Bench Press - The Truth About the Effects of Bench Angle on Pec Activity Varies Depending on the Phase of the Lift

The bench press, in one form or another, is part of almost everyone's workout, but what's the best way to do it?

You may have seen Brad Schoenfeld's post about the just accepted study of his that confirms the well-known link between muscle activity and poundage (higher weight = higher activity | see EMG Series). Well, another recent study provides additional intricate insights into the link between muscle activity and the way you perform the bench press.

Just like Schoenfeld et al.'s study, the study compared the muscular activation during bench presses - albeit in this case that of the pectoralis major, anterior deltoid and triceps brachii during a freeweight barbell bench press performed at different angles: 0°, 30°, 45° & -15° angles, to be specific.
As the authors from the Department of Kinesiology, Cardiopulmonary and Metabolic Research Laboratory at the University of Toledo point out, this is not as "boring" as you may think it is,, as previous investigations may have systematically examined muscle activation during various bench press conditions only throughout the complete lift. Needless to say that "[d]uring any resistance exercise a complete ROM is important", but Jakob D. Lauver et al. are right to point out that there may be potentially relevant differences in the level of muscle activation over the course of the full range of motion (ROM). The latter could be significant enough to...

"[...] have the potential to attenuate any difference in muscle activation observed during the complete lift between bench angle conditions as differences in activation may have been evident throughout different time points of contractions" (Lauver. 2016). 

Accordingly, the primary purpose of the present investigation was, as Lauver et al write "to compare the changes in muscle activation at various time points across contraction phases (concentric, eccentric) during free-weight barbell bench press at varying bench angles (–15°, 0°, 30°, 45°) while maintaining the same absolute resistance load" (Lauver. 2016). The scientists hoped that the results of their study would lead to a better understanding of the effect of bench angle on muscle activation during bench press exercise and "aid in selection of variations in bench press exercise to develop upper extremity strength and musculature" (Lauver. 2016).
For their study, Lauver et al. recruited 14 healthy resistance trained men (age 21.4 ± 0.4 years) who performed one set of six repetitions for each bench press conditions at 65% one repetition maximum. As in previous studies, Lauver et al. used surface electromyography (sEMG) to quantify the muscular contraction. In contrast to previous studies, however, they analyzed the corresponding data during four parts of the lift individually - not just for the whole lift.

Figure 1: Upper and lower (U- / L-) pectoralis major activity during eccentric (UA / LA) and concentric (UB / LB) quarts of the bench press at different angles (-15°, 0°, 30° and 45° | Lauver. 2016).

This is important, because their data showed no difference during any of the bench conditions, when the scientists examining the complete contraction and/or only the concentric part (pushing the bar up) of the contraction. A different picture emerged, however, when Lauver et al. analyzed the four phases of the eccentric and concentric phase individually:

• Differences were found for 26–50% contraction for both the 30° [122.5 ± 10.1% maximal voluntary isometric contraction (MVIC)] and for 45° (124 ± 9.1% MVIC) bench condition, resulting in greater sEMG compared to horizontal (98.2 ± 5.4% MVIC) and –15 (96.1 ± 5.5% MVIC). 
• The sEMG of lower pectoralis was greater during –15° (100.4 ± 5.7% MVIC), 30° (86.6 ± 4.8% MVIC) and horizontal (100.1 ± 5.2% MVIC) bench conditions compared to the 45° (71.9 ± 4.5% MVIC) for the whole concentric contraction. 

Overall, the study results obviously still confirm what you've read previously at the SuppVersity: "[T]he use of a horizontal bench to achieve muscular activation of both the upper and lower heads of the pectoralis" (Lauver. 2016).

This doesn't mean that adding an incline press to your regimen would be useless. As Lauver et al. point out, there's still use for the incline bench press - specifically at 30°!, because it "resulted in greater muscular activation during certain time points", so that the overall results of the study suggest "that it is important to consider how muscular activation is affected at various time points when selecting bench press exercises" (Lauver. 2016).
References:

• Lauver, Jakob D., Trent E. Cayot, and Barry W. Scheuermann. "Influence of bench angle on upper extremity muscular activation during bench press exercise." European journal of sport science (2015): 1-8.
• Schoenfeld, Brad J; Contreras, Bret, Vigotsky, Andrew D.; et al. "Upper body muscle activation during low- versus high-load resistance exercise in the bench press." Not yet published; private communication on Facebook (2016).