This cross-sectional and analytical study was conducted from August to September 2013 under Sports Sciences and Fitness Centre, North-East Regional Centre (NERC), Sports Authority of India (SAI), Imphal, India. Thirteen female and 19 male players among the field hockey trainees of NERC, SAI volunteered for the study. Due to limited availability of the trainees at the institute satisfying the study criteria, the sample size of the study was relatively small. Those players who were healthy and participated in any recognized national level competitions were included. Players who did not give informed and written consent, and found unfit during medical screening and pre-participatory physical evaluation were excluded. The study was approved by the Ethical Committee of the Institute.

All the players were instructed to report at 8 am to 9 am after a sound night sleep of eight hours and mild breakfast for testing [12,13]. Physical exertion was not allowed before 12 hours of the testing [14]. No heavy solid food or caffeinated drink was allowed before four hours of the testing [14]. They were made to relax and asked to empty their bladder at least 30-60 minutes before the testing [15]. After explaining clearly the purpose and procedures, each individual test was conducted.

Standing height (HT) and Sitting Height (SH) were measured using a Stadiometer (Holtain Ltd., Crymych, Dyfed, UK) and a 50 cm wooden box to the nearest 0.1 cm [16]. Body weight (BW), body composition variables {Fat Free Mass (FFM), percentage body fat (%BF)} and Body Mass Index (BMI) were measured using TANITA Body Composition Analyzer (TBF310 Model, Japan), which is based on a patented foot to foot pressure contact electrode using Bioelectrical Impedance Analysis technique [17,18].

The procedures outlined by ISAK (International Society for the Advancement of Kinanthropometry) were followed in recording structural dimensions and girths [13,19]. Segmometer (Rosscraft) was used for measuring segmental lengths {Acromiale-Stylion length (AS) and Midstylion-Dactylion length (SD)} and height {Trochanterion Height (TH)}. For measuring large and small breadths {biacromial breadth (AB), biiliocristal breadth (IB), biepicondylar humerus breadth (HB) and biepicondylar femur breadth (FB)}, large and small sliding calipers (Rosscraft) were used. A flexible and non-stretchable steel tape (Holtain Ltd.,) was used for measuring girths {relaxed arm girth (AG), mid-thigh girth (TG) and calf girth (CG)}.

Strength of each hand grip (left: LG and right: RG) and back (BS) was measured using a hydraulic handgrip dynamometer (Baseline Hand Evaluation set 12-0100, NY 10602, USA) and an arm-leg and back pull electronic dynamometer (Strength Evaluation System IMI-1429, Indian Medico Instruments, Delhi) respectively, following the standard procedures [16].

Seated shot put throw test (SP) was used to assess the speed, strength quality and power of the upper limb musculature, following the standard methodology [20]. The angle of shot put released was not controlled in our study. Strength quality and explosive power in the lower limb musculature was assessed by vertical jump score (VJ) [21-27], conducted following the standard methodology [28].

A sit and reach instrument (model-01285A, Lafayette Instrument Company, IN 47903, USA) was used to assess lower back and hamstring flexibility (F) following the standard methodology [29,30]. The level of feet was used as the zero mark.

Standard descriptive statistics were determined for the measured variables. They were categorized into: non-modifiable and modifiable parameters. Normality was assessed using Shapiro-Wilk test. Independent t-test was used for comparison between the genders. The relationships among various variables were studied using Pearson’s zero-order correlation and partial correlation, controlling for the effect of gender. Statistical significance was set at p-value (2-tailed)<0.05. SPSS (Statistical Package for Social Science) version 20 software was used for data analysis.

[Table/Fig-1] shows the descriptive statistics and also the comparison between female and male players. Significant differences (p-value<0.05) were noted in HT, AS, SD, AB, FFM, %BF, TG, LG, RG, SP, BS and VJ between the groups.

The association between the non-modifiable and modifiable anthropometric variables with strength and flexibility variables was studied by evaluating zero-order Pearson’s correlation r-values for the two groups. In order to study the association in the studied subjects as a whole independent of the effect of gender, partial correlation r-values were evaluated using gender as covariate. [Table/Fig-2,3] show the correlation r-values. After controlling gender, strength variables had significant positive correlation (p-value<0.05) with age (exception: VJ), HT, SH, AS (exception: RG and BS), SD (exception: RG and VJ), TH (exception: BS), AB, IB (exception: BS and VJ), DOT (duration of training; exception: BS and VJ), BW, FFM, %BF (exception: VJ), BMI (exception: VJ), AG (exception: VJ), TG (exception: BS and VJ) and CG (exception: BS and VJ). Similarly, F had significant positive correlation (p-value<0.05), after controlling gender, with age, HT, SH, BW and %BF.

Hockey is a game in which successful performance is influenced by anthropometric characteristics [1,2] apart from physiological [1,4-6] and skill variables. In our study, the males were taller, leaner and stronger with longer upper limbs and broader chests [Table/Fig-1]. The bulkier thigh of female players might be due to more fat deposition [31] or might be merely a coincidental finding. However, there was no significant difference as far as BMI and flexibility score were concerned between the two groups [Table/Fig-1]. As both the groups were of comparable ages, had similar habitual physical activity, and given similar training and diet for similar duration, the differences in both the groups might be due to gender specific physiology [18,32].

Strength [1,7,8,10] and sprint training [8-10] are very important in field hockey as many explosive activities [8,9] and repeated back-to-back sprints [8-10] are common in it. In our study, age and DOT had significant positive correlation with various strength variables (exception: BS with DOT; and VJ with age and DOT) and F (exception: DOT), when gender was controlled for [Table/Fig-2,3]. Also, with increasing age and duration of training, male players showed improvement in strength and flexibility [Table/Fig-2,3].

Grip strength is an important component in performing various skills involving hockey stick both in practice and competition. The mean grip strength of the studied players was lower than that of South African male players with grip strength of 54±8 kg [33]. After controlling for gender, [Table/Fig-2] shows that the players who were taller with longer trunk and lower limbs, and with broader chest and hip had stronger grip in both the hands. It was also more among the players who were heavier, leaner, and with bulkier arms and lower limbs [Table/Fig-3]. The players who had longer upper limbs had stronger left hand grip [Table/Fig-2]. In both groups of the players, the stronger grip was associated with longer trunk, broader chest, heavier and leaner body with bulkier arm, and interestingly, with more BMI [Table/Fig-2,3].

In field hockey, there is also much importance of upper body strength as it allows the players to shoot and pass the ball more powerfully and over a larger range of distance [13]. The upper limb power, as estimated by seated shot put throw score [20], was found to be more among the players who were taller with more trunk, limb and hand length, and broader chest and hip, after controlling for gender [Table/Fig-2,3]. The players who were heavier, leaner, and with bulkier arms and lower limbs also had stronger upper limbs. In both the groups also, body weight, FFM and BMI were associated positively with upper limb strength [Table/Fig-3].

Back strength, endurance and flexibility are important in field hockey as the field hockey players have to spend much time bending forward to the ground for maximum ground work [11]. After gender was controlled, back strength was found to be more for the taller players having longer trunk and hand, and with broader chest [Table/Fig-2]. It was also more among the players who were heavier, leaner and having bulkier arms [Table/Fig-3].

Strength quality and explosive power in the lower limb musculature as assessed by the vertical jump test [21-27] was found to be more among the players who were taller with more trunk and limb length, and with broader chest, when the effect of gender was controlled [Table/Fig-2]. Those players who were heavier and leaner also had more lower limb strength (non significant for females) [Table/Fig-3]. In both the gender groups, having broader chest was also associated positively with lower limb strength [Table/Fig-2].

For the lower back and hamstring flexibility, the study showed that those players who were heavier, taller with longer trunk were more flexible, after controlling for gender [Table/Fig-3]. A point to be noted is that those with more %BF were more flexible among the males and when both the groups were analysed as a whole after controlling for gender [Table/Fig-3]. However, among females, those with more BMI and %BF were less flexible, although statistically non significant. Weak significant and non significant positive correlations of flexibility score with BMI and %BF were reported earlier among young male soccer players [34], and adolescent female volleyball players [35].

Also, there was positive correlation between %BF and BMI with most of the strength variables (except for VJ). This finding might be explained, at least in part, by the positive correlation between %BF and BMI with FFM in our study {zero order correlation: (a) %BF and FFM: r=0.381, p=0.108 (male players); r=0.840, p<0.001 (female players) (b) BMI and FFM: r=0.667, p=0.002 (male players); r=0.938, p<0.001 (female players). Partial correlation, controlling for gender: (a) %BF and FFM, r= 0.517, p=0.003; (b) BMI and FFM, r=0.762, p<0.001. Not shown in the result section}. One study did report positive correlation between fat mass and fat free mass over the body fat range of 10 to 90 kg [36]. The finding of higher BMI with higher FFM and lower %BF has also been reported [37,38]. Hence, BMI should be cautiously used for indicating fatness among sports persons [18].

Our study thus showed statistically significant association of anthropometric characteristics over strength variables and flexibility score, which are known not only to have considerable impact over the game of field hockey [1,7,11], but also related to injury risk [39].

However, due to the cross-sectional nature of the study with non randomly selected small sample size from only one training centre of SAI, further well designed studies with sufficiently large sample size are required.

Our result showed that following non-modifiable anthropometric measures may be considered in selection of players for field hockey: standing height, sitting height, biacromial breadth, trochanterion height, acromiale-stylion length, midstylion-dactylion length and biiliocristal breadth. The most important modifiable anthropometric measures were related to body weight (BW) and composition (FFM and %BF), and hence appropriate training should be given to keep them under desirable range. Thus, the finding may be helpful for training monitoring, talent identification and selection of players for field hockey. The present study may also inspire for further large scale studies in the related field.