Abstract
Long space flights will require astronauts to perform progressive resistance exercise, which is difficult to achieve in microgravity, to maintain skeletal muscle strength and bone mineralization. We assessed changes in knee extensor strength in 10 healthy men in response to a 10-week ground-based training program of concentric and eccentric muscle contractions as well as plyometric movements. Isokinetic knee extensor strength and vertical jump were measured before and after the training period, which involved a progressive resistance protocol of horizontal jumps and squats using the Shuttle 2000-1 Cardiomuscular Conditioner (Contemporary Design Inc., Glacier, WA). This device provides resistance by use of elastic cords attached to a movable sled positioned between two parallel runners on a fixed base. Both concentric and eccentric strength increased in the trained subjects relative to 10 untrained controls. Improvements in strength ranged from 21.5% for concentric contractions and 26.2% for eccentric contractions. We conclude that the Shuttle 2000-1 device effectively improved muscular strength.