Heart Attack

[Dave Zimmerly]

In reading this article on why we have to urinate so often when we dive (Life at the Extremes), the author states "When you are standing upright on the seashore, there is a pressure gradient down your body due to the force of gravity, which causes the blood to pool in your legs. If you now immerse yourself in the sea up to your neck, this effect is counteracted by the external pressure of the water so that about half a litre of blood shifts upwards from the legs to the chest, distending the great veins and the right atrium of the heart and increasing your cardiac output. One consequence of stretching the atrial wall is that it alters the level of two hormones that influence water uptake by the kidney, and thereby stimulates urine production."

My question is, would this be a factor in increasing ones risk of a heart attack?

Regards,
Dave (aka "Squirt"

 

[headsqueeze]

The author might be referring to the body's fluid regulation 'reflex' involving naturetic hormones. It is a simplified and narrow view of why the human body increases urine output while other diving mammals decrease urine output while diving. The human body can dive, but not to the finesse of diving mammals. Some of our reflexes help us dive and some hinder our diving - like increase urine production.

Clear as mud - sorry.

The science discussed in the article you cite is overemphasizing a minor but interesting human body change during an increase in vascular volume. The concept was discovered on land with patient's suffering from congestive heart failure (an abnormal stressed and strained heart muscle) and not in the water w/ healthy divers.

The cardiovascular stress endured while suiting up for diving and swimming is a more important risk for heart attack. Anyone who can exercise 25% more than their diving exertion will tolerate the tiny increase of cardiac output (possibly) caused by an increase in vascular volume shifting during a dive.

 

[Dave Zimmerly]

Headsqueeze,

Thank you for your informative post.

Regards,
Dave (aka "Squirt")

 

[Cacia]

Anyone who can exercise 25% more than their diving exertion

I wonder how many people don't ever do that?
realistically

 

[spectrum]

I wonder how many people don't ever do that?
realistically

Bringing in the groceries seems like more work than diving.......

 

[TSandM]

I don't know -- I rarely carry 100 lbs worth of groceries, especially up hill . . .

 

[Cacia]

I noticed a couple years ago that I was working harder, as in my heart rate was getting higher diving than I was doing in the course of my normal week. -current, big seas, just trying to round divers up, etc. That is when I started cycling because the other stuff, I was doing was not really conditioning my CV system. I have had to work towards being in the true target zone for 45-hr.and feeling comfortable "good". I know I thought I was an active person, but before I got the HR monitor, I don't think I was in as good of shape as I thought I was.
I'm really noticing a difference now.

Bringing in the groceries seems like more work than diving.......

I think most people agree with you, sometimes I feel I'm on another planet.