Doing twenty identical problems in a row feels easy, but on exam day you first have to recognise which kind of problem you're facing. By alternating exercises, what researchers call interleaved practice, your brain also learns to pick the right method. Students trained this way scored clearly better on tests. Harder in the moment, more lasting afterwards.
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.