Motion Sickness in the Athlete

Motion sickness arises from a sensory mismatch. The balance organs of the inner ear, the eyes and the position sensors of the body normally agree about how the head and body are moving, and when they disagree the brain interprets the conflict as a signal to feel unwell. The classic example is reading in a moving vehicle: the inner ear senses the motion of the car while the eyes, fixed on a stationary page, report that nothing is moving. The vestibular system of the inner ear is central to this, which is why the same conflict on a boat, in turbulence or in a fast-cornering car provokes symptoms. Susceptibility varies widely between people, tends to reduce with repeated exposure as the brain adapts, and is more common in those prone to migraine. Screens, simulators and virtual reality can produce the reverse conflict, where the eyes see motion that the body does not feel, which is increasingly relevant as these tools enter training.

The picture is familiar and builds over time. Early symptoms are often subtle, with yawning, drowsiness, apathy and a feeling of being off-colour, followed by pallor, a cold sweat, increased salivation, headache and nausea, and then vomiting if the motion continues. Symptoms usually ease once the motion stops or the conflicting inputs are removed. The diagnosis is clinical, made from the history of a clear motion trigger and a typical pattern, and no investigations are needed. The clinician's main task is to be sure the picture really is motion sickness and not a vestibular or neurological problem wearing its disguise, which is where the red flags matter.

Prevention comes first, and much of it works by reducing the sensory conflict. The traveller faces forward and looks at the horizon or a distant fixed point rather than at a screen or a book, and sits where the motion is felt least, at the front of a coach, over the wing of an aircraft or midship on a boat. Keeping the head still against a support, getting fresh air, avoiding heavy meals and alcohol beforehand, and taking small sips of water all help, as does slow, controlled breathing. For athletes exposed to the same provoking motion repeatedly, such as sailors, drivers and aviators, graded and repeated exposure builds real tolerance over time, and structured adaptation is part of preparation in these sports. Acupressure bands are popular but the evidence for them is weak, so they are reasonable to try but not relied upon.

When medication is needed it works best taken before travel. It may still help if taken at the very first symptoms, but absorption becomes unreliable once vomiting develops. Hyoscine hydrobromide, an antimuscarinic also known as scopolamine, and the sedating antihistamines such as cinnarizine, promethazine and cyclizine are all effective options, chosen according to the length of the journey, any contraindications and the side effect profile. Oral hyoscine is taken shortly before travel, while the hyoscine patch is applied behind the ear about five to six hours beforehand and can last up to three days. Durations otherwise vary, and the patch lasts longer than most oral antihistamines.

The side effects matter more for an athlete than for most travellers. Sedation impairs alertness, reaction time and coordination, which is critical for competition and for driving in motorsport, sailing and aviation, so any medicine is trialled well before competition and is not used before driving, flying or safety-critical sport if it causes drowsiness, dizziness or blurred vision. These drugs also carry antimuscarinic cautions, including angle-closure glaucoma and urinary retention, commonly cause a dry mouth and blurred vision, and interact with alcohol and other sedatives. On anti-doping, the common motion sickness medicines are generally permitted, but every medicine is checked before use, for example on Global Drug Reference Online, since some combination remedies can contain a prohibited substance. General antiemetics such as ondansetron are not reliably effective for motion sickness.

• •National Health Service (NHS) advice, British National Formulary (BNF) guidance and UK product information cover self-help measures and the use of hyoscine and antihistamines, taken before travel.
• •Systematic reviews, including Cochrane reviews of hyoscine and of antihistamines, inform the choice and limits of drug treatment.
• •Anti-doping resources, including Global Drug Reference Online, allow every medicine to be checked for its status in sport.
• •Advice is tailored to the sport and the individual, weighing the benefit of a medicine against its sedative effect on performance.

• •Motion sickness is a sensory mismatch between the inner ear, the eyes and the body, and susceptibility falls with repeated exposure.
• •Early symptoms are often drowsiness, yawning and pallor before nausea and vomiting, and they settle once the motion stops.
• •Confirm it is motion sickness, not a vestibular or neurological cause, especially with hearing loss, focal signs or a severe headache.
• •Prevention comes first: face forward, fix on the horizon, sit where motion is least, and use graded exposure in provoking sports.
• •Hyoscine and sedating antihistamines work best taken before travel, and absorption is unreliable once vomiting has developed.
• •Trial any medicine before competition, avoid driving or safety-critical sport if drowsy, and check every medicine for anti-doping status.