Why is it I can always run a greater distance on a track than I can on a treadmill? On a track, I can run five or six miles, but on a treadmill, I can only go a maximum of three or four, then I tucker out. Is it because I get more bored on a treadmill, or is there a more physical explanation?

I have been chewing and spitting large amounts of food (pretty much always sweet stuff — pastries, chocolate, etc.) almost every night for eight or nine months. I am eating a healthy, balanced diet otherwise, maybe a little on the lower caloric side (1300 to 1500 calories per day). My chewing and spitting sessions usually follow a balanced meal. I know this is a type of eating disorder. I have done a lot of research online and I know that there are side effects, although they vary depending on who you ask. Some sites mention that chewing and spitting activates the release of insulin and results in hyperinsulinemia, insulin resistance and weight gain. Is this true? How long would it take to develop these problems? Are these reversible if I were to stop this behavior?

Are there other types of eating disorders other than anorexia and bulimia? For example, I have this fear of unnecessary fat in food and eat everything "plain," that is, without butter, oil, dressing, or sauce, etc. I thought that it's good that I'm this health conscious, but my friends say that it's a little obsessive. Is this an eating disorder?

I'm curious to know if going to the gym increases sexual drive? I am a female in my 20s and recently started an exercise routine (running and weights), and I have noticed that my sexual drive has increased significantly. There have been no other major changes in my life, and I have been dating the same man for close to two years now, so I can think of no other real reason why my libido would have increased. Is there any real connection between working out in the gym and beneath the sheets?

What is the best way to prepare, health wise, before a big test such as the SAT, LSAT, MCAT? What foods do you recommend to keep my "brain moving?"

Does altitude affect calorie-burning? That is, if I do the exact same workout twice — once in New York City and once in Colorado — will I burn more calories at the high altitude? What things DO affect how many calories you burn in a workout?

I have heard that if you exercise/work out in the morning before you eat breakfast that it will cause your metabolism to increase throughout the day, helping you to burn calories. Is this true?

A friend of mine and I were disagreeing about this point and I thought maybe you could help. I have heard that it is not possible to both lose fat and build muscle mass simultaneously: ideally, a person should do cardiovascular exercise with dieting to lose extra body fat, and then start to focus on building up muscle mass. He says it's possible to both burn fat and build up muscle over the same period of time. Which is the case?

I have a question about walking for weight loss. My walking buddy believes the theory of walking distance is what helps you lose weight best versus my theory that it is the speed at which you walk that matters. So, could you help me figure this one out? Which matters most in ultimate weight loss: speed or distance?

When working out in the gym, machines, such as treadmills and stationary bikes, show how many calories you are burning. Are these calculations correct, or is it just something to keep the participants happy?

After practicing yoga in normal temperatures for years, I recently attended a heated yoga class (heated quite hot: 95 to 100 degrees!). The experience left me dizzy, nauseous, and completely enervated. Afterwards, I expressed my concern to the teacher, asking why the studio needed to be so hot. She "explained" that by sweating, supposedly the body releases "toxins" and that my nausea and dizziness must indicate that I need to "detox." Personally, I think I was suffering from heat exhaustion. I've heard this silly explanation more than once, as many people seem to believe toxins are released through sweat. But is that true??? And — next question — doesn't exerting oneself in extremely hot temperatures seem like a recipe for dehydration? Are their any benefits that make it worthwhile, or is all this heated yoga just nonsense?

I'm a college student and also a bodybuilder. I've become aware of very high protein intake amongst bodybuilders at my gym. I'm skeptical as to consuming as much protein (around 225 grams) a day like the bodybuilders at my gym do. Do bodybuilders need more protein? And if so, how much more?

I was anorexic for three years and I have been in recovery for two. At the moment, I am doing well. I have a healthy weight, I eat a balanced diet, I work out regularly though not excessively, and I feel good. However, I haven't had my period in about three years now. I had been told it would come back once I reached a healthy weight, but so far, no deal, even though I've been at this weight for over a year now.

Before I became anorexic, I did get my period regularly. I am 23 years old. I am taking a calcium supplement daily to prevent osteoporosis, but I would feel more comfortable if I did get my period again. What is going on? How worried should I be? Should I go see a doctor? What can I do about this?

I have recently learned that in order to burn fat as a fuel, your body requires carbohydrate. Up until this point I had been doing cardio training first thing in the morning on an empty stomach, as I had read that this is optimum for fat burning. However, now I have a small carbohydrate snack before I train in order to prevent my body using lean muscle tissue as a fuel. Today I have again read in another book that training on an empty stomach first thing in the morning burns the most fat. I am a little confused over the best thing to do! I train with weights twice a week and do cardio three times per week. I do want to maintain my lean muscle, but am looking to reduce my body fat.

Is it bad to exercise while slightly drunk? Some friends like to hike and drink beer. I find that I get flushed easily, and tire more quickly. What's going on?

I am a wrestler and have very great ambitions within the sport. I lift weights for five to six hours a day, making sure I perform every set to failure often including negatives as well. In addition to working each muscle group two times a week, I make sure to give each muscle group 48 to 72 hours of rest. Recently though, I have learned that training longer than an hour a day can have a catabolic (muscle breakdown) effect on your body. This was very concerning to me because muscle-wasting during my training seems truly counter-productive, but I am also aware that a decrease in training may lead to muscle atrophy and that also poses a deep concern. I have also learned that cardio and even sleep can have a catabolic effect. I will have to cut my training time eventually due to time restrictions during the season because of school day and team practices, including traveling time and homework. I am posing a couple of questions within this letter: 1) Can I reduce the volume of my routine to about an hour and still make gains that are comparable or better to those I experience with my five to six hour workouts and if so, how? 2) Is catabolism truly a legitimate matter to be concerned with?

I've been told that every two to three weeks, I need to change my weight training routine or else my body will become too accustomed to it and I will stop seeing results. Is it really necessary for me to change my entire routine, or do I only need to increase weight and/or repetitions?

Hot yoga is becoming more popular every day but there is a lot of conflicting information regarding benefits versus injuries. Most of the information does not quote sources and is therefore is difficult to follow up on. It has unquestionably helped me become a more flexible person but there is a lot of information on the net regarding horrific injuries including slipped discs, muscle tears, neck injuries, emotional problems, and even strokes. Is there a research-based, or at least a factual breakdown on the health benefits of stretching at temperatures above body temperature versus the injury risk of exercising at temperatures above body temperature?

I was bulimic for about four or five months and went from 5'6.5" at 115 pounds to 95 pounds. I have not told anyone, and will not, so please don't ask me to, but I am back up to 110 to 112 pounds and pretty much graze throughout the day so I don't throw up. I mostly snack on white bread, fruit, potatoes, and cereal in large portions, but want to stop and eat a healthy, more balanced diet. The problem is, I am not sure what a healthy weight should be. Charts say I am too skinny, but I don't believe it because I know girls in the media are thinner than me and they seem fine. I want to be as small a weight as possible without being unhealthy. I skipped my period for three months but did get it in January. I have not lost any weight since then though, and I should have gotten my period about a week ago but didn't. I don't understand, it is so confusing, can you help me?

I'm an athlete, and about a year ago, I purchased one of those ab rollers. One time, I was going through the motions and I experienced an orgasm. Now, it happens about every time I use it. I thought it was extremely weird, but then read where women experience orgasms through lots of things. I was just wondering how it is possible for those feelings to happen just by working out my abs. Also, what are some other weird ways that women have had orgasms? Thanks so much.

I wanted to know how many days of rest is recommended between workouts. I heard it was three days on to one day off...is this enough? I workout on a treadmill for 50 minutes every day and have for the last 14 months. I was not aware of how rest played a very important role until I recently read a brief article on it. I guess my question is, do I need to take that day of rest and how important is it?

I am writing in hopes that your answer to this question will help other readers. A few years ago, when I was in college, I discovered that my college roommate was bulimic. My boyfriend and I found evidence in the mornings that she had been vomiting on a daily basis; she also developed weird eating habits (at 6 A.M., she would wake up and buy two pints of ice cream and eat it all, and then not eat for the rest of the day). We didn't know how to address the problem, and were afraid of hurting her. When we called the Health Service, they took the "my best friend is bulimic" line to suggest that I was bulimic instead! I didn't want to become the food "hall monitor" — are you eating? What did you eat today? etc. — but we tried to include her in healthy meals.

Eventually, some other stress factors in her life calmed down and her binge/purge behavior seemed to subside. However, I've always regretted that I couldn't attack this situation head-on. Do you have any advice for people that might be in a similar situation?

A friend of mine bought me a month's worth of yoga classes over the summer. I loved it! I've never found an exercise/fitness regimen that I actually WANTED to stick with. It helped with a lot of my long-standing physical issues (balance, back pain, stress, fatigue) and was a perfect balance of stretching and strengthening for my fitness goals. The only problem is that now that my month is over... I can't really afford to do it anymore. I've looked all around for inexpensive and conveniently located studios, but I can't find anything that's in my price range or fits in my schedule. What resources are there for broke aspiring yogis? Are there any guidelines for practicing yoga at home? Are there any exercise routines that are similar to yoga (i.e., low impact, stretching + strengthening) that are less expensive or easier to do without an instructor?

I know there are video games out there now that require you to move more, unlike traditional video games. Are these games, like Wii Fit, a good way to be more active or are they doing more harm than good?

For as long as I can remember, I've been using my back muscles when I did sit-ups. In fact, I distinctly remember the first time we did them in second grade. After a few reps, it was already so painful that I was having trouble breathing properly. Being eight years old, however, I didn't realize this was a warning sign and assumed it was normal.

Flash forward ten years, and I have almost no strength in my abdominal muscles. I've tried to teach myself to do curl-ups properly, but no matter how hard I try, I can't even lift my head without using my back muscles. Exercise balls are no help either. Even when I concentrate on using my abs to keep myself steady, my back is still doing 95% of the work.

So, in short, I have two questions: Am I at risk for having damaged my back from years of abuse, and how can I work on strength training my abs now?

A friend of mine takes laxatives to keep her weight under control. The directions on the box say that you should only take two a day for no more than a week. She has been taking two to six a day for two months now. I was wondering what possible physical side effects might result from this kind of activity.

I have bowlegs. It is quite frustrating because I cannot do exercises that isolate and tone the thighs (lunges, squats, etc). When I do squats, my pressure/force comes from the calves and the knees, but not the thighs. Reason being is that the legs are not properly aligned, and pressure/force cannot go up to the thighs. It even hurts when I do squats because they involve bending the (crooked) knees. Are there any alternative thigh exercises?

I am 18 years old and I am determined to lose a few pounds and tone my body by the end of May. I just began running and I'm starting off by running a mile and hope to work up to a four-mile run four or five days a week. My diet is generally a bowl of cereal in the morning, and a turkey or ham sandwich with some type of fruit and a bottle of water. Dinner is something different every day, but usually healthy. I also have been doing an ab workout for about seven minutes after I run. Is what I'm doing effective? What are your suggestions?

I know most of us have seen the ads to buy various muscle toning equipment that uses electric pulses to "build more tissue" (hypertrophy), and I was wondering what you thought about this way of "toning muscle." Also, if you knew where else I could go to further my research on these sorts of devices?

Thank you very much for your help in advance.

About five days ago while I was doing step aerobics I stepped down incorrectly and injured my foot. It turns out, after seeing the doctor, that I cracked a bone on the outer side of my foot and will have to wear a boot cast for about four weeks. My question is, since I can no longer do aerobics, what other kinds of exercises can I do to help me lose weight? I already do weights, abs, and any other type of leg exercise that don't involve me standing, but I don't feel that this is enough and since I am prone to gaining weight easily, I really want to do as much as I can but in a way that I don't aggravate my injury or make it worse.

Do you have any suggestions for me on losing weight? I feel so intimidated going to a fitness center because of the looks I get. I really do. It seems like an individual has to be thin to go into fitness centers now-a-days. I should say some of them are that way.

Can you tell me a way to figure out my basic metabolism?

I have started spinning and I absolutely love it. Currently doing it about 3 times per week. My boyfriend says that spinning will cause permanent damage to my female genitalia, such as damaging the nerves, leading to reduced sensitivity and ultimately impeding my enjoyment of sex. I always wear the appropriate padded shorts. Is this true or not?

I swim three times a week for 40 minutes and sauna for 15. When I come out of the sauna my face is beet red and stays that way for about 1/2 hour — is this a sign of something wrong? Also, is it bad to work-out (sit-ups, push-ups) in the sauna?