Kids' bones are not as strong as they used to be because they don't play outside that much these days.
1) Kids' bones are not as strong as they used to be because they don't play outside much these days.
「最近の子供は外であまり遊ばないので、(昔の子供に比べて）骨が強くない。」
bones は「骨」
are not as strong as they used to be で「昔の子供に比べて強くない」
ご参考になれば幸いです！
日本 
