Not surprising and certainly has been my experience (despite the comments with respect to lymphoma and leukaemia). I think part of it is just getting the lungs and heart working more; in my case, in the early days of treatment, this reduced the risk of pneumonia as well.
Not to mention the psychological and emotional benefits of doing something. Quote:
When they combined the results, the researchers found physical activity both during and after cancer treatment was tied to improved energy. In particular, aerobic exercise such as walking and cycling tended to reduce fatigue more than resistance training.
“What we do know is there will be an appreciable difference; the average patient will get a benefit from physical activity,” Cramp said, though the actual benefit will vary.
For example, there were exercise-related benefits for people with breast cancer and prostate cancer, although not for those with leukemia and lymphoma.
“Some of the hematologic patients may not have the reserves to always tolerate the aerobic exercise,” said Carol Enderlin, who has studied fatigue and cancer at the University of Arkansas for Medical Sciences in Little Rock.
“They do not always have the oxygen carrying capacity, for instance,” because the disease and treatment affect blood cell counts. For those people, non-aerobic exercise or exercise at a lower does may be a better option, added Enderlin, who was not part of the research team.