Biomechanics bench press for powerlifting

[Hønter]

Since I train powerlifting I have started to get interested in the mechanical analysis of the different exercises. But the bench press I haven't been able to figure out. When I am considering a dumbbell bench press the mechanics seems simple, but when I consider a barbell bench press it becomes difficult. If you consider the situation with dumbbells, the torque at the shoulder is the force from the bar (F) times the horisontal distance between A and C. The same for the torque at the elbow which is the F times the horisontal distance between B and C. But when the hand is fixed to a barbell things get changed. So can someone please help me figure this out. If you could use the figure or make your one figure and explain the forces and torques involved i would appreciate it.

 

[BradP]

If you assume the hands remain symmetrical to each other, can't you divide the weight of the barbell in half and analyze each arm as if it were holding a dumbell?

When finding the torque of the elbow, make sure you also account for forces at the shoulder.

 

[Hønter]

If you assume the hands remain symmetrical to each other, can't you divide the weight of the barbell in half and analyze each arm as if it were holding a dumbbell?

No, I don't think its that simple. If you training with a barbell your hand is locked in a straight vertical path and it seems like the hand becomes the axis of rotation, not the elbow, or something like that. If we consider the dumbbell situation i think the torque at the elbow would require the biceps to contract to produce an equal amount of torque in the opposite direction of the torque generated by the force from the bar. This is when the forearm is pointing outwards and is not vertical. But when you train with a barbell, you contract the triceps instead to press the weight.

Does any of this make sense??

 

[G037H3]

From what I can tell, you need to focus on the elbows and hands if you want to calculate force. With a barbell, your hands essentially remain at a constant distance, so pressing the bar up would be firing the chest, shoulder, and triceps, and then holding the bar at the top with the forearms and shoulders. This should mean that there is a point, based on the length of the upper and lower arms, where the power is transferred from one to another most efficiently. (I guess you could think of this as finding the shortest possible vector from the beginning of the movement, to the top, within the confines of maintaining the necessary constant distance between the hands, but don't take my word for it.) With dumbbells you have more of a range of motion, so that means that getting the weight up would be a function of maximizing the amount of range that most muscles push the weight up within.

Also keep in mind that in weight training, the point is to isolate muscles, so calculating based on maximum efficiency (as I have alluded to) isn't what you are going for.

 

[Vinodh Physio]

Hi this is a nice thread and I would like to participate in your discussion.

I have a strong doubt that during barbell bench press, the role of and the load on pectorals is much greater (at the same time lesser role of and load on triceps) than dumbbell bench press. I have been thinking to experiment on the same and get a right conclusion.

 

[Vinodh Physio]

In Dumbbell bench press, both the dumbbells are allowed to contact each other during each push which enables humerus on both sides to adduct more and attain a vertical position before returning back to neutral (see Figure-A & B- first image) . In Barbell bench press, the distance between the hands remains constant hence scope for humerus to adduct is limited up to 60 degrees (approximately) from horizontal (see Figure-A & B – second image). In Dumbbell bench press, triceps must act concomitantly to extend the elbow, because during adduction of shoulders, the elbows can tend to flex and hands moving towards the chest (see figure-C- first image).

If we keep the load constant, Dumbbell bench press may demand more energy output from push muscles than barbell bench press. The reason for this is greater work done during dumbbell bench press due to greater distance traveled by the load from neutral position to end position.

(You may read my entire article on this topic in www.ezinearticles.com[/URL])

 

[abramroyy]

The Big bench pressers are always highly reserved , especially because someone with a massive bench can inspire everyone to just power-lifters. To top it all off, the bench press is the only true test of upper body strength in the power-lifting team. Finally, and let's be honest here, that who doesn't want a big bench. It should be stated that well-planned training, proper nutrition and recovery , and a great deal of dedication and courage are a must to be successful at this sport.


Bench Press Max
improve your bench press