Tasting Blood During Hard Cardio?

I stole a routine from Peter Attia I execute once a week. It's essentially his "Zone 5" workout. It consists of 4 minutes of high intensity cardio followed by a 4 minute rest. Repeat this 4 - 6 times. I use a bike but you can modify. Doesn't sound like much and if you add up the working units its only 20 minutes of exercise. All I can say is try it...And give it 110%. test

I have done it once a week for the past 3 weeks. It's brutal. And after round 1, not only do I feel lethargic with an ache throughout my body, but I have strange metallic taste in my mouth. After the first week, I thought it strange. After the second week, coincidence. And this morning...well I need to know what the hell is in my mouth?

Digging into this, it turns out I am not alone. This has been reported by several athletes, or otherwise, involved in intense cardio workouts. Some of the more lame theories include:

1. Indigestion/ heartburn - I don't think so. I eat before 8pm and I am at the gym at 5am. I have no food in my stomach when I hit the bike.

2. Pregnancy - We live in strange days....But no...

3. Dementia - possible as I am almost 50.

4. Poor oral hygiene -No, I am OCD about brushing and I carry dental floss with me everywhere as I CANNOT stand anything stuck in my teeth.

In addition to this strange taste just after hard cardio I also have a dry cough for a few hours after pushing it....

So, after continuing to research I found the answer:

Pulmonary Edema.

Sounds scary and life threatening. Pulmonary edema is caused from things like high altitude, heart problems, high blood pressure, kidney disease, drug overdose, clotting or poison.....

So what is happening? Well, the lung alveoli have incredibly high surface area and are engineered to maximize diffusion of oxygen across a membrane around 1 micron thick.

With the increase in hyrostatic pressure due to intense physical activity, it's possible and likely that in addition to oxygen migration from lung to capillaries, you may also leak some blood from alveolus to airway. This trace migration is not life threatening. However, with your rapid respiration during bouts of heavy breathing, your nasal passages and tongue are likely to sense the iron from hemoglobin leaked out. Slight Pulmonary edema.

And there you are, a metallic taste generated temporarily while hitting a killer zone 5 workout.

Mine is worse in the first 2 rounds and then dissipates, however I do have a dry cough the rest of the day. To me it feels like my lungs are sore just like sore muscles from lifting.

It is a little strange but from a physics standpoint, it makes perfect sense. I am hoping with time, I acclimate to this workout and it not so stressful on my chest. After all the whole goal is to improve my cardio and my VO2max.

So if this happening to you too, don't worry about it.

And get after it!