Training & Nutrition - Low blood pressure - dizziness?

I have lost over 40 lbs. since December 06, and have increased my fitness exponentially since then. I am riding on a regular basis with around 65 to 85 miles per week right now.
I have recently developed occasional periods of dizziness when I stand quickly or move my head quickly. these events are not too often, but when it happens while driving in the car, I get a little concerned. A co-worker suggested it was low-blood pressure. I have never had high or low blood pressure before, always spot on.
Anyhow, I was wondering if any of you out there have experienced this phenomena while getting back into shape and improving your cardiovascular system?

thanks on advance

My wife once in a great while has dizziness which has been diagnosed as from low blood pressure. It could also be a symptom of too low blood sugar not feeding your brain adequately. Based on your weight loss and exercise, that's what I would bet on. Need more quality carbs?

Al

It could also be hypovolemia (http://en.wikipedia.org/wiki/Hypovolemia).

It could also be hypovolemia (http://en.wikipedia.org/wiki/Hypovolemia).

Well, as far as I can tell, I have no blood losses (thank goodness)
So I will also tend to favor the "low blood sugar" diagnosis for now.

I just had a complete physical with an EKG about ten months ago, and even though I was 265lbs the doc said I was good to go. I have been cutting way back on carbs - but will probabaly include more good carbs now that I'm increasing my weekly mileage.

vasovagal syncope, do a google search

I am hypertensive and on multiple meds for it. I returned to cycling last April.
I learned pretty early on, after strenuous rides, that I needed to do adequate cooldown laps before dismounting or I would start to black out. I was fine as long as I kept riding, it was only when I stopped that I had the problem. Having my suspicions, I checked my BP immediately after a hard ride and found it to be about 70/40. Explains a lot to me. What I figured out was that a large amount of vasodialation occurs under strenuous exercise leading to a drop in my BP.

It's called orthostatic hypotension. Happens all the time. Blood goes to the tissues being exercised. Here's a link:
http://www.medicinenet.com/script/main/art.asp?articlekey=79327

Happens to me after an intense bout of low cadence work on the rollers, squats, leg sled, stuff like that.

However, it sounds like this happens to you too often. There have been several studies showing that strength training reduces the severity of orthostatic hypotension:
http://www.wwu.edu/depts/healthyliving/PE511info/BP/BP/exercise%20for%20hypotension.htm

This used to happen to be quite frequently when I was very fit. (20 years ago, unfortunately not now.) I was doing a large amount of endurance training and racing, and my resting heart rate was very low. Blood pressure was low as well, but not abnormally so. I would frequently get light-headed if I got out of bed too abruptly. Oddly, it would also sometimes happen when getting out of the pool after swimming laps, even though my heart rate and blood pressure would be way higher than when getting out of bed in the morning. This continued to happen for several years but eventually went away as I did less training and lost cardiovascular fitness.

Its probably nothing to worry about, but given that its happening to you when driving, and that you have been very aggressively losing weight, it would seem prudent to consult a doctor, no?

Well, as far as I can tell, I have no blood losses (thank goodness)
So I will also tend to favor the "low blood sugar" diagnosis for now.

I just had a complete physical with an EKG about ten months ago, and even though I was 265lbs the doc said I was good to go. I have been cutting way back on carbs - but will probabaly include more good carbs now that I'm increasing my weekly mileage.

Well, read this bit as well, and maybe the connection will be clearer:
http://en.wikipedia.org/wiki/Volume_status

[QUOTE=SaiKaiTai]I am hypertensive and on multiple meds for it. I returned to cycling last April.
I learned pretty early on, after strenuous rides, that I needed to do adequate cooldown laps before dismounting or I would start to black out. I was fine as long as I kept riding, it was only when I stopped that I had the problem. QUOTE]


I ran into the cooldown issue last August. This was my first summer cycling at a much higher energy level. That likely meant that I was more prone to over taxing my cooling system in the local high temp/humidity conditions.

I felt faint after a hard 2-hour hard. After this happened twice, I happened across an article that indicated that this can happen to perfectly fit/healthy individuals with out cooldowm. I added some cool-down pedaling and that solved it.

Different folks can react to stress differently. When I run into Glycogen depletion, I tend to get spots in my peripheral vision. That to is not unusual according to my optometrist.

Al

After a long hard ride, I always have that problem. If I drink a beer or two afterwards, I have to be careful to keep from passing out. And it's not uncommon in general with athletes having good cardiovascular development.

But you've dropped a lot of weight in a short time (and that is fantastic!). If you're close to a healthy weight, and especially if you're training, you want to slow the weight loss and try to match your caloric intake to your requirements in order to (re)build muscles and cardio fitness. As Al suggests, it may simply be post workout low blood sugar.

I have lost over 40 lbs. since December 06, and have increased my fitness exponentially since then. I am riding on a regular basis with around 65 to 85 miles per week right now.
I have recently developed occasional periods of dizziness when I stand quickly or move my head quickly. these events are not too often, but when it happens while driving in the car, I get a little concerned. A co-worker suggested it was low-blood pressure. I have never had high or low blood pressure before, always spot on.
Anyhow, I was wondering if any of you out there have experienced this phenomena while getting back into shape and improving your cardiovascular system?

thanks on advance

Having a bit of a "head rush" when you get up too quickly isn't that rare. But if it happens when you're just sitting there and moving your head, it might be something else. I'd talk to my doctor about it.