Pedaling resistance, or tension control, can be manually adjusted to set how hard it is to pedal. Adjust this by turning the dial in front of you while seated on the bike. Resistance ranges from 1 (lowest difficulty) to 8 (highest difficulty).
VirZOOM games can sense your resistance settings, but won't change your resistance for you. You may find you get need to pedal harder to maintain your virtual speed when going uphill, but the resistance on the bike itself will remain unchanged.