The sight of wide receivers Keith Kirkwood and Shaq Davis leaving practice early this week because of heat-related symptoms was nothing new for the New Orleans Saints, with the hot and humid Louisiana weather a test for even the best-conditioned athletes. The unrelenting, record-breaking heat across the nation this year has made the opening of training camps even more challenging than usual, however, not only for the Saints but teams throughout the NFL. Safety has been a centerpiece of the preseason since Minnesota offensive tackle Korey Stringer died on Aug. 1, 2001, after slipping and falling the previous day after a Vikings training camp practice.