Isometric exercise provides a maximum amount of resistance based on the force output of the muscle, or muscles pitted against one another. This maximum force maximally strengthens the muscles over all of the joint angles at which the isometric exercise occurs. By comparison, weight training also strengthens the muscle throughout the range of motion the joint is trained in, but only maximally at one angle, causing a lesser increase in physical strength at other angles from the initial through terminating joint angle as compared with isometric exercise. In addition, the risk of injury from weights used in weight training is greater than with isometric exercise (no weights), and the risk of asymmetric training is also greater than with isometric exercise of identical opposing muscles.

It’s important to remember that since everybody is different, these estimates are just that. How the numbers work out for each person will definitely vary. So many factors—like genetics, hormones, sleep, and diet—can change the rate at which our bodies burn calories. And some people may have a harder time than others when it comes losing fat or gaining muscle—again, there are so many factors at play and our body chemistries are all different. Strength training is important for many, many, many other reasons (more on that later), but if you’re looking to increase your metabolism, it’s important to have realistic expectations and know that strength training can make a difference, but probably won’t drastically affect how many calories you burn from one day to the next.

One pilot study using 150mg/kg creatine monohydrate for a five day loading phase followed by maintenance (60mg/kg) for the remainder of the five weeks noted that supplementation was associated with fewer muscle symptoms and complaints alongside improved muscular function,[572] yet a later trial trying to replicate the obsevations using 150mg/kg daily for five weeks noted the opposite, that creatine supplementation exacerbated symptoms.[573] 
Carducci, C., Birarelli, M., Leuzzi, V., Carducci, C., Battini, R., Cioni, G., and Antonozzi, I. Guanidinoacetate and creatine plus creatinine assessment in physiologic fluids: an effective diagnostic tool for the biochemical diagnosis of arginine:glycine amidinotransferase and guanidinoacetate methyltransferase deficiencies. Clin Chem 2002;48(10):1772-1778. View abstract.
Yes, you can pack on size while only doing bodyweight exercises – I did it while traveling the world – and gymnasts train mostly with bodyweight movements. However, this can feel like playing Halo on Legendary difficulty. It can be done, but damn it can be challenging – especially for lower body movements. If your sole goal is to get bigger as fast as possible, access to a barbell for squats and deadlift is almost a requirement.
Without supplementation, creatine is formed primarily in the liver, with minor contributions from the pancreas and kidneys. The two amino acids, glycine and arginine, combine via the enzyme Arginine:Glycine amidinotransferase (AGAT) to form ornithine and guanidoacetate. This is the first of two steps in creatine synthesis, and although rare, any deficiency of this enzyme can result in mild mental retardation and muscular weakness.[28] AGAT is also the primary regulatory step, and an excess of dietary creatine can suppress activity of AGAT to reduce creatine synthesis[29] by reducing AGAT mRNA levels, rather than resulting in competitive inhibition.[30]
McArdle’s disease is a myopathy associated with impaired glucose release from glycogen and impairments in muscle function at times when glucose would be the primary energy substrate. Creatine is thought to be therapeutic, but has shown differing effects in the two trials so far (both benefit and worsening of symptoms) for currently unknown reasons.

One pilot study using 150mg/kg creatine monohydrate for a five day loading phase followed by maintenance (60mg/kg) for the remainder of the five weeks noted that supplementation was associated with fewer muscle symptoms and complaints alongside improved muscular function,[572] yet a later trial trying to replicate the obsevations using 150mg/kg daily for five weeks noted the opposite, that creatine supplementation exacerbated symptoms.[573] 

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