The mechanical side of biology

The field of biomechanics covers a wide range of topics, from the strength of a cytoplasmic structure to the buoyancy of a blue whale. In essence, biomechanics uses the principles of physics to unravel how an organism, or just a part of one, functions, how it is constructed and how its performance and evolutionary potential might be limited. A good deal of biomechanical research examines locomotion — flying, jumping, running, swimming, walking, wiggling, whatever — and it’s worth taking a stroll around the web to find out more. Being walkers more than swimmers, and certainly more than fliers, humans tend to look very carefully at gait, which is the way that a terrestrial animal moves. Horses give us a good look at different gaits, such as walking and trotting. To get familiar with gait, stop by the Clinical Gait Analysis site. Among other things, this site posts a case of the week, which includes a description and a movie of a patient with a walking problem, including measurements of various flexions and extensions. For visitors who want to test their knowledge of gait, the site offers Teach-in ’98, which leads to a series of experiments along with data and questions. Lots of animals get around without taking many, if any, steps. For example, many insects swim, especially during early developmental stages, and it seems that swimming somehow spawned flight. At Jim Marden’s homepage you can learn about the stonefly, a primitive insect that moves in a way that looks like something between swimming and flying. In some cases, a stonefly holds up its wings like sails and skims across the water like a wind surfer. On the other hand, this insect can also flap its wings to use them like a propeller to power its skimming. Marden, an insect-flight expert, has posted QuickTime movies of this surface-skimming on his web site. Fortunately, they are short segments that download quickly. To find out more about the physics of flight, take a tour of the Vertebrate Flight Exhibit at the web site of the University of California Museum of Paleontology. It goes over the basic principles of flight — including drag, lift and thrust — and explains different kinds of flying, such as gliding or parachuting. The field of biomechanics covers many things beyond locomotion. For instance, a biomechanic might measure the strength of any biological material, from a molecule to a molar. Such measurements often lead to medical applications, such as those described at the site of The Berkeley Orthopaedic Biomechanics Laboratory. Visitors can explore a variety of on-going research projects at this site, including one called Prosthesis Design. This project uses finite-element models of hip implants to test how a specific prosthetic device will perform. Then, the design of a device can be changed and retested to look for ways to make it perform better or last longer under the repeated stress created by the rhythm of walking. Other areas of biomechanics seek out even more stress by studying sports. The Sportscience site posts articles about the science of all kinds of sport, and includes a special section on training and technology, where you can learn about the benefits of altitude training for runners and aerodynamic wheels for cyclists. Other sites provide more information on specific athletic events. Baseball, for instance, might look different to you after a tour of the page called the Biomechanics Of Baseball Pitching. Here, a sequence of frames shows a player’s skeleton during a windup and pitch. Colored arrows show the arising forces. If you can wait a few minutes for a download, you can watch an MPEG movie of this pitching skeleton. The skeleton winds up, rears back, and fires the ball home. All the while, arrows show the changing forces during the pitch. Several biomechanics societies have web sites, including the American Society of Biomechanics, the European Society of Biomechanics and the International Society of Biomechanics. A tour of the biomechanical sites on the web should give anyone the chance to take a walk on biology’s mechanical side.