There are mortgages that still amortizase over thirty years which are equally principle and interest. Of course that’s still 30 years of interest, but much easier to cash out with a refinance or sale.
Jumping rope at the gym to 1000. It was too fast to say the numbers mentally so I had to visualize a counter. With each jump I had to see the number I was on. This was more difficult than the actual jumping rope. Mental exercise + physical exercise = compounded gains.