雅思阅读 70: Sleeping Thin, Racing Fast（睡在高处，跑在低处）

改编参考 Frontiers in Physiology / PMC（2025年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://pmc.ncbi.nlm.nih.gov/articles/PMC12423153/

Reading Passage

A. The idea behind altitude training is almost counter-intuitive. A runner climbs to a mountain camp two or three thousand metres above sea level, lives there for weeks, and then races at sea level — where the air is actually richer in oxygen than the place she has been sleeping. Why would deliberately sleeping in thin air make someone faster when she returns to the oxygen-rich lowlands? The answer lies in the way the body defends itself against a shortage of oxygen. At altitude, every breath carries fewer oxygen molecules than it does at the coast, so the body compensates by producing more red blood cells — the oxygen-carrying packets that transport fuel to working muscles. More red cells mean a greater capacity to move oxygen from the lungs to the leg muscles, and endurance athletes have long believed this extra carrying capacity gives them an edge when they race where the air is thick. The belief is older than the science, but in recent decades the science has begun to test it seriously. Once, an athlete who wanted this effect had to travel to a mountain village and live there for weeks, at great cost and distance from home; today, the same stimulus can be switched on inside a tent above an ordinary gym bed.

B. The classic approach, known as "live high, train low", was formalised in the 1990s and remains the most widely used and best-supported method. Athletes sleep and rest at between roughly 1,800 and 3,000 metres, where the thin air stimulates the kidneys to release the hormone erythropoietin, which in turn signals the bone marrow to manufacture more red blood cells. But they descend to lower elevations for the hard, high-intensity workouts that high training demands. The logic is careful: merely training at altitude has a downside, because the air is so thin that an athlete simply cannot run as fast or as hard, and lost intensity means lost training stimulus. By sleeping high to harvest the oxygen benefit while training low to preserve the intensity of the workout, the method tries to have both advantages at once. Modern versions use hypoxic rooms — low-oxygen tents and chambers in ordinary gyms — so that athletes can "sleep at altitude" without actually travelling to a mountain. These artificial chambers mix nitrogen and ordinary air to reproduce the oxygen partial pressure found two kilometres up, at a fraction of the cost and with the convenience of training on a familiar track.

C. Yet when researchers pooled the evidence, the picture turned out to be more complicated than the legend suggests. A 2025 systematic review and meta-analysis of thirteen randomised trials, involving 276 athletes, found that haemoglobin — the oxygen-binding protein inside red cells — did indeed rise after the intervention, a statistically clear effect. But the increase in total haemoglobin mass, the measure that actually matters for carrying oxygen, was only modest and, in some analyses, did not quite reach statistical significance. The benefit, in other words, is real but smaller than athletes hoped, and it depends heavily on the individual: some athletes respond strongly to the hypoxic stimulus, while others barely change. A separate study of elite swimmers found that the total haemoglobin mass could remain elevated long after a camp, possibly because the new red cells simply lived longer rather than being produced faster. The mechanism, it seems, is not as simple as "more altitude, more blood, more speed". The genetic make-up of the athlete matters: some people are naturally high responders whose EPO rises sharply at thin air, while others barely register the stimulus, which explains why the same camp can transform one competitor and leave another untouched.

D. There are also costs that the original slogan ignored. Sleeping in low-oxygen air for eighteen hours a day leaves some athletes restless, light-headed and unable to sleep deeply, which undermines recovery — the very thing training camps are meant to improve. Iron metabolism is disturbed too: after hard exercise, the body releases a hormone called hepcidin that suppresses iron absorption, and the extra demand for new red cells can push an athlete into iron deficiency, a condition that wipes out the benefit of the whole programme. Coaches now routinely monitor ferritin, the body's iron store, before and during altitude camps, because an athlete who arrives low in iron will not make red cells no matter how thin the air. Immunity, inflammatory markers and fatigue also shift under hypoxia, so a camp that is not well supervised can leave an athlete sicker and slower than when she arrived. This is why modern programmes pair the altitude stimulus with careful monitoring of sleep, appetite and blood, treating the body's response as something to be read rather than simply endured.

E. The honest conclusion is that live-high, train-low works for some athletes, some of the time, and only when the details are managed carefully. It is not the automatic performance miracle of popular myth, but neither is it a placebo. The most effective practitioners treat the hypoxic stimulus as one ingredient among many — iron status, sleep quality, training intensity and genetics all decide whether the body builds more oxygen-carrying capacity or merely suffers. For a well-prepared, iron-rich athlete who tolerates the thin air, a carefully monitored camp can add a small but genuine edge. For everyone else, it may simply be an expensive way to sleep badly. The modern view, in the end, is less glamorous than the mountain-camp legend: altitude training does not gift endurance, it merely exposes, in miniature, the question that every training method must answer — whether the body can actually turn the stimulus into adaptation. Athletes who treat a camp as a box to tick, ignoring iron and sleep, will spend a fortnight in thin air for nothing; those who read their own bodies carefully may find a small but measurable edge waiting at the finish line.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why sleeping thin should help at sea level ii. The classic method — and its modern version iii. What the pooled evidence actually shows iv. The hidden costs and side effects v. A balanced verdict on who benefits vi. How red blood cells carry oxygen vii. Why mountain air is polluted

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What is the core logic of "live high, train low"? A. Train hard at altitude and sleep at sea level. B. Sleep high to stimulate red-cell production, train low to preserve intensity. C. Spend all day and night at altitude. D. Avoid oxygen entirely.

6. What did the 2025 meta-analysis find? A. Haemoglobin rises, but total haemoglobin mass gains were modest. B. Altitude training has no effect at all. C. Every athlete benefits equally. D. Haemoglobin falls sharply.

7. Why do coaches monitor iron stores? A. Iron deficiency prevents the body from making new red cells. B. Iron makes athletes heavier. C. Iron absorbs oxygen in the lungs. D. Iron is a banned substance.

8. What is the writer's final verdict? A. Altitude training is a guaranteed miracle. B. It works for some well-prepared athletes when carefully managed. C. It should be banned everywhere. D. It is entirely a placebo.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The kidneys release erythropoietin in response to low oxygen at altitude.
10. Training hard at altitude is recommended because the air allows faster running.
11. The 2025 meta-analysis included thirteen randomised trials and 276 athletes.
12. Altitude camps never affect an athlete's sleep.
13. Most elite athletes now prefer hypoxic tents over real mountain camps.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

At altitude, the body releases (14) ________, which stimulates red-cell production, but athletes who arrive low in iron may fail to benefit because the hormone (15) ________ suppresses iron absorption after exercise.

答案与解析

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