According to recent research by the Centers for Disease Control and Prevention, folks who volunteer on an environmental project are three times more likely to meet recommended levels of physical activity than those who don't. The training necessary to be in shape to maintain trails, remove fencing, erradicate invasive plants or backpack into a remote setting and spend a week doing manual labor is beneficial to your everyday life.
Personal health: Physical activity can control weight, control high blood pressure, reduce symptoms of depression and anxiety, prevent osteoporosis, improve balance and circulation, reduce risk of type 2 diabetes, heart attack and colon cancer, and increase your overall sense of health and well-being. The social interaction and teamwork during the project will increase your sense of empowerment and self-worth.
Environmental health: The physical effort during the project improves the condition of the environment by addressing the detrimental impacts of overuse, erosion, littering, etc. and creates a safer environment for the larger community.
A reporter once characterized a Wilderness Volunteers trips as a fantasy camp for anyone who ever dreamed of being park ranger or naturalist but found themselves working indoors instead.
Sign up for a trip, and then spend the time to be in great shape for it; you'll be glad you did!
John Moeller training for backpacking.