This is the 1774th most frequent Russian word.
здоровью
"To health" (dative case of "здоровье").
In this sentence, "здоровью" here represents the concept of health in the dative case due to the usage of the verb "сказывается".
Этот комплекс упражнений благоприятно сказывается на здоровье.
This exercise complex positively affects health.
Here, "здоровью" is used in the dative case to denote attention given or intended towards the person's health.
Он уделяет особое внимание своему здоровью.
He pays special attention to his health.
The word "здоровью" is again in the dative case, representing the purpose or beneficiary in relation to sports activities.