To the extent that Lochner had an impact on the trade union movement, it would have been negative.

This was not really a case about unions.  It was, instead, a case about what kinds of regulations the government could make with regard to workers and employers.  In it, the Court struck down a state law that limited how many hours bakers could work.  It did not say that unions couldn't make such rules if they could get employers to agree.  

So this case did not directly limit what unions could do.  If you need to make an argument about it and unions, you should say that it generally gave businesses more clout because the government could not regulate them.  This meant that unions and the labor movement in general could not push the government to make laws requiring things that the unions wanted (like better hours).