Johnston fathered a child with Bristol, the 18-year-old daughter of Sarah Palin, the former Republican vice presidential candidate and former Alaska governor.
To get ready for his close-up, Johnston is training three hours a day, six nights a week at an Anchorage gym with a local body builder, Marvin Jones, a former Mr. Alaska competitor.
Playgirl spokesman Vincent Stevens could not immediately be reached for comment.
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