What physical factor increases the risk of positional asphyxia?

The physical factor that increases the risk of positional asphyxia is excessive weight or obesity of the individual. This condition can lead to reduced lung capacity and may impair the body’s ability to breathe effectively, especially in certain positions. When an individual is overweight or obese, the mass of fat can restrict the diaphragm's movement, making it more difficult to take deep breaths.

In cases of positional asphyxia, where body positioning can lead to restricted airflow, an individual with excessive weight is at greater risk. For instance, when someone is placed in a position that compresses their chest or abdomen, excess weight can exacerbate these conditions, ultimately leading to inadequate ventilation and potential asphyxia.

Other factors listed, such as physical fitness, time spent upright, or age may influence respiration but do not directly link to positional asphyxia to the same degree as excessive weight does. Physical fitness generally improves respiratory function, and while age can be a factor in overall health, it does not specifically increase the risk of asphyxia related to body position. Time spent upright does not have the same direct impact on airflow as the presence of excessive weight.