Treadmill Running and Relearning the Basics

I've had my new treadmill now for about 1 month - first run on 5/4. I resorted to this treadmill running to be able to continue training thru the hot/humid weather in Houston without having to slow significantly (outside running is about a minute per mile slower for same heartrate). I've logged 18 runs for a total of about 180 miles and I thought I'd take a look at the data of these 180 miles and see what I can learn. For the datasource - just about all those miles were run wearing my Garmin HRM and as the treadmill readouts shows a milemarker I manually hit the lap button on the Garmin to record mile times. After the first few runs I began to program the AC to knock the inside temperature down to 70°F for the run for increased speed. For the most part the mileage has been one of three types of mileage - Recovery (~140 bpm), Easy (~150 bpm), MP Pace (160-164 bpm) and a few faster miles. I put these on a x-y scatter plot for mileage vs heartrate taking out about 30 miles that were transitional (first miles in a run as heartrate is ramping up, first mile after a step change in pace up or down as the heartrate is ramping up or down) and also taking out the first few days that were before I lowered the AC. Here's what the data looks like:

In the Pink - I've separated out the last couple days of running as I am testing a new theory on why the day to day variation in speed - for example at 150 bpm there are points from 6:15 to 7:00 mpm for the same heartrate. So - what is the new theory that so far (2 days) is keeping me at the fastest end of the range?

Well - first I'll tell you how I got to it. In trying to figure out why the variation I was attempting to correlate things like days since last hard work or days since training outside in the heat. The heat acclimation one specifically I was focusing in on as I've seen some relationship between low heartrate and heat acclimation. Well the first stage of acclimating to the heat I've read is the blood plasma volume increases which reduces the viscosity of the blood (makes it thinner) and makes it easier to pump around so the heartrate goes down for the same effort with higher blood plasma. I figured the volume of blood plasma was probably the variable that was changing that made the heartrate higher one day vs the next. I did a few Google searches for how to impact the blood plasma - how to maximize the volume for greatest efficiency and I came to the most obvious answer in the world.........Drink more. Duhhhh. Of course while running the sweating which comes from the blood plasma reduces the blood volume so if it is not replenished adequately before the next workout I'm starting from a slightly dehydrated state (and have thicker blood). So Sunday and Monday I put extra focus on drinking lots of water at every opportunity - and there it is...low heartrate per pace - at least for two days so far. I'm also a bit of a coffee addict especially on weekdays so the caffeine is likely also blocking some of the needed hydration - I've been cutting back on that too.

Pfitzinger's book "Advanced Marathon" suggests hydration requirements at 4 pints (normal non-working out demand) + 1.5 times the fluid loss during training. For today's workout (10 miles ~150 bpm in 64 minutes - the pink points above 150) I took my weight before and after and found 2.7 lbs lost so I should be drinking ~8 pints per day. Of course I knew hydrating was important but I can't say I've ever put much focus into making SURE I do enough daily and those kinda volumes don't happen without some planning - so now I'm going to give that more focus and see if that keeps my mileage down more aligned with the Pink line of the graph. We'll see how it works.

John.