Prosthetics

Mechanical contrivances adapted to reproduce the form, and as far as possible, the function, of a lost or absent member. The replacement of a missing body part by an artificial substitute is called prosthesis; the branch of surgery dealing with prosthesis is prosthetics.
History

Artificial limbs, in one form or other, have been in use from ancient times. In 1885 a specimen was discovered in a tomb at Capua, Italy, along with other relics dating from 300 BC. The celebrated artificial hand built in 1509 for the German knight Götz von Berlichingen (1480-1562), who was called Götz of the Iron Hand, weighed about 1.4 kg (3 lb) and had articulated fingers so constructed as to be able to grasp a sword or lance. The hand is in the Nuremberg Museum and is still in working order. Early in the 19th century a German prosthetist built a hand with fingers that could be flexed or extended without assistance and yet could still close to hold light objects, such as a pen, a handkerchief, or a hat. In 1851 a French prosthetist invented an artificial arm fitted with a wooden hand and attached to a leather socket that fitted the stump firmly. The fingers were half-closed, the thumb pivoted on a pin and could press firmly against the fingertips by a concealed, strong rubber band; the grasp of the thumb could be operated by a mechanism attached to the opposite shoulder. The same inventor devised a leg that reproduced a natural gait and lengthened the stride.
Development

Before World War I, wood was universally considered the best substance for making artificial legs. Prosthetic devices made of leather reinforced with metal bands tended to lose their shape and were therefore unsatisfactory. Finally, the use of an aluminum alloy called Duraluminum, and later of fiber materials, made possible the manufacture of an artificial limb that was both lightweight and strong. Synthetic polymers now being introduced provide a skinlike covering for some forms of prosthesis.

Only in recent years, as a result of the needs arising out of the two world wars, has the manufacture of prosthetic devices developed into a science. Artificial legs with joints at knee and ankle can simulate a natural gait. The arm presents many more difficulties to the maker than the leg, and intricate mechanical devices make the use of metal imperative. Artificial arms are fitted with elbow joints and wrists capable of rotation. With the aid of springs controlled by shoulder movements, the hand can be manipulated, assuring a positive grip. Hip joint prostheses can provide virtually normal mobility for persons with damaged hip joints (see Hip).
Application

To ensure maximum comfort for the wearer some prosthetic devices are now fitted immediately following amputation of the natural limb. A rigid plaster dressing is applied to the site, serving as a socket for the attachment of a temporary prosthetic device. More recently, use of a removable plaster dressing has reduced pain and infections while the prosthesis is being fitted. In certain severe cases permanent artificial arms are equipped with small battery-powered motors, which facilitate movement at the joints.

The design and development of prosthetic devices are coordinated by the Committee on Prosthetics Research and Development of the National Research Council. Special prosthetic training schools have been set up at several universities for the teaching of modern prosthetic concepts to physicians, surgeons, prosthetists, and physical and rehabilitation counselors. H.R.L.

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Heartbreak Hurts, Scientists Say

Most people know that rejection hurts. But new research from the University of California at Los Angeles (UCLA) suggests that rejection really does hurt.

According to the study, led by social psychologist Naomi Eisenberger, being dumped, excluded or abandoned by a loved one can register in the brain just like a punch in the stomach or a stubbed toe. The finding implies that terms such as “hurt feelings,” “emotional pain” and “broken heart” aren’t simply metaphors: they may have arisen from physical experience.

The researchers used a functional magnetic resonance imaging (fMRI) machine to monitor the brain activity of 13 college students as they played a computer game called “Cyberball.” In the game—which is “really the most boring game you can imagine,” according to study co-author Matt Lieberman—one player, controlled by a human, tosses a ball back and forth with two computer-controlled players. But, in the study, the student participants were led to believe that the two other players in the game were being controlled by fellow students—not by the computer.The students were asked to play three rounds of the game under the vigilant eye of the fMRI. But, when the first round began, they were told that due to “technical difficulties,” they couldn’t participate, and were asked to watch the other players play while the problem was being fixed. In the second round, the participants were able to play and the game proceeded normally. Then, in the last round, the game started off normally, but for the last three-quarters of it, the two computerized players “ignored” the human player and kept the ball to themselves—as the researchers had programmed them to do.
The ACC: An Isolation Alarm

Eisenberger and her team then compared the fMRI data from each of the three rounds, looking closely at activity in the anterior cingulate cortex (ACC), a brain region involved in responding to physical pain. They found that during the first and third rounds of Cyberball (those in which the participants couldn’t play for either part or all of the time), the participants experienced more ACC activity than they did during the second round.

The ACC has been shown to function as a “neural alarm system” for physical pain: it registers pain and decides whether an automatic response, such as pulling one’s hand away from an unexpectedly hot stove, is needed. But Eisenberger’s study suggests that a similar “ACC alarm” goes off when an individual feels isolated from others—when he or she can’t participate in a game, for example. And, the ACC appears to respond the same way to any kind of social exclusion, regardless of whether it’s someone else’s “fault,” as when one’s fellow players refuse to pass the ball, or the result of extenuating circumstances such as technical difficulties. “It seems that if you are being left out in any kind of way, you will see ACC activity,” Eisenberger explained in an email.From an evolutionary standpoint, it makes sense that humans would have evolved a neural mechanism to respond to social exclusion. “Going back 50,000 years, social distance from a group could lead to death and it still does for most infant mammals,” Lieberman said. “We may have evolved a sensitivity to anything that would indicate that we’re being excluded. This automatic alarm [in the ACC] may be a signal for us to reestablish social bonds before harm befalls us.” The researchers believe that this “social exclusion alarm” probably evolved out of our system for responding to pain, which had already been established, and that’s why the two “alarms” use some of the same mechanisms.
Why It Feels Good to Talk?

But the researchers also found that oddly enough, the human brain may be able to override this knee-jerk reaction to social exclusion simply by thinking about the isolating experience. They interviewed the students about how they felt during the last round when the other players ignored them. Some of the students complained of feeling “invisible” and “rejected.” “They came out of the scanner saying, ‘Did you see what they just did to me?'” said Eisenberger. But others suspected (correctly) that the researchers had staged the third round to see how they’d react to being ignored.

The fMRI data showed that students who reported feeling upset as a result of being excluded experienced the most activity in the ACC region, suggesting that the greater the intensity of one’s “hurt feelings,” the greater the activity in that part of the brain. Meanwhile, those students who thought the round had been staged had low ACC activity.Common sense suggests that the skeptics didn’t have much ACC activity because, having figured out that the researchers were up to something, they weren’t insulted when the other players ignored them. But this contradicts the study’s finding that the ACC is activated whenever one finds oneself isolated from a group, regardless of the reason. So, although some of the students concluded that their fellow players weren’t to blame, this doesn’t explain why their ACCs didn’t light up: they were still excluded from the game, so theoretically, their ACC alarm should have gone off.It’s possible that some of the skeptical students might have suspected that the other Cyberball players were computer-controlled. This might have diminished their ACC response because they didn’t think they were being excluded from a real, human community. However, when interviewed by the researchers, most of the skeptics indicated that they believed the other players were humans. Moreover, studies have shown that people can feel insulted even when they know they’re playing with a computer. “Even if you tell people that they are playing (the same Cyberball game) with a preset computer program and that the program is set to exclude them at a certain point in time,” Eisenberger said, “the person playing with the computer still feels badly after the game.”

To unravel this mystery, the researchers returned to the fMRIs, and discovered that the students who figured out the researchers’ scheme had low ACC activity, but unusually high activity in another part of the brain: the right ventral prefrontal cortex (RVPFC). The RVPFC is involved in a wide variety of tasks, such as problem-solving, thinking about emotions and exercising self-control. Eisenberger and her team concluded that the skeptical students spurred this portion of the brain into action by thinking about their situation, in an attempt to figure out why they were being ignored.The researchers then hypothesized that the increased RVPFC activity in the skeptics played a role in diminishing ACC activity. A correlation between high RVPFC activity and low ACC activity had been previously demonstrated in studies of physical pain. In rats, for example, “electrical stimulation of VPFCdiminishes pain behavior in response to painful stimulation,” according to the researchers. And “in humans, heightened RVPFC activation has been associated with improvement of pain symptoms.” Thus, in observing the same kind of interaction between the two brain regions in their experiment on social exclusion, Eisenberger and her team may have uncovered yet another similarity between the brain’s responses to physical and emotional pain.By linking the process of thinking about one’s emotions—as the skeptical students did—to a decrease in ACC activity, the researchers may have discovered why writing or talking about negative emotions helps to alleviate them. “Verbalizing distress may partially shut down areas of the brain that register distress,” Lieberman said. “The regulating abilities of the prefrontal cortex may be why therapy and expressing painful feelings in poems and diaries is therapeutic.” The study, published in the October 10, 2003 issue of the journal Science, is thought to be the first to examine feelings of rejection using an fMRI machine. “It’s fabulous that they brought social interactions into the [fMRI] magnet,” social psychologist Susan Fiske, of Princeton University in New Jersey, told ScienceNOW. Scientists hope that studies like this one will help us develop new therapies for people dealing with rejection and loss.

Iceman’s First Aid Kit Astonishes Medical World

A traveler from the past has revealed that the use of medications began several thousand years earlier than previously thought. The man’s 5,300-year-old, mummified body was found in a melting glacier in the Italian Alps in 1991. His possessions included clothing, shoes, tools and two pieces of birch fungus strung on leather thongs. Scientists first assumed that the fungi were tinder for starting a fire. But new evidence suggests that they were highly specific remedies for a chronic illness the man suffered from. This medicine kit predates the oldest-known Egyptian remedy by one or two thousand years.

The two walnut-sized balls he carried with him are the woody fruit of a birch tree fungus called Piptoporus betulinus. When eaten, the fungus induces strong, but short-lived diarrhea, and acts as an antibiotic. It contains oils that are toxic to intestinal parasites.

An autopsy of the man, named “Otzi” by researchers, revealed that his colon contained parasitic worms called Trichurus trichiura. This kind of worm causes diarrhea and acute stomach pains. It can also bring on a deficiency of iron in the blood called anemia. This might explain why Otzi’s muscles showed a low iron content. Professor Luigi Capasso of Italy’s National Archaeological Museum discovered that Otzi’s fingernails showed a stunted growth pattern suggestive of repeated bouts with the worms. Eating the fungus Otzi carried would have killed at least some of the intestinal parasites and purged his bowels of their eggs.

“The discovery suggests that the Iceman was aware of his intestinal parasites and fought them with measured doses of Piptoporus betulinus,” Capasso wrote in the British medical journal Lancet.

The fungus is not the only evidence that Otzi’s people may have had some system of folk medicine. He also bore many tattoos on his body. Instead of being decorative, most were over joints in the spine, and the knee and ankle, all of which showed clear signs of arthritis. “The Iceman might have used these tattoos as a form of localized therapy for muscle and joint pain,” Capasso suggested.

Previously, the oldest record of medication was an Egyptian papyrus prescribing a brew of chewed-up pomegranate bark and beer to treat a parasitic disease the Egyptians called “aaa.”

Acupuncture Gains Increasing Acceptance

Acupuncture is a 2,000-year old Chinese medical practice used to relieve pain, nausea and other symptoms associated with various ailments. It is also used to help fight drug addiction and to anesthetize patients for surgery. Although Western scientists do not understand how acupuncture works, the practice is gaining favor within the medical establishment in the United States. In March 1996, the U.S. Food and Drug Administration (FDA) classified acupuncture needles as medical devices. That new classification meant that health insurance companies would be more inclined to pay for acupuncture. In September 1996, researchers discussed some of their most recent efforts to understand how acupuncture works.

Traditional Chinese acupuncturists believe that a “life force” called Qi (pronounced chee) flows through the body. They teach that Qi flows along 12 major meridians, or channels, within the body. They think Qi helps regulate various bodily functions. They believe that obstructions to the flow of Qi, caused by injuries such as tissue damage, lead to illness and discomfort. There is no scientific evidence that Qi actually exists.

Acupuncturists insert acupuncture needles into the skin at numerous sites, called acupuncture points. The needles are about the thickness of a human hair and vary in length from one centimeter (0.5 inch) to about 7 centimeters (3 inches). Acupuncturists either twirl, vibrate or send electric current through the needles to release the obstructions.

Many people favor acupuncture over pain-killing drugs because they want to avoid the potential side effects of the drugs, such as stomach upset or addiction. In 1996, about 10,000 acupuncturists and 3,000 medical doctors were certified to perform acupuncture by either state or national licensing boards. An estimated 30 million people in the United States have undergone the therapy.

Although many patients claim acupuncture worked for them, scientists do not know for sure how it works, and many doctors remain skeptical about its effectiveness.

Medical Research

Acupuncture researchers have conducted many studies to learn if acupuncture is effective. Some scientists have criticized the studies for lacking good controls. Controls are patients who do not receive an experimental treatment. The effect of a treatment can be verified by comparing patients who receive the treatment with controls who do not receive a treatment. Controls are an important part of any scientific study. [See Sagan Recommends “Baloney Detection Kit”, October 1996; Be Skeptical of Statistics and Scientific Studies, March 1995]. Two recent acupuncture studies published in peer-reviewed journals did include controls.

Researchers Lixing Lao, Richard H. Wong and Brian M. Berman, of the School of Medicine in Baltimore, tested acupuncture’s ability to ease patients’ pain after tooth extraction. Nineteen patients received acupuncture at four acupuncture points. Twenty control patients received light taps with thin plastic tubes on the same acupuncture points. The patients did not know which procedure they received. All the patients reported the length of time they were free of pain after each treatment.

The acupuncture patients lasted an average of 173 minutes without pain after each treatment. The control patients reported an average of 93 minutes of pain-free time after each treatment. The acupuncture patients mentioned no negative side effects. The researchers reported their results in the April 1995 issue of the journal Oral Surgery Oral Medicine Oral Pathology.

The same researchers conducted a second experiment with patients who suffered from osteoarthritis of the knee. This painful disease results from overuse of the knee joint and is common in the elderly. Conventional physicians treat osteoarthritis with surgery, physical therapy or pain-killing drugs. In the experiment, 19 patients received both pain-relieving drugs and acupuncture. Nineteen control patients received only the drugs. During the study, all 38 patients continued to take the same doses of drugs that they had been taking before the study began. Seventy-three percent of the acupuncture patients reported moderate or marked improvement after 12 weeks of treatment. The control patients reported no improvement.

These results appeared in 1995 in Volume 3 of the journal Osteoarthritis and Cartilage. The study was ongoing as of November 1996.
Endorphins

Some scientists believe acupuncture relieves pain by stimulating the release in the brain of chemicals called endorphins. Endorphins are natural pain killers. They block pain signals, preventing the signals from reaching nerve cells. The pain-killing drug morphine has a chemical structure similar to that of endorphins. Meditation and exercise both trigger the release of endorphins in the brain.

In September 1996, acupuncture researchers held a conference in Arlington, Virginia, entitled “The Physiology of Acupuncture.” The Los Angeles-based American Academy of Medical Acupuncture and the U.S. National Institute on Drug Abuse (NIDA) co-sponsored the conference. At the conference, scientists presented evidence that acupuncture causes changes in blood pressure and in the brain’s electrical activity. They also presented brain-scanning images showing that acupuncture causes increased blood flow to the thalamus. The thalamus is a brain region that serves as a relay station for information gathered by the senses.

Michael O. Smith, the director of the substance abuse division at Lincoln Hospital in New York, reported at the conference that acupuncture has helped him treat recovering drug addicts. Smith’s Drug Court program offers convicted drug offenders counseling and acupuncture instead of prison sentences. About 50% of those who choose the program stay in it for three months of daily treatments. Smith told the Washington Post that this retention rate is “tremendously better than any residential treatment program could imagine attaining.” He believes acupuncture eases drug-withdrawal symptoms and reduces the urge to use drugs again. Scientists do not know how acupuncture might do these things. But they suspect that the endorphins released by acupuncture mimic some of the effects of illegal drugs.

In March 1996, the FDA concluded a six-month inquiry and classified acupuncture needles as Class II medical devices for use by trained professionals. The designation means that the FDA recognizes acupuncture needles as safe for general medical use, as long as they are manufactured according to recognized specifications and used only once.

FDA officials claimed the classification does not mean they advocate acupuncture for any specific condition, or even that they think it works. Bruce Burlington, director of the FDA’s center for devices and radiological health, explained the FDA officials’ logic to the Washington Post with a comparison to surgical devices. He said, “We don’t ask, ‘Does gall bladder surgery work?’ We ask ‘Can a knife make an incision?’ So [the classification] didn’t require us to establish that acupuncture works, but that needles work in acupuncture.”

Acupuncture advocates stated that the Class II designation was important because it should make health insurance companies more willing to pay for acupuncture treatments. A handful of insurance companies covered acupuncture before the new classification, but many companies did not. Acupuncturists and patients who swear by the treatment hoped the FDA designation would help overcome the companies’ reluctance to pay for it. In October 1996, major insurance provider Oxford Health Plans announced that it would cover various unconventional therapies, including acupuncture.

In-Line Skaters Without Pads Injure Wrists And Elbows

In-line skaters could save themselves significant pain and suffering if more of them wore wrist guards and elbow pads, according to a study published in the November 27, 1996, issue of the New England Journal of Medicine.

The study stated that 22.5 million people used in-line skates in 1995, an increase of 79% from 1993. During that same period the number of injuries serious enough to require emergency care increased 169%, to an estimated 99,500. According to the study, about 40,000 of those injuries could have been prevented if all skaters wore wrist guards and elbow pads.

Richard A. Schieber, of the U.S. Centers for Disease Control and Prevention, led the study, which looked at 161 in-line skating accidents in 1993. Wrist injuries were most common, accounting for 32% of the injuries. Another 13% of the injuries were to the lower leg, including the ankle; 12% were to the face or chin; 9% to the elbow; 6% to the knee; 5% to the head; and 23% to other parts of the body.

Schieber told the Associated Press that injury typically occurred to a beginner wearing little or no padding. Almost half the injured people, 45%, were wearing no pads when they were injured. Only 7% were wearing wrist guards, elbow pads, knee pads and a helmet.

One-third of the injured people were wearing wrist guards when they were injured, and 28% were wearing elbow pads. Those who did not wear wrist pads and elbow pads were 10 times as likely to injure their wrists or elbows as those who wore the protection.

Schieber said that helmets and knee pads were probably effective at preventing injuries, but that there were too few head and knee injuries in his study to know how much protection helmets and knee pads provided.

Exercise: No Pain Still Means Gain

Many people take it for granted that the heavier the weights you lift, the bigger the muscles you’ll grow. When a team of researchers from McMaster University in Ontario, Canada tested this idea, however, they found that this common belief could be wrong. The new study, published April 2012 in the Journal of Applied Physiology, compared muscle tissue growth — also called muscle hypertrophy — in the leg muscles of 16 weight-lifting subjects. The authors, led by graduate student Cameron Mitchell of McMaster’s Department of Kinesiology, found that as long as the subjects lifted weights to the point of fatigue — the point when they could no longer lift the weight with proper form — the amount of weight used did not affect gains in muscle size and strength. “Loads that were quite heavy and comparatively light were equally effective at inducing muscle growth and promoting strength,” says Mitchell.

Kinesiology is the study of human physical activity and movement. Stuart Phillips, one of the study’s authors and a professor of kinesiology at McMaster, told Today’s Science that pursuing a career in the field requires “an ability to work with, and love of, people,” since kinesiologists “work with great athletes at one end of the spectrum and with older frail folks at the other.”

 

Exercising to Answer a Fitness Question

 

Kinesiologists and other researchers at McMaster had previously shown that men who exercised with heavier weights made new muscle proteins at the same rate as those lifting lighter weights, as long as the latter group lifted to the point of fatigue. If protein changes after a single session were the same, they wondered, might muscle volume gains also be the same over many training sessions? This experiment was an attempt to find out. “The analogy I use”, Phillips told Today’s Science, “is that we can measure acutely the new bricks that are added to a house, but to know whether the house got bigger we need the longer-term training study.”

To find out whether or not “the house got bigger”, the researchers had 18 healthy subjects, all young men, participate in knee extension exercises for 10 weeks. Each participant was assigned one of three workouts for one leg and a different one of the three workouts for the other leg; workouts differed in terms of amount of weight and number of sets. By measuring changes in muscle size, chemistry and performance, the researchers sought to determine whether or not the weight lifted and the number of sets completed influenced the growth of muscle tissue. Before the first session, the researchers collected tissue samples or biopsies from the subjects’ leg muscles and used magnetic resonance imaging (MRI) to scan and digitize the three-dimensional structure of the muscles.

The researchers also measured subjects’ performance on knee extension exercises, including the maximum amount of weight each participant could lift with each leg. The three possible workouts assigned, based on these measurements, were: one set of knee extensions at 80% of the maximum weight they could lift, three sets at 80% of the maximum, or three sets at a lighter 30% of maximum. To complete a set, a participant would continue doing knee extensions until he could no longer continue with proper form. The researchers called this the point of “fatigue” or “failure.” For the heavier 80% groups, this typically meant eight to twelve repetitions per set, and for the 30% group about 25 to 30 repetitions. Immediately after each workout, all the participants ate the same type of high-protein energy bar and drank approximately 300 milliliters (10 ounces) of water. After the first workout, researchers collected a second muscle sample for chemical analysis, and after the final workout, they took a third sample to look for growth in the muscle fibers. They also took a second MRI scan of the leg.
Measuring Muscle Growth

The team checked for two types of possible muscle hypertrophy: over an entire muscle, and within a small sample of muscle fibers. They examined a muscle in the thigh called the vastus lateralis, a part of the quadriceps that extends the knee. Hypertrophy, the type of muscle growth caused by exercise, generally happens when muscle fibers become thicker — as opposed to new fibers being produced in the muscle. The team expected the two types of hypertrophy measurement in the vastus lateralis to correlate, meaning that if one measure changed, the other should change correspondingly.

To measure volume changes over the entire vastus lateralis, the researchers compared the MRI scans taken before and after the 10-week program. (To conduct an MRI, the part to be scanned [in this case the leg] is first placed in a powerful magnetic field, constraining the motion of certain molecules. Then, specifically calibrated radio waves are sent into the body. By looking at the energy that comes back out, a computer can reconstruct — in three dimensions — the tissues in question.)

Researchers examined computer-generatd slices of the MRIs, with each slice being a cross section of the leg. They used specialized image analysis software to determine the area of the part of the vastus lateralis in question. They multiplied the muscle area calculated for each slice by the distance between slices to come up with an approximate muscle volume which, when added to the volume of other slices in the scan, provided a measure of the total volume of the muscle.

To measure volume changes in individual muscle fibers, the team used a different method. They compared the tissue samples they collected from the first and last of the three biopsies. They wanted to look for changes in thickness in the cross-sectional area of the muscle fibers. To collect the samples, they first administered local anesthesia to the subjects. They then used a special type of needle, called a Bergström needle, along with suction to take about 80 milligrams of tissue from each vastus lateralis.

Tissue samples from the biopsies were placed in a viscous material called OCT (optimal cutting temperature medium), frozen with the OCT into a solid block, and later sliced. The slices were stained to distinguish two kinds of fibers, called type I and type II, or slow twitch and fast twitch, respectively. With a microscope, the researchers took digital photographs of the slices. Using the same image analysis software as they had used with the MRIs, they identified individual muscle fibers and drew outlines around 55 of each of the two types. Comparing the areas outlined before and after the 10 weeks of training, the researchers could determine if the muscle fibers had gotten thicker.
Bucking Conventional Wisdom

The results of both measurements of hypertrophy supported the same conclusion: the subjects’ muscle growth was not dependent on how much weight they had lifted. As long as participants continued exercising until the point of fatigue, it did not matter whether they lifted 30% of their maximum or 80%; performing more repetitions with the lighter weight achieved the same level of growth as fewer repetitions with the heavier load.

Measures of performance on knee extension exercises also showed similar gains in strength for all three groups. There was, however, one difference among them: the maximum weight the subjects could lift. Those who trained on heavier weights (the groups training at 80% of maximum) were able to lift heavier weights after the training program than the rest of the subjects. Although the researchers did not specifically measure velocity or acceleration, there were indications that those training on lighter weights were likely able to achieve greater speeds and accelerations, but those training on heavier weights were probably able to more slowly lift more weight.

Another aspect of the experiment that yielded unclear results was the effect the number of sets had on hypertrophy. Subjects in the groups performing three sets of knee extensions showed more than twice the amount of muscle growth as those in the one-set group. However, given the limited number of people in the study, researchers could not know for sure whether those differences came from significant differences in hypertrophy or from the regular fluctuations in data that are part of every real-world experiment. Repeating the experiment with more subjects or over a longer period of time could establish whether or not the number of sets has a significant effect on hypertrophy.
An Experiment Within the Experiment: Investigating Proteins’ Role in Muscle Growth

While they were examining hypertrophy, the researchers were also curious to see if certain changes in muscle chemistry during the first exercise session would accurately predict muscle growth over the full 10-week period. They analyzed the chemistry of the muscle tissue extracted during the biopsies before and after the first session to look for changes in three proteins that are affected by exercise: Akt, mTOR and p70S6K. The researchers examined “phosphorylation” of these proteins — whether or not a phosphate ion is attached. For many proteins, phosphorylation indicates if the protein is active or not. They wanted to know if phosphorylation of these proteins was correlated with hypertrophy. The researchers used a pestle to homogenize or mash up the muscle tissue samples by hand and then conducted a series of chemical tests for phosphorylation. They found that, while phosphorylation in certain proteins correlated with some of the exercises, none of the three phosphorylation reactions examined was a consistent predictor of long-term muscle growth.
A Revised Understanding of Hypertrophy

If, as this study suggests, hypertrophy is not determined solely by the amount of weight lifted, people can increase muscle size in different ways. “A much broader range of loads including quite light loads can induce muscle growth,” explains Phillips, “provided it is lifted to the point where it is difficult to maintain good form.” If a person is training to lift heavy loads, then fewer sets with more weight could make sense, but for those training for general fitness, endurance, appearance or speed, more repetitions at a lower weight level might be just as — if not more — effective. “Many older adults can have joint problems which would prevent them training with heavy loads,” says Mitchell. “This study shows that they have the option of training with lighter and less intimidating loads and can still receive the benefits.”
Discussion Questions

Why did the researchers assign a different workout for each subject’s right and left legs? Why couldn’t the subjects perform the same workout on both legs?

Why might the researchers have chosen to exclude women from their study?

Which types of athletes would train with a heavier load, and which with a lighter load but with more repetitions? Why?

The scientists conducting this study were not able to determine conclusively whether or not the number of sets influenced muscle growth. How might you change this experiment (or design a different one) to better test the relationship between the number of sets and hypertrophy?

Could a Light on the Knee Cure Jet Lag?

 

Shining a light on the back of someone’s knee can adjust their “internal clock,” according to a group of scientists. If the findings hold true, they may lead to better treatments for malfunctions of the body’s internal clock, like jet lag, winter depression and insomnia.

 

The internal clock is centered in a part of the brain called the suprachiasmatic nucleus. Among other things, it regulates the body’s daily cycles of sleep and waking. Throughout the year the clock adjusts a person’s sleeping schedule to the changing lengths of night and day. Scientists had assumed that the clock makes these adjustments based on sunlight that enters the eyes. But the new findings suggest that light can influence the body’s inner workings through at least one other channel—namely, the skin.

 

The study was headed by Scott S. Campbell and Patricia J. Murphy of Cornell University. The results of the study came as a surprise to scientists, who did not think that the skin had light receptors. Accordingly, many were withholding judgment until the results could be verified. Campbell and Murphy reported their findings in the January 16, 1998, issue of Science.

 

Besides sleeping and waking, many other processes are regulated by the body’s clock. Resistance to alcohol, susceptibility to pain, and levels of testosterone and other hormones vary predictably according to the time of day. In order to test light’s ability to alter the body’s clock via the skin, the researchers studied two prominent features controlled by the clock: body temperature and levels of the hormone melatonin.

 

Melatonin, which makes people feel sleepy, starts to increase in the blood around 10 p.m. It starts to drop around dawn. Body temperature keeps climbing during the day, starts to decline around 8 p.m., and reaches its lowest point at about five in the morning. 

 

The researchers measured body temperature and melatonin levels in 15 people whose skin had been exposed to varying amounts of light. The people spent four days in dimly lit rooms. Some of them received doses of light at three-hour intervals between midnight and noon. The light was applied via a fiber-optic pad attached to the back of the subjects’ knees. The other subjects received no light. On the fourth day, researchers found that the timing of the minimum body temperature for those who had received the light treatments had shifted by up to three hours. The shift in the timing of the minimum body temperature suggested that the timing of the subjects’ internal clocks had shifted as well.

 

“This is the first demonstration that you can affect the human clock without going through the eyes,” Campbell told the New York Times. Scientists speculated that other parts of the body besides the knees may be receptive as well.

 

 

If the findings hold true they may lead to more efficient ways to treat disorders of the body’s internal clock, like seasonal affective disorder (SAD), which causes wintertime depression. Scientists believe SAD results from changes in the clock brought on by winter’s short days. SAD sufferers have benefited from sitting under bright lights in the early morning. However, if the body’s internal clock can be corrected by light hitting the skin, patients can undergo the early morning light treatments while still sleeping.

 

Jet lag, a condition characterized by weakness, fatigue and an inability to concentrate, occurs when people travel across time zones. This causes the rhythms of their internal clocks to go awry. Airplane passengers may be able to correct the problem by attaching light-emitting pads to the backs of their knees.

 

Scientists are not sure how light hitting the back of the knee registers with the clock in the brain. Some suggested that the light triggers a signal that gets carried to the suprachiasmatic nucleus by the blood pigment hemoglobin. Hemoglobin, like the plant pigment chlorophyll, is sensitive to light.