This post is in partnership with Time. The article below was originally published at Time.com.
By Dan Kedmey, TIME
Apple (AAPL) has reportedly scaled back ambitions to embed cutting edge health sensors in its smart watch, as stray arm hairs and dry skin confounded the readings for some wearers.
Insiders at the company told the Wall Street Journal that the company shelved a sensor that would have monitored heart rates using electrocardiogram technology. The sensor reportedly produced less than reliable readings when placed against hairy or dry skin, or if the wearer strapped it too tightly against the wrist. Engineers also struggled to get a reliable reading of stress levels by gauging sweat on the skin.
Apple Watch is slated for an April release, marking the first time that Apple will attempt to create an entirely new category of electronic devices since the 2010 release of the iPad. The device maker has reportedly ordered upwards of 5 to 6 million units in anticipation of the release date, according to parts suppliers in Asia.