When lifting a heavy box, you should bend your knees and engage your whole body to support the weight, rather than relying solely on your arms.
This concept is foundational to “spiraling” in Wing Chun, where efficient movement originates from the larger muscles of the body rather than the smaller ones.
“Spiraling” refers to the coordinated rotation of the arms—including pronation (inward rotation) and supination (outward rotation)—while also incorporating the extension or stretching of the arm from the fingertips to the elbow and shoulder.
In Wing Chun forms, movement begins with the hands remaining relatively still, while the spiraling motion engages the back, torso, and hips.
The movement should always be initiated from the core, and a benchmark for good form is that the core moves first, even if only slightly, followed by the arms.