So I was wondering if there are formulas to calculate the energy expenditure of common lifts, like deadlifts, bench press, squat etc. I know that every formula could only be an approximation, due to differing technique, execution speed etc.
I was just curious if such formulas exist and if so, how accurate they are.
If they don't exist, why is that? Did just noone care to find out? Is it not feasible due to one of the factors mentioned above (or other factors), if so which?
Yes there has been some earlier research regarding this.
For example there is an article that tried to measure exactly this by Robergs et al. in 2007 (I've uploaded the pdf with a sharable link at the end of the post since it's a paywalled article). I won't go too deep into the formulas used as it's explained in the article. Some interesting findings were that he has a table that shows a rough estimate of kcal burned per repetition at a certain intensity. The researchers used for each repetition a 3 second counter, meaning the predicted kcal burned are estimated in repetition ranges of 20. It predicts for example that performing a squat at 62.5% intensity for 1 minute while sustaining 20 reps would lead to a predicted burning of 16.95 kcal.
The one flaw of this study I find though is that it didn't really attempt to quantify very high intensity exercises in the above 85% 1RM range, which is also harder since it's only sustained for a short period of time.
ROBERGS, R. A. , GORDON, T. , REYNOLDS, J. & WALKER, T. B. (2007). ENERGY EXPENDITURE DURING BENCH PRESS AND SQUAT EXERCISES. Journal of Strength and Conditioning Research, 21 (1), 123-130.
link:
https://pdfhost.io/v/zz9ZlcDFN_Energy_expenditure_during_bench_press_and_squat_exercises
A= m*a*s;
mass*acceleration*s-distance.
or
A=F*s Force;
http://en.wikipedia.org/wiki/Work_(physics)
I do not think it is very easy to calculate force though. when i do the math i usually estimate force as gravity force and acceleration as Gravitational acceleration.
Why it is not very important is : energy expenditure during the lift is not important (very small compared to daily non exercising expenditure). This is because of small distance of the movement. I once calculated that to burn a kilogram of fat i need to carry 100kg of iron to the distance of 36 kilometers (maybe i am mistaken here but not by too much) which is ridiculous.
This formula is important for aerobics(aka cardio). Moving your body(50 -100kg) over long distance does the trick.
While work does equal force times distance, the rest of Sergey's commentary is rather absurd. His calculation presumes 1 dimensional motion and forces, people don't move in one dimension first off. Secondly, carrying 100kg involves gravitational force and simply standing still with 100kg on your back will result in increased caloric consumption due to the 981N pushing down on your body and requiring muscle activation to not fall over from carrying the weight (your muscles are contracting and causing mass to move over distance). Additionally there is the calories burned from travel (100kg≈1000N 7700Cal/kg 0.000238845896627 calories/N•m, this equates to about 32.23km to burn 1kg of fat along the x-axis only) This does not account for calories burned in stabilization, calories burned due to metabolic processes such as converting ATP to and from ADP among other things, metabolic efficiency, anaerobic threshold, etc. Also, HIIT cardio and weightlifting also result in excess post-exercise oxygen consumption. Since O2 is a required for cellular respiration (anaerobic exercise doesn't excrete waste effectively until you stop working and permit the respiratory system to blow off CO2, the other other pH regulatory systems don't act fast enough to be relevant) it is the primary indicator of caloric consumption. This effectively means that while lifting weights on it's own doesn't burn as much calories during a workout, they burn more calories post workout (this doesn't count increased caloric consumption due to increased muscle mass.)
Short story: if you're trying to calculate work done based off of your estimated range of motion, you're wasting your time. While the fundamental point of Sergey's post was correct, it left out some pertinent details. As I don't really feel like getting into the physics of all of it in any deeper fashion than I already have, I'll ask that you take my word, as an engineering student, that between the lack of precision of measurement and the sheer amount of calculations required to figure it out would take time that would be better spent working out, resting, eating, or any number of things. So yes, there are formulas that you could use to figure it ou should you have sufficiently precise measurements, but the benefit of figuring it out doesn't even remotely come close to justifying the effort.
One additional factor that none of the other answers factor in is that power lifting not only requires the energy expenditure to rebuild the muscles after a lift. I don't know exact numbers but your body burns a significant number of calories rebuilding muscles. Add on to that the fact that muscles need to burn calories just to maintain themselves having more muscle means your body will be burning more calories while you go about your life. Long story short actually measuring a Joule or KCal energy expenditure is more or less useless but strength training does lead to a large amount of caloric expenditure both during the activity and after.
