Breast cancer treatment left Debbie Mendoza so exhausted that cleaning the kitchen could wear her out. The retired teacher wanted to be active again but wondered how she could exercise without any energy.
She began with two minutes of movement a day through MD Anderson Cancer Center’s Active Living After Cancer program. Two minutes gradually became 10, then 20. Eventually, she was walking her dog daily, following home exercise videos and attending a gym class.
“I feel so much better, and my confidence is higher,” she told MD Anderson. “I definitely have more energy now than I did a year ago.”
October is Breast Cancer Awareness Month, and Mendoza’s experience illustrates a connection that deserves more attention. Physical activity is associated with a lower risk of developing breast cancer. It also can help people maintain or rebuild strength and energy during treatment and recovery.
Both findings add to our understanding of how fitness supports health throughout life.
Movement and lower risk
About 1 in 8 American women will develop breast cancer during her lifetime, according to the American Cancer Society. An estimated 321,910 women will be diagnosed with invasive breast cancer in 2026. The median age at diagnosis is 63, and about 83% of diagnoses occur among women 50 and older, the CDC reports.
The most physically active women had a 12% to 21% lower breast cancer risk than the least active in an analysis of 38 studies cited by the National Cancer Institute. Benefits appeared both before and after menopause.
Researchers are studying possible explanations, including exercise’s effects on hormones, inflammation and body weight. Much of the evidence comes from observational studies, which identify associations rather than prove cause and effect.
Exercise cannot eliminate breast cancer risk or replace screening. But the connection gives regular gym visits, neighborhood walks, and other activities another purpose.
Strength during treatment and recovery
Breast cancer also has a fitness dimension after diagnosis. Treatment can leave people fatigued and struggling with familiar activities. Some treatments contribute to bone loss, while preserving muscle and physical function becomes an important part of care.
“This can make exercise feel like a daunting task, but doing some exercise is better than doing none,” Dr. Erika Rees-Punia, an American Cancer Society researcher, said in a 2025 press release.
Aerobic activity and resistance exercise during and after treatment can reduce fatigue and improve physical function and quality of life, according to evidence reviewed by the National Cancer Institute. The American Cancer Society also identifies benefits for muscle strength and range of motion. Exercise programs account for treatment effects and each participant’s abilities.
Strength helps with carrying groceries, climbing stairs and keeping up with daily routines. Energy makes room for activities and relationships that illness can disrupt.
Mendoza’s return to walking her dog and attending gym classes puts a human face on the research. Her progress shows how movement can become part of living well again — and why fitness matters at every stage of life.
Holly Kouvo is a personal trainer, functional aging specialist, senior fitness specialist, brain health trainer, writer, and speaker.