Physiology practical- Measurement of skin fold thickness for medical & dental students with OSCE questions

1. Measurement of Skin Fold Thickness
Yapa Wijeratne
Faculty of Medicine
University of Peradeniya

2. MAJOR COMPONENTS OF BODY
▪ Bone
▪ Muscle
▪ Organs
▪ Fat
▪ Lean mass + Body Fat Weight = Body Weight
▪ Lean mass is made up of
▪ Muscle
▪ Bone
▪ Organs
▪ The component which can change most is muscle tissue.
▪ Therefore, if we monitor changes in body fat and total body weight
we can determine the change in muscle tissue.

3. ▪ How to measure body fat
▪ 2 methods:
1. Underwater weighing
▪ is available only in large facilities eg: hospitals
2. Skin fold caliper measurement
▪ easy to use
▪ reasonably accurate
▪ can be used at home
▪ Skin Fold Caliper: Measure the thickness of fold of skin
with its underlying layer of fat.

4. ▪ There are key locations of body, which have shown in research studies to he representative of
total amount of fat on the body.
▪ Because of key locations people can' t measure their own fat.
▪ Key locations:
▪ Vertical measurements
▪ 1. Back of upper arm (Triceps)
▪ 2. Front of upper arm (Biceps)
▪ Diagonal measurements
▪ 3. Below the shoulder blade on the back side (Subscapular)
▪ 4. Side of waist (Suprailiac)

5. Vertical Measurements
TRICEPS BICEPS

6. Diagonal Measurements
SUBSCAPULAR SUPRA-ILIAC

7. HOW TO MEASURE:
▪ Triceps: located halfway between shoulder and elbow joints.
▪ Fold is taken in a vertical direction directly on the center of back of the upper arm.
▪ If you are right handed, pull out the fold of skin with its underlying layer of fat with
your left hand. Don't worry about getting muscle as muscle is very firm & taut it
won't come out with skin & fat.
▪ Fold it over as shown in Figure.

8. ▪ Then holding the caliper in your right hand place the jaws of the caliper about
1/4" from fingers of your left hand which continues to hold the fold of skin.
▪ Completely release the trigger of the caliper so the entire force of the jaws is
on the skin fold.
▪ Do not release the fold of skin held in your left hand while taking the reading.
▪ Best to take all 4 reading & add together & with the aid of charts.
▪ % body fat is calculated.

11. ▪ If one location is only taken the best location is →the Back of upper arm.
▪ If two location are taken → Back of upper arm + subscapular region
▪ Ideal body fat % depend on
1. Age
2. Sex
3. Heredity
4. Type of sport - Swimmers perform better with higher % body fat.

12. Normal range of body fat %
▪ If the % body fat is close to the lower limit that person would be lean.
▪ It is desirable to have a body fat% close to the upper limit.
Age Up to 30 30-50 Above 50
Male 9-15% 11-17% 12-19%
Female 14-21% 15-23% 16-25%

13. Calculation of lean mass
▪ Eg: Weight =50kg
▪ Body fat % =12%
▪ Body fat weight =50 x 12/100
▪ =6kg
▪ Lean Mass = 50-6
▪ =44 kg

14. TEST YOUR KNOWLEDGE

15. OSCE STATION-1
1. Identify
2. What is the measurement taken by this instrument.
3. What is the unit of measurement (scale will be covered)
4. List key locations where the measurements are taken.
5. State 1 clinical use of this measurement.

16. ANSWER
1. Identify
1. Skin Fold Caliper
2. What is the measurement taken by this instrument.
1. Skin fold thickness
3. What is the unit of measurement (scale will be covered)
1. Millimeter (mm)
4. List key locations where the measurements are taken.
▪ Back of upper arm (Triceps)
▪ Front of upper arm (Biceps)
▪ Below the shoulder blade on the back side (Subscapular)
▪ Side of waist (Suprailiac)
5. State 1 clinical use of this measurement.
▪ Pre-operative assessment of nutritional state of the patients undergoing
surgeries- e.g. dysphagic patients waiting for oesophagectomies.

17. 1. Identify
2. 22 year old female is having skin fold thickness -20mm. Her weight is 50 kg. What
is her lean body mass.
3. Comment on your findings
(charts are provided)
OSCE STATION-2

18. ANSWER
1. Identify
1. Skin Fold Caliper
2. 22 year old female is having triceps skin fold thickness
-20mm. Her weight is 50 kg. What is her lean body mass.
 Select the correct chart & find fat % - 30%
 Fat mass = 50kg x 30% = 15kg
 Lean body mass= 50-15= 35kg
1. Comment on your findings
(charts are provided) Her fat mass is 30% & for her age that is above the upper limit of
normal range.
Age Up to 30
Male 9-15%
Female 14-21%

19. MCQ- T/F
▪ Key locations where the skin fold thickness measurements are taken includes
1. Back of upper arm
2. Front of upper arm
3. Below the shoulder blade on the back side
4. Inner aspect of the thigh
5. Side of waist
Answer : TTTFT