The 38th Sportsman No. 1 Competition (最強の男は誰だ！壮絶筋肉バトル!! スポーツマンNo.1決定戦 XXXVIII) will air on TBS on January 3rd, 2009 from 18:30 to 20:54. The show will be preceded by the Sportsman No. 1 Navi (スポーツマンＮＯ，１決定戦 ナビ) at 17:00 to 18:00.
Pic taken from here.
Some of the competitors (as compiled by various sources):
宮崎大輔 (Miyazaki Daisuke)
松永共広 (Matsunaga Tomohiro, Beijing 2008 silver medalist in wrestling)
シェーン・ビクトリーノ (Shane Victorino of the Philadelphia Phillies)
森本ひちょり (Morimoto Hichori, Nippon Ham Fighters baseball team)
三沢光晴 (Mitsuharu Misawa, NOAH Pro Wrestling)
玉田 圭司 (Tamada Keiji, soccer player)
秋山準 (Akiyama Jun, NOAH Pro Wrestling)
丸藤正道 (Marufuji Naomichi, NOAH Pro Wrestling)
イ・ジョンウク/이종욱 (Lee Jong-Wook of South Korea's Doosan Bears baseball team)
里見恒平 (Satomi Kouhei, American football)
池谷直樹 (Iketani Naoki, talento)
ワッキー (Wakky, comedian)
More names via Yahoo
佐々木 健介 (Sasaki Kensuke, pro wrestler)
福地寿樹 (Fukuchi Kazuki, Seibu Lions baseball team)
本田武史 (Honda Takeshi, figure skater)
興梠慎三 (Kouroki Shinzou, Kashima Antlers soccer team)
青木剛 (Aoki Takeshi, Kashima Antlers soccer team)
北川智規 (Kitagawa Tomoki, rugby)
竹内公輔 (Takeuchi Kousuke, AISIN Sea Horse basketball team)
Daisuke Miyazaki is the defending champion and would be trying to become the first three-time champion and the first back-to-back champion (his first attempt at a back-to-back was foiled by the American Monster, Paul ANTHONY Terek). Iketani Naoki is a former champion. Wakky is the defending Geinojin champion. There was no (that we know of) Geinojin Battle this year.