If you stop getting the results you want after several weeks of working out, it's time to mix things up. You need to challenge or "confuse" your muscles often to keep them growing. You can do this by putting a twist on your basic moves. Do a biceps curl with a reverse grip, for example. Or find a bench for the step-up move shown here. Change up your workout at least every 4 to 6 weeks for the best results.

Compound exercises work several muscle groups at once, and include movement around two or more joints. For example, in the leg press, movement occurs around the hip, knee and ankle joints. This exercise is primarily used to develop the quadriceps, but it also involves the hamstrings, glutes and calves. Compound exercises are generally similar to the ways that people naturally push, pull and lift objects, whereas isolation exercises often feel a little unnatural.

Cornelissen VA, Defoor JG, Stevens A, Schepers D, Hespel P, Decramer M, Mortelmans L, Dobbels F, Vanhaecke J, Fagard RH, Vanhees L. Effect of creatine supplementation as a potential adjuvant therapy to exercise training in cardiac patients: a randomized controlled trial. Clin Rehabil. 2010;24:988–999. doi: 10.1177/0269215510367995. [PubMed] [CrossRef]
Synthesis primarily takes place in the kidney and liver, with creatine then being transported to the muscles via the blood. The majority of the human body's total creatine and phosphocreatine stores is located in skeletal muscle, while the remainder is distributed in the blood, brain, and other tissues.[17][18][20] Typically, creatine is produced endogenously at an estimated rate of about 8.3 mmol or 1 gram per day in young adults.[16][17] Creatine is also obtained through the diet at a rate of about 1 gram per day from an omnivorous diet.[17][18] Some small studies suggest that total muscle creatine is significantly lower in vegetarians than non-vegetarians, as expected since foods of animal origin are the primary source of creatine. However, subjects happened to show the same levels after using supplements.[21]