Cornelissen, V. A., Defoor, J. G., Stevens, A., Schepers, D., Hespel, P., Decramer, M., Mortelmans, L., Dobbels, F., Vanhaecke, J., Fagard, R. H., and Vanhees, L. Effect of creatine supplementation as a potential adjuvant therapy to exercise training in cardiac patients: a randomized controlled trial. Clin.Rehabil. 2010;24(11):988-999. View abstract.

A great analogy that I like is that the balance between training and recovery is like digging a hole. Each time you lift, you dig yourself deeper and make it harder to climb out of the hole. To get back out again, you have to fill in the hole to return to ground level, and the only way to fill it is with food and rest. If you overdo it in the gym by pushing too hard, you won’t be able to train as often or at a high capacity. Eventually, you’ll get injured.

While muscle growth is critical for bodybuilding, getting rid of extra fat is a necessity to improve your total physique. These supplements can help to increase your metabolism, forcing your body to burn away more of its fat stores. They can also slow down the digestion process to prevent excess fat and carbohydrates from entering the body and being stored.
Glycogen synthesis is known to respond directly and positively to cellular swelling. This was demonstrated in an earlier study, during which rat muscle cells were exposed to a hypotonic solution in vitro to induce cell swelling, which increased glycogen synthesis by 75%. In contrast, exposing these same cells to a hypertonic solution hindered glycogen synthesis by 31%. These changes were not due to alterations in glucose uptake, but are blocked by hindering the PI3K/mTOR signaling pathway.[112] It was later noted that stress proteins of the MAPK class (p38 and JNK) as well as heat shock protein 27 (Hsp27) are activated in response to increasing osmolarity.[113][114] Furthermore, activation of MAPK signaling in skeletal muscle cells is known to induce myocyte differentiation[115] via GSK3β and MEF2 signaling, which can induce muscle cell growth.[116][117]
The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".[185] They named the hormone testosterone, from the stems of testicle and sterol, and the suffix of ketone. The structure was worked out by Schering's Adolf Butenandt, at the Chemisches Institut of Technical University in Gdańsk.[186][187]
Sandow was so successful at flexing and posing his physique that he later created several businesses around his fame, and was among the first to market products branded with his name. He was credited with inventing and selling the first exercise equipment for the masses: machined dumbbells, spring pulleys, and tension bands. Even his image was sold by the thousands in "cabinet cards" and other prints. Sandow was a perfect "Gracilian", a standard of ideal body proportions close to those of ancient Greek and Roman statues. Men's physiques were then judged by how closely they matched these proportions.