Lihaks

Lihaks is the Finnish word for muscle; in general usage it refers to the tissue in animals and humans that contracts to generate force. The term can appear in different cases in Finnish grammar (for example lihaksen or lihaksia), but in English-language texts the word muscle or muscles is used. In a broad sense, muscles consist of muscle fibers enclosed in connective tissue and supplied with nerves and blood vessels.

Muscles are classified into three main types: skeletal, smooth, and cardiac. Skeletal muscles attach to bones and enable voluntary movement; smooth muscles control internal organs and vessels; cardiac muscle makes up the heart. Each type has unique structure but shares the basic contractile apparatus of fibers arranged into sarcomeres.

Contraction is driven by the sliding filament mechanism: actin and myosin proteins slide past each other, powered by ATP and regulated by calcium ions released from the sarcoplasmic reticulum in response to nerve signals at the neuromuscular junction. A motor unit, comprising a motor neuron and the muscle fibers it stimulates, coordinates this activity.

Performance and growth: regular training induces adaptations such as hypertrophy, increased mitochondrial density, and changes in fiber type balance; recovery and nutrition, especially adequate protein intake, support these changes.

Common disorders and aging: strains, myopathies, and muscular dystrophies affect muscle function; aging causes sarcopenia, a progressive loss of mass and strength. Management includes exercise, balanced nutrition, and medical consultation as needed.