Still leaning forward, I place the filled cup in the microwave. This stretches my arm through its range of motion, while using strength to hold the cup. Leaning forward is particularly useful. I do it every time I make tea, reach for something on my desk, brush my teeth and so on. Every time I lean forward, it's a type of sit-up. Although I'm not able to do 100 crunches in a row, I probably do about 100 sit-ups throughout the day. In fact, my abs are probably the best-developed muscles I have!