High intensity contraction/exercises

Fatigue in Intact Skeletal Muscle of Human Subjects During High Intensity Exercise 247 Muscle Metabolism During Electrically Evoked High Intensity Contraction 248... 

This categorization of relative whole body intensity is also valuable in distinguishing between high intensity and submaximal exercise. Exercise intensities or power outputs at or above 100% VO2 max are generally considered high intensity. These intensities require muscle contractions that generate -40-100% of the force... 

Myophosphorylase deficiency is the classic example of a carbohydrate-related dynamic syndrome. Affected persons are unable to mobilize glycogen therefore they cannot perform high-intensity work and must rely extensively on lipid metabolism. Several other defects of glycolysis produce similar symptoms. All are characterized by inability to do anaerobic work and to produce lactate during ischemic exercise, which is the basis for the customary screening test for these disorders. Patients are asked to perform maximal hand grip contractions at the rate of one per second for 60 seconds with the forearm circulation... 

At the onset of very rapid muscle contraction, ATP levels fall. This canses an increase in AMP concentration. Both phosphofructokinase and glycogen phosphorylase are sensitively stimnlated by AMP. After several seconds, glycogen phosphorylase becomes fully activated because of the arrival of epinephrine in the blood that stimulates the cAMP cascade. Epinephrine is rapidly secreted at the onset of high-intensity exercise and is a mediator of the fight or flight response. 

In summary, all mammals possess a large fraction of hlgh-oxl-datlve muscle. The ordered pattern of motor unit recruitment Involves these high oxidative muscle fibers before the low-oxldatlve fibers, as exercise Intensity progresses from mild, to moderate, to severe. This progression favors an enhanced exercise performance at submaxlmal exercise Intensities, since the slow and fast—twitch red fibers are capable of repeated contractions for long periods of time. 

---