That said, it’s crucial to understand that fitness can take many different forms (think of the contrast between a ballet dancer and a bodybuilder, or a sprinter and a gymnast). Fitness isn’t defined by a particular “look.” In fact, appearance alone doesn’t necessarily reflect someone’s habits or level of physical activity.

A well-known research paper from 1985 distinguished between the terms “physical activity” (any bodily movement that results in energy expenditure), “exercise” (physical activity that is planned and structured), and “physical fitness.” The paper defined physical fitness as a collection of attributes that people possess or develop, which determines their ability to perform daily tasks with energy and alertness, without excessive fatigue.

“As you get older, you lose muscle mass, which can significantly affect your quality of life. Strength exercises help build bones and muscle, and increased muscle mass protects your body from falls and fractures that are common in older age,” says Robert Sallis, MD, a family medicine doctor at Kaiser Permanente in Fontana, California, and chairman of the Exercise Is Medicine initiative with the American College of Sports Medicine (ACSM).


The ACSM defines strength or resistance training as exercises “designed to improve muscular fitness by working a muscle or a group of muscles against external resistance.” Examples of such activities include lifting weights, using resistance bands or your body weight, carrying heavy loads, and even engaging in strenuous gardening, according to the Physical Activity Guidelines from the U.S. Department of Health and Human Services (HHS).

Learn More About Why Strength Training Is Important and How to Do It

Flexibility and Mobility

Flexibility and mobility are essential components of healthy movement, as noted by the International Sports Sciences Association. However, they are not the same.

Flexibility refers to the capacity of tendons, muscles, and ligaments to stretch, while mobility relates to the body’s ability to move a joint through its full range of motion.

There isn’t a specific recommendation for the number of minutes you should spend on activities that improve flexibility or mobility (such as stretching), and the health benefits of these activities are not fully understood due to limited research, according to the HHS Physical Activity Guidelines. However, the guidelines do emphasize that flexibility exercises are important for overall physical fitness.

Additionally, the guidelines recommend that older adults incorporate balance training into their weekly fitness routine. Evidence suggests that regular exercise, including balance training, can significantly reduce the risk of falls among older adults, helping prevent serious and potentially debilitating injuries.

Learn More About Different Types of Flexibility Exercises and How to Become More Flexible

Rest and Recovery

Incorporating rest and recovery days into your routine allows your body time to repair the natural wear and tear that occurs in muscles during exercise. By definition, exercise places stress on the muscles and the body. The process of repairing or healing from that stress is how you become stronger and fitter. However, adequate rest after a workout is necessary for this recovery process to take place.

Recovery days can involve no physical activity at all or can include active recovery, which means engaging in low-intensity, low-impact exercise, such as walking or gentle yoga. Dr. Sallis generally recommends engaging in some form of activity every day, even if it’s just a 10-minute walk outdoors.

On rest and recovery days, the goal isn’t to be completely inactive; rather, it’s to avoid pushing yourself to the point where physical activity feels strenuous or challenging.