Assessing the effect of stability, Goodman et al. (2008) found no difference in latissimus dorsi muscle activity when performing the free - weight bench press on a stable bench or Swiss ball. (strengthandconditioningresearch.com)
Comparing the effect of bench angle, Barnett et al. (1995) explored the difference in latissimus dorsi muscle activity between bench angles of 18 degrees below horizontal, 0 degrees (flat), 40 degrees and vertical. (strengthandconditioningresearch.com)
Norwood et al. (2007) explored the effect of increasing instability on latissimus dorsi muscle activity during the bench press performed on a (1) stable bench, (2) with the feet placed on a BOSU ball, (3) Swiss ball, or (4) Swiss ball with feet placed on a BOSU ball. (strengthandconditioningresearch.com)