The most common though that I see in BJJ is the cervical sprain or strain. The cervical spine is the most mobile segment of the spine however it puts it at a high risk of injury. Cervical sprains/strains are soft tissue injuries. A strain is linked to muscle, while a sprain is linked to tendons.
However, for some people, effects are much shorter and they have to take modafinil 2X per day (albeit this is not that common). For other people, effects can last 20-24 hours. It all depends on how your body processes it.
The standard dosage is 200mg per day. However for patients with narcolepsy and sleep apnea, single dose in the morning works. People with shift work disorder must consume the medication one hour prior to their shift. Modafinil can be given up to 400mg to patients.