Determining Functional Swimming Threshold

Don Macdonald training in 58 f fresh water for the English Channel
with support team under watchful eye of Doug McConnell.

There are a number of training assessment methodoligies. Understanding, especially as we age, how to train effectively, efficiently, and safely is critical to a long life and positive outcome.

TrainingPeaks WKO+ automatically generates training stress scores (TSS) for bike rides uploaded from a power meter and for run workouts uploaded from a speed and distance device. Triathletes who use WKO+ and appreciate this feature often wish that the program could do the same for swim workouts. Unfortunately, the swimming equivalent of a bike power meter or run speed and distance device does not yet exist. However, you can calculate TSS for your swims manually using a method we’ll describe in this article.

Why not simply use the same calculation for swim TSS that is used for running, in which the metric of pace is also used to quantify the training load? Because water presents more resistance than air, so the physiological stress of swimming increases with increasing swim speed faster than the physiological stress of running increases with increasing running speed.

The simplest, if not the most accurate, way to account for this difference in calculating TSS scores is to weight the “intensity factor” of swim workouts differently than it is weighted for run workouts. Specifically, we suggest, it should be cubed as opposed to squared.

Determining Functional Swimming Threshold Speed

Training stress score calculations in running and cycling are scaled according to the individual athlete’s current functional threshold pace (running) and functional threshold power (cycling), which correspond roughly to the lactate threshold running pace or cycling power. The lactate threshold can only be determined through laboratory testing, while the functional threshold is determined through field tests that are known to yield roughly equivalent results.

Similarly, the functional swimming threshold pace is a stand-in for the laboratory-determined swimming lactate threshold pace. There are two approaches that are most appropriate for the determination of swimming FTP. The first is the straightforward timed effort, where you swim as far as possible in a given time (e.g. 30 or 60 minutes). So, if you swim for 30 minutes and cover 1000 meters, then you can use the value of 33.3 m/min. as your FTP. Since the actual FTP is closer to the one-hour effort, it might be more advisable to perform a 60-minute test, or to take the value obtained for 30 minutes, multiply by two and subtract 2.5 percent (as most trained swimmers swim roughly 2.5 percent slower in a 60-minute maximal effort than in a 30-minute maximal effort). So again, if you cover 1000 m in 30 minutes, your 60-minute FTP would be 1900 m/hr or 31.7 m/min. This may seem like a minor difference, but due to the resistive aspect of swimming, small differences can have a substantial impact.

If you are not inclined to perform such long, exhaustive efforts in the pool, you may alternatively perform a critical velocity (CV) test. This method consists of two test efforts at different distances (200 m and 400 m) separated by a complete rest. Because complete rest is required for the results of a CV test to be valid, it is best to perform the first all-out effort at the beginning of one workout (after warming up, of course) and the next at the beginning of another. Record the time required to complete each effort and simply plot the results on a graph as distance vs. time. The slope of that line is your critical speed. Alternatively, a simple equation yields the same result:

Critical speed = (Distance of longer test swim – distance of shorter test swim) divided by (Time of longer test swim – time of shorter test swim)

For example, suppose you swim your 200m test swim in 2:02 (2.04 minutes) and your 400m test swim in 4:21 (4.35 minutes). Your critical velocity, then, is (400m – 200m) ÷ (4.35 min. – 2.02 min.) = 86.6 meters/min.

The results of your critical speed determination should yield a result that is very close to a 60-minute test or a laboratory-determined lactate threshold pace. Either of these results can then be used as the FTP for determination of TSS and performance modeling.

Calculating swim TSS

Now that you know your swim FTP, you can easily calculate the TSS for any swim workout using the following procedure:

1. Measure total distance covered for the workout

2. Determine time to cover total distance (not including rest periods)

3. Express distance vs. time in m/min to obtain normalized swim speed (NSS), which is analogous to the normalized power and normalized graded pace in cycling and running, respectively

4. Divide NSS by FT to obtain IF

5. Swim TSS = (Intensity Factor cubed) x hours x 100

For example:

Once you have determined the swim TSS, you can manually input values in Training Peaks WKO+ and then use the program’s analysis features for swimming as you do with running and cycling. Let’s look at an example of a specific workout. First, let’s suppose that your swim FTP is 75 m/minute. Next, let’s suppose you complete the following workout (remember, rest periods are not counted):

Warm-up: 200 m @ 3:20, 30 sec. rest (3:20 total)

Drills: 4 x 50 m @ 1:00, 10-sec. rest (4:00 total)

Main set: 10 x 100 m @ 1:15, 20-sec. rest (12:30)

Cool-down: 200 m @ 3:20 (3:20 total)

Total workout distance: 1,600 m

Total workout time: 23:10 (or 0.386 hours)

The average pace for the complete workout is 1,600 meters divided by 23:10 (23.16 minutes or 0.386 hours) or 69 m/min. The intensity factor for the complete workout is the average pace (69 m/min.) divided by the athlete’s functional threshold pace (75 m/min.) or 0.92. To cube IF, multiply it by itself three times (So, in this example, 0.92 x 0.92 x 0.92). So the TSS for the workout is So the TSS for the workout is 0.778x 0.386 hours x 100 = 30.1.

There are some important limitations of our do-it-yourself method of swim TSS calculation to bear in mind. First of all, although this simplistic approach can be effective, it should be noted that by simply tracking distance and time swum, the effects of rest periods on the sustainable efforts are neglected, whereas in cycling and running they are not, because power meters and speed and distance devices capture coasting and non-movement as part of the workout.

Similarly, our rough-and-ready method of calculating swim TSS lacks the exponential weighting of higher intensities that is done automatically with pace and power in the digital calculation of normalized cycling power and normalized graded pace, and which is an important means of capturing the exponentially greater stress imposed by higher intensities. That being said, the cubed weighting of the IF counterbalances this limitation to a certain extent.

These calculations ignore the differences between different swim strokes and the rather substantial differences in efficiency that result from good or poor technique. Finally, the impact of flip turns and push-offs is essentially neglected using this approach.

Still, it’s a lot better than nothing, which is what triathletes interested in logging their swim workouts on WKO+ have had up to this point!

This article was reprinted from and co-written by Matt Fitzgerald and Stephen McGregor, PhD. 

Diana Nyad - Never Giving Up

Never Ever Give Up

My advice for living your healthiest, most fulfilling life—even if you’re not swimming across 110 miles of treacherous open ocean

By Diana Nyad ON LABOR DAY, 2013, I WALKED out of the sea onto Smathers Beach in Key West, becoming the first person ever to swim all the way across the Florida Straits from Cuba without a shark cage. It was a journey of 110.86 miles, and it took me 52 hours, 54 minutes. I was 64 years old at the time. Walking onto that Florida shore from Cuba didn’t become a reality until my fiſth try. I failed four times, and each of those attempts was public and each was crushing. I had put in hundreds of grueling, lonely training hours. A team of 44 people had sacrificed a great deal in the name of adventure, friendship and history. In the end, it was a 35-year saga of discovery, life lessons and grand experiences on an epic journey. Envision your dream and don’t give up until you get there, or at least get so close that your own effort inspires you.

The reason I was able to do something that many younger athletes had attempted and failed—myself included, back when I tried for the first time at age 28—is that I don’t believe in imposed limitations. Nobody knows the full power of the human spirit. If you are willing to accept the statistical parameters for your age, your gender, your economic situation, your whatever, you are flat-out saying you’re not interested in soaring toward your potential.

But we need to get real. The universe at times dishes out circumstances that even the toughest among us have to accept and come to terms with. My good friend, at the young age of 32, fought cancer of the worst kind with courage and not a drop of self-pity. But when the cancer in the end would not submit, my brave friend had to somehow find the grace to say good-bye to her children. We sometimes are dealt a tough road of physical and other kinds of disabilities. That’s when we still fight labels and yet somehow find elegance in determining what we can and can’t ultimately do.
Dreaming, reaching for stars and personal fulfillment are what drive the human spirit. I don’t wake up in the morning a middle-aged woman, a child of sexual abuse, a human rights activist, even though I am all of those things. I wake up a citizen of the world who refuses to let this cherished life slip quietly by. Don’t tell me I can’t touch the stars, because I just may get there one day. And on my way I’ll be tapping down into the deep well of all I can be.

Don’t Fear Failure ...

The debate about the journey versus the destination has raged for all time. Is the journey a worthy road to travel? What if you never touch that dream star of yours? I may have tried dozens of times more and never successfully completed the Cuba Swim, but I had come to peace with feeling that the journey itself was noble and worth taking, even if I never reached the destination.

During that last year of training in 2013, I kept on my desk that famous Teddy Roosevelt quote about not wanting to be a timid soul. To paraphrase, Roosevelt says he would rather be the guy in the ring who gets bloody and dirty and falls and fails over and over again. Far better, he says, to be bold and fail than to be a timid soul who is afraid and never tries at all.

Dazed when I stumbled onto that beach aſter more than two days of nonstop swimming, the first words I uttered through swollen lips were: “Never ever give up.”
I was living proof that to be fierce in your convictions, to refuse to give up on your dreams, allows you to stand tall, with no regrets that you have not lived out everything in your being.

There were thousands of screaming people on that beach to greet me. They weren’t swimming fans or even sports fans. They were people just like you and me, who fully understand and thirst to live inspired lives, who grasp that perseverance is the key to all success and fulfillment.

... And Never Let Age Define You

I truly believe that the key to well-being, aſter physical health and vitality, of course, is the drive to summon your spirit for something that moves you. Don’t let anybody else’s limitations define you. Envision your dream and don’t give up until you get there, or at least get so close that your own effort inspires you.
By the way, the second thing I said on that beach that day was: “You’re never too old to chase your dreams.”

Today, at 65, I am undoubtedly at the center of the prime of my life. As an athlete, a world-class athlete at that, I am stronger, fitter, more focused, more capable today than I was when setting records for such endurance marks as the fastest to swim around Manhattan Island at the age of 25, 40 long (or short) years ago.

Perhaps we can all of us agree that we mature and evolve for the better in all kinds of ways as we age. We have more perspective; the clock ticking exponentially faster year by year makes us want to grab on to our precious days, one by one. Our sense of appreciation for life and this beautiful blue jewel Planet Earth heightens. So it’s easy to understand an emotional and psychological prime at 65—for athletes and nonathletes alike.

Make this the prime of your life, whatever age you are, whatever life circumstances you find yourself in. It’s a one-way street we’re all traveling, each and every one of us. What a shame not to take this one walkthrough of ours with great gusto. It’s up to each of us to find a way toward whatever shore looms in our dreams.

Widely known as one of the world’s greatest endurance athletes, Diana Nyad inspired millions at 64 with the record-breaking swim from Cuba to Florida described in this essay. Previous feats include circling Manhattan and swimming 102 miles from the Bahamas to Florida.
Her next challenge? Getting a million people to join her planned journey across America—called The Walk—to draw attention to obesity and related illnesses and to help create social change. Her latest book, a memoir called Find a Way: The Diana Nyad Story: One Wild and Precious Life, will be published this fall.

In February she launched a one-woman show, Onward!, in Key West. Diana will tour her stage show around the country and, as we have come to expect, has ambitions to hit the big time—Broadway. For more on Diana, visit diananyad.com.

Exert from Merril Lynch Article

A Navy SEAL Explains 8 Secrets to Grit and Resilience

Getting Across

Outtakes from Article by Erin Barker

In this series we are breaking apart Erin Baker's article on why Navy Seals are so tough (Resilient) and what the everyday open water marathon swimmer can learn. 

Purpose And Meaning

To say SEAL training is hard is a massive understatement. 

The initial vetting phase (“BUD/S”) is specifically designed to weed people out who aren’t serious.

How do you get serious? Grit often comes from a place of deep purpose and personal meaning. Here’s James:

"At BUD/S you have to know what you’re getting yourself into and what you’re there to do.I still mentor a lot of guys who are interested in trying out for BUD/S and they always ask, “What do I need to do to make my push ups better?” or “Can you teach me the proper swim technique?” My first question is always, “Why do you want to be a SEAL? What is it about being a SEAL that appeals to you?”

The research backs James up. Without a good reason to keep pushing, we’ll quit. Studies of “central governor theory” show our brains always give in long before our body does.

“…Overall, it seems that exercise performance is ultimately limited by perception of effort rather than cardiorespiratory and musculoenergetic factors.”

But this isn’t just true for athletics, it also holds for careers. In a study of West Point alums, those that had intrinsic goals (“I want to serve my country. I want to test my abilities.”) outperformed those that had extrinsic goals (“I want to rise in the ranks and become an officer because that’s a really powerful position and it’s prestigious.”)

So purpose matters. But what’s the attitude that keeps you going in the moment? It’s actually a bit less serious.

If your just trying it to see if you will get across, you will more than likely fail.

Open Water Swimming - Once bitten, twice shy: our exaggerated fear of shark attacks

Something humor to think about as you wade into the calm, lovely morning swim . . .

Ok, Now that your adrenaline is pumping, here are the facts...

With open water swimming and beach season in full swing, the question inevitably arises: what are the chances of getting attacked by a shark? In a phrase: extraordinarily low – though not nonexistent. It is higher in certain parts of the US (Florida tops the list) than in others, and in some places (off Cape Cod) legendary great whites are making a comeback that can be frightening to beach goers. But is it really worth worrying about a shark strike or considering forgoing an ocean swim as an act of self-preservation?

Let's consider the numbers, courtesy of the International Shark Attack File at the Florida Museum of Natural History. Last year, 80 unprovoked shark strikes took place worldwide: seven resulted in deaths, including one in California. Fifty-three strikes took place in US waters, nearly half of them off Florida.

According to the file's analysis of data from 2000, beach goers faced a one in 2m chance of dying from drowning and other causes based on visits to east and west coast beaches. By contrast, they faced a one in 11.5m chance of being attacked by a shark, and less than a one in 264m chance of dying from a shark bite, since just one person died that year in US waters from an attack.

Put another way, more Americans were killed by collapsing sinkholes (16) than sharks (11) between 1990 and 2006, and more by tornadoes (125) than sharks (6) in Florida between 1985 and 2010. (And for all youSharknado fans, those were shark-free tornadoes.)

"Tides and currents kill more people [at the beach] than sharks that kill people," said Gregory Skomal, a shark biologist with the Massachusetts Division of Marine Fisheries.

But in some parts of the US, the number of shark spotting's has risen in recent years. Last year, there were more than 20 confirmed shark sightings at Cape Cod beaches, in areas including its outer beaches and off the mainland, and a 50-year-old man was bitten by a shark that scientists believe was a great white. (The swimmer, a Colorado native, was scarred but survived with limbs intact.)

This summer, eight great whites already have been spotted off various Cape Cod beaches, though some of the sightings may involve the same shark. The National Park Service just issued precautionary guidelines for Cape Cod swimmers.

Skomal has been tracking great whites off Cape Cod for years: he and his colleagues tagged five in 2009 and 17 in 2012. The probable reason for the increase is a resurgence in the seal population, which has been recovering over the past four decades since enactment of the Marine Mammal Protection Act, which outlawed a kind of hunting that caused the seals' precipitous decline. The National Oceanic and Atmospheric Administration estimates that the seal population in the western north Atlantic has increased by tens of thousands over the past few decades.

"I fully anticipate that the white sharks will continue to take advantage of this resource," Skomal said, noting that half of the sharks tagged in 2011 came back to the areas where they were tagged the following year. (Researchers use a few different tags, including acoustic ones that rely on radio transmitters and satellite tags.)"Everything is clicking for [the sharks] and the cafe is open for them. They will continue to take advantage of that."

A spate of shark strikes in 2001 that claimed the lives of swimmers – including two in the mid-Atlantic, 10-year-old David Peltier off Virginia Beach and 28-year-old Sergei Zaloukaev off Cape Hatteras, North Carolina – earned the season the nickname "Summer of the Shark". Zaloukaev was the last person to die from a shark bite in the mid-Atlantic. (His girlfriend was bitten also but survived.)

Still, there have been nonlethal events. Last month, 63-year-old surf instructor Barbara Corey was bitten off Holden Beach in Brunswick County, North Carolina, the first mid-Atlantic shark strike this year. Last year there were two, both in North Carolina, where six-year-old Brooklyn Daniel was struck off Brunswick and 33-year-old Megan Konkler was bitten off Nags Head Beach.

Florida's Brevard and Volusia counties, including tourist hot spots such as New Smyrna Beach, routinely lead the US in the annual number of shark strikes because they have a a huge number of surfers and swimmers and are in the migration routes of black tip and sandbarsharks. Together they made up 15 of the 53 recorded US attacks last year, though most of these tend to be minor scrapes since the species there are less dangerous than those found in other areas.

Commonsense precautions – avoiding areas where seals congregate, staying close to shore and staying out of the water around dawn and dusk, when sharks tend to be feeding and water visibility is low – are the best ways to avoid coming into a contact with a shark, experts say.

The shark species that pose the greatest risks to humans are great white, tiger, bull and oceanic whitetip sharks. So the regions of the world where some of these sharks swim – including Australia, South Africa and California, where great whites regularly migrate – tend to have more fatalities. Of the seven fatalities last year, according to the International Shark Attack File, three were off South Africa, two off Australia, one off California and one off the French island of Réunion in the Indian Ocean.

Despite its small size, Réunion has emerged as one of the world's deadliest shark sites: a 15-year-old was killed last month off a beach where swimming was prohibited, the second Réunion death this year and the fifth since 2011. Scientists do not know why this number is so high, but George Burgess, director of the International Shark Attack File, said he suspects that human factors are playing a role. Island residents have cut back on shark fishing because of concerns over the toxins in shark meat; Burgess said an increase in global tourism means more people who are not familiar with the island are visiting and swimming there. "Now you've got a great rush of people in the water who don't know the area, and don't know the risks," he said.

Christopher Neff, a doctoral candidate at the University of Sydney who researches the human-shark relationship, said that humans are becoming more open to protecting sharks in the open ocean even as they're growing more hostile to those near shore. In March, theConvention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) agreed to impose new rules on the trade inhammerhead, oceanic white tip and porbeagle sharks under which countries would have to prove their catch was sustainable before exporting it.

In December, French Polynesia and the Cook Islands joined together to create the world's largest shark sanctuary, emulating small island nations such as Palau and the Maldives in banning all shark fishing in their waters.

But both western Australia and Réunion have authorised shark hunts in the wake of deadly strikes there. Neff noted that researchers have become better at tracking sharks' swimming patterns with the use of satellite and radio tagging, but sharing this sort of information "can arouse public anxiety", and it can't prevent some of the inevitable human-shark interactions that arise.

"Anywhere we have a beach, we likely have sharks," he said. "The difference is that until now, we didn't know it."

This article appeared in Guardian Weekly, which incorporates material from the Washington Post

The Fountain of Youth may just be in a Pool or Lake

Swimming in the fountain of youth 

It has been my experience, observing my teammates, that they are generally more positive people
and have a higher success to overcome health challenges than others whom do not work out. 

The fountain of youth might just be in a lap pool near you, according to research at Indiana University Bloomington's Counsilman Center for the Science of Swimming, which is examining the effects of long-term participation in vigorous activity on "optimal aging."

"Swimming in particular provides an emotional foundation to your physical health rarely found elsewhere", Don Macdonald of One Stroke At A Time.

The researchers are adding a new twist to aging research by studying a very active population. Recent studies, says Counsilman Center Director Joel Stager, often are drawn from a diseased or declining population, casting them as the 'general' population.

"Are Masters Swimmers unique, or are we what 'normal' people should look like?" Stager recently told USMS Swimmer, the official magazine of United States Masters Swimming.

The IUB researchers conducted a battery of tests on elite swimmers -- United States Masters Swimmers competing in the U.S. championships in 2004 and in the FINA world championships at Stanford in 2006. They measured age markers, whose physiological functional capacity typically decline by 0.5 percent to 1 percent per year beginning around the age of 35, and compared their findings with similar data collected on the general population. From their 2004 data, they found that regular and fairly intensive swimming substantially delayed the decline of such age markers as blood pressure, muscle mass, blood chemistry and pulmonary function.

Photo by: Chris Meyer

Joel Stager is a professor in the Department of Kinesiology in the School of Health, Physical Education, and Recreation. He also directs the Counsilman Center for the Science of Swimming.

Print-Quality Photo

"We're starting to find out that a lot of the decline is probably related to a decline in activity rather than aging per se," said Stager, a professor in IUB's Department of Kinesiology. "The hypothesis is that activity preserves physiological function."

The researchers found that by regularly swimming 3,500 to 5,000 yards (roughly 2 to 3 miles) three to five times a week, the USMS swimmers examined in 2004 postponed the aging process, not only for years but for decades. They found that many of the swimmers delayed this natural decline until the age of 70. Stager, who also competed at the FINA Masters World Championships this summer, is an avid swimmer himself, swimming roughly 3,000 yards per day five times a week. For recreational swimmers, any amount of swimming is beneficial, he said, particularly for the least active. A workout should depend on goals, such as preparing for competition, improving fitness or seeking health and well-being benefits.

"The health and well-being benefits start with a minimal amount of swimming," Stager said. "If you want the fitness effect, you'll need to look at getting your heart rate up and boosting the intensity."

Stager said most of the male and female swimmers examined in spring 2004 reported swimming 3,500 to 5,000 yards five days a week. He received a grant from USMS to get a better grasp of how much swimmers actually swim, using accelerometers to measure how often, how far and how intensely they swim. He received another USMS grant to focus his research on the relationship between swimming, aging and muscle mass and function. The loss of muscle mass is a big concern among the aging, he said, because of its effect on range of motion and quality of life.

What would you pay to keep from getting sick as you get older? How about a daily walk or other exercise? A new study suggests that’s exactly the right investment. In the study, people who were the most fit at midlife lived longer and spent less time being sick than middle-aged folks who weren’t fit.

I am actually a better swimmer today than when I was 20, says Don, now 50.
I find the mental ability to overcome barriers can easily let me keep swimming further.
In recent years Don has trained millions of yards, most in cold open water below 70f with no wetsuit.

Probably the most difficult aspect of training as we get older is cross training to balance fitness and muscle response to prevent injury.

  

There are many benefits to staying physically active and exercising daily. Exercise

• strengthens the heart and lungs
• makes blood vessels more flexible and responsive, improving circulation
• controls blood pressure and cholesterol
• helps muscles burn sugar
• reduces stress
• decreases the risk of diabetes, heart disease, some cancers, and other chronic conditions
• preserves memory and prolongs life

Another important effect of exercise, one that doesn’t get enough attention, is that it improves fitness. Fitness is a measure of how well your heart, blood vessels, blood, and lungs work together to supply muscles with oxygen during sustained exercise. It also estimates how efficiently the muscles use the oxygen. Fitness also reflects your exercise capacity.

The most accurate fitness gauge requires complicated machinery and sensors to measure the maximum oxygen consumed during exercise. This is called VO2max. It can also be done using the kind of treadmill test that cardiologists commonly use to check for heart disease.

Fitness translates to better health later on

To explore the effect of fitness on health status in old age, researchers with the Cooper Institute in Dallas looked at information that had been gathered from more than 18,600 men and women who were part of another long-term health study. When the study began, their median age was 49. Fitness levels were measured using a type of treadmill test. Once a volunteer reached age 65, the researchers tracked his or her health with Medicare claims information.

Those who were the most fit at midlife were less likely over the course of the 26-year study to have died of coronary artery disease, Alzheimer’s, heart failure, diabetes and other chronic conditions, the researchers reported in Archives of Internal Medicine. Just over 2,400 people died during the study. In the last five years of their lives, the people who had been most fit at midlife spent about 50% less time with four or more chronic diseases than the least fit group and 34% more time with no or one chronic disease.

Find your fitness

How do you improve your fitness? Increase the amount and the intensity of exercise over time.

Exercise capacity is usually measured in metabolic equivalents (METs). One MET is the amount of oxygen used when sitting still or sleeping. Nonathletic, healthy, middle-aged men and women have peak exercise capacities in the range of 8 to 10 METs. Marathon runners can have values as high as 18 to 24.

But you don’t need an expensive exercise stress test to determine your fitness. Many fitness centers have exercise machines that show METs. Some home treadmills and elliptical trainers also show METs.

If you don’t have access to such a machine, or don’t like exercising on one, you can measure your current fitness with a simple walking test. All it takes is a one-mile track or level terrain that you know is one mile long. You’ll also need a stopwatch or watch with a second hand, paper, and a pen or pencil.

First, get yourself warmed up by walking briskly for a few minutes. Record the time and start walking as fast as you can. Push yourself, but don’t overdo it. When you cross the one-mile mark, record the time again. Calculate how many minutes it took to finish the mile.

	Time in minutes to walk one mile
Fitness level	50-year-old woman	50-year-old man
Excellent	under 14:42	under 13:24
Good	14:42 to 15:36	13:24 to 14:24
Average	15:37 to 17:00	14:25 to 15:12
Fair	17:01 to 18:06	15:13 to 16:30
Poor	more than 18:06	more than 16:30

Don’t be concerned about how low your METs are now or how slow you walked. What’s important is to improve them. You can do this with regular exercise that challenges your body. That means working hard enough to speed up your heartbeat and breathing.

The intensity of exercise and the amount of time spent exercising that are needed to improve fitness differ from person to person. The goal is to increase your METs or decrease the number of minutes it takes you walk one mile. Don’t rush it. Improving fitness starts within weeks but will continue for months.

Reprinted from: 

Howard LeWine, M.D., Chief Medical Editor
Internet Publishing, Harvard Health Publications

Dave Barra Talks About His 2010 Marathon Swims, This is the Reality