So we're really trying to watch and care for each other where it comes to mental and physical fatigue.

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The physical fatigue testing takes months.

FORBES: Connect

People with anxiety disorders feel excessive or irrational worry and can have anxiety-related physical symptoms, such as fatigue, headaches, trembling, sweating, panic, and nausea.

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How people interpret some of the physical sensations of exertion or fatigue, such as buildup of lactic acid in muscle or increases in body temperature, can also influence whether they stick with an exercise routine.

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Some of the more common side effects of weight-loss surgery can be difficulty digesting starchy foods and protein, which can lead to other physical conditions including hair loss, fatigue, swelling and muscle weakness.

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Weathering fatigue is about serious physical preparation, too.

FORBES: Magazine Article

Scientists are confident they have found a physical cause for the controversial condition Chronic Fatigue Syndrome.

BBC: News | Health | Immune system blamed for Chronic Fatigue Syndrome

Even for people in top physical condition, that can cause a lot of strain and fatigue.

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The symptoms of ME include chronic fatigue, muscle pains and migraine, but in extreme cases patients can develop a permanent physical disability.

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