I frequently hear that beverages with caffeine or alcohol are not good for replenishing fluids and preventing dehydration. But in reality aren't they just a bit less effective at hydrating your body than other beverages? In other words, if you were stuck in the desert with nothing to drink but beer, coffee and cola, would you actually be worse off and die of thirst sooner if you drank these beverages versus not drinking anything at all?

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?

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?

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 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?

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?