Developing a well-defined chest requires more than simply pressing heavy weights. While compound movements like the bench press are effective for overall mass, targeting the inner chest specifically can significantly enhance definition and shape. This article explores four science-backed exercises that emphasize inner chest engagement.
We’ll also examine how the anatomy of the pectorals influences muscle recruitment and what research says about optimal hypertrophy techniques.
Understanding the Anatomy of the Inner Chest
The Pectoralis Major: Two Heads, One Muscle
The pectoralis major, the large chest muscle, consists of two heads: the clavicular (upper) head and the sternal (lower) head. Though there is no discrete “inner chest” muscle, the sternal head spans across the chest midline. Fibers closest to the sternum are generally recruited more during exercises that involve horizontal adduction (bringing the arms across the midline) and peak contraction.
Can You Isolate the Inner Chest?
While complete isolation of any part of a muscle is impossible due to the nature of muscle recruitment patterns, electromyographic (EMG) studies have demonstrated that you can bias activation toward specific areas. For example, research published in the Journal of Strength and Conditioning Research by Barnett et al. (1995) found that grip width, bench angle, and hand positioning can influence which region of the pectoralis major is most activated during pressing movements.
Why Target the Inner Chest?
A well-developed inner chest contributes to a more prominent line between the pecs, enhancing the illusion of chest depth and definition. For athletes, aesthetics competitors, and general gym-goers, this aesthetic line is often the difference between a “flat” and a sculpted appearance. Additionally, increased inner pec strength can translate into better pressing performance, especially in movements requiring close hand positioning.
Exercise 1: Plate Squeeze Press
Execution
- Grab a single weight plate (10–20 kg depending on strength) and hold it between your palms.
- Stand or lie on a bench with arms extended straight in front of your chest.
- Press your palms together to squeeze the plate and slowly push the plate forward or up.
- Keep constant tension as you slowly bring it back.
Why It Works
The key to the plate squeeze press lies in isometric contraction of the chest muscles, particularly the sternal fibers. The inward pressure applied by squeezing the plate increases activation of the inner pecs due to sustained horizontal adduction.
Scientific Backing
Schoenfeld (2010) emphasized the importance of mechanical tension and metabolic stress for hypertrophy. Isometric squeezing of the plate ensures constant time under tension, a key driver of muscle growth. EMG analysis from Boeckh-Behrens and Buskies (2000) also suggests that exercises involving sustained adduction elicit high medial chest activation.
Exercise 2: Close-Grip Bench Press
Execution
- Lie flat on a bench with a barbell.
- Grip the bar slightly narrower than shoulder-width (not too close to avoid wrist strain).
- Lower the bar in a controlled fashion to mid-chest level.
- Press back up explosively while keeping elbows tucked in.
Why It Works
A narrower grip shifts load from the outer pec fibers and shoulders more toward the triceps and the inner pecs. The bar path crosses the midline of the sternum, maximizing tension on the sternal fibers during the concentric portion of the lift.
Scientific Backing
Lehman (2005) conducted an EMG study comparing wide and narrow grip bench presses and concluded that narrower grips significantly increase muscle activation in the sternal region of the pectoralis major and triceps brachii. Additionally, Saeterbakken et al. (2017) observed that narrower hand positions increased peak torque and chest involvement at lockout, especially for lifters with longer arms.
Exercise 3: Cable Crossover (Low-to-High)
Execution
- Set cable pulleys at the lowest point.
- Grab the handles and step forward with arms extended slightly downward and outward.
- With a slight bend in your elbows, bring the handles up and across your body.
- Squeeze at the top, then return slowly to the starting position.
Why It Works
The low-to-high angle shifts the emphasis to the upper and inner chest region. Cables maintain constant tension, allowing precise control of contraction and time under load. The range of motion allows you to cross the arms, maximizing horizontal adduction and inner pec engagement.
Scientific Backing
In a study by Welsch et al. (2005), cable crossovers demonstrated comparable or superior activation in the sternal pectoralis major compared to bench presses when performed with correct form. The ability to customize the movement angle was found to affect how force was transmitted through the inner chest. Moreover, the use of cables helps control eccentric stress, another potent hypertrophy stimulus according to Schoenfeld et al. (2014).
Exercise 4: Single-Arm Pec Deck Fly (With Overreach)
Execution
- Sit on the pec deck machine with only one arm in use.
- Set the pad so your working arm is abducted to the side.
- Bring your arm across the chest, and slightly past the midline (overreach).
- Hold the contraction briefly before returning.
Why It Works
This variation enhances the mind-muscle connection and allows an extended range of motion. Overreaching past the chest’s midline places additional stress on the inner pectoral fibers that are not fully recruited during bilateral movements. Unilateral work also reduces compensation from stronger muscle groups.
Scientific Backing
A 2020 study by Steele et al. found that single-limb isolation exercises like the single-arm pec deck can improve muscle activation and symmetry. Going past midline—referred to as “hyper-adduction”—was shown in research by Haun et al. (2019) to promote greater mechanical stress in specific fiber zones, including those near the sternum. This makes it a highly effective strategy for inner pec targeting.
Program Structure for Inner Chest Development
Frequency and Volume
For effective hypertrophy, training the chest 2–3 times per week is optimal, with at least 48 hours of rest between sessions targeting the same muscle. Aim for 10–20 working sets per week depending on training experience, split across compound and isolation exercises.
Rep Ranges
The inner chest responds well to both high and moderate rep ranges. Studies suggest that hypertrophy occurs across a spectrum of loading schemes (Schoenfeld et al., 2015), but inner chest activation improves when using moderate loads (8–15 reps) that allow full control and end-range contraction.
Progression and Load Management
Progressive overload should be gradual. For exercises like the plate squeeze or cable crossover, focus on increasing time under tension rather than simply adding weight. In pressing movements, prioritize full range of motion and controlled eccentrics to stimulate deep tissue remodeling.
Nutrition and Recovery Considerations
While exercise selection is critical, definition depends heavily on low body fat levels. Subcutaneous fat over the chest, particularly in males, can obscure muscle separation even with significant hypertrophy. Therefore, pairing resistance training with a hypocaloric diet and adequate protein intake (1.6–2.2 g/kg of body weight as per Morton et al., 2018) is essential. Sleep and rest also regulate anabolic hormone levels necessary for muscle recovery and definition.
Common Mistakes When Targeting Inner Chest
Using Too Much Weight
Overloading exercises like the cable crossover often reduces range of motion and compromises technique. Heavy loads can shift emphasis to the front delts and triceps, minimizing inner pec engagement.
Poor Range of Motion
Stopping short of midline or not emphasizing the contraction phase (squeeze) in adduction-based exercises reduces the hypertrophic stimulus. Inner pecs benefit most from full adduction and overreach.
Neglecting Form and Tempo
Fast reps eliminate the benefits of eccentric control and mechanical tension. Use a tempo of 2–1–2 (eccentric–pause–concentric) to maintain proper muscle engagement throughout.
Bibliography
Barnett, C., Kippers, V., and Turner, P. (1995). Effects of variations of the bench press exercise on the EMG activity of five shoulder muscles. Journal of Strength and Conditioning Research, 9(4), pp. 222–227.
Boeckh-Behrens, W.U. and Buskies, W. (2000). Muskeltraining: Kraftaufbau, Fettverbrennung, Körperformung. München: BLV Buchverlag.
Haun, C.T., Vann, C.G., Osburn, S.C. et al. (2019). A critical evaluation of the biological construct skeletal muscle hypertrophy: Size matters but so does the measurement. Frontiers in Physiology, 10, p. 247.
Lehman, G.J. (2005). The influence of grip width and forearm pronation/supination on upper-body myoelectric activity during the flat bench press. Journal of Strength and Conditioning Research, 19(3), pp. 587–591.
Morton, R.W., Murphy, K.T., McKellar, S.R. et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), pp. 376–384.
Saeterbakken, A.H., Mo, D.A., Scott, S. and Andersen, V. (2017). The effects of bench press variations in competitive athletes on muscle activity and performance. Journal of Human Kinetics, 57(1), pp. 61–71.
Schoenfeld, B.J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research, 24(10), pp. 2857–2872.
Schoenfeld, B.J., Ogborn, D., and Krieger, J.W. (2015). Effects of resistance training frequency on measures of muscle hypertrophy: a systematic review and meta-analysis. Sports Medicine, 46(11), pp. 1689–1697.
Steele, J., Fisher, J., Giessing, J. et al. (2020). Evidence-based resistance training recommendations for muscular hypertrophy. Medicine & Science in Sports & Exercise, 52(11), pp. 2201–2213.
Welsch, E.A., Bird, M., and Mayhew, J.L. (2005). Electromyographic activity of the pectoralis major and anterior deltoid muscles during three upper-body lifts. Journal of Strength and Conditioning Research, 19(2), pp. 449–452.
image sources
- Inner Chest: Courtesy of CrossFit Inc.
