的意见

海拔对身体有什么影响?

高度的功能

每年, thousands of people travel to high-altitude environments for tourism, 探险, 或者在各种运动中训练和竞争.

不幸的是, these trips can be marred by the effects of acute altitude sickness, 而且症状因人而异. To understand why people are affected differently, we have to look at how the body is affected by altitude.

“海拔”和海平面有什么不同?

Air is comprised of different molecules, with nitrogen (79.04%)和氧气(20.93%) making up the majority of each breath we take. 这 composition of air remains consistent, whether we are at sea level or at altitude.

然而, 与高度, the “partial pressure” of oxygen in this air (how many molecules of oxygen are in a given volume of air) changes. 在海平面, 氧分压为159毫米汞柱, 而在8,848m above sea level (the summit of Mt Everest), the partial pressure of oxygen is only 53 mmHg.

在高海拔地区, oxygen molecules are further apart because there is less pressure to “push” them together. 这 effectively means there are fewer oxygen molecules in the same volume of air as we inhale. In scientific studies, this is often referred to as “hypoxia”.

在高海拔地区身体会发生什么?

在暴露于高海拔的几秒钟内, 通风是增加, 这意味着我们开始尝试更多的呼吸, as the body responds to less oxygen in each breath, 并试图增加氧气摄入量. 尽管这种反应, there’s still less oxygen throughout your circulatory system, 这意味着到达肌肉的氧气减少. 这 will obviously limit exercise performance.

Within the first few hours of altitude exposure, 水分流失也会增加, 会导致脱水吗. Altitude can also increase your metabolism while suppressing your appetite, meaning you’ll have to eat more than you feel like to maintain a neutral energy balance.

When people are exposed to altitude for several days or weeks, their bodies begin to adjust (called “acclimation”) to the low-oxygen environment. The increase in breathing that was initiated in the first few seconds of altitude exposure remains, and haemoglobin levels (the protein in our blood that carries oxygen) increase, along with the ratio of blood vessels to muscle mass.

Despite these adaptations in the body to compensate for hypoxic conditions, physical performance will always be worse at altitude than for the equivalent activity at sea level. The only exception to this is in very brief and powerful activities such as throwing or hitting a ball, which could be aided by the lack of air resistance.

为什么只有一些人会有高原反应?

Many people who ascend to moderate or high altitudes experience the effects of acute altitude sickness. Symptoms of this sickness typically begin 6-48 hours after the altitude exposure begins, 和包括头痛, 恶心想吐, 嗜睡, 头晕和睡眠障碍.

These symptoms are more prevalent in people who ascend quickly to altitudes of above 2,500m, which is why many hikers are advised to climb slowly, particularly if they’ve not been to altitude before.

It’s difficult to predict who will be adversely affected by altitude exposure. Even in elite athletes, high levels of fitness are not protective for altitude sickness.

There’s some evidence those who experience the worst symptoms have a low ventilatory response to hypoxia. So just as some people aren’t great singers or footballers, some people’s bodies are just less able to cope with the reduction in oxygen in their systems.

There are also disorders that impact on the blood’s oxygen carrying capacity, 如地中海贫血, 会增加出现症状的风险.

But the best predictor of who may suffer from altitude sickness is a history of symptoms when being exposed to altitude previously.

高海拔地区的当地人有什么不同?

People who reside at altitude are known to have greater capacity for physical work at altitude. 例如, the Sherpas who reside in the mountainous regions of Nepal are renowned for their mountaineering prowess.

High-altitude natives exhibit large lung volumes and greater efficiency of oxygen transport to tissues, 无论是在休息时还是在运动时.

While there is debate over whether these characteristics are genetic, or the result of altitude exposure throughout life, they provide high-altitude natives with a distinct advantage over lowlanders during activities in hypoxia.

所以除非你是夏尔巴人, it’s best to ascend slowly to give your body more time to adjust to the challenges of a hypoxic environment.

article 最初发表在The Conversation.
关于作者

布伦丹·斯科特博士

Brendan is a lecturer in strength and conditioning in the School of Psychology and Exercise 科学. His research interests include novel resistance training methods, such as using hypoxia (simulated altitude) to improve muscular development.

发布:

2018年6月13日

主题:

健康, 科学, 研究

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