To say where it is the most eye-catching recently, the swimming competition of the 19th Asian Games in Hangzhou is counted as one, and the mainland swimming team has not only achieved outstanding results, but has already won a gold medal, and its personal image is also quite eye-catching.
However, when watching the swimming competition, some viewers found that it was still the season of short-sleeved shorts per capita, but the swimmers were all wearing down jackets when they entered, and the swimmer Wang Shun was even "down jacket + snow boots", and the warmth measures were quite in place.
Source: Xiaohongshu @wannabe video screenshot
On the other hand, athletes in other sports are mostly cooler. Table tennis players mostly wear thin jackets with short-sleeved shorts, basketball players wear loose short-sleeved shorts, rowers wear sleeveless tights...
Table tennis players enter the arena
So, why do swimmers wear down jackets when entering competitions?
Wearing a down jacket is really because of the coldIn fact, swimmers wear down jackets for a simple reason: to keep warm.
But specifically, it is very knowledgeable.
Su Hao, a professor at the School of Sports and Human Science at Beijing Sport University, said, "Unlike other sports, before swimming competitions, athletes need to warm up in a special warm-up pool. After warming up, the athlete's body temperature rises, the muscles are tense, and the cardiopulmonary function is mobilized, which is more conducive to performing at the best level in the competition. ”
Moreover, after the warm-up, there is still a long time before waiting for the official competition to start, and the temperature of the swimming pool is only about 22 degrees, which is lower than the temperature of the pool, if you just wear a swimsuit during the competition, or wear a thin jacket, it is impossible to maintain the best game condition, especially the muscle temperature is easily affected.
You know, muscle temperature is different from body temperature, body temperature refers to the average temperature of the deep part of the body, usually changes little, kept in a fixed range; Muscle temperature is a kind of surface temperature, the value is not stable enough, will be obviously affected by the external environment.
And whether the muscle temperature is suitable or not will really determine the performance of a swimmer on the field.
This is mainly because different muscle temperatures have different physical properties. Simply understood as muscles have viscosity, when the muscle temperature rises, the viscosity of muscles decreases, stretch and elasticity increase; Conversely, muscle viscosity increases, stretch and elasticity decrease. This means that muscle temperature can be directly related to muscle spasms, stretching effect, and amplitude of movement.
Ian Jeffries, professor of strength and conditioning training at the University of South Wales, mentioned in the book "Warm-up Exercise: A Warm-up Training System for Optimizing Sports Performance and Prolonging Sports Career" that with the increase of muscle temperature in warm-up, the elasticity of muscle tissue will increase significantly, thereby potentially increasing the range of movement, which is crucial for the improvement of the speed of subsequent swimmers.
Secondly, the book "Sports Anatomy" mentioned that foreign researchers Wright and Johns found that when muscle temperature rises, its stretching performance increases, and when the muscle temperature reaches 45 °C, the stretchability is increased by about 20%; When the muscle temperature drops to around 20 ° C, muscle tone weakens; When the temperature drops to 18 °C, the stretch decreases by 10%~20%. As a result, the muscle temperature rises and the muscles become relaxed and soft, ensuring that stretching exercises bring maximum benefits; Conversely, stretching when the muscle temperature is not enough can easily lead to muscle tearing.
At the same time, stimulated by external low temperature, muscle temperature is greatly reduced, muscle excitability is increased, and muscle spasms (that is, cramps) are easily caused. Imagine the state of waking up from leg cramps in the middle of the night, and if you play in this state, the result can be imagined...
If there is a problem with the muscles, you can't swim at this speed
In addition to this, muscle temperature also affects muscle strength.
Muscle strength refers to the ability of the body's neuromuscular system to overcome or resist resistance while working. Studies have shown that when muscle temperature decreases, the rate of synthesis and breakdown of ATP (adenosine triphosphate) decreases, and the maximum cardiac output and muscle blood flow are also reduced, resulting in a decrease in muscle work power.
In a cold environment, nerve cooling also alters neuromuscular function and further leads to a decrease in muscle strength.
There are also studies that specifically verify the correlation between muscle temperature and decreased muscle strength.
Researchers such as Sargeant measured peak anaerobic power and force for a maximum sprint force of 20 seconds at four different muscle temperatures and showed that peak force at 32°C and 29°C was reduced by 12% and 21%, respectively, compared to a muscle temperature of 36.6°C.
Oksa and other researchers exposed eight subjects to air at 27°C, 20°C, 15°C, 10°C for 60 minutes, and then measured their maximum rebound jumping ability, and the results showed that at 15°C air lowered calf muscle temperature by 2°C and in 10°C air lowered calf muscle temperature by 3.4°C, resulting in a 24% reduction in jumping flight time. Therefore, if you want to swim faster and smoother, you must maintain a certain muscle temperature, and a clothing with good warmth is particularly important.
Needless to say, the warmth of the down jacket is good. The down in the down jacket is a three-dimensional structure, and a huge branch picture is presented under the microscope, and the velvet is supported by diamond joints, accumulating a large amount of still air, because the conduction coefficient of the air is the lowest, forming a good warmth of the down.
The key is that the down jacket is light and thin, and the athletes wear it light and not bloated, which is convenient for doing some simple warm-up exercises, and it appears slender, and it is also walking with the wind, full of momentum.
This is an inappropriate big show
Can the pool temperature be high?Since the low temperature is not conducive to play, is it okay to directly increase the temperature of the pool? Of course that's not going to work.
Pool temperature is limited, according to the national public places health indicators and limit requirements (standard number: GB 37488-2019) regulations, artificial swimming pool water temperature should be 23 °C ~ 30 °C, while swimming venue temperature is pool water temperature ± 1 °C. Depending on the application scenario (competition, training, entertainment, children, etc.), people will also set a more specific temperature in the standard range.
Specifically, competitive swimming pools (Olympic Games, FINA), 25 °C ~ 28 °C; Indoor constant temperature swimming pool, 24°C~27°C; Children's pool, 28°C~29°C; Resort (entertainment), 27°C~29°C.
It is not difficult to see that no matter how it is set, the temperature of the pool has a temperature difference of nearly 10 ° C from the human body temperature, and it is inevitable that it will be cold just after entering the water. But such a "slightly cold" temperature allows everyone to swim better.
Pool water at the right temperature is both a "radiator" and an "accelerator".
Studies have shown that the calories consumed for 4 minutes in water at 12 degrees Celsius are equivalent to the calories consumed for an hour on land at the same temperature. That is to say, during swimming, the human body will produce a lot of heat, coupled with the acceleration of metabolism, the human body temperature will also rise rapidly. At this time, the pool water below body temperature can quickly transfer excess heat and achieve cooling, so that swimmers can always maintain a relatively cool and comfortable state.
According to the China Meteorological Society, temperature and speed are also related: when the water temperature is 0 °C, the coefficient of friction in the fluid is 1.83, 1.03 at 20 °C, and 0.84 at 30 °C; when the water temperature is 0 °C, the density of water is 1.0 g/cubic centimeter, and at 25 °C it is 0.997 g/cm³, while the density of the human body is between 0.94 g/cubic centimeter and 0.96 g/cubic centimeter when inhaled.
From this, it can be clearly seen that in the appropriate water temperature range, the higher the water temperature, the smaller the friction coefficient, and the resistance of the water will be greatly reduced, thereby increasing the swimming speed. For example, the internal friction at a water temperature of 25°C is about 30% smaller than the internal friction at a water temperature of 10°C, and when the water temperature exceeds 24°C to 28°C, the friction reduction is offset by the corresponding density effect.
On the contrary, the pool water that is too hot is equivalent to a "heater" and "reducer".
When the temperature of the pool reaches more than 30 ° C, it is closer to the surface temperature of the human body, and if you perform strenuous exercise, the large amount of heat generated will not be quickly transferred, and will continue to accumulate, resulting in overheating of the body, dehydration, muscle spasms and other conditions, which may eventually be fatal. In addition, in water close to body temperature, people tend to feel comfortable, relaxed, do not want to exercise, and are not friendly to competitive sports.
Of course, the temperature of the pool water is too low and it is easy to have problems, such as cold shock - under the stimulation of cold water, blood vessels contract significantly, resulting in choking or aspiration of water, thereby suffocating shock; Studies have shown that the average person's breath-holding time at about 15 °C is only one-third of the usual time (about 45 seconds), and at 4 °C, people's average breath holding time is only 9.5 seconds, or even shorter.
In addition, it is certain that too low the temperature of the pool water will also accelerate the drop in muscle temperature, resulting in muscle stiffness and spasms. In addition to considering the person itself, the temperature of the pool water is also to maintain the pool environment.
When the temperature is too low, the chemical reaction of chlorine in the water slows down, and if it is not adjusted, the problem of excessive chlorination may occur. When the water temperature is below 15°C, most salt and chlorine generators will not work, and the pool water will not be thoroughly cleaned. When the temperature of the pool water is greater than 30 ° C, bacteria and other microorganisms will thrive, plus sweat, etc., the smell may be quite strong and mellow.
In general, swimmers are so "cold and know the heat" because they are engaged in competitive sports, and we do not necessarily have to use down jackets for daily swimming, just a blanket.