August 7, 2005
How to Strengthen Your Heart
Fitness refers to your heart muscle. The stronger your
heart, the more fit you are. The only stimulus that makes any
muscle stronger is to exercise that muscle against increasing
resistance. To make your skeletal muscles stronger, you have to
lift heavier weights or press against greater resistance in any
weight-bearing exercise. The only way that you can strengthen
your heart muscle is to exercise against greater resistance also.
When you use your legs, your leg muscles squeeze
blood from the veins near them toward your heart. Then, when
your leg muscles relax, the veins near them fill with blood. This
alternate contraction and relaxation of your leg muscles acts as a
second heart pushing huge amounts of blood towards your heart.
To pump the extra blood from your legs to your heart and then to
your body, your heart muscle has to squeeze harder and faster.
The harder you exercise, the more blood is pumped by your legs
to your heart, and in turn, the harder your heart has to work to
push it out towards your body, so your heart has to beat faster
and with more force to do more work.
Fitness is determined more by how hard you exercise
than by how long you exercise. Exercising at a casual pace does
not do much to strengthen either your heart or your skeletal
muscles. When you work harder, more blood returns to your
heart, and this increased amount of blood fills the inside of your
heart and stretches it, so your heart has to pump against greater
resistance and the heart muscle becomes stronger.
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Several of you have asked for the link to reader Laszlo Pentek’s
comments on high fructose corn syrup and honey. It’s
http://www.drmirkin.com/nutrition/honey.html
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Dear Dr. Mirkin: Does everyone need to drink eight glasses of
water a day?
Drinking lots of water just means you will spend a lot of
time running to the bathroom. All foods contain water, and all
food is converted to energy, carbon dioxide and water. You can
get most of the fluid the body needs from food, and you only
need to drink enough water to prevent constipation.
When you eat, the pyloric valve at the end of your
stomach closes to keep food in the stomach. Then the stomach
takes fluid that you drink and food that you eat and mixes them
into a soup. Then the soup passes to the intestines and remains
a soup until it reaches your colon. Only then is the fluid absorbed
to turn the soup into solid waste in the colon. If you do not have
enough fluid in your body, your body extracts extra fluid from
your stool, which makes it hard and can cause constipation.
A reasonable amount for a healthy human is one cup of
water or any other fluid with each meal. If you have a problem
with constipation you may not be drinking enough water (see my report on
constipation), but if you are not
constipated, you are getting plenty. You'll also want to replace
fluids whenever you sweat a lot, particularly when you exercise
or in hot weather. Drink water whenever you feel thirsty, but
there's no benefit from forcing yourself to drink eight glasses of
water a day.
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Dear Dr. Mirkin: Why are some men so much more aggressive
than others?
A partial answer may come from a study in Biological
Psychology (March 2005), showing that the ratio of a man's
second finger to his fourth finger appears to predict aggression.
The amount of testosterone a baby is exposed to in his mother’s
uterus determines how long his fourth finger grows. So men who
have been exposed to high levels of testosterone in utero have a
larger ratio of the fourth (“ring”) finger to the second (“index”)
finger and therefore are more prone to physical aggression later
in life. The author of this study states: “This study shows that
events in the womb have subtle effects on children's personality."
Previous studies have shown that men with higher ratios of the
fourth to second finger may be better in sports and are usually
more dominant and masculine. On the other hand, these men
are at higher risk for autism and immune deficiency. Men have
larger finger ratios than women. The authors cautioned that
these findings link a larger finger ratio to "a tendency toward
physical aggression". They do not show that all men with larger
ratios are more aggressive.
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Recipe of the Week
Here’s my favorite summer desert:
Fresh Fruit Bowl
Recipe List
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