There have been a couple of messages recently on the forum regarding the right HR and using HR in races. I thought the following might prove a useful example as to how right/wrong things can get if you don't use the right figures.
Firstly in the training thread I mentioned that my planned session tonight is a marathon simulation run which I plan to run at around 75% effort.
First of all important factor is to apply resting heart rate (RHR) from maximum heart rate (MHR) to get working heart rate (WHR). I know my RHR is 42-43 but were I to use any of the age based formula I would come up with a maximum between 183 and 187 (various forumla applied, 220 minus age the most well known produces a value of 183, whereas a "fit" variation - 205 minus half age - produces a value of 187). However, I know that my stress tested maximum is closer to 195.
So my WHR is 195 less 43 which equals 152. When quoting percentage of effort you need to be careful whether the programme you are looking at is percentage of maximum or percentage of WHR. For example at 75% of MHR (195) produces a training target HR of 146 (75% x 195) whereas a method based on WHR gives a target rate of 157 (remeber when using a WHR forumla to take the % of your WHR and add your RHR to get your training target rate - in this example 75% x 152 + 43).
So depending on which MHR I elected to use (stress tested or age related) and whether I applied a straight % of maximum or percentage of WHR makes a huge difference to the suggested training HR - in this case a target HR between 137 and 157 a range of 20 beats which would make a huge difference to actual pace.
I know the 157 is reasonable based on experience in training and races but for beginners I think this is a good example as to why you should be careful in applying HR to your training and not to rely on HR alone in the early training phases but to first use your HRM to gather data.
.........I'll get me coat!