Moreover, the rate of endogenous heat production associated with a 2-h 10-min marathon estimated from ordinary heat-balance equations  is approximately 1400 kcal·h-1. This metabolic heat must be dissipated to the surrounding environment, or body temperature will rise to physiologically dangerous levels. Lind  has demonstrated that core temperature is independent of climate over a temperature range he has termed the "prescriptive zone. " It has been demonstrated that the width of the prescriptive zone progressively narrows as metabolic rate increases.
Thus, climate begins to affect physiological responses to exercise at relatively cooler temperatures during activities that elicit high metabolic rate compared with those eliciting lower metabolic rates. More recently, it has been demonstrated that endurance performance is indeed impaired when exercising in warm versus more temperate laboratory conditions and that air temperatures of approximately 10°C seem optimal for endurance exercise . One criticism of these and other laboratory findings is that typical airflows used for indoor testing situations are well below those encountered when running or cycling outdoors ver the ground. The lack of appropriate airflow substantially reduces the combined heat transfer coefficient  and may overestimate physiological strain . Few field studies have examined the effect of weather conditions on endurance running performance[16,17,22]. Although it is generally observed that race performances worsen as weather warms, there are currently no data quantifying the magnitude of performance reduction. In addition, these studies relied only on data from elite male runners; thus, the implications for slower competitors or women runners are only speculative.
COLD WEATHER BEST FOR MARATHON PERFORMANCE Every runner knows that cool weather is better than hot weather for marathon performance. But a recent study from the U. S. Army Research Institute of Environmental Medicine suggests that relatively cold weather is better than merely cool weather. Researchers gathered many years' worth of results and weather data from six major North American marathons and performed stastical analyses to determine the effect of air temperature on finishing times among runners at various levels of performance.
Specifically, they looked at year-to-year comparative finishing times of the top three male and female runners at each event, as well as the 25th, 50th, 100th, and 300th finishers. The results showed a clear trend toward faster times at colder temperatures. For example, the finishing times of male races winners were, on average, 1. 7% slower than the course record when the air temperature was between 34 and 50 degrees. The finishing times of the top male runners were 2. 5% slower than the course record, however, when the temperature was between 51 and 59 degrees.
And at higher temperatures, finishing times fell off even more dramatically. Runners at all levels were slowed by warmer air, but higher temperatures had a smaller effect on faster runners. The ideal marathon temperature, according to these analyses, was a bone-chilling 41 degrees. Think about that when you sign up for your next marathon! 2. Divers who collect ornamental fish have to work in a hostile environment. Discuss how the SCUBA apparatus helps these divers to meet the challenge of the deep sea environment. SCUBA diving is an exciting and first-hand way for scientists to study the underwater environment.
It is one among the most effective ways for executing underwater experiments that require high quality precise measurements. SCUBA as the name suggests stands for Self Contained Underwater Breathing Apparatus. It literally means that all divers carry all of required breathing equipment’s and gases with them. Hence they are subjected to water temperature, pressure, currents, and other factors revolving oceans present at the diving depth. The NURP program approximately supports about 10,000 SCUBA Divers for Scientific Research work.
NURP provides all the necessary equipments and finances for scientists and technical assistance to conduct diving operations. They use both open circuit as well as closed circuit breathing apparatus. The difference between them primarily relies upon what happens to the exhaled gas. In open system the gas is exhaled in to the water. A closed system apparatus has recycling abilities and thus lasts longer underwater as it reduces carbon-dioxide and adds oxygen in a cyclic manner inside the container. It reduces the amount of gas required in the container and also allows the diver to remain streamlined.
The breathing gas provided by NURP involves compressed air, NITROX and TRIMIX. NITROX is a composition of nitrogen and oxygen whilst TRIMIX is a composition of oxygen, nitrogen and helium. NITROX is of special interest to NOAA. It was in introduced in late 1970’s which allows the divers to stay longer underwater when compared to compressed air alone. Each of these gases is of different properties which enables the diver to dive at maximum depths. 3. The year 1968 marked the emergence of high altitude trained long distance runners from Kenya.
Discuss the scientific basis of high altitude training and how it helps to perform better in long distance events. The theory underlying the belief that training at high altitude can enhance athletic performance sounds reasonable enough. Work out in an environment that causes the body to produce more oxygen-carrying red blood cells and an athlete will be able to perform better than he or she can when trained at a lower elevation. Proponents of this theory point to East African runners, who have dominated long-distance events in recent years, as proof that training at high altitudes pays off.
But if that’s the case, why don’t runners from other high altitude countries such as Peru and Mexico perform equally well? And why do some athletes excel in endurance sports despite having never trained at high altitude? “[High-altitude training has] had so much press that certain athletes feel like they’re at a disadvantage if they’re not doing altitude training,” says Andrew Subudhi, a researcher at the Altitude Research Center in Denver and assistant professor of biology at the University of Colorado in Colorado Springs. There’s a big movement for endurance athletes to move to high altitude if they’re serious about [improving their performance]. ” Into Thin Air But does it really help? Answering that question is harder than one might think, despite numerous scientific studies on the relationship between altitude and athletic performance. The issue reached prominence at the 1968 summer Olympics in Mexico City (elevation 7,349 feet), when questions arose about the best way to prepare for competing in the thin air, Subudhi says. Thin air” is a term used to describe air that contains less oxygen than air at sea level (20. 9% at sea level compared with 15. 3% at higher altitudes).
The number of red blood cells found in the body of an endurance athlete who does not live and train at high altitudes may be insufficient to supply the amount of oxygen needed at higher altitudes. To help deal with this problem, athletes may live and train at high altitudes several weeks before a competition to increase the number of red blood cells, which are produced in response to greater release of the hormone erythropoietin.
More red blood cells allows a person’s blood to carry more oxygen, which partly makes up for the shortage of oxygen in the air. Studies have found that athletes do perform better in competitions held at high altitudes if they live and train at high altitudes prior to competition, Subudhi says, but training at high altitudes does not necessarily help athletes perform better at low altitudes as one might assume. “When you’re at altitude, you can’t train as hard, and when you’re not training as hard, you’re not getting the same training stimulus,” he says. “Training at altitude doesn’t mean you’ll do well at sea level. Then again, that doesn’t mean that you won’t, says Jack Daniels, PhD, head distance coach at the Center for High Altitude Training at Northern Arizona University.
Daniels says the key benefit to training at higher than normal altitudes is that it teaches an athlete how to hurt, and learning to tolerate pain can help athletes push themselves harder than they would otherwise. “It’s good for an athlete to learn to really lay it out there, and it’s easy to do that [in high altitude] without working quite as hard,” says Daniels, who has coached 31 individual3/22/13 Printer-friendly article page www. motionsports. com/blog/training at altitude. htm 2/3 NCAA national champions in his career. Although there are benefits to training at altitude, Daniels says, the advantages one might gain are unimportant when compared with more mundane factors. No matter where people train, he says, they want comfortable housing, healthy food, a friendly atmosphere, good training facilities, desirable weather, and adequate medical and therapy attention. “In other words, you train best where you are happiest,” Daniels says. If you can have that at altitude, that's good, but if you do altitude-type things and don't have those other things, then you are wasting your time. It is very disturbing to me to hear people say, ‘If you don't train at altitude you may as well not bother trying. ’ I think we have all the things an athlete would want right here, but anyone who comes here and is not happy, I encourage to leave. ” Live High, Train Low Daniels also doesn’t believe in another philosophy that has gained considerable support in recent years from researchers who have studied the altitude-performance relationship.
Known as “live high, train low,” this philosophy holds that endurance athletes benefit most from living in high-altitude conditions but training at low altitude where they are able to push themselves harder. The term “live high, train low” came into being in 1996 when researchers James Stray-Gundersen and Benjamin Levine studied the relationship between altitude, training, and performance using three groups of endurance athletes. One group lived and trained in Park City, Utah, (elevation 7,000 feet) while another group lived there and trained at a lower altitude.
A third group lived and trained in San Diego (elevation 72 feet). After the four-week training period ended, all were tested at a low altitude. “They found that the group that lived high but trained low got the best benefit; that was measured in 5-kilometer time trials. ” Subudhi says. The reason for the improved performance among the live-high, train-low group, researchers hypothesized, is that by living in high-altitude conditions, their bodies produced more red blood cells in response to the lower concentration of oxygen.
And because these athletes trained at a lower elevation, they were able to push themselves harder than they would have at higher altitudes, resulting in a higher training stimulus. The results of this and other studies received so much media attention that companies began manufacturing masks, tents, and rooms that would allow athletes to live anywhere in high-altitude conditions. Devices cost anywhere from hundreds to thousands to tens of thousands of dollars. Some companies convert entire houses to these conditions, and both Finland and the United States have outfitted dormitories in this way.
Manufacturers claim benefits can occur from as little as six to eight hours of exposure. But those claims are not supported by research, Subudhi says, who contends 15 to 16 hours per day exposure is supported by research. Exercise rooms designed to mimic high-altitude conditions can benefit athletes who live at low altitudes and are planning to compete at a high altitude, he says: “If your competition is at altitude, then you need to train at altitude. ” Altitude Advantage The only danger associated with the use of such devices is reducing oxygen levels too quickly, and almost everyone will experience more difficulty sleeping, Subudhi says.
However, it’s rare to see athletes suffering from acute mountain sickness, commonly known as altitude sickness, or from high-altitude pulmonary or cerebral edema among those who live at an 8,000- to 9,000-foot altitude, he says. Plus, benefits are temporary: An athlete who stops living under high-altitude conditions will begin to see a loss in benefits in about two weeks as extra red blood cells die off, he says. Bob Cranny, PT, owner of Altitude Physical Therapy and Sports Medicine in Boulder, Colo. , is a big believer in the benefits of training at altitudes of 2,500 feet or greater.
He and his wife are both triathletes and marathon runners who moved to Boulder (elevation 5,430 feet) 12 years ago from Long Beach, Calif. , because they believed the higher altitude would enhance their performance. Many athletes in the area follow the live-high, train-low philosophy, although it might more accurately be described as “live high, train lower. ” That’s because many athletes who train in Boulder live at elevations of3/22/13 Printer-friendlyarticlepage www. kmotionsports. com/blog/training at altitude. htm 3/3 round 9,000 feet and travel to Boulder’s 5,430-foot elevation to train, as opposed to sea level. “If you could live at 9,000 feet and train at sea level, that would be even better — that would be wonderful,” Cranny says. So the answer to the question of whether training at high altitude will enhance an athlete’s performance is: maybe. Training at altitude will help some, while other athletes might benefit best from alternate training methods. “I see altitude as a type of training, and if this type suits you then it is good,” Daniels says.