A 1997 study in Nature compared the effects of sleep loss and alcohol on performance. After 17 hours awake, volunteers' hand-eye coordination was as impaired as with a blood alcohol concentration of about 0.05%. After 24 hours, it matched roughly 0.10%. Getting behind the wheel after an all-nighter is far from harmless.
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.