It's times like this that we have to do weight-training.
「こんな時こそ筋トレ」は英語で「It's times like this we have to do weight-training.」と言います。「こそ」は前のことばを強調する単語でこの場合なら英語で「It's times like this」と言います。
こんな時こそヨガをしましょう。
It's times like this that we should do yoga.
こんな時こそ家でご飯をつくりましょう。
It's times like this that we should cook food at home.