More tracking of resting HR

Got struck with an under the weather feeling again in the household, you know temperature, raging headache and chest ache... so some annoying virus or other... I've taken a look at what my resting HR was doing ... now I began to feel crap on Sunday but thought I was just tired from a good night out. My run on Monday felt harder then it should for easy and again I thought I was just fatigued from training... when I got on the bike on Tuesday and felt really nasty I began to suspect something more was up ... itchy throat by Tuesday evening, raging heavy head on Weds and Weds night disturbed sleep, sickness and temperature... 

and the resting HR picture... jumped up to 54 then 57 on wednesday, stayed there thursday.... 

I've rested up totally from Wednesday to today and you can see my average resting HR (according to fitbit) has come back down to 52... compare this to the period just before I went on holiday when I felt a similar virus attack..... going from RHR around 50 up to 58

So this seems to validate that for me (in my sample of two times) that if I get an increase of 6-8 beats in my RHR (fitbit takes it as an average over the course of a day excluding periods of activity) then I probably had hit the vitamin c quickly.... indeed tri 220 magazine recently said as much...  although actually by the time that happens it's probably too late anyway as the lurgy is lurgying! .. ... but I could use it as a motivation for training - ie if my RHR is still within normal tolerance (which I would say is between 52-54 BPM) then if I feel tired I probably am just tired not necessarily unwell and so training can be done and not use a feeling of general malaise as a reason for not bothering.