|
正所谓得暑期者的天下,暑期复习也是强化复习的关键时段,考生一定要认真把握,加强集中复习。对于考研英语阅读来说,大家也要借着暑期这个东风提高阅读能力,下面为大家整理考研英语阅读文章,希望大家能够多读多练多记,提高整体阅读水平。
Cancer and Staying Fit
Four times a week, Anne Rinn, 28, a psychology professor in Bowling Green,
Ky., whose mother died of breast cancer, goes to kickboxing, aerobics or Pilates
classes. Liz Usborne, a 64-year-old breast-cancer survivor, lobs tennis balls
over the net and circuit-trains at a women's gym near her home in Bonita, Cafif.
The thread binding them? Concern about getting-or surviving and thriving
after--breast cancer.
The American Cancer Society estimates that this year, 241,000 women will
learn they have breast cancer and 40,000 women will die of it. Fortunately , a
growing list of effective therapies developed during the past decade has helped
extend lives, one reason that deaths from breast cancer have been dropping
slowly since 1990. Living among us are more than 2 million women who have
undergone breast-cancer treatments.
Modern miracle drugs like Tamoxifen and Raloxifene routinely cut risk for
breast cancer in women whose medical histories or genes make them especially
vulnerable to it. But reams of research also suggest that exercise--an activity
as old as the human race-substantially reduces the odds of ever getting the
disease, lengthens survival and considerably enhances quality of life for women
with breast cancer.
Scientists don't completely understand why exercise is so important, but
they're actively looking for answers. Roughly two thirds of all breast cancers
are considered estrogen-positive; that means that the hormone estrogen fuels
their growth. The rest are estrogen-negative. Many experts believe regular
exercise lowers the amount of estrogen circulating through the body in the
bloodstream. So for certain types of breast cancer, less estrogen equals less
fuel. Exercise also pares off hormonally active fat tissue. Fat manufactures
substance called Aromatase that converts hormones known as androgens to
estrogen. After menopause, when the ovaries stop cranking out high levels of
estrogen, this hormonal cascade becomes the major source of estrogen in a
woman's body
Recently two large, carefully designed studies suggested exercise may work
through more than just hormonal mechanisms linked to estrogen. In a study
published last month in the Archives of Internal Medicine, researchers
speculated that exercise might affect tumor aggressiveness. The researchers
found that long-term moderate or strenuous activity over a lifetime cut risk for
developing estrogen-negative invasive breast cancers (though not
estrogen-positive cancers). Since fewer therapies are effective against
estrogen-negative cancers, that's heartening news. Some earlier research on
exercise suggests it lowers risk for estrogen-positive cancers, too. Scientists
are also looking beyond estrogen at the effects exercise has on insulin, leptin
and certain growth factors.
Regular exercise early in life, particularly around puberty, and exercise
vigorous enough to suppress other reproductive hormones may make a difference,
too. A 2005 multicenter study on lifetime activity matched more than 4,000 white
and black breast-cancer survivors with controls. Researchers found a 20 percent
decrease in breast-cancer risk for the most versus least active women.
After a woman is diagnosed, exercise can dramatically lengthen survival and
lower the odds of another tumor. For up to 14 years, the Nurses' Health Study
tracked nearly 3,000 participants diagnosed with breast cancer. Researchers
found that recurrence rates and deaths from breast cancer (and from all causes)
dipped 26 to 40 percent among those who exercised most, compared with their
sedentary peers. Brisk walking or equivalent energy-burning activity for three
to five hours a week-about 30 minutes a day-netted the biggest benefits. But
even being active for one to three hours a week reduced risk to some degree。
Excess pounds lower the likelihood of survival after breast cancer. But for
many women, maintaining a healthy weight is often a struggle, especially during
treatment. Chemotherapy or radiation can make women feel too tired to exercise.
Steroids given to help ease certain side effects of chemotherapy prompt a
ravenous appetite. Nausea can lead to almost continuous nibbling of comfort
foods to settle queasy stomachs. Some anticancer medications that work by
tampering with hormones may have a hand in weight gain, too. One such hormonal
drug is Tamoxifen, which keeps estrogen from entering breast cells by blocking
receptors atop the cells that allow access. Studies have yet to confirm a
connection, but many women on Tamoxifen complain of watching the scale inch
upward. No matter what the root cause is for weight gain, exercise of all sorts
helps burn calories. And paradoxically, for those who feel too wiped out to fit
exercise in, some evidence shows light to moderate activities may actually
alleviate treatment-induced fatigue。
Doctors once believed upper-body resistance training was apt to trigger the
chronic swelling and discomfort of Lymphedema in women treated for breast
cancer. Lymph is a thin, milky fluid that collects in spaces between cells.
Carrying germ-battling immune cells, it seeps through a lacy network of channels
in the body before draining into the circulatory system. Lymphedema occurs when
lymph backs up, often in an arm or sometimes in the torso, after surgery or
radiation alters lymph channels. Several recent studies suggest that a gradual
approach and proper precautions make resistance training unlikely to raise the
risk of developing Lymphedema or worsening it if it already exists.
That's important news. Resistance training helps reverse the muscle loss
and fat gain called Sarcopenia that often follows chemo-therapy and hormonal
therapy. Itˊs helpful in other ways, too. Osteoporosis, which sets the stage for
life-altering bone fractures, may be hastened by certain anticancer treatments.
Chemo-therapy, for example, sometimes pushes women into early menopause by
pre-maturely shutting down their ovaries. Since estrogen helps protects bones,
losing it speeds bone-thinning, particularly in the spine and hips, which are
especially vulnerable to fractures. Also known to contribute to osteoporosis is
a class of breast-cancer drugs called aromatase inhibitors that cut off the most
plentiful supply of estrogen after menopause by interrupting the process that
converts androgens into estrogen. Resistance training slows bone loss and may
even strengthen bones.
Quality of life counts, too. In clinical trials, moderate to vigorous
exercise programs notched up progressively to 45-minute sessions at least three
times a week eased anxiety and depression, enhanced mood and self-esteem, and
helped counter fatigue.
Thus far, there are few studies of exercise in women with advanced breast
cancer, although early evidence suggests that physical activity offers benefits
here, too, such as less fatigue. More rigorous studies investigating links
between breast cancer and exercise are underway. Don’t settle back to await
developments, though. Rise from your reading and head out for a walk.
|
|