Are we sure about this?

[Saturation]

True. In fact informed opinion seems to be swinging from genetics being the most influential factor to life style (fitness) being more important that genetic predisposition; at least for most people.

But that is a bit off the track for this thread. Here we are discussing the question: How fit does a person need to be to safely dive in a recreational setting; be that reeef crawling, wreck, cave, or whatever?

I submit that although there are some WAGs that in some cases may even be elevated to SWAGs we just don't know.

We do know.

The diving medicine guidelines are METS >= 13. If you cannot pass that in a formal evaluation, a diver will not pass the RSTC PE form. In the US, maintaining fitness however, is the diver's responsibility.

Although one can drop the level to about 10 at minimum, the risk of sudden death just rises exponentially.

As for musculoskeletal fitness, that's another issue, but its linked closely to METS, so if you can METS >= 13, chances are one's joints and spine are up to the task.

 

[Rick Inman]

I figure that I'll stop diving when I'm no longer able to gear up without having to rest up several times. Putting on a wetsuit and hauling gear (and cleaning it after the dive) are more physically challenging than most of my dives!

Ain't it the truth. My technical diving buddies are both guys in their prime - lower 30's, - and I'll be 50 this summer. Hauling multiple sets of doubles, stages, scooters, hauling them up and down hills and ramps, hauling yourself with all the gear on up the boat ladder at the end of the dive... you will soon see what kind of shape you're really in. I figure as long as I can keep up with my young punk buddies, I'm Ok.

I try to stay fit and at proper weight, and although 50 may be the new 40 or whatever, I am not 25 anymore. But I'm smarter about the use of my body, and it's amazing how many times after hiking up the beach in my doubles after a shore dive, I'm less winded than many of the newer, younger singles divers. It's funny, I feel like I understand my body and how to use it more efficiently and get more mileage out of it at middle age than I did as a youth. But the price for this physical wisdom is that I can't eat donuts and fast food and not exercise like I did when I was 20.

 

[ArcticDiver]

We do know.

The diving medicine guidelines are METS >= 13. ...

Yep, I am aware of that. My point is that at best that is a SWAG, not an empirically determined number. Certainly the assumptions that went into setting that number sound reasonable. But, they are just that, assumptions.

In fact, from observing divers in action over the past few years I suspect very few of them could reach that target. Yet, from DAN statistics serious injury and death is extremely rare. Hence, it is reasonable to make another assumption; that the guideline is not realistic as applied to the general diving population.

 

[Charlie99]

In fact, from observing divers in action over the past few years I suspect very few of them could reach that target. [ >13 METs ]

Trying get an intuitive feel for what 13 Mets corresponds to I wandered through webpages on things like the Bruce Protocol and it seemed like 13 Mets was a pretty high target.

I also found this article when trying to figure out the typical performance of various age groups: How 'Bout Them METs!

An individual's capacity is the highest MET number he or she can sustain for a few minutes, Earnest said. You can increase this capacity by getting more fit. A healthy 50-year-old man should have a capacity of at least 9.2 METs; a healthy 50-year-old woman should clock in at 8.2 METs or higher, according to a recent study on women's fitness in the New England Journal of Medicine. (Some other age-related targets: For men age 20, 13.5 METs; age 30, 11.4 METs; age 40, 10.3 METs. For women age 20, 12.1 METs; age 30, 10.8 METs; age 40, 9.5 METs.)

Too much to remember? Try this: The Centers for Disease Control and Prevention says that, for most people, activities burning three to six METs qualify as moderate intensity; those using more than six METs are vigorous.

In another webpage I found a conversion between treadmill incline + speed to METs. There's no way I can sustain 13 mets of activity, and I'm pretty healthy for a 59 year old. I find that walking on an inclined treadmill in around 3.0 - 3.3mph at 12% grade for 25 minutes is a pretty good workout and there is no way I could sustain the higher speeds and incline corresponding to 13 mets.

It appears that a "fit for diving" requirement of >13 mets is a pretty agressive standard. Then again, maybe I'm misunderstanding the meaning of

The diving medicine guidelines are METS >= 13. If you cannot pass that in a formal evaluation, a diver will not pass the RSTC PE form.

Comments from anybody that actually does "fitness for dive" medical clearances that include met testing??

 

[fisherdvm]

I don't know if 13 is very high. For my age, it is only about 13 minutes on the bruce protocol, which is only 1 minute at the maximum speed of 5 miles per hour, and 18 degree incline. Certainly, as you get older, it will be more difficult to sustain higher speed, not because of cardiovascular fitness - but because of arthritis, and other skeletal issue.

I know that my dive instructor simply snorkels and fins for over 1 hour 3 or 4 days a week. That probably can achieve a good mets value. But he likely can not do mets of 13, mainly because of his age.

I think the 13 mets is likely a guideline, and there must be other methods to substitute for handicaps.

 

[Saturation]

The purpose of a stress test is a maximum load will put "defective parts" into failure, in this case a critically blocked artery ... and to do this in a controlled setting. In electronics, we also call such evaluations a burn-in. Its not truly to determine one's physical ability to do dives but to find disease that is of concern. A negative test does not mean one has no disease, just that it won't be of concern at least for a year, because only critical blockages will show under marked stress.

How an exercise stress test relates to true sport activity, METS measured via a stress test is a peak transient performance capacity. A 'touring' or working METS is another issue, its like the difference in energy needs between a sprint, a running marathon or 20 mi march.

Is it a WAG or SWAG? METS 13 is not a wild a** guess but neither has it been analyzed with the same scrutiny as medical studies like cholesterol and heart disease. it likely can be realistically some notches lower, but as it stands its an RSTC standard.

In real recreational dives, a dictum is to exert yourself in-water minimally to reduce risk of nucleation, c02 retention, gas consumption, narcosis, DCS, etc., so the exercise capacity is really there to insure a diver's heart will not be an issue, enhance bubble mechanics and later, provide a reserve capacity in case of emergency. While the working METS for dives is likely in the 4-6 range, the need for a higher capacity can occur without warning, such as emergencies, and buoyancy alone puts a known but poorly quantified load on the heart, without any exertion on the diver's part. Further vascular patency will vary with temperature, and arteries that survived METS 13 in a comfortable stress lab can react differently if the diver is chilled. Add to it, a simple problem like angina will find no relief once it is initiated at depth, even with a diver at rest. Since diving is a heterogenous set of conditions, from calm flat seas and 200+' vis to 1 knot current in rolling seas, from being within drivable range to a major US Medical Center or the remoteness of Vanuatu, the fitness requirement for diving has no set limitations, and is thus set by default to maximal.

Yes, I've sent patients at risk for heart disease to stress tests, and asked specifically that they stick it out to a METS >= 13. Most make it through, the problem are those who don't.

The risk of recreational fatality hovers in the 1/10,000 divers, the risk of a driving fatality in US roads is similar 1/10,000 drivers but driving is a necessity in most US daily life, while diving isn't. Putting those numbers into perspective, ask yourselves do you know anyone killed in a car accident, personally, or a dive accident? Its really not that rare, as compared to asking yourselves if you know anyone who was murdered.

The theory of fitness is rather involved, but few texts touch on its needs as this book does:

SCUBA Diving Exercise and Fitness

 

[bleeb]

Not knowing much about METS, I did some digging around and came across the following document from the University of South Carolina's Prevention Research Center.

METS=12.5 skin diving, moderate
It also gives a value for SCUBA diving, but it seemed too vague about the conditions and didn't seem worth repeating.

METS=10.0 running 6 mph (10 min/mile, 6.5 min/km)
METS=12.5 running 7.5 mph (8 min/mile, 5 min/km)
METS=13.5 running 8 mph (7.5 min/mile, 4:40 min/km)
METS=15.0 running 9 mpg (6.5 min/mile, 4 min/km)
If this is measured in the same units, a METS of 13 sounds only moderately challenging for the average runner, and hopefully most people who are in decent shape (or at least decent enough to dive) could learn to run this with some training and practice IMHO.

METS=10.0 walking upstairs carry 50 to 74 lb load
METS=12.0 >74 lbs
For me, climbing onto a boat, that's less that an AL80, 7 mm farmer john and assorted gear.

USC Prevention Research Center :: PRC Reports and Tools

 

[ArcticDiver]

before we get too entrenched in our thought patterns let me give a go at saying it another way.

The fundamental problem with assigning any particular fitness number, like METS, to a diving fitness standard is that the assumptions upon which it is based are just that, assumptions. On the other hand certain job specific fitness standards are based on significant empirical study that directly affect job performance. The latter would certainly be an objective way of measuring someone's suitablity for the task. The former would not be.

It is one thing to say, for example, that based on experience a lifeguard needs to be able to swim a specified distance that relates to the area of responsibility in a time that would make a rescue effective. It is qute another to decide that a certain level of fitness is required to do a job and to measure it using a method that does not include performing the job/task. In real life the first situation is essentially what a divemaster candidate must do. The second is what the METS 13 does.

Of course, as stated previously, death or serious injury is so infrequent in diving and the events themselves are so poorly analyzed that it is hard to know what role physical fitness played in most of them.

Some of us advocate a more thorough analysis of incidents and accidents so we, the general public of divers, can know the facts and circumstances surrounding them. That would certainly move us beyond the My Expert's Assumptions are better than Your Expert's. But, it doesn't sem likely that will happen any time soon.

 

[ArcticDiver]

As I was doing my workout routine today I was thinking of this thread. I started with some weights, did an hour spin class with a master motivator as a leader and finished with some crunches, back extensions and standing barbell curls going into standing military presses.

What came to me is that not only do we not have a good description of how fit a person needs to be to dive; we don't even have a set of tests that comprehensively measure that fitness, whatever it may be.

Without a doubt METS is the best measure of cardiovascular fitness we have available. We can obtain similar data from aerobic sports. But, METS is standardized and better understood in the medical community.

But, cardiovascular is only one measure. I think we would all accept that muscle and skeletal strength are just as important as cardio.

Another pertinent fitness factor is psychological. How well does the person function when in the diving environment? We all know that our performance improved after some experience. But we got through those first dives either because we had no problems, or because we could handle the pressure of a problem. I know, as I'm sure y'all do too, people who just can't handle that stress.

I could go on. But,the point is that what we have been so vigorously discussing is but one factor in determining fitness to dive. Maybe what should happen is that someone comes up with an empirically based fitness standard that can be universally recognized and accepted.

 

[DocVikingo]

I don't know if 13 is very high. For my age, it is only about 13 minutes on the bruce protocol, which is only 1 minute at the maximum speed of 5 miles per hour, and 18 degree incline.

Hi fisherdvm,

Under the Standard Bruce Treadmill Test, achieving 13 mets involves walking at 4.2 mph at an incline of 16 degrees. Like the earlier stages, this one (Stage 4) is maintained for 3 min.

There is a modified version for use with elderly or very sedentary individuals where the third stage corresponds to the first stage of the Standard protocol, but I much doubt it would be applicable to you and in any event the numbers you provide still don't fit.

Are you referring to some other modification or technique?

Thanks,

DocVikingo