Many students have club practice early in the morning. But does it cut their sleep? Researchers in Australia studied 70 top athletes for two weeks. Before training days, the athletes went to bed earlier, but they got up even earlier.

So they slept less and felt more tired. In another study of 112 student athletes, those who slept less than eight hours were about 1.7 times more likely to have been injured.

Morning practice may look like a sign of hard work, but it can have a hidden cost. In 2014, Australian researchers asked 70 national-level athletes from seven sports to wear activity monitors and keep sleep diaries for two weeks. On average, they slept only about six and a half hours. Before training days, they went to bed earlier but woke up even earlier, so they slept less than before rest days.

On days with less sleep, they also felt more tired before practice. Teenagers may find this even harder, because their body clocks tend to shift later. A survey of 112 student athletes aged 12 to 18 found that those sleeping under eight hours were about 1.7 times more likely to have been injured.

Early morning training is often seen as a mark of dedication, but sleep research suggests it carries a hidden cost. In a 2014 study, Sargent and colleagues monitored 70 national-level athletes from seven sports for two weeks using wrist-worn activity monitors and sleep diaries. Average sleep was only about six and a half hours. Before training days, athletes went to bed earlier but woke up even earlier, so both their time in bed and their actual sleep were shorter than before rest days.

Shorter sleep was in turn associated with greater pre-training fatigue, and the researchers pointed to early start times as a key factor. For adolescents, whose body clocks naturally shift later, falling asleep early enough may be even harder. A survey of 112 athletes aged 12 to 18 at one American school found that those reporting less than eight hours of sleep per night were about 1.7 times more likely to have been injured.

However, these were observational studies. Sleep in the survey was self-reported, and injuries could disrupt sleep rather than the reverse, while training load may affect both. A review of 37 studies on elite athletes likewise judged the overall quality of evidence to be low.