An exercise feedback system determines sensor data quality of an athletic garment based on bioimpedance data. The athletic garment includes sensors that can generate physiological data and bioimpedance data. An athlete wears the athletic garment while exercising. If the sensors have a stable contact with the skin of the athlete, the sensors generate high quality physiological data. However, if the sensors have unstable or no contact with the skin of the athlete, the sensors generate low quality physiological data. The exercise feedback system uses the magnitude and/or variance of the bioimpedance data to determine whether the physiological data is high or low quality. If the physiological data is high quality, the exercise feedback system may generate and provide feedback based on the physiological data for display to the athlete. The exercise feedback system may also use the bioimpedance data to identify defects in the garment during quality assurance tests.