Here's the scenario:

Most days of the week, I get up with just enough time to get my stuff together and get dressed for the gym, get a ride there, and hop on the treadmill for empty stomach cardio. I warm up for 5 minutes, aim for 140 BPM in between, and cool down for 5 minutes. Every single time, the speed and incline, as well as the acceleration/deceleration of both throughout the workout, are generally the same aside from the occasional permanent boost due to improved fitness overall. My cardio typically lasted an hour, but I've decided to cut it down to 45 minutes recently, and yesterday I threw in an extra 45 minute session later in the day, after some light weight training (I'm trying to break a plateau, and cheat days haven't worked, so I'm just seeing what working harder does this time).

Anyway, this morning was weird. I did my cardio as normal, but no matter how hard I tried, my heart rate just wanted to hover at 130 BPM. I had to increase my speed to 3.2 and my incline to 7.0 just to achieve that by about 25 minutes in, when normally 2.8/6.0 gets it up to 140 BPM easily and I only have to increase the speed to 3.0 over the course of my workout to keep it there. Even when I was cooling down, my finishing heart rate was 10 beats lower than it normally is by the time I step off the machine.

At first I thought it was a glitch of the heart rate monitor on the machine (yes, I use it, but I know its limitations. I use it to get a rough figure before I decide to pause my workout and take my heart rate manually), but I took my heart rate manually at two separate times during my workout while trying to reach my THR, and once as soon as I finished, and the results were consistant with the machine.

Normally when I see signs of a lowered heart rate, I think it's a good thing, but in this case I had developed a killer headache and felt much more lethargic than usual, and I really wasn't feeling comfortable with the incline and the speed or how overheated I felt despite the lower heart rate. What could be causing this? What course of action should I take? Should I go see a doctor?

First of all - if you ever have a feeling like you should see a Dr, don't ask for advice. Do it. No advice can ever take the place of your Dr checking you out.

Exercise headaches are actually a common phenomenon, however, if you have no pattern of this - it could be many things. Anything from a virus comming on (head cold?) to just having a bad workout. If it is a severe headache - without a doubt get thyself to a Dr.

As for your heart rate. While we all have our standards and norms, we are an ever evolving machine. Things change - even moment to moment. It could be that your system was just operating at a higher level today and it was time for you to kick it up a notch. Or it could be something else.

In general, an isolated incident isn't enough to form a fully noted opinion on your heart rate. Look for patterns and see what develops from them. Try charting it. As you become more fit, your HR may slow. I know that before I started working out truly consistently about 7 years ago, my RHR was about 70 BPM. Now it's 40 - and I do have to work a lot harder to get it rolling along where I want it for my intensity than way back when walking a mile would do it. In some cases that can be bad, but because it's a result of my fitness - it's actually a good thing. My heart has become more efficient.

But once again - if you have any doubts, see a dr. No one can substitute for that.

I definitely wouldn't use advice from here to replace a doctor's opinion, but as I get to bother my doctor enough as it is about my other (non-related, so far) ailments, and I had just been to see him recently, I was wondering if it might be some mundane, common workout-related phenomenon.

That said, I'm going to see a doctor tomorrow morning to get things checked out :nod: I took the day off from the gym today (had a bunch of errands to run, anyhow), and I will take the morning off tomorrow (but as soon as he says it's all clear, I'm bussing my ass back to the gym).

I replied on something like this before. It's simply overtraining - probably only slightly, maybe a couple of bad nights and not quite enough food. Take 1-2 days off cardio and hit it again, you should be fine. You body is trying to make it hard for you so you can't do too much.

Progressively getting lower and lower HR for a given speed can be a sign of training fitness (but not an absolute), but usually takes a few months.

Well, I got back from the doctor, and I've been given a clean bill of health! :D Actually, to quote him, he says that I am "the picture of health, compared to how you were last year".

So yeah, the heart rate thing was probably just from a overtraining and having a bad day. After my doctor's appointment, I decided to go home and nap, instead of hitting the gym. I hadn't had a good sleep the night before. I'll be going back to the gym tomorrow.

On a side note, I have a very devoted trainer: she happened to come by while I was waiting for a bus, and drove me home while she was on the way to work. She said she recognized me immediately by my track pants (which now seem to be always surgically attached to my person :o )