4 - Aerobic Exercise

What kind of energy is mainly used by the muscles of the body?

ATP (adenosine triphosphate)

ATP-PC

• Occurs in the first 30 seconds of intense ex

• The fuelAn source is phosphocreatine

• No O2 needed

• Used for short bursts of activity

• When muscle is at rest, it is restored

Anaerobic Glycolytic System

• Occurs from 30 - 90 seconds

• The fuel source is glycogen (glucose)

• No O2 is needed

• Short duration for moderate intensity

• Lactic acid is produced (by-product of glycolysis)

Aerobic system

• Occurs after the 2nd minute of exercise

• The fuel source is glycogen, fats, and proteins

• Needs O2

What does the recruitment of motor units depend on?

The rate of work

Slow-twitch fibers

• Type 1

• Slow contractile response, high oxidative capacity an low anaerobic capacity, recruited for endurance

Fast-twitch fibers (Type 2B)

• Fast contractile response, high glycolytic capacity, recruited for power

Fast-twitch fibers (Type 2A)

• Characteristics of both type 1 and type 2B, recruited for both anaerobic and aerobic activities

Sub maximal intensity activities lasting 20-30 min

Will increase endurance

Intense activity lasting 30-120 seconds (and repeated after 4 minutes of rest or mild exercise)

Will enhance power

Bursts of intense activity lasting only seconds

Will develop muscle strength and stronger tendon and ligaments

Activity with large muscles for 3-5 minutes that is repeated after rest

Will develop power and endurance

How is energy expended computed?

• Calculated from the amount of oxygen consumed

• Metabolic Equivalent of Task (MET) = O2 consumed per kg of body weight

• The more effort required, the higher the MET value

Light energy expenditure

• 1.0 - 2.9 MET value

• Ex. sitting, standing, walking less than 2.5 mph

Moderate energy expenditure

• 3.0 - 5.9 MET value

• Rapid walk of 2.5 - 4 mph, walking downstairs

Vigorous energy expenditure

• 6 - 8.8 MET value

• Ex. swimming laps at moderate pace, jogging, shoveling snow

Anaerobic exercise

• Short duration, high-intensity

• Exercises that use fast-twitch muscle fibers

• The body’s need for oxygen exceeds the oxygen supply available

• Relies on energy stored in muscles

• Used in non-endurance sports

• Last from a few seconds to around 2 minutes

Benefits of anaerobic exercise

• Develops stronger muscles

• Improves VO2 max

• Increases capacity to tolerate buildup of waste products

• Improves endurance

• Burns fewer calories than aerobic

• Increased muscle mass helps to stay lean

VO2 max

The highest amount of oxygen consumed during exercise

Rhabdomyolysis

• Breakdown of skeletal muscle fibers, leakage of myoglobin into the bloodstream, and kidneys become unable to filter, can be life-threatening

• Caused by extended muscle compression, crush injury, overexertion

• Symptoms include muscle pain in shoulders, thighs or lower back, brown or red urine

• Complications include high levels of potassium, irregular heart beat, cardiac arrest, kidney damage

• Treatment is IV fluids, management electrolytes,

Aerobic exercise

• AKA cardiac

• Stimulates the heart rate and breathing to increase + sustained exercise over an extended period of time

• Cardiovascular exercises

Benefits of aerobic exercise

• Increased cardiac output

• Increased stroke volume

• Increased mobility

• Increased blood volume and hemoglobin

• Decreased risk of developing a chronic disease, diabetes, heart disease, some cancers

• Dec resting heart rate

• Dec adipose tissue

• Dec weight

What are physiological responses to aerobic exercise?

• Increased HR, increased force of cardiac myofibers

• Peripheral effects: vasoconstriction, increased cardiac output, increase in systolic BP

• Respiratory response: inc gas exchange, inc muscle metabolism

• Responses providing additional oxygen to muscles: inc blood flow, inc oxygen extraction from blood, oxygen consumption depends on vascularity of muscle, fibers # of mitochondria, etc.

Talk test

• If you can talk during exercise = moderate intensity

• If you can’t say more than a few words without needing to catch your breath = vigorous intensity

Target HR

• Max heart rate = 220 - age

• Used when someone is sedentary (not active and healthy)

• Targets HR

  • Lower-end max HR for moderate intensity = max HR x .5

  • Higher-end max HR for moderate intensity = max HR x .7

  • Lower-end max HR for vigorous intensity = max HR x .7

  • Higher-end max HR for vigorous intensity = max HR x 85

• Ex. 220-25 = 195, 195 x . 5 = 97.5, and etc.

Karvonen Method

Similar to the target heart rate method but factor in resting HR

Borg rating of perceived exertion

• Asks a patient what their perceived exertion is while doing exercise

• Ranged form 6-20 points (6 = no exercise, 20 = max exertion)

Examples of fitness testing

• For healthy people

• Ex. run 1.5 miles, 1 mile walk test, etc.

Multistage testing

• Testing is usually done in 4-6 increments on a treadmill

• Progressive increase in speed and grade

What are the purposes of stress testing?

• Helps diagnose heart disease

• Evaluate cardiovascular function, and response to exercise training

• Assists in selecting mode of Rx for heart disease

• Increased patient motivation

When should stress tests be stopped?

• Onset or progressive angina

• Significant or excessive rise of BP

• Lightheadedness, confusion, pallor, cyanosis, nausea, SOB, wheezing, leg cramps

• No inc in HR with inc intensity

• Onset or change of heart rhythm

• Severe fatigue

• Pt wants to stop

Stages aerobic conditioning (for patients with coronary disease)

• Phase 1 - inpatient phase

• Phase 2 - Outpatient phase

• Phase 3 - Outpatient program

General exercise program

• Warm-up period: 5-10 minutes of total body exercise like walking trying to get the HR within 20 bpm of target HR

• Exercise period: continuous, interval, circuit, circuit-interval training

• Cool-down period: 5-10 minute of total body movement and static stretching

Continuous training

• Submax energy required sustained throughout the 20-60 min session

• Progressive inc in work rate

• The most efficient way to improve endurance

• Mainly using slow-twitch fibers

Interval training

• Improves strength and power more than endurance

• Involves brief period (1 to 2 min) of intense exercise with a longer period (3-5 min) of less intense activity or rest

• Uses aerobic and anaerobic exercise

• During rest, ATP and O2 are replenished

• Ex. 20 sec of a specific exercise then 10 sec rest then 20 sec of another ex then 10 sec rest

Circuit training

• Uses a pre-established sequence (circuit) of continuous exercise that is done in a series at individual exercise stations that target a variety of major muscle groups

• Improves strength and endurance

• Uses mechanical resistance

• Usually, reps are higher and resistance is lower

• Progressed by inc sets, reps, resistance, # of exercise stations, etc.

• The order of exercises is important (large muscle groups before small, multi-joint muscles before single-joint muscles)

• Alternate pushing and pulling exercises

• Can be combined with interval training

Progressive resistive exercise (PRE)

• System of dynamic resistance training in which a constant external load is applied to the contracting muscle by some mechanical force and incrementally increased

• Usually done in 2-3 sets of 6-12 reps

Repetition maximum (RM)

• Helps determine the effectiveness of a resistance exercise program and the appropriate exercise load for training

• Used with PRE programs

DeLorme regimen

Progressive loading during each set (each set you do more weight and you start at 50% of a 10 rep max)

Oxford regimen

Modified regressive loading in each set (each set you do less weight and you start at 100% of a 10 rep max)

Daily Adjustable Progressive Resistive Exercise (DAPRE)

• Based on 6 rep max working weight for 3 sets

• Developed to try to figure out a systematic way of how much to increase the resistance in a PRE program to overload the muscle progressively

• Takes into account that patient progress at different rates

• Increase weight by 5-10% if reps and sets are completely without significant disease

Physiological changed that occur during training

• Cardiovascular

  • At rest, dec HR, BP, inc blood volume, and HgB

  • During exercise, inc stroke volume, cardiac output, and extraction of O2 by working muscles

• Respiratory

  • At rest, larger lung volumes and diffusion capacities

  • During ex, inc ventilator efficiency, small amount of air is ventilated at the same O2 consumption rate

• Metabolic

  • At rest, muscle hypertrophy, inc ability to make ATP, inc O2 transport

  • During ex, lower blood lactate levels

• Other: dec body fat, blood cholesterol and triglycerides, inc heat acclamation, inc bone, ligament, and tendon strength

Consideration for exercise program design

• WHO and American Heart Association recommend no less than 150 min of mod intensity ex or 75 min of vigorous intensity training each week

• Frequency: 3-5 times a week

• Duration: usually 20-30 min of aerobic sessio at 70% max HR, if less tan max HR, 45 min of ex

• Mode:

• Intensity: talk test, target HR, Karvonen method, Bord scale

Recommendations aerobic physical activity

• Children: age 6-17 - 60 min of moderate - vigorous aerobic exercise daily

• Adults: age 18-65 - 30 min of moderate intensity of 5 days a week or 20 minutes of vigorous activity 3 days a week

• Older adults: 65 or older - 30 min of moderate intensity exercise 5 days a week or 20 min of vigorous intensity 3 days a week

• Pregnancy or postpartum: can continue to do the same exercise if it was done prior to pregnancy

What is the difference between aerobic and anaerobic exercise?

• Aerobic:

  • O2 needed

  • Lots of energy produced

  • CO2 and H20 = waste product

  • Cardiovascular benefits

  • Helps inc endurance

  • Continuous movement, rhythmical and long duration

  • Low to mod intensity

  • Ex. Walking, running, swimming, cycling

• Anaerobic:

  • No O2

  • Less energy produced

  • Alcohol, CO2, and lactic acid = waste products

  • No cardiovascular benefits

  • Helps inc strength, speed, and power

  • Short burst of high-intensity exercise

  • High intensity

  • Ex. Lifting weight, interval training, sprinting