Shortly after Thanksgiving, Deborah Schneider decided to join a gym. It was time to get in better shape, she said. “I went because I wanted to strengthen my core,” said Schneider, 74. “I have a bad back and I need stronger muscle strength.” She visited Jersey Strong in Manalapan in late November, and after hearing the sales pitch, she said she was sold. “They said they had a nutritionist,” she said. “I was told there would always be a person on the floor who would provide help if I needed it — just look for the black shirts with Jersey Strong in green lettering.” Schneider said she was excited…