The worst effect a current of 159mA is likely to have on the human body is _____.

A current of 159 mA passing through the human body is significant and can lead to painful shock along with potential loss of muscular control. When the body is subjected to currents in this range, it can disrupt normal physiological functions, leading to intense sensations of pain. This current level may also interfere with the body's neuromuscular control, making it difficult for an individual to respond or move effectively.

While lesser currents may cause only minor discomfort or a painful shock without significant loss of control, 159 mA is above the threshold where more severe effects can manifest. It poses a serious risk not only of causing pain but also of muscular contractions, which can impair voluntary control over muscle movement.

In terms of the potential for severe burns or cardiac arrest, these outcomes typically require either higher currents or different circumstances, such as prolonged exposure or specific pathways through the body. Thus, while the possibility of burns or cardiac complications exists, the immediate and most common result of exposure to 159 mA is indeed the painful shock and associated loss of muscular control.