In the TED talk above, Dr. James O'Keefe, a research cardiologist and a former elite athlete, discusses an important point that can be difficult for some to accept, namely the fact that extreme cardio can actually do more harm than good...

I am about two years older than Dr. O'Keefe and had a similar running history. Dr. O'Keefe actually won the largest sprint distance triathlon in Kansas City five years in a row, from 1999 to 2004¹ . Although I was never an elite athlete like Dr. O'Keefe, I had run a 2:50 marathon previously. It is satisfying to hear Dr. O'Keefe validate what I have been writing about for years now. I suspect we both wised up and stopped running at about the same age, after many decades of intense endurance training.

The myth that extreme endurance cardio is good for your heart took off at full speed when, in 1977, Dr. Thomas Bassler boldly proclaimed that "completing a marathon confers immunity against heart attack." Many die-hard runners still believe this to be true.

However, in the years since, research has shown that the complete opposite may be true². According to one study, presented in the video above, once you reach 40-50 minutes of vigorous exercise per day, the benefits from your efforts plateau, and further efforts do not convey further improvements in life expectancy.

When it comes to light to moderate exercise, on the other hand — such as walking, housework, and similar less strenuous day-to-day activities — more is better. It's not as effective as vigorous exercise (performed less than about 40 minutes a day), but the more active you are throughout the day, the better your life expectancy.

Survival of the Moderately Fit

As Dr. O'Keefe says, "Darwin was wrong about one thing. It's not survival of the fittest, but survival of the moderately fit." If you can dance, or lightly swim, or jog at six miles an hour, your mortality rate plummets compared to someone who can barely walk a flight of stairs. However:

"Further attainments of peak fitness do not translate into further increases in life expectancy. It plateaus out," Dr. O'Keefe says. "We weren't born to run. We were born to walk, and we need to be walking more... you need to be moving your body more than sitting — every chance you get, move! "

I've often described exercise as a drug that needs to be taken in the ideal dosage to impart the optimal benefit. Too little, and you won't get any benefit. Too much, and you could do harm.

As Dr. O'Keefe describes, extended extreme cardio actually sets in motion inflammatory mechanisms that damage your heart. So while your heart is indeed designed to work very hard, and will be strengthened from doing so, it's only designed to do so intermittently, and for short periods — not for an hour or more at a time. Repeatedly and consistently overwhelming the heart by long distance marathon running, for example, actually prematurely ages your heart.

Veteran endurance athletes have a five-fold increased risk of atrial fibrillation, a dangerous irregular heart rhythm. Worse yet, some endurance athletes also present ventricular tachycardia (a heart rhythm faster than 100-120 beats per minute), which can lead to ventricular fibrillation — a leading cause of sudden cardiac death.

Runners Live Longer — But Only Those Who Run Within the Goldilocks Zone...

Dr. O'Keefe also summarizes new research about to be published, showing that, yes, runners do live longer — in general, nearly 20 percent longer than non-runners. The study in question followed 14,000 runners and 38,000 non-runners for up to three decades. And they found that, to optimize the health benefits from running, you'll want to run 5-20 miles per week — the ideal amount being 10-15 miles per week. Once you reach 25 miles or more per week, the benefits actually disappear!

Also, if you run too fast — over eight miles an hour — the benefits tend to go away (note we're talking about speed in long distance endurance running here, not interval sprinting). It won't make your health worse than a non-runner, but as Dr. O'Keefe says, if you put in that much effort, surely you'd want to get some benefit from it!

In order to obtain the health benefits and increased longevity from long distance running efforts, it seems to be best to limit your pace to six to seven miles per hour (about a ten-minute mile). Lastly, if you run seven days a week, the benefits also seem to disappear. The ideal amount was found to be between two to five days of exercise a week.

Another Danish study, also discussed by Dr. O'Keefe, found similar results. It followed 20,000 Danes since 1976, and found that joggers live about six years longer than non-runners, but again the benefit disappeared in those who overdid it... The best survival rates were among those who ran at a slow to average pace for a total of 1 to 2.5 hours per week, divided between two to three runs per week.

High Intensity Interval Training May Be the Ideal for Most

Mounting research is showing that the ideal form of exercise isn't related to long-distance endurance after all. Rather, short bursts of high intensity exercise has been shown to beat conventional cardio time and time again as the most effective and efficient form of exercise. It also provides health benefits you simply cannot get from regular aerobics, such as a tremendous boost in human growth hormone (HGH), aka the "fitness hormone."

According to fitness expert Phil Campbell and author of Ready Set Go, getting cardiovascular benefits actually requires working all three types of muscle fibers and their associated energy systems -- and this cannot be done with traditional cardio. Here's a quick review:

• Slow twitch (red muscle): Activated by traditional strength training and cardio exercises
• Fast twitch (white muscle): Activated by high intensity interval exercises (sprints)
• Super-fast (white muscle): Consists of fast twitch AND super-fast fibers, activated by high intensity interval exercises

Unfortunately, most traditional cardio and strength training exercises work only red muscle fibers, completely missing your white muscle fibers, which then atrophy. If your fitness routine doesn't work your white muscle, you aren't really working your heart in the most beneficial way. Your heart has two different metabolic processes: the aerobic, which require oxygen for fuel, and the anaerobic, which do not require any oxygen.

Traditional strength training and cardio exercises work primarily the aerobic process and the slow twitch (red) muscle fibers. On the other hand, high intensity interval exercises work your aerobic AND your anaerobic processes, which is what you need for optimal cardiovascular benefit. This is why you may not see the results you desire even when you're spending an hour on the treadmill several times a week. You're only working HALF of your muscle fibers!

In the case of these kinds of Peak Fitness exercises, less is more, as you can get all the benefits you need in just a 20-minute session performed twice a week. In fact, you should not do these exercises more than three times a week, as if you do it more frequently than that you may actually do more harm than good -- similar to running marathons.

Your body needs regular amounts of stress like exercise to stay healthy, but if you give it more than you can handle you will actually lose your health. So it is really crucial to listen to your body and integrate the feedback into your exercise intensity and frequency. When you work out it is wise to really push as hard as you possibly can a few times a week but you need to wisely gauge your body's tolerance to this stress.

Improve Your Heart Health and Your Insulin Sensitivity

High intensity interval exercises offers pretty astounding benefits to your heart and risk of chronic diseases, like diabetes. A Canadian research team gathered several groups of volunteers, including sedentary but generally healthy middle-aged men and women, and patients of a similar age who had been diagnosed with cardiovascular disease³. The participants were asked to undertake a program of cycling intervals as their exclusive form of exercise.

After several weeks on the program, both the unfit volunteers and the cardiac patients showed significant improvements in their health and fitness. Most remarkably, the cardiac patients showed "significant improvements" in both heart and blood vessel functioning. And, contrary to what popular belief might dictate, the intense exercises did not cause any heart problems for any of the cardiac patients.

The conventional widely held belief is that the short exposure of the exercise actually helps insulate your heart from the intensity!

Equally remarkable were the results of yet another study, in which unfit but otherwise healthy middle-aged adults were able to improve their insulin sensitivity and blood sugar regulation after just two weeks of interval training (three sessions per week)⁴. A follow-up study⁵ also found that interval training positively impacted insulin sensitivity. In fact, the study involved people with full-blown type 2 diabetes, and just ONE interval training session was able to improve blood sugar regulation for the next 24 hours! This truly is amazing, and while aerobic fitness is indeed important, improving and maintaining good insulin sensitivity is perhaps one of the most important aspects of optimal health.

A Simple to Follow Approach to Peak Fitness and Longevity

If you are using exercise equipment, I recommend using a recumbent bicycle or an elliptical machine for your high-intensity interval training, although you certainly can use a treadmill, or sprint anywhere outdoors. Just beware that if you sprint outside, you must be very careful about stretching prior to sprinting. Also, unless you are already an athlete, I would strongly advise against sprinting outdoors, as several people I know became injured doing it the first time that way. For a demonstration using an elliptical machine, please see the following video. Here are the core principles:

If you have a history of heart disease or any medical concern please get clearance from your health care professional to start this. Most people of average fitness will be able to do it though; it is only a matter of how much time it will take you to build up to the full 8 reps. By the end of your 30-second high-intensity period you will want to reach these markers:

• Warm up for three minutes
• Exercise as hard and fast as you can for 30 seconds. You should be gasping for breath and feel like you couldn't possibly go on another few seconds. It is better to use lower resistance and higher repetitions to increase your heart rate
• Recover for 90 seconds, still moving, but at slower pace and decreased resistance
• Repeat the high-intensity exercise and recovery 7 more times. (When you're first starting out, depending on your level of fitness, you may only be able to do two or three repetitions of the high-intensity intervals. As you get fitter, just keep adding repetitions until you're doing eight during your 20-minute session)
• Cool down for a few minutes afterward by cutting down your intensity by 50-80 percent
• It will be relatively hard to breathe and talk because you are in oxygen debt.
• You will start to sweat. Typically this occurs in the second or third repetition unless you have a thyroid issue and don't sweat much normally.
• Your body temperature will rise.
• Lactic acid increases and you will feel a muscle "burn."

The remarkable effectiveness of interval training makes logical sense when you consider that this type of exertion mimics how our ancestors lived. This is also how animals and young children behave naturally (long-duration exercise really isn't "natural"). By exercising in short bursts, followed by periods of recovery, you recreate exactly what your body needs for optimum health, and that includes the production of growth hormones, the burning of excess body fat, and improved cardiovascular health and stamina.

Remember to Add Variety to Your Exercise Program

In addition to doing high intensity interval exercises a couple of times a week, it's wise to alternate a wide variety of exercises in order to truly optimize your health. Without variety, your body will quickly adapt and the benefits will begin to plateau. As a general rule, as soon as an exercise becomes easy to complete, you need to increase the intensity and/or try another exercise to keep challenging your body. I recommend incorporating the following types of exercise into your program:

You need enough repetitions to exhaust your muscles. The weight should be heavy enough that this can be done in fewer than 12 repetitions, yet light enough to do a minimum of four repetitions. It is also important NOT to exercise the same muscle groups every day. They need at least two days of rest to recover, repair and rebuild.

Exercise programs like Pilates and yoga are also great for strengthening your core muscles, as are specific exercises you can learn from a personal trainer. In a related article, Pilates Platinum owner Healther Dorak shares three moves you can do at home or in the gym. To see a demonstration of each exercise, please check out the article posted on FitSugar.com⁶.

"Each of these three moves targets and challenges several different muscle groups at once so you get more bang for your buck," says Dorak. "Do this routine three times a week, and you'll start to strengthen and tone your abs, legs, glutes, and arms."

• Interval (Anaerobic) Training: This is when you alternate short bursts of high-intensity exercise with gentle recovery periods.
• Strength Training: You can actually "up" the intensity by slowing it down. For more information about using super slow weight training as a form of high-intensity interval exercise, please see my interview with Dr. Doug McGuff.
• Core Exercises: Your body has 29 core muscles located mostly in your back, abdomen and pelvis. This group of muscles provides the foundation for movement throughout your entire body, and strengthening them can help protect and support your back, make your spine and body less prone to injury and help you gain greater balance and stability.
• Stretching: My favorite type of stretching is active isolated stretches developed by Aaron Mattes. With Active Isolated Stretching, you hold each stretch for only two seconds, which works with your body's natural physiological makeup to improve circulation and increase the elasticity of muscle joints. This technique also allows your body to repair itself and prepare for daily activity. You can also use devices like the Power Plate to help you stretch.

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