运动强度监控

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Monitoring Exerise IntensityHeart rate and exercise intensity. Monitoring the heart rate response to exercise is one method for assessing workout intensity. By using an age-adjusted or known maximal heart rate (MHR), a heart rate exercise benefit range (EBR) can be set within a high and low heart rate in relation to the MHR. When MHR is unknown, the value is commonly estimated by subtracting the age from 220 beats per minute (bpm). Unfortunately, this method for estimating MHR can be problematic since the result can vary for 68 percent of the population within 10-12 bpm above or below the average estimated value. Also, certain medications can invalidate the usefulness of a predicted MHR for setting a heart rate benefit range for aerobic conditoning. Using the MHR obtained at maximal oxygen intake (see aerobic capacity) or from maximal exercise testing is the best method for ssetting the EBR for aerobic conditioning. Only highly trained athletes in sports like bicycling, rowing, running, or swimming should push themselves to the upper limit needed to attain MHR. Most individuals should ask a qualified fitness professional or physician about using an estimated MHR as a reliable indicator for setting an EBR for conditioning.
Pulse counting procedure. Because it is difficult to obtain the heart rate during exercise (unless you have a heart rate monitor), the pulse taken immediately after you stop exercising. Correct procedure depends on beginning the first pulse count within 5 seconds after you stop exercising and completing the count within 15 seconds. The following is a description of the procedure:

Find your pulse immediately after exercise by placing your first two fingers (not your thumb) over the radial artery on the thumb side of the wrist (inside the wrist bone) or lightly on the carotid artery in the groove in the neck on the side of the voice box below the angle of the jaw. Press lightly and do not press on both carotid arteries at the same time. Begin counting and count the number of pulses in a 10-second period. The first pulse that begins the 10-second interval should be "0" and you should continue counting throughout the 10-second period (i.e., 0…1…2…3…4…etc.). Then multiply the 10-second count times 6 to convert the pulse rate to beats per minute.

The benefit range for aerobic conditioning can vary between 55 to 90 percent of MHR, or 40 to 85 percent of aerobic capacity (same as heart rate reserve) (29). For an example of how to use the heart-rate reserve method, see the Karvonen formula below. When using the Karvonen formula to set the EBR, the training heart rate range can be as low as 40 to 49 percent of heart rate reserve for individuals who are unfit.
From the Table below, for a person who is 45 years of age, the EBR can be set between 96 to 157 bpm at 55 to 90 percent of MHR (based on a predicted MHR = 220 bpm minus the age). The table is for illustration purposes and is intended to show the wide exercise benefit ranges for various age groups.

Age in Years 20-30 31-40 41-50 51-60 61+

EBR in bpm 107-175 101-166 96-157 91-148 85-139

MHR in bpm 195 185 175 165 155

If you are unfit and just beginning to exercise, it is a good idea to stay at the low end of your EBR. The progression should be gradual and you should not reach the high end until after 6 months. For those who are highly fit or training for competitive sports, exercise heart rate may be at the high end or even exceed the highest value of the EBR.
Karvonen formula. Another method commonly used for determining an exercise heart rate range for aerobic training is to estimate the heart rate response at a given percent of aerobic capacity by using the Karvonen formula. To use this method, you will need to know your resting and estimated (or known) maximal heart rate in beats per minute. First count the number of pulses for 30 seconds while standing at rest and multiply the value by 2 to obtain the resting heart rate in beats per minute. The calculation is as follows for a 45 year old person exercising at 60 percent of aerobic capacity with a resting heart rate = 75 bpm:

Exercise Heart Rate = resting heart rate + .60 (maximal heart rate - resting heart rate)

where estimated maximal heart rate = 220 - age in years

Exercise Heart Rate = 75 bpm + .60 (220 bpm - 45 years - 75 bpm )

Exercise Heart Rate = 75 bpm + .60 (100 bpm) = 135 bpm

As aerobic fitness improves, your exercise heart rate may be lower for the same workout intensity in METs. The lower heart rate at the same work intensity means that the amount of blood ejected by the heart with each beat (stroke volume) has increased and the cardiac output (heart rate in bpm x stroke volume) can stay at the same level with fewer heart beats. Before increasing exercise intensity, it is a good idea to ask whether the increased effort is necessary for health benefits and general conditioning. Remember to always assess how you feel and reduce effort if you are exercising too hard.
Using the exercise heart rate alone is not a precise method for monitoring training intensity (24). In fact, a number of external factors can cause the heart rate to vary independently of workout intensity (metabolic demand) (27). Some of these factors include time of previous meal, environmental termperature, and airflow/ humidity which can influence heat dissipation. Also the degree of rest, overtraining, illness, and certain cardiovascular medications can often invalidate the use of exercise heart rate as an indicator of metabolic demand. However, an abnormal heart rate response to exercise like rapid and irregular heart beats or a failure of the heart rate to rise with an increase in metabolic demand are important signs that warrant physician attention.
Perceived exertion and intensity. Another method for monitoring physical effort is to assess how you feel using a perceived exertion rating (RPE) scale. The procedure is best used for nonstop activities like walking, jogging, bench stepping, swimming, or cycling. Monitoring exercise effort by using the RPE scale can provide a method for checking your training heart rate range as an indicator of intensity, and can also be used during exercise without stopping to obtain a pulse.
Rating perceived exertion can help you sense effort by listening to your body. The proper rating of perceived effort depends on input from the muscles, joints, breathing rate, and energy demand. By using an RPE scale, you can learn to evaluate your internal comfort zone and sense excessive discomfort. The following is a description of one commonly used procedure (28-30):

Estimate your exertion by using the exercise intensity scale below. The scale begins with 0 (nothing at all) and increases to extremely heavy (maximum). For example, 10 is the exertion you feel when the exhaustion is beyond anything you have ever experienced and the exercise is so difficult that you almost can’t make it. If the exertion is fairly light, you should answer 2 or 3 and so on. Feel free to use any number on the scale that you wish, as well as half values (e.g., 1.5) or decimals (e.g., 0.7, 4.6, etc.). It is important to select a number that best describes how you feel while exercising and not after you stop. Rate yourself as honestly as possible and try not to overestimate or underestimate your numerical value. Do not rate kind of work you are doing like comparing running to cycling or swimming. If you are exercising with another person or in a group do not compare your rating to others who might influence the number.

0	Nothing at all
0.5	Extremely light	Just noticeable
1	Very light	Like slow continuous walking
2	Light	Weak
3	Moderate	Can continue without difficulty
4	Somewhat heavy
5	Heavy (strong)	Can continue without excessive fatigue
6
7	Very Heavy	Very tired and strenuous
8
9
10	Extremely heavy	Maximum

The breathing rate is a good indicator of perceived exertion. Therefore it is a good rule to use a conversation test to rate your effort. You are most likely working too hard if you need to stop and catch your breath. If you can talk and exercise at the same time, you are not working too hard. However, aerobic exercise should leave you at least a little short of breath. With practice, you should be able to use the RPE scale and eventually reduce the number of times needed for pulse counting. The intensity for beginning an aerobic conditioning program should be at the low end of your MET-intensity range and you should gradually increase workout intensity only after assessing both exercise heart rate and RPE. The RPE range for most individuals is between 3 (moderate) and 5 (strong). For those who are unfit, the RPE should remain at 3.
The perception of effort during exercise is related to activity tolerance and can vary considerably throughout the population. Since physical activity intensity is classified for public health considerations in both absolute and relative (i.e., in relation to aerobic capacity) terms, it is often convenient to use brisk walking at 3-4 mph as an example of a moderate-intense activity. This example can be misleading for some individuals with reduced acivity tolerance. For those individuals, walking at 3-4 mph exercise can be vigorous. Yet for others with a high level of exercise capability, walking at 3-4 mph walk may require a relatively low level of effort.
Frequency and Duration
Frequency.The minimum number of workouts for cardiorespiratory conditioning is 3 times weekly with no more than two days between exercise sessions. You should gradually progress to 5 days per week only if your fitness level improves and you can effectively manage the additional load. The benefits of exercising beyond 5 days per week may be outweighed by an increased injury risk. If you should exercise five days per week, it is important to lower exercise intensity. Avoid exercising if you are ill, especially if you have a fever or are recovering from an infection. Plan your workouts to avoid strenuous exercise during hot and/or humid days or immediately after a meal. However, light or moderate activity (like walking) may be beneficial after eating, especially if you are trying to lose weight. Whatever your schedule, plan to exercise at a time that is free from interruptions.
Duration. The length of time for an aerobic workout can vary between 8 to 60 minutes and there is an inverse relationship between duration and workout intensity. You should gradually progress from 10-15 minutes of continuous exercise to 30-60 minutes (longer duration for moderately intense exercise and weight management). Intense conditioning on consecutive days can lead to general fatigue and increase injury risk. Depending on your fitness level, it is a good idea to reduce your average workout duration if intensity and/or frequency are consistently high. You should exercise within the DURATIONrange given in your exercise program guidelines. If you have been physically inactive, select light to moderate-intense aerobic activities within the 3-6 MET range, and/or stay at the low end of your duration range and gradually increase the length of the workouts.
Less-intense activities like walking can be maintained for longer periods since exercise duration depends on activity intensity. You can also improve aerobic fitness by varying your effort during a single workout (e.g., by alternating slow jogging and walking with brief rest pauses). This approach is also useful for extending workout duration and expending extra calories.

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