There is no minimum under the law. You can compel your employees to come in for .01 hours as a term of continued employment. It may make them mad and result in
turnover and things like that, but it's perfectly legal. Minimum shift requirements are often seen in CBAs but they're not part of any applicable federal or Texas state law, assuming you are a private employer. If the
training is ocurring at all the hourly employees regular work site, or in the same city as their regular work site with only a single location to go to for the
training, there will be no
travel time concerns.