India, May 5 -- Getting a full night's sleep is non-negotiable for maintaining a healthy lifestyle. However, it is the experience of many that sleeping for just four hours often leaves us feeling more energetic right after waking up.

Taking to Instagram on May 4, Dr Kunal Sood, a Maryland-based physician in Anesthesiology and Interventional Pain Medicine, explained why that happens, and what can be done about it.

According to Dr Sood, one may feel groggy after getting a full eight hours of sleep at night because of sleep inertia, which only takes place when one is in deep sleep.

Describing sleep inertia, Dr Sood stated that it is "a temporary state of sluggishness that happens when you wake up during deep sleep, also known as flowwave ...