Anthropometry and isokinetic strength in water polo: Are young players ready to compete on adult teams?

Abstract

BACKGROUND:

In countries where water polo is a minority sport, coaches often recruit young players to senior teams.

OBJECTIVE:

To explore whether young water polo players are ready to train and play with older players from a physical and strength perspective.

METHODS:

Forty-four adolescent and senior water polo players (20 women and 24 men) were evaluated on full anthropometry, absolute and relative isokinetic muscle strength of shoulder internal and external rotator muscles (60 and 240 ${}^{\circ}$ /s) and hand grip strength.

RESULTS:

The strength of the internal rotators was significantly greater than that of the external rotators in both sexes and age groups. Senior male players had significantly higher values for variables related to body size and absolute strength in these muscle groups compared to their adolescent counterparts but these differences were not observed among women.

CONCLUSIONS:

Adolescent female players but not male players may be physically prepared to compete and train with senior teams.

Keywords

Team sport body size adolescence strength training performance

1. Introduction

Water polo is a team sport played in four 8-minute sets, separated by 2- and 5-minute recovery periods, implying short intense efforts interspersed with incomplete recovery. The sport is practiced in an aquatic environment, and numerous grips, thrusts, and sometimes illegal punches occur during games [1]. Thus, water polo demands a high level of physical conditioning [2].

Similar to other sports, researchers have attempted to relate some anthropometric characteristics to performance and success in water polo. Male [3] and female [4] players on national squads are taller and heavier and also perform better in conditional tests than players of the regional league. Junior and senior players differ in anthropometric variables related to strength, such as weight, body mass index (BMI), muscle percentage, and muscle size, all of which are higher in senior players [5, 6]. Furthermore, positive correlations have been demonstrated between throwing velocity or ball speed and body height in young male players [7], body breaths in national squad adult players [8], and body height in female players [9]. Thus, some anthropometric characteristics, particularly stature and body mass, appear to be relevant in water polo performance.

Likewise, Idrizovic et al. [10] indicated that greater absolute strength of water polo players correlates with greater acceleration, which implies enhanced launch speed. The relationship between force and acceleration can be expressed as force $=$ mass $\cdot$ acceleration, thus emphasizing the importance of body mass in performance. Some authors [11, 12] have shown that water polo players are stronger than non-players, but they also observed that most athletes have a large imbalance of shoulder muscle groups that act antagonistically. Imbalance of the rotator cuff is demonstrated by the presence of strong internal rotator and adductor muscles compared to external rotators and abductors. In this way, isokinetic assessment is a valuable tool to evaluate muscular deficits and imbalances of antagonistic muscle groups [13].

Water polo is a minority sport in many countries. Consequently, clubs and coaches often struggle to find players, particularly adult players, due to study and work-related losses. Thereby, coaches frequently recruit young and adolescent players to play on senior teams. However, because younger players may still be undergoing growth and development, it could be hypothesized that either they are not ready to play at a senior level or that their performance could be inferior than that of older players.

Therefore, the objective of the present study was to determine if young water polo players are ready to train and play with adult players from a physical and strength perspective. We compared anthropometric measurements and isokinetic strength of adolescent and adult players who train together. Due to sex differences in growth between men and women, we studied these variables separately in male and female water polo players.

2. Methods

2.1 Participants

This study included male and female water polo players who competed, separated by sex, in the senior team, included cadet players (15–16 years old) and senior players ( $>$ 18 years old). Players with shoulder injuries were excluded from the study. This study included a total of 44 players (20 women and 24 men). Players trained four times a week for $\sim$ 2 hours each and played a match every season weekend. Measurements were performed in the mid-season. All participants were appropriately informed, participated, and signed a consent form. In the case of underage participants, parents and/or tutors provided signed consent. This study was approved by the Ethics Committee of the University of the Basque Country (UPV/EHU), and conformed with the Code of Ethics of the World Medical Association (Declaration of Helsinki, printed in British Medical Journal in 1964).

2.2 Procedures

2.2.1 Anthropometry

The following anthropometric variables were measured: weight (kg), height (cm), sitting height (cm), arm span (cm), leg length (cm), BMI, and weight (kg)/height ${}^{2}$ (m), which were calculated with a scale (HD – 314W, USA), height meter (HD – 314W, USA), and tape measure (Mannesmann, Germany). In addition, the following skinfolds were measured with calipers (Harpenden, UK): subscapular, triceps, biceps, iliac crest, supraspinal, abdominal, thigh, and calf (mm). We also measured elbow, wrist, knee, and ankle diameters (cm) with calipers (Holtain, UK) and relaxed arm, arm in flexion and tension, waist, hip, thigh, and calf perimeters (cm) with a tape measure (Mannesmann, Germany). All measurements were made by the same person, who was qualified by the International Society for the Advancement of Kinanthropometry (ISAK). Two measurements were taken for each variable, and the average was used for statistical analysis.

With the collected data, bone weight was estimated as:

Bone weight (kg) $=$ 3.02 $\cdot$ (height ${}^{2}$ $\cdot$ wrist diameter $\cdot$ knee diameter $\cdot$ 400) ${}^{0.712}$ , where stature and diameters are expressed in metres.

Fat percentage was calculated separately for men and women as:

fat % ${}_{\text{men}}$ $=$ [(triceps fold $+$ subscapular fold $+$ supraspinal fold $+$ abdominal fold) $\cdot$ 0.153] $+$ 5.783; or fat % ${}_{\text{women}}$ $=$ [(triceps fold $+$ subscapular fold $+$ supraspinal fold $+$ abdominal fold $+$ thigh fold $+$ calf fold) $\cdot$ 0.1518] $+$ 3.58. Fat weight (kg) $=$ Fat % $\cdot$ body weight/100 Muscle weight was calculated as: muscle weight (kg) $=$ [total body weight $-$ (fat weight $+$ bone weight $+$ residual weight)] $\cdot$ 100/weight, where residual weight was estimated according to the following formula: weight $\cdot$ 0.241, for men and weight $\cdot$ 0.209 for the women.

2.2.2 Isokinetic testing

Isokinetic testing of concentric internal (IR) and external (ER) shoulder rotation strength was performed while participants laid supine on an isokinetic machine (Humac Norm, USA), with the shoulder in 90 ${}^{\circ}$ of abduction, the elbow flexed at 90 ${}^{\circ}$ , the forearm in supination and the wrist in neutral position. The axis of rotation was aligned with the line extending from the olecranon process through the humerus to the acromion process, ensuring that the subject had a complete and safe range of motion. The range of motion was adjusted individually and defined as an arch of physiological movement without meaningful discomfort to the athlete [14] while the strengths of both muscle groups was measured at 60 and 240 ${}^{\circ}$ /s. Each test consisted of an initial warm-up, 2 sets of 5 repetitions each (with 20 seconds of rest between the series), and – 1 min of rest at the end of each test.

Before isokinetic tests, participants performed a standardized warm-up using PRO2 Sport Total Body ergonomics (SciFit, USA). Duration of the warm-up was 3-min at a force of 25 N and an intensity of 40 repetitions per minute, similar to a previous study of handball players [15]. In addition, participants used an EN-Tree P machine (Enraf Nonius, Netherlands) with pulleys and resistance directed by compressed air. Participants performed 3 sets of 15 repetitions of alternative IR and ER exercises, both at 90 ${}^{\circ}$ abduction [16]. From the isokinetic assessment we derived the peak moment (PM) and average power (AP) of IR and ER and their ratio (ER/IR). We also calculated the normalized strength and power, N $\cdot$ m $\cdot$ kg ${}^{-1}$ and Watt $\cdot$ kg ${}^{-1}$ , respectively).

2.2.3 Hand grip test

A hand grip test was performed with a digital grip dynamometer (Jamar Plus digital hand dynamometer, USA) with both hands. The dynamometer was adjusted to each athlete’s hand size. Participants stood with an arm parallel to the body in adduction and exerted a maximum contraction for 5 seconds. After a 30-second break, they performed the test with the opposite hand. All athletes performed the test twice for each hand, and the highest value result of both attempts was used.

2.3 Statistical analyses

Statistical analysis was performed using IBM SPSS Statistics software (v 22.0). Normality of the data was analyzed by Shapiro-Wilk test. The level of significance was established at $p<$ 0.05. Data are presented as mean $\pm$ standard deviation and percentages. Effect size of the measurements was calculated using Cohen’s d [17]. Threshold values to assess effect size were 0.1, 0.2, 0.5, and 0.8 for trivial, small, medium, and large effect sizes, respectively [17]. Differences between seniors and cadets and between men and women were analyzed using Student’s t-test (parametric variables) or Mann-Whitney U-test (non-parametric variables). Differences between IR and ER were analyzed using the paired sample Student’s t-test (parametric variables) or Wilcoxon test (non-parametric variables). The technical error of measurement was $<$ 0.5% for height and weight and within 2.4%–4.5% for skinfolds. Intra-class correlation coefficients of the variables were 0.971–0.994.

3. Results

3.1 Anthropometric characteristics

Male cadet players had significantly lower weight ( $p<$ 0.05), BMI ( $p<$ 0.05), subscapular skinfold ( $p<$ 0.05), relaxed arm perimeter ( $p<$ 0.001), contracted arm perimeter ( $p<$ 0.001), waist perimeter ( $p<$ 0.05), and muscle weight ( $p<$ 0.01) than senior players (Table 1). In women, there were significant differences between cadet and senior players in biceps skinfold ( $p<$ 0.05), and bone percentage ( $p<$ 0.05).

Table 1
Anthropometric characteristics (mean $\pm$ SD) according to the category in male and female players

	Men						Women
	Seniors		Cadets		d		Seniors		Cadets		d
Players ( $n$ )	17		7				10		10
Age (years)	23.67 $\pm$	6.16	15.58 $\pm$	0.57 ${}^{\ast\ast\ast}$	1.	85	24.17 $\pm$	5.07	15.31 $\pm$	0.61 ${}^{\ast\ast\ast}$	2.	45
Height (cm)	179.00 $\pm$	7.06	179.00 $\pm$	3.27	0.	00	165.60 $\pm$	7.69 ${}^{{\dagger}{\dagger}{\dagger}}$	162.89 $\pm$	6.03 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	39
Arm span (cm)	183.93 $\pm$	13.37	192.86 $\pm$	8.09	$-$ 0.	81	171.40 $\pm$	13.50 ${}^{{\dagger}}$	165.67 $\pm$	12.94 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	43
Weight (kg)	81.67 $\pm$	9.36	70.14 $\pm$	10.93 ${}^{\ast}$	1.	13	58.50 $\pm$	7.58 ${}^{{\dagger}{\dagger}{\dagger}}$	59.67 $\pm$	6.00 ${}^{{\dagger}}$	$-$ 0.	17
BMI (kg $\cdot$ m ${}^{-2}$ )	25.50 $\pm$	2.64	21.90 $\pm$	3.49 ${}^{\ast}$	1.	16	21.27 $\pm$	1.69 ${}^{{\dagger}{\dagger}{\dagger}}$	22.48 $\pm$	1.87	$-$ 0.	68
Triceps skf. (mm)	12.71 $\pm$	5.49	12.33 $\pm$	4.63	0.	08	13.40 $\pm$	3.22	14.18 $\pm$	3.22	$-$ 0.	24
Subscapular skf. (mm)	14.09 $\pm$	6.35	9.63 $\pm$	2.90 ${}^{\ast}$	0.	90	11.34 $\pm$	1.13	11.77 $\pm$	3.13	$-$ 0.	18
Biceps skf. (mm)	4.50 $\pm$	2.51	4.30 $\pm$	1.29	0.	10	3.91 $\pm$	0.87	5.83 $\pm$	2.40 ${}^{\ast}$	$-$ 1.	06
Iliac Crest skf. (mm)	19.09 $\pm$	7.73	14.66 $\pm$	5.54	0.	66	14.58 $\pm$	3.82	16.30 $\pm$	4.65	$-$ 0.	40
Abdominal skf. (mm)	21.16 $\pm$	7.79	16.27 $\pm$	7.23	0.	65	13.57 $\pm$	3.52 ${}^{{\dagger}{\dagger}}$	15.62 $\pm$	3.33	$-$ 0.	60
Suprailiac skf. (mm)	13.35 $\pm$	7.04	9.90 $\pm$	4.86	0.	57	9.37 $\pm$	2.91	12.47 $\pm$	3.84	$-$ 0.	91
Thigh skf. (mm)	20.65 $\pm$	7.82	17.77 $\pm$	6.55	0.	40	22.53 $\pm$	4.54	25.80 $\pm$	5.58 ${}^{{\dagger}}$	$-$ 0.	64
Calf skf. (mm)	12.26 $\pm$	4.60	13.29 $\pm$	5.71	$-$ 0.	20	13.57 $\pm$	3.39	16.58 $\pm$	5.49	$-$ 0	.66
Arm perimeter (cm)	34.51 $\pm$	1.88	30.39 $\pm$	2.60 ${}^{\ast\ast\ast}$	1.	82	28.58 $\pm$	0.95 ${}^{{\dagger}{\dagger}{\dagger}}$	28.50 $\pm$	1.87	0.	05
P. of contracted arm (cm)	35.60 $\pm$	1.79	31.29 $\pm$	2.70 ${}^{\ast\ast\ast}$	1.	88	29.32 $\pm$	1.09 ${}^{{\dagger}{\dagger}{\dagger}}$	29.23 $\pm$	1.86	0.	06
Thigh perimeter (cm)	47.90 $\pm$	9.55	49.53 $\pm$	4.64	$-$ 0.	22	49.75 $\pm$	2.16	50.09 $\pm$	3.87	$-$ 0.	11
Calf perimeter (cm)	38.75 $\pm$	2.29	36.90 $\pm$	5.01	0.	47	34.90 $\pm$	2.17 ${}^{{\dagger}{\dagger}{\dagger}}$	34.64 $\pm$	2.37	0.	11
Waist P. (cm)	85.26 $\pm$	7.68	77.27 $\pm$	7.21 ${}^{\ast}$	1.	07	67.12 $\pm$	5.58 ${}^{{\dagger}{\dagger}{\dagger}}$	70.06 $\pm$	5.38 ${}^{{\dagger}}$	$-$ 0.	54
Hip P. (cm)	101.46 $\pm$	6.68	95.90 $\pm$	8.69	0.	72	90.39 $\pm$	6.33 ${}^{{\dagger}{\dagger}{\dagger}}$	93.49 $\pm$	3.81	$-$ 0.	59
Elbow diameter (cm)	5.86 $\pm$	0.47	5.80 $\pm$	0.52	0.	11	5.02 $\pm$	0.90 ${}^{{\dagger}{\dagger}}$	4.90 $\pm$	0.50 ${}^{{\dagger}{\dagger}}$	0.	17
Wrist diameter (cm)	4.73 $\pm$	0.54	4.44 $\pm$	0.34	0.	62	4.16 $\pm$	0.78 ${}^{{\dagger}}$	3.74 $\pm$	0.29 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	71
Knee diameter (cm)	9.29 $\pm$	0.62	9.04 $\pm$	0.55	0.	43	8.28 $\pm$	0.84 ${}^{{\dagger}{\dagger}{\dagger}}$	8.31 $\pm$	0.63 ${}^{{\dagger}}$	$-$ 0.	04
Ankle diameter (cm)	5.73 $\pm$	0.52	5.61 $\pm$	0.46	0.	24	5.14 $\pm$	0.79 ${}^{{\dagger}}$	4.81 $\pm$	0.20 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	57
Bone weight (kg)	10.32 $\pm$	1.51	9.70 $\pm$	0.83	0.	51	7.84 $\pm$	1.79 ${}^{{\dagger}{\dagger}{\dagger}}$	7.08 $\pm$	0.84 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	54
Fatty weight (kg)	12.59 $\pm$	4.19	9.33 $\pm$	3.15	0.	88	9.59 $\pm$	2.25 ${}^{{\dagger}}$	11.00 $\pm$	2.81	$-$ 0.	55
Muscle weight (kg)	39.75 $\pm$	3.97	34.21 $\pm$	4.98 ${}^{\ast\ast}$	1.	23	26.97 $\pm$	2.59 ${}^{{\dagger}{\dagger}{\dagger}}$	27.21 $\pm$	1.71 ${}^{{\dagger}{\dagger}}$	$-$ 0.	11
Fat (%)	14.98 $\pm$	3.63	13.00 $\pm$	2.71	0.	62	16.30 $\pm$	2.21	18.22 $\pm$	3.08 ${}^{{\dagger}{\dagger}}$	$-$ 0.	72
Bone (%)	12.61 $\pm$	2.13	14.03 $\pm$	1.87	$-$ 0.	71	13.31 $\pm$	1.89	11.86 $\pm$	0.51 ${}^{\ast{\dagger}}$	1.	05
Muscle (%)	48.31 $\pm$	2.64	48.87 $\pm$	1.58	$-$ 0.	26	46.29 $\pm$	2.05	45.83 $\pm$	3.33 ${}^{{\dagger}}$	0.	17

d: Cohen’s d; n: number; skf.: skinfold; P.: perimeter; ${}^{\ast}p<$ 0.05; ${}^{\ast\ast}p<$ 0.01; ${}^{\ast\ast\ast}p<$ 0.001 significant difference seniors vs. cadets; ${}^{{\dagger}}p<$ 0.05, ${}^{{\dagger}{\dagger}}p<$ 0.01, ${}^{{\dagger}{\dagger}{\dagger}}p<$ 0.001 significant difference men vs. women.

In addition, men and women significantly differed in anthropometric parameters (Table 1). Senior athletes significantly differed between sexes in height, weight, BMI ( $p<$ 0.001), arm span ( $p<$ 0.05), and abdominal skinfold ( $p<$ 0.01); in perimeters of relaxed arm, contracted arm, calf, waist, and hip ( $p<$ 0.001); in diameters of elbow ( $p<$ 0.01), knee ( $p<$ 0.001), wrist, and ankle ( $p<$ 0.05); and in weight of bone, muscle ( $p<$ 0.001), and fat ( $p<$ 0.05). Cadets significantly differed between sexes in height, arm span ( $p<$ 0.001), weight ( $p<$ 0.05), thigh skinfold ( $p<$ 0.05), and waist perimeter ( $p<$ 0.05); in diameters of elbow ( $p<$ 0.01), wrist, ankle ( $p<$ 0.001), and knee ( $p<$ 0.05); in weight of bone ( $p<$ 0.001) and muscle ( $p<$ 0.01); and in percentages of fat ( $p<$ 0.01), bone, and muscle ( $p<$ 0.05).

Table 2

Isokinetic and hand grip strength according to the category in male and female players

	Men										Women
	Seniors ( $n=$ 17)				Cadets ( $n=$ 7)						Seniors ( $n=$ 10)				Cadets ( $n=$ 10)
	Mean $\pm$ SD		$d^{\rm a}$		Mean $\pm$ SD		$d^{\rm b}$		$d^{\rm a}$		Mean $\pm$ SD		$d^{\rm a}$		Mean $\pm$ SD		$d^{\rm b}$		$d^{\rm a}$
PM (N $\cdot$ m)
IR 60	50.41 $\pm$	9.83			41.57 $\pm$	5.59 ${}^{\ast}$	1.	11			30.50 $\pm$	6.62 ${}^{{\dagger}{\dagger}{\dagger}}$			28.00 $\pm$	4.45 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	44
ER 60	38.59 $\pm$	6.42 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			28.86 $\pm$	3.80 ${}^{\ast\ast{\ddagger}}$	1.	84			23.30 $\pm$	5.06 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$			20.80 $\pm$	5.22 ${}^{{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	49
Ratio 60 (%)	78.59 $\pm$	15.71	1.	18	69.86 $\pm$	10.04	0.	66	2.	40	78.40 $\pm$	16.06	1.	11	73.80 $\pm$	11.95	0.	32	2.	25
IR 240	42.88 $\pm$	7.43			30.57 $\pm$	4.86 ${}^{\ast\ast\ast}$	1.	96			24.10 $\pm$	5.26 ${}^{{\dagger}{\dagger}{\dagger}}$			21.80 $\pm$	4.10 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	49
ER 240	28.47 $\pm$	5.62 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			21.43 $\pm$	2.44 ${}^{\ast\ast{\ddagger}}$	1.	62			17.30 $\pm$	2.21 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$			15.70 $\pm$	3.23 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	58
Ratio 240 (%)	67.71 $\pm$	12.59	1.	87	70.57 $\pm$	8.12	$-$ 0.	27	2.	26	72.20 $\pm$	10.58	1.	57	73.00 $\pm$	9.13	$-$ 0.	08	2.	15
PM Relative to body weight (N $\cdot$ m $\cdot$ kg ${}^{-1}$ )
IR ${}_{\text{BW}}$ 60	0.60 $\pm$	0.09			0.60 $\pm$	0.12	$-$ 0.	01			0.53 $\pm$	0.12			0.45 $\pm$	0.10 ${}^{{\dagger}}$	0.	71
ER ${}_{\text{BW}}$ 60	0.47 $\pm$	0.09 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			0.42 $\pm$	0.06 ${}^{{\ddagger}}$	0.	65			0.40 $\pm$	0.08 ${}^{{\dagger}{\ddagger}{\ddagger}}$			0.33 $\pm$	0.08 ${}^{{\dagger}{\ddagger}{\ddagger}}$	0.	92
IR ${}_{\text{BW}}$ 240	0.52 $\pm$	0.10			0.44 $\pm$	0.08	0.	85			0.41 $\pm$	0.09 ${}^{{\dagger}}$			0.35 $\pm$	0.10	0.	66
ER ${}_{\text{BW}}$ 240	0.34 $\pm$	0.08 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			0.31 $\pm$	0.04 ${}^{{\ddagger}}$	0.	54			0.30 $\pm$	0.04 ${}^{{\ddagger}{\ddagger}}$			0.25 $\pm$	0.06 ${}^{\ast{\dagger}{\ddagger}{\ddagger}}$	0.	95
AP (W)
IR 60	39.12 $\pm$	8.10			32.71 $\pm$	5.59	0.	92			24.70 $\pm$	5.70 ${}^{{\dagger}{\dagger}{\dagger}}$			21.90 $\pm$	4.41 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	55
ER 60	27.53 $\pm$	3.84 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			22.00 $\pm$	4.47 ${}^{\ast\ast{\ddagger}}$	1.	33			16.00 $\pm$	2.94 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$			14.70 $\pm$	3.56 ${}^{{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	40
Ratio 60 (%)	72.47 $\pm$	15.28	1.	38	68.14 $\pm$	12.67	0.	31	2.	09	66.10 $\pm$	9.83	2.	10	67.10 $\pm$	7.14	$-$ 0.	12	3.	43
IR 240	101.94 $\pm$	19.60			72.43 $\pm$	8.44 ${}^{\ast\ast\ast}$	1.	96			53.40 $\pm$	17.12 ${}^{{\dagger}{\dagger}{\dagger}}$			45.30 $\pm$	14.47 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	51
ER 240	60.53 $\pm$	16.27 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			47.29 $\pm$	8.67 ${}^{{\ddagger}}$	1.	02			30.70 $\pm$	7.60 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$			28.60 $\pm$	9.34 ${}^{{\dagger}{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	25
Ratio 240 (%)	60.47 $\pm$	14.24	2.	00	66.00 $\pm$	13.22	$-$ 0.	40	2.	34	60.50 $\pm$	13.87	1.	58	64.90 $\pm$	10.83	$-$ 0.	35	1.	39
AP Relative to body weight (W $\cdot$ kg ${}^{-1}$ )
IR ${}_{\text{BW}}$ 60	0.47 $\pm$	0.08			0.47 $\pm$	0.09	$-$ 0.	04			0.43 $\pm$	0.10			0.35 $\pm$	0.09 ${}^{{\dagger}}$	0.	80
ER ${}_{\text{BW}}$ 60	0.33 $\pm$	0.06 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			0.31 $\pm$	0.04 ${}^{{\ddagger}}$	0.	37			0.27 $\pm$	0.04 ${}^{{\dagger}{\ddagger}{\ddagger}}$			0.23 $\pm$	0.05 ${}^{{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	89
IR ${}_{\text{BW}}$ 240	1.23 $\pm$	0.23			1.05 $\pm$	0.14	0.	95			0.92 $\pm$	0.30 ${}^{{\dagger}{\dagger}}$			0.73 $\pm$	0.28 ${}^{{\dagger}}$	0.	65
ER ${}_{\text{BW}}$ 240	0.74 $\pm$	0.23 ${}^{{\ddagger}{\ddagger}{\ddagger}}$			0.68 $\pm$	0.11 ${}^{{\ddagger}}$	0.	31			0.53 $\pm$	0.13 ${}^{{\dagger}{\ddagger}{\ddagger}}$			0.45 $\pm$	0.14 ${}^{{\dagger}{\dagger}{\ddagger}{\ddagger}}$	0.	58
HAND GRIP TEST (kg)
Dominant hand	44.94 $\pm$	7.49			39.14 $\pm$	8.47	0.	73			27.40 $\pm$	3.27 ${}^{{\dagger}{\dagger}{\dagger}}$			26.60 $\pm$	4.33 ${}^{{\dagger}{\dagger}{\dagger}}$	0.	21
Non dominant	38.00 $\pm$	6.40			34.57 $\pm$	7.81	0.	48			24.80 $\pm$	2.70 ${}^{{\dagger}{\dagger}{\dagger}}$			24.00 $\pm$	1.89 ${}^{{\dagger}}$	0.	34

$d^{\rm a}$ : Cohen’s d within subjects (IR vs. ER); $d^{\rm b}$ : Cohen’s d inter subjects (cadets vs. senior); n: number; 60: 60 ${}^{\circ}$ /s; 240: 240 ${}^{\circ}$ /s; PM: Peak moment; AP: Average Power; IR: Internal Rotation; ER: External Rotation; BW: body weight; ${}^{\ast}p<$ 0.05; ${}^{\ast\ast}<$ 0.01; ${}^{\ast\ast\ast}p<$ 0.001 significant difference seniors vs. cadets; ${}^{{\dagger}}p<$ 0.05, ${}^{{\dagger}{\dagger}}p<$ 0.01, ${}^{{\dagger}{\dagger}{\dagger}}p<$ 0.001 significant difference men vs. women; ${}^{{\ddagger}}p<$ 0.05, ${}^{{\ddagger}{\ddagger}}p<$ 0.01, ${}^{{\ddagger}{\ddagger}{\ddagger}}p<$ 0.001 significant difference IR vs. ER.

3.2 Isokinetic characteristics

Cadet and senior players of the same sex had significantly different isokinetic parameters (Table 2). Male senior players had significantly higher strength in internal rotation and external rotation at both velocities ( $p<$ 0.001 to $p<$ 0.05). Significant differences were also observed for average power in external rotation at 60 ${}^{\circ}$ /s ( $p<$ 0.01) and internal rotation at 240 ${}^{\circ}$ /s ( $p<$ 0.001). No significant differences were found in the normalized PM or AP in males. For female players, the only significant difference between seniors and cadets was the normalized PM in ER at 240 ${}^{\circ}$ /s ( $p<$ 0.05).

We also observed significant differences in isokinetic parameters between internal rotation and external rotation. Players of both age groups had significantly higher internal rotation compared to external rotation strength for both men and women ( $p<$ 0.001 to $p<$ 0.05; large effect sizes) (Table 2).

Likewise, we observed significant differences in isokinetic parameters between men and women (Table 2). In general, male and female senior players significantly differed in peak torque and average power, for IR and ER at both angular velocities ( $p<$ 0.001). Relative to body weight, male and female senior players significantly differed in PM values for ER at the low and IR at the higher velocity ( $p<$ 0.05), average power in ER at both velocities ( $p<$ 0.05) and IR at the higher ( $p<$ 0.01). Male and female cadet players significantly differed in all absolute values of measurements and those relative to body weight ( $p<$ 0.001 – $p<$ 0.01), except for IR at 240 ${}^{\circ}$ /s.

3.3 Hand grip test

Hand grip findings did not significantly differ within the same sex (Table 2). However, there were significant differences between sexes in both categories with dominant and non-dominant hands ( $p<$ 0.001 – $p<$ 0.05).

4. Discussion

The objective of this study was to determine if cadet water polo players are ready to train and play with senior teams, as it is a common practice in some clubs. Considering the relevance of body size and strength in this sport, we hypothesized that still-growing young players would not be ready to play at a senior level or that their performance would be lower than that of older peers. Our findings corroborate this hypothesis in men, in which young players had lower absolute strength, highlighting body mass as a critical element in performance. However, women cadet players appear to be physically prepared to compete with senior teams. To the best of our knowledge, this is the first work to investigate this topic in water polo players.

Several studies of anthropometry and performance have been conducted for water polo. In this sport, body size is important not only because of the large amount of physical contact, but also because larger bodies enable players to obtain better positions in the pool and tall players with long arms can better reach and control passes [18]. For these reasons, taller players are found in national compared to regional levels for both male [19] and female squads [2]. Moreover, Lozovina and Pavicic [20] analyzed anthropometric changes and observed that height increased significantly in elite water polo players from 1980–1995. In our study, we observed anthropometric differences between older and younger men that were centered on parameters related to body size. However, these differences were not observed among women.

In the present work, senior players had larger body mass, probably due to larger muscle weight and arm circumference. Differences in arm diameter seem to be specifically related to muscle bulk because the amount of fat (biceps skinfold) in the arm was similar in both groups. This is an important finding because strength and performance are proportional to muscle size [21]. In a similar vein, Ferragut et al. [8] observed positive correlations between muscle weight and relaxed arm perimeter with throwing speed as well as body weight and perimeter of contracted arm with hand grip strength. In ultra-endurance runners [22] and in judokas [23], arm circumference is a relevant factor associated with performance. Other authors [5, 6] have demonstrated that elite compared to amateur water polo players have greater dimensions in body mass, height, and upper extremities, which lead to faster throwing speed and confirms the importance of anthropometric factors as elements of success.

In this regard, we observed that male cadet players displayed lower absolute strength in all strength measurements (IR and ER) and in average power for ER at 60 ${}^{\circ}$ /s and IR at 240 ${}^{\circ}$ /s compared to senior players. In contrast, no differences were observed when strength was related to body mass. These findings are particularly relevant for coaches. Coaches must be aware that young players may not have the same performance level on the field because among other things they may perform technical actions with less force. In addition, the differences imply that if both age groups of male players train together, coaches must implement adapted and individualized strength training programs for each age group, accounting for these differences and considering the progression of physiological adaptations of young players. In contrast, both cadet and senior female players displayed similar anthropometric and strength values, so adolescent female players are presumably prepared to train and compete with senior female players.

In regards to the power of external and internal rotator muscles of the shoulder, we measured a predominance of IR compared to ER strength, which is in line with previous studies [11, 24] and has been related to better throwing speed [25]. However, previous studies also have described a significant association between ER weakness and increased probability of substantial shoulder problems throughout the season [26]. Risk of shoulder injury is increased due to insufficient ER strength to balance and decelerate the shoulder in the follow-through phase of throwing [11, 18, 27]. On this basis, Miller et al. [28] recommended that a ratio of 0.67 and above is desirable in water polo players. In our study, these ratios were similar in old and young players and met this minimum in all measurements, except for AP at 240 ${}^{\circ}$ /s both in men and women. Hence, coaches should pay special attention to strengthening exercises for ER because they may be important for injury prevention [26].

Likewise, it should be taken into account that the reliability of isokinetic dynamometry is generally higher at slower speeds [29] and therefore, findings of the tests at 240 ${}^{\circ}$ /s should be interpreted cautiously. Olivier and Daussin [24] and Osternig [30] concluded that beyond 240 ${}^{\circ}$ /s with sedentary subjects, the part of the curve that is truly isokinetic is not large enough for the test performed to be significant.

Compared to women, men had greater strength in each test related to their larger bodies, because strength is proportional to body size [21]. Previous studies have shown that the strength of the upper limb of women is 55% of that of men [31]. Likewise, relative strength was also higher in men compared to women in most parameters, similar to other studies [32, 33]. However, Fleck and Kraemer [34] emphasize that strength differences are reduced when represented as relative strength and that women can have higher lower limb strength than men.

5. Conclusions

The present study shows that the female cadet players are physically prepared to compete and train with senior teams in terms of anthropometric measurements and isokinetic strength of the shoulder rotators. However, this finding was not confirmed in male cadet players. Anthropometric differences between older and younger men were centered on parameters related to body mass, such as weight, BMI, muscle weight, and arm circumference. Older players had greater absolute strength of rotator muscles of the shoulder than young players. This result is particularly relevant for coaches because it suggests they should program adaptive and individualized strength training according to a player’s age, accounting for the progression of physiological adaptations. Nonetheless, additional research is required to determine the most efficient working methodology for each training group. Likewise, this study showed that strength exerted in internal rotation was greater than that exerted in external rotation. Although this is desirable for good performance (throwing speed), it also could be related to increased risk of shoulder injury. These results can help coaches and sports scientists formulate guidelines and recommendations for preparation, control, and performance of water polo players.

Footnotes

Acknowledgments

We express sincere gratitude to the parents and children who agreed to participate in this research and acknowledge the collaboration of the water polo club Leioa Waterpolo. This research was partially supported by a grant the Basque Government (code: IT922-16) and the University of the Basque Country, UPV/EHU (code: PPG17/34). Izaro Esain was supported by a PhD Studentship from the Basque Government (Pre_2015-2-0207).

Conflict of interest

There are no conflicts of interest.

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Anthropometry and isokinetic strength in water polo: Are young players ready to compete on adult teams?

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Methods

2.1 Participants

2.2 Procedures

2.2.1 Anthropometry

2.2.2 Isokinetic testing

2.2.3 Hand grip test

2.3 Statistical analyses

3. Results

3.1 Anthropometric characteristics

Table 1 Anthropometric characteristics (mean ± SD) according to the category in male and female players

3.3 Hand grip test

4. Discussion

5. Conclusions

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Anthropometric characteristics (mean $\pm$ SD) according to the category in male and female players