This is coolbert:
"War is a game for young men!" With regard to the physical demands it is.
"The need to balance and reduce a soldier’s load is as old as warfare with technology creating additional burden with new ability as well as reducing them through eliminating weight in existing kit. In addition innovative approaches to discipline, education and supply can aid the process to increase soldier effectiveness in the field"
[click on all images to see an enlarged view]
First the Great War. As carried by the common soldier.
This represents the complete existence load as was issued to the American soldier during the Great War [WW1]. Fighting load consisting of uniform with helmet and boots, rifle with bayonet and ammo, canteen filled, load bearing web gear, entrenching tool, first aid kit, bare minimum rations for several days. Everything else to include the bedroll, extra rations, hygiene kit and apparently a Bible add to the fighting load and you have the existence load. Back in my day those were the two categories of load as understood. Fighting and existence. Hand grenades and gas mask as issued only according to need and demand?
Now for the modern  load as carried by a platoon leader [2nd lieutenant].
Load now categorized as: * Mobility, * Lethality, * Survivability, * Sustainment.
With regard to the platoon leader load let me clarify:
VS17: Marker signal panel.
AN/PAS-13: Thermal weapon sight.
ACH: Advanced combat helmet.
AN PVS-7B/D: Night vision goggles.
IOVT: Improved Outer tactical vest.
IOVT totally replaces in totality the previous more conventional web gear? IOVT has a pouch front and reader that can hold an ceramic armor ballistic plate able to stop an AK ball round. Each ballistic plate weighing eight pounds [about 3.6 Kg.].
Again, no gas mask included!