If you were on bed rest and you’re feeling sluggish or weak, there’s a good reason for that. Your body’s natural ability to regulate your blood pressure is out of practice after being horizontal so much of the time. Normally, when you stand up, your blood vessels respond by constricting to help move blood back up north, towards your head.
When those blood vessels are out of practice, this response takes a bit longer, which leaves you feeling faint when you stand up. The medical term for that is postural hypotension, and it can occur with any positional change, whether that’s sitting to standing or lying down to sitting. It may make you feel weak, dizzy, or lightheaded, and it can even result in a fall. Before you start an exercise program, it’s important to get your circulatory system working like it should again.
In a rare longitudinal study (where the same subjects are tested again years or decades later), researchers were able to show just how much bed rest affects the body. In 1966, a group of researchers put 5 healthy young men on bed rest for 3 weeks. The researchers took a variety of measurements to determine the immediate effects of bed rest on the men’s bodies. The men were then released to recover and get back to their normal lives.
Thirty years later, the same 5 men returned. This time, the researchers took measurements to determine the effects of 30 years of aging on their bodies. As it turned out, 3 weeks of bed rest in their 20s was harder on their bodies than 30 years of aging, particularly their bodies’ ability to transport oxygen to their muscles and their physical work capacity.1
Getting up again from bed rest is tough, and there’s a good reason for that. The negative side effects after bed rest are temporary, but it’s important to understand why it’s so hard to get moving again. Don’t get frustrated. Take it slow, listen to your body (and your doctor), and you’ll recover just fine.