How to measure arm span

The Suitability of Arm Span as a Substitute Measurement for Height

HLTH 501

David M. Barton

Abstract

Many anthropometric equations rely on individual height. Accurate height is not obtainable when various skeletal abnormalities exist. Arm span is proposed as a possible substitute for height. Thirteen subjects’ arm span and height were measured. The Pearson R for arm span and height was 0.96 (p<0.05). Regression analysis was used to build and equation predicting height from arm span (Height = 0.8655 x Arm Span + 9.3368). Results of this study show that arm span and height are strongly correlated and arm span can be used as a reliable predictor of height.

Introduction

In many medical, physiological, and human performance measurements the height of human subjects is used as a predictive and/or classification variable. Equations predicting Body Mass Index, pulmonary function, caloric expenditure, and body fat percentage are just a few of the many equations using height as a predictive variable.1 However, spinal curvature conditions such as kyphosis, scoliosis, lordosis, and kyphoscoliosis make it difficult to determine the correct height of the individual and thereby necessitating the need to identify a substitute anthropometric measurement.2

The need for an anthropometric measurement to serve as a substitute for height has long been recognized. One possible substitute measurement is arm span, that is – the distance from the left middle finger tip to the right middle fingertip of outstretched arms parallel to the ground. This relationship is notably shown in the drawing Vitruvian Man by Leanardo da Vinci (See Figure 1.).

Figure 1. Vitruvian Man by Leonard da Vinci.

image1.jpg

The purpose of this cross-sectional observational study was to determine if there was a significant relations ship between arm span and height to determine if a arm span could serve as a valid and reliable substitute for height.

Methods

Sample:

A convenience sample of 12 high school seniors and 1 senior high school teacher will be used.

Equipment:

Task Force Hand Tools 25 foot tape measure.

Measurements:

Each subject height (with shoes off) will be determined with the subject standing flat footed and with erect posture.

The arm span will be taken with arms outstretched, parallel to the ground, from the tip of the right middle finger to the left middle finger across the back.

All measurements will be recorded to the nearest ½ inch.

Statistical Procedures:

Mean, median, standard deviation, minimum and maximum will be calculated for the sample. Data will be examined for outliers.

Pearson product moment correlation was used to determine the magnitude and significance of the relationship between arm span and height.

Hypotheses tested:

Null Hypothesis: ρ (rho) =0 There is no significant relationship between arm span and height.

Alternative Hypothesis: ρ (rho) ≠0 There is a significant relationship between arm span and height.

Hypotheses tested at the 0.05 level of significance.

If a significant relationship between arm span and height is determined then regression analysis was used to derive an equation to predict height from arm span.

Data analysis and graph creation were accomplished using SPSS 20.0

Results

Arm span and height measurement are shown in Table 1.

Table 1. Raw data and correlation parameters

Student Name

Arm Span

(Inches)

Height

(Inches)

A

61.5

63.5

B

70.5

70.0

C

66.5

66.0

D

68.0

65.5

Dr. Barton

67.0

68.0

E

60.5

61.5

F

71.5

72.5

G

77.0

76.5

H

62.0

64.5

I

64.0

65.0

J

64.0

64.5

K

72.5

71.0

L

71.0

72.0

Descriptive statistics for arm span and height are shown in Table 2.

Table 2. Descriptive Statistics

ArmSpan

Height

N

Valid

13

13

Missing

0

0

Mean

67.38

67.73

Median

67.00

66.00

Mode

64

65

Std. Deviation

4.946

4.347

Variance

24.465

18.901

Skewness

.330

.582

Std. Error of Skewness

.616

.616

Kurtosis

-.625

-.439

Std. Error of Kurtosis

1.191

1.191

Range

17

15

Minimum

61

62

Maximum

77

77

Percentiles

25

63.00

64.50

50

67.00

66.00

75

71.25

71.50

Figure 2. Box plot of arm spam measurements.

image2.png

Figure 3. Box plot of height measurements.

image3.png

Correlation between armspan and height are shown in Table 3.

Table 3. Correlations

ArmSpan

Height

Spearman's rho

ArmSpan

Correlation Coefficient

1.000

.963**

Sig. (2-tailed)

.

.000

N

13

13

Height

Correlation Coefficient

.963**

1.000

Sig. (2-tailed)

.000

.

N

13

13

**. Correlation is significant at the 0.01 level (2-tailed).

Scatterplot of arm span and height is shown in Figure 3.

Figure 3. Scatterplot of Arm Span and Height

image4.emf

Results of regression analysis is shown in Table 4.

Table 4. Regression Analysis

r²

0.925

n

12

r

0.962

k

1

Std. Error

1.249

Dep. Var.

Height

ANOVA table

Source

SS

df

MS

F

p-value

Regression

191.8190

1

191.8190

122.98

6.11E-07

Residual

15.5977

10

1.5598

Total

207.4167

11

confidence interval

Regression output

95% upper

variables

coefficients

std. error

t (df=10)

p-value

95% lower

21.1675

Intercept

9.3368

5.3097

1.758

.1092

-2.4940

1.0394

Arm Span

0.8655

0.0780

11.090

6.11E-07

0.6916

Discussion

In an effort to determine whether or not a significant correlation between arm span and height, measurements were obtained from 13 “normal” subjects.

The results shown in Table 2 and Figures 2 and 3 indicate there were no outliers and that the data were almost normally distributed. Therefore all data were included in the statistical analyses.

Results of the correlation analysis in Table 3 indicate a significant (p<0.05) strong positive (r=0.925) correlation between arm span and height. This strength and direction of the correlation is further demonstrated by the scatterplot shown in Figure 3.

The significant correlation between arm span and height allowed for subsequent regression analysis, the results of which are shown in Table 4. The resulting regression equation is as follows:

Height = 0.8655 x Arm Span + 9.3368

The results of this study suggest that arm span measurement can be used as a substitute for height in normal subjects.

Limitations of this study include the small sample size, narrow range of arm spans and height, and the fact that all subjects were healthy and had no observable spinal curvature. Caution must be exercised in generalizing these results to populations other than described above.

1. Use of anthropometric measures to assess weight loss;George A. Bray,4 M.D., Frank L. Greenway,5 M.D., Mark E. Molitch,6 M.D., William T. Dahms,7 M.D., Richard L. Atkinson,8 M.D., and Kare

2. The use of arm span as a predictor of height: A study of South Indian Women SP Mohanty, S Suresh Babu and N Sreekumaran Nair Kasturba Medical College and Hospital, Manipal, Karnataka, India

�Introduction

�Methods

�Results

�Conclusion

�Foundation

�Need

�Historical refereence, not always necessary, but often of interest

�Type of study

�Purpose statement

�Summary statement

�Final conclusion

�Limitations of the study

�At least one reference required.