The importance of exercise to health and well-being was already known in Ancient Greece. Hippocrates (460–270 BCE) has been quoted: “Eating alone is not enough for health, there must also be exercise.” During the Renaissance, the significance of the individual’s own actions on his or her health became of interest. Health was no longer in the hands of God alone. In his 1553 work, Book of Bodily Exercise Spanish doctor, Christóbal Méndez described exercise as “blessed medicine” for the health of individuals. This medical point of view became more and more prevalent entering the industrial era. In his 1769 book, Domestic Medicine, Scottish doctor, William Buchan indicated that exercise alone could prevent many illnesses that were difficult to treat. French doctor, Clement Tissot, on the other hand, highlighted the importance of incidental exercise. From the late 19th century exercise was introduced into school curricula. The significance of exercise to health and general well- being was understood rather early on. Proper scientific studies on the subject matter did not appear until the turn of the 20th century. The American Journal of Physiology was first published, and in 1920, physiology professor August Krogh won the Nobel Prize in medicine, having discovered the mechanism that regulates blood flow in the muscles. Research on the health benefits of exercise really took off in the 1950s when The Lancet published a groundbreaking study on the positive impact of exercise on the prevention of coronary heart disease. The World Health Organization (WHO) has created global recommendations on physical activity for health which are based on extensive research. For individuals aged between 18 and 64 physical activity includes recreational or leisure-time physical activity, transportation, occupational, household chores, games, sports or planned exercise, in the context of daily, family, and community activities. Improve endurance fitness by exercising several days per week for a minimum combined duration of 2 hours 30 minutes (brisk exercise) or 1 hour 15 minutes (strenuous exercise). In addition, improve muscular fitness and proper form at least twice per week. Additional health benefits may be achieved with five hours of endurance exercise per week.
Based on meta-analysis studies, the most effective way to encourage people to exercise is behavioral intervention rather than cognitive intervention.5 6 In other words, people respond more easily to concrete experiences compared to intellectual facts. Examples of behavioral intervention include setting goals, self-monitoring and measuring, feedback systems, exercise prescriptions, and various challenges.
EXERCISE AND THE BRAIN
As the saying goes, sound mind in a sound body. Most people are aware that exercise makes us feel better. Previously it was believed that this was due to physiological factors only. However, recent studies have found that exercise improves our brain function. According to the latest meta-analyses, exercise increases the amount of gray matter, particularly in areas crucial for memory functions such as the orbitofrontal cortex and the hippocampus.7
In today’s technology-oriented world, we have become alienated from our natural need to move, hunt, and gather food. In terms of survival, immaterial things have replaced physical effort. It is tragic that it is precisely the lack of bodily exercise that makes us unable to deal with the challenges that cause an ever-growing amount of stress on our minds.
Of all the medication used to treat people, the share of psychiatric medication has also grown dramatically (see the Mind chapter of the Biohacker’s Handbook for more details). In 2000, scientists at Duke University published
a study that compared the effects of the antidepressant sertraline as well as exercise on cases of severe depression over the course of 10 months. Regular exercise was found to be more effective in treating depression compared to medication.
A comprehensive 2014 meta-analysis found physical exercise to have a significant positive impact on various levels of depression. Exercise is recommended as a treatment for mild or moderate depression.9 According to meta-analyses, regular exercise also reduces stress which is a predisposing factor for various illnesses. Aerobic exercise in particular has also been found to boost the production of endogenous cannabinoids (anandamide), opioids (beta-endorphin), and phenylethylamine. These chemicals probably contribute to the pleasurable experience of a runner’s high. In his book Spark – The Revolutionary New Science of Exercise and the Brain, John J. Ratey, an associate clinical professor of psychiatry at Harvard Medical School, discusses in depth the impact of exercise on the brain and the mind. According to Ratey, exercise has been found to increase
the long-term potentiation of nerve cells, improving the ability to learn and memorize. Similarly, BDNF protein (Brain Derived Neurotrophic Factor) levels have been found to increase after physical activity. This has a positive impact on cognitive functions. The most significant increase of BDNF in the blood was found after aerobic exercise and particularly high intensity activity.
The effects of strength training on BDNF have been inconclusive. The positive impact of strength training on the brain function is mainly due to other mechanisms. For elderly people in particular, performing strength training at least twice weekly increases the functional plasticity of the brain. A study published in 2014 found that just one 20-minute strength training session significantly improves episodic memory. Several studies have found that exercise reduces the occurrence of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease as well as assists in the treatment of these diseases. For example, dance has been used to significantly improve the motor skills and quality of life of patients suffering from Parkinson’s disease. The development of a child’s brain, nervous system, and cognitive function to their full potential also requires regular and varied physical activity.
THE INDIVIDUALITY OF EXERCISE
A basketball player more than two meters (6 ft 7 inches) in height is unlikely to do well in ski jumping. Conversely, a lean marathon runner will not be a successful weightlifter. Humankind represents a diversity of sizes, strengths and physical characteristics. It is therefore worthwhile to carefully consider the suitability of each type of exercise – what is my body suited for and what are my personal preferences? There are individual differences in recovery, too. Generally speaking, women need more time to recover compared to men, and as we age the recovery period grows longer. Because of this, a customized training program and listening to one’s own body are key in maintaining and developing the enjoyment of exercise. Aside from sex and age, other individual factors include one’s previous fitness level, training background, and the development level of various physical characteristics.
THE SOCIAL DIMENSIONS OF EXERCISE
Regular exercise affects the social behavior of the individual. People who exercise regularly generally have healthier emotional lives and more confidence. For children in particular, physical activity has been found to improve social skills. Exercising in a group also invokes team spirit and may improve communication skills. It is fascinating to note that rowers, for example, have a higher tolerance of pain in a group setting than when training alone. Indeed, team sports appear to beat individual sports in developing psychosocial skills and health. In addition to exercise, spectator sports have also been found to have health benefits. Intensive sports moments experienced and shared with others may strengthen social relationships. The social impact of spectator sports is much greater for men compared to women. Many people also consider watching sports an aesthetic experience which, like art, may activate areas of the brain to do with aesthetic pleasure.
NEVER STOP PLAYING
Exercise should not be thought of as a chore or a compulsory item to check off to promote health. Playful movement is normal and characteristic of children but adults often completely forget about it. We don’t stop playing because we grow old. We grow old because we stop playing. Exercise could be thought of as natural, playful movement that takes place throughout the day, without forced performances, grimacing, and exhaustion. The saying “grease the groove” (GTG)33 refers to short, almost playful exercises conducted throughout the day that place significantly less strain on the nervous system whilst yielding results along with being fun. For example, you could do a few pull-ups each time you pass under a scaffold. You could also break up the working day with intermittent push-ups, squat jumps or dashes in the stairs. Lastly, nature and the outdoors offer endless possibilities. 72-year-old Stephen Jepson has taken the concept of playfulness in exercise and created a philosophy called Never Leave the Playground. Jepson rides a unicycle, balances, juggles, and walks a tightrope. His philosophy is constant movement regardless of the surroundings.
ANATOMY AND PHYSIOLOGY
The cardiovascular and circulatory system consists of the heart, arteries, veins, capillaries, and lymphatic vessels. Its function is to carry blood to various parts of the body. The heart acts like a pump, pushing blood from veins into arteries and capillaries. Biochemical reactions and substance exchange between blood and cells occur in capillaries from which “used” blood travels into the heart through veins. The vessels of the lymphatic system absorb the interstitial fluid from tissues back into veins. The purpose of the circulatory system is to deliver oxygen and nutrients to cells and to remove waste products from them. Hormones secreted by endocrine glands are also delivered throughout the body by the circulatory system. In addition, it serves as a part of the body’s temperature control system.
The heart is located inside the chest, in the mediastinum behind the sternum. The heart is formed of a muscular wall consisting of three layers, and inner cavities. The outermost layer (pericardium) is a double-walled sac around the heart. Between the layers of the sac, there is the pericardial cavity, filled with liquid. This reduces friction caused by the heart beating. The inner layer of the sac is attached to the middle layer of cardiac muscle tissue (myocardium). Conversely, the outer layer (parietal pericardium) is attached to the surrounding tissue. Inside the cardiac muscle, there is the endocarium layer, which is in direct contact with the blood that flows through the heart. The heart has four chambers: the right and left atrium and the right and left ventricle. In addition, there are four valves. Two of these are located between the atria and the ventricles (atrioventricular valves) and the other two between the ventricles and the arteries (semilunar valves). Blood from the body flows from the veins into the atria. From there, the blood moves into the ventricles and, as the heart contracts, into the arteries. Low-oxygen blood travels via the superior and inferior vena cava into the right atrium, from which it is pumped via the right ventricle into the lungs. Oxygenated blood returns from the lungs into the left atrium, from which it is pumped via the left ventricle throughout the body. The heart has a separate circulatory system that secures its oxygen supply. It involves three coronary arteries (one on the right and two on the left) and their branches. Coronary arteries are attached to the base of the aorta where they receive blood rich in oxygen. A clot in a single artery branch may cause lack of oxygen in the cardiac muscle, leading to coronary thrombosis. The low-oxygen blood used by the cardiac muscle travels via the veins into the right atrium to be recycled.
REGULATION OF THE HEART FUNCTION
Heart rate is regulated by the autonomic nervous system
as well as signals relayed by hormones. Signals that slow the heart rate (parasympathetic nervous system) are sent by the brainstem via the vagus nerve. Conversely, signals that increase the heart rate are sent by the nerve fibers of the sympathetic nervous system. For example, neurotransmitters (adrenaline and noradrenaline) secreted by the adrenal gland medulla as a reaction to stress boost the activation of the sympathetic nervous system, increasing the heart rate. Relaxation activates parasympathetic nerve impulses and the heart rate slows down due to acetylcholine. Heart rate can be regulated through breathing: inhaling momentarily increases the heart rate whilst exhaling reduces it. This phenomenon is called heart rate variability (HRV).
Heart rate and blood pressure are also regulated by the baroreflex. For example, blood pressure in the upper torso and head increase when lying down, causing a signal to be sent to the brain via the baroreceptors in the neck and the aortic arch. The vasomotor center (center of neural circulatory control) located in the medulla oblongata of the brainstem sends a signal to the heart, reducing the heart rate and cardiac contractive force. Conversely, when standing up rapidly, the heart rate and cardiac contractive force increase. Muscle contractions also increase the heart rate. Proprio- ceptors are sensory receptors located in muscles, joint capsules and tendons that assess the nature of movement. In turn, they are in touch with the vasomotor center. Increased proprioceptor activity increases the heart rate and circulation.
The flow volume of the microcirculation remains constant regardless of pressure changes in the systemic circulation. This is due to the arteriole wall muscles contracting and relaxing according to various stimuli. The precise microcirculation system secures sufficient nutrient and oxygen delivery to the internal organs regardless of any changes taking place in the body. There are many different mechanisms involved in the regulation of the microcirculation. These include metabolic, electrical, neural and mechanical (muscle-based) regulation. For example, venules provide feedback to arterioles about the metabolic state of tissues, and during exertion, the arterioles in the muscles expand to deliver more oxygen to the tissues. The efficiency and control of the microcirculation often deteriorate with age. Factors contributing to this include smoking, alcohol consumption, poor diet, stress, sleep deprivation, air pollution, environmental pollution and the lack of exercise.
Capillaries are in direct contact with tissues, making biochemical exchange between interstitial fluid and blood possible. Capillary walls are permeable enough for most substances in the blood to freely pass into the interstitial fluid.43 Only proteins fail to pass though the capillary walls. This is why molecules attached to carrier proteins (such as hormones) are not effective at tissue level. Three metabolic mechanisms are currently known: diffusion, bulk flow and transcytosis.
• Diffusion causes oxygen, glucose, amino acids, etc. to flow from capillaries into interstitial fluid. Metabolic waste flows from interstitial fluid back into capillaries.
• In bulk flow, the exchange occurs via small fat molecules. The flow of substances from the capillaries into the interstitial fluid is called filtration. Conversely, reabsorption refers to the flow of substances from the interstitial fluid into the circulation.
• In transcytosis, large molecules such as proteins, hormones and immuno- globulins move into the interstitial fluid with the help of vesicles via the endothelial cells of the capillaries. The transfer occurs through exocytosis: the fluid sac surrounding the protein merges with the cell membrane, moving the protein into the interstitial fluid.
LYMPHATIC SYSTEM AND CIRCULATION
The lymphatic system is part of the circulation. It consists of a comprehensive network of lymphatic vessels, lymph nodes and other lymphoid tissues, the spleen and the thymus. The lymphatic vessels circulate lymph, which has an important role in fluid balance regulation, immune system function, and carrying fatty acids. Lymphatic circulation returns the fluid absorbed from the microcirculation back into circulation. Lymphatic circulation also carries the fat absorbed from the intestine into circulation. For the circulation of lymph, moving the entire body is important. Unlike blood circulation, lymphatic circulation does not have a heart-like pump. Instead, lymph circulates with the help of voluntary muscles, respiratory movements and the smooth wall muscles of the lymphatic vessels.
The consistency of lymph resembles that of blood plasma. It contains lymphocytes and a small amount of other white blood cells. In addition to these, lymph consists of metabolic and cellular waste, bacteria and proteins.
LYMPH NODES ARE THE QUIET WATCHMEN OF THE BODY
Lymphocytes are an important part of the immune system. They are produced in the bone marrow and matured either in the thymus (T cells) or the marrow (B cells). Mature lymphocytes move into the spleen, lymph nodes and other lymphoid tissues such as tonsils and adenoids, lymphoid tissue of the intestine, and the walls of respiratory and urinary tracts.46
An individual has approximately 500–600 lymph nodes, most of which are clustered in the intestine, armpits, neck, and groin. The size of lymph nodes can vary dramatically (diameter approximately 1–20 millimeters). The size varies due to infections, possible tumors in the body, etc.
Several lymphatic vessels lead to the lymph node, bringing in lymph from the surrounding tissue. The medullary sinuses of the lymph node contain macrophages that consume foreign substances found in the lymph, particularly various pathogens. The function of the macrophages is a part of cell-mediated immunity. The medullary sinuses converge at the hilum where the lymph exits via lymphatic vessels to be used again.
The lungs are the body’s main respiratory organ. Humans have two lungs, one on each side of the body. The right lung consists of three lobes, while the left lung has only two. Each lung is fed by a main bronchus. These branch out into lesser bronchi. The lungs are located in the chest cavity, on either side of the heart in front of the spine. On the front side, they are protected by the ribs. Below the lungs, there is the diaphragm, one of the main muscles of respiration. The lungs are estimated to contain up to 2400 kilometers (1490 miles) of airways and approximately 400 million alveoli. Due to the enormous number of alveoli, the respiratory surface of an adult human measures 30–50 square meters. The lungs are surrounded by the pleural cavity which consists of two layers (parietal pleura and visceral pleura) and the fluid between these layers. Fluid exchange is controlled by the circulation in the intercostal arteries and the lymphatic system. Some illnesses (such as liver cirrhosis, pulmonary embolism) or trauma may cause fluid (pleurisy) or air (pneumothorax) to collect in the lungs, making breathing difficult. The lungs have a dedicated circulation in which low-oxygen blood is oxygenated for use by the body. Pulmonary circulation is discussed in more detail in the section “Circulation.”
RESPIRATION AND THE ALVEOLI
Respiration refers to the mechanical and biochemical transfer of oxygen (O2) from the air into cells, and conversely, the transfer of carbon dioxide (CO2) from cells into the air. Cellular respiration is discussed in more detail in section “Metabolism – the cornerstone of energetic life.”
Respiration is regulated by the respiratory center located in the medulla oblongata. Its functions are influenced by the levels of carbon dioxide, oxygen and hydrogen in the blood. This is called humoral regulation. Corresponding nervous regulatory mechanisms include the mechanical movements of the chest, stimuli from the air entering the lungs, signals sent by proprioceptors, and changes in body temperature. Pain also has a significant effect on respiration. Respiration may also be voluntarily regulated for example through hyperventilation (breathing very fast).
Motor units can be divided into groups based on the contractility and endurance of the muscle cells. Motor units are categorized into slow-twitch (S) or fast-twitch (F) units. Fast units are further divided into three groups: fatigue- resistant (FR), fatigue-intermediate (Fint) and fatigable (FF).64Motor units are also activated in this order based on the force required by the movement. The fastest motor units are activated in maximal movement such as changes of direction and jumps.
The connection point between muscle and tendon is called a myotendinous junction. The force generated by muscle contraction is transmitted via the tendon to the skeleton to be released for example as limb movement. The junction tendons consist of dense collagen fibers and fibrocytes (the main cell type of connective tissue). At the tendon end of the muscle, the muscle fibers become thinner and their filaments overlap with the collagen fibers of the tendon. Due to their structure, myotendinous junctions are prone
to injury. In the event of muscle or tendon injury, the myotendinous junction is typically the first casualty.67 Injuries to the myotendinous junction may be prevented by improving balance and body proprioseptics, strengthening collagen fibers and improving general muscular strength. Good joint mobility and thorough pre-exercise warm-ups also provide protection from injury.
MUSCLE SPINDLE – A SENSORY RECEPTOR IN THE MUSCLE
A muscle spindle is a sensory receptor (stretch receptor or proprioceptor) located within the muscle. It detects changes in the length of the muscle and transmits this information to the central nervous system. A muscle spindle contains several sensory nerve terminals. Of these, type Ia nerve terminals (afferent) react to rapid changes in muscle length. Type II nerve terminals transmit information about the muscle length and activate other motor nerves. Structurally very thin type III and IV fibers transmit information about various sensations such as pain, changes in temperature and chemical sensations. Muscle spindles are plentiful in the neck area muscles which are important for adjusting the position of the head and the rest of the body. Facial muscles also contain plenty of muscle spindles which are consistent with the fine motor function requirements of facial movements and eating. For example, the number of motor spindles in the neck and face area is many times greater compared to that of the bicep.
METABOLISM – THE CORNERSTONE OF ENERGETIC LIFE
Metabolism is the continuous vital process of breaking down organic matter and forming new substances within the tissues of the body. The word is derived from the Greek word metabolemeaning “change.” Indeed, the body is in a constant state of change. The breakdown process is called catabolism whereas anabolism is the process by which living organisms synthesize new molecules. Metabolic reactions are affected by several reaction-accelerating body enzymes (biocatalysts). In addition, metabolism is regulated by hormones, various growth factors, vitamins, minerals, and the autonomic nervous system. Various chemical reactions form so-called metabolic pathways. Energy metabolism in particular is relevant to exercise. Metabolic pathways are crucial for the maintenance of homeostasis (the equilibrium of the body). The long-term imbalance of metabolic pathways may lead to various metabolic disorders. Genetic hereditary enzyme dysfunctions may also cause innate metabolic disorders (for example, a mutation in the MTHFR gene may cause an increased level of homocysteine and therefore an increased risk of cerebrovascular disorders). Examples of metabolism include the breaking down of carbohydrates, proteins and fats into energy (the citric acid cycle), the removal of superfluous ammonia through urine (the urea cycle) and the breakdown and transfer of various chemicals. The metabolic pathway that was first discovered was glycolysis in which glucose is broken down into pyruvate supplying energy (ATP and NADH) to cells.
AEROBIC ENERGY SYSTEM
The aerobic (requiring oxygen) metabolic process is also called cellular respiration. The processes involved in the aerobic energy system (cellular respiration) are glycolysis, pyruvate oxidation, the citric acid cycle and the electron transport chain. In practice, various cascades use glucose and oxygen to produce ATP (adenosine triphosphate) that acts as an energy source. Byproducts of these processes include carbon dioxide and water.
The first metabolic phase, glycolysis, takes place in the cytoplasm. When glycolysis occurs under aerobic conditions, a glucose molecule is broken down into pyruvate, simultaneously producing two ATP molecules and two NADH molecules. Glycolysis also takes place under anaerobic conditions; however, the end result in this case is lactate, or lactic acid (see section “Anaerobic energy system”).
CITRIC ACID CYCLE
The citric acid cycle, or Krebs cycle (named after the Nobel prize winner Hans Adolf Krebs who discovered it), takes place in cell mitochondria.74 The primary metabolic compound of the citric acid cycle is acetic acid (acetyl coenzyme A) produced from fatty acids, carbohydrates and proteins. The various reactions of the citric acid cycle (see image) form hydrogen ions and electrons which are then transferred to the inner mitochondrial membrane for oxidative phosphorylation (binding energy to ATP molecules
through oxidation) and the electron transport chain. The reaction releases NADH and small amounts of ATP and carbon dioxide.
The citric acid cycle involves ten steps, each of them affected by B vitamins and certain minerals such as magnesium and iron as well as the liver’s main antioxidant, glutathione. The reactions are inhibited by heavy metals such as mercury, arsenic and aluminum.
Most of the energy generated during the citric acid cycle is captured by the energy-rich NADH molecules. For each acetyl coenzyme A molecule, three NADH molecules are generated and then used for energy in the reaction that follows (oxidative phosphorylation). The regulation of the citric acid cycle is determined by the availability of various amino acids as well as feedback inhibition (for example, if too much NADH is produced, several enzymes of the citric acid cycle are inhibited, slowing down reactions).
Oxaloacetate acts as a compound used to fulfill a sudden need to produce energy (for instance, in the brain or muscles). Taking an oxaloacetate supplement may therefore be useful, and it may even boost the regeneration of mitochondria in the brain, reduce silent inflammation in the body and increase the number of nerve cells. To put it simply, the body incorporates ingenious systems that convert consumed food into electrons which are used as energy for various needs.
Oxidative phosphorylation consists of two parts: the electron transport chain and ATP synthase. Oxidative phosphorylation produces most of the energy generated in aerobic conditions (ATP). It is a continuation of the citric acid cycle. In the electron transport chain, hydrogen ions (H+) are released into the mitochondrial intermembrane space. Through ATP synthase, the hydrogen ions released from the intermembrane space move back into the mitochondrion. Using the energy released in the process, ATP synthase converts the ADP used for energy into ATP again. Ubiquinone (coenzyme Q10) acts as a contributor to the electron transport chain. It has been used for decades as a dietary supplement. Low cellular ubiquinone levels may be a predisposing factor for various illnesses due to insufficient aerobic energy production in the cells. In addition, the use of cholesterol medication (statins) has been found to be a contributive factor to ubiquinone deficiency.
BETA-OXIDATION OF FATTY ACIDS
Fatty acids broken down in the digestive system are used for energy in the mitochondria. In this reaction (called beta-oxidation), the fatty acids are activated by being bound to coenzyme A. The result is acetyl coenzyme A (see above) which is used for energy production in the citric acid cycle. The oxidation of long-chain fatty acids requires carnitine acyl transferases in which the fatty acids are transported from the cytoplasm into the mitochondrion. Such transfer of short- and medium-chain fatty acids into mitochondria is unnecessary as they move there by diffusion.
ANAEROBIC ENERGY SYSTEM
The term “anaerobic” refers to reactions that happen without oxygen present. The anaerobic energy system is needed in circumstances in which oxygen is not immediately available in the quantities required, for example during high-intensity sports activity. In the anaerobic energy system, ATP is produced by breaking down glucose polymers (glycogens) stored in muscles and the liver as well as by utilizing the free ATP molecules immediately available in the muscle cells.
During anaerobic glycolysis, glucose is broken down into pyruvate which is then converted into lactic acid (lactate) during the lactic acid fermentation process. The lactic acid fermentation takes place when oxygen is not available for energy production.
CREATINE PHOSPHATE SYSTEM
The creatine phosphate system is one of the main energy sources for muscles. It is estimated that approximately 95 % of the body’s creatine is located in the skeletal muscles. Creatine phosphate (phosphocreatine) is synthesized in the liver from creatine and phosphate (from ATP; see above). Red meat is a source of creatine, and it can also be synthesized from amino acids (arginine and glysine). Creatine is used as a dietary supplement (creatine monohydrate) as it significantly increases force generation in the skeletal muscles. Creatine is formed and recycled in the creatine phosphate shuttle (see image). The shuttle transports high-energy ATP molecule phosphate groups from mitochondria to myofibrils (muscle fibers), forming phosphocreatine (creatine phosphate) through creatine kinase. It is used by the muscles for fast energy production. Unused creatine is transported by the same shuttle into mitochondria where it is synthesized into creatine phosphate. Used phosphocreatine forms creatinine which exits the body in urine via the kidneys.
When determining the filtering capability of the kidneys, it is useful to measure the blood creatinine level. The higher a person’s muscle mass, the higher the volume of creatinine secreted. Because of this, the muscle creatine level and blood creatinine level of men are usually higher than those of women.
THE BODY’S MAIN ENERGY STORAGE SYSTEMS
The body utilizes two different types of energy storage. Energy-dense molecules such as glycogen (sugar) and triglycerides (fat) are stored in the liver, muscles and adipose tissue (fat; triglycerides only). Another important type of energy storage is comprised of the electrochemical ions located between cell membranes. Due to its complex nature, the latter is not covered here.
Glycogen is a large-size molecule formed of several (up to 30,000) glucose molecules. Glycogen is stored in the liver (10 % of the weight), muscle cells (2 % of the weight) and, to a lesser extent, red blood cells. In addition to glucose, glycogen binds triple the amount of water. Because of this, a person’s body weight may fluctuate by several kilograms within a 24-hour period depending on the fill level of the glycogen reserves. The glycogen storage in the liver acts as an energy reserve for the entire body’s energy production needs, and those of the central nervous system in particular. The glycogen storage in the muscles is only used for the energy production of muscle cells. The amount of glycogen present is determined by physical exercise, the basal metabolic rate and eating habits.
The glycogen reserves are especially important for the regulation of blood sugar between meals and during intensive exercise. Glucose may also be used for energy under anaerobic conditions. Conversely, fatty acids are broken down into energy only under aerobic conditions. The brain needs a steady level of glucose although it is able to utilize, for example, the ketone bodies produced by the liver during fasting. A metabolically active glycogen breakdown product is glucose 6-phosphate in which the glucose molecule binds with one phosphate group. It may be used for energy in a muscle under either aerobic or anaerobic conditions, utilized via the liver as glucose elsewhere in the body or converted into ribose and NADPH for use in various tissues (for example in the adrenal gland, red blood cells, mammary glands and the fat cells in the liver).
Adipose tissue (fat) is the body’s main long-term energy storage system. In addition to fat cells (adipocytes), it consists of connective tissue cells and vascular endothelial cells. Fat cells contain a lipid droplet consisting of triglycerides and glycerol. Adipose tissue is located under the skin (subcutaneous adipose tissue), in bone marrow, between muscles, around internal organs (visceral fat) and in the breast tissue. Visceral fat is particularly detrimental to health as it increases the risk of type 2 diabetes, coronary heart disease and various inflammatory diseases. Adipose tissue is also a hormonally active (endocrine) organ. Adipose tissue produces for example, leptin, adiponectin and resistin that regulate the energy metabolism and body weight. Adipose tissue is ever changing, storing or breaking down free fatty acids for use by the body. The process of breaking down adipose tissue into energy is called lipolysis. In lipolysis, triglycerides of the adipose tissue are oxidized by lipase and triglyceride lipase into free fatty acids and glycerol. Fatty acids are used for energy in the muscles, liver and heart; glycerol is mainly used in the liver.
Conversely, insulin inhibits lipolysis. If the body’s stored insulin levels are consistently elevated, the fatty acids circulating in the blood are stored in the adipose tissue. This is called lipogenesis. In particular, the secretion of insulin is stimulated by high blood sugar levels and a carbohydrate-rich diet. An abundant protein intake also increases insulin secretion.
METHODS TO IMPROVE PHYSICAL PERFORMANCE
Endurance refers to the body’s ability to withstand fatigue and remain active whilst under physical strain. Endurance depends largely on the performance of the respiratory and circulatory system as well as the energy management in the muscles, i.e. their ability to convert fat and carbohydrates into energy. This is determined by the number of mitochondria, the number of capillaries in the muscles as well as various metabolic pathways (glycolysis, Krebs cycle and oxidative phosphorylation).
Endurance exercise is generally recommended as the basis of all healthy physical exercise. The recommendation is to exercise for at least 2 hours and 30 minutes per week (the common suggestion is five times per week, for at least 30 minutes each time). Some activities considered to fall under endurance exercise include walking, cycling, swimming, hiking and even heavier house and yard work. The intensity varies depending on the individual’s fitness level. To make significant developments in one’s endurance fitness, it is usually necessary to include activities more arduous than walking, for example running, cross-country skiing, fast-paced cycling or various ball games. In terms of group exercise, various aerobics, dance, and cross-training classes are popular.
Endurance exercise can be divided into four types by the level of exertion involved: basic aerobic endurance, tempo endurance, maximal endurance and speed endurance. Endurance can also be divided into either aerobic or anaerobic exercise. In practice, basic aerobic endurance is the basis of all movement. The boundary between basic endurance and tempo endurance is called the aerobic threshold. Similarly, the boundary between tempo endurance and maximal endurance is called the anaerobic threshold. Anaerobic (oxygen-free) energy production increases with the level of physical effort. The aerobic threshold is the level of effort at which anaerobic energy pathways start to be a significant part of energy production (usually under 70 % of the maximal heart rate). The anaerobic threshold is defined as the level of exercise intensity at which lactic acid builds up in the body faster than it can be cleared away by the heart, liver and striated muscles. For this reason, it is also sometimes called the lactate threshold (approximately 85–90 % of the maximal heart rate). Once the threshold has been surpassed, more
lactic acid is produced in the muscles than can be removed, slowly leading to fatigue.90 Both aerobic and anaerobic threshold may be increased by training. For example, runners want to increase their aerobic threshold because this will enable them to run faster for longer. Maximal endurance refers to the level of intensity that ranges from the anaerobic threshold to the maximal aerobic exertion. It is determined by the maximal oxygen uptake (VO2max), the biomechanical power of the activity and the performance of the neuromuscular system.
lactic acid is produced in the muscles than can be removed, slowly leading to fatigue.90 Both aerobic and anaerobic threshold may be increased by training. For example, runners want to increase their aerobic threshold because this will enable them to run faster for longer.
Maximal endurance refers to the level of intensity that ranges from the anaerobic threshold to the maximal aerobic exertion. It is determined by the maximal oxygen uptake (VO2max), the biomechanical power of the activity and the performance of the neuromuscular system. The indicative threshold values can be determined using the Karvonen formula:
THE BASIC PRINCIPLES OF ENDURANCE TRAINING
The main goal of endurance training is to increase the body’s ability to perform prolonged exercises ranging in duration from a few minutes to several hours. Typical sports include walking, running, cycling, cross-country skiing, swimming and hiking. Developing endurance usually requires training at least three times per week, for 30 to 60 minutes at a time. Utilizing heart rate zones and training with a heart rate monitor can be useful. However, this is not strictly necessary – the method helps you recognize various heart rate zones and their physiological impact on endurance training.
Key factors in endurance exercise:
• The majority of endurance training takes place in the basic endurance zone (approx. 70–80 % of the training session). This develops basic endurance in general and cardiac output in particular (see section “Heart – Cardiac output”).
• Focus on technique training
• Training should be progressive in nature and there should be sufficient time reserved for recovery
• High intensity interval training (HIIT) is particularly effective for increasing the number of mitochondria and the maximal oxygen uptake (VO2max)
• Perform various interval exercises in the tempo and maximal endurance zones
Physical strength refers to a person’s ability to generate force, or resistance, that one can apply to a given task. In practice, physical strength is determined by two factors: the cross-sectional area of a muscle as well as muscle fiber volume and their contractile intensity. On the other hand, a person may be strong even if their cross-sectional muscle area is not large106 because force generation hinges on the ability of the nervous system to command, recruit and organize the muscle fibers more effectively. The strength of connective tissues such as tendons and fibrous tissues also affects the ability of the muscles to generate force. A good example of this is the biomechanics of the Achilles tendon. The muscle cell type distribution of an individual significantly affects his or her ability to generate force (see section “Muscle cell types”). The force generation ability is also affected by the individual’s sex, age, hormonal balance, nervous system function, general health, and nutritional status. The strength training of muscles (and the nervous system) means training with the objective of increasing force generation and usually also muscle mass. Muscular strength training is commonly referred to as gym training, weight training or resistance training. The maximal force generation ability is commonly measured in terms of a one- repetition maximum (1RM) (for example a squat).
THE BASIC PRINCIPLES OF STRENGTH TRAINING
To develop muscular strength it is usually necessary to exercise the major muscle groups at least twice per week for at least 20 minutes at a time. Studies have typically included training programs of 5–15 different exercises. There are 1–4 sets per exercise, each set consisting of 8–15 repetitions.
Key factors in strength training:
Regular strength training strengthens bones, increases muscle mass and muscular strength, helps in weight management, improves muscular endurance and reduces the occurrence of musculoskeletal ailments. Regular strength training is also associated with increased life expectancy. Strength training may significantly slow down the age- related loss of muscle mass (sarcopenia). In many illnesses muscle atrophy (cachexia) is a risk factor for premature death. For example, as many as 25 % of cancer patients die of cachexia .
THE POTENTIAL DISADVANTAGES OF STRENGTH TRAINING
There are potential health risks associated with strength training. Training using poor technique and excessive loads may cause repetitive strain injuries. Adverse effects of strength training reported in various studies include strains, muscle cramps, joint pains, and in extreme cases, ruptured muscles or bone fractures. Prolonged strength training performed using poor technique can cause ailments like spondylolysis (stress fracture of the pars interarticularis of the vertebral arch), spinal disc herniation and spondylolisthesis (the displacement of a vertebral bone). Young people and older adults are particularly susceptible to these injuries. On the other hand, strength training performed with care and proper form also prevents many types of injury. Elderly people in particular benefit from strength training as it may prevent injuries related to slipping and falling.
SPECIAL TECHNIQUES IN STRENGTH TRAINING: ISOMETRIC TRAINING
Isometric training means exercising muscles in such a way that the length of the muscle remains constant. In practice, this means performing the exercise in a static position and joint angle. The word “isometric” is derived from the Greek words isos (“equal”) and metron (“measure” or “distance”). Isometric training can be divided into overcoming iso- metrics (maximal exertion against an immovable object) and yielding isometrics (prolonged exertion against the resistance of an additional weight or individual body weight). Isometric exercises may be used to promote recovery from injury, for example, in individuals with painful osteoarthritis in the knee. In 2014, Mayo Clinic published a meta-analysis indicating that isometric training performed at a fairly light intensity is effective in lowering blood pressure – even more so than aerobic exercise or other weight training.
Isometric training has been found to increase strength and muscle mass. However, isometric training only strengthens the muscle at the joint angle used (max. 10–20 degrees to either side). Dynamic muscular training strengthens the muscles throughout the entire range of motion.
BASIC PRINCIPLES OF ISOMETRIC TRAINING:
• Use maximal muscle contractions
• The set length is 1–10 seconds (increases maximal strength)
• The set length is 45–60 seconds (increases muscle mass)
• Use three different joint angles per exercise
• Rest between sets using a ratio of 1:10 (for example, 3 seconds of exercise, 30 seconds of rest)
• Isometric exercises may be performed alongside dynamic exercises (the recommendation is to perform explosive exercises followed by isometric exercises)
• Isometric exercises may be performed at the beginning or end of the training session. This way they activate the neuromuscular system in preparation for strength and speed exercises
Sample exercise – maximal strength:
• Deadlift (+ 125 % 1RM): 6 sets x 6-second maximal lift
• The bar must be heavy enough to not move at all
• Maximal muscle tension throughout the whole body
Sample exercise – muscle mass and strength endurance:
• Superset for biceps (3–4 sets) – Bicep curl with a bar x 8 repetitions (30-second recovery) – Isometric bicep tension at a 125 -degree joint angle x 45 seconds
ECCENTRIC QUASI-ISOMETRIC TRAINING (EQI)
EQI is a special technique that may prevent muscle
injuries (stretching elastic components and strengthening tendons). The EQI technique can also be used to increase force generation at all joint angles. Eccentric refers to the lengthening of muscles as they contract; quasi-isometric means movement that is extremely slow, almost static. A sample exercise for EQI is a static push-up in the lower position with hands on blocks. As the muscles become fatigued, the position gradually becomes lower until the chest touches the floor. This combines the isometric exercise and the eccentric muscle contraction and lengthening.
HIGH INTENSITY INTERVAL TRAINING (HIIT)
High intensity training became popular among body- builders in the 1970s when sports equipment pioneer Arthur Jones (1926–2007) developed a method to counter long, lower intensity exercises. The idea was to complete short sets at maximal intensity with short rest periods. Jones also developed the Nautilus exercise machines and published articles (the Nautilus Bulletin) on strength training and muscle growth. High intensity interval training has become a natural continuation of the interval methods used by endurance athletes. High intensity interval training has been in use for a long time in sports that are interval-like by nature, such as soccer, basketball and American football. HIIT is defined as very high intensity exercises (85–95 % of maximum heart rate) completed in interval form, i.e. alternating action and rest. The intensity of the rest phase is usually 60–70 % of maximum heart rate. The length and number of the intervals vary widely depending on the training method. A typical example includes 30 seconds of action followed by 30 seconds of rest, repeated 8 to 10 times. Many studies involve observing a significantly longer interval cycle (for example, 4 minutes of action, followed by 3 minutes of active rest – repeated 4 times). By varying the length of the action phase (from 10 seconds to several minutes), it is possible to develop the body’s various energy systems (see section “Metabolism”). However, there doesn’t appear to be a link between the length of the rest phase and the biochemical effects of the exercise on muscle cells (lactate, ATP, creatine phosphate and H+). This suggests that the benefits of varying the length of the rest intervals can be explained by other factors (neurological, hormonal and cardiovascular changes). In particular, HIIT develops the cardiovascular and circula- tory system, maximal oxygen uptake, insulin sensitivity and sugar metabolism as well as lactate tolerance.158 HIIT is also an effective form of exercise for weight loss and burning fat. In the comprehensive Harvard Alumni Health study (2000), in comparison to lighter forms of exercise, a link was found between HIIT and a lower risk of mortality. HIIT has been found to increase the size and number of mitochondria in muscle cells. In addition, HIIT significantly increases the volume of oxidative enzymes in the muscles (see section “Metabolism – Citric acid cycle”).
HIIT VS. PROLONGED ENDURANCE TRAINING
According to a meta-analysis published in 2015, HIIT is more effective than conventional lighter-impact training for lowering the risk of cardiovascular diseases and generally improving vascular performance. A meta-analysis published in 2014 found HIIT, when compared to constant prolonged exercise, to be significantly more effective in improving the performance of the cardiovascular and circulatory system, particularly in individuals suffering from metabolic syndrome. Compared to prolonged endurance training, HIIT is also a more effective method for developing maximal oxygen uptake and burning fat. The excess post- exercise oxygen consumption (EPOC) and 24-hour energy expenditure after a HIIT session are significantly higher than that of a constant endurance training session.
THE TABATA METHOD
The Tabata method is based on a 1996 study of Olympic- level speed skaters, published by professor Izumi Tabata. The study compared high intensity interval training to training performed at a constant pace. The HIIT group completed a 10-minute warm-up before the interval training which included eight 20-second sets of extremely high intensity (170 % VO2max / 85 rpm on a stationary bike) alternated with 10-second rest intervals. The actual workout was therefore only 4 minutes in length. There was a short post-workout cool-down phase. The control group exercised for an hour on the stationary bike at a constant pace (70 % VO2max). Both groups trained 5 times per week for 6 weeks. The training intensity was increased in both groups in accordance with improvements in fitness and oxygen uptake.
The Tabata group’s improvements in maximal oxygen uptake (VO2max) were higher than those of the control group (7 ml/min per kg vs. 5 ml/min per kg). The anaerobic capacity of the Tabata group also improved 28 % compared to the baseline, whereas the control group showed no improvements at all. The Tabata group also spent significantly less time training than the control group. Having gained popularity in recent years, Crossfit training applies the Tabata method on bodyweight and strength exercises. However, it is unlikely that Crossfit will produce the same extreme intensity (VO2max 170 %) as the traditional Tabata method, mostly due to the overbearing muscle fatigue. The Tabata method is best combined with simple exercises that effectively increase the heart rate and anaerobic load, such as cycling, running, cross-country skiing and indoor rowing.
THE GIBALA METHOD
The Gibala method is based on a 2010 study conducted on students, published by Martin Gibala, a doctor of physiology. The goal of the study was to determine the effect of high intensity (100 % VO2max) interval training on general performance using a method that is safer and of slightly lower intensity than the Tabata method. The study continued for two weeks during which six stationary bike workouts were completed. Each workout included a 3-minute warm-up phase followed by the interval phase: 60 seconds of action followed by 75 seconds of rest, repeated 8–12 times. There was no control group involved in the study. Gibala found out that this method achieved the same oxygen uptake benefits as 5 hours of constant pace endurance training per week. The method also significantly increased the force generation capability of muscle cells and improved sugar metabolism.
• Warm up for 5–10 minutes (stationary bike, rowing machine, running)
• Complete 8 sets as follows: – 60 seconds of action (between tempo and maximal endurance) – 75 seconds of rest / light action (cycling, walking, light rowing)
• Follow with a short cool-down and recovery phase
• As you improve, you may increase the number of sets to 12
SPRINT INTERVAL TRAINING (SIT)
Many HIIT exercises with typical alternating action and rest cycles are called sprint interval training. This section discusses sprint interval training performed by running and its positive effects on the cardiovascular and metabolic performance. Sprint interval training may significantly increase the levels of myokinase and creatine phosphokinase enzymes in muscle cells as well as boost the activity of glycolytic enzymes. The enzyme activity of the mitochondria in muscle cells is also significantly increased. This means that the training improves the aerobic (oxygen present) and anaerobic (oxygen not present) energy expenditure of muscle cells (see section “Metabolism” for more information).
SIT may also increase the cross-sectional muscle area and is likely to change the muscle cell type distribution to contain more of the fast IIA cells (see section “Muscle cell types” for more information).171 Sprint interval training has also been found to significantly increase the levels of growth hormones and testosterone (anabolic effects, i.e. related to muscle growth and increased strength). A study published in 2011 found that a 6-week period of sprint interval training (4–6 x 30 seconds of running) significantly improved aerobic performance and oxygen uptake (as much as the control group that ran for 30–60 minutes at a constant pace). However, spring interval training did not improve cardiac output.
• The sprint may be completed on a level surface or slightly uphill (easier on the knees)
• Warm up by jogging for 5–10 minutes and performing a few sharp accelerations while running
• Complete 4–6 sets as follows: – Run 200 meters at 85–95 % of maximum exertion – Rest/walk for 3–4 minutes
• Slowly increase the number of sets from four to six
• We recommend completing 1–3 workouts per week depending on the volume and intensity of other training
HIGH INTENSITY INTERVAL RESISTANCE TRAINING (HIRT)
Strength training is also compatible with short recovery periods and high intensity. This is called high intensity interval resistance training (HIRT). Typically, strength training conducted at high intensity involves long recovery periods (3–5 minutes) between sets to maintain the best possible performance in each set. On the other hand, shorter recovery periods (20–60 seconds) are more effective for increasing the levels of growth hormones and improving muscular endurance.
Besides running and wrestling, gymnastics is one of the original forms of exercise. The word is derived from the Greek word gymnos meaning “naked” or “clean.” In Ancient Greece gymnasts naturally exercised in the nude. As a form of exercise, gymnastics was particularly popular in the army as it prepared the bodies of the warriors for battle. These days, gymnastics is a sport that has been divided into various forms such as artistic gymnastics and rhythmic gymnastics. The goal of gymnastics is to improve physical strength, coordination, balance, agility, muscular endurance and flexibility. From the biohacker’s viewpoint, the top priority is to train a well-functioning body using simple gymnastic exercises. Artistic gymnastics is a particularly useful source for exercises performed on rings, parallel bars, a horizontal bar or a pull-up bar. When started from an early age, gymnastics develops motor skills, general fitness and cognitive and social skills. Gymnastics also develops the ability to adopt full body movement sequences, spatial awareness and the ability to adapt to various kinesthetic stimuli.
BASIC PRINCIPLES OF GYMNASTIC TRAINING
One of the main physiological factors in gymnastics is the greatest possible force generation in relation to body weight. Great muscle mass alone will not ensure success in gymnastics. Moving one’s body requires great relative strength. For young and healthy individuals, the correlation between muscle thickness and maximal strength is usually 0.5–0.7 in the lower limbs and just 0.23 in the upper limbs. Even more so than strength, skill training is of utmost importance in gymnastics. Without sufficient skills, it is impossible to perform gymnastic movements. However, they also require sufficient strength. Strength and skill develop hand in hand.
Below we have listed basic gymnastic movements categorized by difficulty level. If you are a beginner at gymnastics, try the easiest movements beginning with the basics. The most efficient method to learn the movements is under the guidance of a coach. There are good instructions and video clips available for each of the movements on the Gymnastics WOD website.
Gymnastics movements – easy:
• Forward/backward roll
• Hollow rock / hollow hold
• Superman / superman rock
• Pull-up (with bar or rings)
• Ring row
• Broad jump
• Box jump
• Hip shoots
• Hanging on a bar (active and passive / different grip variations)
• Push-up (different variations)
Gymnastics movements – medium difficulty:
• Handstand (against a wall or without a wall)
• Handstand walk
• Dip (with parallel bars or rings)
• Rope climb (different variations)
• Toes to bar (T2B)
• Tuck up
Gymnastics movements – difficult:
• Handstand push-up
• Muscle-up (with bar or rings)
• Front lever (different variations)
• Back lever (different variations)
• Iron cross (different variations)
• German hang
• Swings on parallel bars
A kettlebell is an iron or steel ball equipped with a handle. Training involves ballistic exercises that improve strength, speed, balance and endurance. It provides a hard workout for the hamstrings, pelvis, lower back, shoulders, arms and the entire core. It is crucial to follow proper form. The history of kettlebell training goes back to 18th-century Russia where the sport originates. The kettlebell or giryawas popular especially amongst farmers and later used for exercise in the Soviet army. In the 1940s, kettlebell training was refined as a sport called Girevoy Sport. The sport includes lifts similar to weight lifting such as jerking and snatching. Both sports involve lifting as many repetitions as possible within a 10-minute period.
The Russian swing, a simple kettlebell exercise, has been found to develop maximal and explosive strength in the lower body.181 In addition, an interval-type kettlebell swing routine (alternating 30 seconds of action and 30 seconds of rest for 12 minutes) causes a positive hormonal response typical of strength training (increased post-workout levels of testosterone and growth hormone). The swing exercises have also been found to improve endurance and maximal oxygen uptake.
BASIC PRINCIPLES OF KETTLEBELL TRAINING
As with other technique-based athletic sports, you should familiarize yourself with the basics of kettlebell training before attempting the exercises. The basic techniques can be learned quickly. You should progress in the movements according to their difficulty level. The weight of the kettle- bell should be increased incrementally. If you have shoulder or back problems, kettlebell training may not be a good form of exercise for you as it places a lot of strain on these areas.
Kettlebell movements – easy:
• Russian swing
• American swing
• Deadlift using kettlebells
• One-arm kettlebell row
• Goblet squat (holding the kettlebell in front of the chest)
• Shoulder press using a kettlebell
• Abdominal crunch holding a kettlebell with straight arms
• Farmer’s carry using kettlebells
• Slingshot (well suited for warm-ups)
• Halo (well suited for warm-ups)
• Russian twist
• Thruster using kettlebells
• Floor press in bridge position using kettlebells
• Overhead squat using one or two kettlebells
• Sots press using kettlebells
• Pistol squat using kettlebells
Kettlebell movements – medium difficulty:
Kettlebell movements – difficult:
• Turkish get-up
• Front squat with two kettlebells
• Clean using one or two kettlebells
• Jerk using one or two kettlebells
• Snatch using a kettlebell