# What causes a greater rate of calorie burn during an activity?

What causes more calories are burnt per min during an activity? Is there a list of all major factors? Ideally answers should be scientifically proved or backed but if not then just a list / ideas what it could be is fine. (Just for clarity, by activity I don't mean, e.g., eating but an exercise like walking, running, bike, gym, ... .)

I'd assume the biggest (or only ?) factor is increased heartbeat that an activity causes.

If there are more factors than this then what is the ratio that they contribute to calories burn per unit of time?

• Do you mean "What causes a greater rate of calorie burn during an activity?" – Jason Sep 22 '16 at 0:10
• @Jason - Yes, that's it. – B J Sep 23 '16 at 19:43

This is just plain old physics. The amount of calories burned is based on the amount of work it put in.

Work = Force x Distance

Force = Mass x Acceleration

So based on that, you can put in more work (thus burn more calories) by either moving more mass at the same pace, moving the same mass at a faster pace, or both.

10,000 joules of energy (Work) is equivalent to roughly 2 calories.

For example, say you had a 100 kg sled. You were able to push it at a rate of 10 m/s^2 (because you're extremely fast and powerful).

100 kg x 10 m/s^2 = 1,000 Newtons (N)

1,000 N x 10 m = 10,000 joules or roughly 2 calories.

Of course this is a very simplified view of the whole picture. Pushing a sled is harder than running. Running is harder than cycling (on a flat surface). There are other factors that go in to play like friction, surface angles, wind resistance if you're outside, etc.

The point I'm trying to get across is the amount of calories that burn is determined by the amount of work that is done.

Regarding heartbeat, this can be a way to measure the amount of effort a person is pushing. People who have been working out for years will be more efficient than people just starting out, so they will burn less calories for the same work. Likewise, experienced people will also have slower heartbeats because of how relatively efficient they are.

If you mean- what is the best easily observable indicator of rate of calorie burning during exercise, then in general for any given exercise the harder your heart and lungs are working, the more calories you are burning.

With calorie burning though, you're better off keeping your heart down so you can sustain the activity for a longer time. If yo're doing something and your heart rate is 80%, 90%, 100% max, and you're burning 20+ calories a minute then by definition you're doing high intensity exercise, possibly anerobically, and you won't be burning 20 cals a minute for long because you'll have to quit.

To burn the most calories, it's more important to exercise at a rate you can sustain for a longer time.

• Not necessarily. It's a function of intensity versus duration, as well as EPOC (Excess post exercise oxygen consumption). Heart rate is a very minor factor that is very person specific, and can be affected by many things outside of the actual exercise. Say I go for an hour run today and tomorrow. Assume same conditions, today my HR stays around 120, tomorrow I had extra coffee and my HR is 144. Assuming everything else is same, am I suddenly burning 20% more calories for same effort? – JohnP Oct 28 '16 at 15:31
• Many exogenic factors can be introduced to raise heart rate. Maybe someone drinks coffee, maybe someone does cocaine or meth. maybe someone has a panic attack. The OP was asking about a single individual, compared at a single moment of time, whose heart rate was being elevated owing to immediate exercise effort- the assumed topic of this SE - and I qualified it further by limiting it to a single given exercise. The OP wants to know the best way to estimate rate of calorie burn. Under those qualified circumstances, heart rate is an effective estimate. – Kirby225 Dec 5 '16 at 14:30