New ergonomic backpack lightens the load

An MBL (Marine Biological Laboratory) biomechanics expert has invented an ergonomic backpack that uses rubber bands to reduce the effects of heavy loads on shoulders and joints and permits wearers to run more comfortably with heavy loads.

The backpack's design, which suspends loads using bungee cords, reduces the energetic cost of carrying weight such that users can carry 12 more pounds in the suspended backpack than in a traditional backpack. The suspended backpack could reduce the risk of orthopedic and muscular injuries to children, emergency workers, and others who use backpacks to carry loads.

Lawrence C. Rome, a University of Pennsylvania biology professor and a Whitman Investigator at the MBL, where he spends his summers studying muscle in fish and frogs, and two colleagues, describe the design of and the mechanics behind the Suspended-Load Ergonomic Backpack in the December 21 issue of the journal Nature.

With traditional backpacks, the mass of the backpack, which is typically attached tightly to the body, must undergo the same vertical displacement as the hip, which moves up and down 5 to 7 centimeters during walking. As a result, the peak forces exerted on the body by the load can be twice as high when walking, and three times as high when running, as when the backpack is not moving, exerting extreme forces on the wearer's shoulders and joints.

By using stretchy bungee cords, Rome's ergonomic backpack suspends the load and allows it to stay at a nearly constant height from the ground while the wearer walks or runs. This reduces the vertical displacement of the load and the resulting dynamic forces exerted on the body by a remarkable 82 to 86 percent. The reduction in dynamic force is easily felt, says Rome, and has practical consequences. "An immediate application would be to use it in backpacks carried by schoolchildren, a well known cause of musculoskeletal injury and recognized international public health problem."

Perhaps the most remarkable aspect of the backpack is that it permits wearers to run far more comfortably with heavy loads. "Being able to move at relatively high speeds is crucial for many professions (firemen, first responders, disaster relief workers, and police) as well as in some athletic competitions and recreation," says Rome. "If you have ever tried to run with a heavy backpack, it is almost impossible because of the large shocks to your knees and ankles. What is striking about our ergonomic backpack is that one can feel the 86 percent reduction in force with each and every step."

Rome and his colleagues also found that the suspended backpack's reduction in forces exerted on the body reduced the metabolic cost of carrying a load, allowing a substantially heavier load to be carried. The lower metabolic rate allows the wearer to carry 60 pounds in the ergonomic backpack for the same energetic cost as 48 pounds in a normal backpack. "The reason for this reduction in metabolic rate is that the suspended backpack reduces the accelerative forces during the more energetically expensive phase of walking, which is when both legs are simultaneously in contact with the ground and performing mechanical work against each other," says Rome.

Rome has formed a company called Lightning Packs LLC to further develop and commercialize the backpack. He and his colleagues will be focusing on reducing the backpack's weight and making a smaller daypack version.

Source: Marine Biological Laboratory

Related stories:

Accelerometer backpacks aid study of gliding behavior in the 'flying' lemur
The "flying" lemur of Malaysia is the champion of all gliding mammals, able to drop from the forest canopy, glide more than the length of two football fields, execute 90-degree turns and then alight gently on a tree trunk.
A new twist on power walking
MBL scientist invents backpack that empowers wearers to generate their own electricity

In an unprecedented breakthrough in the development of portable and renewable human-driven energy sources, an MBL (Marine Biological Laboratory) biomechanics expert who studies how muscle moves skeletons in fish and frogs has invented a backpack that gives new meaning to the term power walking.
GM crops protect neighbors from pests
A study in northern China indicates that genetically modified cotton, altered to express the insecticide, Bt, not only reduces pest populations among those crops, but also reduces pests among other nearby crops that have not been modified with Bt. These findings could offer promising new ideas for controlling pests and maximizing crop yields in the future. The report will be published by the journal Science on Friday, 19 September.
Back to School Reminder: Kids Should Go for Safety, Not Style
(PhysOrg.com) -- School children across the world may speak different languages but there is one experience an estimated 90 percent of all students share: wearing a backpack. Researchers from the University of San Diego, California School of Medicine say those students also share a common problem: low back pain due to overloaded backpacks.
Musical Robot Tags Along as your Serenading Sidekick
If you ever thought it would be cool to be serenaded by a robot, you might get a kick out of the new A.M.P. Bot. Developed by Hasbro Tiger Electronics, the 2.5-foot-tall humanoid rolls around on a Segway-type platform, blasting your favorite tunes, all the while following you around your house like a younger sibling with its remote control technology.
Backpack straps can decrease blood flow in the shoulder and arm
More than 92 percent of the children in the U.S. carry backpacks. Typically the backpacks are loaded with almost one-fourth of the child’s body weight (22 percent) and worn with only one strap. Last year, a team of physician researchers examined the effect heavy-loaded backpack straps can have on children. They found the straps can significantly increase pressure when the load is ten percent or more. They also found that strap pressures with loads as small as ten percent of bodyweight can obstruct localized blood flow and contribute to shoulder fatigue.
Antisocial conduct and decision making about aggressive behavior influence each other in teens
A new study challenges the idea that antisocial behavior is relatively unchangeable during the teenage years. The study, published in the March/April 2008 issue of the journal Child Development, found that decision making and behavior among adolescents are related across time, and that efforts to help may be more effective if they address how adolescents make decisions about acting aggressively.
Godwits readying for Alaska migration
A new cohort of godwits is preparing to leave Miranda, the second wave to have their epic 11,000km journey to and from Alaska monitored by satellite technology. Dr Phil Battley, of the University’s Ecology Group, is leading the New Zealand leg of the worldwide project run by the US Geological Survey.

News discussion:

General Science news