Creatine is used up as energy during high intensity exercise. Due to this usage, the amount of glucose required from glycogen is decreased a bit. This both preserves glycogen concentrations in skeletal muscle and reduces lactate production, which is produced when glucose is oxidized for energy. There do not appear to be any alterations in the bioenergetic status of muscle cells during low to moderate intensity exercise.
Phosphocreatine is known to be a major source of energy for cardiac tissue alongside fatty acids, which are dominant under periods of normoxia (normal oxygen) while phosphocreatine becomes more important in periods of hypoxic stress.[281][282][283] The entire CK system plays a role in the recovery of the heart following ischemic/hypoxic stress, since blocking CK activity impairs recovery[284][285] and overexpressing CK activity promotes it.[286] This is due to the heart tissue needing high energy phosphate groups at this time, and the ischemic stress reduces CK activity and the ability of CK to donate these groups.[287][288]
Most experts recommend starting with your larger muscle groups and then proceeding to the smaller muscle groups. The most demanding exercises are those performed by your large muscle groups and you will need your smaller muscles to get the most out of these exercises. But, don't feel limited by that. You can do your exercises in any order you like and changing the order is a great way to challenge yourself in different ways.
Once training is resumed under these conditions, there may be little in the way of caloric support to ensure that protein synthesis and muscle growth occurs. Muscle may even begin to cannibalize itself as the body enters into a catabolic state. Even with the best of diets this can sometimes happen if training demands override the nutritional balance or imbalance.

It turns out yoga isn’t the only form of exercise that could strengthen your inner self. In fact, one study comparing the effects of hatha yoga and resistance exercise found that both activities improved mental health and wellbeing. Each group was less depressed, and the folks pumping iron enjoyed improved body image, too. “We know that all exercise improves mood,” explains Jeffrey A. Katula, PhD, associate professor of health and exercise science at Wake Forest University in Winston-Salem, North Carolina. “But I think resistance training provides something different emotionally to people.”
Over time, we naturally lose muscle mass in a process called sarcopenia. On average, men lose about 30% of their muscle mass during their lives. Usually, this begins in your 30s and progresses slowly as you age. But, don’t despair. You can rebuild and maintain muscle mass even as you age. Often, diet and exercise are enough. But, sometimes, if the above hormones play a role, your doctor may recommend medications and additional treatments (4).
Weight training also requires the use of 'good form', performing the movements with the appropriate muscle group, and not transferring the weight to different body parts in order to move greater weight (called 'cheating'). Failure to use good form during a training set can result in injury or a failure to meet training goals; since the desired muscle group is not challenged sufficiently, the threshold of overload is never reached and the muscle does not gain in strength. At a particularly advanced level; however, "cheating" can be used to break through strength plateaus and encourage neurological and muscular adaptation.
To meet the demands of a high-intensity exercise, such as a sprint, muscles derive their energy from a series of reactions involving adenosine triphosphate (ATP), phosphocreatine (PCr), adenosine diphosphate (ADP), and creatine. ATP, the amount of which is relatively constant, provides energy when it releases a phosphate molecule and becomes ADP. ATP is regenerated when PCr donates a phosphate molecule that combines with ADP. Stored PCr can fuel the first 4-5 seconds of a sprint, but another fuel source must provide the energy to sustain the activity. Creatine supplements increase the storage of PCr, thus making more ATP available to fuel the working muscles and enable them to work harder before becoming fatigued [1].

Moving through repetitions too quickly, going too fast; there is nothing gained by lifting weights fast. Some of the perks of lifting weight in a slow and controlled manner, include more total muscle tension and force produced, more muscle-fiber activation both slow and fast twitch fibers, and less tissue trauma. Remember, a joint is only as strong as the muscles that cross it; if you haven't lifted in a long time, or ever, be careful what you ask of your joints.
Another double-blind study supplemented with 18.75 g/day of creatine monohydrate for 5 days prior to high-intensity intermittent work to exhaustion, and then 2.25 g/day during testing. The workouts consisted of cycling to exhaustion using several protocols: (a) nonstop, (b) 60 seconds work/120 seconds rest, (c) 20 seconds work/40 seconds rest, and (d) 10 seconds work/20 seconds rest. Creatine supplementation significantly increased the total work time for all four protocols [13].
Collectively the above investigations indicate that creatine supplementation can be an effective strategy to maintain total creatine pool during a rehabilitation period after injury as well as to attenuate muscle damage induced by a prolonged endurance training session. In addition, it seems that creatine can act as an effective antioxidant agent after more intense resistance training sessions.