render :json => {
      page: page,
      per_page: @user_tracks.per_page,
      total_pages: @user_tracks.total_pages,

      user_tracks: @user_tracks.map do |track|
        { id: track.id, name: track.name, player: track.player, distance: track.distance,
          best_time: track.best_time, likes: track.likes, created_at: track.created_at }
       end
    }