The Constrictor is a device that causes involuntary muscle contraction to the point of breaking bones.
Howard Stark created the Constrictor for back massage; the invention became too dangerous for public usage. Leet Brannis stole the Constrictor, among other inventions, and stored them aboard The Heartbreak with Jerome Zandow until it could be sold.
Peggy Carter and Edwin Jarvis found the device and other inventions when they entered the boat. Jarvis explained the origin of the Constrictor to her when she asked. Later, Zandow attempted to kill Jarvis before Carter only to be paralyzed by Carter who used the Constrictor.
- "I need a doc; my arm is broke."
- ―Jerome Zandow
Opposite muscle groups cannot contract simultaneously; biceps do not contract when triceps do. The Constrictor causes opposite muscle groups to contract simultaneously; this causes the bone associated with those muscle groups to break from the strain.