When athletes should drink, why napping helps you work, and how marriage hits your waistline

Athletes should drink only when thirsty: In this summer heat, you may be tempted to drink more than your thirst dictates. But new guidelines from an international expert panel published in the Clinical Journal of Sport Medicine advises to drink only when you're thirsty. Drinking too much water or sports drinks can lead to exercise-associated hyponatremia, say the 17-member panel led by Loyola University Medical Centre sports medicine physician Dr James Winger. Excess water causes sodium in the body to become diluted, leading to swelling in cells, which can be life-threatening. Symptoms of mild hyponatraemia include lightheadedness, dizziness, nausea, puffiness and gaining weight during an athletic event. Severe cases include vomiting, headache, altered mental status (confusion, agitation, delirium), seizure and coma. An athlete can safely lose up to 3 per cent of their body weight during a competition due to dehydration without loss of performance, Winger says.

Sleeping on the job? That's a good thing: Employees seeking to boost their productivity at work should take a nap, according to a new University of Michigan study. Napping, the researchers say, may be an effective strategy to counteract impulsive behaviour and to boost tolerance for frustration. The study's 40 participants, aged 18 to 50, maintained a consistent sleep schedule for three nights prior to undergoing lab tests. They completed tasks on computers and answered questions about sleepiness, mood and impulsivity. They were randomly assigned to a 60-minute nap opportunity or no-nap period that involved watching a nature video, before completing those questionnaires and tasks again. Those who napped spent more time trying to solve a task than the non-nappers, who were less willing to endure frustration to complete it. In addition, nappers reported feeling less impulsive.

Is marriage good or bad for the figure? Married couples on average eat better than singles, but they also weigh significantly more and do less sport. That is the finding of a new study by a team of researchers from Basel, Nuremberg, and Berlin published in the journal Social Science & Medicine. The researchers compared the body mass index of married couples with that of singles - a total of 10,226 respondents - in nine European countries. The average body mass index (BMI) of the single men in the study was 25.7; that of the married men was 26.3. For women, the average was 25.1 for singles and 25.6 for married women. In an average-height woman of 165 centimetres or an average-height man of 180cm, this seemingly small difference in BMI represents a difference of about 2kg. A normal BMI is between 18.5 and 25. Overweight is defined as between 25 and 30, and obesity as above 30.