Lihasmassa

Lihasmassa, commonly translated as muscle mass, refers to the total amount of skeletal muscle tissue in the human body. It is a major component of lean body mass and is distinct from fat mass and bone. Lihasmassa can be expressed as mass in kilograms or as a percentage of body weight and is influenced by age, sex, and overall health.

Muscle mass changes through hypertrophy, the growth of muscle fibers in response to resistance training and sufficient protein intake, and through atrophy, which occurs with inactivity, aging, illness, or malnutrition. The process is regulated by protein synthesis signaling pathways, notably mTOR, and by hormones such as testosterone, growth hormone, and IGF-1. Aging is associated with sarcopenia, a progressive loss of muscle mass and strength that can affect mobility and independence.

Measurement methods include dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), magnetic resonance imaging (MRI), and computed tomography (CT). DXA is common in clinics and research, while MRI and CT provide regional detail but are more costly. BIA estimates can be affected by hydration status and recent activity.

Greater lihasmassa is linked to metabolic health, improved insulin sensitivity, and better physical performance, especially in older adults. Conversely, low muscle mass is associated with frailty, disability, and higher risk of adverse health outcomes.

To maintain or increase lihasmassa, a combination of resistance exercise and adequate protein and caloric intake is advised. General guidelines suggest protein consumption around 1.2–2.0 g/kg of body weight per day for adults, with higher targets for older adults or athletes, along with sufficient rest and recovery.