Use a subquery to separate selecting the rows from computing the average.
It seems you want to filter your data with ORDER BY date DESC LIMIT 7, but you have to consider, that the ORDER BY clause takes effect after everything else is done. So your AVG() function considers all values of restingHR from your $userId, not just the 7 latest.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.