The retina has no pain receptors: you can damage it by staring at the Sun without feeling a thing, and the injury can be permanent. During a partial eclipse, the sliver of visible Sun is still bright enough to cause this solar retinopathy. Sunglasses are not enough. Only eclipse viewers certified to ISO 12312-2 make it safe.
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.