It's important to activate your stomach muscles to support your back.

激活你的腹部肌肉来支撑你的背部很重要。

Just make sure that your back is straight and that your stomach muscles are tight so that it keeps you solid.

要确保你的背部保持笔直，这样你的腹部肌肉就会收紧，保持坚实状态。

Relax your stomach muscles, then stretch again.

【muscle】放松腹部肌肉，然后再伸展。

You can do exercises to strengthen your stomach muscles.

【exercise】你可以做体操来增强腹部肌肉。

He had seen his brother George do it, and George had explained that it kept the stomach muscles firm and was a fine abdominal thing to do.

他看到哥哥乔治就是这么做的，乔治解释说那会令腹肌变得结实，因此是一个很好的锻炼腹部的方法。