|“||Your physical strength determines your ability to use heavy weapons and armour without tiring, and to carry heavy loads, including your wounded comrades. Strength affects the blunt damage you do with heavy weapons, hacking-type blades, and while unarmed. It is trained faster by using heavier weapons in battle, or by traveling with a very heavy inventory or encumbrance.||”|
–in-game stats menu
Strength affects your carrying capacity before you start to slow down. In 0.96.26, the formula for carrying capacity is 15 + strength.
In combat, your strength exp is gained by attacking. Every strike you land, even if blocked by the enemy, is what grants you strength exp. Defending grants no experience at all.
Strength, along with Armour Smithing and Weapon Smithing, also affects the bulk of your character. At 1 Strength, a character will display as fairly thin and frail. At 100 Strength, they will appear much larger and bulkier.
A similar system governs the definition, or visibility, of the muscles. Except it uses Dexterity and Martial Arts, and to a lesser extent Athletics and Swimming. While Cooking and Science have a negative effect. See the picture attached to see what the character looks like at specific skill levels for bulk and definition.
Strength has a large effect on the speed with which characters swing heavier weapons. At 100 Strength, a user could swing a Fragment Axe weighing 72kg about the same speed as a Hungry Bandit can swing a 3kg Iron Club.
An effective way to train strength would be to fill a backpack with Raw Iron or other heavy items, a Shopkeepers Backpack would work best, and then when it is full put it in your inventory without wearing it. You then have all the weight inside the backpack working on your character. Then have them follow a guard or policeman around a city. They will then continue to walk around whilst carrying this weight, accumulating strength experience rather quickly and autonomously.
If you have a party of more than 1 person, you can also train strength by ordering one of your people to carry the other via the 'pick up' command (hold down the right mouse button on the character to be carried) and ordering the carrier to walk as usual.
At 72% Encumbrance the maximum 25% Strength XP is reached, further Encumbrance only diminishes the Athletic XP gain. You can reach a 50% by picking up any character, including Animals.
You can use combat to train strength as well. Using a weapon that weighs at least 20kg over your strength level will gain you a fair amount of XP per swing. But the lighter you go under that the worse XP you get, eventually dropping down to as low a x0.1 XP rate.
Alternatively, you can overload your inventory much like the passive training method above, and then go fight using Martial Arts. Each hit you make will give a you a HUGE boost to strength XP relative to the other methods. However, this is also the most dangerous method. As you are slowing yourself down to the point where running away from a fight is near impossible. And also significantly crippling your combat stats by being over-encumbered. But it is by far the fastest training method for Strength, and trains several other stats in the process.