How to document an ISAK assessment in practice
Step-by-step protocol: measurements, calculations, somatochart, and digital clinical record
The ISAK (International Society for the Advancement of Kinanthropometry) assessment is the reference standard for body composition in sports and clinical nutrition. Yet correctly recording all 17 measurements, computing the Heath-Carter somatochart, and linking results to the patient file in real time is one of the most common bottlenecks in practice.
What does the ISAK protocol measure?
Skinfolds (8): triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh, and medial calf.
Girths (5): relaxed arm, flexed arm, waist, hip, and calf.
Bone breadths (2): humerus and femur biepicondylar.
Heights and mass: stature, sitting height, arm span, and body mass.
Level 2 adds 4 skinfolds and 2 girths to refine segmental muscle mass.
Recommended measurement order
1. Landmark marking (dermographic pen, 30 seconds per point)
2. Skinfolds: proximal to distal, right side
3. Girths: larger to smaller segment
4. Breadths: with short-branch calliper
5. Heights and mass: stadiometer + calibrated scale
Repeat each measurement twice; if they differ by more than 5%, add a third. Record the mean.
Heath-Carter somatochart calculation
- Endomorphy (relative fatness): triceps + subscapular + supraspinale, corrected for height
- Mesomorphy (skeletal muscle mass): bone breadths + girths corrected for skinfolds
- Ectomorphy (linearity): ponderal index (height / ∛mass)
Reference values: endurance athletes ≈ 2-5-3; strength athletes ≈ 2-6-2; average sedentary ≈ 4-4-2.
Digital record vs. spreadsheet
1. Not linked to the patient's clinical file
2. No automatic somatochart or growth percentile calculation (paediatric)
3. No visual evolution between visits
Nutrition software with an integrated ISAK module solves all three: enter measurements once, and the system calculates, graphs, and stores the result in the file with date and responsible clinician.
Most common technical errors
Abdominal skinfold: measure 3 cm lateral to the navel, not over it. The caliper jaw axis must be horizontal.
Waist girth: at the end of a normal expiration, not maximal. Midpoint between the last rib and the anterosuperior iliac crest.
Bone breadths: the caliper must press on the bony epicondyles, not on soft tissue.
Clinical interpretation of results
- Body fat percentage (Yuhasz, Faulkner, or Jackson-Pollock depending on population): compare with reference values for the same age, sex, and activity level
- Appendicular lean mass index (ALMI): kg of appendicular muscle / height²; sarcopenia if < 7.0 (male) or < 5.5 (female) kg/m²
- Longitudinal evolution: the most useful indicator is not the absolute value but the change between assessments 4–8 weeks apart
Always record measurement conditions (time of day, hydration status, prior exercise) to make valid comparisons.
Recommended workflow in NutriManager
2. Enter measurements in the active session (the system guides the order)
3. Select the body composition formula by context (Sport / Clinical / Paediatric)
4. Review the automatically generated somatochart
5. Add clinical notes in the free-text field
6. Save: the system links data to the file, updates the evolution chart, and generates the PDF report in one click
Want to run ISAK assessments directly in the software?
NutriManager includes the full ISAK module with automatic somatochart, paediatric percentiles, and visual evolution between visits. Try it free for 30 days.
Frequently asked questions
Not legally required, but recommended. The Level 1 course (2 days) reduces TEM to < 5% and is the standard required in research and elite sport. For general clinical practice, mastering landmark marking and measurement technique is sufficient.
In elite athletes, every 4–6 weeks coinciding with training mesocycles. In clinical weight-loss nutrition, every 8–12 weeks. Shorter intervals do not capture significant changes and increase relative error.
The Harpenden is the reference standard (constant pressure 10 g/mm²). The Holtain and Slim Guide are validated alternatives for clinical use. The Lange caliper has higher inter-observer variability. Always calibrate before each session.
Yes, with adaptations. Paediatric percentiles are calculated using international (WHO, CDC) or national references depending on the population. NutriManager's paediatric nutrition module includes WHO 0–19 year tables.
In the digital file, consent is automatically linked to the patient during the onboarding process. For ISAK specifically, some centres add a clinical note stating that the patient authorises the somatochart photograph. Check the regulations of your professional association.