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The Physiology Of Speed

Posted by Dan Peterson Aug 29, 2009

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Usain Bolt, the triple Olympic gold medal sprinter from Jamaica, predicted last week that he could break his own world record of 9.69 seconds in the 100 meter sprint with a time as low as 9.54 seconds.  (8/15 update: he came very close running a 9.58 at the World Championships in Berlin.)

 

He claimed his coach told him its possible, so he believes him. His coach, Glen Mills, may have just finished reading some new research coming out of Duke University that showed sprinters and swimmers who are taller, heavier but more slender are the ones breaking world records.

 

At first glance, it may not make sense that bigger athletes would be faster. However, Jordan Charles, a recent engineering grad at Duke, plotted all of the world record holders in the 100 meter sprint and the 100 meter swim since 1900 against their height, weight and a measurement he called "slenderness."

 

World record sprinters have gained an average of 6.4 inches in height since 1900, while champion swimmers have shot up 4.5 inches, compared to the mere mortal average height gain of 1.9 inches.

During the same time, about 7/10 of a second have been shaved off of the 100-meter sprint while over 14 seconds have come off the 100-meter swim record.

 

What's going on

Charles applied the "[constructal theory | http://www.constructal.org/]" he learned from his mentor Adrian Bejan, a mechanical engineering professor at Duke, that describes how objects move through their environment.

 

"Anything that moves, or anything that flows, must evolve so that it flows more and more easily," Bejan said. "Nature wants to find a smoother path, to flow more easily, to find a path with less resistance," he said. "The animal design never gets there, but it tries to be the least imperfect that it can be."

 

Their research is reported in the current online edition of the Journal of Experimental Biology.

 

For locomotion, a human needs to overcome two forces, gravity and friction. First, an athlete would need to lift his foot off the ground or keep his body at the water line without sinking. Second, air resistance for the sprinter and water resistance for the swimmer will limit speed.

 

So, the first step is actually weight lifting, which a bigger, stronger athlete will excel at. The second step is to move through the space with the least friction, which emphasizes the new slenderness factor.

 

By comparing height with a calculated "width" of the athlete, slenderness is a measurement of mass spread out over a long frame. The athlete that can build on more muscle mass over a aerodynamic frame will have the advantage.

 

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The numbers

In swimming, legendary Hawaiian champion Duke Kahanamoku set the world record in 1912 with a time of 61.6 seconds with a calculated slenderness of 7.88. Some 96 years later, Eamon Sullivan lowered the world mark to 47.05 seconds at a slenderness factor of 8.29.

 

As the athletes’ slenderness factor has risen over the years, the winning times have dropped.  In 1929, Eddie Tolan's world-record 100 meter sprint of 10.4 seconds was achieved with a slenderness factor of 7.61. When Usain Bolt ran 9.69 seconds in the 2008 Olympics, his slenderness was also 8.29 while also being the tallest champion in history at 6-feet 5-inches.

 

“The trends revealed by our analysis suggest that speed records will continue to be dominated by heavier and taller athletes,” said Charles. “We believe that this is due to the constructal rules of animal locomotion and not the contemporary increase in the average size of humans.”

 

So, how fast did the original Olympians run? Charles used an anthropology finding for Greek and Roman body mass and plugged it into his formula.

 

“In antiquity, body weights were roughly 70 percent of what they are today,” Charles said. “Using our theory, a 100-meter dash that is won in 13 seconds would have taken about 14 seconds back then.”

Bolt puts his prediction to the test next month at the track and field world championships in Berlin. One of his main competitors is Asafa Powell, the previous world record holder, who is shorter and has a slenderness factor of 7.85. My money is on the Lightning Bolt.

 

Please read more sports science articles at Sports Are 80 Percent Mental.

460 Views 0 Comments Permalink Tags: olympics, sports_science, track_and_field, usain_bolt

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For any guy who has endured more than thirty minutes on a road bicycle seat, there is usually some concern over the strange numbness that occurs in places that should not go numb. Well, a new study has some good and bad news.

 

Spanish researchers have found that active male cyclists have lower quality sperm to the point of infertility risk. Among other things, they blame the painful "function over form" design of the wedge bicycle seat.

 

The good news is that unless you're training to be in the next Tour de France with Lance Armstrong, your time on the saddle shouldn't do any long-term damage.

 

A team led by professor Diana Vaamonde, from the University of Cordoba Medical School, tracked the workout regimen of 15 Spanish triathletes, with an average age of 33 who had been training for at least eight years, while also monitoring their sperm morphology.




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For those in the test group that covered more than 180 miles per week on their bikes, the percentage of normal looking sperm dropped from a group average of 10 percent to 4 percent, a rate where infertility problems begin. Increased swimming or running did not affect sperm quality.

 

"We found a statistically adverse correlation between sperm morphology and the volume of cycling training undertaken per week," Vaamonde said. "We believe that all the factors inherent in this sports activity, especially with regards to the cycling part, may affect sperm quality," she added. "Moreover, we think that normal physiological homeostasis – the body’s ability to regulate its own environment – may become irreversibly altered, therefore resulting in complex anomalies."

 

Vaamonde cited three possible reasons for the results: the increased heat during exercise, the friction and pressure against the seat causing microtrauma on the testes, and the overall rigor of intense exercise.

 

The study was released last week in Amsterdam at the annual conference of the European Society of Human Reproduction and Embryology (ESHRE).

 

The Spanish researchers were following up on research from 2002 that showed similar results for mountain bikers. In that study, Austrian researcher Ferdinand Frauscher tested 40 active (two hours per day) mountain bikers with 30 non-bikers. He found that the bikers had about half the sperm count of the non-bikers. Frauscher explained (as only a medical doctor can) the possible reasons: "The exact causes for the decreased sperm motility are unclear. We believe that repeated mechanical trauma to the testicles results in some degree of vascular damage, and may thereby cause a reduction in sperm motility." Ouch.

 

For casual bike riders, the risk is still quite low. Allan Pacey, senior lecturer in andrology at the University of Sheffield, told BBC News, "It is important to stress that even if the association between cycling and poor sperm morphology is correct, men training for triathlons are spending much more time in the saddle than the average social cycler or someone who might cycle to and from work."

 

For those that are still not okay with the "saddle sores," there are always the anatomically correct seats and the padded biker shorts, not to mention recumbent bikes. Beyond that, maybe a nice jog would be better.

 

Please read more sports science articles at Sports Are 80 Percent Mental!

610 Views 0 Comments Permalink Tags: cycling, triathlon, tour_de_france, lance_armstrong, sports_science

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After an hour of sweating on the treadmill or pumping iron, most of us look forward to the extra post-exercise "afterburn" of fat cells that has been promised to us by fitness pundits. This 24-hour period of altered metabolism is supposed to help with our overall weight loss. 

Unfortunately, a recent study found this to be a myth for moderate exercisers.

 

The new research clarifies a misunderstanding that exercisers can ignore their diet after a workout because their metabolism is in this super active state.

 

"It's not that exercise doesn't burn fat," said Edward Melanson, associate professor of medicine at the University of Colorado, "It's just that we replace the calories. People think they have a license to eat whatever they want, and our research shows that is definitely not the case. You can easily undo what you set out to do.”

 

The findings were detailed in the April edition of Exercise and Sport Sciences Review.

 

What does happen


Melanson and his team set out to measure whether people were able to burn more calories for the 24 hours after a workout compared to a day with no exercise. Their test groups, totaling 65 volunteers, included a mix of lean vs. obese and active vs. sedentary people.

On exercise days, they rode stationary bikes until they had burned 400 calories. Their pre and post exercise diet was controlled.

Throughout the groups, there was no difference in the amount of fat burned in the 24-hour period either with or without exercise.  Of course, during the exercise plenty of calories were being burned and that's the formula that Melanson would like us to remember.  "If you are using exercise to lose body weight or body fat, you have to consider how many calories you are expending and how many you are taking in," Melanson recently told WebMd. The daily energy balance or "calories in vs. calories out" is the most reliable equation for long-term weight loss.

While the current research focused on the moderate activity levels of most people, the researchers admitted they still need to examine the effect of higher intensity workouts and multiple consecutive days of exercise.

They are clear on their current message. "We suggest that it is time to put the myth that low intensity exercise promotes a greater fat burn to rest," Melanson writes. "Clearly, exercise intensity does not have an effect on daily fat balance, if intake is unchanged."

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Type of workout

So, how about a weight resistance training program mixed in with cardio work?  Another fitness industry claim is that more muscle mass on your frame will raise your metabolism rate, even while sitting on the couch.

 

The same study, using the same test groups, found the post-exercise rate of calorie burn did not change on days of lifting versus no lifting. It is true that a pound of muscle burns seven to ten calories per day versus only two calories per day for a pound of fat. However, the average adult just doesn't put on enough lean muscle mass to make this difference significant.

 

While this research dispels one myth about exercise, there is still overwhelming evidence of the benefits of movement when combined with your eating habits. So, before eating that double cheeseburger and fries, you might want to do some math to figure out how many stairs you'll have to climb to break even.

 

 

Please visit my other sports science articles at Sports Are 80 Percent Mental </b>

389 Views 0 Comments Permalink Tags: training, running, fitness, evidence_based_coaching, sports_science

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At a recent baseball game, the 12-year-old second baseman on my son's team had a ground ball take a nasty hop, hitting him just next to his right eye. He was down on the field for several minutes and was later diagnosed at the hospital with a concussion.

 

Thankfully, acute baseball injuries like this are on the decline, according to a new report. However, several leading physicians say overuse injuries of young players caused by too much baseball show no signs of slowing down.

 

Our unlucky infielder's hospital injury report may become part of a national database called the National Electronic Injury Surveillance System (NEISS), part of the U.S. Consumer Product Safety Commission. It monitors 98 hospitals across the country for reports on all types of injuries.

 

Bradley Lawson, Dawn Comstock and Gary Smith of Ohio State University filtered this data to find just baseball-related injuries to kids under 18 from 1994-2006.

 

During that period, they found that more than 1.5 million young players were treated in hospital emergency rooms, with the most common injury being, you guessed it, being hit by the ball, and typically in the face.

 

The good news is that the annual number of baseball injuries has decreased by 24.9 percent over those 13 years. The researchers credit the decline to the increased use of protective equipment.

 

"Safety equipment such as age-appropriate breakaway bases, helmets with properly-fitted face shields, mouth guards and reduced-impact safety baseballs have all been shown to reduce injuries," Smith said. "As more youth leagues, coaches and parents ensure the use of these types of safety equipment in both practices and games, the number of baseball-related injuries should continue to decrease. Mouth guards, in particular, should be more widely used in youth baseball."

 

Their research is detailed in the latest edition of the journal Pediatrics.

 

The bad news is ...


 


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While accident-related injuries are down, preventable injuries from overuse still seem to be a problem, according to author Mark Hyman. In his recent book, "Until It Hurts," Hyman admits his own mistakes in pressuring his 14-year-old son to continue pitching with a sore arm, causing further injury.

 

Surprised by his own unwillingness to listen to reason, Hyman, a long-time journalist, researched the growing trend of high-pressure parents pushing their young athletes too far, too fast.

 

"Many of the physicians I spoke with told me of a spike in overuse injuries they had witnessed," Hyman told Livescience. "As youth sports become increasingly competitive — climbing a ladder to elite teams, college scholarships, parental prestige and so on — children are engaging in a range of risky behaviors."

 

One expert he consulted was Dr. Lyle Micheli, founder of one of the country's first pediatric sports medicine clinics at Children's Hospital in Boston. Micheli estimates that 75 percent of the young patients he sees are suffering from some sort of overuse injury, versus 20 percent back in the 1990s.

 

"As a medical society, we've been pretty ineffective dealing with this," Micheli said. "Nothing seems to be working."

 

Young surgeries

 

In severe overuse cases for baseball pitchers, the end result may be ulnar collateral ligament surgery, better known as "Tommy John" surgery. Dr. James Andrews, known for performing this surgery on many professional players, has noticed an alarming trend in his practice. Andrews told The Oregonian last month that more than one-quarter of his 853 patients in the past six years were at the high school level or younger, including one 7-year-old.

 

Last spring, Andrews and his colleagues conducted a study comparing 95 high-school pitchers who required surgical repair of either their elbow or shoulder with 45 pitchers that did not suffer injury.

 

They found that those who pitched for more than eight months per year were 500 percent more likely to be injured, while those who pitched more than 80 pitches per game increased their injury risk by 400 percent.  Pitchers who continued pitching despite having arm fatigue were an incredible 3,600 percent more likely to do serious damage to their arm.

 

Hyman encourages parents to keep youth sports in perspective. "I think that, generally, parents view sports as a healthy and wholesome activity. That's a positive. But, we live in hyper-competitive culture, and parents like to see their kids competing," he said. "It's not only sports. It's ballet and violin and SAT scores and a host of other things.  It's in our DNA."

 

 

Please visit my other sports science articles at Sports are 80 Percent Mental.</b>

523 Views 0 Comments Permalink Tags: coaching, baseball, evidence_based_coaching, sports_science, sport_skills, youth_sports

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As usual, your Mom was right. When she told you to get outside and play, she instinctively knew that would be good for you.

 

Researchers at the University of Exeter have found that kids' natural short bursts of play energy contribute just as much to a healthy lifestyle as longer bouts of organized exercise, such as gym class.

As of 2008, 32 percent of U.S. children were overweight or obese, as measured by their body mass index. While many organized programs have studied this epidemic, the prescription remains the same: less food, more exercise.

 

In fact, a previous study of 133 children found that the physical activity of the obese children over a three-week period was 35 prcent less during school days and 65 percent less on weekends compared to the children who were within accepted healthy weight norms.

 

In the new study, Michelle Stone and Roger Eston of Exeter's School of Sport and Health Sciences measured the activity level of 47 boys aged between 8 and 10 over seven days using an accelerometer strapped to each boy's hip (similar to the one inside your iPhone or Wii controller that senses motion).

The key was to find a model that would record the shortest bursts of energy, sometimes less than 2 seconds. As any boy's parents know, those spurts can happen all afternoon, whether it be chasing the dog, throwing rocks in the lake or climbing a tree.

 

The researchers also measured waist circumference, aerobic fitness and blood pressure of each boy. They found that even though their activity levels came in many short chunks, their health indicators were all in the normal range.

 

Stone explains their conclusion, "Our study suggests that physical activity is associated with health, irrespective of whether it is accumulated in short bursts or long bouts. Previous research has shown that children are more naturally inclined to engage in short bursts of running, jumping and playing with a ball, and do not tend to sustain bouts of exercise lasting five or more minutes. This is especially true for activities that are more vigorous in nature.

 

Their findings are in the April edition of the International Journal of Pediatric Obesity.

 

The researchers admit that more research is needed to measure long-term effects on health.  Establishing activity guidelines for parents and schools will help the kids plan time to move each day.

 

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The National Football League has even started a program called NFL Play 60 that encourages kids to move for at least 60 minutes each day.  "Our players know the importance of staying healthy and it’s important that young fans also understand the value of exercise," said NFL Commissioner Roger Goodell. "Play 60 is an important tool in ensuring children get their necessary daily physical activity as recommended by health and fitness experts."

 

So, more recess and less physical education in our schools? Maybe, according to Stone, "If future research backs up our findings, we would do better to encourage young children to do what they do naturally, rather than trying to enforce long exercise sessions on them. This could be a useful way of improving enjoyment and sustainability of healthy physical activity levels in childhood."

 

Please visit my other sports science articles at Sports Are 80 Percent Mental

434 Views 0 Comments Permalink Tags: fitness, sport_science, evidence_based_coaching, sports_science, youth_sports

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Many people exercise to improve the health of their hearts. Now, researchers have found a link between your heart rate just before and during exercise and your chances of a future heart attack.
Just the thought of exercise raises your heart rate. The new study shows that how much it goes up is related to the odds of you eventually dying of a heart attack.

More than 300,000 people die each year from sudden cardiac arrest in the U.S., often with no known risk factors. Being able to find early warning signs has been the goal of researchers like Professor Xavier Jouven, of the Hopital Européen Georges Pompidou in Paris.

Jouven's team has been examining data from a study of 7,746 French men employed by the Paris Civil Service and given health examinations between 1967-1972, including exercise tests, electrocardiograms and heart rate measurements. Over an average 23-year follow-up, 83 eventually died of heart attacks, also known as sudden cardiac death (SCD).

In 2005, Jouven's team first showed that how a heart behaves before, during and after exercise could predict future problems. The risk of a future heart attack was about four times higher than normal in men whose resting hearts beat faster than 75 beats per minute (bpm) or did not speed up by more than 89 beats during exercise. Likewise, heart attacks were twice as likely in men whose heart rates didn't slow down more than 25 beats in the first minute after exercise stopped.

Just a thought

In the latest study, published last week in the European Heart Journal, the French researchers found another interesting clue in the same data set. Not only was the resting heart rate of each person taken, but also another reading right before they were to start a strenuous exercise bike test. This rate is affected by what they called "mild mental stress." It measures the body's physiological anticipation of exercise .

 

Think of this type of stress as the brain's warning to the body that some difficult, sweaty work is about to begin. It is normal for this rate to be slightly higher than the resting rate, but for some it is significantly higher.

 

The men who had the highest increase in heart rate during this period (increasing by more than 12 beats a minute) had twice the risk of eventual future sudden cardiac death compared to men who had the lowest increase in heart rate (an increase of less than four beats a minute).

 

So, the high-risk heart overreacts to the anticipation of exercise, and then does not respond to the full extent needed during exercise. Afterwards, it does not regulate itself down fast enough.

 

What's going on

Jouven hypothesized that the autonomic nervous system (ANS), the body's internal control governor, must be out of whack.

 

!http://3.bp.blogspot.com/_3b3RMRFwqU0/Six0njRi5kI/AAAAAAAAArk/ETSL44_ynGQ/s400/autonomic_nervous_system.jpg|src=http://3.bp.blogspot.com/_3b3RMRFwqU0/Six0njRi5kI/AAAAAAAAArk/ETSL44_ynGQ/s400/autonomic_nervous_system.jpg|border=0! The ANS has two parts, the sympathetic and the parasympathetic. Joeven suggests we think of the sympathetic system as the accelerator that turns up our response to exercise by increasing our heart rate. Putting the brakes on this acceleration are the vagus nerves, part of the parasympathetic system, preventing our heart from running out of control.

 

"There is a balance between the accelerator (sympathetic activation) and the brake (vagus nerve activation)," Jouven explains. "During an ischemic episode, when blood flow to the heart is reduced, sympathetic activation occurs to counteract it. However, if there is no protection by the vagal tone (the brake), the activation can become uncontrolled and then it becomes dangerous."

 

Finding this connection between heart rate and future heart problems is encouraging for future research, according to Jouven.

 

"These findings may carry significant clinical implications," he said. "Few measurements in medicine are as inexpensive and as easy to obtain in large general populations as to measure the heart rate difference between resting and being ready to perform an exercise test. The results will contribute towards a better understanding of the mechanisms of cardiac death."

 

Please visit my other sports science articles at Sports Are 80 Percent Mental .</b>

354 Views 0 Comments Permalink Tags: running, fitness, sport_science, sports_science, sports_medicine
Dan Peterson

Dan Peterson

Member since: Oct 1, 2007

A Look Inside the Mind of the Athlete - You can find a mix of sport science, cognitive science, coaching and performance stories here as I focus on the "thinking" side of sports. My "home" is at http://blog.80percentmental.com. Thanks for stopping by!

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