DEL DERECHO A NO SER DISCRIMINADO

Protocols published by the International Society for the Advancement of Kinathropometry (ISAK) were used where relevant (Norton & Olds 1996). All measurements were undertaken by the author, who is a trained level 3 ISAK Accredited (Instructor) anthropometrist. The authors’ known technical error of measurement (TEM) for skinfolds and circumferences were derived prior to the commencement of the study. From these repeated measures of 20 subjects TEM’s

are as follows: mid arm circumference =0.05cm (0.2%), tricep skinfold =0.1mm (0.74%), calf circumference =0.07cm (0.19%) and calf skinfold =0.11mm (0.93%).

The intraclass correlation coefficient (ICC) for these measurements was 1.0.

Midarm and calf circumferences were measured using a flexible steel tape measure (Lufkin W606PM). Tricep and calf skinfold thickness was measured to 0.2mm using Harpenden skinfold calipers. The Harpenden calipers were calibrated by Harpenden prior to commencing the study.

Anthropometric measurements were standardised to the right side of the body (Norton & Olds 1996) unless the presence of a fistula precluded this. Comparisons between the left and right sides of the body have shown that there is either no significant difference in skinfold thickness (Wormsley & Durnin 1973) or that the differences, although statistically significant, are of no practical significance (Martorell et al 1988). However, where any deviations or variations were made, these were noted to allow for the standardisation of subsequent measurements.

For comparative purposes, at recruitment, anthropometric data was contrasted to reference data of healthy individuals aged 50-59 years collected as part of the US National Health and Nutritional Examination Survey (NHANES) collected 1999-2002 (McDowell 2005). Whilst it is currently common practice in the UK to compare

anthropometric results with previous US NHANES data collected 1971-1974 (Bishop et al 1981) this data does not include norms for calf circumference and given the secular increase in BMI this earlier data was not considered applicable.

2.5.3.1 Mid arm circumference

Mid arm circumference (MAC) is considered to indirectly estimate fat and fat free mass. In combination with the tricep skinfold measurement it also allows the calculation of mid arm muscle circumference.

The point of measurement for MAC is the midpoint equidistant from the acromiale and radiale. Patients were asked to assume a relaxed position, arms hanging by their sides and with their shoulder girdle in a mid position in order to allow identification of the acromiale and radiale.

The acromiale is the point at the superior and external border of the acromion process of the scapula. This was located by the Investigator positioning themselves behind the right side of the patient. The Investigator palpated along the spine of the scapula to the corner of the acromion. The straight edge of a pencil was then applied to the lateral external border of the scapula to identify the most lateral part of the border of the acromion process. The most superior, lateral margin was located with the side of the thumb and marked with a hypoallergenic pencil.

The radiale is the point at the proximal and lateral border of the head of the radius.

This was located by the investigator again being positioned at the right side of the patient. The right thumb was used to palpate downward in the lower portion of the lateral dimple of the right elbow. If necessary, patients were asked to pronate or supinate their forearm to produce a rotary movement of the head of the radius. The position was then marked with a hypoallergenic pencil.

Once identified the linear distance was measured between the acromiale and radiale landmarks with the arm relaxed and extended at the side, avoiding any curvature surface of the arm. A horizontal mark using a hypoallergenic pencil was placed at the level of the midpoint between these two landmarks. The mark was then projected around to the posterior surface of the arm as a horizontal line (to allow the measurement of the tricep skinfold)

In order to obtain the MAC itself, patients continued to assume a relaxed position with arms hanging by their sides. The patient’s arm was abducted slightly to allow the steel tape measure to be passed around the arm. The tape was placed

perpendicular to the long axis of the arm when the subject was standing erect .The circumference was measured at the marked level of the mid-acromiale radiale.

Where necessary the above measurement was undertaken with patients in the sitting position, using a standard chair with no arms and a low back, but otherwise following the above protocol.

2.5.3.2 Tricep skinfold thickness

The tricep skinfold site is the most widely used single skinfold site for making an estimate of total fat mass stores operating on the assumption that subcutaneous fat stores at this point are representative of whole body fat stores (Brodie & Hutcheon 1998) However, in this study it was used to examine regional changes only.

The patient was asked to assume a relaxed position with the left arm hanging by the side. The right arm was also relaxed, but this time with the shoulder joint slightly externally rotated and the elbow extended at the side of the body.

The skinfold was raised parallel to the long axis of the arm at the site of the posterior mid-acromiale radiale landmark. The skinfold was grasped and lifted (raised) at the marked line so that a double fold of skin plus the underlying subcutaneous adipose tissue was held between the thumb and index finger of the left hand. The nearest edge of the contact faces of the caliper were applied 1 cm away from the edge of the thumb and finger. The measurement was recorded two seconds after the full pressure of the caliper was applied (Kramer & Ulmer 1981). This approach was used as adipose tissue is compressible and a constant recording time enables test/retest comparisons to be made while controlling for the known compressibility (Martin et al 1985). Two measurements were taken and the mean value recorded.

2.5.3.3 Mid arm muscle circumference

Mid arm muscle circumference (MAMC) is considered to be an estimate of fat free mass. It represents the circumference of the inner circle of muscle mass surrounding a small central core of bone (Gurney & Jelliffe 1973) and is derived from the measurements of MAC and TSF as follows:

MAMC (cm) = (MAC (cm) - (л x TSF (mm)).

It should be noted that the equation does not take into account inter-subject variation in the diameter of the humerus relative to the MAMC (Frisancho 1981).

Whilst this method is commonly used to reflect whole body FFM stores, in this study it was used to examine regional changes in FFM only.

2.5.3.4 Calf circumference

Calf circumference (CC) is an estimate of FFM and FM and as such is similar to MAC. In combination with calf skinfold measurement it allows the calculation of calf muscle circumference.

Patients were in a sitting position with feet separated. The right leg was positioned at a 90^o angle. The measurement was taken at the most medial aspect of the calf at the level of the maximal girth. The maximal girth was determined by using the middle fingers to manipulate the position of the steel tape in a series of up or down measurements to determine the maximum girth and marked with a small horizontal line on the medial aspect of the calf.

2.5.3.5: Calf skinfold thickness

Calf skinfold (CSF) is an estimate of FM and similar to TSF. The patient was asked to assume the same position used for the measurement of calf circumference. The calf skinfold, parallel to the long axis of the leg, was measured at the point of the maximal circumference on the most medial aspect of the calf as above.

The skinfold was grasped and lifted (raised) at the marked line so that a double fold of skin plus the underlying subcutaneous adipose tissue was held between the thumb and index finger of the left hand. The nearest edge of the contact faces of the caliper were applied 1 cm away from the edge of the thumb and finger. The measurement was recorded two seconds after the full pressure of the caliper was applied (Kramer & Ulmer 1981). Two measurements were taken and the mean value recorded. Like TSF it was used to examine regional changes.

2.5.3.6: Calf muscle circumference

Calf muscle circumference (CMC) is considered to be an estimate of FFM (similar to MAMC) and is derived from CC and CSF measurements above as follows:

CMC (cm) = (CC (cm) - (л x CSF (mm))

The above equation does not take account of inter-subject variation in the diameters of the tibia and fibula relative to the CMC. CMC was used to examine regional changes in FFM.