By Pete Najarian, co-founder of OptionMonsterNEW YORK -- Even as the Russell 2000 led the major indices lower Thursday, upside options were active in its exchange-traded fund. OptionMonster's tracking systems detected a strong buying pattern in contracts on the small-cap iShares Russell 2000 Index ETF ( IWM). The Weekly 82 calls, which expire this afternoon, were particularly busy with more than 52,000 changing hands. The Weekly 81 and 83 calls traded heavily as well. Calls lock in the price that investors must pay to buy shares, so they can be highly leveraged to a rally. But the short-term options bought Thursday have only Friday's session to pop, or they will expire worthless. The fund fell 1.41% to close at $80.62 after trading as low as $80.17 in the afternoon. The broader market sold off Thursday as traders anticipated a bearish employment report later this morning, following an ADP labor report on Wednesday that was much worse than expected. Total volume in the name exceeded 640,000 contracts Thursday, almost twice the average amount. Najarian has no positions in IWM.