Basic Concepts of Cardiovascular Exercise
The American College of Sports Medicine (ACSM) and the Centers for Disease Control and Prevention recently formulated new guidelines for the public with respect to exercise. The new recommendations state that “Every adult should accumulate 30 minutes or more of moderate intensity physical activity on most, preferably all, days of the week”.
They defined moderate intensity physical activity as “activity performed at an intensity of 3 to 6 METS, or the equivalent of brisk walking at 3 to 4 mph for most healthy adults”.
Whereas the previous recommendations for populations emphasized the importance of extended periods of strenuous exercise, these new guidelines state that short, intermittent bouts of moderate exercise are important and sufficient for health benefits.
In this module we will discuss:
Basic concepts of cardiorespiratory conditioning.
How to estimate your maximal aerobic capacity.
Types of aerobic activities and basic workouts.
Many of the definitions and terminology associated with cardiorespiratory conditioning have been presented in module 1. However, other terms are used interchangeably to reflect cardiorespiratory conditioning; these include cardiovascular, cardiopulmonary, and aerobic conditioning.
The important point is that this form of conditioning improves health and work capacity by enhancing the circulation and overall functioning of the heart and lungs.
Basics Concepts of Cardiorespiratory Exercise
Cardiorespiratory conditioning consists of both aerobic exercise, which requires oxygen to sustain muscle activity, and anaerobic exercise, which does not use oxygen for the short bursts of highly intense activity.
Most daily work and activities are aerobic in nature, and thus, improving the delivery of oxygen to the working skeletal muscle will improve work performance.
The variety of processes that your ability to utilize oxygen for exercise depends on the factors outlined below:
The functioning of your muscles of respiration or pulmonary ventilation and the ability of oxygen to diffuse across lungs into your blood.
The ability of your heart to increase it’s rate of beating and amount of blood pumped with each beat.
The ability of your blood vessels in and surrounding the skeletal muscle to regulate blood flow within the body.
The ability of the contracting skeletal muscle to extract and use oxygen in blood while exercise is being performed.
Basics Concepts of Cardiorespiratory Exercise (Continued)
All of the previously mentioned factors, the efficiency of the heart, lungs, blood vessels and skeletal muscle, are important in determining your ability to sustain a submaximal workload, and your maximal aerobic capacity.
Two other factors which help determine maximal aerobic capacity are your percentage of specific muscle fiber types and your genetic makeup.
Some persons are endowed with a high aerobic capacity, whereas others are not.
However, everyone can and will improve if a cardiorespiratory conditioning program is followed.
Maximal Oxygen Uptake
Your maximal aerobic capacity or oxygen uptake is the best indicator of how much work you can sustain without fatigue.
The primary measure or predictors of one's capacity to sustain work performance is maximal oxygen uptake (VO2max) or maximal aerobic (cardiorespiratory) capacity.
VO2max is measured in milliliters per minute (ml/min), Liters/min, or after adjusting for body weight in kilograms, as ml/kg/min; a higher value indicates a higher level of
Typical VO2max values range from 30 ml (of oxygen)/kg/min for an unfit person up to 80 ml/kg/min for an exceptionally fit, endurance athlete.
If the unfit and highly fit persons both weighed 70 kg (155 lb) then their respective absolute maximal aerobic capacities would be 2.1 liters (of oxygen)/min and 5.6 liters (of oxygen)/min.
How much strenuous work can you sustain without oxygen? Most people can do very little for more than a couple of minutes. It is very important to realize that most people cannot work for very long at even 90% of their maximal aerobic capacity.
This is because everyone has a threshold at which the balance between aerobic and anaerobic energy systems begins to favor the anaerobic; your muscles cannot extract enough oxygen to produce the required energy. This is called your anaerobic threshold and can be monitored by the accumulation of lactate in your blood.
Of course, your body will know when there is too much lactate, because once lactate goes above a certain value, it starts to accumulate and unless you decrease your work rate, you will become too tired to continue working.
Anaerobic Threshold (Continued)
Interval workouts stress the anaerobic energy systems and will increase your anaerobic threshold and power.
This anaerobic threshold, or “break point” varies among individuals, but ranges between 60% and 100% of your VO2max; all athletes should be able to work at 70% of their VO2max for an extended period, and should have a break point above 70%.
Conditioning programs for athletes should strive to raise the anaerobic threshold or break point to as high as possible, because that means you can work at a higher rate for a longer period of time.
Determination of Work Rate
One common denominator across all types of cardiorespiratory conditioning programs is exercise intensity and work rate. The term exercise intensity typically refers to how hard you are working as a percent of your maximal aerobic capacity.
On average, a maximal capacity of 45 to 55 ml of oxygen/kg/min and a maximal heart rate of 200 beats per min would be typical for a 20 to 29 year old athlete.
Table 1.1 presents the relation between exercise intensity, oxygen uptake, and heart rate for a 20 year old athlete with a maximal heart rate of 200 and a maximal oxygen uptake of 55 ml of oxygen/kg/min.
You must know your maximal capacity or your maximal heart rate to actually quantify your exercise intensity this way.
Table 1.1. Relation Between Exercise Intensity, Oxygen Uptake and Heart Rate
(% of maximal)
100% - Maximal
90% - Strenuous
70% - Moderate
50% - Easy
Factors Affecting the Training Response
The terms duration, frequency and intensity are commonly used when talking about training for fitness or health. All training programs, whether running, biking, swimming, or climbing, strive to vary in duration, frequency, and intensity so as to optimize conditioning and minimize injuries.
Five major factors determine the extent of your maximal aerobic capacity and the magnitude of your response to training. These include:
Initial level of aerobic fitness.
Duration of exercise.
Frequency of exercise.
Intensity of exercise.
Factors Affecting the Training Response (Continued)
General principles apply to all types of physical activities. Take the following general principles and apply them to your individual program:
The degree of aerobic training is closely tied to intensity and total work, not to frequency of training. However, a minimum of 3 days per week is recommended.
A greater training improvement (up to a point) will be noted if you exercise above 85% of VO2max or 90% of your maximal heart rate once a week or every other week: interval training.
Aerobic capacity will improve if exercise increases your heart rate to at least 70% of your maximum heart rate.
A lower exercise intensity can be offset by exercise of longer duration.
Maximal heart rate for swimming and other upper body exercise is lower than maximal heart rate for leg or whole body exercise. Thus, training heart rate (THR) can be 13 to 15 bpm lower for swimming/upper body exercise than when running, biking, or other whole body exercises.
A threshold duration per workout has not been identified to maximize aerobic capacity.
Active recovery involves exercising at 30% to 50% of maximal capacity for 5 to 10 minutes after a strenuous workout.
Throughout this guide, we will continually stress the importance of warming up, cooling down, and stretching. These are integral parts of any workout, regardless of the activity. The cool down, or recovery period, is very important because it will determine how you feel several hours after your workout.
There are two types of recovery: active and passive. Passive recovery, in other words, just resting, was recommended many years ago, and is still recommended when you exercise below 50% of maximal capacity.
Active recovery is preferred for exercise exceeding 60% of maximal capacity to remove lactate.
This helps prevent muscle cramps and stiffness.
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