I totally know this is not the best question for here because it goes beyond just fitness-y stuff and into all of that science stuff more so, but let's consider I am asking this is a good-hearted, simple way:

Middle-aged woman; doesn't exercise really; has three kids; probably couldn't lift even 200 lbs. on the deadlift on any normal day, even with full force.

One day, her child is trapped under the back, rear-bumper of a small car, and she somehow lifts it enough to save the baby. Even disregarding the fact that the car is small, most U.S. cars that are small still weigh over 1,800 lbs. most of the time.

With that in mind, it would most certainly take over 200 lbs. of force to lift one rear-side of a bumper. Why can she do this?

Why can some people gain this superhuman strength, and what can simply explain it for one like me who is interested in the power world more?

Also, if this superhuman strength can just appear and help a person lift something they couldn't normally lift, couldn't this superhuman strength be trained to be applied to more common use, possibly?

  • Adrenaline, (the fight or flight response), and the basal urge to obtain a result without considering the consequences on the body. It's the same reason people perform astonishing feats when their lives are threatened. Can one train for it? Possible but highly improbable for most people (no reason to) . Jan 7, 2015 at 3:13
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    Is there any evidence that this has actually happened?
    – half-pass
    Jan 9, 2015 at 0:24
  • News reports, stories, etc. I believe anecdotes exist very widely as well as eyewitnesses. Jan 13, 2015 at 2:05
  • 2
    This might be a good fit on skeptics stackexchange. Jan 15, 2015 at 21:11

2 Answers 2


The answer is a phenomena called Tetanic contraction:

A tetanic contraction (also called tetanized state or tetanus) occurs when a motor unit has been maximally stimulated by its motor neuron. This occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch. If stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches. If stimuli are delivered at high frequency the twitches will overlap resulting in tetanic contraction. When tetanized, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction.

Contrary to how we think, muscular movements aren't analogue but based on discrete nerve signals. Normally these signals are spaces apart, however it is possible under extreme for the body to rapidly fire these signals increasing the force of contraction. However, the downside is that this drastically increases the risk of skeleto-muscular damage.

enter image description here

As described here:

  • a. successive twitches;
  • b. summation, in which three stimuli are applied before relaxation is completed. This involves recruitment of more muscle cells to make the contractions more powerful;
  • c. incomplete tetanus eventually leading to complete tetanic contraction after 8 stimuli are applied.
  • 3
    +1. Overall, good answer. But the graphs should be accompanied by an interpretation, for example, explaining what real life circumstances to which each one corresponds, IMHO.
    – Tyler
    Jan 7, 2015 at 4:25
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    But not everyone can produce this. Some people have had their lives in danger and failed to do anything "extreme" enough to survive in a given set of circumstances. Jan 8, 2015 at 21:40
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    The tetanic contraction is the result of, and not the reason for "superhuman strength". Jan 8, 2015 at 22:16
  • Then what's the reason? Jan 13, 2015 at 2:06

Cortical excitation and disinhibition in the face of danger are what enables supranormal strength.

  • One effect is tetanic contraction due to an increased central drive (under the effects adrenaline and noradrenaline among others). That is, the neurons of the primary motor cortex fire in rapid succession
  • Another one is inhibition of the Golgi tendon organs (GTO), which under normal conditions cause reflex relaxation of the agonist when there is excessive tension across the muscle and its tendon. Again, this effect comes about by cortical disinhibition; the reflex arc, through which the effects of the GTO are mediated, is inhibited by neurons coming down through the spinal cord
  • The reflex arc that is mediated by the muscle spindle is excited by the same afferents that disinhibit the GTO arc. Normally the muscle spindle increases force to prevent excessive stretching of the muscle (the opposite of the GTO); due to excitation, the force is further increased. This is also the reason why motions involving stretch-shortening tend to be more forcefull; the effect of the stretch-shortening cycle is replicated without a previous eccentric contraction through central excitation

To answer your last question. Yes, it can be trained. Although not to that extent. To sum up the research, it seems that the higher the tension in your muscles and tendons when you exercise, the more the function of the GTO is inhibited, and the more the muscle spindle responds to stretching. Weight training has this effect. Power lifting and sprinting more so. Plyometrics seems to be most effective at it.

  • By repeatedly exposing your muscle to what activates the GTO and the muscle spindle, you alter their functions. The more you do it, the stronger the effect.

Also, an interesting aspect of whole body vibration, the kind utilized in vibration training. It seems to have precisely those effects. I generally advise people (amateurs and recreational athletes) not to pay the ridiculously high prices for vibration training. But if you are a power athlete (football, sprint, weight lifting, even jumping in basketball and volleyball), it can give you quick increases in explosiveness and power. In my opinion the effects seem to be comparable to those of isometric training, which has been proven to yield the highest acute strength gains of all training modalities. What else, vibration and isometrics work by two different mechanisms, so their effect are most probably synergistic, but that is unrelated to your question, so I wont go into detail there.

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