Isometric (overcoming) Training

[Jim_Jude]

NASA uses bands.

[Res Judicata]

The key here is time-efficiency. Isometrics have a place in specialized applications--as do other modalities like yoga, pilates, etc. But, ultimately, moderately to very heavy free weight exercises through the full range of motion are going to give you the benefit/time for strength training.

Elastic tools, like bands and springs, are useful for specialized applications because they change the force curve of the exercise or have a different force curved compared to simply resisting gravity. Machine pilates is based around springs, as are some specialized powerlifting training techniques. I can see elastic tools would be useful in space--it's the spring's elasticity that resisting the force generated by your muscles, not gravity.

[Bruiser]

Paul Vunak's opinion on it is echoed by Ross Enamait ( who I believe is an authority on strength)