The Physiological Benefits of Exercise

​Exercise is a a pretty fabulous activity for improving the functioning of our bodies. It reduces stress, helps with weight loss, and can make other physical activities easier. It can reduce the risk of cardiovascular disease and cancer. 

Exercise can also improve blood lipid profiles by lowering total cholesterol while elevating HDLs or the "good cholesterol". Resistance training can provide protection against sarcopenia (the loss of muscle mass that accompanies aging), osteoporosis, and type II diabetes.

But what I'd like to focus on today are the long term effects of exercise training on bioenergetic pathways, myofibers, the pulmonary system, the cardiovascular system, and blood composition.

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Bioenergetic Pathways
As defined by the ACSM, bioenergetics refers to the body's ability to acquire, convert, store, and utilize energy. This is the system that uses ATP into ADP, and explains aerobic and anaerobic energy pathways.
And guess what? There are several improvements to this system thanks to exercise:

• Our bodies can produce more ATP, meaning that in effect we have more energy available
• More mitochondria: the powerhouses of energy within every cell
• More fats and carbohydrates are stored in these energy pathways, another way in which we can effectively have more energy available.

Myofibers
Ok, I'm just being fancy now. Myofibers are skeletal muscles, which means just about every major muscle one might use when exercising. Exercise causes two impressive effects on skeletal muscles:

• Type IIb fibers convert to Type IIA. Endurance and resistance training both cause this. This means that fibers convert from only being able to use ATP for fast twitch use to hybrid muscle fibers able to use both aerobic and anaerobic pathways with medium twitch speeds. This means greater endurance.
• Muscular hypertrophy. Fun fact: When your muscles get bigger (and stronger), it is the same muscle fibers getting bigger. We always have the same number of muscle fibers in any given muscle regardless of exercise.

Pulmonary System
The pulmonary system is the lungs. 

• Exercise effectively means greater breathing capacity. 
• The volume of air breathed in or out rises to as much as 20-25 times higher during maximal exercise. Keep in mind some of this increase is due to breathing faster too, but not all!
• VO2 Max is improved from 55% to 80-85% of exercise intensity. This is the threshold of exercise we can do before ATP demand by working muscles can no longer be met by aerobic metabolism and the anaerobic pathways must be recruited as well. This also matters because blood lactate levels and muscle fatigue start rising once a person is using anaerobic energetic pathways more. Note: lactate does not cause fatigue, but it is highly correlated with it.

Cardiovascular System
This system refers to the heart and blood vessels throughout our body.

• At maximal effort, pumping capacity can increase by 5 to 6 times versus at rest
• At up to 50% of VO2 Max,  increases in pumping capacity are accounted solely by stroke volume
• Lower blood pressure
• Maximum heart rate is not effected by exercise, but well trained individuals have lower resting heart rates due to higher stroke volumes
• During intense exercise, cardiac output to muscles rises from 20% at rest to about 85%. And our bodies can get better at this with exercise training!
• Exercise leads to more capillaries delivering oxygen and other nutrients to skeletal muscles

Blood

• Regular exercise leads to greater oxygen carrying capacity due to an increase in red blood cells
• Exercise leads to having more blood! In addition to red blood cells, another major adaptation is far more blood plasma to the point of a decrease in the ratio of red blood cells to overall blood volume. This has been termed "runner's anemia", but don't worry: it's not a negative adaptation.
• More plasma also helps lead to higher heart  stroke volume, lower heart rate with less increase in heart rate during exercise, and higher cardiac output.

Thanks for reading, and happy running!


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