Exercise is now recommended as part of the treatment for cancer by the American College of Sports Medicine, the American Society of Clinical Oncology, the National Comprehensive Cancer Network, the American Cancer Society, the Oncology Nursing Society, the Commission on Cancer and the Cancer Foundation for Life.

Extensive research shows that exercise also helps to prevent cancers. A review of 12 prospective U.S. and European studies on risk for 26 types of cancer in 1.44 million adults followed for 11 years shows that exercise is associated with reduced risks for cancer, regardless of body size or smoking history (JAMA Intern Med, published online May 16, 2016). So far, physical activity has been associated with a lower risk for cancers of the colon, breast, endometrium, esophagus, liver, stomach, kidney, head, neck, rectum, bladder and lung as well as adenocarcinoma, myeloid leukemia and myeloma.

Evidence that Exercise Helps to Treat Cancers
An extensive review of research (Translational Journal of the American College of Sports Medicine, December 1, 2016;1(17):152–158) shows that exercise:
• reduces the side effects of chemotherapy treatments including nausea, fatigue, anxiety and depression, and increases bone strength and muscle mass (Curr Treat Options Oncol, 2008;9:135–46)
• increases the percentage of people who are able to complete full-dose chemotherapy regimens (J Clin Oncol, 2007;25:4396–404)
• can increase tumor sensitivity to chemotherapy (Cancer Prev Res (Phila), 2013;6:925–37)
• reduces heart damage from chemotherapy (Circulation, 2011;124:642–50)
• markedly reduces arm swelling from extensive breast cancer surgery (N Engl J Med, 2009;361:664–73)
• is associated with a 50 percent increased survival rate in patients treated for breast cancer (JAMA, 2005;393:2479–86) and colon cancer (J Clin Oncol, 2006;24:3535–41)
• is associated with a 70 percent risk reduction of high-grade, advanced or fatal prostate cancers (Arch Intern Med, 2005;165:1005–10)
A regular exercise program reduced carcinogenic inflammation, strengthened the immune system and improved mental processing by increasing apoptosis and by lowering cancer-inducing insulin-like growth factor 1, DNA damage and gene mutations (Br J Cancer, 2011;105:S52–73).

Why Don't More Oncologists Recommend Exercise to Their Patients?
Oncologists have training to prescribe surgery, radiation, and chemotherapy. If doctors do not exercise regularly themselves, the chances are that they know little or nothing about exercise and would not know how to tell others how to exercise. Furthermore,
• none of the doctors' oncology societies have made specific, detailed recommendations on how cancer patients should start and maintain an exercise program,
• insurance companies do not provide reimbursement for cancer rehabilitation, and
• oncologists have no local referral base for effective exercise programs for cancer patients.
The way that a doctor practices medicine is governed by the "Standard of Care" which is defined by lawyers, not by doctors. Most doctors practice medicine in a manner dominated by fear of malpractice lawsuits, and a cancer patient who injures himself or herself during a prescribed exercise program is a potential lawsuit.

Fitness Programs for Cancer Patients
A model program called FitSTEPS for Life (FSFL) was started in 2001 as an evidence-based cancer rehabilitation program that charges no fees, is community-based and is offered to cancer survivors from diagnosis onward. In the last 12 years, more than 14,000 referred patients have attended more than 350,000 exercise sessions at 13 community-based locations. To be accepted by FSFL, a cancer patient must be referred by a physician with specific recommendations on the patient's limits for safe exercising.

Rules for Exercise for Cancer Patients
I can recommend no specific exercise program for cancer patients because the amount of exercise a cancer patient can do is limited by level of fitness, extent of disease, treatment regimen and other variables. In general, all exercisers — healthy or not — should follow these rules:

• Stop exercising when your muscles start to hurt, burn or feel tight. If you keep on exercising, your muscle fibers can start to tear and run out of their stored sugar supply. Your body always talks to you and tells when this is happening. Failure to listen to your body is the most common cause of exercise injuries.

• Take the day off when your muscles feel tight or hurt after you have warmed up for five minutes or more. It is normal for muscles to feel sore when you first get up in the morning, but they should feel better after you have exercised for five to 10 minutes. Soreness after warming up means that your muscle fibers are damaged and are at increased risk for tearing if you exercise that day. Sometimes you can get away with exercising at reduced intensity on days when your muscles feel sore, but often it is best to just stop for the day.

• Stop exercising immediately if you feel increasing soreness in one spot, which can mean that a muscle is about to tear or go into a spasm. You can prevent many injuries just by stopping exercising when you feel pain in one spot and do not have pain in the same spot on the other side of your body.