The triceps muscle is the primary contributor to arm size. It makes up roughly two-thirds of the upper arm's volume, while the biceps make up the remaining third. A well-developed triceps adds noticeable width and fullness to the back of the arm, creating a more pronounced horseshoe shape.
Other factors influencing arm size include:
- Genetics: Some individuals naturally have larger arms due to bone structure and muscle insertions.
- Body fat percentage: Lower body fat allows for greater definition and visibility of muscle mass.
- Training: Focusing on compound exercises like dips, close-grip bench press, and overhead press can stimulate triceps growth.
- Nutrition: Adequate protein intake supports muscle growth and recovery.
