exercise phys updated

Chapter 2

Exercise Physiology

Fitness• A. Being active improves health: 30 minutes

of accumulated physical activity on most days of the week

• B. Being “fit” goes beyond health and requires a comprehensive exercise program that includes the following components

• 1) Cardiorespiratory endurance• 2) Muscular strength and endurance• 3) Flexibility• 4) Body composition• 5) Balance

Components of Fitness

• 1) Cardiorespiratory endurance– The ability to perform large muscle movements over a

sustained period

• 2a) Muscular strength – The max force that a muscle can produce against a

resistance in a single maximal effort.

• 2b) Endurance– The capacity of a muscle to exert force repeatedly

against a resistance

Components of Fitness

• 3) Flexibility– The range of motion around a joint

• 4) Body composition– The make-up of the body in terms of the relative

percentage of fat free mass and body fat

• 5) Balance– The ability to maintain the body’s position over it’s

base of support.

Involves the heart. Lungs, & blood vessels

Supply the body With O2 and remove wastes

Ratio of lean body mass (muscles, tendons, organs, bone, etc.) to fat mass What is your % body fat

Ability of a muscle or group of muscles to exert maximal force against a resistance 1 rep max (how much weight you can lift on one repetition)

Ability of a muscle, or group of muscles to exert force over a period of time against a resistance that is less than max How many times can you lift 80% of your max

Ability of a joint and surrounding muscles to move freely through its Range of Motion (ROM) How far can your muscle move during stretches

The 5 Fitness Components

Physiology of the Cardiorespiratory System

• For muscles to contract, they need energy in the form of ATP. The cardiorespiratory system is responsible for the three basic processes to produce this energy:– Get oxygen into the blood (oxygen-carrying capacity)– Deliver oxygen to the muscles (oxygen delivery)– Extract the oxygen from the blood to form ATP

(oxygen extraction)• Oxygen-carrying capacity is affected by two primary

functions: (1) the ability to adequately ventilate the alveoli in the lungs and (2) hemoglobin concentration in the blood.

Basic Processes Blood Delivery and Nutrient Exchange

• 1) Pulmonary Ventilation– The total volume of gas inspired and expired per

minute

• 2) Cardiac Output– The amount of blood pumped by the heart per

minute– HR x SV

• 3) Oxygen Extraction– The amount of O2 taken from the HB Molecule and

used in the exercising muscle.

Oxygen Delivery• Oxygen delivery is a function of cardiac output (the

quantity of blood pumped per minute). – Cardiac output (Q) = Stroke volume (SV) x Heart rate

(HR) (in beats per min)• Stroke volume is the amount of blood pumped

during each heartbeat.– Cardiac output increases due to increases in both SV

and HR. • HR typically increases in a linear fashion up to

maximal levels.• SV increases to about 40–50% of maximal

capacity, and then plateaus.

Oxygen Extraction• Oxygen extraction from the blood at the cellular level

depends on muscle fiber type and the availability of specialized oxidative enzymes. – Slow-twitch muscle fibers are specifically adapted for

oxygen extraction and utilization.– Aerobic production of ATP occurs in the mitochondria

of the cells. – The circulatory system increases blood flow to the

active muscles and decreases blood flow to non-active areas such as the viscera, allowing a higher concentration of O2 to be extracted.

Oxygen Consumption• The more oxygen a person can take in, deliver, and

utilize, the more work he or she can perform.

• VO2max refers to one’s maximal oxygen consumption.

– It is expressed in either “relative” terms (mL/kg/min) or “absolute” terms (L/min).

– Relative VO2max allows comparisons between individuals. Absolute VO2max is used to determine caloric expenditure during specific activities.

• Approximately 5 kcal of energy are burned for every liter of oxygen consumed.

Energy production • 1) Adenosine triphosphate (ATP)

• a.Manufactured by the mitochondria in the muscle cell

• b. ATP is the energy source used to drive muscle contraction

• c. Fatty acids and glucose are used to produce ATP

• d. Amino acids are not a preferred energy source, but are used in an undernourished individual

Energy production

Energy System Substrate Limitation to Produce ATP

Primary Use

ANAEROBIC

Phosphogen Creatine phosphate (CP) Stored ATP

Muscle stores very little CP and ATP

High-intensity, short-duration activities; less than 10 seconds to fatigue

Anaerobic glycolysis

Glucose and glycogen

Lactic acid build-up causes rapid fatigue

High-intensity, short-duration activities; from 1–3 minutes to fatigue

AEROBIC

Fatty acids, glucose, and glycogen

Depletion of muscle glycogen; insufficient O2 delivery

Long-duration, sub-anaerobic threshold activities; longer than 3 minutes to fatigue

Anaerobic Threshold • The anaerobic threshold (AT) is reached when exercise

intensity increases above steady-state aerobic metabolism and anaerobic production of ATP occurs.

• When the AT is crossed, exercise can only be sustained for a few minutes before hyperventilation begins to occur.– Lactate accumulates progressively in the blood and the

oxygen deficit and corresponding EPOC are extremely high.

– At this point, the body attempts to rid excess CO2 (a by-product of acid metabolites). The increase in respiration is called the second ventilatory threshold (VT2).

– VT2 is an indirect indicator of AT.

Ventilatory Threshold • There are two distinct changes in breathing patterns during incremental exercise: the

first ventilatory threshold (VT1) and the second ventilatory threshold (VT2).• VT1 occurs as soon as blood lactate begins to accumulate and the body needs to rid

itself of excess CO2 through increased respiration.

– Can be identified using the “talk test.” It is the first point at which it becomes noticeably more difficult to speak.

• VT2 occurs as blood lactate rapidly increases with intensity, and represents increased hyperventilation past the need to rid the body of excess CO2.

– Also known as lactate threshold (LT) and respiratory compensation threshold (RCT)

– Speaking is definitely not comfortable at this intensity.

Fuel Use During Exercise: Carbohydrates• Carbohydrates are the major food macronutrient for the metabolic

production of adenosine triphosphate (ATP) and the only one whose stored energy can produce ATP anaerobically.

– Stored as glycogen in the muscle and liver• Glycogenolysis (breakdown of liver glycogen to glucose) is the primary regulator of

blood glucose.

– Carbohydrates used during exercise come from both glycogen stores in muscle tissue and blood glucose.

• The relative contribution of muscle glycogen and blood glucose used during exercise is determined by intensity and duration.

• After the first hour of submaximal exercise, carbohydrate metabolism shifts from muscle glycogen to glycogenolysis in the liver.

Fuel Use During Exercise: Fats

• Fats are mainly stored as triglycerides in adipocytes, which must be broken down into FFAs and glycerol.– During low-intensity exercise, circulating FFAs

from adipocytes are the primary energy source from fat, but during higher intensities, muscle triglyceride metabolism increases.

– As duration increases, the role of plasma FFAs as a fuel source increases.

Fuel Use During Exercise: Protein

• Protein plays a small role in the fueling of exercise. It must be broken down into amino acids, which can be supplied to the muscle tissue from the blood and from the muscle fiber itself.– Skeletal muscle can directly metabolize certain amino acids to produce

ATP.

– During exercise, glucose stored in a non-exercising muscle can be delivered indirectly to the exercising muscle via the glucose-alanine pathway.

Cardiorespiratory adaptations to acute aerobic exercise

• 1) Increased heart rate (HR)• 2) Increased stroke volume (SV)• a.The amount of blood pumped from each

ventricle each time the heart beats• b.Measured in mL per beat

• Cardiac output = HR x SV


• 3) Increased cardiac output• a. Cardiac output = HR x SV

• b. A typical cardiac output at rest:• 60 bpm x 70 mL/beat = 4200 mL/min• (approximately 1 gallon of blood per min)

• 4) Increased breathing rate


• 5) Increased systolic blood pressure• a. Due to the cardiovascular system attempting to

increase O2 delivery to the muscles

• b. However, blood pressure greater than250/115 mmHg is an indication to

terminate exercise (hypertensive response)


• 6) No change (or a slight decrease) in diastolic blood pressure

• a. Due to the dilation of vessels in the muscles and the skin

• b. This decreases peripheral resistance (which is an important benefit for individuals suffering from heart disease, hypertension, diabetes, and

peripheral vascular disease)

Blood Pressure During Exercise • Systolic blood pressure has a much higher increase during exercise than diastolic

blood pressure due to:– Increased contractility of the heart

– Increased stroke volume

– The muscular need for greater force and pressure to deliver blood to the exercising muscles

– Vasodilation within the exercising muscle, which results in more blood draining from the arteries, through the arterioles, and into muscle capillaries, minimizing the change in diastolic pressure


• 7) Blood is shunted from the viscera to the working muscles

• a. Dilation of vessels that supply blood to the exercising muscles

• b. Constriction of vessels that supply blood to the abdominal area


• 8) Increased extraction of oxygen from the blood into the working tissues

• a. A normal, healthy person is able to load the blood with more O2 in the lungs than he or she is able to use at the cellular level

• b. Therefore, the more efficiently an individual can extract O2 from the hemoglobin in the capillaries,

the more fit he or she becomes

Chronic Training Adaptations to Exercise

SAID principle (specific adaptation to imposed demands) Examples include:– Improved cardiac output efficiency (increased SV and lower HR)

(aerobic training)– Increase in respiratory capacity (aerobic training)– Increase in maximal oxygen consumption (aerobic training)– Increase in bone density (weightbearing exercise)– Improved control of blood glucose and lipids (physical activity)– Maintained or improved lean body mass (weightbearing activity)– Decreased depression and anxiety (physical activity)– Higher quality of life (physical activity)

Cardiorespiratory adaptations due to regular aerobic exercise

• 1) Decreased RHR• a. With consistent exercise (as few as three

months of regular aerobic training), the interior dimensions of the ventricles increase,

allowing them to hold more blood• b. The same cardiac output can be maintained at

a lower HR due to the greater SV


• 2) Decreased relative working heart rate• a. Since a given intensity requires a given amount

of O2, HR at any given intensity will be lower due to increased SV

• b. A trained individual will have to work at higher intensities to achieve the same HR he or she achieved prior to being fit


• 3) Increased VO2max as SV increases

• a. VO2max is the total capacity to consume oxygen at the cellular level

• b. VO2max depends on two factors

• 1. The delivery of O2 to the working muscle by the blood (cardiac output)

• 2. The ability to extract the O2 at the capillaries and use it in the mitochondria


• 4) Increased O2 extraction

• a. Improved ability to remain “aerobic” at higher intensities

• b. Increased capillary density• c. Increased mitochondrial density• d. Increased ability to create ATP


• 5) Increased fatty acid oxidation at any submaximal intensity

• 6) More glycogen is stored in trained muscles and less lactic acid is produced

• 7) Increased tolerance to lactic acid produced during exercise

Exercising in the Heat • In addition to exercising in a hot, humid environment, other factors

can cause heat overload.– Poor hydration prior to exercise

– Overdressing

– Overweight and obesity

• During exercise, the internal heat load is brought to the skin’s surface to be cooled via the secretion of water by the sweat glands (evaporation). – The goal (given favorable environmental conditions) is to prevent body

temperature from rising more than 2 to 3°F.

– When the ability to dissipate heat is compromised, injuries occur.

Physiological Responses to Exercising in the Heat

• Dissipating internal body heat is more difficult in the heat, resulting in a higher heart rate than normal at any level of exercise to maintain cardiac output.

• A hot humid environment is the most stressful environment for exercising and poses the risk of heat exhaustion and heat stroke.

Safety in the Heat• The heat index, as presented on the next slide, provides guidelines

on when exercise is safe and when it should be avoided.• Tips to consider before exercising in the heat:

– Begin gradually

– Always wear lightweight, well-ventilated clothing

– Avoid impermeable or non-breathable garments

– Replace body fluids as they are lost

– Record daily body weight

– Air movement is critical for adequate cooling

Heat Index

Exercising in the Cold • The excessive loss of body heat can lead to a generalized vasoconstriction

and conditions such as hypothermia, frostbite, and increased blood pressure.

• Strong wind can accelerate heat loss.– The windchill index, which is presented on the following next, provides guidelines

for determining if exercise is safe.

• Tips to consider before exercising in the cold:– Wear several layers so that garments can be removed or replaced as needed– Allow for adequate ventilation of sweat– Wear garments made of materials that allow the body to give off body heat

during exercise and retain body heat during inactivity– Replace body fluids in the cold, just as in the heat– Monitor body weight over several days

Windchill Factor Chart

Altitude

• 1) Since there is less partial pressure of O2 at higher altitudes, HR and respiratory rate increase

• 2) During exercise HR may increase up to 50% higher than normal

• 3) Decrease exercise pace so the client can complete the session without becoming exhausted

• 4) It can take up to 2–5 weeks to acclimate to a new altitude

Exercising at Higher Altitudes

• At moderate-to-high altitudes, the partial pressure of oxygen in the air is reduced.

• Acclimatization (physiological adaptation to an unfamiliar or unaccustomed environment) begins in a couple weeks, but it may take several months to fully acclimatize.– Gradually increase exercise intensity over several

days– Increase warm-up and cool-down periods – Take frequent exercise breaks at a lower intensity

Altitude Sickness

• The higher the altitude, the greater the risk.• Altitude sickness can be avoided by proper

acclimatization.• Signs and symptoms of altitude sickness include:

– Shortness of breath– Headache– Lightheadedness– Nausea

Exercising in Air Pollution

• Inhaled air pollutants (i.e., smog) negatively affect the body and performance.

• The overall physiological effects depend on the amount of pollutant in the air, the length of exposure, and the amount of air breathed.

• Exercising early in the morning and avoiding high-traffic areas can help minimize exposure.

Age• Generally, exercise performance improves from puberty

until young adulthood, followed by a slow decline.– If a person maintains activity levels, performance can

be preserved into the early 30s, but inevitably declines beyond age 60.

– Individuals who are sedentary and over the age of 45 (for males) and 55 (for females) should avoid high-intensity activity the first several weeks to decrease the risk of triggering a heart attack.

Gender• The relative amounts of testosterone (in males)

and estrogen (in females) account for specific variances in males and females and their physiological response to exercise.

• Outside of the hormone-attributed differences, men and women have very similar responses to exercise.

Pregnancy• Outside of weight gain, change in body shape, and the

diversion of part of the cardiac output to the developing baby, pregnancy has minimal effect on exercise performance.– Exercise performance will decrease as the pregnancy

progresses. However, exercise intensity and duration should be reduced to maintenance levels during pregnancy, as guided by comfort.

• Current research does not support the traditional concerns about hyperthermia and circulatory diversion.

• It is not recommended to engage in intense training or competitions or to reduce body fat during pregnancy.

General Adaptation Syndrome• General adaptation syndrome refers to the body’s predictable

response to stressful events (including heavy exercise). • Three stages

– Shock or alarm phase (usually lasts 2 to 3 weeks)• The individual initially exhibits signs of fatigue, weakness, and soreness.• He or she soon experiences remarkable gains (attributed to neuromuscular

adaptations).

– Adaptation or resistance phase (begins around weeks 4 to 6)• Major muscular adaptations (biochemical, mechanical, and structural)• Progressive increases in muscle size and strength

– Exhaustion phase (may occur at any time)• Symptoms similar to the first phase, but inadequate repair or recovery time

lead to burnout, overtraining, reduction or elimination of overload, injury, illness, or lack of adherence

Overtraining• Overtraining often occurs during periods of intense overload in which signs

and symptoms are individualized and include a combination of both physiological and emotional factors.

• Some signs and symptoms include:– A decline in physical performance with continued training– Elevated heart rate and blood lactate levels at a fixed submaximal work rate– Weight loss– Sleep disturbance– Multiple colds or sore throats– Irritability, restlessness, excitability, and/or

anxiousness– Loss of motivation and vigor– Lack of mental concentration and focus– Lack of appreciation for things that are normally enjoyable

• The best way to prevent overtraining is periodization.

Delayed Onset Muscle Soreness (DOMS)

• Research suggests DOMS is caused by tissue injury from excessive mechanical force, particularly eccentric force, exerted on muscle and connective tissue.

– Generally appears 24–48 hours after strenuous exercise– Is thought to result from a series of events activated by strenuous exercise:

• First, structural damage occurs as a result of strenuous eccentric muscle actions.

• As a result, calcium is leaked out of the sarcoplasmic reticulum and collects in the mitochondria, halting ATP production.

• The build-up of calcium activates enzymes that break down proteins.• The breakdown of proteins causes an inflammatory process.• Lastly, the accumulation of histamines, potassium, prostaglandins and

edema stimulates pain receptors, leading to the sensation of DOMS.– Attempt to reduce DOMS by starting at a low intensity and progressing slowly

through the first few weeks while minimizing eccentric actions.

General Training Principles • Principle of specificity

– The exercise response to any training program is specific to the mode and intensity of training.

• Principles of overload and progression– Overload involves increasing the load on the tissue or system above

and beyond the normal load.

– Progression is the systematic process of applying overload.

General Training Principles (cont.)

• Principle of diminishing returns– The rate of fitness improvement

diminishes over time as an individual’s fitness approaches its ultimate genetic potential.

• Principle of reversibility– When training ceases, all gains will

return to pre-training levels and may possibly decrease to the point where they are only supporting the demands of daily use.

exercise phys updated

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atp oxygen extraction

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body fat ability