填空题

Physical fitness is the result of many factors--good medical care,
proper nutrition, adequate rest and relaxation, and sensible personal habit. (1) ______
But these are never enough. An essential factor is regularly physical (2) ______
activity--exercise for a body that needs it to function well.
All of us know that ordinary movements things as running, (3) ______
jumping, and bending--made possible by muscles. Muscles also do (4) ______
many other things. They suck air into your lungs, push food along
your digestive tract, and tighten your blood vessels to raise blood
pressure when you need more pressure for an emergency. Your heart
is a muscular pump.
When your muscles are not used, or are not used enough, they
do not develop and grow proper. They soon become flabby and (5) ______
weak, shrink in size, and lose the ability to do the jobs they were
mean to do. Recent studies showed that the average high school (6) ______
student spends fifteen to thirty hours a week watching television and
only two hours a week in organizing play or exercise. That is one (7) ______
reason why one-third of the 200, 000 pupils tested for the
President’s Council on Physical Fitness failed a simple test of
strength, stamina, and flexible. Some of the boys and girls could not (8) ______
raise themselves to a sitting position without used their hands! (9) ______
Cars and buses, elevators and escalators, TV and push-button
machines all tend reduce strenuous physical activity. But our bodies still need (10)______
exercise. Without it they soon become weak, ineffective, and unattractive.