Fold bike. Grasping stem and seat post, bring to chest. Hold the bike with the drive side away from your body to avoid soiling your lovely bike clothes. Squat fully then return to an erect posture. Lift Brompton above your head until arms straight but not locked. Raise up on tip toes. Return to erect posture and lower bike to chest, then repeat. If this gets too easy, hold bike with one hand and squat on only leg, with palm on wall or furniture for balance. If still too easy, fill the front bag with bricks, or for an even greater challenge, many store bought fruitcakes, due to their depleted uranium density. Do this for 20 minutes and you will feel exercised. To restore carbs and sugars and to punish yourself for your many failures as a human being, eat all the fruitcakes. No other equipment needed. If core work is needed, hook your feet under heavy furniture and do sit ups holding the Brompton. You will not need a gym membership but maybe a hospital.