I have been on a fat loss program for the past 6 weeks or so and my cardio routine involves continuous stationary bike work 5-6 times a week.
When I started my resting heart rate was around 75 bpm. This morning I checked my heart rate while lying in bed and it was 54. It kinda shocked me…
Is this normal to have a drop this significant in only 6 weeks?
-Dave-
I would expect about a 10 beat RHR decrease; you ARE doing alot of cardio. Was the 75 BPM taken before you got out of bed too? If not, that may account for 6-8 BPMs, IMO.
Scipio,
Yes the initial measurement was taken at waking 6 weeks ago. I never really checked it much but decided to check this morning for some reason. It kinda shocked me…
-Dave-
don’t worry about it. unless you’re symptomatic, low heart rates are extremely efficient. the lower your heart rate (within physiological limits), the greater the loading of blood volume and ejection of the same providing a more efficient circulation.
a friend of mine who is involved with athletics has a normal heart rate of <60 bpm.
bjorn borg had extremely low heart rates while playing tennis (that’s WHILE playing).
SO, the lower the heart rate, the more the heart fills, the stretch of the heart muscle is greater, and hence the contraction is even greater. this results in a higher efficiency of heart function. be glad 
The other thing to consider, of course, is consistent readings. You may have ocassional highs (like your initial reading of 75) and lows (like your 54), but if you take it each day upon waking or for periods of 3 days at a time, you’ll probably have a better idea of what your “true” resting heart rate is, and what impact your program is having on it. In other words, your 75 could have come after a particularly restless night, or as an indication of overtraining or illness, or stress, etc. Almost everything you do, (or don’t do) will be reflected by your RHR.