According to this website,http://www.heartmonitors.com/exercisetips/aquatics.htm, the Aquatic Exercise Association states that "Even using the 6 second pulse count, a 13% or 17 beats per minute deduction should be taken from the exerciser’s land-based minimum and maximum training thresholds, according to AEA, due to the effects of water I have described."
Does anyone believe this is true? 17 beats seems like a lot.
YES
My experience is 10, maybe 15 BPM lower for aqua than land at same exertion.
I think I am about 15-20 bpm slower. I believe for men it is on average 10-17 and women 15-22 bpm slower in water than on land. It is also affected by the temperature of the water. But I know that I can kill myself in the pool and my heart rate is well below my max.
Drop your aqua jogger in a whirlpool (104 degrees) and see what it does to your heart rate.
The temp of the water is what makes the big difference.
I believe the standard explanation from physiologists has to do with the water pressure increasing venous return. I've aqua jogged in warm pools, cool pools, and even Adirondack lakes, and while the temperature does make a difference (as it does on land), I wouldn't say it's the majority of the land vs. water differential, at least not at typical pool temps.