Symmetric heart rates

A training app checks whether a workout was perfectly mirrored: the heart-rate samples during the cool-down should retrace the warm-up exactly, so the whole session reads the same forwards and backwards. Given the list rates, return True if it is symmetric (a palindrome of values) and False otherwise. Compare from both ends inward instead of building a reversed copy. Example: [90, 110, 130, 110, 90] is symmetric.