Let’s finish up the article that we started talking about here.
To recap, movement affects cells in these processes:
— transduction— movement of signals across the cell membrane (skin) via receptors. Then if those signals activate cytosolic mediators, then they trigger transcription factors which travel into the nucleus (brain) and…
— transcription— DNA gets unzipped and a gene is copied onto a messenger. Which travels out of the nucleus (brain). Then…
— translation— The messenger gets read and proteins are created. The proteins are then in turn used to make actions either inside the cell or are secreted out of the cell to have an action outside the cell.
A reminder of the different kinds of forces:
“[These forces] can either strengthen the [tissues] that bear the load or change the distribution of receptors to [divvy up] the load.” Which is how the cells respond to movement. Each cell type also responds differently to an individual force– a lung cell is going to do something different than a bone cell to the same force. They also respond differently to variety in the amount of force, length of time the force is applied and number of times a force is put on them.
“… forces regulate and influence biochemistry, genetic expression, tissue integrity in homeostasis, and developmental and repair processes. Many otherwise unrelated disease processes share abnormal mechanotrandsduction [force response], as the etiology or clinical presentation and molecules that mediate mechanotransduction present therapeutic targets for amelioration of these disease.” So if we can figure the root force problem in these diseases, we can figure out how to fix it!
A few examples….
The cells that line the entire cardiovascular system are constantly under shear forces from the blood flowing through the vessels. The shear isn’t constant; it goes up and down with your pulse rate. Alterations in the shear force has been shown to effects transcription in those cells, which in turn contributes to atherosclerosis or the hardening of vessels making for heart disease.
Lung cells are constantly adjusting to tension forces as we inhale and exhale. “At birth, the transition to breathing air creates changes in force distribution across lung tissue and results in the formation and maturation of aveolar [lung] structures.” Trouble with managing tensile forces is also a contributing factor to asthma, ventilator-induced lung injuries, idiopathic pulmonary fibrosis, and emphysema.
Most people are familiar with compressive forces in weight-bearing activities improving bone health and preventing osteoporosis. Distraction (a tension force) is used to start fracture repair in some cases.
Research is showing that shear forces build cartilage, while compressive forces break it down.
Tension is used by athletes everyday in build muscle. The article goes a step further saying that muscle cells can differentiate between chronic longitudinal tension vs. chronic function or resistive overload tension forces. In the first instance induced by stretching, the cells get longer. In the second induced by weight training, the cells hypertrophy or get bigger.
Tension on skin makes new skin cells grow. But too much tension can make bad scarring. So to combat that, compression forces are added to prevent hypertrophic scarring in burn cases.
Bottom line: we need more research in this area, so we can better understand our dosing of interventions. “… we do not have the answers we need to precisely load healing tissue with the exact frequency, duration, magnitude and types of loads to extra the optimal outcome.” We also don’t know at what point the healing process these forces are best applied or if that dose needs to change as the tissue goes through the healing process.
Go, go super researchers! Find us answers!