Present data was collected as a part of a larger bio-medical project (‘Health status of the stone mine/ quarry workers of Birbhum district, West Bengal’) conducted on Santal labourer groups of Suri sub-division of Birbhum district, West Bengal between December 2012 to June 2016. Cross-sectional data on strength (handgrip and back strength) and anthropometric measurements were taken from 536 healthy adult Santal labourers (i.e. wage earner in stone mines and agricultural sectors) of both sex (251 males, 285 females) aged between 18 to 65 years. The study was restricted to single ethnic group (i.e. Santal) in order to avoid possible ethnic/ genetic effect (if any) in respect of variables under study.
Santals are the third largest marginal (schedule tribe) community and distributed in most of the districts of West Bengal . They were classified as ‘Pre-Dravidian’ tribe. Their language, Santali belongs to the Mundari branch of Austro-Asiatic language family  and now they have their own script i.e. ‘Ol-Chiki’.
No statistical sampling were attempted for the selection of study participants. Individuals who persuaded to participate and voluntarily agreed with written consent were included in the present study without any bias. The research was conducted after prior approval from the Ethical Committee for the Protection of Research Risks to Humans, Indian Statistical Institute.
Strength data in terms of handgrip strength (on both hands) and back strength were collected through battery operated digital handgrip dynamometer and back strength dynamometer (manufactured by Takei Scientific Instrument Co. Ltd., Tokyo, Japan) respectively, following standard protocols for measurements.
In measuring handgrip strength, participants instructed to pull one arm of the dynamometer as close as possible with another arm fixed with palm, in standing position, using one's strength of a single hand. No part of upper or lower arm or hand may push against any object or any other part of the body. Handgrip strength measured in terms of scores observed on the dial of handgrip dynamometer and the highest score considered out of three satisfactory attempts. The measurements were taken on both the hands separately.
In case back strength, participants instructed to stand in erect posture on the base of the dynamometer with straight arms and fingers extended downward as far as possible towards thigh. The chain (bar attached to the chain) was then fixed with the instrument so that it becomes 1 to 2 inches below one’s fingertip. Then participant were asked to bent forward slightly, and pull the bar, which is attached through chain with the base of the dynamometer. The tests done consecutively three times and the best score was recorded.
The IBP basic list of anthropometric measurements were included like height, sitting height, weight, diameters (bi-condylar of humerus, bi-condylar of femur, bi-acromial and bi-iliac), circumferences (forearm, medial calf, chest, waist and hip) skinfold thickness (biceps, triceps, medial calf, subscapular and supra-iliac) as well as measurements on hand length and wrist breadth on both hands were taken using standard techniques and instruments . Further, body mass index (BMI), fat mass (in kg) and fat free mass (in kg) were calculated using following formulae-
Body Mass Index (BMI) = Body weight (kg)/ Stature (m.) 2
Surface area (SA) = 0.007466 ⊆Weight (kg) 0.425⊆ Height (cm) 0.725
Fat Mass (kg) = (Fat %/ 100) ⊆Weight (kg)
Fat Free Mass (kg) = Weight (kg) – Fat Mass (kg)
Due to the absence of written records of age in some of the individuals, the ages were estimated with reference to important local events and crosschecked with elderly individuals, which were further compared with the ages of individuals for whom age records existed.
Descriptive statistics computed for each variable under present study. Pearson’s correlation analysis performed between strength measurements and anthropometric measurements to understand the bi-variate relationship.
Canonical correlation analysis (CCA) performed to understand the overall relationship between strength (both grip and back strength as a whole) and anthropometric traits of an individual. CCA indicates the relationship between two sets of variables i.e. first set consists of strength measurements [viz. Right Hand Grip Strength (RHGS), Left Hand Grip Strength (LHGS) and Back Strength (BS)] and the second set consists of all anthropometric measurements and age. Age of the participant was considered in the analysis as it influenced both strength and anthropometric measurements. The analysis proceeds by collapsing each subject’s score on the variables in each set of variables into a composite score. The composite scores are derived in such a way that the relationship between two variable sets is maximized. Canonical correlation value is the bivariate correlation between two composite score. We consider first canonical function because it provides highest correlation value and can explain majority of variance of the depended set. Canonical loadings and cross-loadings value provides information about the most influential variables for each set, which influence the other sets.
All the statistical analyses have been done using SPSS software 16.0 (SPSS Inc., Chicago, IL, USA) and SAS software 9.0 (SAS Institute Inc., Cary, NC, USA).