However, this is only true when comparing the same absolute load, and not the same relative load of each of the bench press variations tested. (strengthandconditioningresearch.com)
This would then explain why eccentric training tends to produce greater gains in strength overall, because eccentric training typically involves greater absolute loads (as well as more muscle damage). (strengthandconditioningresearch.com)
They reported that internal oblique muscle activity was highest with either lower body instability (feet on BOSU) or combined upper body and lower body instability (BOSU and swiss ball) but the same absolute load of 9.1 kg was used for all conditions. (strengthandconditioningresearch.com)