What is the fastest way to incease my athletics skills in Morrowind?

According to the Notes on the Unofficial Elder Scrolls Pages - Morrowind:Athletics

You can quickly train Athletics with minimal effort by toggling on Autowalk while facing a wall. This will passively increase Athletics skill without your character accidentally walking into trouble. A more effective way to do this is to swim towards a wall; a well-suited place for this is the river running through Balmora.

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also can't jump quite literally an inch of the ground

this is actually your Acrobatics skill which is separate from Athletics

The Acrobatics skill involves jumping, climbing, and avoiding damage from falls

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• With an extremely excessively high acrobatics skill it is possible to jump from one end of the map to the other.

a quick way to increase this skill is to jump while running up a slope. i tend to find the slopes for going up level on the outside of Vivec's Cantons are great places because each jump will help improve the skill no matter how high you jump, jumping up against a slope as you go up it mean you do lots of tiny jumps. i believe i've counted 10-20 jumps from one slope in the Foreign Quarter