Do you mind me asking a couple questions? If not, do you have any related diagnoses? Hypertension?

Generally, lower sodium is going to impact your body's ability to retain blood volume. That is, hydration. Sodium consumption is necessary during longer/harder efforts to retain fluid volume in your blood, which is critical to maintain stroke volume for your heart. If your stroke volume goes down due to dehydration, heart rate goes up, for the same amount of physical work. You become less efficient metabolically, and have a lower rate of work at which fatigue will onset.

In short workouts, this is minimally important.

Anything over 2 hours and it gets more important, quickly.

On days you sweat heavily for >3 hours, you're likely to be losing >2000mg sodium in sweat a lone so a catch-all recommendation of "2000mg/day" is usually misplaced unless there is an existing diagnosis.

Disclaimer: I'm not an MD. I'm not well versed in all medical diagnoses, though I'm usually somewhat familiar. Please don't take any advice I give without chatting with your physician.

PS. Common symptoms of low-sodium consumption and endurance training:

1. Thirst
2. Peeing lots
3. Headaches
4. Faintness due to low BP, because your body won't retain the water in the blood stream enough to keep BP up.

If you plan to be sweating heavily for >4 hours I highly recommend talking this through with your doc and seeing if they'll allow for higher sodium consumption. Hyponatremia isn't something to mess with.

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Why? Unless you have congestive heart failure in which case you wouldn't be training at all there is no benefit. A moderate sodium diet 4-5 grams a day is likely as healthy as a low sodium diet and doesn't involve a high amount of effort that is better directed at other things.

You might get a 5 mmHg reduction in bp going low sodium which isn't much. You probably have to get something like 500 men to do this for ten years to prevent one stroke or heart attack. There are so many better ways of maintaining your health. We have been focusing on the wrong white crystal. High sugar intake way more damaging. This was something that was recommended a lot 20 years ago in preventative medicine not much now.

A Mediterranean type diet is way more beneficial.

https://pubmed.ncbi.nlm.nih.gov/33011774/

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They constantly try to escape from the darkness outside and within
Dreaming of systems so perfect that no one will need to be good T.S. Eliot

Just be aware that most endurance athletes need more sodium, not less. If you doc is treating you like a normal couch potato client, then maybe time to fill him in on what you do. Is there some particular metric gone awry that lead him to recommend this for you?

the heart healthy diet of low sodium...... japanese people eat 2x sodium daily as americans yet have 2x less heart problems

Yes, I was recently diagnosed with heart failure. I can still do cardio training but no more heavy lifting for me. Also, no more long course triathlon, but I can do short course.

I'm not sure what heart failure means, at least in your context. My failure was 3rd degree heart block. Others have heart attacks, some have A fib, others different bad arrhythmias. Which is your failure? How is it salt related if the doc told you??

Also not an MD here, but consider talking to your doctor about improving Kalium to Sodium ratio, rather than arbitrarily reducing Sodium.

Why am I not surprised you'd mix causation and correlation?

A lot more people drown when ice cream consumption increases. Obviously ice cream causes drowning, right?

Given the number of variables that affect longevity, the longest living people do not need a perfect track record. Especially when you compare them to people living the typical American lifestyle.

Heart failure is a loss of pumping efficiency of the heart. It's structural failing of the heart muscle, not electrical or blood supply related.

You and I can easily find the studies of what I stated, .. but let's see tours. People blame the sodium intake for heart disease when it's clearly the blocked arteries, causing that amount of sodium to be high, reducing sodium doesn't fix the original problem

That's not how any of that works.

Regardless, given that the OP is diagnosed with heart failure, that's not even related. As noted above heart failure is a pumping problem, and is impacted by excess blood volume. More sodium = more blood volume.

Presumably the doctor is controlling blood volume (via reduced sodium) to limit the heart muscle effects.

Last year I cut my salt intake quite dramatically and found in the first month I was getting leg cramps at night (never happened before) and cramps in all my toes and arch of foot when swimming. I found that there are two hormones that control how the body handles salt intake, and it takes one of them two weeks to adjust to a change in salt intake and the other hormone takes a month to adjust. This made sense to me as I have continued with a lower salt intake and not had any cramp problems after the first month.

You may find this study helpful (I am not a medical person by the way): https://www.ncbi.nlm.nih.gov/...articles/PMC8955583/