ABERDEEN PROVING GROUND, Md. – As a 40-year-old Army physical therapist with 18 years in the service, I am so thankful for the benefits that Army training has provided my body and joints. As a former infantry Soldier, I am thankful for the long runs and foot marches, the 100-pound ruck, for Ranger School and airborne jumps.Why?According to some public health experts, progressive strenuous exercise — especially during our younger years — provides a lifetime of health benefits like stronger bones and cartilage. New research is confirming that maintaining an active lifestyle throughout your lifespan is quite safe and beneficial for the body.“Wait a minute,” you may ask, “Doesn’t all that strain cause ‘wear and tear’ on your body?”According to a recent scientific study: no, not really. In fact, the opposite may be true. Researchers in Germany who studied healthy individuals for more than 14 years found that those who engaged in the highest amounts of physical activity had fewer changes in magnetic resonance imaging (MRI) of their spines compared to less active individuals. These changes are usually associated with the normal aging process, but appear to slow down with increased physical activity.Of course there are some limitations to the German MRI study. The participants in this research weren’t Soldiers. Also, although the German MRI study showed that being sedentary was associated with increased signs of aging in the spine, the design of the research cannot prove physical inactivity caused the changes to the spine.Despite the reassuring findings from the German MRI study, it is understandable that some Soldiers may worry they get too much activity since some research identifies elite running mileage as a risk factor for injuries.The average Soldier, however, competes at a much lower running mileage than elite athletes. This type of recreational running has actually been shown to protect the knee and hip joints from osteoarthritis.So rather than “wear and tear,” a more accurate description of the effect of physical activity may be “repetition and condition.” In other words, when your body undergoes regular, progressive exercise, your tissues adapt and become more conditioned. Research shows that active individuals have healthier, stronger joints compared to those who are sedentary. Tissues positively adapt to the mechanical loads and stresses from regular physical training.Of course, more is not always better, especially if your body is not used to an activity. Excessive physical overload can lead to an over-use injury. These types of injuries are common in the military and among athletes.If you have experienced an injury — like falling, twisting, or doing too much activity that your body was not conditioned for — and you have treated your injury with relative rest for 4-6 weeks but continue to have problems, then it is time to get help from a healthcare provider.The good news is that most of these injuries heal. Even worrisome injuries such as disc herniations, meniscal tears and cartilage damage often heal well. Healing may take a long time and may require periods of relative rest and activity modification following an injury.After a serious injury, it is not realistic to expect to be 100 percent symptom-free, but the human body can achieve a new normal. Individuals can be highly active even following major injuries.Since over-use injuries are so common in the military, it may seem that doing less activity will protect your body and joints. The German MRI study showed that too little activity, however, can be just as unhealthy for your body as too much activity. This explains why astronauts returning from space have weakened tissues and bones: their bodies face too little stress when living without gravity.It is best to train smartly and gradually build up your tissue conditioning and avoid these types of injuries in the first place. Here are some general tips that can help prevent overuse injuries:Follow a progressive plan. Many researchers recommend keeping training increases (distance, weight, or intensity) to around 10 percent a week. Take it a little easier every fourth week of regular training.Keep an eye on signs of over-training: difficulty sleeping, persistent feelings of fatigue, easy to catch illnesses.Change things up. A healthy body regularly changes how it moves to help manage stress and load.Ensure adequate sleep and nutrition.Engage in progressive, balanced strength-training.Remember, the human body is incredibly resilient and capable of adapting to the physical demands of military service and beyond. These adaptations take time, however!Army training is tough, but so is the human body. Scientific research is discovering more and more that regular physical activity does not necessarily result in harmful “wear and tear” on your body. Injuries are possible, but tissues heal and the benefits of physical activity — like better cardiovascular health and longer life — far outweigh the risks.With progressive repetition, your tissues will become conditioned. The benefits of being highly active will stay with you for life, especially if you maintain a healthy lifestyle.Editor’s Note: This commentary incorporates the author’s review of multiple academic journal articles examining training and sport injury causes and prevention, including studies conducted by his colleagues at the Army Public Health Center. A version of this article with all citations can be found at the Army Public Health Center P3 information site.The Army Public Health Center focuses on promoting healthy people, communities, animals and workplaces through the prevention of disease, injury and disability of Soldiers, military retirees, their families, veterans, Army civilian employees, and animals through population-based monitoring, investigations, and technical consultations.