Your Brain is Making You Weak
athletics fitness nervous system neuromuscular Pavel Tsatsouline power to the people strength weightlifting
The interesting thing is, these effects can be overcome. By treating even light weights as if they are heavy (apply serious concentration and tension as if you were lifting a heavy load) you can trick your nervous system into ignoring its own feedback and just going all out all the time. If, instead of letting gravity lower a weight, you actively pull it down with the antagonist muscles, the brain will allow a stronger agonist movement, since it is aware of the antagonist activation. Obviously, you don't want to completely override these safety mechanisms, but you can push the margins a lot. Going from 30% tendon load to 50% is a pretty big jump in strength while leaving a lot of room for safety. And that's all without any physiological change in the muscle itself, only in nervous activation. That would be the equivalent of going from lifting 100lbs to over 150lbs.
An interesting correlation to this is what happens when you do override the safety margins too much. I heard about a gymnast holding an iron cross to the point that his biceps tore the tendon off the bone. The brain was allowing it to activate beyond what the tendon could bear. On a more optimistic note, this effect is probably what enables mothers to hoist cars off their infants; the nervous system perceives an extreme situation and removes all safety margins, allowing for ridiculous increases in strength with no prior conditioning.
This is an effect caused by the proximity or overlap of neurons in the motor cortex (I think). Basically what it does is increase the strength of agonist muscles acting against a load simply by activating non-related muscles. For example, if you are trying to do a pullup, you will actually be able to pull more weight if you squeeze your glutes, tighten your abs, and lock out your legs. These muscles have little to no relationship to the actual movement, but because they are such large motor groups, they have a lot of associated nerve activation, and by activating their nerves, you get a lot of nervous activation overflow into the muscles that are actually working (in this case, lats and biceps). Another example is making a fist. Your left fist will be much stronger if you actively squeeze your right hand into a fist at the same time. Again, this is a neural phenomenon, not a muscular one.
Another related effect is abdominal pressurization. We're often told not to hold our breath when weightlifting, despite the fact that it is instinctual. I'm not making medical recommendations here, but I do know that holding one's breath dramatically increases possible strength output. There are two reasons for this. One is that abdominal pressure triggers certain nerves that allow for greater muscle tension and loading. These nerves are there to check that there is sufficient pressure in the abdomen to stabilize an extra load. If you let out your breath, they will inhibit muscle action in order to protect the spine, which is no longer braced by the extra air pressure, causing you to drop the weight. The second effect is the structural impact of the held air; simply by inhaling and holding a breath, you provide extra bracing for the trunk, which allows peripheral muscles to push against a more stabler platform. It's the difference between bouncing a flat basketball and a taut one.
The next time you try for a big lift, or even just a pushup, set up first by taking a breath, tightening your abs, squeezing your buttcheeks like you're holding a coin, and lock out your knees by tightening your thighs and hamstrings. Also tighten your back and pull your shoulders into the sockets hard. You will immediately see an increase in your strength.
Your brain is also paying attention to your peripheral limbs to determine appropriate muscular tension. It will check pressure in the hands and feet as a means of determining how hard to allow the prime movers to pull. When doing heavy deadlifts, for example, a weak grip will cause your brain to inhibit hamstring and glute action. Perceiving an unstable grip, the brain is wary about allowing full tension, either because it doesn't think the load can successfully be moved, or in order to protect the back. This is why artificially increasing the security of the grip (either through alternating grip, hook grip, or straps) can improve strength output and increase the lift.
Similarly, the brain utilizes pressure sensors in the feet to determine appropriate tension to hold a load. This is why it is a bad idea to wear running shoes when weightlifting. They interfere with the foot's natural perception of pressure, and also delay its reception, which can cause the brain to mistime muscle tension in supporting muscles like the back and core during heavy lifting.
What does all this mean? A couple things. First, you're already way stronger than you think. Your muscles are probably currently capable of some pretty crazy feats of strength and power, if only your brain would get out of the way. It also means that you don't need to be especially large to be amazingly strong. Muscle size can be associated with strength, but often a smaller muscle with better neural activation is going to be stronger. Because this kind of strength is based on proper proprioception and body awareness, it contributes to better overall stability, balance, and is probably more useful for preventing injury.
If you're interested in learning more about this, I recommend any of Pavel Tsatsouline's ebooks (Power to the People being the main one). Neurological factors as the basis for amazing feats of strength also play a big part in kettlebell conditioning, and of course gymnastics, where small people do some crazy stuff.
Image source: TangYauHoong on Flickr