected, heart rate is mainly determined by genetics. Of course, if you want, I could drone on about specific cells and molecules which actually regulate the rythmic excitatory nature of cardiac musccle cells, but I digress. Anyway, the sympathetic and parasympathetic nervous systems can speed up and slow down the heart rate but it is largely controlled by predetermined genetics. I am getting to the point, I promise. So, when we excercize, our heart rate increases in an attempt to return blood more quickly to the lungs where it can be perfused with oxygen. But as Jason and I can both attest to, the heart rate can only increase so much, this is based on the rate at which Na and Ca can diffuse across the cell membrane, how fast the membrane can depolarize, and how fast the membrane can repolarize. So,...what allows for adaptation during exercize is an actual increase in stroke volume, meaning the amount of blood the heart can move with each cycle. This requires the heart muscle to increase in size with training so it can pump harder and more, meaning increased cardiac output. This is what varies in trained athletes, not how fast their heart can beat but how hard, and how much blood. This is actually the limiting factor, how much blood can be pumped through the lungw. The heart is the weak link in the chain. The lungs will accept up to 4x the amount of blood as at rest. Even during strenous exercize the amount of blood flowing to the lungs is only 2-2.5 xs more than as at rest. So, more speed workouts that challenge our hearts ability to pump enough blood, with adequate rest in between, goes a long way towards building that needed cardiac muscle.
Okay, so I ended up droning on and on anyway, but it was at least helpful to me, creating those neural pathways for my finals which are rapidly approaching.
posted by John J Cherry at 10:34 PM
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