What type of external barrier is highlighted by the challenges faced during workouts?

The choice of an injury from working out as the type of external barrier is particularly pertinent because it directly impacts an individual's ability to engage in physical activity. Injuries can create significant setbacks, not only physically by causing pain and restricting movement but also psychologically by leading to fear of re-injury or a decrease in motivation to maintain an active lifestyle. This barrier can hinder regular workout routines, making it difficult for individuals to achieve their fitness goals and maintain their overall health.

The other options, while they may present challenges as well, do not encapsulate the immediate physical impediment that an injury does. For example, a lack of fitness equipment can limit the variety of workouts available but does not physically prevent someone from exercising altogether. Similarly, a lack of family support might affect motivation and emotional encouragement but does not create a tangible barrier to exercise in the way an injury can. A safe area to work out is also vital, yet without the capability to perform exercises due to an injury, the location of the workout does not hold the same level of significance. Thus, injury stands out as a prominent external barrier interrupting one's fitness journey.