冬練三九，夏練三伏 [－练－－－－练－－]

Jyutping dung1 lin6 saam1 gau2 ， haa6 lin6 saam1 buk6
Pinyin dōng liàn sān jiǔ ， xià liàn sān fú

Definitions (Wiktionary)
  1. phrase, idiomatic
    to carry out training in the coldest and the hottest parts of the year