Chest thickness predicts bench press far more than arm length does
In short
In a study that measured 26 Paralympic powerlifters by panoramic ultrasound, pectoralis major thickness was the structural variable most strongly associated with maximum dynamic bench press strength. Each additional centimeter of pectoralis thickness was associated with roughly a 56% increase in performance (p=0.008), each centimeter of triceps brachii thickness with roughly 34% (p=0.001), and each additional centimeter of arm length with roughly a 4% reduction (p=0.033). Long arms are a real disadvantage, but a small one next to what muscle thickness contributes.
The most common explanation for a stalled bench press is arm length: longer arms mean a longer bar path, so the lift is harder. This study put a number on that disadvantage by measuring it alongside muscle architecture rather than on its own.
The subjects were 26 Paralympic powerlifting athletes. Panoramic ultrasound captured regional architecture of the pectoralis major and triceps brachii, and a generalized linear model related those measurements to maximum dynamic strength.
What was measured, and where?
The measurement sites were specific. Cross-sectional area and muscle thickness of the pectoralis major at 15% and 30% of clavicle length, and of the triceps brachii at 50%, 60% and 70% of humerus length. At the 60% triceps site, pennation angle and fascicle length were also recorded.
The design does not ask whether a big chest benches more. It asks which region of the chest being thick actually matters.
Which variable mattered most?
Pectoralis major thickness at 30% of clavicle length was positively associated with maximum dynamic strength (coefficient 0.2023, p=0.008). Each additional centimeter of thickness at that site was associated with an expected performance increase of about 56%.
Triceps brachii thickness at 60% of humerus length was also significantly and positively associated (coefficient 0.290, p=0.001), corresponding to roughly a 34% increase per centimeter. The authors' conclusion was explicit: of everything measured, pectoralis major thickness had the greatest magnitude of association with performance.
How much do long arms actually cost?
Arm length was negatively associated with performance (coefficient -0.039, p=0.033), at roughly a 4% reduction per additional centimeter. So the disadvantage is real — and at the same time, per centimeter, pectoralis thickness carries more than ten times the weight.
The practical reading is simple. Arm length cannot be changed and muscle thickness can, and the coefficient on the changeable one is far larger. "My arms are long" is part of the picture, but too small a part to be the conclusion.
The subjects were Paralympic powerlifters, whose bench press is performed with the upper body alone — no leg drive, no arch — so the mechanics differ from conventional powerlifting. This is also a cross-sectional study of 26 athletes, so these are associations, not causes. "56% per centimeter" is a model estimate from this sample, not a promise that adding a centimeter of chest raises your bench by 56%.
What does this change in training?
The most direct use is an order of operations for a stalled bench. In this data the association ran pectoralis thickness first, triceps thickness second, with specific sites attached — 30% of clavicle length for the chest, 60% of humerus length for the triceps.
In other words, choosing accessories that build chest volume first and add triceps second is consistent with what was measured. Angle selection for the upper chest is covered in the incline dumbbell press and the upper chest.
It is also worth holding this next to the fact that muscle size and strength are not simply proportional — that question is in the correlation between muscle size and strength.
What it means for a strength score
The Muscle Index sums squat, bench and deadlift 1RMs and then corrects for bodyweight, sex, age and height. The bench is therefore a third of the total, and typically the lift that stalls longest of the three.
The usable message is to check muscle thickness before concluding it is your skeleton. The index does not correct for arm length, though it does correct for height — a coefficient applies to every centimeter above 170 cm. See where your total sits in the strength calculator.
Frequently asked questions
Which body structure is most associated with bench press performance?
In this study it was pectoralis major thickness. Measured at 30% of clavicle length, it showed the strongest positive association with maximum dynamic strength, at roughly a 56% performance increase per additional centimeter (p=0.008).
How much of a disadvantage are long arms in the bench press?
In this study of 26 Paralympic powerlifters, arm length was negatively associated with performance at roughly a 4% reduction per additional centimeter (p=0.033). The disadvantage is real but small next to the roughly 56% associated with a centimeter of pectoralis thickness.
How much does triceps thickness contribute to the bench press?
Triceps brachii thickness measured at 60% of humerus length was significantly and positively associated with performance, at roughly a 34% increase per additional centimeter (p=0.001). That is the second-largest association after pectoralis thickness.
Do these results apply to conventional powerlifting?
With caution. The subjects were 26 Paralympic powerlifters, whose bench press is performed with the upper body alone and therefore differs mechanically from a conventional bench using leg drive and an arch. It is also cross-sectional, so it shows association rather than causation.
Where should you build first when the bench press stalls?
In this data the order of association was pectoralis thickness first, triceps thickness second. Choosing accessory work that secures chest volume first and adds triceps after is consistent with that finding.
Source: PubMed