You basically want the bar to travel in a straight line.Having the bar travel less distance from your chest to the lockout will make your lift stronger and more efficient
Biomechanics of The Bench Press
This information has been posted multiple time on StrongFirst.
Dr. Tom McLaughlin, (PhD Exercise Biomechanics)
McLaughlin published a research article on the Biomechanical Path of the Bench Press in the National Strength and Conditioning Research Journal in 1984.
McLaughlin's book, "Bench Press More Now: Breakthroughs in biomechanics and training methods", came out on it the same year.
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Dr. Greg Nuckols article provides the research data from McLaughlin in his article on "How To Bench Press"; the most efficient Bar Path Trajectory.
I have McLaughlin's NSCA Research article and book.
Below is an illustration of the most effective method of Bench Pressing.
As demonstrated, the Bench Press Bar Path is an arc, rather than trying to drive the bar straight up.
Mike Bridges Bench Press
Bridges was one of the greatest Squatters and Bench Pressers in Powerlifting.
Bridges Bench Press was over 500 lbs, at 181 lbs, in a T-Shirt.
McLaughlin's Biomechanical Research over time with Bridges revealed that his Bench Press increased by slightly modifying the arc of his Bench Press Bar Trajectory, in driving the weight up.
By shifting the Bench Press Bar Trajectory, Bridges was able to decrease the load in the weaker position of the lift.
As McLaughlin noted,
"Technique is everything".
Leg Press Analogy
A lifer can Leg Press more on a 45 Degree Leg Press than if they were to perform it on a completely Vertical Leg Press; pushing it straight up.
That due to the the angle of the 45 Degree Leg Press. Research shows that with a 45 Degree Leg Press the True Weight is 70% of the Total Load on it.
Thus, if someone is performing a 45 Degree Leg Press with 500 lbs, the actual Leg Press Load is around 350 lbs.
That same concept applies when Bench Pressing with an arc.
Perpetuation of Misinformation
Ironically, 38 years (2022-1984 = 38) after the Bench Press research, "The Bench Press In A Straight Line" misinformation continues to be perpetuated.
Even Dr. Greg Nuckols article from a few years ago, based on his research (one of the references from McLauglin) didn't slow down or put a dent in this erroneous Bench Press information.
Bench Pressing In A Straight Line
There is no research to support it.
While Benching In A Straight Line would appear to be more effective, it isn't.
The Body does not move in a Straight Line.