Throwing is a composite kinetic action involving the majority of joints of the whole human body (Skoufas, Kotzamanidis, Hatzikotoulas, Bebetsos & Patikas, 2003), in a harmonious segmental sequencing pattern of various body parts (Atwater, 1979). According to a study by Bayios and Boudolos (2005), the successful throwing of an object starts with the proper support on the ground and is completed with the arm undertaking the final throwing effort. Throwing performance is differentiated according to the biological development of the thrower (Dun, Fleisig, Loftice, Kingsley, & Andrews, 2007). This comes in line with many researchers supporting that the main throw characteristics, i.e. neuromuscular coordination and strength- are differentiated during prepuberty (Sakurai & Miyashita, 1983; Fleisig, Barrentine, Zheng, Escamilla, & Andrews, 1999; Hong, Cheung & Roberts, 2001).
In addition, it is pointed out that girls are inferior to boys with regard to these biomechanical characteristics, starting from the age of 7 years old and becoming more intense as approaching adulthood (Pauwels, 1979, Sakurai & Miyashita, 1983; Danilov, 1985). Their typical difference is that male athletes use the whip lash throw while female athletes use the push throw. This difference continues to exist after puberty and even during adulthood probably because of learning issues and, more specifically, due to the fact that females, from their early childhood, do not deal with kinetic activities as much as males do (Burton, Greer & Weise-Bjornstal, 1992).
Performance level and chronological age are two major factors that determine the correlation between throwing action and strength. It has been observed that throwing has a high positive correlation with strength at development ages but not in the following years (Sakurai & Miyashita, 1983) and that the biggest benefits of strength training on throwing performance are seen in athletes of younger age (Behringer, Vom Heede, Matthews, Mester, 2011).
In the past it was believed that strength training brought no improvement in muscle strength during childhood and puberty, mainly due to the reduced levels of androgen hormones (American Academy of Pediatrics, 1983). On the contrary, more recent studies have shown that there is the potential of improving strength in children and adolescents when implementing well planned strength programs (Ozmum, Mikesky & Surburg, 1994; Falk & Mor, 1996; Faigenbaum, La Rosa- Loud, Westcott & Long, 1999; Faigenbaum, Loud, O’ Connell, Glover & Westcott, 2001; Granacher, A. Goessele, Rogo, Wischer, Fischer, Zuerny, Gollhofer & Kriemler, 2011). Moreover, it has been demonstrated that strength programs with the use of isokinetic dynamometres, resistance weight equipment, free weights and resistances or even with the use body mass, can improve muscle strength, thus resulting in improvement of the throwing ball velocity (Weltman, Janney, Rians, Strand, Cahill & Katch, 1986; Sailors & Berg, 1987). Strength training has been proven effective in enhancing specific performance skills, such as jumping and throwing (Behringer et al., 2011), that are basic elements in VB.
Muller (1982) points out that the effective energy transfer affects significantly the throwing ball velocity (TBV). It has been indicated that TBV can improve with the use of various methods in adults (Van den Tillaar, 2004; Derenne, Ho & Murphy, 2001) and in adolescents (Escamilla, Fleisig, Yamashiro, Mikla, Dunning, Paulos & Andrews, 2010). However, there is lack of respective trials with children and, to the authors' knowledge, there is no research having investigated the effect of VB training on TBV in male children. There is only one relevant study, concerning though girls of development ages, indicating that female VB athletes at the age of 11 and 12 years present higher TBV values compared to untrained girls of the same age (Panagiotidou et al., 2008), yet without presenting any differences in handgrip strength.
The purpose of the study was to evaluate the effect of volleyball training on throwing performance and handgrip strength in male children. The aim of the study was to identify the value of the training process and its effect in improving performances and, even furthermore, to point out the benefits of dealing with volleyball more specifically and with sports in general.
Methodology
Sample
The study was carried out during the competition period 2009-1010. The total sample consisted of 150 boys of the Prefecture Department of Thessaloniki, Greece, aged 8-12 years old: seventy-five (75) volleyball athletes (VA) and seventy-five (75) untrained boys that composed the control group (CG). The sample was divided in five (5) age groups, each one consisting of 30 boys: fifteen (15) VA and fifteen (15) CG. The sample was selected randomly. VA who were training less than three times a week were excluded from the study.
Measurements for VA were conducted in the indoor gyms where they did their training, while measurements for the CG took place in the school playground during the Physical Education lesson. All children participated on a voluntary basis in the study following the written consent of their parents and with their school coaches’ and directors’ approval.
Measurement instruments
The study was conducted with the use of the following tools:
Electronic scales Seca 707, accuracy of 100gr, for measuring body mass.
Height rod Seca 220, accuracy of 0.1cm, for measuring body height.
Decimal tape measure, accuracy of 0.5cm, for measuring hand length and width.
Sports Radar Gun (Sports Electronics Inc., SR 3400 (Doppler phenomenon), for measuring throwing ball velocity.
Handgrip (Jamar), for measuring handgrip strength.
Balls, number 1, for measuring the throw.
Description of testings
First of all, the personal information of all boys were recorded. Then the following anthropometric characteristics were measured: standing body height (cm), body mass (kg), hand length and width (cm). The boys’ BMI was also estimated. The motor parameters measured were the overarm throwing ball velocity in standing and sitting position and the handgrip strength.
Measurement process
Before each measurement, the tested children were informed about the aim of the evaluation and were encouraged to achieve the best possible result. Following warm-up, the boys made testing efforts in order to get familiar with the throwing technique and then performed five (5) efforts from standing position (TBVSt) and respectively from sitting position (TBVS). The throw with the highest value was the one recorded. In TBVSt, every tested child had to be in stepping position with opposite arm-leg and throw the ball overarm using the dominant hand. In TBVS, the body trunk and the opposite arm that did not perform the throw were immobilised with a waist belt, so as to avoid the participation of other muscle groups. For measuring handgrip strength (HS), the boys performed three grippings in the hand dynamometer using their dominant hand; the highest value achieved was recorded. The elbow was placed in a 90° position to avoid the participation of another muscle group. In-between every effort there was a pause of 30´´ in duration.
Statististical analysis
Analysis of Variance 2X5 was used to identify differences between the two boys’ groups (VA and CG) and among the 5 age groups (8-12 y.o.). The statistically significant differences were traced with the Pοst hoc Scheffe test. Measurement values were expressed with mean values standard deviations. The significance level was defined as p<.05.
Results
Anthropometric and kinetic characteristics of VA and CG
The results indicate that overall VA were superior to the CG, demonstrating higher values in all anthropometric parameters and significant differences in body height (p<.05) and hand length and width (p<.01). With regard to the boys’ kinetic characteristics, a statistically significant effect of age was found (p<.05), but no statistically significant difference between groups was observed (p<.05). (Table 1)
More analytically, the overall trained boys were significantly superior in body height by 5.0cm, compared to the CG (p<.05). Although, the body mass in total value was higher in VA than in the untrained boys (3.5kg), the difference was not statistically significant (p>.05). Similarly, no statistically significant differences were found between VA and CG with regard to BMI (p>.05). As for hand length and width, VA were significantly superior compared to the CG by 2.0cm and 1.3cm respectively (p<.01).
Table 1: Anthropometric and kinetic characteristics of VA (n=75) and CG (n= 75), (*p<.05, **p<.01).
|
MEASUREMENTS |
VB ATHLETES |
CONTROL GROUP |
|
|
Anthropometric |
Body mass (kg) |
42.3±11.9 |
38.7±11.6 |
|
Height (cm) |
145.9±11.8* |
140.9±10.6* |
|
|
BMI (kg/m2) |
19.5±3.1 |
19.2±3.5 |
|
|
Hand length (cm) |
17.2±1.5** |
15.1±1.2** |
|
|
Hand width (cm) |
19.2±1.6** |
17.9±1.6** |
|
|
Kinetic |
TBVSt (m/sec) |
32.7±10.3 |
35.4±8.2 |
|
TBVS (m/sec) |
24.8±7.8 |
27.5±6.8 |
|
|
HS (joule) |
21.4±6.1 |
21.7±6.1 |
|
Anthropometric characteristics of VA and CG per age
VA were superior compared to non-athletes in the majority of anthropometric characteristics per age group (p<.05). The statistically significant differences between trained and untrained boys per age are analytically presented in Table 2.
Table 2: Anthropometric characteristics between VA and CG per age and group (VA n = 75 & CG n = 75), (*p<.05, **p<.01).
|
AGE (yrs) |
8 |
9 |
10 |
11 |
12 |
|
|
HEIGHT (cm) |
VA |
129.4±7.4 |
143.7±4.8* |
144.9±5.4* |
152.8±7.2 |
158.3±8.0 |
|
CG |
128.8±4.9 |
137.4±7.2* |
140.3±6.4* |
143.1±5.0 |
155.0±8.5 |
|
|
BODY WEIGHT (kg) |
VA |
29.5±6.2 |
39.7±6.2* |
40.1±7.7 |
47.0±7.1 |
55.3±12.8 |
|
CG |
27.5±3.5 |
34.7±3.6* |
38.3±6.2 |
42.3±11.4 |
51.0±14.0 |
|
|
BMI (kg/m2) |
VA |
17.4±1.8 |
19.0±2.1 |
19.0±3.0 |
20.1±2.3** |
22.0±4.3 |
|
CG |
16.6±2.3 |
18.5±2.3 |
19.4±2.2 |
20.4±4.3** |
21.0±4.2 |
|
|
HAND WIDTH (cm) |
VA |
17.5±0.3 |
19.5±1.2** |
18.8±1.1** |
19.6±1.5* |
20.7±1.7 |
|
CG |
17.0±1.0 |
17.4±1.3** |
17.4±1.5** |
18.2±1.0* |
19.7±1.5 |
|
|
HAND LENGTH (cm) |
VA |
15.3±0.6** |
17.1±0.7** |
17.3±0.9** |
17.5±1.3** |
18.6±1.4** |
|
CG |
14.3±0.6** |
14.7±1.1** |
15.1±0.8** |
15.2±1.0** |
16.3±1.3** |
|
Kinetic characteristics of VA and CG per age
In the standing position throw, VA showed no statistically significant difference from the CG (p>.05). The TBVSt of both groups presented progressive higher values in direct ratio to the corresponding increase of age (p>.05). (Figure 1)
Figure 1: Graphic representation of TBVSt between VA and CG per age.
In throwing from the sitting position, VA showed no statistically significant difference compared to the CG (p>.05). The TBVS of both groups presented gradually higher values in direct ratio to the corresponding increase of age (p>.05). (Figure 2)
Figure 2: Graphic representation of TBVSt between VA and CG per age.
With regard to handgrip strength, VA showed no statistically significant difference from the control group (p>.05). The HS of both groups presented higher values in direct ratio to the corresponding increase of age (p>.05). (Figure 3).
Figure 3: Graphic representation of HS between VA and CG per age.
Discussion - Conclusions
According to the results, VA presented statistically higher values in most anthropometric parameters in comparison to the CG. This result comes in line with the study by Papadopoulou, Papadopoulou, Panagiotidou, Liapi & Kotzamanidis (2006), where similar findings derived in all development ages of female VA. Also, in the present study VA were not found to be significantly superior to the control group in any of the three kinetic parameters (TBVSt, TBVS, HS). There was also progressive increase of TBVSt, TBVS and HS, in relation to the age development. The TBVSt values were always higher than the TVBS values in both groups.
More analytically, VA were superior compared to the CG in body height, demonstrating significant differences only at the age of 9 and 10 years old. The high posture constitutes a critical factor for the VB athlete so that s/he manages to meet the ball at the maximum height above the net (MacLaren, 1993). In addition, according to a study by Papadopoulou (2003), body height is a major performance element at the top VB level and body height values are positively correlated with the competition level. The high posture in VA can probably be attributed to the selection of children with high mean body height so that they meet the needs of the sport (Papadopoulou et al., 2006).
As for the body mass, higher values were observed in VA compared to the boys of the CG, which values were though significant only at the age group of 9 years old. In VA body mass values have a strong positive correlation with respective body height values (Papadopoulou, 2001), and probably the superiority of body mass and height values in the 9-year old VA of the present study compared to the CG of same age, is attributed to the fact. With regard to BMI, significantly higher but normal CG values were found in comparison with VA at the age of 11y.o.
In all age groups, VA presented significally higher values in hand length and width compared to the CG, with the exception of the ages of 8 and 12 years old where the superiority was not significant. The higher values observed in the athletes’ handgrip can be attributed to the superiority of their body height (Xu, Zhang, Cong, Wu & Wang, 2007).
In overall, VA showed a gradual increase of values in almost all anthropometric parameters among the age groups, with the exception of handgrip at the age of 10 years old. Likewise, the CG showed a similar progressive increase in all anthropometric variables per age. Some anthropometric characteristics, such as body weight, lean body mass, arm span, hand length and width are correlated with throwing velocity (Skoufas et al, 2003).
Although, in the beginning it had been expected that VA would present significant differences with higher values in TBVSt, TBVS and HS, it was found out that they did not differ significantly in any of the examined variables compared to the CG. The findings of this study come in contradiction with the findings deriving from the study by Clements, Ginn and Henley (2001), which was conducted though in adolescent VA showing that athletes were superior to their untrained peers in the above parameters. This was attributed to the fact that in puberty muscle adaptations are related to the increased muscular mass (Fournier, Ricci, Taylor, Ferguson, Monpetit & Choitman, 1982). However, no clear assumption on the issue can be drawn due to lack of similar references to boys of younger ages, about how systematic occupation with a sport during childhood can differentiate the throwing ball velocity (TBV).
Moreover, TBVSt, TBVS and HS values in VB athletes appeared progressively increasing in direct relation to the increase of age. The same was found in the CG: as age advanced, the throwing ability and HS increased, too. This result comes in line with the study by Ritzaleou (2005), which measured TBV in untrained girls 7-18 years old and observed that throwing velocity improved in accordance with the age development. All TBVSt values were higher than the corresponding TBVS values at all age groups of trained and untrained boys. This also agrees with corresponding studies by Bayios and Boudolos, 2005, who investigated the throwing performance towards known and unknown visual target in handball by analyzing the overall kinetic chain in correlation with the joints participating in the throw motion. The TBV superiority can be attributed to the evolution of the neuromuscular coordination as age advances, resulting in more joints participating in the movement, so that the velocity of the next joint yields higher angular velocities than generated by the previous joint (Sakurai & Mayashita, 1983).
It was also found in this study that TBVSt and TBVS values were directly related to HS values: the higher the TBVSt and TBVS values, the higher the HS values. This comes in line with Hermasi (2004), who observed a positive correlation between strength and throwing ability. Throwing is a movement of strength and it is considered that changes in muscle strength are required for its improvement (Skoufas, Kotzamanidis, Hatzikotoulas & Patikas, 2003). The integration of strengthening exercises with external resistances might probably be able to differentiate the VA performance, as derives from the study by Fleck and Kraemer (1993) who believe that strengthening the upper body muscle groups in young athletes with appropriate strengthening programs is highly important. However, in order for a strengthening program to be safe and effective at these ages, there are some basic training principles that have to be followed. First of all, learning properly the technique of exercises and then improving strength through the exercises. Moreover, at development ages there has to be a progressive increase of loading. In the beginning, proper execution of simple exercises only with the body weight and then exercises with external resistances (Kellis, 1999).
As a conclusion, volleyball athletes were superior in most somatometric parameters at all ages with obvious corresponding increase of values as age progresses. Lastly, it is concluded that systematic volleyball training two-three times a week during childhood, may probably not be enough to differentiate the throwing ability and handgrip strength between young volleyball athletes and untrained boys.
Suggestions
ACKNOWLEDGEMENTS
We would like to thank the Hellenic Volleyball Association of Thessaloniki (Ε.PE.S.TH.), as well as all coaches and parents for their cooperation and all boys for participating in the study. We would also like to warmly thank Mrs Ritzaleou M., MSc, Professor of Physical Education, for her valuable support and cooperation.
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