I typically burn 100-140 calories with a heart rate monitor but the benefits of fitness in a set( for time) from a physics perspective might be more. There are two points that come to mind.
1. The work done by each rep and multiplied by the number of reps(Kinetic Work)
2. The rest of the time in between the reps(potential work)
While the heart rate monitor might be off it bases its calculation on heart rate. What is interesting is what happens after the set is finished.
This had been done a few times. I'll use this.
I had a 5k run in 22.5 minutes
Average Heart Rate 165
I had one 102 reps for 10 minutes with OALC without setting the weight down and switching every minute. 1 32kg bell. Average HR 175. Peak 185.
With Scenario 1: Burned 390 calories in 22.5 minutes and 160 in 30 minutes following
With Scenario 2: Burned 280 calories in 10 minutes and 250 in 30 minutes following
In this case the HR monitor doesn't know the activities themselves are different. IT calculates intensity based on an exponential curve of HR approaching higher beats per minute. Even though the kettlebell workout had been only slightly higher with intensity it made a bigger difference during and especially after the set. Metabolism becomes increased and stays increased for longer. Based on a workout, It had been 1200 calories-1600 in the first 90 minutes and who knows as it dropped off during the rest of the day and following day. The thing I notice is that reps per minute do make a difference. Weight does not necessarily have an effect in that reps per minute with lighter weights being inversely proportionate make p the difference with a lighter poundage. The difference might matter more after the activity stops such as a higher HR for longer. Gotta keep searching. ;) Get to work and use the HR monitor to see what is happening.