Which of the following is a key factor that affects fitness loss?

Consistency of the exercise routine is a key factor that affects fitness loss because regular engagement in physical activity is essential for maintaining and improving fitness levels. When individuals consistently exercise, they can effectively build muscle strength, endurance, flexibility, and overall cardiovascular health. Inconsistent exercise habits can lead to periods of diminished activity, which may cause the body to lose the adaptations gained through previous workouts. This loss of fitness can happen relatively quickly, often within a few weeks, highlighting the importance of maintaining a routine to keep one's fitness levels stable.

While other factors like the type of equipment, time of day, and location can influence the effectiveness and enjoyment of a workout, they do not directly dictate the risk of fitness loss to the same extent that consistency does. Regular participation in exercise is the most significant determinant of maintaining health and fitness over time.