Association of Height and Arm Span in Young Healthy Subjects

Introduction: Height is used to calculate body mass index and body surface area which are used to interpret renal function test and pulmonary function test. Maximum vertical measurement of a person is the standing height. Arm span is the measurement between the tip of the middle finger of the right and left hands. Exact standing height of patients with abnormalities of disproportionate growth, spine deformities, skeletal dysplasia, limb deformities, amputated limb, pain, weakness or paralysis cannot be measured. In these conditions, arm span may be used to determine the height of a person. Objective: This study aims to determine the association of height and arm span among the medical students of Maharajgunj Medical Campus, Nepal. Methods: A cross sectional analytical study was conducted among medical students in Clinical Physiology Department of Maharajgunj Medical Campus from November 2020 to October 2021. Non-probability, convenience sampling method was adopted and a total of 110 participants were enrolled in the study including 55 males and 55 females. Pearson’s correlation coefficient was used to find the association between height and arm span. Simple linear regression test was also used to formulate the equations of height and arm span and data analysis was done using SPSS version 25. Results: A significant positive correlation was observed between height and arm span where the total participants had r-value=0.765(p=0.00), males had r-value=0.557(p =0.00) and female had r-value=0.778(p=0.00). Conclusions: A strong positive correlation was observed between height and arm span among the participants.


INTRODUCTION
Among the developing countries the burden caused by musculoskeletal disorders showed a rise of 60% from the year 1990 to the year 2010. 1 It was estimated that around 2.35 million people had musculoskeletal disease in Nepal in 2016. 2 There were 2.1 million elderly inhabitants in Nepal which is 8.1% of the population. 3 Body height is used to calculate body mass index and body surface area which are used to interpret renal function test and pulmonary function test. 4 Once puberty is attained length of long bones do not change. 5 Arm span is the measurement between the tip of the middle finger of the right and left hands which is measured in subjects standing straight against a wall with both hands abducted horizontal at 90 degrees. 6 Height and weight increase after birth as a process of physical growth. After the age of 19 years a person's height usually does not grow. 7 Loss of height is seen during the ageing process and begins approximately between the age of 30 years and 50 years. 8 The loss of height is caused by the postural changes, and decrease in size of the discs in the vertebral column. Clinical conditions like arthritis and kyphoscoliosis can cause difficulty in standing straight which can lead to inaccurate measurement in height. 9 Height of patients with disproportionate growth, spine deformities, skeletal dysplasia, limb deformities, amputated limb, pain, weakness or paralysis may not be measured accurately. 10,11

METHODS
A quantitative cross sectional analytical study was adopted for this study. Height was used as an independent variable whereas arm span was used as a dependent variable. The study was conducted in medical students in the department of clinical physiology of Maharajgunj Medical Campus from November 2020 to October 2021 after obtaining ethical clearance from the Institutional Review Committee of Institute of Medicine, Maharajgunj.
A convenience sampling method was used to collect the data. A total of 110 medical students between the age ranges 18 to 25 years participated in the study.
Participants who had skeletal deformities or physical disabilities or who could not stand erect or straighten their knees were excluded from the study. Written informed consent was taken from the participants after explaining about the research procedure. Pearson's correlation coefficient test was used to determine the association between height and arm span. A p value < 0.05 was considered statistically significant. Linear regression was used to formulate an equation of height and arm span and SPSS version 25 was used for data analysis.

RESULTS
A total of 110 medical students with 55 male and 55 female participants were enrolled in the study. The mean age and BMI were more among the male participants in comparison to their female counterparts as shown in table 1. Table 2 shows a significant positive correlation of height and arm span with a p value <0.001 was observed among the total participants. The male and female participants also showed a significant positive correlation with a p value <0.001 when analyzed separately.
The scatter plots shown in figure 1a and 1b show a positive association of height and arm span among the male and female participants respectively. The estimated equation formulated by simple linear regression for male participants was height = 132 + 0.25 × arm span and for female participants was height = 63.8 + 0.61 × arm span as shown in figure  1a and 1b respectively. figure 2 shows a positive correlation of height and arm span among the total participants. The estimated equation formulated by simple linear   In similarity to our study Rai et al, in 2015, India also reported similar results among 600 participants.

Scatterplot in
There was a significant correlation of height and arm span among the total participants r=0.921, p value = 0.0001 as well as among male and female participants. 15 Similarly, Mohanty et al, in 2001, India reported a significant positive correlation between standing height and arm span among the participants. The study also correlated the sitting height and leg length with arm span. 10 A study conducted by Steele et al, also reported similar results but mean arm span was wider than the height in female participants. 16 Similarly, a study conducted by Bjelica et al, in Montenegro, in 2012 also showed a significant positive correlation in both male and female participants. In contrast to this study the females had a shorter mean arm span compared to the height whereas the males had wider arm mean arm span compared to the height in a study done by Bjelica et al. 17 In similarity to this study, Zverez reported significant correlation of height and arm span among boys and girls. 18 Similarly Jamir et al, in 2013 Haryana reported a significant correlation of height and arm span. 19 Arm span could be considered to be used as an alternative measurement when an accurate height cannot be assessed. In certain conditions where a person cannot stand, amputees and patients with spinal deformities standing height cannot be measured. In these conditions arm span may be taken in consideration to measure the height as arm span can be easily measured and does not require highly trained personnel.
A larger sample size including a wider age range and multiple centers could give us a better estimation of height using arm span for the general population.

CONCLUSIONS
The study concludes that a significant positive correlation of height and arm span was observed among total participants. So, arm span may be taken in consideration to measure the height of an individual especially in conditions where a person cannot stand, amputees and patients with spinal deformities.