Muscle activity in m.pectoralis major during bench press variations in healthy young males

Abstract: Background. The bench press is a commonly used resistance training exercise for targeting the chest musculature. During hypertrophy training, different variations of bench press are often used to isolate different segments (pars clavicularis, pars sternocostalis and pars abdominals) of the chest muscle m.pectoralis major. Commonly used variations of the bench press are decline bench press (less than 0° from horizontal) and incline bench press (more than  0° from horizontal). Some research has been done into these variations of bench angle and their effect on muscle activation; however other commonly used bench angles is yet to be investigated. Aim. The aim of this study was to examine if there were any difference in muscle activity in the three segments of m.pectoralis majors while performing three different barbell bench press variations with different bench angles to obtain a greater understanding of m.pectoralis major activation and possibly optimize hypertrophy training in above mentioned muscles segments.  Method. 13 healthy male (age: 23± 3.8 year and BMI: 24.3 ±1.8 kg/m2) participated in this single group study. EMG was used to measure muscle activity in m.pectoralis major's three segments. Test subjects performed 1 set of 6 repetitions on each bench press variation at a relative load of 6RM. An maximal voluntary isometric contraction (MVIC) test was performed and set as 100 percent reference value for comparison muscle activity in various angles. Results. While performing the decline bench press and the incline bench press, the muscle activity in pars clavicularis displayed a strong trend of a lower muscle activity (decline: p= 0.055 and incline: p=0.052) in comparison to the flat bench press. Muscle activity in pars sternocostalis while performing the incline bench press was significantly lower in comparison to the flat bench press (flat: p<0.001 and decline: p<0.001). Muscle activity in pars abdominals while performing the decline bench press was significantly higher (p=0.013) in comparison to the flat bench press. Muscle activity in pars abdominals while performing the incline bench press were significantly lower than both the flat and decline bench press (incline: p<0.001 and decline: p<0.001). Conclusion. For a better isolation of the pars abdominals segment, the decline bench press should be used. Muscle activity in pars sternocostalis did not show any significant difference between flat and decline bench press and could be isolated with either of these two exercises.  The muscle activity in pars clavicularis showed a strong trend of higher activity while performing the flat bench press compared to the decline and incline bench press, however findings regarding the pars clavicularis differs between studies.