祖父は九十歳を過ぎても頑健で、毎朝畑仕事をしている。
Even past ninety, my grandfather is robust and works in the fields every morning.
彼は頑健な体の持ち主で、風邪ひとつ引いたことがない。
He has a sturdy constitution and has never so much as caught a cold.
若い頃に山で鍛えたおかげで、体が頑健になった。
Thanks to training in the mountains when I was young, my body became strong and healthy.