I've picked up weight lifting recently and the thing I've noticed is that it really gets the heart pumping. After a heavy set of squats for instance I can hear my heart beating in my ears and feel it beating in my chest.
However my heart rate monitor says that, while it's increased, it's not that much faster than normal. My heart rate is far faster while riding a bike, but it doesn't beat as 'hard' then.
Why does it feel like my heart is beating harder in these cases? Why is it different to beating faster like when doing cardio exercises? Would this 'harder' heat beat burn more calories than a normal strength heart beat at the same bpm?