Explain why exercise programs must increase in difficulty and duration over time to remain effective.

Exercise programs must increase in difficulty and duration to remain effective because of the principle of overload. As an individual exercises at a higher level, the body adapts to the increased demand and this higher level eventually becomes your body's new normal.

Explanation:

answer: when you start thinking negitivly and start having suicidal thoughts

or harming yourself, sadness is part of depression as well as fear and anger combined

you would have a std. i hope this .