A blood flow restriction garment controller, a blood flow restriction garment system, a method of controlling a blood flow restriction garment, a method of controlling an electronic device and computer software. The blood flow restriction garment controller comprising: a pump arranged to increase a pressure in an air bladder of a blood flow restriction garment; an air pressure sensor arranged to measure a pressure of the air bladder and provide a signal indicative of the measured pressure; a valve arranged to control the pressure of the air bladder, wherein the valve has at least two operating states, wherein the operating states comprise an open state and a closed state; at least one or more of an inertial measurement unit, an accelerometer, a gyroscope, arranged to determine movement of the blood flow restriction garment controller and provide a signal indicative of the determined movement; processing means for providing a signal to control the valve by selecting one of the at least two operating states, wherein the signal to control the valve is based on at least one of the signal indicative of the measured pressure and the signal indicative of the determined movement.

A sportswear garment comprising means for adjustably compressing at least one major vein in a user's limb such that blood flow through the at least one major vein is restricted.