How to burn calories whilst performing a bicycle crunch?

Patient

Q: Hi, i really need an accurate and detailed description of what it is that causes calories to be burnt when performing a bicycle crunch. I'm writing a health and fitness report, and ive been given confusing, conflicting answers from various other sources. When performing a bicycle crunch does the lowering and extending of one leg/knee as close as possible to the floor burn more calories than the crunching up of the other leg/ knee to the chest. Or is it the crunching up of the leg/ knee to the chest that burns more calories than the lowering and extending of the other leg/ knee to the floor. Does the lowering and extending/ straightening of the leg burn any calories at all. Also, do concentric contractions burn calories and do eccentric contractions also burn calories.

And, does the lowering/ extending of the leg/knee have to as close as possible to the floor in order to burn more calories than if it is lowered to a position higher up from the ground i/e not as close to the ground.Also, does the leg/ knee have to be crunched up to the 90 degree position in order to start burning calories, or are calories burnt as soon as the leg/ knee starts crunching up from a straightened/ extended position. In other words, are the same amount of calories burnt when the leg/ knee starts contracting only by a slight distance from the straightened/ extended position (i.e not all the way up to the 90 degree level), or does the leg/ knee have to be contracted to the 90 degree position and above on order to burn calories.

Further, how do you know when the leg/ knee is at chest height when crunching it up. Is it the leg/ knee being pressed as close to the chest as possible that means the leg/ knee is at chest height, or is it the leg/ knee being raised as high into the air as possible that means the leg/ knee is at chest height.

If i performed bicycle crunches with smaller contractions i.e one leg/ knee crunching up only slightly and not very far to chest level and the other leg/ knee being lowered not very far to the ground & extended/ straightened not completely (i.e not completely straight), would this burn the same amount of calories as performing bicycle crunches with larger contractions i.e one leg/ knee crunching up at a longer distance and up to & past the 90 degree level and the other leg/ knee being lowered very far to the ground & extended/ straightened completely out. Thankyou for your help and kind regards,
Kelly.

Doctor

A:   Hello,
Thank you for your medical query at AskTheDoctor.com
I understand your concern.

When you are performing a bicycle crunch, you burn maximum calories, when you extend the leg straight all the way parallel to the ground, and pull the legs as close to your chest as possible with your knees bent.
Concentric contractions burn more calories.

Regarding the angle, it should be a 45 degree angle, however, you start burning calories as soon as you start pulling the leg up from the ground, since it requires muscular contractions, and any muscle contraction starts burning calories.
As I mentioned, the knees should be bent while it is coming to the chest, and it should be extended parallel to the floor when you extend it back.
The only way you burn more calories is by doing more repetitions in a given amount of time. Shorter contractions also help if you can maintain and do it in a correct way.

I will appreciate if you can post the questions number wise in follow-up as specific queries.

Please feel free to discuss further,
Regards.

Comments / Follow Ups

Patient: Hi, when performing a bicycle crunch does the leg/ knee have to be crunched up all the way to the armpit in order for the leg/ knee to be at the same height as the chest. Or does the crunching up of the leg/ knee to the armpit just burn more calories than the crunching up of the leg/knee to just the 45 degree level to the chest. Are significantly more calories burnt (eg 1 and more calories) with the crunching up of the leg/ knee to the armpit compared to the crunching up of the leg/knee to just the 45 degree level to the chest. Also, is it the crunching up of the leg that burns more calories or is it the lowering of the leg into the extended/ straightened position that burns more calories. And, does the leg being lowered as close as possible to the ground when being extended/ straightened back out burn more calories or does the height of the leg/ knee from the floor not really affect the number of calories burnt. Thankyou for your help and kind regards,
Kelly.
Doctor: Hello,
Yes, I already mentioned it has to be crunched up to the armpit. This ensures complete squeezing of the core muscles.
But the calorie difference is not much. Now, for every repetition you may have an additional 0.5 calories burnt due to more squeezing of the abdominal muscles. So if you can do more reps, the calorie count will go up.

The leg should be straightened back and should remain parallel to the ground without touching the ground. It should be as low as possible to burn maximum calories.

Hope this was helpful,
Regards.

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