Bike testing: different LTHR for Indoors vs Outdoors?
Hello all,
For my first test to start the OS, I rode outdoors and did an approximate 40min stretch after a long warmup. I looked at my Garmin Training Center lap splits (every mile) to see where my average HR was. As it turned out, it was right around 164.
As it is very unlikely that I will be able to ride outdoors for my next test, I was wondering what, if any, difference I can expect for indoor LTHR testing?
Other than one specific day, I haven't had any problem hitting my HR for my intervals. I have noticed that my average speed for the intervals has increased (~1.0 mph or so), so work is definitely working. 
Given that most talk about different FTPs for indoors vs. outdoors, I am curious as to what everyone else has seen and experienced as an HR athlete.
Thanks in advance,
Joe
Comments
What was the temperature?
How much did you eat?
How hydrated were you?
How much sleep did you have?
What time of day was it?
etc.
There are just so many factors. For those of us with a power meter, a watt is a watt. The difference between indoors and outdoors is how your bike interacts with the trainer as opposed to the road. I'm not sure your heart rate shares a similar relationship and if it did, I'd think it would be difficult to quantify it because of the other factors affecting heart rate.
Main factor in outdoor HR vs. indoor HR is lack of cooling effect when riding indoors. Riding outdoors, there is a constant breez you create that keeps you cooler even in 95F+, indoors you can only mitigate it with fan, which I found a must unless you want to be recovering from heat exhaustion all the time. I ride in a very cool garage and add fan to it. How does one's HR respond, it is very individual, but your outdoors HR will do very little for you indoors.
Look a few threads up, this has been discussed in more depth even with a link to a site that explains the reasons in decreased power output indoors.