Strength and muscle

Muscle strength is the ability of muscles to produce force, and it is one of the most consistent physical predictors of survival. A meta-analysis (a study that pools the results of earlier studies) of 38 studies with about 1.9 million adults found higher grip strength associated with 31% lower all-cause mortality (death from any cause) and higher leg strength with 14% lower mortality [1]. The WHO recommends that adults do muscle-strengthening activity involving all major muscle groups on 2 or more days a week, in addition to aerobic activity [2].

Resistance training, exercise against a load such as weights, bands or body weight, is the main way to build strength. In a review of 16 prospective studies (which follow people forward in time), any muscle-strengthening activity was associated with about 15% lower all-cause mortality, with the lowest risk at about 40 minutes a week, and combining strength and aerobic exercise was associated with 40% lower mortality than doing neither [3]. Training also increases muscle mass, by about 1.1 kg of lean mass (body weight minus fat) on average in adults aged 50 and over [4].

Strength and muscle decline with age. At age 75, muscle mass is lost at under 1% a year while strength is lost at about 2.5% to 4% a year [5]. Grip strength, measured with a hand dynamometer (a handheld squeeze gauge), is the most widely used test of strength in population studies: in the PURE study, each 5 kg lower grip was associated with 16% higher mortality [6]. When strength and muscle fall low enough to impair function, the condition is called sarcopenia, which affects roughly 6% to 22% of older adults and is associated with about twice the risk of death [7, 8].