This may sound like something invoked by couch potatoes, but research has shown that too much cardio can actually do you more harm than good.
First things first - I am a cardio(vascular) freak and you'll probably find me beating away at a cross-trainer or in spinning class whenever I'm at the gym. I could go on for hours, so much so that guys have actually come up to me asking why I push myself so hard.
"You're already slim," one noted, while another insisted that my lack of a behind was a result of doing too much cardio. (Well, I'm Chinese. Hello?!)
Personally, at about 48kgs, I don't think I'm fat at all, and I'm definitely not trying to lose weight. It's more of that elusive post-exercise high I'm after, the kind that fills me with an inexplicable sense of euphoria every time after a gym session.
And so I pound away to the beats of Guetta and Tiesto, oblivious to the world - a routine I have been carrying out up to three to four times a week (sometimes five if I feel fat) for over three years.
So in considering the question, "Is too much cardio bad for you?" I would certainly be a very likely candidate for any of its detrimental long-term effects.
Yes, I'm sure we're all familiar with the benefits of cardio - stronger heart and lungs, weight loss, reduced risk of heart diseases and cancer, but as with chocolates and most things in life, too much of a good thing is usually bad ...
Too much of a good thing
To begin with, the question as to whether years of intense cardiovascular exercise could possibly be harmful to the heart is nothing new. Cardiovascular exercise itself has a reputation that seems to founder whenever a seemingly healthy distance runner, cyclist or other athlete drops dead while in action.
Of course, I suspect that such questions are sometimes invoked by couch potatoes looking for an excuse not to exercise. The sad truth is, they may not be entirely wrong.
In a March 2011 report published in The New York Times, a British study that focused on men who had been part of a British national or Olympic team in distance running or rowing found that athletes aged 50 or older (those who had been lifelong athletes) showed greater signs of fibrosis or heart muscle scarring compared to younger athletes (aged 26 to 40), or their older non-athlete counterparts.
Fibrosis, if it becomes severe, can lead to stiffening or thickening of portions of the heart, which can contribute to irregular heart function and, eventually, heart failure.
The affected men were, in each case, those who'd trained the longest and hardest. In short, those who had spent more years exercising strenuously, or completing more ultra-marathons were associated with a greater likelihood of heart damage in the study.
So just how much cardio should one engage in to reap its benefits without running the risk of overdoing it?
Diversify your routine
Exercise specialist Sim Lee-Archer recommends 30 minutes of moderate intensity cardiovascular exercises for at least five days a week, in accordance to the guidelines that have been published by the American College of Sports Medicine.
That means you don't have to kill yourself at the gym like what I've been doing.
"Ideally, one should burn about 150 to 200 calories for a 30-minutes session. So burning a total of 1,000 to 1,400 kcals a week would be good," says Lee-Archer, who is also the education consultant for the Federation of International Sports, Aerobics and Fitness (FISAF) International, and the managing director of Art in Movement, the official FISAF service provider in Malaysia.
She adds it is important to diversify one's routine. "The human body is built in such a way that it learns to adapt, and it adapts so well that if you keep engaging in the same activities, you'll hit a plateau because you're not challenging it any more.
"Also, you do not want to be doing the same thing over and over again because repetitive motions can cause strain to your joints, which could increase your risk of getting an injury," she says.
For instance, knee injuries are a common problem among runners due to the impact on the joints, especially for those who run on hard surfaces such as concrete. Proper footwear however, will help cushion the impact.
In any cardio workout, the muscles undergo stress, which in turn activates muscular hypertrophy, or muscle building. However, when you push the muscle too hard, the stress can cause potentially serious damage, including muscle pulls, muscle tears or damage to other supportive tissues, such as ligaments and tendons.
"You have to understand the nature of whatever sport or activity you're doing, and you try to counter or balance it with something else."
I had to learn this the hard way. I'd picked up spinning classes only last January, and I enjoyed them so much I started attending them at least four times a week, sometimes for back-to-back sessions.
Worst idea of my life. I got a little too skinny for my liking shortly afterwards (because skinny isn't sexy), and more alarmingly, my knees began to hurt, leaving me no choice but to forgo my beloved spinning classes.
The ordeal lasted for about two weeks, during which I felt depressed enough to want to stuff my face with a greasy bucket of KFC.
As Lee-Archer stresses (how I wish I'd met her earlier), moderation is very important. Understandably, most of us run just to stay in shape, but the problem arises when we overwork our bodies.
"For instance, when a non-athlete trains according to competitive criteria or conditioning, it's definitely too much."
She explains: "Marathon trainers for example, can go on the treadmill for up to two hours, and it is not uncommon for professional marathon runners to train up to three times a day - in the morning, during lunch and again in the evening every day.
"But whenever you become 'competitive', you are over-training because you're no longer exercising for basic health and wellness. You are now training for competition, and everything that deals with competition is not the norm."
Women are especially susceptible to getting knee injuries as a result of over-exercising, Lee-Archer explains.
"This is due to the genetic build-up of the female. Females have a wider pelvis compared to males, which means they have a larger 'quadriceps angle' or 'Q angle'.
"The Q angle is measured by creating two intersecting lines: one from the centre of the patella to the anterior-superior iliac spine of the pelvis; the other from the patella to the tibial tubercle. It is thought that this increased angle places more stress on the knee joint, resulting in an uneven weight distribution, which in turn, increases the risk of injury.
"Also, a woman who is bottom-heavy would be more prone to getting knee injuries than a woman with a more proportionate lower body; which is why it is important to find a sport or activity that actually suits your body type, and not just purely out of your interest for it, to reduce the risk of injury."
Of course, it boils down to common sense as well - if it hurts you, stop. Another way to mitigate the risk of injury is to balance up your cardio routine with resistance training exercises (weights).
From my personal experience and observation over the years, Malaysian women generally shy away from any form of resistance training for fear of turning into a she-hulk.
"Yes, a lot of women are afraid of bulking up and looking like a man, which they never will (not by natural means anyway)," Lee-Archer says knowingly.
Not to be confused with weightlifting or body-building, regular resistance training actually helps strengthen and tones muscles, as well as increase bone mass, which is a good thing, especially as we age.
I've been experimenting with free weights, simply because I'm not quite strong enough to use weight machines just yet. But lo and behold! Already I am seeing more defined abs and arm muscles.
Conversely, skinny men who are looking to buff up typically avoid cardiovascular exercises completely for fear of losing muscle mass. But Lee-Archer explains that such regimes can actually be counter-productive for those who dream of having that perfectly chiselled Brad Pitt body.
"By not working on your cardiac muscles (with cardiovascular exercises), you're actually compromising the development of your skeletal muscles (which occurs when you train with weights), which is of course, counter-productive to whatever amount of pumping you might do.
"Besides, they're not going to lose their muscle mass if they follow the guideline (30 minutes of moderate intensity cardio five days in a week), unless they train really hard.
"Some men are so eager to buff up, they resort to 'unnatural means' or supplements. But you've heard stories of people who get so big that their hearts fail to support their body. Balance is imperative," she cautions.
As Yap Mai Kuen, assistant fitness centre manager at Renaissance Kuala Lumpur Hotel and master trainer for FISAF Malaysia puts it: "Concentrating solely on resistance training is like having a nice car, but you're focused solely on the exterior. You put spoilers on it, you modify it, you spray paint it, but if you ignore the engine, your car will eventually break down."
The million-dollar question is: is a person who overtrains actually worse off than a person who doesn't train at all?
"That's a tricky one," Lee-Archer says, smiling.
"A person who trains will obviously be in better health than a person who doesn't train. The most important thing is that you find a balance."