By Dr. Mercola
Modern fitness research offers many potent reminders that physical activity is one of the best "preventive drugs" for many common ailments, from psychiatric disorders to heart disease, diabetes, and cancer.1
For example, one meta-review2 of 305 randomized controlled trials comparing the effectiveness of exercise versus drug interventions on mortality outcomes found "no statistically detectable differences" between exercise and medications for prediabetes and heart disease!
One of the key health benefits of exercise is that it helps normalize your glucose, insulin, and leptin levels by optimizing insulin and leptin receptor sensitivity.
This is one of the most important factors for optimizing your overall health and preventing chronic disease, and may explain why exercise is such a potent preventive medicine.
However, as with other medications, there's the matter of dosage. Too little, and you won't get much benefit. Too much, and you could potentially do harm.
For example, extreme endurance cardio, such as marathon running, actually damages your heart and can negate the health benefits you'd otherwise reap from a regular fitness program.
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.
Finding the Goldilocks Zone...
As discussed in a recent New York Times article,3 there's a "Goldilocks zone" in which exercise creates the greatest benefit for health and longevity:
"Two new, impressively large-scale studies4,5 provide some clarity, suggesting that the ideal dose of exercise for a long life is a bit more than many of us currently believe we should get, but less than many of us might expect."
In the larger of the two studies,6 data was collected from six large health surveys involving an impressive 661,000 adults and 14 years' worth of death records. Exercise habits ranged from no exercise at all, to 10 times the recommended amount, or 25 hours per week and over. Among their findings:
- Those who did not exercise had the highest risk of premature death
- Those who exercised but did not meet current exercise recommendations of 150 minutes of moderate exercise per week lowered their risk of early death by 20 percent
- Those who met the guidelines of 150 minutes per week of moderate exercise lowered their risk of death by 31 percent during the 14 year study period, compared to those who did not exercise
- Tripling the recommended amount of exercise had the greatest benefit. Those who engaged in moderate exercise such as walking for 450 minutes per week (just over an hour a day), lowered their risk of premature death by 39 percent, compared to non-exercisers
- Those who exercised at 10 times above the recommended level only gained the same mortality risk reduction as those who met the guidelines of 150 minutes per week
The second study7 focused on intensity. Here, health survey data from more than 200,000 adults was pooled, and the exercise that each person engaged in was qualified according to intensity. As reported in the featured article:8
"[A]s in the other study, they found that meeting the exercise guidelines substantially reduced the risk of early death, even if someone's exercise was moderate, such as walking. But if someone engaged in even occasional vigorous exercise, he or she gained a small but not unimportant additional reduction in mortality.
Those who spent up to 30 percent of their weekly exercise time in vigorous activities were 9 percent less likely to die prematurely than people who exercised for the same amount of time but always moderately...
[T]hose who spent more than 30 percent of their exercise time in strenuous activities gained an extra 13 percent reduction in early mortality, compared with people who never broke much of a sweat." [Emphasis mine]
Everyone Can Benefit from Walking More Each Day
It's interesting to note that the greatest benefit, in terms of longevity, was reaped by those who primarily walked for an hour or so each day. Overwhelming amounts of research shows that sitting too much can take a massive toll on your health, and everyone would benefit from simply standing up and walking more each day.
Chronic sitting is the new smoking, actually raising your risk of lung cancer by over 50 percent. Importantly, it elevates your risk for an early death from poor health independently from your fitness and other lifestyle habits.
Personally, I believe that application of this truth has had one of the most profound impacts on my health. I used to sit more than 12 hours a day and had chronic back pain. Now, I sit less than one hour a day and my pain has disappeared, posture has improved, and I feel much better.
It's ok to sit some, and you don't have to go under an hour like I have, but ideally you'll want to limit your sitting to three hours or less, and aim for 7,000 to 10,000 steps a day, over and above your scheduled workout. A fitness tracker can be a helpful tool to monitor your progress and ensure you're hitting your mark.
If you've taken such advice to heart and are incorporating more walking into your day, consider switching up the pace at regular intervals, interspersing bouts of speed walking followed by more casual strolling.
In study after study we find that it is this intermittent high and low intensity that appears to produce the most significant results. So simply by exerting yourself intermittently when walking, you can dramatically increase the return of your effort without spending any extra time on it.
Intermittent High Intensity Is Key for Optimal Results
A growing body of clinical research maintains that the ideal fitness regimen is one that mimics the movements of our hunter-gatherer ancestors, which included short bursts of high-intensity activities, but not long-distance running such as is required to complete a marathon.
The idea behind "hunter-gatherer fitness" is to closely emulate the actions that ancient man took on a daily basis. This is what your body is hard-wired for, after all, and includes such attributes as:
- A variety of exercises performed regularly (weight training, cardio, stretching, etc.)
- Alternate difficult days with easier days
- Interval training sessions performed once or twice a week
- Weight training at least twice a week
- Ample time for rest after physical exertion
Part of what makes high-intensity interval training (HIIT) so beneficial for your body composition and general fitness and longevity is that it:
- Engages far more of your muscle tissue than conventional aerobic cardio exercise. You have three different types of muscle fibers: slow, fast, and super-fast. Only ONE of these muscles, the super-fast fibers, will impact your production of human growth hormone (HGH, also known as "the fitness hormone"), which is KEY for strength, health, and longevity, and HIIT is the only way to effectively engage these super-fast fibers.
- Produces anti-inflammatory myokines in your muscles, which very effectively reverses metabolic syndrome by increasing all of the following: insulin sensitivity, glucose utilization inside the muscle, liberation, and burning of fat from adipose cells. Myokines also act as chemical messengers that inhibit the release and the effect of the inflammatory cytokines produced by your body fat. They also significantly, via an inhibitory effect, reduce body fat irrespective of calorie intake!
If you're over the age of 30, especially if you lead an increasingly sedentary lifestyle, you've likely entered a phase known as somatopause (age-related growth hormone deficiency). As your HGH levels decrease, your levels of insulin-like growth factor-1 (IGF-1) also decrease. This is another important part of what drives your body's aging process.
Sample HIIT Demonstration
There are many ways to do high-intensity interval exercises. You can use a bicycle, an elliptical machine or treadmill, sprint outdoors, or up the intensity on your strength training routine by slowing it down (super-slow strength training). Just beware that if you sprint outside, you need to properly stretch prior to sprinting to avoid being sidelined by an injury.
Also, unless you are already an athlete, I would advise against sprinting outdoors, as several people I know became injured doing it the first time. For a demonstration using an elliptical machine, please see the video above. Here are the core principles:
- 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
Be mindful of your current fitness level and don't overdo it when you first start out. Also keep in mind that there's no "magical" speed here. It's entirely individual, based on your current level of fitness. Some may reach their anabolic threshold by walking at a quick pace, while others may need to perform a mad-dash to get the same effect.
Also remember that besides intensity, recovery is a key factor of high intensity workouts. An equation to keep in mind is that as intensity increases, frequency can be diminished. In fact, you need to allow your body to fully recuperate in between sessions, so it's NOT recommended to do high-intensity exercises more than three times a week. Both Phil Campbell and Dr. Doug McGuff have addressed this in previous interviews.
Balanced Variety Is the Key to Optimal Health and Longevity
Even if you're eating the best diet in the world, you still need to exercise effectively to reach your highest level of health. I've often equated exercise to a drug from the perspective that they both need to be taken at optimal dosage to reap the desired effect.
As for the optimal weekly time investment, remember that the greatest effect on longevity was found among those who engaged in 150-450 minutes of exercise per week, the bulk of which was moderate intensity activities such as walking. And those who included bouts of vigorous activity also got an extra boost in longevity, compared to those who kept to a one pace.
Ideally, you want to incorporate a variety of activities, including core-strengthening exercises, strength training, stretching, and high-intensity activities into your rotation. High-intensity interval training boosts human growth hormone (HGH) production, which is essential for optimal health, strength, vigor, and yes—longevity. That said, intermittent movement is equally (if not more) critical for maximizing the quality of your life. Chronic, undisrupted sitting—even if you maintain an optimum fitness program—has been found to be an independent risk factor for premature death.
In short, one of the keys to optimal health is to remain as active as you can, all day long. Whenever you have a chance to move and stretch your body in the course of going about your day, do so. That said, there's no doubt that an ideal fitness regimen requires a little more effort. Fortunately, you can accomplish the bulk of it through high intensity exercises, which require a minimal time investment—as little as 20 minutes, two to three times a week.