Wednesday, May 25, 2011

Hips Take Walking in Stride, Ankles Put Best Foot Forward in Run

In a first-of-its-kind study comparing human walking and running motions -- and whether the hips, knees or ankles are the most important power sources for these motions -- researchers at North Carolina State University show that the hips generate more of the power when people walk, but the ankles generate more of the power when humans run. Knees provide approximately one-fifth or less of walking or running power.
The research could help inform the best ways of building assistive or prosthetic devices for humans, or constructing next-generation robotics, say NC State biomedical engineers Drs. Dominic Farris and Gregory Sawicki. The co-authors of a study on the mechanics of walking and running in the journal Interface, a Royal Society scientific journal, Sawicki and Farris are part of NC State's Human PoWeR (Physiology of Wearable Robotics) Lab.
A long history of previous studies have focused on the biomechanics of human locomotion from a whole-body or individual limbs perspective. But this study is the first to zoom in on the mechanical power generated by specific lower-limb joints in a single comprehensive study of walking and running across a range of speeds, Sawicki says.
The study shows that, overall, hips generate more power when people walk. That is, until humans get to the point at which they're speed walking -- walking so fast that it feels more comfortable to run -- at 2 meters per second. Hips generate 44 percent of the power when people walk at a rate of 2 meters per second, with ankles contributing 39 percent of the power.
When people start running at this 2-meter-per-second rate, the ankles really kick in, providing 47 percent of the power compared to 32 percent for the hips. Ankles continue to provide the most power of the three lower limb joints as running speeds increase, although the hips begin closing the distance at faster speeds.
"There seems to be a tradeoff in power generation from hips to ankles as you make the transition from walking to running," Sawicki says.
Both researchers are interested in how the study can help people who need assistance walking and running. Knowing which part of the lower limbs provide more power during the different activities can help engineers figure out how, depending on the person's speed and gait, mechanical power needs to be distributed.
"For example, assistive devices such as an exoskeleton or prosthesis may have motors near both the hip and ankle. If a person will be walking and then running, you'd need to redistribute energy from the hip to the ankle when the person makes that transition," Farris says.
Ten people walked and ran at various speeds on a specially designed treadmill in the study; a number of cameras captured their gait by tracking reflective markers attached to various parts of the participants' lower limbs while the treadmill captured data from the applied force.
The study examined walking and running on level ground in order to gauge the differences brought about by increased speed; walking and running on inclined ground is fundamentally different than walking and running on flat ground, the researchers say, and would likely skew the power generation results toward the hips and knees.
Source: Daily science webs

Wednesday, May 11, 2011

Mitochondria: Body’s Power Stations Can Affect Aging

Mitochondria are the body's energy producers, the power stations inside our cells. Researchers at the University of Gothenburg, Sweden, have now identified a group of mitochondrial proteins, the absence of which allows other protein groups to stabilise the genome. This could delay the onset of age-related diseases and increase lifespan.
Some theories of human aging suggest that the power generators of the cell, the mitochondria, play a part in the process. In addition to supplying us with energy in a usable form, mitochondria also produce harmful by-products -- reactive oxyradicals that attack and damage various cell components. Eventually these injuries become too much for the cell to cope with, and it loses its capacity to maintain important functions, so the organism starts to age. That's the theory anyway. Oddly enough, several studies have shown that certain mitochondrial dysfunctions can actually delay aging, at least in fungi, worms and flies. The underlying mechanisms have yet to be determined.
In a study from the Department of Cell and Molecular Biology at the University of Gothenburg, published in the journal Molecular Cell, a research team has now identified a group of mitochondrial proteins that are involved in this type of aging regulation. The researchers found that a group of proteins called MTC proteins, which are normally needed for mitochondrial protein synthesis, also have other functions that influence genome stability and the cell's capacity to remove damaged and harmful proteins.
"When a certain MTC protein is lacking in the cell, e.g. because of a mutation in the corresponding gene, the other MTC proteins appear to adopt a new function. They then gain increased significance for the stabilisation of the genome and for combating protein damage, which leads to increased lifespan," says Thomas Nyström of the Department of Cell and Molecular Biology.
He adds, "These studies also show that this MTC-dependent regulation of the rate of aging uses the same signalling pathways that are activated in calorie restriction -- something that extends the lifespan of many different organisms, including yeasts, mice and primates. Some of the MTC proteins identified in this study can also be found in the human cell, raising the obvious question of whether they play a similar role in the regulation of our own aging processes. It is possible that modulating the activity of the MTC proteins could enable us to improve the capacity of the cell to delay the onset of age-related diseases. These include diseases related to instability of the genome, such as cancer, as well as those related to harmful proteins, such as Alzheimer's disease and Parkinson's disease. At the moment this is only speculation, and the precise mechanism underlying the role of the MTC proteins in the aging process is a fascinating question that remains to be answered."