Ultrasound measurements of the combined thickness of the biceps and brachialis muscles at two specific points along the upper arm can reliably detect muscle growth in men who have not previously...

Pro

Against

Mechanism

Synthesis from 1 study

How it works

When arm muscles get bigger from training, they thicken in predictable spots along the upper arm. Ultrasound can measure this thickening very precisely because it uses sound waves to see the muscle edges clearly at the same spots every time, making it easy to spot even tiny growth.

Most probable mechanism

In Simple Terms

When muscles grow thicker, the amount of tissue between two fixed points on the arm increases, and ultrasound can accurately capture this change by bouncing sound waves off the muscle edges at consistent locations along the bone.

Causal chain

Muscle fibers increase in diameter due to protein synthesis and sarcomere addition during resistance training, leading to an increase in muscle cross-sectional area.

Verified by multiple studies

which leads to

The combined thickness of the biceps brachii and brachialis muscles at 50% and 70% of humerus length corresponds to regions where muscle bellies are most voluminous and least affected by fascial or adipose tissue variation.

Verified by multiple studies

which leads to

Ultrasound imaging captures the distance between the superficial and deep aponeuroses of the muscle, providing a direct, non-invasive measure of muscle thickness that scales linearly with cross-sectional area.

Verified by multiple studies

which leads to

Reproducible probe placement at standardized anatomical landmarks minimizes measurement variability, allowing small changes in muscle thickness to be detected with high precision.

Verified by multiple studies

Evidence from Studies

Supporting (1)

Community contributions welcome

The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise

Randomized Controlled Trial

Human

2026

Contradicting (0)

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No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Source Study

The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise

Score: 60

DOI: 10.3389/fphys.2026.1750722

Similar Assertions

To measure muscle growth in the upper arm, researchers use specific measurements including the muscle's cross-sectional area, thickness at two points along its length, and the circumference of the arm at three different positions.

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In untrained young women, performing bicep exercises through a shorter range of motion (from fully extended to halfway bent) leads to more muscle growth near the elbow than using a longer range (from halfway bent to fully bent), but both approaches result in similar muscle growth in the middle of the bicep.

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Ultrasound can reliably measure arm muscle size in active women, and the same person can get consistent results when repeating the measurement—making it a trustworthy way to track muscle growth from workouts.

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