Whether the activity is self-directed leisure such as walking or organized sports, the body in motion increases the risk of injury. According to recent studies, approximately 20% of all injuries treated in emergency rooms in the United States each year are activity-related, involving approximately 7 million people. However, the total number of activity-related injuries requiring professional medical care in the United States each year is at least double this estimate.

To ensure that the positive benefits of physical activity are not undermined by pain and loss of function caused by injury, and to reduce the financial burden of treating activity-related injury, it is critical to understand the factors that increase the risk of injury and the approaches that can be used to reduce the risk of sustaining such an injury.


Physical activity injury occurs when a body part or system is unable to withstand a physical demand or load placed on it. The demand can be mechanical (e.g., a soccer tackle resulting in a broken leg), thermal (e.g., high atmospheric temperature during a marathon resulting in heat stroke), or radiation (e.g., sunburn during a swim). Failure can occur as a result of a single incident (i.e., an acute injury, such as a sprained ankle) or as a result of cumulative overload over time (i.e., an overuse injury such as “tennis elbow”).

An injury occurs as a result of a complex interaction between demand characteristics (frequency, intensity, duration, type), individual characteristics (age, sex, level of fitness, technical expertise), and environmental characteristics. Injury prevention entails manipulating one or more of these characteristics to ensure that the demand does not exceed the body’s tolerance level. In general, this can be accomplished by lowering the demand, increasing the body’s functional level, or managing both.

Lowering Demand On the Body

The demands placed on the body during physical activity can be manipulated to prevent injury by adjusting the characteristics of the demand and some aspects of the environment. The most basic approach an individual can take is to ensure that the frequency, intensity, duration, and/or type of demand match the functional capacity of the body, and the key element is to be conservative. It is critical not to overestimate one’s ability when beginning a new activity or attempting a more advanced level of participation. This is a common source of activity-related injury.

For example, a normally sedentary person is more likely to sustain an injury such as blisters, muscle strain, or post-exercise muscle soreness from a 5-mile hike than someone who regularly hikes 3 to 4 miles or more. Similarly, even for experienced hikers, a sudden increase in the intensity or duration of a hike—for example, hiking in a very steep region instead of the usual flat trails, or abruptly increasing from a normal hiking distance of 5 to 20 miles—can increase the risk of injury.

Conservatism entails starting with a demand that is well within one’s ability to tolerate it and gradually and progressively increasing the demand over time. This causes the body to adapt to the demand and increase its functional capacity to withstand higher demands. The optimal magnitude and rate of change of demand vary greatly across activities, but recreational and sports organizations, as well as medical professionals, can provide model programs.


Furthermore, the impact of a demand on the body can be reduced by using appropriate equipment such as shoes, clothing, gloves, helmets, elbow and knee padding, shin and mouth guards, eye protection, breakaway bases, quick-release bindings, and so on. Such equipment must be of high quality and appropriately sized in order to be effective. It is critical to determine whether a manufacturing standard exists for a specific type of equipment and, if so, to purchase equipment that meets the standard.

For example, in the United States, the Consumer Product Safety Commission’s (CPSC) standard for bicycle helmets is required by law, but not in other parts of the world. Correct fit is especially important for children, who may not have access to appropriate sizes. An oversized helmet will not only not provide adequate head protection for a child, but it will also obstruct normal head movement and vision, increasing the risk of a fall and neck injury.


Finally, adhering to the rules and regulations that govern various physical activities can reduce or eliminate the risk of certain types of injuries. Rules may be enacted to protect competitors or to prevent high-risk situations and environments.

The rule prohibiting American football players from hitting an opponent with the top of their helmet is intended to reduce the tackler’s risk of spinal injury. Pool regulations that require fencing or access barriers create an environment that is designed to prevent drowning in unsupervised pools. Knowing and following the rules and regulations is a simple but crucial step in preventing activity-related injury.

Increasing the Body’s Functional Level

Although many personal characteristics are linked to an increased risk of injury during physical activity and sport, not all of them are modifiable. Age, gender, and the effects of previous injury are all non-modifiable attributes. However, it should be noted that nonmodifiable factors do not have the same influence on injury risk in all circumstances, and designing effective prevention programs necessitates a life-cycle approach.

According to the American Academy of Orthopaedic Surgeons, 50 percent of scholastic sports injuries are caused by overuse. This is not a common problem in children and adolescents who engage in unstructured or recreational activity because they do not continuously repeat the same motion for long periods of time. However, in unorganized sports settings, skill development necessitates a great deal of repetitive motion, which many young athletes are not physically prepared for.

Similarly, in older adults, deteriorating balance control is a common feature that raises the risk of injury. Falling is, in fact, the leading cause of both nonfatal injuries and injury death in people over the age of 65. Recognizing the changing physical and psychological characteristics of individuals as they age is a critical component of effective injury prevention.


As previously stated, the fundamental approach to increasing the functional level of the body is to begin slowly and gradually increase participation/effort. While this is common practice in the context of organized sports, it is less common in the context of informal recreational activities but is equally applicable. The underlying mechanisms for increasing functional capacity for different activities are the same; only the specifics of each program differ.

Consider the parallels between marathon training and a full day of gardening. Progressively increasing mileage and/or intensity within a prescribed format (e.g., limiting increases to less than 10% per week) is recommended for someone wishing to run a marathon without injury. Similarly, to reduce the risk of musculoskeletal injury from a full day of gardening stooping, squatting, digging, and hauling, participants should begin with shorter and/or less strenuous work periods and gradually increase the work time and effort. While programs to improve strength and endurance for those interested in competitive sports are readily available through coaches or the internet, physical and occupational therapists, certified athletic trainers, personal trainers, and certified strength-and-conditioning specialists can provide model or personalized programs for recreational or leisure activities.


Physical activity research has consistently revealed that the lower extremities, particularly the ankles and knees, are the most commonly injured areas of the body. This is not surprising given that most activity involves walking, running, jumping, or other uses of the legs and feet, but it is not unavoidable. Balance or proprioceptive training programs have been shown to reduce the risk of lower extremity injury in a variety of activities and are simple to incorporate into a daily routine.

While emerging research supports the recommendation of strength and endurance training as well as improving balance to prevent injuries, current research on stretching for flexibility to prevent injuries is inconclusive. Stretching as a warm-up before activity does not appear to reduce injury risk, but it may be beneficial as part of an activity-specific warm-up protocol for performance and can be most effective for increasing flexibility when done at the end of activity. However, activity-specific warm-up is an important component in lowering the risk of injury.

Depending on the activity, general recommendations include beginning with 30 to 50 percent intensity and gradually increasing to 70 percent intensity. Also depending on the activity, the duration of the warm-up and the appropriate time prior to activity will differ.


Recommendations for lowering the risk of activity-related injury are only useful if participants are aware of them and willing to follow them. Improving understanding of activity risks and appropriate methods to reduce risk(s) through video, the Internet, seminars, and clinics is becoming an increasingly important aspect of injury prevention. Although sports and public health organizations are developing more effective delivery methods to disseminate research-based best practices, it is ultimately the individual’s responsibility to ask questions and act on available recommendations to reduce activity-related injury risk. Including as many recommendations as possible in one’s physical activity routine increases the likelihood of safe and beneficial physical activity.

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