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Maximal Strength, Speed and Isokinetic Evaluation of Power in Youth Basketball Players

Juan Henrique Szymczak Conde1; Poliana de Lima Costa1; Gislaine Cristina de Souza1; Yuri Rafael Dias1; Fabíola Vila Santos1;Raul Osiecki1

1Center for the Studies of Physical Performance, Federal Universityof Paraná, Paraná, Brazil

ABSTRACT

Conde JHS, Costa PL, Souza GC,Dias YR, Santos FV, Osiecki R. Maximal Strength, Speed and Isokinetic Evaluation of Power in Youth Basketball Players. JEPonline2015;18(6):45-51. The purpose of this study was to evaluate power in youth basketball players (using an isokinetic dynamometer) and verify its relation to maximal strength and speed.Fourteen male basketball athletes (age: 15.71 ± 0.99 yrs, body mass: 74.25 ± 10.04 kg, height: 184.28 ± 6.2 cm, body fat: 10.39 ± 3.3%) performed three assessments on different days: (1)anthropometric; (2)isokinetic evaluation for peak power of knee flexors andextensors at 240°/s; and (3) one repetition maximum (1-RM) inthe 45° leg pressand 30m sprint test and vertical jump. Values for vertical jump, 30m sprint, 1-RM, power of knee flexors andextensors were, respectively: 52.5 ± 7.81 cm; 4.63 ± 0.19 sec; 340.64 ± 94.8 Kg; 193.64 ± 37.35 W and 252.81 ± 86.8 W. 1-RM was significantly related to power of knee flexors (r=0.59) and knee extensors (r=0.67). On the other hand, a significant correlation was found between the 30m sprint and vertical jump (r= -0.59). Besides, physical-motor tests were significantly related to anthropometric variables. Significant associationswere found between the vertical jump and 30m sprint time, power of knee flexors and extensors as well as maximum strength in youth basketball athletes.

Key Words:Anaerobic power, Sprint, Vertical jump, One repetition maximum

INTRODUCTION

Efforts with anaerobic characteristics (e.g., rebounding, shooting, blocking, fast breaks and defensive balance) are responsible to the success in basketball. Such activities depend on power and combining strength and speed. Thus, the evaluation of variables related to power is relevant for prescribing and controlling the training of basketball players.

Delextrat and Cohen (2)submitted elite and amateur basketball players to vertical jump, maximal strength in bench press, agility “T” test, and isokinetic evaluation of knee extensors torque. The results showed that elite players are stronger, more agile, jump higher, and demonstrate greater power levels.

However, the evaluation of thepower through devices such as isokinetic dynamometers and force plates are less widely used due to the high cost. Studies have demonstrated the validity and feasibility of field tests since they are cheaper, simpler, and more specific(1,6). As an example, the 30m sprint test is an important measure of anaerobic power for sports that depend on the ability to perform brief and intense repeated action. Dardouri et al. (6)reporteda significant correlation between the 30m sprint testand total time (r=0.63; P=0.001) and peak time (r=0.62; P =0.001) duringrepeated sprint test in team sports athletes, including basketball players.The power can also be evaluated by jump.Alemdaroğlu (1) demonstrated a moderate, but significant correlation (r = 0.49; P<0.05) between countermovement jump and peak power during the Wingate test in basketball players. Additionally, there was a significant inverse correlation between the countermovement jump and 30m sprint (r= -0.62; P<0.05) and betweenthe agility “T” test and 30m sprint (r= 0.50; P<0.05).

Hence, it is reasonable that the scientific evidence that supports the use of simple methodology could assist in the evaluation of the performance of youth basketball athletes, since, in competitions and trainings, the demand for youth players is as high as the adult category. At the same time, there is no structure for the evaluation and training plan for them. Starting from this premise, the purpose of this study was to evaluate power in youth basketball players and verify its relation to maximal strength and speed.

METHODS

Subjects

The subjects for this study consisted of 14 male basketball athletes (age: 15.71 ± 0.99 yrs, body mass: 74.25 ± 10.04 kg, height: 184.28 ± 6.2 cm, body fat: 10.39 ± 3.3%) who were competing at the regional level. All subjects had at least 2 yrs experience in the sport. Once informed about the risks and benefits of the study, a signed consent form wasapproved by the subjects’ parents.The Ethics Committee of the Federal University of Parana approved the research procedures.

Procedures

The study consisted of three sessions of assessments interspersed for 24 hrs. The first was carried out in the laboratory where all subjects had their body mass, height, and skin folds measured. The second session took place in a clinic in which the subjects performed the isokinetic evaluation for power of knee flexors and extensors. In the third session, the subjects performed the 30m sprint test, vertical jump, and maximal strength (1-RM).

Anthropometric Measures

The subjects’ height was measured using a stadiometer with 1 mm accuracy (Alturexata, Brazil). Total height wasmeasured from the dactiloidal point of the right hand above the head to the plantar region. Body mass was measured using a digital balance (Filizolla) with 100g accuracy. Body density was obtained through skinfold measurements (subscapular, abdomen, triceps, andmidaxillary) accordingly to theprotocol proposed by Forsyth and Sinning (9) using a caliper with an accuracy of 0.1 mm and breadth of 80 mm (Cescorf, Brazil). Percentage of body fat was calculated and corrected by the equation proposed bySiri (15).

Vertical Jump

The subjects performed three jumps interspersed with a 2-minrecovery. The arms were used to support the movement from the vertical position and touch the tape-measure on the wall with the hands at the greatest height possible. The height of the jump was obtained by subtracting the total height from the higher value reached.

Maximal Strength (1RM)

Each subject performed one repetition maximum test in the Leg-Press 45°,which was preceded by warming up on a stationary bike (CEFISE Biotecnologia esportiva, São Paulo, Brazil) for 10 min and stretching. The loads were increased according toLombardi (10)until the subjects could not perform more than one repetition.

Isokinetic Evaluation

Peak power of knee flexors and extensors were measured by three repetitions at 240º·s-1using an isokinetic dynamometer (Cybex Norm, Ronkokoma, NY).Each subject sat in the bench reclined at 5º with their body and thigh trapped properly. The rotational axis of the dynamometer lever arm was aligned visually to the lateral condyle of the femur and the leg was attached to the dynamometer lever arm in the malleolus region. First, the subject performed a 10-min warm up on stationary bike and then performed a few repetitions to become familiar with the dynamometer. Then, the subject performed three movements of flexion-extension in each measurement. The best attempt was considered (peak).

The 30m Sprint Test

The test was held on the same court in which the subjects trained. Each subject performed three 30m sprints in the greatest speed possible interspersed witha 2-min recovery. The shortest time was considered the best. The test was preceded by a 15-min warm up with exercises involving jogging, coordination, brief accelerations, and stretching. The same subject always applied the testthrough a timer (CITIZEN, Brazil). At the moment the subject started the movement, the timer was started and immediately after passing the 30m line the timer was stopped.

Statistical Analyses

Descriptive statistic was used and data are presented in mean and standard deviation. Data normality was tested by the Shapiro Wilks test. The Spearman correlation r value was used to verify association between variables. The data were treated in software STATISTICA 6.0 (Oklahoma, USA) and significance was fixed atP≤0.05.

RESULTS

Descriptive values for vertical jump, 30m sprint, maximal strength, and peak power of knee flexors and extensors were, respectively:52.5 ± 7.81 cm; 4.63 ± 0.19 sec; 340.64 ± 94.8 kg; 193.64 ± 37.35 W, and 252.81 ± 86.8 W. The correlation coefficients are presented in Tables 1, 2, and 3.

Table 1. Correlation Coefficients between Power and VerticalJump, 30m sprint, and 1-RM.

VerticalJump(cm) / 30m Sprint (s) / 1-RM (kg)
Power Flexors (W) / r = 0.06 (P = 0.82) / r = 0.07 (P = 0.80) / r = 0.59 (P = 0.02)*
Power Extensors (W) / r = 0.06 (P = 0.82) / r = - 0.17 (P = 0.55) / r = 0.67 (P = 0.00)*

*Statistically significant (P<0.05). 1-RM – One repetition maximum.

Table 2. Correlation Coefficients between30mSprintand Vertical Jump and 1-RM.

Vertical jump (cm) / 1-RM (kg)
30m Sprint(sec) / r = -0.59 (p = 0.02)* / r = 0.10 (p = 0.71)

*Statistically significant (P<0.05). 1-RM – One repetition maximum.

Table 3. Correlation Coefficients betweenMotor-Physical Tests and Anthropometric Measures.

Body Mass
(kg) / Lean Body Mass
(kg) / Height
(cm) / % Body Fat
(%)
30m Sprint(sec) / r = 0.24 (P = 0.39) / r = 0.14 (P = 0.63) / r = 0.06 (P = 0.82) / r = 0.08 (P = 0.77)
1-RM (kg) / r = 0.77 (P = 0.00)* / r = 0.78 (P = 0.00)* / r = 0.63 (P = 0.01)* / r = 0.15 (P = 0.58)
VerticalJump(cm) / r = -0.22 (p = 0.44) / r = -0.14 (p = 0.62) / r = -0.10 (p = 0.73) / r = -0.55 (p = 0.03)*
PowerExtensors (W) / r = 0.60 (P = 0.02)* / r = 0.70 (P = 0.00)* / r = 0.54 (P = 0.04)* / r = 0.02 (P = 0.93)
Power Flexors (W) / r = 0.62 (P = 0.01)* / r = 0.63 (P = 0.01)* / r = 0.67 (P = 0.00)* / r = 0.23 (P = 0.40)

*Statistically significant (P<0.05). 1-RM – One repetition maximum.

DISCUSSION

The present study found a negative association between verticaljump and the 30m sprint test in youth basketball players (Table 2), which corroborated the results found byAlemdaroğlu(1)who observed an inverse correlation between the countermovement jump and the 30m sprint test in professionals basketball players(r= -0,619; P<0.05).Likewise, Stojanovic et al.(16)found a negative correlation between dynamic strength (obtained by vertical jump) and repeated sprint ability (r= -0.74; P<0.05) in elite basketball players. Their findings suggest that performing only one high power action is associated with the capacity of maintaining repeated anaerobic efforts. The relative decrease in 30m sprint time was related to the relative improvement of the countermovement jump height (r= -0.63; P≤0.01), after a repeated sprint training period(3).The similar energetic contribution in both tests (i.e., creatine phosphate and glycolytic system) may explain the association between the tests.We found a relationship between values of power of knee flexors and knee extensors in isokinetic dynamometer and maximal strength (Table 1). Our results agree in part with those reported by Baker and Nance(2)who found a significant correlation between maximal strength in the squat exercise and the vertical jump (r=0.81). A possible explanation for this finding is the similar pattern of muscle recruitment in both actions(8).

Although the percentage of body fat and verticaljump was negatively associated, maximal strength was positively related to body mass, lean body mass, and height (Table 3). This indicates that anthropometric values can influence performance, especially in the case of young athletes (5). Ostojic et al.(13)reported a strong inverse relationship between body mass and countermovement jump (r= -0.99; P<0.01) in prepubertal basketball players, which demonstratedthat lowering body mass can positively influence jumping mechanics. Moreover, accordingly to Malina et al.(11), body mass contributes to sprint performance while height contributes to the vertical jump performance.

Although not controlled, age and maturity have also been shown to influence running, strength, and power, particulary between the age of 12 to 15. In boys, there is an increase in testosterone that allows athletes to improve performance in motor-physical tests (4,14). This point is supported by the fact that Vamvakoudiset al.(17)found that puberty is a critical period for the increase in maximal aerobic power. Therefore, it is expected that adolescents in the later stages of puberty exhibit better performance in power exercises and endurance(11)and, consequently, a relationship between these variables. However, Meylan et al.(12)emphasizes that, regardless of maturity, the sprint capacity depends on anthropometric, physiological, and biomechanical factors that can be enhanced with different training programs.

CONCLUSIONS

Significant associations were found between vertical jump and 30m sprint time, power of knee flexors and extensors, and maximal strength. Acorrelation was found between the anthropometric measurements and the physical-motor tests, which indicates that these variables can influence performance (especially in the case of young athletes). Thus, scientific evidence supports the use of simple methodology to assist in the evaluation of the performance of youth basketball athletes.

Address for correspondence: Juan Henrique Szymczak Conde, Departament of Physical Education of Federal University of Parana, Parana, Brazil. Street Sagrado Coração de Jesus. Phone (55) 41 9678-5332. Email:

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