If you have a heart disease or condition， high-intensity exercise for longstretches could

actually increase your chance of a massive heart attack or stroke，recent studies found.

In the first of two studies（1）in Heart， German researchers spent a decadestudying the（2）and intensity of weekly exercise in 1，000 people in their 60swith coronary artery heart disease （冠心病）， almost half of whom were（3）2-4times a week. Predictably， participants who（4）less than 2 times a week weredetermined to be at greater risk for a heart attack. However， counter-intuitively （直觉地 ） ， participants who exercised more than the average were also twice aslikely to have a heart attack or stroke than the average.

A different study found that young men who engage in endurance exercisemore than five hours a week may（5）their risk of developing an irregular heartrhythm later in life.

Swedish researchers surveyed 44，000 men， ages 45-79， about theirexercise（6）at ages of 15，30，50 and over in 2013. Those who exercised（7）formore than five hours a week were 19% more likely to have developed an irregularheartbeat， which is a（8）factor in stroke risk.

Despite their findings， researchers（9）sounding the alarm full-force onintense exercise， citing the "benefits of exercise" while clarifying that "thestudies reviewed here， and future studies， will serve to maximize benefits obtainedby（10）exercise while preventing undesirable effects of intense exercise."

A．active

B．avoided

C．behavior.

D．consequently

E．Density

F．Energetic

G．Engagement

H．Exercised

I．Frequency

J．Increase

K．Intensely

L．Key

M．Largely

N．Published

O．regular

第（1）题__________

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