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Amy Schnitzler was tired.

Surgery and chemotherapy treatments for her breast cancer had knocked the energy right out of her and all she wanted to do was snuggle under the bedcovers all day.

But she got up, anyway.

“Even on my worst days, in terms of fatigue, if I just got up and did a little something, whether it be some light stretching, gentle yoga, just some yoga, that definitely made me feel better and it definitely made me able to greet the day,’ said Schnitzler, who is studying opera.

“It was just a matter of, ‘OK, I know you feel really tired right now, Amy. But if you just get up and do a little something, you’re going to feel better after’. And that has definitely been the case for me.”

Now research bears out what Schnitzler found by instinct. Exercise helps people battling the fatigue caused by cancer and by its treatment — and usually does it better than drugs do.

Related: Exercise Lowers the Risk for These 13 Cancer Types

Karen Mustian of the University of Rochester Medical Center and colleagues looked through all the studies they could find on the various ways to help cancer patients get their energy back. Exercise was the clear winner, they reported in the Journal of the American Medical Association’s JAMA Oncology.

“Even on my worst days, in terms of fatigue, if I just got up and did a little something, whether it be some light stretching, gentle yoga, just some yoga, that definitely made me feel better."

“If a cancer patient is having trouble with fatigue, rather than looking for extra cups of coffee, a nap, or a pharmaceutical solution, consider a 15-minute walk,” Mustian said.

Counseling can help, too, but drugs should be the last option, her team’s review showed. They looked at studies that covered 11,000 cancer survivors, including men and women of all ages. About half involved women with breast cancer.

Amy Schnitzler of Rochester, NY, an aspiring opera singer, exercises to battle the fatigue caused by breast cancer treatment. Kristen Koppers Photography

They compared exercise, counseling and drugs that can be offered to patients such as the amphetamine Ritalin or other stimulants.

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“The literature bears out that these drugs don’t work very well although they are continually prescribed,” Mustian said in a statement. “Cancer patients already take a lot of medications and they all come with risks and side effects. So any time you can subtract a pharmaceutical from the picture it usually benefits patients.”

Schnitzler certainly found it to be true.

“I was diagnosed at age 26, which is kind of crazy,” Schnitzler, who lives in Rochester, told NBC News.

Now 27, Schnitzler has put her career as an opera singer on hold while she recovers from surgery and finishes chemotherapy for tumors that have spread to her lungs.

Related: Exercise Keeps Breast Cancer Survivors Alive Longer

Part of her recovery includes regular exercise.

“Prior to chemotherapy I was a five-mile-a-day runner,” she said. “Chemo has definitely taken a toll for sure. But I am doing an hour of exercise at least five days a week.”

She can manage about two miles a day now but is confident she’ll get the pace back up.

Dorothy O'Shea of Marlborough, Massachusetts, came back as strong as ever, if not stronger.

Dorothy O'Shea of Marlborough, Massachusetts finds exercise helps her battle the fatigue caused by cancer and its treatment. Dorothy O'Shea

“Saturday in the strength class, we were doing this thing where we were like in a plank and you have got a weight in each hand and you do a row with one arm, put that down, do a row with the other arm,” said O’Shea, a 51-year-old colon cancer survivor.

“I was so psyched. I had never done that before. I’d never been able to do that.”

O’Shea had also been a runner before her diagnosis last year but found that continuing exercise helped her not only battle fatigue, but cope with the psychological effects of a cancer diagnosis.

Related: Bad Diet in Teen Years Raises Breast Cancer Risk

“When I was first diagnosed with cancer I admit I did have a little bit of a pity party,” said O’Shea.

“You know, what the heck? I eat well. I exercise. I’m not fat. Why did I end up with cancer?” she added. “But then I was like, ‘I eat well. I exercise. I’m not fat. And I’m recovering from this a lot quicker than a lot of people would have.’”

Both O’Shea and Schnitzler were exercisers before, and both had been following very healthy diets before, also. But Mustian’s review showed exercise appeared to benefit most people, regardless of age, cancer diagnosis or other habits.

"I eat well. I exercise. I’m not fat. And I’m recovering from this a lot quicker than a lot of people would have."

Cancer-related fatigue is different from any other type of exhaustion. Sleep doesn’t help and patients often feel that even raising a hand to sip some tea or coffee is almost more than they can manage. Conversation, even watching television, can be just too much to manage.

Still, exercise helps.

Amy Schnitzler of Rochester, NY, an aspiring opera singer, exercises to battle the fatigue caused by breast cancer treatment. Jenny Berliner Photography

“Exercise and psychological interventions are effective for reducing cancer related fatigue during and after cancer treatment, and they are significantly better than the available pharmaceutical options,” Mustian’s team wrote.

“Clinicians should prescribe exercise or psychological interventions as first-line treatments for cancer related fatigue.”

O’Shea has had to make concessions.

“I will admit I slacked a bit last week, but I just picked up on my strength training last December,” she said.