The structure of cyclocreatine is fairly flat (planar), which aids in passive diffusion across membranes. It has been used with success in an animal study, where mice suffered from a SLC6A8 (creatine transporter at the blood brain barrier) deficiency, which is not responsive to standard creatine supplementation.  This study failed to report increases in creatine stores in the brain, but noted a reduction of mental retardation associated with increased cyclocreatine and phosphorylated cyclocreatine storages.  As demonstrated by this animal study and previous ones, cyclocreatine is bioactive after oral ingestion   and may merely be a creatine mimetic, able to phosphorylate ADP via the creatine kinase system. 
All bets are off the table when high-dose testosterone and its many metabolites are used illegally, such as with anabolic steroid abuse. Strokes, embolisms, and cardiovascular disease are all more likely, as is sudden death, and liver and kidney disease. 44 In women, acne, irreversible deepening of the voice, baldness, increased facial hair, enlarged sex organs, breast reduction, depression, and infertility have all been reported. In adult men that abuse anabolic steroids, acne, baldness, permanent infertility, gynecomastia, loss of libido, erectile dysfunction, testicle shrinkage, and profuse sweating are all reported side effects. Increased testicular cancer hasn't been reported, though. 45,46
Alan: In the research I’ve collaborated on thus far, I unfortunately can’t report anything spectacular. In fact, it’s some of the most anticlimactic/unsexy results in the literature (LOL). However, in the most recent RCT of ours that’s in publication (PMID: 28070459), we did report individual data, and one of the subjects showed approximately an 18 mm gain in biceps thickness ( inches), measured via ultrasound, over an 10-week period. The rest of the subjects – all of whom were resistance-trained – stayed pretty much the same, which was not surprising since they were in hypocaloric conditions. It’s interesting to imagine what type of response this high responder would have if conditions were optimized for muscle growth, and/or supplementation was implemented. On the poor responder side, one of the subjects experienced a huge drop in quadriceps thickness (25 mm; about 1 inch) during this study. Interindividual response variability is just the nature of the beast, and a very poignant example of this is work by Ahtiainen et al (PMID: 26767377), who demonstrated vast heterogeneity in subjects’ responses to resistance training. Their study is openly accessible, have a look at this figure showing the full range of differences in strength & size gains (and losses): https:///pmc/articles/PMC5005877/figure/Fig4/. High responders gained 4-5 times the muscle mass of average responders. Of course there are the unfortunate subjects (2% of the subjects were classified as low responders) who included those who experienced losses in size and strength as a result of resistance training (and in my speculation, other factors as well).
While creatine's influence on physical performance has been well documented since the early twentieth century, it came into public view following the 1992 Olympics in Barcelona . An August 7, 1992 article in The Times reported that Linford Christie , the gold medal winner at 100 meters, had used creatine before the Olympics. An article in Bodybuilding Monthly named Sally Gunnell , who was the gold medalist in the 400-meter hurdles, as another creatine user. In addition, The Times also noted that 100 meter hurdler Colin Jackson began taking creatine before the Olympics.  
I hope it is apparent that the muscle memory phenomenon is a multi-faceted process with many different areas of the body having a different “memory” in relation to degree and timeframe. For example, following an eight-week detraining period, the overall quantities of various enzymes (such as citrate synthase) were increased compared to baseline levels. Further, myelination of axons has been a key area of interest in relation to skill acquisition and retention to form a memory. Thus, this article is only scratching the surface of the body-wide memory process and is only taking into consideration the cellular and molecular changes.
While creatine's influence on physical performance has been well documented since the early twentieth century, it came into public view following the 1992 Olympics in Barcelona . An August 7, 1992 article in The Times reported that Linford Christie , the gold medal winner at 100 meters, had used creatine before the Olympics. An article in Bodybuilding Monthly named Sally Gunnell , who was the gold medalist in the 400-meter hurdles, as another creatine user. In addition, The Times also noted that 100 meter hurdler Colin Jackson began taking creatine before the Olympics.