Extract:
The Sleep Workout
Developing muscle growth is an effective way to stay healthy as we get older, but many people find it difficult to develop this muscle growth, even after modifying their exercise routine and food intake. What many people may not realize is that getting the proper amount of uninterrupted sleep plays a major role in the development of muscle.
The hard work of developing muscle is done in the gym, on a track, or on the court, but the actual growth takes places during the rest periods that follow a workout. Your body immediately begins rebuilding the muscle fibers that were broken down during the course of your workout. Much of this process is carried out while you are sleeping, so without a full night of sleep, muscle fibers will not have the opportunity to rebuild.
Human growth hormone (HGH) is an amino acid that is central to regulating metabolism, building muscle, facilitating calcium retention, and stimulating the immune system. The amount of HGH in your body spikes significantly during deep sleep, which makes getting at least 7 to 10 hours of sleep every night imperative to anyone hoping to develop additional muscle growth.
Recent studies have linked inadequate amounts of sleep to lowered levels of leptin, a hormone in the brain that controls appetite. Test subjects who received less sleep, or frequently interrupted sleep, would crave carbohydrates even after their caloric needs reached satiety. This can contribute to obesity and negatively affect any good habits people may have developed with regard to food intake.
What conclusion can the reader draw after reading this passage?
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A
Getting uninterrupted sleep is more important than getting enough sleep.
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B
Insufficient sleep may result in an increased risk for obesity.
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C
Human growth hormone is not essential for muscle development.
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D
Leptin is essential for building muscle.
A valid conclusion is that insufficient sleep may result in increased obesity risk, directly supported by the leptin disruption mechanism described.
A) Getting uninterrupted sleep is more important than getting enough sleep
The passage emphasizes both quantity ("7 to 10 hours") and quality ("uninterrupted," "deep sleep") as essential, never ranking one above the other or suggesting tradeoffs between them.
B) Insufficient sleep may result in an increased risk for obesity
Directly supported: inadequate sleep lowers leptin, causing carbohydrate cravings "even after caloric needs reached satiety," which "can contribute to obesity." The causal chain from sleep disruption to overconsumption to weight gain is explicitly established.
C) Human growth hormone is not essential for muscle development
Contradicted by the passage, HGH is described as "central to... building muscle" with its deep sleep spike making adequate rest "imperative to anyone hoping to develop additional muscle growth."
D) Leptin is essential for building muscle
Never stated, leptin regulates appetite; HGH builds muscle. The passage never connects leptin directly to muscle development, only to appetite control and obesity risk.
Conclusion
Valid conclusions must align with textual evidence without contradiction or unsupported extension. The sleep-leptin-appetite-obesity causal chain provides clear support for option B as a reasonable inference from presented mechanisms.