A portable electronic device with an IrDA transmitter LED is used to transmit both IrDA signals and remote control infrared signals. Each data packet is directed to a predetermined user and includes transmission power control information for said user. A slope of the elliptical path can also be adjusted by driving the stride adjusting mechanisms, so as to provide climbing exercise effects. The bladder contains air at slightly above ambient pressure and can be formed by thermoforming or by welding two sheets of resilient, flexible material together.