And again... the elephant in the room continues to be ignored.
E=MC2
A rifle dangling at arm's length being tossed around to acquire/maintain balance punches way above its weight class. Those "minor" bursts of speed require intense energy far beyond expectations.
Everyone carrying a rifle in hand while climbing a nasty incline instinctively knows it makes a difference. That rifle is live weight.
The formula points out energy equals mass times velocity squared, period.
But C in that formula is the speed of light???
Yeah, that formula is describing mass/energy duality. Nothing to do with classical mechanics in terms of inertia or kinetic energy. A more relevant equation would be E_k = 0.5mv^2.