Open-water swimmers might think they’re ticking all the right training boxes but they could be putting themselves at risk of some serious health issues by not getting enough sleep, according to a new study from The University of Western Australia.

"Coaches might set training sessions at 5.30am or 6am, but for swimmers they also have to fit in their normal day, such as going to work and doing all of the usual things, and we found this significantly curtailed the amount of sleep they'd get."

Dr Ian Dunican, UWA Centre for Sleep Science

The study Understanding the sleep of ultra-marathon swimmers: guidance for coaches and swimmers which has been accepted for publication in the International Journal of Sports Science & Coaching measured the sleep of 24 masters’ swimmers (those aged 25 years and older) over 42 nights while training for a swim to Rottnest Island.

Lead author Dr Ian Dunican, Adjunct Senior Research Fellow from the Centre for Sleep Science at UWA’s School of Human Sciences, said a ReadiBand wrist activity monitor was used to track the sleep of the 11 men and 13 women and found when it came to quality shuteye, they weren’t getting enough.

“The swimmers in our study typically obtained less than the recommended seven- to-nine hours of sleep a night and more than a fifth of them had a high risk of obstructive sleep apnea (OSA), a potentially serious sleep disorder in which breathing repeatedly stops and starts,” he said.

Dr Dunican said body mass index was found to be associated with a decline in total sleep time, an issue exacerbated by the excessive high-energy diets often adopted by long-distance, open-water swimmers in the lead-up to an event, as they looked to increase body fat as protection against hypothermia.

“Each unit increase in Body Mass Index (BMI) was associated with five minutes less sleep per night,” he  said. “Higher BMI is a significant risk factor for the development of sleep apnea because as you put on weight your tongue size and the size of your neck grows which in turn causes difficulties with breathing while you sleep,” he said.

And if you’re a marathon swimmer who thinks the early bird gets the worm, think again. The study found that early morning training sessions were problematic when it came to healthy sleep practices, often not suiting the swimmers’ chronotypes (the time they would naturally wake up).

“Coaches might set training sessions at 5.30am or 6am, but for swimmers they also have to fit in their normal day, such as going to work and doing all of the usual things, and we found this significantly curtailed the amount of sleep they’d get,” Dr Dunican said.

The chronobiologist said the study, the first to investigate the sleep patterns of masters’ swimmers, is evidence that coaches need to consider the sleep behaviour and problems of competitors before they design training schedules with early morning starts.

“And swimmers need to safeguard their own health and support their recovery through doing everything they can to have between seven-to-nine hours sleep a night, including weight management to minimise the risk of a medical sleep disorder,” he said.

Alarmingly, the study also found that 21 per cent of the participants consumed alcohol “to hazardous and harmful levels”, leading the authors to ask whether further education was needed to help limit the potential negative effects of liquor consumption on sleep.