The athlete hit his chest during the game, causing pain in the sternal area.

sternal 是由名词 sternum（胸骨）加上形容词后缀 -al 构成的形容词。sternum 指人体胸部正中央的长条状骨骼，-al 表示"与...相关的"。sternal 意思是"胸骨的、与胸骨相关的"。