28 male healthy subjects with no history of back pain, hernia or hypertension, volunteered to participate in a 16-week, three times/week, high-intensity resistance training study. Four groups were matched according to age, height, weight and maximal strength (1RM) in the squat exercise. One group trained using free weights (FW), two groups trained using the interim Resistance Exercised Device (iRED) and one group did not train and served as a control (CON). Of the two groups that trained with the iRED, one group trained with three sets (iRED3) and one group trained with six sets (iRED6).
At the end of the study there were no differences in 1RM values between the exercising groups. All exercising groups significantly increased in training intensity and 1RM for all exercises with exception of the squat exercise for the iRED6 group. Changes in local and total bone mineral content and density, as assessed by DEXA, were not consistent. No significant increases were observed at the end of the study, with the exception of bone mineral density in the lumbar vertebrae L4 for the free weight group. Significant increases in leg mass and lean tissue, were observed in all training groups at the end of the study, which was in agreement with significant increases in both thigh and calf muscle volume as assessed by MRI.
In conclusion, the 16-week resistive training program yields similar improvements in strength and muscular hypertrophy between training with free weights and training with the interim Resistance Exercise Device. Increasing the volume to 6 training sets does not elicit an additional training response. These results may be important in prescribing exercise countermeasures to prevent the adverse musculoskeletal changes associated with space flight.