What can contribute to fatigue or drowsiness while riding?

Poor sleep is a significant factor that can contribute to fatigue or drowsiness while riding. When a rider does not get enough quality sleep, it can impair cognitive functions, reaction times, and overall alertness, which are crucial for safe riding. Sleep deprivation can lead to slower response times, decreased attention to surroundings, and difficulty making quick decisions, all of which can increase the risk of accidents on the road.

The other factors mentioned, while potentially impacting comfort and performance, do not have the same direct relationship with sleep deficiency. An exciting morning ride might actually energize someone rather than cause fatigue. Overeating before riding can lead to discomfort rather than drowsiness, and excessive hydration is generally more about ensuring proper hydration than contributing to fatigue. Thus, the clear connection between poor sleep and its effects on a rider's capabilities makes it the most relevant choice in this context.