Sjhuk - I am no expert on this but I would not sweat about a few beats either way. Your HRM will not be completely precise and your HR has a natural variability anyway depending on temperature etc, just keep it there or thereabouts.
Nayan - i had VO2 max, lactate threshold and max HR tested at the London metropolitan university. The max HR was determined by a controlled exhaustion test on a treadmill, with the speed being steadily ramped up until you reach your limit. I have read elsewhere that your HR at the end of a hard run 5k is close to your max HR and that seems to be the case for me assuming I "sprint" the finish.
Training like this took me in the last 6 months from someone who struggled to run 3 times a week without getting injured to someone who can run 50 mile weeks without getting injured.
from personal experience:
- ensure that you have the right HR calculation, this is really important. If you are using a % of HR Max, ensure that you have your Max HR measured Properly. The 220-age formula usually used is very inaccurate - for example I had mine measured in a lab on a treadmill (backed up by wearing a HRM for flat out 5 k races) and it is 193. The standard formula says it should be 180 and if I were to set my HR zones on that basis I would have to walk! I read Phil Maffetones book and used his simple formula (google it) for aerobic base HR and it worked well.
- it takes time to show results training like this, and in my experience (backed up by some reading on the subject) volume makes a big difference. Low volume meaning slow progression. I trained steadily going from 20-30-40 miles a week and I saw very slow progress until I started getting 30-40 miles and 5 runs a week after which my aerobic pace dropped from 10:30 to around 9:15 in about 3 months and my fitness rocketed. Of course everyone is different, the key is to take it slow as if you ramp up volume too quickly you will just get injured and be back to square one.
- results did not seem linear for me e.g I seemed to be making no improvement for 4-6 weeks and then suddenly I would be looking at my pace and thinking "wow, where dis that improvement come from?"
- training this way made a huge difference to training for my second marathon, for my first I was always injured, I could really "feel" the base I had when I started training for my second and I was able to execute and recover from training much better.
- getting home feeling like you have not done anything is how it should feel. you should almost feel more refreshed than before you started.....
Good news is that it sounds like you have come out of it better that I have - I could barely walk yesterday and I am still having trouble with stairs today and i am generally absolutely shattered, heavy chest etc - running again is some way off I think!
Whilst i am very happy with my time I think it would have been nicer to have started slower and had something left at the end, rather than being at the limit of blow up pace for the first half and hanging on for dear life for the second. It is pretty clear I pushed myself to the absolute limit.
Some similarities between us here. I did Brighton on Sunday also and i had a big dilemma as to what pace to go out at prior to the race:
- I am 39, running 2 years
- First marathon
- PB for 1/2 (Brighton in Feb) 1:42:40
- Did a 20 mile race in 2:53 6 weeks ago; ran 10 miles at 9mm, then ran next 10 at 8:15 pace, came hoem feeling great!
- I trained about 35 miles per week from January, 3 20+ milers
Based on the above I was convinced I had 3:45 in me. However I posted up my data over on the US RW forum and they had some fairly consistent advice that 3:45 was too much, based on my relatively low milage and limited running history. the advice that stuck with me was "start with the 3:45 pace group and let them go".
In the end I got stuck a way back behind the 3:45 group, and I decided to wear my HR monitor (which i always train with) for the race and use my HR to judge the right effort level.
I ended up raining myself in to around 8:40-8:45 pace for the first half of the race, and i still paid for it in the second where I slowed by about 3 minutes. The undulations of the first half really seemed to take it out of me, and I was tired at mile 17 but kept going and managed to finish in 3:51 just about fighting off cramp the last 2 miles. From about 18 miles I felt I was on the verge of blowing up, and felt utterly destroyed at the end; I am certain that had i gone out following the 3:45 group I would have been walking at around 18 miles; I also think had i ran a more consistent 8:50 pace for the first half I might have got home maybe just under 3:50.
I learnt a few things from all this:
- Race time predictors are not to be trusted unless you are doing high mileage. My HM time almost led me to making a huge and painful mistake on race day, and I was lucky I asked a question on the US forum.
- There is a huge difference between 20 and 26 miles, it really shocked me on the day how much harder it was than the 20 mile race.
- I will be more conservative next time about my pace at the start
- I need to run more miles
I hope my analysis helps yours. I think from my own experience and times you just unknowingly set yourself an impossible pace at the start.