At least 26 participants in the Santa Barbara Half Marathon and 5K were taken to hospital after experiencing medical problems during or following Sunday's races. Santa Barbara County health officials said the illnesses were likely heat-related, although police are continuing to investigate the incident.

Cottage Health initially reported 19 patients with similar symptoms of undetermined cause. A subsequent update from Santa Barbara County's Public Health Department said 26 participants had been transported to hospital, including 19 to Santa Barbara Cottage Hospital and seven to Goleta Valley Cottage Hospital.

Santa Barbara Cottage Hospital alerted police after several runners sought treatment for unusual symptoms. The race began at 7am on Sunday with 7,500 registered participants, according to organisers.

Organisers Point to Heat Illness

Event director David Monico said a handful of people typically need hospital care after a long-distance race. He said warm weather could be a factor, as the medical team saw heat exhaustion, regular exhaustion and dehydration.

This year's number was higher than in the past, he said, though the field was also larger. He added that the medical team had not seen unusual symptoms or circumstances among those transported.

An organisers' spokesperson said there was no reason to believe anything unusual happened beyond typical heat-related illness or exhaustion. The hospital is still trying to determine whether the symptoms were caused by heat or other factors.

Monico also said much had been said and circulated on social media. He said police are doing their due diligence to see whether there is any truth behind it.

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How Heat Shapes Race Medicine

Chris Troyanos, the long-time medical coordinator for the Boston Marathon, said a race's medical surge capacity, the most athletes needing help at one time, is about 1 to 2 per cent of field size. That number climbs when a race is hotter or longer.

Dr William Roberts, medical director for the Twin Cities Marathon, said weather is the biggest factor in how many athletes need medical help. Medical encounters more than double in hot years, and heat-related issues rise sharply.

An American College of Cardiology analysis found that adverse medical events during endurance races increase considerably when wet-bulb globe temperature (WBGT) exceeds 60F (15.6C). The risk of exertional heat stroke is greatest when WBGT exceeds 82F (27.8C). No race-day WBGT readings have been reported.

Serious Conditions Experts Watch For

Running USA reported that the most common race issues are musculoskeletal, gastrointestinal or heat-related, including blisters, cramps, nausea and bloating. Both experts stressed that preparing for the most serious conditions matters more.

Exertional heat stroke is the most serious heat-related condition, with core body temperature rising above 104-105F and not coming down. Signs include disorientation, dizziness, collapse and nausea.

Exercise-associated hyponatraemia occurs when blood sodium levels fall below 135 mmol/L during or after physical activity. It can turn serious if symptoms are mistaken for dehydration and more water is consumed. Symptoms range from nausea and headache to seizures.

The analysis said symptoms of such conditions are not particularly sensitive or specific, and altered mental status is a hallmark of severe disease. It said altered mentation in warm, humid weather should lead to a heat stroke diagnosis until proven otherwise.

Laura LaMarche, a physical therapist at the University of Utah Runner's Clinic, said blood pressure drops rapidly when a race ends. She said this can cause dizziness, lightheadedness and, in some cases, collapse.

Roberts said that for every cardiac arrest he has handled, he has probably seen 10 exertional heat strokes and 2,000 to 3,000 exercise-associated collapses. He said cardiac arrest is rare, happening about once per 50,000 to 100,000 runners.

Officials have not detailed the symptoms, health risks or possible causes, and police have recommended no specific action for the public. Participants who feel unwell are urged to seek medical attention and follow guidance from doctors.

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