People do tend to think that once rigor mortis sets in that the body remains rigid.
Only for a period of time:
After death, respiration in organisms ceases, depleting the corpse of oxygen used in the making of adenosine triphosphate (ATP). When oxygen is no longer present the body may continue to produce ATP via anaerobic glycolysis. When the body’s glycogen is depleted, the ATP concentration diminishes and the body enters rigor mortis.[2] ATP is required to cause separation of the cross-bridges during relaxation.[3] Additionally, calcium enters the cytosol after death. Calcium is released into the cytosol due to the deterioration of the sarcoplasmic reticulum. Also, additional calcium enters the cytosol from the extracellular fluid due to the breakdown of the sarcolemma. The calcium activates the formation of myosin-actin cross-bridging. Once calcium is introduced into the cytosol, it binds to the troponin of thin filaments, which causes the troponin-tropomyosin complex to change shape and allow the myosin heads to bind to the active sites of actin proteins.[1] In rigor mortis myosin heads continue binding with the active sites of actin proteins via adenosine diphosphate (ADP) and the muscle is unable to relax until further enzyme activity degrades the complex.[3]
Normal relaxation would occur by replacing ADP with ATP, which would destabilize the myosin-actin bond and break the cross-bridge.[1] However, as it is absent, there must be a breakdown of muscle tissue by enzymes (endogenous or bacterial) during decomposition. As part of the process of decomposition, the myosin heads are degraded by the enzymes, allowing the muscle contraction to release and the body to relax.[4][5] Decomposition of the myofilaments occurs forty-eight to sixty hours after the peak of rigor mortis which occurs approximately twelve hours after death.[1]
Source: Wikipedia
Those people dont rise from the dead. God could have decided to elongate his arms And put the hands over the groin so we wouldn’t be looking at the penis of the son of God 2000 years later