Exercise-Associated Postural Hypotension

During exercise, the leg muscles rhythmically squeeze the deep veins, the skeletal muscle pump, which returns blood to the heart against gravity and maintains venous return and cardiac output. The vessels in the skin and muscles are also widely dilated, to release heat and deliver blood to working muscle. When the athlete suddenly stops, particularly if they stand still at the finish, the muscle pump switches off while the vessels remain dilated, so blood pools in the legs, venous return falls, and cardiac output and blood pressure drop, producing light-headedness or collapse.

Impaired short-term control of blood pressure by the baroreflex after prolonged exercise adds to this, so the normal reflexes that would tighten the vessels and hold up the pressure on standing are blunted. Heat, dehydration and prolonged standing all make the pooling worse. The key point is that this is a transient problem of where the blood sits on stopping, rather than a failure of the heart or a dangerous metabolic disturbance, which is why it is usually benign and quick to correct.

The athlete typically becomes light-headed, faint or unsteady shortly after crossing the finish line or stopping. They are pale, may be sweaty and feel weak, but once laid down they are alert and orientated, recover quickly and can usually get up and walk after a short period. That rapid recovery with positioning, and the normal mental state, are what point towards a benign cause. A brief loss of consciousness can occur, but a true faint should prompt assessment for cardiac and other serious causes rather than being assumed benign.

The differential is the rest of the collapsed endurance athlete: exertional heat stroke, which combines brain dysfunction with significant hyperthermia, exercise-associated hyponatraemia, a low blood sodium often after heavy drinking, low blood glucose, and cardiac causes. Because the benign and serious pictures can look similar in the first moments, a few checks are used to exclude the dangerous causes rather than relying on impression alone.

The diagnosis is mainly clinical, resting on the story of collapse after stopping in an athlete who recovers quickly. The first priority is the airway, breathing and circulation, the mental status, the pulse and the blood pressure. Targeted tests are then guided by the picture rather than done routinely in every well athlete: the core temperature measured rectally when heat illness is possible, the blood glucose where indicated, and the blood sodium at the point of care when there is altered mental status, vomiting, a history of heavy drinking or poor recovery. A normal mental state, normal observations and a rapid recovery support the diagnosis. Where there are red flags, such as collapse during exercise, persisting confusion or an abnormal pulse, further assessment including an electrocardiogram (ECG) and hospital evaluation is needed. Investigations here are aimed less at confirming postural hypotension and more at ruling out what it must not be.

The mainstay is positioning, and it works quickly. The athlete is laid flat and the legs and pelvis raised above the level of the heart, which drains the pooled blood back to the heart, restores venous return and cardiac output, and usually settles the symptoms within minutes. This simple manoeuvre is the single most effective treatment.

Oral fluids can be offered if the athlete is alert, able to drink and it is appropriate, but fluid is not the main treatment, and large volumes should not be pushed, both because they are unnecessary and because of the risk of contributing to exercise-associated hyponatraemia. Intravenous fluid is rarely required and is avoided unless there is genuine, assessed loss of circulating volume, since reflexive fluid can do harm. The athlete is reassessed lying down before being helped gradually to sit, then stand, then walk, rather than getting up quickly. Throughout, they are monitored, and if they do not recover promptly with positioning, or if symptoms recur or any red flag appears, the working diagnosis changes and they are treated and investigated for a serious cause. Recovery from true postural hypotension is quick, so a slow or absent response is itself a warning.

Prevention is simple and worth teaching. Athletes should keep walking after they finish rather than stopping and standing still, continuing to move for a few minutes so the muscle pump keeps working, and should avoid standing motionless straight after hard exertion. A gradual cool-down helps, and staying reasonably but not excessively hydrated and getting out of the heat also reduce pooling.

Return to activity is usually prompt, since the condition is benign and self-limiting. It follows complete resolution of symptoms, normal observations and the ability to walk unaided, after which there is no need for prolonged restriction, and the main advice is on finishing technique for future events. Recurrent episodes, collapse during exercise or a true unexplained faint need medical and cardiac assessment before return.

• •Guidance on the collapsed endurance athlete sets out the central role of timing, the benign nature of most collapse after finishing, and the need to exclude heat stroke, hyponatraemia, hypoglycaemia and cardiac causes.
• •Event and endurance medicine resources describe the assessment, the positioning-based management and the caution around fluids.
• •Sports cardiology guidance informs the assessment of collapse where a cardiac cause is possible.
• •UK sports and endurance event medical resources support planning and triage at mass-participation events.

• •Exercise-associated postural hypotension, or exercise-associated collapse, is the most common and usually benign cause of collapse in endurance events.
• •Timing is a clue, not a diagnosis: after stopping favours it, but collapse during exercise should be treated as a serious cause until proven otherwise.
• •It is caused by loss of the leg muscle pump on stopping, with persistent vasodilatation and blunted baroreflex control, so blood pools and the pressure falls.
• •The athlete recovers quickly when laid flat with the legs and pelvis raised, which is the main treatment.
• •Prioritise airway, breathing and circulation and mental status, and check temperature, glucose and sodium when the picture indicates, not routinely.
• •Intravenous fluid is rarely needed, and large fluid volumes risk contributing to hyponatraemia.