I did a little experiment to see how much it would affect my heart rate. 5 miles on the treadmill at 12 min miles plenty of fluids and my heart rate never got above 132. 5 miles same pace no fluids my heart rate got up to 160 by the end of the run.
I had no idea fluids made such an impact. There are a lot of times I have wondered why my heart rate would be higher when running at the same pace one time to the next. I now realize that I was probably just dehydrated. If my max heart rate is 190 does that mean if I let myself dehydrate and allow my heart rate to get up towards 190 that a run or ride is soon going to end. It’s like I found a new training tool. I know what my heart rate should be at a certain pace and if it is above that then I need more fluids. Obviously terrain makes a difference but typically I run the same route so it should not fluctuate much. Is it really that simple or am I missing something?
Unless its over 80 degrees, I would never stop and get fluids for a five mile race. Maybe this changes my outlook but I always thought it just wasn’t worth it. In fact on colder days I’ll run about an hour with nothing.
Question as far as I can tell was, ‘can I use HR at a set pace to gauge hydration status?’. Quick answer is no - several factors can affect exercise HR independent of hydration status. Also, as you improve cardiovascular endurance, an identical workload may well elicit lower HR. IOW, running speed should go up at a given submaximal HR if your aerobic endurance improves.
Second part of the question, I think, was, ‘if my HR goes up to 190 does that mean my run is going to end?’ If your HR is at 190 due to dehydration while you’re running (let’s say it’s about 40 beats elevated), you won’t need a HR monitor to figure out you’re dehydrated.
@ Dave from VA - you can test this for yourself. Run w/ a bottle on a hot day/in the gym and drink, or don’t. Repeat each condition five times on the same course under sim. conditions and average things out. I’ll run the stats for you :-). The larger point in this is that we’re sometimes married to our HR zones and fail to see that HR is a (sometimes poor) substitute for power output - which is what really matters.
Sorry I did such a shitty job posting. Sort of threw it out there to see what would stick. The test was done indoors on Monday(no water) and Wednesday(with water). Both runs on a treadmill same temp in basement both days(70 ish), same speed same time frame. I guess I was just surprised that hydration would make that much difference. Granted one test does not make this a done deal but to me it seems to show how important water is even on runs that last less than an hour.
My question more or less was if my lactate threshold was at a heart rate of xxx(pick a number, its not relevent cause I don’t know it) and I allowed my heart rate to get there because I got dehydrated will I still burn out or will my lactate threshold move up because I am dehydrated. I’m not sure if I’m making sense with this. Hypothetically you should only be able to run for 5 minutes at heart rate x. If I get dehydrated and my heart rate goes up because of it and I hit heart rate x then will I run out of steam in 5 minutes? If my heart rate is elevated 10 bpm because of dehydration does it mean I am exactly 10bpm closer to lactate threshold or is lactate threshold a function of power output not neccesarily heart rate
It seems to me that all things equal (same treadmill run, etc…) I should be able to look at my heart rate monitor and tell if I am taking on enough fluids.
Sorry if I’m not doing a good job getting this across
w asked: is lactate threshold a function of power output
short answer: yes, LT is a function of power output, not HR.
If you want to get really technical, LT can be affected by cardiac output (and therefore HR to some degree, because cardiac output equals stroke volume multiplied by HR), barometric pressure, and maybe even restrictive clothing. But, power output is more related to LT, closer than HR anyway.
If under optimum conditions, you last 5 minutes at heart rate x, do you really think that when you are dehydrated you will still last 5 minutes at heart rate x?
I think you will collapse much sooner. I think you could prove it too.
These questions have been bugging me for awhile too. The LT question is part of it, but for me, it’s always been about when I’m trying to train in a specific zone (let’s say Zone 1) and I experience an elevated HR which I believe is due to drift (since my pace/power feels about equal to any other workout),
The question is: should I back off on the power/pace to get my HR back down into Zone 1, or just work from a perceived level of effort, trying to keep a “Zone 1” kind of feeling to the workout, and ignore my HRM?
