Lecture 2

NELSON MANDELA UNIVERSITY - HMSV392 Evaluation Methods II - Lecture 02: Equipment and the TEM

Anthropometry Equipment

  • Specific equipment is essential for taking measurements. The following tools are vital for an anthropometrist:

    • Stadiometer: Measures stature and sitting height.

    • Weighing Scales: Used for measuring body mass.

    • Anthropometric Tape: For measuring girths and locating skinfold sites.

    • Skinfold Caliper: For assessing body fat through skinfold thickness.

    • Anthropometer: Measures heights and lengths.

    • Large Sliding Caliper: Used for larger distances.

    • Segmometer: For segment length measurement.

    • Wide Spreading Caliper: Designed for specific body measurements.

    • Small Sliding Caliper: For small bone breadth measurements.

    • Anthropometric Box: Facilitates height and length measurements.

Stadiometer

  • Used to measure stature and sitting height; typically mounted to a wall for accuracy.

  • Features:

    • Should have a headpiece with a locking device.

    • Measurement range: 60 cm to 220 cm, accuracy to 0.1 cm.

    • Requires a level and hard floor for accurate measurement.

Alternative Methods when Stadiometer is Unavailable

  • Carpenters Tape: Fixed to the wall with a 90° head board.

  • Girth Tape: Similar setup as carpenters tape.

  • Laminated Graph Paper: Taped to a wall for height estimation using a head board (not acceptable in lab settings).

Weighing Scales

  • Beam Balance: Traditional choice, accuracy to nearest 100g.

  • Spring Balance Scales: Accuracy of 500g, must be regularly calibrated.

  • Electronic Scales: More convenient, accuracy to within 50g, should be calibrated using certified weights totaling at least 150kg.

Anthropometric Tape

  • Essential for measuring girths and locating skinfold sites accurately.

  • Specifications:

    • Must be non-extensible and flexible.

    • Should not exceed 7mm in width.

    • Must have a stub area of at least 4cm before the zero line.

    • Recommended length: at least 1.5m, calibrated in cm with mm gradations.

    • Regular calibration required, particularly for fibreglass tapes.

Skinfold Calipers

  • Maintain a constant closing pressure of 10g/mm².

  • Harpenden Calipers: Widely used, calibration up to 40mm in 0.2mm divisions.

  • Slim Guide Calipers: Alternative, calibrates to 80mm in 0.5mm divisions.

  • Caution advised when applying skinfold data from different calipers due to variations.

Anthropometer

  • Measures heights, lengths, and segment lengths directly.

  • Primarily for vertical heights, can also measure segment lengths, bone breadths, and stature.

Large Sliding Calipers

  • Upper segment of the anthropometer; measures large bone breadths.

  • Features two straight branches attached to a rigid scale.

  • Caution against incorrect assembly of calipers.

Segmometer

  • Comprises a steel tape with two straight branches (approx. 7cm in length) for direct segment length measurements.

Wide Spreading Calipers

  • Features recurved branches, ideal for measuring dimensions not suitable for straight branches due to anatomical constraints.

Small Sliding Calipers

  • Mitutoyo Adapted Calipers: Suitable for small bone breadths, dimensions include a minimum branch length of 10cm and accuracy of 0.1mm.

Anthropometric Box

  • Standard dimensions: +/- 40cm sides and height.

  • Facilitates measurement of heights, lengths, and breadths while seated.

  • Includes a cutout section for foot positioning.

Technical Error of Measurement (TEM)

  • Measurement variances are inevitable; reasons include:

    • Biological changes

    • Anthropometrist technique

  • Aim to minimize technical variability in measurements.

Key Concepts in Measurement Error

  1. Precision:

    • Variability in repeated measurements on the same subject.

    • High precision equals low variability.

    • Competent anthropometrists strive for precision.

  2. Reliability:

    • Alternative to precision; expressed as a correlation coefficient (Intraclass correlation coefficient, ICC).

    • Values range from 0 (no reliability) to 1 (perfect reliability).

  3. Accuracy:

    • Correspondence of the measured value to the real value, determined by a skilled anthropometrist.

  4. Validity:

    • The extent to which a measurement truly measures what it claims to.

Measures of Precision and Reliability

  • Technical Error of Measurement (TEM): Standard deviation of repeated independent measurements.

  • Comparison of TEM across different variables can be facilitated by converting to relative TEM (%TEM):

    • Formula: % TEM = (TEM / MEAN) x 100

Additional Notes on Measurements

  • TEM and ICC specifics:

    • Related to a particular variable, measuring technique, equipment, and tested population.

    • A minimum of 20 subjects and 2 trials recommended for accurate TEM and ICC determination.