Why programming for the clavicular, sternal, and costal divisions yields more results than just "chest training".
Building a fuller chest isn’t just about more benching; it’s about where you bias load and range of motion across a fan-shaped muscle with multiple origins. The pectoralis major’s fibers run in different orientations from the clavicle, sternum and costal cartilages toward a shared insertion. That geometry means different pressing paths and ranges preferentially load different regions – and a one-size-fits-all bench press approach leaves portions under-stimulated.
If you don’t address regional bias, you’ll keep chasing incomplete results: persistent “gaps” in the upper or lower chest, asymmetric shape when flexed, and slow transfer of strength to exercises that need balanced development. For a trainer, that’s not just an aesthetic issue – it becomes a programming blind spot that undermines your own progress as well as your clients'.
Worse, poor attention to regional muscle development compounds over months of training. Repeatedly loading only the sternal-dominant pressing pattern can entrench movement habits, create strength imbalances around the shoulder, and limit long-term hypertrophic return. The solution is practical: understand the divisions, how they behave, and select implements and paths that bias each region over time.
Key terms you need to know to program for a full pec hypertrophy.
Below are the three anatomical regions of the pec. Your programming should evolve to emphasize all three divisions over months of training:
- Clavicular division
- Sternal division
- Costal division
Each pec division defined and how it behaves anatomically.
${component=BasicCard}Clavicular Division
The clavicular division (commonly called the “upper” pec) originates from the medial portion of the clavicle. Its fibers run obliquely downward and laterally toward the humerus, meaning they contribute most when the arm moves upward and inward relative to the torso – for example, on incline pressing and shoulder flexion-adduction paths. This region tends to be shorter in length and responds to different moment arms than the sternal fibers, which changes where tension is felt through a lift.
${component=BasicCard}Sternal Division
The sternal division is the largest central mass of the pectoralis major, originating on the sternum and adjacent costal cartilages. These fibers are more horizontally oriented and are the primary drivers of horizontal adduction and pressing force in flat pressing patterns. Because it comprises the bulk of the muscle, it often dominates common gym pressing movements, which explains why many trainees feel their “middle” chest develop first.
${component=BasicCard}Costal Division
The costal division (sometimes referred to as the “lower” pec) originates from the lower costal cartilages and the abdominal fascia. Its fibers run upward and outward toward the humerus and are preferentially loaded with downward pressing paths and movements that include scapular depression or a more pronounced torso lean, such as dips. The costal fibers are functionally linked to scapular control and often benefit from loading through movements with a greater stretch portion.
Target even growth across all three regions of your pec with three practical steps.
${component=Step}Target the clavicular fibers by pressing with higher shoulder flexion angles.
Use an incline pressing variation (preferably dumbbells) set between 25–45° to align load with the clavicular division's fiber orientation. Dumbbells enable more natural scapular movement and greater humeral extension, which is beneficial for hypertrophy goals. Perform 2–4 sets of 8–12 reps with deliberate eccentric control (1–2 seconds) and smooth transitions into concentric phases. Prioritize this region in hypertrophy cycles as it's often underdeveloped compared to other pec regions.
${component=Step}Bias the sternal division through horizontal adduction-focused pressing.
Emphasize horizontal pressing where the humerus moves straight away from the sternum when stretching – classic flat bench or flat dumbbell presses fit well. Avoid excessive thoracic extension to prevent shifting load to the costal fibers. Program 2–4 sets of 6–10 reps with steady tempo – this is a stronger range because the bulk of the pec fibers attach to the sternum. For variation, try a cable press or machine fly – loading potential may be lower, but the resistance profile allows for more consistent tension on the sternal fibers.
${component=Step}Emphasize the costal division with movements that demand scapular depression and shoulder extension.
Load the costal fibers with dips or decline pressing paths that position the upper arm behind the torso and require scapular depression. Program 2–4 sets of 8–12 reps using assisted or bodyweight dips, decline machine presses, or cable flys with the cam set above the shoulder. Start with depressed scapulae and allow the arm to travel back, then progressively engage scapular retraction and elevation toward the bottom of the eccentric phase for controlled loading.