Skeletal Muscle Mass Index (SMMI): Females, Age 65-69
Skeletal muscle mass index (SMMI), also called skeletal muscle index (SMI), measures appendicular skeletal muscle mass (arms and legs) divided by height squared (kg/m²). It is a key diagnostic criterion for sarcopenia (age-related muscle loss), alongside grip strength and physical performance. Data are from Lee et al. 2020, a cross-sectional study of 390,565 White adults aged 40 to 69 from the UK Biobank. Muscle mass was estimated by bioelectrical impedance analysis (BIA). These norms apply to White British/European populations; other ethnic groups may differ (South Asian and Black adults tend to have lower and higher muscle mass respectively at the same BMI). Cutoffs for low muscle mass vary by consensus group. The European Working Group on Sarcopenia in Older People (EWGSOP2) uses <7.0 kg/m² for men and <5.5 kg/m² for women as low-SMMI thresholds.
Data source: Lee et al. (UK Biobank SMMI) About this study
Percentile Distribution (kg/m2)
| Percentile | Value (kg/m2) | Rating |
|---|---|---|
| 5th | 5.68 | Poor |
| 25th | 6.36 | Below average |
| 50th | 6.77 | Average |
| 75th | 7.27 | Above average |
| 95th | 8.81 | Excellent |
What these numbers mean for females aged 65-69
A score around 6.77 kg/m2 is typical (50th percentile) for females in this age group. Scores above about 7.27 kg/m2 fall near the 75th percentile or higher, indicating above-average performance. Scores below about 6.36 kg/m2 fall near the 25th percentile, about 75% of the reference population scored higher.
Percentiles show how common a value is, not whether it is healthy.