Concussion Symptoms to Watch For and Return to Play

Research-informed explainer — last updated April 12, 2026

A concussion is a brain injury, and most people recover within 1 to 4 weeks with appropriate management. But certain symptoms are red flags for something more serious — and returning to sport or physical activity too soon is one of the most preventable ways to make a concussion worse or cause lasting harm.

This article covers the symptoms that warrant immediate medical attention, how concussion is diagnosed and managed, and what current research shows about return-to-play protocols. It draws on research from sports medicine physicians including one of the leading concussion researchers in the United States, whose work has changed how doctors think about activity after head injury [1][2].

What is a concussion?

A concussion is a traumatic brain injury caused by a bump, blow, or jolt to the head — or by a hit to the body that transmits force to the head. It temporarily disrupts normal brain function. You do not need to lose consciousness to have a concussion; in fact, most concussions do not involve loss of consciousness.

The injury causes chemical and physiological changes in the brain. These changes are not typically visible on standard CT scans or MRIs, which is why diagnosis relies on symptoms and clinical testing rather than imaging alone [4].

Signs and symptoms

Concussion symptoms span several categories and can start immediately after the injury or emerge over hours. They include:

Cognitive and mental symptoms

• Feeling slowed down, foggy, or "not right"
• Difficulty concentrating or remembering things
• Confusion about events before or after the hit

Physical symptoms

• Headache or pressure in the head
• Nausea or vomiting
• Dizziness or balance problems
• Blurred or double vision
• Sensitivity to light and noise

Sleep and mood symptoms

• Sleeping more or less than usual
• Feeling more emotional, irritable, or sad
• Fatigue

Most of these symptoms are expected in the first days after a concussion and typically improve with rest. What matters is the pattern: are symptoms improving, staying the same, or getting worse?

Warning signs that need emergency care

Some symptoms after a head injury require calling 911 or going to an emergency room immediately. These are signs of a more serious brain injury, such as a brain bleed, that cannot wait:

• One pupil larger than the other
• Extreme drowsiness or inability to be woken up
• Worsening headache that does not improve
• Repeated vomiting (more than once or twice)
• Slurred speech
• Seizures or convulsions
• Weakness or numbness in arms or legs
• Loss of consciousness that lasts more than a few seconds

These symptoms indicate that something beyond a typical concussion may be happening. Do not wait to see if they improve on their own.

How concussion is diagnosed

Doctors diagnose concussion based on the mechanism of injury (how the head was hit) and the presence of symptoms, combined with a clinical exam. Standard tools include:

• Symptom checklists: The athlete or patient reports which symptoms they are experiencing and how severe each one is.
• Cognitive testing: Short tests of memory, concentration, and processing speed.
• Balance assessment: Evaluating coordination and stability.
• Neurological exam: Checking eye movements, reflexes, and strength.

In some settings, a physiological treadmill test — called the Buffalo Concussion Treadmill Test — is used to assess autonomic nervous system function and help guide return-to-activity decisions [4]. This approach, developed at the University at Buffalo, identifies the heart rate threshold at which symptoms worsen during exercise and uses that threshold to design safe exercise protocols.

Standard CT or MRI scans are not part of routine concussion evaluation but may be ordered if there are warning signs that suggest a more serious brain injury.

Treatment options

Rest — but not complete rest

The previous standard was strict rest until all symptoms resolved. The research now tells a different story. A systematic review of randomized and observational studies found that prolonged strict rest does not speed recovery and may actually delay it, while structured activity within limits appears to help [3].

The updated approach is relative rest: avoid anything that significantly worsens symptoms (including heavy exercise, screen time in large doses, or cognitively demanding schoolwork), but continue light daily activity and gentle movement.

Early structured exercise

The most significant shift in concussion management over the past decade has been the move toward early, controlled exercise rather than waiting for symptoms to fully clear. Research published in JAMA Pediatrics tested early subthreshold aerobic exercise — activity kept deliberately below the heart rate where symptoms worsen — in adolescents with sport-related concussion within 10 days of injury. Participants in the exercise group recovered faster than those in the stretching-only control group, and the exercise was safe [1].

An earlier preliminary study found that the same approach — exercise kept below the symptom threshold — improved symptoms in patients with refractory post-concussion syndrome who had not recovered through rest alone [2]. Together, these studies reshaped how sports medicine physicians approach concussion recovery.

Targeted rehabilitation

Concussions do not all look the same. Some patients have predominantly physiological disruption; others have vestibular problems (balance and inner ear symptoms), vision problems (eye tracking, convergence), or cervical spine contributions from whiplash forces during the same impact. An evidence-based framework developed in part by University at Buffalo researchers categorizes these subtypes and matches them to targeted rehabilitation approaches — vestibular therapy for balance symptoms, vision therapy for eye tracking problems, and cervical physical therapy for neck-related symptoms [4].

Identifying which subtype is driving a patient's symptoms matters because the treatment is different, and treating the wrong mechanism adds time without benefit.

Return-to-play protocol

No athlete should return to sport before symptoms have resolved and a stepwise return protocol has been completed. All major sports medicine organizations, including those involved in preparticipation evaluation standards [6], support a gradual progression:

1. Symptom-limited rest: Only light daily activity until no symptoms at rest.
2. Light aerobic exercise: Walking, swimming, or stationary cycling at low intensity.
3. Sport-specific exercise: Running drills, skating, without head-impact activities.
4. Non-contact training drills: More complex movements and resistance training.
5. Full-contact practice: After medical clearance, normal training with contact.
6. Return to competition.

Each step takes a minimum of 24 hours. If symptoms return at any stage, the athlete drops back one step and waits until symptom-free again before progressing. Medical clearance from a healthcare provider familiar with concussion management is required before the final step.

What specialists are discovering

Current research is focused on why some patients take weeks or months to recover while others bounce back in days. Physiological testing using exercise challenge has identified that autonomic nervous system dysfunction — specifically, the inability to appropriately regulate blood flow to the brain during exertion — is a measurable predictor of prolonged recovery in some patients [4]. This finding has practical implications: it means there may be a physiological basis for persistent symptoms beyond those expected from the initial injury, and that treating this autonomic dysfunction through carefully supervised aerobic exercise is a better approach than rest.

Work is also ongoing to understand how many concussions accumulate over a career of contact sport and what that means for long-term brain health. Sports medicine's approach to preparticipation evaluation has evolved to include individual risk assessment [6], and concussion management is one area where that careful, athlete-specific approach is most critical.

Questions to ask your doctor

• Should I go to an emergency room, urgent care, or a sports medicine clinic first? What does my symptom pattern suggest?
• Have my symptoms been getting better, staying the same, or getting worse since the injury?
• Do my symptoms suggest a physiological, vestibular, vision, or cervical problem — or a combination? Does that change what treatment I should be doing?
• Is a Buffalo Concussion Treadmill Test or similar physiological assessment appropriate for me?
• My symptoms have lasted more than four weeks. What evaluation and treatment approach makes sense at this point?
• How strictly do I need to limit screen time, reading, and cognitive activity during recovery?

The bottom line

Most concussions resolve within a few weeks with appropriate management. Early controlled exercise below the symptom threshold speeds recovery — strict prolonged rest does not. Return to sport should follow a supervised stepwise protocol, and no athlete should progress before symptoms have fully resolved and medical clearance is obtained. Warning signs like worsening headache, one enlarged pupil, repeated vomiting, or slurred speech need emergency evaluation without delay.