The WHO's WRIGHT project found that the risk of venous thrombosis, a clot that usually forms in the legs, roughly doubles after more than four hours of seated travel, whether by plane, car or train. The absolute risk stays low, around one case per 6,000 long-haul flights. To cut it further, the WHO advises moving your legs, working your calf muscles and walking up the aisle when you can.
Chlorine on its own is fairly gentle. But when it combines with urine, sweat and other grime from swimmers, it forms chloramines, which cause stinging eyes and that classic 'chlorine smell'. A well-kept pool barely smells at all. Shower before you swim and never pee in the water.
Muscle mass slowly shrinks with age, putting independence at risk. But in 1990, a study had nursing home residents aged 86 to 96 train their legs for eight weeks: their strength more than doubled. Muscle responds to training at any age. Getting up from a chair without using your hands is already an exercise.