Better trained in wrestling with complex religious texts than in martial arts, the ultra-Orthodox Jewish youths drop to the floor to give their combat instructor a dozen push-ups.
Black skullcaps slip off their heads and a pair of glasses goes flying across the room as the khaki-clad trainer barks out: “I will kick your ass if you do not keep time.”
The 15 young men have chosen to go against the norm of their reclusive community. They are training for military service, a two-to-three-year obligation that binds most Israelis, but from which the ultra-Orthodox, or Haredim, are mostly exempt.
Not 10 minutes drive away, posters in Jerusalem’s ultra-Orthodox neighbourhoods scorn Haredi men who choose to serve in the army and quote rabbis who rule against the practice they fear will lead their youth away from piety and into bad ways.
But there are those who swim against the stream, many of them seeking a way out of financial hardship. According to the Israeli military, there are increasing numbers of ultra-Orthodox soldiers in its ranks today.
“Army is an essential stage for the rest of my life, you go through a lot there, you leave there ready for life,” said Michael Iluz, one of the youths taking part in the private programme meant to prepare him for military life.
From childhood, ultra-Orthodox men are schooled almost exclusively in religious studies, many at adulthood choosing full-time study over working. Their traditionally large families rely on state benefits, stipends and their wives’ wages.
As such, Haredim, who make up about 10 percent of Israel’s eight million population, are viewed by many in Israel as an economic burden.
Adhering to a strict religious lifestyle, Haredim - Hebrew for “those who fear God” - mostly live in their own towns and neighbourhoods, keep to their own schools and shun secular culture. Men wear traditional black garb and women cover up.
But there are signs of a growing, dispersed movement driving change inside the cloistered, and also poor, community.