By Denny Watkins

Exercising while undergoing chemotherapy can help cancer patients overcome the treatment's debilitating effects and return to normal life faster.

That's according to a new study of 266 patients undergoing chemotherapy for testicular, breast, or colon cancer or non-Hodgkin's lymphoma. All the participants took part in a 6-month exercise program, but half started the program during their chemo treatment (3 months before their chemo was scheduled to end), while the other half started after chemo was finished.

Previous research has shown that exercise benefits cancer patients, but this is the first to look at how exercise timing can impact treatment's effects.

Those who worked out during chemotherapy saw a smaller drop in peak oxygen uptake, or VO2 peak — an indicator of overall fitness — after their chemo was finished. At that point, their VO2 peak had declined by about half as much as the other group’s (–2.8 mL/kg/min versus –5.8 mL/kg/min).

They also saw smaller declines in strength, quality of life, and physical function. And they reported less fatigue.

"Although patients are tired from the treatment, physical exercise can induce changes in muscle strength and increase physical condition," says study author Annemiek Walenkamp, MD, PhD, an oncologist at the University Medical Center Groningen in the Netherlands.

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Exercise produces cellular changes in the body, stimulating the production of mitochondria in muscle cells, Walenkamp explains.

"Having more [mitochondria] increases your body's energy supply. Also, exercise increases oxygen circulation. This allows you to more efficiently use energy."

If exercise can't be safely performed during chemo, then a program afterward can still help. In fact, all the study participants were able to restore their fitness back to baseline 1 year after completing the exercise regimen, no matter when they had started it.

Preserving lung and heart fitness matters for cancer patients, as it may improve chances of survival. A separate study found that for every additional 1 peak metabolic equivalent (the amount of energy you spend sitting still) cancer patients achieved during an exercise test, the risk of dying from cancer decreased by 25%.

What kind of exercise should patients do? In the Dutch study, participants did 30 minutes of cardio (stationary bike, treadmill) 3 days a week, 20 to 30 minutes of weight training twice a week, and a recreational sport like indoor hockey, soccer, or badminton once a week. They worked with a physical therapist for the first 3 months and were asked to keep up the routine on their own for the last 3 months.

More research is needed to determine the safest workout for different types of cancer, Walenkamp says. People with lung or bone cancers, for example, may need to be extra cautious and be sure to work with a physical therapist who specializes in assisting cancer patients.

"When safety is guaranteed, I suspect that all patients will benefit from such a program," Walenkamp says.