練習時間と結果の関係2 https://energy.jp/blog/2016/05/18/%e7%b7%b4%e7%bf%92%e6%99%82%e9%96%93%e3%81%a8%e7%b5%90%e6%9e%9c%e3%81%ae%e9%96%a2%e4%bf%82%ef%bc%92/