When is creatine phosphate used

However, the pool is very small and after a few muscle twitches will be exhausted. Phosphocreatine, also known as creatine phosphate, can rapidly donate a phosphate group to ADP to form ATP and creatine under anaerobic conditions.

Enough phosphocreatine is present in the muscle to provide ATP for up to 15 seconds of contraction. During periods of rest, the store of phosphocreatine is regenerated from ATP. Glycolysis is the metabolic reaction which produces two molecules of ATP through the conversion of glucose into pyruvate, water, and NADH in the absence of oxygen.

The glucose for glycolysis can be provided by the blood supply, but is more often converted from glycogen in the muscle fibers. If glycogen stores in the muscle fibers are expended, glucose can be created from fats and proteins. However, this conversion is not as efficient. Pyruvate is continually processed into lactic acid. With pyruvate accumulation, the amount of lactic acid produced is also increased.

This lactic acid accumulation in the muscle tissue reduces the pH, making it more acidic and producing the stinging feeling in muscles when exercising. This inhibits further anaerobic respiration, inducing fatigue.

Glycolysis alone can provide energy to the muscle for approximately 30 seconds, although this interval can be increased with muscle conditioning. While the pyruvate generated through glycolysis can accumulate to form lactic acid, it can also be used to generate further molecules of ATP.

Mitochondria in the muscle fibers can convert pyruvate into ATP in the presence of oxygen via the Krebs Cycle, generating an additional 30 molecules of ATP. Cellular respiration is not as rapid as the above mechanisms; however, it is required for exercise periods longer than 30 seconds.

Cellular respiration is limited by oxygen availability, so lactic acid can still build up if pyruvate in the Krebs Cycle is insufficient.

Cellular respiration plays a key role in returning the muscles to normal after exercise, converting the excess pyruvate into ATP and regenerating the stores of ATP, phosphocreatine, and glycogen in the muscle that are required for more rapid contractions. Muscle fatigue refers to the decline in muscle force generated over sustained periods of activity or due to pathological issues. Muscle fatigue has a number of possible causes including impaired blood flow, ion imbalance within the muscle, nervous fatigue, loss of desire to continue, and most importantly, the accumulation of lactic acid in the muscle.

Long-term muscle use requires the delivery of oxygen and glucose to the muscle fiber to allow aerobic respiration to occur, producing the ATP required for muscle contraction. If the respiratory or circulatory system cannot keep up with demand, then energy will be generated by the much less efficient anaerobic respiration. This improves performance during periods of intense muscle use, which results in increased muscle growth and greater strength.

The larger creatine phosphate pool also leads to a faster regeneration of ATP and therefore helps recovery after intensive exercise — at both the amateur and competitive level.

Skip to main content. How do muscles gain the additional energy? How is energy released into the muscle? How can creatine support muscle movement? What does creatine do? More categories All. You may also be interested in Is creatine harmful? Can creatine go bad? Creatine overview. Creatine phosphate can supply the energy needs of a working muscle at a very high rate, but only for about 8—10 seconds. Fortunately, muscles also have large stores of a carbohydrate, called glycogen, which can be used to make ATP from glucose.

But this takes about 12 chemical reactions so it supplies energy more slowly than from creatine phosphate. Oxygen is not needed — this is great, because it takes the heart and lungs some time to get increased oxygen supply to the muscles.

A by-product of making ATP without using oxygen is lactic acid. You know when your muscles are building up lactic acid because it causes tiredness and soreness — the stitch. Within two minutes of exercise, the body starts to supply working muscles with oxygen.

When oxygen is present, aerobic respiration can take place to break down the glucose for ATP. This glucose can come from several places:. Aerobic respiration takes even more chemical reactions to produce ATP than either of the above two systems.