AESTHESUOMETRY TESTING

During all tests, distractions were kept to the absolute minimum, as subjects perform better if their concentration is not interrupted (Miron et al, 1989; Grabfield and Martin 1912). Night workers were tested on night 5 of the 7 night shift series, to allow the subject to become accustomed to the change in sleep pattern (Knauth et al, 1980; Âkerstedt, 1991). The majority of tests were made by the same observer (Merchut and Cone Toleikis 1990; Szabo et al 1984; Bell 1978), except for one that was carried out as a double-blind experiment.

Skin areas tested to sensory threshold

Areas of glabrous and hairy skin were tested. Sensory thresholds o f glabrous skin at the palmar and plantar areas of the hand and foot, and hairy skin of the dorsum of the hand, foot and inner arm were assessed. The points where the sensory stimuli were apphed within these anatomical divisions were determined in the manner outlined below:

• No marks were made on the skin for the touch and pin prick tests, but, heat stimulus points were marked on the skin, as dots with a felt tip pen.

• The anatomical areas to be tested were divided into notional test areas, following anatomical markers, such as skin creases, or the limit of weight bearing / non-weight bearing areas, as shown in the diagrams, and drawn on the record card as heavy lines. • With each area, a number of stimuli were delivered to equally spaced points, that

corresponded to the cells marked on the record sheet by the light lines (see Table 10, below).

• Mean sensory thresholds were calculated for each test time, for each area, as the average of the point (record cell) thresholds.

• Mean threshold of anatomical areas, eg: the medial longitudinal arch of the foot; the palm of the hand, were calculated as the mean of the data within that anatomical division.

Test areas on the foot:

The plantar sur6ce of the foot was divided equally into medial and lateral halves, to either side of a hypothetical longitudinal line that separates the non-weight bearing skin of the instep (the medial longitudinal arch, MLA) from the weight bearing skin of the lateral middle third of the sole of the foot (LLA), and extended from the centre of the heel, to the interdigital space between the second and third toes. Each half was subdivided into 3 zones, by hypothetical transverse lines at the distal weight bearing margin of the heel, and at the proximal limit of the ball of the foot (ie: the limits o f the instep), to designate the medial (MFF) and lateral fore foot (LFF) areas, and the medial (MH) and lateral (LH) heel areas. The plantar aspects of the toes (T) were taken as a single weight bearing area. Thus the plantar surfrce of the foot was

considered as seven areas: six of weight bearing skin, and one (ie: the MLA) of non weight bearing skin. The hmits of the test area on the dorsum of the foot (Dors F) were hypothetical transverse lines from the medial eminence of the 1st metatarsophalangeal joint to the lateral border of the 5th metatarsophalangeal joint, and from the tuberosity of the navicular on the medial side of the mid foot, to the proximal margin of the cuboid, on the lateral aspect of the tarsal area (Diagram 21).

T able 10:

Skin areas, and zones, assessed in the touch-pressure, pin prick, and beat pain threshold tests

Touch Pin

Prick

Heat

A rea Skin Type Test No: of No: of Exp. 1 Exp. 2

Areas zones zones Zones Zones

Foot Plantar Glabrous T 10 2

MFF 8 2 LFF 8 MLA* 8 8 8 4 LLA 8 8 MH 8 LH 8

Dorsum Hairy Dors F 16 1

Hand Palm Glabrous MP* 8 8

LP* 8 8

Fingers* 15

Dorsum Hairy D orsH 16

Arm Timer Hairy Volar 20

arm • Non-weight bearing glabrous skin

A bbreviations used to describe skin areas:

T Toes MFF Medial Forefoot

LFF Lateral Forefoot MLA Medial Longitudinal Arch

LLA Lateral Longitudinal Arch MH Medial Heel

LH Lateral Heel Dors F Dorsum o f the Foot

MP Medial (Radial) Palm LP Lateral (Ulnar) Palm

Dors H Dorsum o f the Hand Volar Arm Irmer Surface o f the Upper Arm

Fingers Volar Surfaces o f the Finger and Thumb

Test areas on the hand:

The palmar surface of the hand was divided to either side of the longitudinal palmar crease, into medial (MP) and lateral (LP) area. The palmar aspects of the fingers and thumb were each divided into zones, by the skin creases overlying the interphalangeal and metacarpophalangeal joints. The limits of the test area on the medial (MP) and lateral (LP) area. The palmar were

hypothetical transverse lines linking 2 -5 metacarpophalangeal joints, and the styloid process of the radius to the styloid process of the ulna (Wermer and Omer, 1970) (Diagram 22).

D iagram 21: SK IN TESTS SITES ON THE FO O T

PLANTAR SKIN SITES DORSAL SKIN SITES

RECORD CARD : PLANTAR TESTS RECORD CARD: DORSAL TESTS

Subject: Date: Time: R / L Subject: Date: Time: R / L

D iagram 22: SK IN TESTS SITES O N TH E H A N D

PALMAR SKIN SITES DORSAL (H) SKIN SITES

RECORD CARD : PALMAR TESTS RECORD CARD: DORSAL (H) TESTS

Subject: Date: Time: R / L Subject: Date: Time: R / L

Test areas on the arm:

The test area of the inner surface of the upper arm was defined by the limits of the proximal bulge of the biceps muscle transversely across the inner arm surfece to its outer border, and from the distal bulge o f biceps muscle to the outer border of the arm, parallel to the first line (Diagram 23).

Design of the Experiment, and Statistical Analysis

There is a wide variabihty within the range of normal thresholds to sensory stimuli, in any population. This can obscure within-subject diurnal variation of sensory thresholds, if group means are compared at repeat tests. The methodology of the experiments described below acknowledged this, and used subjects as their own controls. The subject’s sensory threshold, at any time, was calculated as the mean of a number of observations at the skin test site (eg: 58 at the glabrous - plantar - skin of the foot; 31 for the glabrous - palmar - skin of the hand). The diurnal variation of threshold, ie: the difference in threshold between tests made in the morning and repeated in the late aftemoon, was calculated as the subject’s threshold morning mean (time

1) minus the subject’s threshold late afternoon / evening mean (time 2). Group means were calculated as the mean of the individuals’ differences between timed tests.

For example, the mean plantar T-P threshold of a group of 16 normal subjects, calculated from a morning test, with a repeat test in the aftemoon was 3.9995 +/- sem 0.0539 Log units, with a standard deviation of 0.2158. This represented subject’s thresholds of between 3.6095 - 4.3476 log units. Within this global figure, the group moming threshold was 4.1284 +/- 0.0616 Log units, St dev 0.2463 (range: 3.5965 - 4.5695 log units), and the late aftemoon threshold was

3.8706 +/- 0.0517 Log unit, st dev 0.2069 (range: 3.6226 - 4.1781). But vdien the group’s moming - aftemoon mean, calculated as above, is examined, a robust diumal variation emerges: 0.2578 +/- 0.0360 Log units, st dev 0.1439. Whilst one subject within the group showed an insignificant rise in threshold of 0.0261 log units by the aftemoon, the remaining 15 subjects showed a very significant decrease in threshold of between 0.0870 - 0.4690 log units.

Randomisation was built into this basic method, where the areas within the anatomical sites were tested in random order, and the order of repeat tests (i.e.: am -> pm; pm -> am)was varied within the subject groups. These measures allowed paired data within the group (such as timed thresholds, left / right foot / hand, areas of different skin thickness, glabrous and hairy skin) to be analysed using repeat measures analysis of variance, and paired ‘t ’ tests. Where variables could not be directly paired (such as gender, test order, age, laterality, global analysis of site related thresholds) comparisons were made using single factor analysis of variance and 2- sample