Mens sana in corpore sano is a Latin phrase, translated as "a healthy mind in a healthy body". Another translation is “A sound mind in a sound body”. This is an adage promoted by the ancient Greeks and Romans centuries ago and current scientific evidence points toward this statement as being true. If we consider that regular bouts of exercise increase our blood flow and spur the body to create more capillaries to expand the circulatory system and increase the footprint of the reach of our total cardiovascular system. These benefits are undeniable. (Green & Daniel, 2014) Regular exercise contributes to brain growth factors. The data demonstrates that cognition, neurogenesis and vascular functions are all improved. (Powers & Howley, 2015) If we consider the hippocampus and brain structure, a steady exercise regimen has increased not only neurogenesis but angiogenesis. The incident of inflammation is also reduced by the central nervous system which leads to improved growth factor signaling. (Cotman, Berchtold & Christie, 2007)
Physical health and brain stimulation are not the only aspects of well being that benefit from regular exercise. When an individual exercises, the release of endorphins, the natural opiates produced in the pituitary gland of the brain, act to reduce pain and elevate mood. (Green, 2014) The term “runner’s high” resulted from the euphoric state that runners get when these endorphins are released. “And a lot of what we do know about exercise is gleaned from animal studies. But one potential cause that seems especially promising is related to neurogenesis, or the growth of new neurons in the brain, says Dr. Trivedi.” (Scobba, 2014) Even though the exact contributing factor is unknown, people that exercise tend to avoid depression in the first place and use exercise as a means to combat it as opposed to reliance on side effect laden pharmaceuticals. The post training physical and mental state is one that fitness enthusiasts crave and strive to achieve on a regular basis.
As people age, the benefits of physical fitness help to keep the brain stimulated and helps reduce and/or stave off the effects of Alzheimer’s, depression and lessen the severity of strokes and other types of brain injuries. People in good physical condition also require shorter recovery periods if and when illness occurs. In the case of the Mind-Body exercise of Tai Chi and Hatha Yoga, the combination of breathing, weight shifting and memorization of movement has multiple beneficial effects upon the physical, emotional and even spiritual well being of the participant. (Bryant & Green, 2012)
The relationship between force and speed is often misinterpreted.
FORCE: Strength or energy as an attribute of physical action or movement.
SPEED: The rate at which someone or something is able to move or operate.
Force and speed in regard to muscular contraction are primarily generated by Type llx muscle fibers, due the necessity of rapid excitation to generate the aforementioned fiber type. This occurs in the fast fibers because the sarcoplasmic reticulum in the fast fibers releases calcium at a faster rate. It’s also important to note that the fast fibers have a higher ATPase activity than that of the slow twitch fibers. The pulling of actin over the myosin molecule results in the shortening of the muscle (contraction) and thus generates force. The number and size of the motor units recruited are the main components that determine the force of a muscle contraction. The larger the motor unit the greater the potential force. The initial muscle fiber length plays a big role as well. There is an optimum length for a muscle fiber as it relates to the overlap of actin and myosin. If at rest the fiber is too long, the overlap between actin and myosin are limited and therefore there are less cross-bridges are able to attach. (Powers & Howley, 2015, pgs. 178, 179) Liken this to a fighter. There is an optimal size and weight for a fighter where force and speed maximize power. If this were not the case, then the largest person would be the best fighter. History has proven this not to be true. The proper mix of size and speed produce the best fighter.
Speed is also a function of the fast twitch muscle fibers. During high velocity movement, the actin-myosin filaments move past each other at a very fast rate. This lowers the number of cross-bridges that can be made, thus decreasing potential force. Fighters and punching power comes to mind. Faster striking does not necessarily yield more power. Yes, speed does add to power up to a certain point, but at some point, the speed of the punch diminishes the power of the strike. A fighter will use the quicker jab technique to set up the slower, more powerful cross in hopes of landing the knockout blow. Yes, the jab is faster, but not as powerful. Even though power equals force plus speed (velocity), to reach optimal power, there must be a balance. At some point, the peak force of a muscular contraction will be diminished as speed is increased. (Powers & Howley, 2015, pg. 181)
Control of heart rate and stroke volume are tantamount to body to maintain homeostasis and or achieve steady state during exercise. This is a fairly complex and involved task. Cardiac output is a function of heart rate multiplied by stroke volume or Q = HR x SV. Heart rate is regulated by the autonomic nervous system via a negative feedback loop garnering the information from the body’s increased demand of oxygen for the skeletal muscles. The parasympathetic system receives direction from the medulla oblongata to release acetylcholine that causes a decrease in activity of the SA and Av nodes. The heart rate is then lowered. The sympathetic nervous system is responsible for the increase in heart rate through the cardiac accelerator nerves. The fibers release norepinephrine and act upon the beta receptors. The system receives and interprets impulses from various parts of the circulatory system to accommodate changes in the specific parameters. (Powers & Howley, 2015, pg. 199)
Stroke volume is regulated by EDV (End Diastolic Volume), aortic blood pressure and the strength of ventricular contraction. An increase in aortic pressure results in a decrease in stroke volume, resulting in an inverse relationship. Another contributing factor to stroke volume is the release of nephrine and norepinephrine as inspired by the sympathetic nervous system. Other factors that regulate stroke volume during exercise are the venoconstriction that increases venous return, movement of the blood toward the heart from contraction of the skeletal muscles and increased depth of breath by the mechanical action of the respiratory pump. (Powers & Howley, 2015, pg. 200, 201)
The notion of a central command and the workings as described refer initiation via a motor signal developed within the higher levels of the brain. Although only theoretical at this point, the processes employed are based in sound science. This signal from the brain is created to drive motor signals. This signal is generated in less than once second and goes both directly to the skeletal muscle and to the cardiovascular control center that in turn forwards signals to the heart and blood vessels. The CV center also receives input from the pressure sensitive baroreceptors and the chemoreceptors as well as the mechanoreceptors of the skeletal muscle resulting in a finely tuned feedback system. What is originally initiated by the higher brain function in response to exercise is then manifested into a negative feedback system to control the function of the body in response to exercise.
Despite all of the studies and knowledge that has been garnered regarding human physiology in the past few centuries, there is still much to be learned. The advancements in training protocols, nutrition, discovery of new neural pathways and how to harness the power potential of humans in my estimation, is unlimited. Every year seems to shed light on a new subject to improve and enhance performance and health. It’s a great time to be in this field!
Bryant, Cedric X., Ph.D., FASM and Green, Daniel J. Essentials of Exercise Science for Fitness Professionals. (2010, 2011, 2012) American Council on Exercise. ISBN 9781890720315. 4851 Paramount Drive, San Diego, CA, 92123
Cotman, Carl W., Berchtold, Nicole C. and Christie, Lori-Ann. Exercise builds brain health: key roles in growth factor cascades and inflammation. TRENDS in
Neurosciences Vol.30 No.9. August 31, 2007.
Definitions of Force and Speed paraphrased from these sources:
Green , Daniel J., Project Editor. ACE, American Council on Exercise (2014). ISBN 978-1-890720-50-6. American Council on Exercise Personal Trainer Manual, Fifth Edition.
Powers, Scott K., and Howley, Edward T. Exercise Physiology, Theory of Application and Performance. 9th ed. New York: McGraw-Hill, 2015.
Scobba, Christa. Does Exercise Really Fight Depression? Men’s Health.
http://www.menshealth.com/health/how-exercise-fights-depression October 29, 2014