How do I not get so tired in cardio?

So I ran track in high school my first two years, then because of multiple leg injuries, I stopped and just did field events. Now in college, I'm trying to get my cardio back up to 'get my legs back underneath me'. I was a very good runner back before...

Lately I've been getting terribly tired after working out. Usually I get around 30 - 45 minutes of moderate cardio - aerobics, jogging, biking. But I've been feeling like a reck after my workouts! My heart speeds up and I can't seem to catch my breath...

What can I eat to gain weight and have energy? I'm looking for suggestions, recipes or advice on things I can do to gain weight and have a more constant level of energy throughout the day. Searching for information on weight gain for females on the internet...

My goal is to overall tone my body (not lose weight...or at least alot...dont' need to) AND most importantly, lose my beer belly (genetics, althought i'm a very slim girl) and tone it completely. I started my workout routine again mid May by doing swimming...

im a full time tennis player that does about 3 hours a day tennis atm and up to 2hours fitness. hoever recently iv been going away to tournaments and not doing much fitness or cardio. iv come back and just practicing. but i seem to be so tired all the...

im a full time tennis player that does about 3 hours a day tennis atm and up to 2hours fitness. hoever recently iv been going away to tournaments and not doing much fitness or cardio. iv come back and just practicing. but i seem to be so tired all the...

I've had some problems with a high resting pulse (120-150) because of anxiety, but now my resting pulse is normal (between 60-77, usually). When I get up though, my pulse usually shoots to about 80-90, and now (and I don't know if this has something...

tired too fast? how can i run really fast but have more stamina so not to get tired too fast too soon? how can i develop more stamina so i can run faster longer???? can a cardio expert please tell me. thank you.

Hi, Im suffering from really bad anxiety, or so I THINK Im suffering from really bad anxiety. I havnt ben to a doctor yet, but I need to go soon... I get sick to my stomach and sometimes feel like I want to throw up because knowing that we will die one...