SB 10.44.3

aratnī dve aratnibhyāṁ
 jānubhyāṁ caiva jānunī
śiraḥ śīrṣṇorasoras tāv
 anyonyam abhijaghnatuḥ
Word for word: 
aratnī — against the opponent’s fists; dve — two; aratnibhyām — their fists; jānubhyām — their knees; ca eva — also; jānunī — against the opponent’s knees; śiraḥ — head; śīrṣṇā — with head; urasā — with chest; uraḥ — chest; tau — they in pairs; anyonyam — each other; abhijaghnatuḥ — struck.
Translation: 
They each struck fists against fists, knees against knees, head against head and chest against chest.
Purport: 

The word aratni in this verse may indicate the elbow as well as the fist. Thus blows were perhaps also struck with the elbow, a technique seen today in various martial arts.