Skeletni mišići su vezani uz kosti i služe za njihovo pokretanje. Energija potrebna za rad potječe od kemijskih reakcija koje nastaju u mišićnim stanicama tijekom kontrakcije. U mišiću postoje zalihe gotovog ATP-a, a energija je pohranjena i u drugim oblicima, tj. energijom bogatim molekulama, čija se energija veze koristi u resintezi ATP, i na taj način iskorištava u mišićnom radu. U ovom radu objašnjeni su procesi proizvodnje energije tijekom mišićnog rada aerobnim i anaerobnim metaboličkim putovima, te su istaknute razlike među ovim procesima s obzirom na brzinu i količinu oslobođene energije. Prema dominaciji fizioloških procesa organizma, sportovi se dijele na anaerobne, aerobne i mješovite odnosno anaerobno-aerobne. Tijelo koristi energetske sustave tijekom vježbanja ovisno o intenzitetu i trajanju aktivnosti. Hranjive tvari koje metabolizmom daju organizmu energiju su ugljikohidrati, masti i bjelančevine. U radu su objašnjeni glavni mehanizmi metaboličkih procesa dobivanja energije iz hranjivih tvari.

The sceletal muscles are tied to the bones and serve to move them. The energy required for work originates from the chemical reactions that occur in the muscle cells during the contraction. In the muscles there are stocks of energy source ATP, and energy is also stored in other forms, ie energy rich molecules. The energy stored in them is used in resynthesis of ATP, and thus exploited in muscular work. This paper explains the processes of energy production which occur during the muscular work by aerobic and anaerobic metabolic pathways, and highlightes differences in these processes with regard to the rate and amount of energy released. According to the dominance of physiological processes of the organism, the sports are divided into anaerobic, aerobic and mixed or anaerobic-aerobic. The body uses energy systems during exercise depending on the intensity and duration of the activity. Nutrients that metabolize energy to the body are carbohydrates, fats and proteins. The main mechanisms of metabolic processes of obtaining energy from nutrients are explained in this paper.