Resistance bands

they have graded resistance, weigh next to nothing and fit in your luggage, so you will not miss a workout even when travelling. Choose a set with several resistance levels right away — one band will cover only a fraction of exercises and as your strength grows, you will need more resistance. Inspect the band before every workout: a cut or cracked one can snap under tension and whip you. And never exercise in a way that the band could flick into your face if it snaps.