Muscle is a longevity organ

In 2015, a study of nearly 140,000 people across 17 countries found that grip strength, measured with a dynamometer, was more strongly associated with the risk of death than systolic blood pressure. This observational association makes strength a valuable marker of overall health, although it cannot, on its own, establish cause and effect. A dynamometer cannot replace a cardiovascular assessment. It does, however, measure something a blood test cannot reveal: the force we can produce.

Why call muscle a “longevity organ”? Because the role of skeletal muscles, the ones we contract voluntarily, extends well beyond movement. They help regulate glucose, support bone health and contribute to the body’s response to illness. Their strength also helps us remain independent.

Having muscle and being able to use it are not quite the same thing. Two people with similar muscle mass can differ in the composition of their muscle tissue, the force they produce and how quickly they can produce it. Walking, carrying a load or getting up from the floor depends on all of these dimensions.

To understand how to preserve muscle as we age, we first need to define what we are trying to preserve, how to measure it and what we can do about it.

Muscle strength, mass and quality

Muscle mass describes how much muscle we have. Strength also depends on how that muscle is built and used: its architecture, the fat within the tissue and the nervous system’s ability to activate muscle fibers all influence the force it can produce. The force produced by a given amount of muscle is one way to assess its quality. Two people with similar muscle mass can therefore have very different levels of strength.

Muscle power adds speed: it is the ability to produce force quickly, as when standing up from a chair or climbing stairs. Walking draws on the legs, but also on coordination and endurance. Mass, strength, power and the ability to move describe different aspects of muscle function.

This distinction is reflected in how sarcopenia, a muscle disease associated with aging, is assessed. European diagnostic criteria give priority to low muscle strength. Reduced muscle quantity or quality confirms the diagnosis; poor physical performance, such as slow walking speed, indicates its severity.

What muscle activity changes in the body

Metabolism: After a meal, insulin helps glucose enter muscle fibers. They use it to produce energy or store it as glycogen. When muscles contract, they also increase their uptake of glucose through mechanisms distinct from insulin’s action. Regular training then improves their sensitivity to insulin. Muscle activity thus influences how the body handles glucose both during exercise and in everyday life.
Bones: Muscles transmit force to the skeleton through tendons. These mechanical loads stimulate bone remodeling. In the LIFTMOR trial, 101 postmenopausal women with low bone mass were assigned either to a supervised program combining high-intensity resistance and impact exercises or to gentle exercises at home. After eight months, bone density and several measures of physical function had improved more in the first group. This weight-bearing training affected both bone health and physical ability.
Inflammatory response: Working muscle also sends signals to other tissues. It releases molecules known as myokines, including IL‑6. In a human experiment, administering IL‑6 increased levels of IL‑10 and IL‑1ra, two molecules that dampen certain inflammatory responses. These observations help explain how muscle contractions may contribute to the signals that regulate the immune response during exercise.
Illness and recovery: Muscle proteins provide a reserve of amino acids. During surgery or serious illness, the body draws on more of this reserve to meet its needs, including the production of proteins involved in tissue repair.

What weakens muscle with age

Aging changes both muscle and its nerve supply: The fibers that produce rapid efforts tend to shrink. Some of the motor neurons that activate them are lost, while fat may accumulate within muscle tissue. Strength, and especially the ability to produce it quickly, can then decline before a substantial loss of mass becomes visible.
Inactivity accelerates this process: Regular contractions, particularly against resistance, stimulate the renewal of muscle proteins. When muscles are used less, protein synthesis slows and fibers can shrink. A period of immobilization after an injury or illness intensifies this effect: the legs lose strength because they are barely bearing weight or pushing against anything.
Insufficient food intake limits muscle maintenance: Protein supplies the amino acids needed to renew muscle fibers; food must also provide enough energy to support that process and physical activity. Too little protein slows this renewal. Even when protein intake stays the same, eating too little relative to energy expenditure can reduce muscle protein synthesis. This is particularly relevant when demanding training is paired with insufficient food intake.

Preserving muscle as we age

Strengthen your muscles regularly. To maintain or gain strength, muscles need to work against resistance: bodyweight exercises, resistance bands, machines or free weights, depending on your level. As a movement becomes easier, you can gradually increase the load, the number of repetitions or the difficulty of the exercise. The WHO recommends working the major muscle groups at least two days a week. Early gains in strength can appear before any visible change in muscle mass: the nervous system is also learning to activate muscle fibers more effectively.
Build endurance. Brisk walking, cycling and swimming challenge the heart and lungs while muscles use oxygen to sustain the effort. Done regularly, these activities improve the ability to keep going and contribute to cardiovascular health and glucose regulation. The WHO guideline is 150 to 300 minutes of moderate activity per week, built up gradually from your current level.
Practice balance. Standing on one leg near a support, walking heel to toe or practicing changes of direction draws on coordination and leg strength. A few minutes, repeated regularly, can sit alongside strength and endurance work. For older adults, the WHO recommends activities that combine balance and strength at least three days a week to maintain physical function and reduce the risk of falls.
Eat enough protein and energy. After resistance exercise, the muscle renews more of its proteins. Amino acids from food provide the building blocks, while sufficient energy supports training and recovery. For a healthy adult who trains, 1.2 to 1.6 g of protein per kilogram of body weight per day is a reference point to adapt to individual circumstances. This requirement tends to increase after age 65, when 1.6 to 2.0 g/kg/day is often recommended to compensate for age-related anabolic resistance. Carbohydrates fuel exercise and replenish the glycogen stores used by muscles.
Make room for recovery. A workout challenges the muscle; adaptation continues afterward as it repairs and renews its proteins. Spacing out demanding sessions that work the same muscles, or alternating muscle groups, helps maintain the quality of each effort. Sleep and sufficient food intake also contribute to recovery.

What we can measure

Strength and physical ability can first be tracked through what we do: a load that becomes easier to carry, stairs we can climb without slowing down, a movement we can repeat. During training, recording loads, repetitions and movement quality helps show whether we are progressing or losing ground.

When a difficulty arises, tests can help define it more precisely:

Repeatedly standing up from a chair provides information about leg strength and function; walking speed measures physical performance.
DXA estimates the lean mass of the limbs, which is used as an approximation of muscle quantity.
Bioelectrical impedance provides another estimate, although its result varies with factors including hydration. Combined with physical tests, these measurements help distinguish a loss of tissue from a decline in strength or ability.

Bloodwork offers another perspective. It can help investigate fatigue or weakness and provide insight into the metabolic conditions in which muscles function:

Creatinine is primarily used to estimate kidney filtration, expressed as the estimated glomerular filtration rate (eGFR). Its concentration also depends on muscle mass; a recent intense workout or a meal rich in cooked meat can temporarily raise it. Low muscle mass can, conversely, lower it. These variations affect eGFR calculated from creatinine, so the same result needs to be read in light of a person’s body composition, habits and medical history. When the estimate remains uncertain, cystatin C can help refine the assessment of kidney function.
CPK, or creatine kinase, is an enzyme that enters the bloodstream when muscle fibers are damaged. It can rise after intense exercise, with muscle disease or as a result of certain medications, including statins. Symptoms and recent activity are essential to interpreting the result.
Fasting glucose measures blood glucose at a particular moment; HbA1c provides information about its average level over the past few months. Fasting insulin, considered alongside glucose, can add to an assessment of metabolic regulation.
Hemoglobin provides information about oxygen transport, and ferritin about iron stores. These results can help explain fatigue or reduced tolerance for exercise. Depending on symptoms, TSH, sometimes supplemented by thyroid hormone tests, or an assessment of vitamin D status may point to other contributing factors.

In conclusion

The study cited at the beginning puts a number on something tangible: the strength we have matters as the years pass. It allows us to carry out everyday tasks and provides a reserve when illness or immobilization diminishes our abilities. At the same time, active muscle helps regulate glucose and maintain bone health; its proteins can be mobilized when the body needs them.

Taken together, these functions make muscle a longevity organ. Preserving muscle mass matters alongside maintaining strength and the ability to move. Strength training, endurance activity, sufficient food and recovery all help. Everyday movements show us what we can still do, while bloodwork helps us understand factors that may hold us back.

Scientific references

American Diabetes Association (2026). Diagnosis and Classification of Diabetes: Standards of Care in Diabetes.
Brancaccio et al. (2007). Creatine kinase monitoring in sport medicine.
Church et al. (2021). Perioperative amino acid infusion reestablishes muscle net balance during total hip arthroplasty.
Cruz-Jentoft et al. (2019). Sarcopenia: revised European consensus on definition and diagnosis.
DeFronzo et al. (1981). Synergistic interaction between exercise and insulin on peripheral glucose uptake.
Deutz et al. (2014). Protein intake and exercise for optimal muscle function with aging.
Goodpaster et al. (2006). The loss of skeletal muscle strength, mass, and quality in older adults.
Kortebein et al. (2007). Effect of 10 days of bed rest on skeletal muscle in healthy older adults.
Leong et al. (2015). Prognostic value of grip strength: findings from the PURE study.
Morton et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.
National Kidney Foundation. Creatinine.
World Health Organization (2020). WHO guidelines on physical activity and sedentary behaviour.
Oxfeldt et al. (2023). Low energy availability reduces muscle protein synthesis in trained females.
Steensberg et al. (2000). Production of interleukin-6 in contracting human skeletal muscles can account for the exercise-induced increase in plasma interleukin-6.
Steensberg et al. (2003). IL-6 enhances plasma IL-1ra, IL-10, and cortisol in humans.
Watson et al. (2018). The LIFTMOR randomized controlled trial.

This content is provided for informational and educational purposes. It does not replace a medical consultation, diagnosis or treatment. The information presented should be adapted to your circumstances with a healthcare professional.