Final answer:
The total load should be increased by 5-10% per week in strength training based on the principle of progression.
Step-by-step explanation:
To effectively implement the principle of progression in strength training, the total load should be increased by a certain percentage per week. The appropriate percentage increase per week is typically recommended to be in the range of 5-10%. This gradual increase ensures that the muscles are consistently challenged and stimulated for growth and improvement.