Tibolone, also known as 7α-methylnoretynodrel, as well as 7α-methyl-17α-ethynyl-19-nor-δ 5(10) -testosterone or as 7α-methyl-17α-ethynylestr-5(10)-en-17β-ol-3-one, is a synthetic estrane steroid and a derivative of testosterone and 19-nortestosterone .   It is more specifically a derivative of norethisterone (17α-ethynyl-19-nortestosterone) and is a member of the estrane subgroup of the 19-nortestosterone family of progestins.     Tibolone is the 7α-methyl derivative of the progestin noretynodrel (17α-ethynyl-δ 5(10) -19-nortestosterone).  Other steroids related to tibolone include the progestin norgesterone (17α-vinyl-δ 5(10) -19-nortestosterone) and the anabolic steroids trestolone (7α-methyl-19-nortestosterone) and mibolerone (7α,17α-dimethyl-19-nortestosterone). 
It is advisable to use both high and low reps in your workout program if you are looking or build muscle, lose fat, or just enhance your overall physical fitness. Depending on the training outcome, some rep ranges are more optimal than others. According to fitness gurus, the best rep ranges to bring about the most radical changes in body composition for fat loss and muscle building, in terms of time-efficiency, safety and overall effectiveness possibly happen within the 6-12 rep range. Your specific goals will determine what ranges you should use.