30 Minutes of Cardio

This intreagued me. I do 10-20min of a workout every morning (well - I'm suppose to) - sometimes running sometimes 30 day shred. I have lost over 30# in about a year doing just that. So I googled this and found a trainer's blog (http://sheerbalance.com/brettsblog/4-indicators-you-do-too-much-cardio/) where she talks a little bit about this. The only other thing I founds was some amature bodybuilder posting that after 45 min your body starts to burn muscle tissue for energy (but that didn't seem to be the most reputible resource).

Here's a paste from the above referenced trainer blog (since the pasted URL didn't turn into a link):
Sometimes when I go to the gym, I have this urge to tell some of the most religious treadmill riders “Ma’am, Step away from the treadmill!” No matter how many articles and reports are written on the benefits of other than cardio, it never ceases to amaze me how many women (and men too…) relegate themselves to the endless monotony of the treadmill – or for that matter, any other piece of cardio equipment. Moreover, these individuals will do cardio for over an hour…sometimes hopping from one piece of cardio equipment to another…never even considering time in the weight room, in classes or outdoors.

Although there are definite benefits to doing aerobic exercise; strength, core and flexibility training all provide numerous health benefits that cardio can’t: They increase muscular and bone strength, increase lean body mass, safeguard against injury and boost metabolism while decreasing fat.

Is it possible you are overdoing the cardio? Here’s how to know:

1) Time: Unless you are training for a race, marathon or triathlon, there is no need to do more than 30 minutes of cardio (with your heart rate between 65% – 85% of your maximum heart rate) when you workout. Fitness Revamp: If you want to exercise for over 30 minutes, you are better off doing a 20 – 30 minute cardio session and another 20 – 30 minutes dedicated to strength training, stretching and/or core training.
2) You aren’t seeing results: If you are trying to lose weight, yet you aren’t seeing results, it may be because of too much cardio. Believe it or not the idea of ‘burning off fat’ does not stem from cardio…it stems from strength training. Fitness Revamp: Build in 20 – 30 minute strength training sessions 2 – 3 times a week.
3) Injuries: Too much wear and tear on your muscles and joints can end up in an injury…or even worse, multiple injuries. Incorporating flexibility and strength training helps to strengthen the joints which will prevent pain and damage to joints. Fitness Revamp: Take the time to stretch before and after your cardio sessions.
4) Boredom: Does it take a lot to motivate yourself to go to the gym? Doing the same type of exercise every day, of every week, of every year is…BORING! Working out should be fun and should make you feel good. Fitness Revamp: Mix it up. Take a class or two that interest you each week. Get into the weight room and do a few sets of bicep curls. Go hiking. Do things that motivate you and keep you interested. Being active is what is most important…not the time and mileage on a piece of equipment.
Do you think you are overdoing cardio? Have you found any of the above indicators true?

It's true. If you exercise for longer than 30 min:

1. Your muscles will shrink.

2. You will go into starvation mode.

3. Your hair will fall out.

4. If you are a woman, your uterus will fall out.

5. If you do cardio longer than 45 minutes, you will gain weight.

Don't believe me?



THIS person did 35 MINUTES of cardio:

Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise—a randomized controlled trial in overweight sedentary males

Mads Rosenkilde, Pernille Auerbach, Michala Holm Reichkendler, Thorkil Ploug, Bente Merete Stallknecht, and Anders Sjödin

1Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
2Department of Human Nutrition, University of Copenhagen, Copenhagen, Denmark

Submitted 2 April 2012. Accepted 30 July 2012.

Abstract

The amount of weight loss induced by exercise is often disappointing. A diet-induced negative energy balance triggers compensatory mechanisms, e.g., lower metabolic rate and increased appetite. However, knowledge about potential compensatory mechanisms triggered by increased aerobic exercise is limited. A randomized controlled trial was performed in healthy, sedentary, moderately overweight young men to examine the effects of increasing doses of aerobic exercise on body composition, accumulated energy balance, and the degree of compensation. Eighteen participants were randomized to a continuous sedentary control group, 21 to a moderate-exercise (MOD; 300 kcal/day), and 22 to a high-exercise (HIGH; 600 kcal/day) group for 13 wk, corresponding to ∼30 and 60 min of daily aerobic exercise, respectively. Body weight (MOD: −3.6 kg, P < 0.001; HIGH: −2.7 kg, P = 0.01) and fat mass (MOD: −4.0 kg, P < 0.001 and HIGH: −3.8 kg, P < 0.001) decreased similarly in both exercise groups. Although the exercise-induced energy expenditure in HIGH was twice that of MOD, the resulting accumulated energy balance, calculated from changes in body composition, was not different (MOD: −39.6 Mcal, HIGH: −34.3 Mcal, not significant). Energy balance was 83% more negative than expected in MOD, while it was 20% less negative than expected in HIGH. No statistically significant changes were found in energy intake or nonexercise physical activity that could explain the different compensatory responses associated with 30 vs. 60 min of daily aerobic exercise. In conclusion, a similar body fat loss was obtained regardless of exercise dose. A moderate dose of exercise induced a markedly greater than expected negative energy balance, while a higher dose induced a small but quantifiable degree of compensation.

I'm not a fan of cardio and you'll be hard pressed to see me recommend more than 30 mins of cardio top anybody, but the information presented in this thread seems suspect to me

Someone told me that doing any more then 30 minutes of cardio won't really do you any good. Is this true or not?