Physiological Adaptations to Exercise and Environmental Stressors

Hypertrophy

An increase in the size of muscle fibers, leading to an increase in cross-sectional area.

Hyperplasia

Hyperplasia is the multiplication of muscle fibers, where cells divide and multiply to replace damaged cells from cell proliferation or splitting. It is not done in humans but is observed in cases where extra weight is added to normal life (e.g., a bird with a weight on its leg, demonstrating isometric strength gain).

Strength and Hypertrophy Differences

Males have more testosterone, which gives them a greater capacity for hypertrophy and strength building than females. Males typically build muscle more obviously.

Mitochondrial Density after Resistance Training

Mitochondrial density increases following resistance training programs because this type of training stimulates hypertrophy (muscle growth) rather than endurance, which focuses on increasing the number of mitochondria.

Body Composition Components

Fat mass and lean/fat-free mass.

Physiological Adaptations of Anaerobic Training

Small increases in glycolytic enzymes, increase in phosphagen system enzymes, increase in phosphagen stores, hypertrophy of fast and slow twitch fibers, increase in aerobic enzymes, increase in VO2 max, cardiac hypertrophy (a non-endurance type, increasing ventricular mass rather than filling, which leads to increased stroke volume and a stronger heart).

Muscle Adaptations of Aerobic Training

Increase in myoglobin content, increase in capacity to oxidize carbohydrates, increase in the number and size of mitochondria, increase in glycogen content, increase in oxidation of fats, increase in triglyceride content, increase in ATP and PC (phosphocreatine) content, adaptation of FTb (fast-twitch b) to FTa (fast-twitch a) fibers, hypertrophy of ST (slow-twitch) fibers.

Cardiorespiratory Adaptations at Rest after Aerobic Training

Cardiac hypertrophy, bradycardia (decreased resting heart rate) due to an increase in stroke volume, increased stroke volume, maintenance of lung volumes, increase in hemoglobin and blood volume, increase in capillary density around muscular beds, lowers blood pressure in hypertensive individuals, increase in hematocrit concentration to carry more oxygen.

Cardiorespiratory Adaptations during Submaximal Exercise

Maintenance of VO2, decrease in glycogen use, increase in fatty acid oxidation (leading to glycogen sparing), decrease in lactate accumulation, increase in the use of lactic acid as a fuel source, increase in the number and size of mitochondria, earlier onset of anaerobic threshold, maintenance of cardiac output, increase in stroke volume, increase in ventricular volume, decrease in heart rate due to increased stroke volume.

Cardiorespiratory Adaptations during Maximal Exercise

Adaptations that occur during maximal exercise following aerobic (or endurance) training.

Cardiorespiratory adaptations during maximal exercise following aerobic training

Decrease in heart rate due to increased stroke volume.

VO2 max

Increase in VO2 max.

Cardiac output

Increase in cardiac output.

Oxygen extraction (a-VO2 diff)

Increase in oxygen extraction (a-VO2 diff).

Stroke volume

Increase in stroke volume.

Heart rate

No change in heart rate.

Cardiac hypertrophy

Cardiac hypertrophy.

Blood volume

Increase in blood volume (with more hematocrit).

Ventilation

Increase in ventilation (including an increase in tidal volume and breathing frequency).

Lactate accumulation

Increase in lactate accumulation, indicating an ability to tolerate higher lactate levels in muscle and blood, reflecting a higher work capacity.

Amine hormones

Amine hormones are derived from amino acids.

Peptide hormones

Peptide hormones are derived from proteins.

Examples of hormones

Examples include Catecholamines, Glucagon, Insulin, ADH, and Growth Hormone.

Steroid hormones

Steroid hormones are lipid-soluble hormones that circulate bound to carrier proteins.

Cortisol function during exercise

Cortisol makes blood vessels more sensitive to hormones that cause vasoconstriction (decreasing blood pressure) and increases lipolysis, gluconeogenesis, and proteolysis to minimize the loss of glucose during exercise.

Growth Hormone (GH) function during exercise

GH increases glycogenolysis, lipolysis, and gluconeogenesis.

Glucagon function during exercise

Glucagon releases glycogen stored in skeletal muscle and the liver to increase blood glucose levels.

Insulin function during exercise

Insulin increases glycogenesis, lipogenesis, and the uptake of amino acids.

Catecholamines

Catecholamines, such as epinephrine and norepinephrine, are released from the adrenal medulla and are fast-acting hormones.

Stimuli for the release of ADH

The release of ADH is stimulated by changes in plasma osmolality (specifically, high osmolality) and low plasma volume resulting from sweating.

Homeothermic body temperature regulation

Homeothermic refers to the body's ability to maintain a consistent internal body temperature. Everyone has a set point, and deviations from this set point cause physiological changes. The body temperature reflects the balance between heat production and heat loss, only deviating from the normal range during extreme conditions like heavy exercise, illness, or extreme temperatures.

Heat transfer methods

Heat can be transferred in four ways: Conduction, Convection, Radiation, and Evaporation.

Conduction

Conduction is the transfer of heat when something is directly touching the skin.

Convection

Convection is the transfer of heat from one place to another via the motion of gas or liquid across a heated surface. As air or water circulates and passes over the skin, it moves air molecules away that have been warmed by contact with the skin. The greater the movement of water and air, the greater the rate of heat removal.

Radiation

Radiation is the transfer of heat given off by infrared rays. The body radiates heat in all directions and receives heat from surrounding objects. If the surrounding objects' temperature is greater than the body's, heat gain will occur.

Evaporation

Evaporation is a means of dissipating heat, particularly through sweating.

Cardiovascular adaptations during exercise in hot environments

Heat loss mechanisms compete with working muscles for blood flow and nutrients, meaning neither receives these necessities adequately. While cardiac output remains constant, stroke volume will decline, causing heart rate to increase. The body may begin to rely on the anaerobic system for energy because oxygen cannot be adequately delivered to the muscles.

Stroke volume decrease in heat

Stroke volume decreases because less blood is returning to the heart, as it is redirected to the skin to manage heat stress.

Hormonal changes during exercise in hot environments

In hot environments, there is increased sympathetic nervous activity, increased heart rate, decreased stroke volume, sometimes increased cardiac output, and increased reliance on carbohydrates (which are depleted much faster). Oxygen uptake increases during constant-rate exercise, and sweating increases.

ADH and aldosterone release during heat stress

To compensate for dehydration and electrolyte loss, the release of ADH (Antidiuretic Hormone) and aldosterone increases, causing sodium and water retention and expanding plasma volume.

Heat exhaustion

Heat exhaustion is the inability of the cardiovascular system to meet the needs of both the muscles and the skin, often caused by a reduction in blood volume due to sweating.

Heat stroke

Heat stroke is a failure of the thermoregulatory mechanism, which can be fatal.

Avoiding heat-related disorders during exercise

Strategies to avoid heat-related disorders while exercising in hot environments.

Heat-related disorders

Can be avoided by not exercising if environmental heat stress is too high, wearing proper clothes, being aware of hyperthermia, ensuring adequate fluid intake (pre-hydrating before exercise), and reducing the intensity or eliminating exercise in extreme heat.

Heat injury symptoms

Include irritability, thirst, nausea or vomiting, dizziness or lightheadedness, heavy sweating, elevated body temperature, or a fast heart rate.

Benefits of heat acclimatization

Repeat exposure to heat stress improves the body's ability to lose excessive heat, increases the rate of sweating in areas most efficient at heat loss, increases stroke volume, improves blood delivery, reduces the rate of muscle glycogen use, and delays the onset of fatigue.

Requirements for heat acclimatization

Requires exercise in a hot environment, not just exposure to heat. The level of acclimatization depends on the specific conditions of exposure, the duration of exposure, and the rate of internal heat production.

Primary means of avoiding excessive cooling

Shivering, nonshivering thermogenesis, and peripheral vasoconstriction.

Health risks of exercising in cold environments

Include increased submaximal VO2, increased reliance on anaerobic metabolism, decrease in exercise capacity, less blood flow to the skin, decrease in lipid mobilization, increase in glycogen use, increase in lactate production, increase in cardiac output, decrease in submaximal heart rate, decrease in muscle strength, decrease in VO2 max, and direct health risks like hypothermia and frostbite.

Behavioral adaptations to avoid cold-related risks

Increasing clothing, increasing heat storage, increasing insulation, and decreasing convection, conduction, and radiation (to reduce heat loss).

Pulmonary ventilation response to higher altitudes

Increases at higher altitudes, both at rest and during work, meaning breathing starts to increase immediately. More air needs to be inspired to supply as much oxygen as normal breathing at sea level because the air is less dense.

Effect of altitude on hemoglobin saturation

Hemoglobin saturation drops at altitude (e.g., from 98% to 92% at an elevation of 8,000 feet) due to a decrease in the partial pressure of oxygen (PO2) within the alveoli and pulmonary capillaries.

Driving force of oxygen from blood to tissues at altitude

Significantly decreases (e.g., 55 mmHg at sea level vs. 20 mmHg at 8,000 feet).

Physiological response to alkalosis at altitude

The kidneys excrete more bicarbonate ions to buffer acids, leaving more acids in the blood to reverse the alkalosis.

Effects of body temperature dropping below 94 degrees

The hypothalamus loses its ability to thermoregulate.

Impact of hypothermia on heart rate

The heart's SA node is affected by hypothermia, causing heart rate to drop and reducing cardiac output.

Consequences of reduced cardiac output due to hypothermia

Leads to less oxygen being pumped and circulated.

Cold-related health risks

Hypothermia and frostbite.

Increased reliance on anaerobic metabolism in cold

Occurs due to physiological responses to exercising in very cold environments.

Decrease in lipid mobilization in cold

A physiological response to exercising in very cold environments.

Decrease in muscle strength in cold

A physiological response to exercising in very cold environments.

Decrease in VO2 max in cold

A physiological response to exercising in very cold environments.

Increase in cardiac output in cold

A physiological response to exercising in very cold environments.

Decrease in submaximal heart rate in cold

A physiological response to exercising in very cold environments.

Increase in lactate production in cold

A physiological response to exercising in very cold environments.

Maximal oxygen uptake (VO2 max)

Maximal oxygen uptake decreases as altitude increases.

Partial pressure of oxygen

There is very little decrease in VO2 max until the partial pressure of oxygen drops below 125 mmHg (around 5,200 feet).

Decrease in VO2 max

Above 5,248 feet, maximal oxygen uptake decreases by 11% for every 3,281 feet of ascent.

Plasma volume changes at altitude

A person's plasma volume progressively decreases at altitude, then plateaus by the end of the first few weeks.

Red blood cell (RBC) production at altitude

In the first few hours at altitude, red blood cell production increases.

Dehydration at altitude

The decrease in plasma volume leads to dehydration, so drinking water is essential to retain plasma.

RBCs per unit of blood

The result of plasma loss is an increase in the number of RBCs per unit of blood, allowing more oxygen to be delivered to muscles.

Restoration of plasma volume

Although diminished, plasma volume is eventually restored with continued exposure to high altitude.

Cardiovascular response at altitude

At submaximal work levels during the first few hours at altitude, heart rate increases, but stroke volume decreases due to reduced plasma volume.

Blood pressure in pulmonary arteries at altitude

Blood pressure in the pulmonary arteries increases during exercise at altitude, potentially involving structural changes.

Metabolic response at altitude

Anaerobic metabolism is expected to increase, and lactic acid production is expected to rise at any given workload.

Lactate accumulation at altitude

At maximal effort, lactate accumulation is lower in muscles and blood because individuals cannot reach the same maximal effort at altitude.

Physiological adaptations in hyperbaric conditions

Water reduces stress on the cardiovascular system, thereby reducing workload.

Pressure application in water immersion

Immersing the body up to the neck applies pressure to the lower body, minimizing blood pooling and assisting blood return to the heart.

Heart rate drop in water immersion

Heart rate drops by 5-10 BPM when immersed in water.

Plasma volume increase in diving

Plasma volume increases during diving, leading to a reduction in hemoglobin hematocrit.

Surface heart rate reduction in diving

Diving can reduce surface heart rate by 50%, leading to bradycardia.

Breath-holding diver's depth limit

A good breath-holding diver's depth limit is determined by the ratio of their total lung volume (TLV) to their residual volume.

Good diver's lung volume ratio

Good divers typically have a 5:1 ratio of total lung volume to residual volume.

Oxygen poisoning

Oxygen poisoning occurs when the partial pressure of oxygen values are above 318 mmHg.

Effect of oxygen poisoning

Oxygen poisoning impairs the binding of CO2 to hemoglobin, leading to less oxygen being removed for tissue use.

Nitrogen narcosis

Nitrogen narcosis results from the narcotic effect of nitrogen when its partial pressure is high.

Symptoms of nitrogen narcosis

Nitrogen narcosis is similar to alcohol intoxication, impairing judgment and compromising the diver.

Decompression sickness (the bends)

Decompression sickness results from ascending too rapidly, causing nitrogen bubbles to form in the body.

Prevention of decompression sickness

To prevent decompression sickness, divers use dive tables that guide safe times and depths.

Treatment of decompression sickness

To treat decompression sickness, individuals may be placed in a hyperbaric chamber to simulate a slow ascent.

Risks associated with changing pressures in diving

Risks include spontaneous pneumothorax and ruptured eardrums.

Primary drive for respiration

The primary drive for respiration is to breathe out or 'blow off' CO2.