영어 모의고사 (자동 편성)

Exercise does far more than strengthen muscles and the heart; it also produces measurable changes within the brain itself. During sustained physical activity, the body ① releases a protein called brain-derived neurotrophic factor, which supports the growth of new neurons and ② strengthens connections between existing ones, particularly in regions associated with memory and learning. Studies comparing physically active students to sedentary peers have repeatedly found that the active group ③ performing better on tests of attention and problem-solving, even when the exercise session ends well before the test begins. Researchers believe that exercise increases blood flow to the brain, ④ delivering oxygen and nutrients more efficiently, while also reducing levels of stress hormones that can interfere with clear thinking. These findings have encouraged some schools ⑤ to schedule exercise before demanding academic classes.

Sleep is not a single, uniform state but a cycle that alternates between two very different modes: REM (rapid eye movement) sleep and non-REM sleep. During non-REM sleep, especially its deepest stage, the brain waves slow down dramatically, the body temperature drops, and tissue repair and growth hormone release reach their peak. This is the period ① most closely associated with physical restoration. REM sleep, by contrast, brings rapid eye movements, near-total muscle paralysis, and brain activity that closely ② resemble wakefulness. Most vivid dreaming occurs during this stage, and researchers believe it ③ plays a central role in consolidating memories and processing emotional experiences. A healthy night typically cycles through both stages four or five times, with non-REM ④ dominating the early hours and REM periods lengthening toward morning. Disrupting either stage, through frequent awakenings or alcohol use, can leave a person ⑤ feeling unrested even after a full night in bed.

Modern sports wearables, from wrist-worn fitness trackers to smart insoles embedded in running shoes, continuously collect data that would once have required a laboratory to measure. Heart rate, sleep quality, running cadence, and even subtle changes in gait can now be ① monitored during ordinary daily activity rather than only in a controlled clinical setting. Coaches use this constant stream of information to detect early warning signs of overtraining, sometimes noticing a decline in performance ② after the athlete consciously feels tired. However, the flood of data has created a new challenge: distinguishing a meaningful pattern from ordinary daily fluctuation requires expertise that many amateur athletes simply ③ do not have. Some researchers worry that casual users may misinterpret a single unusual reading as a serious problem, leading to ④ needless anxiety rather than useful insight. For this reason, most experts recommend treating wearable data as a general trend to observe over time, not as a precise ⑤ diagnostic tool.

Caffeine is the most widely consumed stimulant in the world, prized for its ability to ① sharpen focus and fight off fatigue within minutes of consumption. It works by blocking adenosine, a chemical that gradually builds up in the brain throughout the day and makes us feel ② decreasingly sleepy the longer we stay awake. By occupying the receptors that adenosine would normally bind to, caffeine tricks the brain into feeling alert even when the body has accumulated significant sleep pressure. The effects, however, last far longer than most people realize. Because caffeine can remain active in the bloodstream for five to six hours, a cup of coffee consumed in the late afternoon may still be ③ interfering with the ability to fall asleep at midnight. Even when people do not consciously notice difficulty falling asleep, caffeine has been shown to ④ reduce the amount of deep, restorative sleep obtained later in the night. For this reason, many sleep specialists advise ⑤ avoiding caffeine after early afternoon.

After an especially demanding training session, the instinct to collapse onto a couch and remain motionless is understandable, yet exercise physiologists increasingly recommend the opposite approach. Active recovery involves performing low-intensity movement, such as a light jog, an easy swim, or a gentle bike ride, on days following intense exertion rather than resting completely, since _______________. Some athletes worry that any movement at all will interfere with the repair process, but research suggests that truly light activity does not meaningfully slow healing and may even reduce the perceived soreness that follows a hard session.

Travelers who cross several time zones in a single flight often arrive feeling exhausted, foggy, and strangely out of sync with the local clock, a condition widely known as jet lag. The discomfort arises because the body's internal clock continues to run on the schedule of the departure city even after landing. Realigning this internal clock to a new time zone is not instantaneous; researchers estimate that the body typically needs about one day to adjust for every time zone crossed. Flying eastward tends to produce more severe symptoms than flying westward, because _______________. Exposure to natural light at the right moments after arrival can help speed up the adjustment, since light is the strongest external cue the internal clock uses to reset itself.

Sleep apnea is a disorder in which breathing repeatedly stops and restarts during sleep, often because the muscles at the back of the throat relax too much and block the airway. (A) Doctors therefore rely less on a patient's own account of the night and more on objective measurements, such as overnight oxygen levels and airflow patterns recorded in a sleep laboratory. (B) Each pause can last from a few seconds to over a minute, and it may occur dozens of times in a single night without the sleeper ever waking up fully. (C) Because these interruptions rarely produce a clear memory the next morning, many people remain unaware that anything is wrong, even as chronic fatigue, headaches, and irritability build up over months.

Anyone who has ridden a bicycle after a decade away from one has likely experienced muscle memory firsthand: the body seems to recall a complex skill almost instantly, even when conscious memory of the exact movements has faded. (A) Interestingly, research also suggests that these neural pathways can remain partially intact even after long periods without practice, which is why relearning a skill is typically much faster than learning it for the very first time. (B) Contrary to what the name suggests, muscles themselves do not actually store memories; the phenomenon originates in the brain and nervous system, where repeated practice gradually shifts control of a movement from conscious regions to areas that operate largely automatically. (C) This shift explains why a skilled athlete can execute a complicated sequence of movements without consciously thinking through each individual step, freeing mental attention for strategy and decision-making instead.

This grogginess occurs because the brain has not fully completed a sleep cycle and is abruptly pulled out of its deepest phase. A short nap taken in the early afternoon, often called a power nap, can noticeably sharpen attention and mood without leaving a person groggy afterward. ( ① ) The key lies in timing: naps limited to roughly twenty minutes allow the brain to pass through the lightest stages of sleep while avoiding the deeper stages associated with slow-wave activity. ( ② ) If a nap extends much beyond that window, the sleeper risks waking during deep sleep, which produces a foggy, disoriented feeling known as sleep inertia that can persist for thirty minutes or more. ( ③ ) Laboratory studies comparing napping and non-napping groups have repeatedly shown that a brief nap improves reaction time and short-term memory almost as effectively as a full night of extra rest. ( ④ ) Interestingly, the benefit appears strongest when the nap occurs several hours after waking, since this is when the body's natural dip in alertness makes rest most effective. ( ⑤ ) For this reason, many workplaces now designate quiet rooms where employees can recharge briefly during the day.

This shift in emphasis reflects a growing understanding of what actually happens inside the body while an athlete is asleep. Coaches have traditionally focused athlete preparation on training volume and nutrition, but a growing body of research suggests that sleep deserves equal attention. ( ① ) During deep sleep, the body releases growth hormone, a substance essential for repairing muscle tissue damaged during intense training, while the brain consolidates motor skills practiced earlier that day into more stable, efficient patterns. ( ② ) Athletes who sleep fewer than seven hours a night have been shown to suffer more injuries, slower reaction times, and reduced accuracy compared to well-rested peers performing the identical drills. ( ③ ) Frequent travel across time zones compounds this challenge considerably, since jet lag can disrupt an athlete's natural sleep-wake cycle for several days after a long flight, sometimes right before an important competition. ( ④ ) In response, many professional teams now employ sleep specialists who design travel schedules, control bedroom lighting and temperature, and even adjust competition start times when possible. ( ⑤ )