Source: Unearthed Arcana 38 - Feats for Skills

You become stronger, gaining the following benefits:

  • Increase your Strength score by 1, to a maximum of 20.
  • You gain proficiency in the Athletics skill. If you are already proficient in the skill, you add double your proficiency bonus to checks you make with it.
  • You count as if you were one size larger for the purpose of determining your carrying capacity.