For adults, a resting heart rate between 60 and 100 beats per minute is considered normal. In endurance athletes, it can drop to 40 or 50: their stronger heart pumps more blood with every beat. Take your pulse in the morning while calm. Watching it fall over the months reflects your progress.
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.