The hours we need to exercise for is one and half hour a week except gym class.
And it is said that you had better do half an hour exercise three times a week, not do 1 and half hour exercise once a week.
Then what kind of exercise do we need to do?
In junior high-school and high-school days the cardiopulmonary function becomes full and the capacity for muscle endurance is built up. So you need to do exercise for gaining strength.
There are three big principles for our exercise.
Even though it is safe, if it is not so effective, it will be unsuitable for our exercise. Or even though it is effective, if it has the risk to be injured, it won't be suitable for us.
We have to find out the exercise which gives us good health and the exercise we can keep doing with enjoying.
How much should we do exercise?
Basically effective exercise makes you feel a littele bit hard.
You have to know exactly how much exercise makes you feel a littele bit hard.
You can know it from your maximal heart rate.
The maximal heart rate is the maximum pulse rate in one minute.
Generally it is close to the number which subtracts your age from 220.
You must feel the exercise a little bit hard when the heart rate just after exercising or during exercising should be 60-90% of that number.
For example, we are 16 years old. So our maximal heart rate is
So when the maximum pulse rate is 122-183, we should feel the exercise a little bit hard.
Please check this just after exercising, and get to know how much exercise you should do.
Look at this picture. You can know your maximum pulse rate doing like this for a minute.
During exercise, you need to take a rest.
Too much exercise has harmful effects especially on heart and joints.
If you feel the exercise too hard, you should take a rest right away.
And you should take a bath a few hours later after exercising. After exercise, you should take a rest first and take a bath. After taking a bath, do some stretches to relax your body.
During exercise, you often need to drink some water.
60% of a whole human body is made up by water. And this water is 0.9% salty water.
To maintain a human body both conditions have to live up to certain standards.
If a human body cannot keep those conditions, the 60 trillion cells which build up our body cannot live.
When the activities of cells die down, every organ doesn't work well and the human body cannot maintain the life.
And if you sweat a lot during exercise, and water in your blood decreases, your blood becomes icky and results in poor circulation.
Then your blood cannot convey oxygen and sustenance throughout your body. Then you cannot do exercise well, and that causes the injury.
If you drink water, it is absorbed into your whole body and makes blood.
Water cannot stay in your body for a long time. It goes out as urine, sweat, exhaled breath and feces.So we always have to get water.
In other words, to get appropriate water is the key to keep your health in a good condition.
But if you drink too much water during exercise, you may have stomachache or feel tired.
Then how often and how much should we drink water?
Look at the chart below. Basically you need to drink some appropriate amount of water before, during and after exercise.
You should drink water before you feel thirsty.
When you feel thirsty, your body is already lack of water.
So before exercise, you should drink some water.
By the way, what kind of drink should we take?
After one hour exercise, if it is not too hard, water is the best to take.
Because 99% of sweat is water. So to make up water you lost, just take some water.
After more than 2 hours exercise, or if you exercise really hard, you need to take salty water.
Because when you sweat a lot, your body loses not only water but also salt.
When you lose salt-natrium- in your body, it leads you to deconditioning as detailed below.
So when you do the hard exercise, you should take water and salt together.
Speciffically, mineral water or sports-drink which include 0.1-0.2% salt would be better.
Or to get some calories, if it includes 2 or 3% sugar, it is better in addition.（★Only when you do the hard exercise more then 2 hours. If you take sports-drink when you do one hour exercise, it may give you too much salt and sugar.）
From the result of a questionnaire in our school, we could know that 70% of students take some water after exercise.
From the result of a questionnaire about what to drink in our school, we could know that 26% of them drink water, 46% drink sports-drink, 14% drink soft drink and other 14% drink other beverage.
In the answers of other beverage, most of them are cold Japanese tea.
Soft drink includes a lot of sugar.
We explained that you needed 2 or 3% sugar in your drink after hard exercise. But if you get more than 5% sugar after exercise, it might disturb fluid absorption.
So you shouldn't take soft drink.
And barley tea is good to drink. But green tea has so much caffeine which acts as a diuretic. Drinking green tea foments the lack of water.
So you shouldn't drink green tea as a drink after exercise.
Select the drink whick is appropriate for your exercise and is healthy.
And the temperature of the drink is also important.
During exercise, you want to drink cold drinks. But to drink too cold beverage places strain on entrails.
You should drin the beverage at 11-15C or at normal temperature.
To drink water is really important when you exercise.
When you lose 3% water of your weight, you may develop dehydration. If you don't take water, you get dizzy, sick and spastic and might die from dehydration.
If you think your friend may develop dehydration, tell your teacher and ask him or her emergency measure.
If you think you might develop dehydration, call your teacher and take a rest under the shadow with drinking beverage.
Indicator of dehydration
Especially in summer, you also have to be careful for heat disorder and calenture.
Don't forget to take some water always and enjoy exercise!