noun
prime of life; prime of manhood
Refers to the period of peak physical and mental vigor, typically for men. Somewhat literary or formal.
彼は壮齢に達し、仕事でも家庭でも充実している。
He has reached the prime of life and is fulfilled both at work and at home.
壮齢を迎えた彼の体力はまだ衰えていない。
Now in his prime, his physical strength has not yet declined.