If you wanted to explore Mars, what kind of bridge would you take with you? How would you build the bridges? How would you make sure the bridge will work for a variety of terrain? Since you must carry the bridge all the way to Mars, it must be small, light, and highly reliable. Researchers from the Technical University of Munich have a wonderful answer: a tensegrity truss.
Tensegrity masts are also used for deploying a variety of instrumentation and solar panels on orbiting satellites. The tensile network is bearing the weight of the structure; by increasing the tension, the mast deploys. It’s a remarkably material-efficient way to “reach out” with structure. Tensegrity masts can even teach us how to reach out more effectively with our arms and legs.
Our arms can be thought of as tensegrity masts: bridges to reach out from our body to the world. Like the Mars Bridge, our masts are deployed and supported with lines of tension. The Deep Front and Deep Back Arm Lines are used to effortlessly engage our arm-masts. These lines are fully described in Thomas Myers’s book Anatomy Trains. Myers provides a 20-page summary of the book here.
Are all the muscles tensioned in our arm? No. Most of the superficial muscles are relaxed; relaxing them cues the deep muscles to engage.
There’s one hidden detail about the Mars Bridge: before deployment starts, its base is connected to the ground. This allows the “reaching” to work smoothly and gracefully — with no danger of the bridge toppling into the ravine. To reach and carry loads gracefully, the mast is simultaneously pulling inwards as it reaches outwards.
For our arms to work this way, the shoulder is engaged or pulled back over the shoulder girdle. Again, this pulling happens with deep muscles; it’s actually a very relaxed engagement. Body/mind workers have a variety of terms for this movement: integrated shoulder, scapular stability, etc. Body/mind master instructor Eric Franklin has a wonderful book on this topic: Relax Your Back: Liberate Your Shoulders.
Using your arm like a tensegrity mast allows it to work with far less stress. Powerfully connecting your shoulder to the lines of tension in your torso will allow you use more muscles to support the weight of your arm. This one simple movement may dramatically lessen upper back stress and pain. If you practice it, you may even notice that your arms can float upwards with very little effort. I practice this sometimes when stopped at a traffic light.
Thanks to Landolf at the Tensegrity Structures blog for finding the wonderful “Bridging Mars” video.