1) When I do a 3-mile or 5-mile run, I run for time and try to finish with nothing in the tank. The closer I get to the end, the more I push myself, because I know I don't need to sustain the effort much longer. When I stop running, I suddenly get very light-headed and dizzy. It never happens while I'm running. I walk briskly while I'm warming down, but that doesn't prevent it. Why does this happen? Is it dangerous?

2)  Sometimes after jogging a while, or cycling a great distance, my head begins to spin and I feel as if I'm going to pass out. Is it normal to have feelings like these, and if so, how intense should these feelings be?

1) Is it better to eat before or after exercising? I've recently started a fitness program and am not sure which way is the best.

2) Is it bad to eat before you have practice or a game in basketball?

I have two questions:

(1) What are the benefits of jumping on a mini-trampoline?

(2) Are there any benefits to using a hula-hoop?

As you can probably see, I'm looking for exercises that are fun.

It's been about three months since I worked out regularly. I find that lifting for strength (i.e. 80% of max for 5-8 reps) causes me to feel nauseated about 3/4 through the workout sometimes, so that I can't bring myself to finish. I took a weight training course last semester and was affected the same way every once in a while. I warm up, stretch before and after, breath when I lift, drink plenty of water, take care not to eat 1 hour before working out, skip a day between workouts, don't lift more than I can handle (I reduced the weight from what I ended on in the class to a seemingly suitable weight. I got a 98 in the class incidentally). What's going on?

1) I'm worried. What happens if you eat your own sperm?

2) Today a girlfriend and I were discussing the nutritional value of sperm. While performing oral sex, if you swallow, I was told that it is very high in protein. However, I was also informed that it is very high in calories. This may seem like a weird question, but I would like to know what nutritional benefits are involved when "swallowing" and how many approximate calories are in a man's ejaculation? Thank you for your help in this matter.

1) I work out on my treadmill 20 to 30 minutes a day, usually one to two miles. My husband says that there is a minimum and maximum heart rate. Is there a formula that I can use to calculate this information? Please advise.

2) Is there an equation that would relate the relationship between exercise and heart rate. I understand the maximum and minimum heart rate equations for exercising. I would like to know if someone who is at their max. heart rate would be able to predict their heart rate if they increased their intensity. I am looking for something relating work intensity to heart rate.