Now, more than ever, she had to keep up her strength.
I hope both of you are eating well to keep up your strength.
Still, she had to eat to keep up her strength.
John had been trying to keep his strength up for the last hour.
Some left to eat perhaps to keep their strength up.
I want you to keep your strength up for the games.
Common sense told him that he had to keep his strength up for later on.
Keeping his strength up was going to be hard work.
You have to keep up your strength for a case like this.
Eating well is important to keep up your strength and health.