UPDATED 

Because a concussion impacts the brain's cognitive functions (those that involve thinking, concentrating, learning and reasoning), the four most recent concussion guidelines, ^[1,2,9-11] a number of recent studies,^{[3,12, 13, 16, 17, 18]} and the expert opinions of many clinicians involved in the assessment and management of sport-related concussion, recommend cognitive rest in the immediate period after injury to allow the brain time to heal and speed recovery.  

Physical rest 

An athlete should avoid strenuous activity until the athlete has no post-concussion symptoms at rest because physical activity may make symptoms worse and has the potential to delay recovery.  While strict bed rest is not necessary, and while the effect of physical activity on concussion recovery has not been extensively studied (indeed, there is some evidence to suggest that mild physical exertion may actually help concussion recovery, especially for those suffering from post-concussion syndrome), the consensus of experts recommends broad restrictions on physical activity in the first few days after a concussion, including:

• no sports
• no weight training
• no cardiovascular training
• no PE classes
• no sexual activity
• no leisure activities such as bike riding, street hockey, and skateboarding that risk additional head injury or make symptoms worse.

Cognitive rest

Just as an athlete recovering from a concussion needs to get physical rest, he needs cognitive (mental) rest as well.

Because a concussion impacts the brain's cognitive function (those that involve thinking, concentrating, learning and reasoning), not its structure, engaging in cognitive activities (in other words, engaging in activities that requires a great deal of thinking or paying concentrated attention) may make an athlete's concussion symptoms worse, and, as a 2014 study^[12] (discussed in greater detail below) finds, lengthy recovery time by from 2 to 5 times. 

As a result, many experts recommend that concussed student-athletes limit scholastic and other cognitive activities, at least in the first several days after concussion, to allow the brain time to heal.

Cognitive rest means:

1. Time off from school or work;
2. No or reduced homework;
3. No or limited reading;
4. No or limiting visually stimulating activities, such as computers, video games, texting or use of cell phones, and limited or no television;
5. No exercise, athletics, chores that result in perspiration/exertion;
6. No trips, social visits in or out of the home; and
7. Increased rest and sleep. ^[1]