How Much Muscle Is Enough? Lean Mass and Sarcopenia

Sarcopenia is the loss of muscle strength and muscle mass that comes with age, and it raises the risk of falls, fractures, disability, and losing independence. The amount of muscle in your arms and legs, called appendicular lean mass (ALM), is how guidelines measure the “mass” part. But the current definitions put strength first: weak muscles matter even before the mass is low.

This article is general information, not medical advice.

What Appendicular Lean Mass Is

ALM is the lean (fat-free, bone-free) mass of your arms and legs, which is mostly skeletal muscle. It’s usually measured by a DXA (dual-energy X-ray absorptiometry) scan, or estimated by bioelectrical impedance. Because taller people carry more muscle, it’s often divided by height squared to give the appendicular lean mass index (ALMI), in kg/m², the same way body mass index scales weight.

The Cut-Offs

The European Working Group on Sarcopenia in Older People (EWGSOP2) revised its definition in 2019, and the Asian Working Group for Sarcopenia (AWGS) updated its own the same year:

Measure	EWGSOP2, men	EWGSOP2, women	AWGS 2019, men	AWGS 2019, women
Grip strength	Under 27 kg	Under 16 kg	Under 28 kg	Under 18 kg
ALM	Under 20 kg	Under 15 kg
ALMI (DXA)	Under 7.0 kg/m²	Under 5.5 kg/m²	Under 7.0 kg/m²	Under 5.4 kg/m²

In EWGSOP2’s approach:

• Low strength (grip strength, or taking more than 15 seconds to rise from a chair five times) makes sarcopenia probable.
• Low muscle quantity as well confirms it.
• Poor physical performance as well, such as a walking speed of 0.8 m/s or less, makes it severe.

The cut-offs were set for older adults, from reference populations. For younger adults, a falling ALM over the years is more informative than any threshold.

Why Strength Comes First

EWGSOP2 moved strength to the front because weakness predicts poor outcomes better than muscle mass does, and it’s cheap to measure. A grip dynamometer takes a minute; see Why Grip Strength Is Worth Measuring.

What Keeps Muscle

• Resistance training. The World Health Organization’s guidelines recommend muscle-strengthening activity on two or more days a week for adults, and for older adults activities that also train balance.
• Enough protein and energy. Muscle is harder to keep during weight loss and illness.
• Staying active. Bed rest and inactivity cost muscle quickly in older adults.

Following It in Kaizora

Appendicular Lean Mass and Appendicular Lean Mass Index are metrics on the Body page, logged from a DXA report; Skeletal Muscle Mass and Total Muscle Mass come from smart scales, logged by hand or, for total muscle mass, synced from Withings. These are different quantities, so they’re kept apart. Grip strength for each hand lives on Fitness. Comparing ALM with grip strength on Correlations shows whether strength is keeping up with mass; see Comparing Metrics.

The Short Version

• ALM is the lean mass of your arms and legs; ALMI divides it by height squared.
• Low grip strength makes sarcopenia probable; low ALM or ALMI confirms it.
• European cut-offs for ALMI are 7.0 kg/m² for men and 5.5 kg/m² for women.
• Resistance training twice a week is the main defence.

Sources

• Cruz-Jentoft AJ et al., “Sarcopenia: revised European consensus on definition and diagnosis,” Age and Ageing 48, no. 1 (2019): 16–31. doi:10.1093/ageing/afy169
• Chen LK et al., “Asian Working Group for Sarcopenia: 2019 consensus update on sarcopenia diagnosis and treatment,” Journal of the American Medical Directors Association 21, no. 3 (2020): 300–307. doi:10.1016/j.jamda.2019.12.012
• World Health Organization, WHO guidelines on physical activity and sedentary behaviour (2020).