# Relation between different variables of vertical jumps and sprints in Brazilian professional soccer players.

ABSTRACT

Braz TV, Nogueira WJ, Cruz WA, Businari GB, Ornelas F, Brigatto FA, Germano MD, Sindorf MAG, Silva JF, Pellegrinotti IL, Lopes CR. Relation between Different Variables of Vertical Jumps and Sprints in Brazilian Professional Soccer Players. JEPonline 2017;20(1):33-46. The purpose of this study was to investigate the relation between different variables of vertical jumps and sprints in professional soccer players. The study consisted of 25 Brazilian elite soccer players (28.1 [+ or -] 1 yrs, 78.2 [+ or -] 6.8 kg, 1.81 [+ or -] 0.12 m, % Fat = 14.2 [+ or -] 3.2) who were ran the 10 m (S10m) and 20 m (S20m) sprint tests with change of direction at 40 m (20 + 20 m) (Acyclic Sprint) and the Zig-Zag sprint (ZZT) as well as Squat Jumps (SJ) and Counter Movement Jumps (CMJ). The Pearson's linear correlation and the stepwise linear regression model were used to investigate both the relation and the prediction between variables. All the correlations between the variables were significant (P<0.05). The correlation magnitude between S10m-S20m (r=0.83, P<0.0001), SJ-CMJ (r=0.86, P<0.0001), and ZZT-Acyclic Sprint (r=0.79, P<0.0001) were very large. The S20m variable explained 68% (P=0.002) of the performance in S10m (P=0.001), CMJ explained additional 7%, and ZZT, 4%. The S10m variable explained 68% (P=0.001) and ZZT explained additional 9% (P=0.001) of S20m. The CMJ was the only explanatory variable (74%) for SJ (P=0.001) with additional 5% at S10m. The Acyclic Sprint explained 62% (P=0.001) of ZZT with additional 10% at S10m and S20m (P=0.001). It was concluded that the S10m-S20m, CMJ-SJ, and ZZT-Acyclic Sprint relations in the analyzed sample have dependent attributes between each other. The CMJ and SJ did not help in explaining the ZZT and the Acyclic Sprint; whereas, the S10m and S20m had low explanatory power for sprints with change of direction.

Key Words: Agility, Speed, Power, Field Testing, Soccer

INTRODUCTION

High intensity moves such as jumps, sprints, turns, and shifts with change of direction represent 11% of the moves performed by professional soccer players (8). During a match, the players perform 726 turns, of which on average 84% of them occur in a range from 0[degrees] to 90[degrees] to the left or to the right. They are also required to produce motor actions such as jumps and sprints in a short period of time (1 to 7 sec) (2). Brazilian professional soccer players perform 100 sprints ([greater than or equal to]23 km*[h.sup.-1]) on average during the matches, and approximately 65% of them do not exceed 16 m (1). These motor actions represent decisive moments in soccer matches (2,12,22), since sprints are the most frequent moves in score situations for players who perform both the service and the completion of the goal (10).

Rampinini et al. (22), Gonzalez-Badillo and Marques (11), Ingebrigtsen et al. (16) have highlighted the importance of performing field trials to assess the training and to monitor the performance of professional soccer players. Several studies have investigated the relation between the vertical jump tests (8,27) and short-distance sprints with change of direction (17,19) as a means to investigating their association with the players' performance during the match (22), with chronic adaptations to training (15,21,23), and with the performance prediction models of these motor actions (6,18). Rampinini et al. (22) demonstrated that the UEFA European Champions League elite athletes, who showed the shortest time in 6 sprints of 40 m (20 + 20 m, Acyclic Sprint), ran longer distances in the form of sprints during the matches (r = -0.65).

With respect to the chronic adaptations to training, the combination of maximum strength trainings and jumps over 7 wks did not change the 10- and 40-m sprint time of professional soccer players (23). Similarly, agility showed no improvement when sprint training without change of direction was applied alone (24-26). The chronic adjustments described in these studies contrast with the fact that there are significant linear correlations between variables of vertical jumps and sprints with and without change of direction (16,17). Similar neural (e.g., nerve conduction velocity), muscle (e.g., type of recruited muscle fibers), and physiological aspects (e.g., the phosphagen pathway energy predominance) between sprints and jumps led to the assumption that these motor actions are highly related to each other in professional soccer players (13,18).

In fact, several studies have demonstrated the existence of significant linear correlations between vertical jumps (e.g., countermovement jump [CMJ], squat jump [SJ]), sprints at distances of 5, 10, 20, 30, and 40 m, and sprints with change of direction (e.g., Zig Zag Test [ZZT], Illinois Test, t-test) (4,7,11,16,19). However, according to Marques and Izquierdo (20), the relations between variables should be interpreted with caution because correlations do not necessarily mean causality. These authors have demonstrated that the kinematic and kinetic parameters (average strength, time to peak force, mechanical thrust, and force development rate) are different in the execution of vertical jumps (CMJ) and 10-m sprints (S10m). However, there is an association between the S10m time and the peak velocity of vertical jumps (r=0.63).

Little and Williams (18) found a significant association between S10m and ZZT (r=0.35) in professional soccer players from England. But, they pointed out that although the actions are similar, the coefficient of determination ([r.sup.2] = 0.119) explains just 11.9% of the shared variance between the variables. The authors concluded that different factors were related to the performance of such motor actions. Despite the relevance of the study, the variation coefficient was demonstrated through the simple linear association between two variables (S10m vs. ZZT, or S10m vs. S20m, or S20m vs. ZZT). In addition, the study has not presented the joint explanatory power of the correlation among three or more variables in a multiple predictive model (28). Chaouachi et al. (6) tested linear multiple regression models using the stepwise technique in elite professional soccer players. The authors demonstrated the percentage contribution of 15 anthropometric and muscle variables to the performance of two sprint types with change of direction (t-test and 5-m shuttle run sprint). Eight variables were shown to have explanatory power in the t-test ([r.sup.2] = 0.45), and 10 variables, in the 5-m shuttle run sprint ([r.sup.2] = 0.48).

Thus, it is worth highlighting the lack of studies that seek an explanatory multiple regression model that can identify associations between a set of variables of vertical jumps (e.g., CMJ, SJ), sprints with change of direction (ZZT, Acyclic Sprint), and with no change of direction (S10m, S20m) in professional soccer players. Differently from young athletes (17) or from athletes playing at less competitive levels (7), the initial hypothesis addressed in the current study was that the variables representing the same motor action (CMJ vs. SJ, ZZT vs. Acyclic Sprint, S10m vs. S20m) would present greater magnitude correlations among the elite professional soccer players because the players have similar biomechanics. The athletes in the sample have a longer background in the modality and perform specific training regarding the investigated motor actions in the long-term. In addition, despite the similar strength and speed manifestations in motor actions such as sprints and vertical jumps, the joint analysis of the multiple correlations is expected to show the explanatory power percentage of these variables in the interaction between the actions. The purpose of this study is to investigate the relation between different variables of vertical jumps and sprints in Brazilian professional elite soccer players.

METHODS

Subjects

The study consisted of 25 professional soccer players (28.1 [+ or -] 1 yrs, 78.2 [+ or -] 6.8 kg, 1.81 [+ or -] 0.12 m, % Fat = 14.2 [+ or -] 3.2) from a Brazilian elite team. All volunteers were informed about the procedures and signed the consent form after the research was approved by the Research Ethics Committee in the local institution (protocol 80/12). All athletes had a history of at least 6 yrs of systematized training in the modality (e.g., 10 to 12 training sessions 14 to 16 hrs a week). They showed no injuries in the three previous months and were not using any type of medication.

The subjects were familiar with the tests (S10m, S20m, ZZT, Acyclic Sprint, CMJ and SJ), given that they had previously performed them in at least 2 separate occasions in the previous seasons. Except for the vertical jumps, all tests were performed on natural grass surface in the team-training field. The temperature ranged from 22 to 25[degrees]C, with relative humidity between 36 and 46%. The subjects performed 8-min of jogging and 7-min of coordination exercises (skipping, short shifts, sprints, and jumps) to warm up before the tests. Static stretches were not performed. The athletes rested the day before the assessments. They were instructed to keep nutrition and hydration states similar to those of the normal training practices. They were also told to avoid drinking stimulating beverages 24 hrs before the procedures.

Procedures

Experimental Approach to the Problem

A cross-sectional study design was applied to male Brazilian soccer players from a national elite professional team. The study was conducted at the beginning of the preparatory period (week 2) for the tournament season. The assessments were performed on two different days, during the morning (9 to 11 a.m.). With respect to the 1st day, sprint tests were performed at 10m (S10m) and 20m (S20m) with change of direction (shuttle running) at 20m, thus totaling 40m (acyclic sprint). As for the 2nd day, vertical jump tests using Squat Jump (SJ) and counter movement jump (CMJ) were performed, as well as the Zig-Zag sprint test (ZZT). The performance in the 10- and 20-m sprints was selected because they represented the distance covered in sprints during soccer matches; whereas, the protocols of vertical jump (SJ - CMJ) and sprint with change of direction (ZZT - Acyclic Sprint) were selected because they are commonly used to assess athletes in such sport modality. In addition, these actions are essential to goal situations during the matches (10). The association between dependent variables was set using the Pearson's correlation and stepwise linear regression model prediction after data collection was over.

Sprints Tests

The athletes stood still before the starting line (50 cm) and performed the sprint at top speed at the distance of 10 m and 20 m in a straight line, 20 m in zig zag (ZZT), and 20 m shuttle running, thus totaling 40 m (20 + 20 m = Acyclic Sprint). Each subject made 3 attempts in each distance with a 2-min interval between each stimulus. The best results for S10m, S20m, ZZT, and acyclic sprint were taken into consideration. The Zig Zag Test consisted of performing a sprint with a change of direction at 20 m distance. The soccer players changed direction every 5 m and performed three 100[degrees] turns (18). As for the acyclic sprint, the subjects performed a 20 m sprint up to the marked points (cones) and immediately after they returned to the starting point in a 180[degrees] turn, thus featuring the shuttle running regime (22). The Speed Test 6.0 CEFISE[R] (Nova Odessa, SP, Brazil) photocell system was used to measure the time in the sprints.

Vertical Jump Height Tests

Vertical jumps such as the Squat Jump (SJ) and the Counter Movement Jump (CMJ) were assessed. During the assessment, each subject was allowed to make three attempts, which were separated by 1-min recovery. The best SJ and CMJ were taken into consideration in the analysis. In order to perform the CMJ, the subjects stood upright with knees extended at 180[degrees] with the hands positioned at the waist. The vertical jump was performed with counter movement. The knee flexion occurred at approximately 120[degrees], then, the subjects extended their knees, trying to propel the body upward and vertically. The trunk remained motionless during the action in order to avoid affecting the height of the jump. The knees remained extended during the flight and landing phases.

The SJ followed the same procedures, except for the initial position. In this case, the subjects stood with their hands on the hips, the knees were bent at 90[degrees] for a period of 2 to 3 sec, and then they performed the jump. The jumps were analyzed in an Ergo Jump[R] contact platform connected to the Jump Test Pro 2.10[R] software (CEFISE, Nova Odessa, SP, Brazil). It is a platform comprising electronic-circuits. It measures how long the subject stayed away from the platform during the jump. It has millisecond precision and calculates the gravity center elevation in centimeters and millimeters, using the formula suggested by Bosco and colleagues (3): jump height = time2 x gravity x 8-1.

Statistical Analyses

The normality and homoscedasticity of the variances were verified through the Shapiro-Wilk and Levene tests, respectively. The mean and standard deviation (SD) were used after data normality and homoscedasticity were assumed. The intraclass correlation coefficient (ICC) was used to verify the reliability on the performance of sprints and vertical jumps, according to the criterion by Cortina (9), wherein r [greater than or equal to] 0.80 may be considered excellent. The relation between variables (S10m, S20m, ZZT, Acyclic Sprint, SJ, and CMJ) was determined through the Pearson's correlation using the SPSS software (version 21.0; SPSS, Inc., Chicago, IL, USA). The confidence interval (95% CI) of the association between variables was calculated.

The following criteria were adopted in order to interpret the correlation magnitude: [less than or equal to]0.1, trivial; >0.1-0.3, small; >0.3-0.5, moderate; >0.5-0.7, large; >0.7-0.9, very large; and >0.9-1.0, extremely large (14). Six separate stepwise multiple linear regression models were used to identify speed, agility, and muscle power of the lower limb variables that have best explained the performance variance in such motor skills. The S10m, S20m, ZZT, Acyclic Sprint, CMJ, and SJ were considered dependent variables (individually) and their combination was considered the independent variables. Variables with F value <4 were removed from the model in the backward procedure. The GPower software (version 3.1.3; University of Dusseldorf, Dusseldorf, Germany) was used to calculate the sample. It adopted 0.75 effect size (E' = 0.05) and 80% statistical power, thus leading to the minimum number of 15 subjects. The significance level was P[less than or equal to]0.05.

RESULTS

Table 1 shows the descriptive results of the mean and standard deviation of the variables, as well as the ICC. The ICC found in the variables of vertical jumps and sprints with and without change of direction showed high reliability between test attempts (r [greater than or equal to] 0.913, P>0.001). All the associations between the variables of sprints and vertical jumps were significant (P<0.05) (Table 2). The magnitude of the very large correlation between variables such as S10m-S20m (r = 0.83, 95% Cl = 0.64 to 0.92, P<0.0001), SJ-CMJ (r = 0.86, 95% Cl = 0.70 to 0.94, P<0.0001), and ZZT-Acyclic Sprint (r = 0.79, 95% Cl = 0.57 to 0.90, P<0.0001) was found. Figure 1 shows the result of individual values of very large correlation (r = 0.70-0.90) between S10m-S20m, SJ-CMJ, and ZZT-Acyclic Sprint variables.

The stepwise multiple linear regression model used independent variables (S10m, S20m, ZZT, Acyclic Sprint, CMJ, and SJ) to explain the variance in the performance of sprints and vertical jumps (Table 3). The S20m variable explained 68% (P=0.002) of the performance in S10m; whereas, CMJ and ZZT represented additional 7% (P=0.002) and 4% (P=0.001) increase in it. The S10m variable explained 68% (P=0.001) of the performance in S20m; whereas, ZZT explained additional 9% (P=0.001) in it. The CMJ was the only independent variable (74%) for SJ (P=0.001); whereas, SJ explained 74% performance in the CMJ variable with additional 5% in the S10m one.

As for the agility variables, the Acyclic Sprint explained 62% (P=0.001) of ZZT, with additional 5% (P=0.001), and the S10m, 5% (P=0.001). The ZZT explained 62% (P=0.001) of Acyclic Sprint, with additional 2% in S20m (P=0.002) and 3% in S10m (P=0.002). No other variable was selected through the stepwise linear regression model (F <4).

DISCUSSION

The current study investigated the relationship between vertical jumps and sprints with and without change of direction among Brazilian professional soccer players. Significant correlations were found between all the studied variables. The magnitude of the correlation between the S10m-S20m (r = 0.83), SJ-CMJ (r = 0.86), and ZZT-Acyclic Sprint (r = 0.79) variables was very large. The initial study hypothesis that these variables were similar motor action manifestations in soccer players was confirmed. In addition, it was possible to establish an explanatory multiple regression model to demonstrate, in percentage, the performance contribution degree of each analyzed variable. According to the findings, the vertical jump variables (CMJ and SJ) did not help explaining the ZZT and Acyclic Sprint performances; whereas, the S10m and S20m variables showed low explanatory power ([less than or equal to]5%) for sprints with change of direction.

The variables monitored in the current study (S10m, S20m, ZZT, Acyclic Sprint, CMJ, and SJ) emphasized different motor actions performed by soccer players during the matches. The literature often investigates these variables in professional teams in such sport modality (16,18,22) since they are the most frequent movements in goal completion situations (10). The results show the relationship between vertical jumps and sprints with and without change of direction among soccer players (Table 2). Koklu et al. (17) emphasized that these motor actions are featured by high force production in short time periods (force development rate), and that they have similarities such as the speed and frequency of motor unit recruitment in the skeletal muscle. In addition, the variables of vertical jumps and sprints are all-out stimuli (maximum), which last less than 8 sec with prevalent energy supply through the phosphagen pathway (5).

The relation between these variables has been demonstrated in other studies. Little and Williams (18) analyzed 106 professional soccer players from the 1st and 2nd divisions in England and found significant correlations between S10m and S20m (r = 0.623), S10m and ZZT (r = 0.346), and between S20m and ZZT (r = 0.458). Significant correlations were found between 10 m and 30 m sprints (r = 0.60), CMJ and S10m (r = 0.45), and CMJ and 30 m sprint (r = 0.74) in Brazilian elite players under 20 yrs of age (27). The correlation values found in the current study (S10m-S20m r = 0.83, S10m-ZZT r = 0.47, S20m-ZZT r = 0.65, S10m-CMJ = -0.69) are higher than those reported by Little and Williams (18) and Silva Junior et al. (27) for jumps and sprints with and without change of direction.

Professional soccer players from the 1st, 2nd and 3rd divisions in Norway presented r =0.949 for S10m and S20m (16), and very large correlation magnitude (r = 0.83) similar to that found in the current study, which was conducted with Brazilian professional soccer players. The relationship between sprints with change of direction (ZZT) and vertical jumps (SJ-CMJ) was also reported by Koklu et al. (17) (ZZT- SJ, r = -0.71; ZZT-CMJ, r = -0.77). These values were higher in SJ and CMJ than in ZZT in comparison to those found in the current study (ZZT- SJ, r = -0.51; ZZT-CMJ, r = -0.53). Factors such as age, competitive level, as well as the frequency and volume of training in the sport modality may explain the similarities and the different values found between the studies. However, the results found in the literature, along with those described in the present study, demonstrate the relationship between variables such as vertical jumps and sprints with and without change of direction in soccer players.

On the other hand, it is noteworthy that despite the similar relationships and manifestations, the vertical jumps and sprints with and without change of direction are motor actions that have different biomechanics. Marques and Izquierdo (20) investigated kinetic and kinematic parameters of vertical jumps by correlating them with sprints without change of direction. The authors found significant associations between the 10 m sprint time and the peak velocity during the CMJ (r = 0.630), as well as no significant associations between sprint and variables such as force, mechanical drive, and force development rate in the vertical jump. Despite the relation between vertical jumps and sprints (Table 2), it is necessary to take into consideration the motor gesture in the specific power action manifestation among soccer players.

Thus, the results in Figure 1 show that only the significant correlations found between power actions with similar motor gesture - S10m vs. S20m (r = 0.83), SJ vs. CMJ (r = 0.86), and ZZT vs. Acyclic Sprint (r = 0.79) - showed very large magnitude (r [greater than or equal to] 0.70). In addition, the correlation coefficients ([r.sup.2]) 68%, 73% and 62% were found between these variables, respectively. According to Thomas, Nelson, and Silverman (28), whenever the shared variance between two variables is greater than 50%, it indicates that they have dependent and specific nature (i.e., there is variation and influence of one variable on the other). Therefore, S10m-S20m, CMJ-SJ, and ZZT-Acyclic Sprint showed dependent attributes between each other among the elite professional soccer players analyzed in the current study. The coefficient of determination ([r.sup.2]) was lower than 50% in all the other investigated relations (Table 2, values between 22 and 48%). Thus, the values found in S10m-S20m, CMJ-SJ and ZZT-Acyclic Sprint are justified because they represent similar pattern of motor gesture and movement biomechanics (i.e., they are representative of vertical jumps or sprints with or without change of direction).

Sheppard and Young (25) highlighted the difference between performing sprints with and without change of direction. According to the authors, factors such as deceleration, braking, body balance, and cognitive components (movement choice reaction) are different between the cyclic and acyclic sprints. The synchronicity of reactive forces between the ground and the gravity center shift in the sprint is different (13). In addition, sprints with change of direction performed by soccer players have lower energy consumption than the linear sprints (i.e., the deceleration phase promotes lower metabolic demand that cannot be compensated in the acceleration phase, in comparison to that of cyclic sprints) (12). These statements find support in values reported by Little and Willians (18) for professional soccer players (S10m vs. ZZT, [r.sup.2] = 0.119), as well as in the results of the current study (S10m vs. ZZT, [r.sup.2] = 0.22; S10m vs. Acyclic Sprint, [r.sup.2] = 0 32).

However, it is worth emphasizing that most studies analyzed the relation between vertical jumps and sprints with and without change of direction among soccer players using simple linear correlation (8,17-19,27). This type of treatment allows for analyzing a variable by comparing it to the other variable (28). Thus, using a stepwise multiple regression model, the present study demonstrated how the variables interact jointly to explain the motor actions (Table 3). The vertical jumps (CMJ and SJ) did not help to explain the performance of sprints with change of direction (ZZT and Acyclic Sprint). The S10m and S20m variables explained, together, less than 6% of the performance in acyclic sprints and 11% of ZZT in elite professional soccer players. Although the variables showed significant correlations (Table 2) in a multiple analysis model, it was clear that the shared variance between vertical jumps and sprints with and without change of direction among elite professional soccer players had little explanatory power ([less than or equal to]11%).

This information is important in helping to organize trainings for professional soccer players. It also seems to relate to studies that found chronic adaptations to sprints and vertical jumps in the sport modality. Training sprints without change of direction for 10 wks did not increase the performance in sprints with change of direction among female elite professional soccer players (24). It was not possible to verify the positive effect on amateur soccer players who performed 10 and 20m sprints for 4 wks in trainings with jumps on different surfaces (15). The training with jumps was not able to improve the 20m sprint even among young players (21). In addition, the combination of jumps and maximum strength training did not improve the performance in sprints without change of direction among elite professional soccer players (23).

The evidences in the studies are still insufficient to demonstrate the effect of training jumps on the performance of sprints with or without change of direction, mainly among professional soccer players (24,26). Thus, it is assumed that the information about the specificity of these motor action manifestations, as it was proposed in the current study, may provide the basis for better understanding the chronic responses to the training of vertical jumps and sprints with or without change of direction in soccer. In other words, since the controlled variables showed little or no explanatory power together, training sessions should be prioritized with motor gesture similar to motor actions, as it was highlighted in longitudinal studies comprising sprints (23-25) and vertical jumps (15).

The results of the current study allow concluding that there are significant linear correlations between all the herein studied vertical jump and sprint variables. The S10m-S20m (Sprint without change of direction), CMJ-SJ (Vertical Jumps) and ZZT-Acyclic Sprint (Sprint with change of direction) relation showed dependent attributes between each other in the analyzed sample, and it confirmed the initial study hypothesis that these variables are similar manifestations of motor actions performed by professional elite soccer players. The vertical jump variables (CMJ and SJ) did not help in explaining the ZZT and Acyclic Sprint performance when they were analyzed together; whereas, the S10m and S20m variables showed low explanatory power for sprints with change of direction.

CONCLUSIONS

The results in the present study showed correlation between vertical jumps and sprints with and without change of direction among professional soccer players. These actions depend on the ability of players to produce force in the lower limbs in a short period of time. However, the different biomechanics of these motor actions reflect the degree of determination in the studied variables; the vertical jumps showed attributes relatively independent from those of the sprints. In addition, the change of direction during the sprint performed by the soccer players had low explanatory power in the same action performed in a linear way. These findings may be used by coaches to adjust the organization of speed, agility, and lower limb muscle power trainings since the variables are related. However, the improvement in the performance of such motor actions depends on stimuli with specific biomechanics, such as vertical jumps and sprints with and without change of direction, mainly when the sample comprises elite professional soccer players who depend exclusively on the principle of specificity to improve their performance.

Address for correspondence: Charles R. Lopes, PhD, Universidade Metodista de Piracicaba (UNIMEP)--Campus Taquaral. Rodovia do Acucar, km 156, Piracicaba, SP, Brasil. 13400-911. charles_ricardo@hotmail.com

REFERENCES

(1.) Barros RML, Misuta MS, Menezes RP, Figueroa PJ, Moura FA, Cunha SA, et al. Analysis of the distances covered by first division brazilian soccer players obtained with an automatic tracking method. J Sports Sci Med. 2007;6:233-242.

(2.) Bloomfield J, Polman R, O'Donoghue P. Physical demands of different positions in fa premier league soccer. J Sports Sci Med. 2007;6:63-70.

(3.) Bosco C, Belli A, Astrua M, Tihanyi J, Pozzo R, Kellis S, et al. A dynamometer for evaluation of dynamic muscle work. Eur J Appl Physiol Occup Physiol. 1995;70: 379-386.

(4.) Buchheit M, Samozino P, Glynn JA, Michael BS, Al Haddad H, Mendez-Villanueva A, et al. Mechanical determinants of acceleration and maximal sprinting speed in highly trained young soccer players. J Sports Sci. 2014;32:1906-1913.

(5.) Chamari K, Padulo J. "Aerobic" and "Anaerobic" terms used in exercise physiology: A critical terminology reflection. Sport Med--Open. 2015;1:1-4.

(6.) Chaouachi A, Manzi V, Chaalali A, Wong DP, Chamari K, Castagna C. Determinants analysis of change-of-direction ability in elite soccer players. J Strength Cond Res. 2012;26:2667-2676.

(7.) Comfort P, Bullock N, Pearson SJ. A comparison of maximal squat strength and 5-,10-, and 20-meter sprint times, in athletes and recreationally trained men. J Strength Cond Res. 2012;26:937-940.

(8.) Comfort P, Stewart A, Bloom L, Clarkson B. Relationships between strength, sprint, and jump performance in well-trained youth soccer players. J Strength Cond Res. 2014;28:173-177.

(9.) Cortina JM. What is coefficient alpha? An examination of theory and applications. J Appl Psychol. 1993;78:98-104.

(10.) Faude O, Koch T, Meyer T. Straight sprinting is the most frequent action in goal situations in professional football. J Sports Sci. 2012;30:625-631.

(11.) Gonzalez-Badillo JJ, Marques MC. Relationship between kinematic factors and countermovement jump height in trained track and field athletes. J Strength Cond Res. 2010;24:3443-3447.

(12.) Hader K, Mendez-Villanueva A, Palazzi D, Ahmaidi S, Buchheit M. Metabolic power requirement of change of direction speed in young soccer players: Not all is what it seems. PLoS One. 2016;11:e0149839.

(13.) Haugen TA, Tannessen E, Hisdal J, Seiler S. The role and development of sprinting speed in soccer. Int J Sports Physiol Perform. 2014;9:432-441.

(14.) Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science. Med Sci Sports Exerc. 2009;41:3-13.

(15.) Impellizzeri FM, Rampinini E, Castagna C, Martino F, Fiorini S, Wisloff U. Effect of plyometric training on sand versus grass on muscle soreness and jumping and sprinting ability in soccer players. Br J Sports Med. 2008;42:42-46.

(16.) Ingebrigtsen J, Brochmann M, Castagna C, Bradley PS, Ade J, Krustrup P, et al.

Relationships between field performance tests in high-level soccer players. J Strength Cond Res. 2014;28:942-949.

(17.) Koklu Y, Alemdaroglu U, Ozkan A, Koz M, Ersoz G. The relationship between sprint ability, agility and vertical jump performance in young soccer players. Sci Sports. 2015;30:e1-e5.

(18.) Little T, Williams AG. Specificity of acceleration, maximum speed, and agility in professional soccer players. J Strength Cond Res. 2005;19:76-78.

(19.) Lopez-Segovia M, Marques MC, van den Tillaar R, Gonzalez-Badillo JJ. Relationships between vertical jump and full squat power outputs with sprint times in 21 soccer players. J Hum Kinet. 2011;30:135-144.

(20.) Marques MC, Izquierdo M. Kinetic and kinematic associations between vertical jump performance and 10-m sprint time. J Strength Cond Res. 2014;28:2366-2371.

(21.) Ramirez-Campillo R, Meylan C, Alvarez C, Henriquez-Olguin C, Martinez C, Canas-Jamett R, et al. Effects of in-season low-volume high-intensity plyometric training on explosive actions and endurance of young soccer players. J Strength Cond Res. 2014;28:1335-1342.

(22.) Rampinini E, Bishop D, Marcora SM, Ferrari Bravo D, Sassi R, Impellizzeri FM. Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players. Int J Sports Med. 2007;28:228-235.

(23.) Ronnestad BR, Kvamme NH, Sunde A, Raastad T. Short-Term effects of strength and plyometric training on sprint and jump performance in professional soccer players. J Strength Cond Res. 2008;22:773-780.

(24.) Shalfawi SAI, Haugen T, Jakobsen TA, Enoksen E, Tannessen E. The effect of combined resisted agility and repeated sprint training vs. strength training on female elite soccer players. J Strength Cond Res. 2013;27:2966-2972.

(25.) Sheppard JM, Young WB. Agility literature review: Classifications, training and testing. J Sports Sci. 2006;24:919-932.

(26.) Silva JR, Nassis GP, Rebelo A. Strength training in soccer with a specific focus on highly trained players. Sport Med--Open. 2015;1:2-27.

(27.) Silva-Junior CJ, da Palma A, Costa P, Pereira-Junior PP, Barroso R de CL, Abrantes-Junior RC, et al. Relationship between the sprint and vertical jumps 'power in young soccer players. Motricidade. 2011;7:5-13.

(28.) Thomas, J, Nelson, J, Silverman, S. Research Methods in Physical Activity. (7th Edition). Champaign, IL: Human Kinetics, 2015.

Tiago Volpi Braz (1,2), Wagner Jose Nogueira (1), Wallace de Assis Cruz (1,2), Guilherme Borsetti Businari (1), Felipe de Ornelas (1), Felipe Alves Brigatto (1), Moises Diego Germano (1), Marcio Antonio Gonsalves Sindorf (1), Juliano Fernandes da Silva (4), Idico Luiz Pellegrinotti (1), Charles Ricardo Lopes (1,3)

(1) Methodist University of Piracicaba, Human Performance Research Laboratory, SP, Piracicaba, Brazil, (2) Faculty of Americana, Americana, SP, Brazil, (3) Faculty Adventist of Hortolandia, Hortolandia, SP, Brazil, (4) Federal University of Santa Catarina, Florianopolis, SC, Brazil
```Table 1. Descriptive Values of Variables such as Sprints and Vertical
Jumps by Brazilian Professional Soccer Players.

Variables                   Mean
(N = 25)                    [+ or -] Standard Deviation

10 m Sprint (sec)            1.84 [+ or -] 0.09
20 m Sprint (sec)            3.12 [+ or -] 0.12
Zig Zag Test (sec)           5.90 [+ or -] 0.22
Acyclic Sprint (sec)         7.46 [+ or -] 0.22
Squat Jump (cm)             39.8  [+ or -] 4.2
Counter Movement Jump (cm)  47.8  [+ or -] 5.5

Variables                   ICC        SEM
(N = 25)                    (r)

10 m Sprint (sec)           0.913 (*)  0.08
20 m Sprint (sec)           0.965 (*)  0.12
Zig Zag Test (sec)          0.923 (*)  0.18
Acyclic Sprint (sec)        0.926 (*)  0.17
Squat Jump (cm)             0.978 (*)  3.9
Counter Movement Jump (cm)  0.981 (*)  5.1

ICC = intraclass correlation coefficient, SEM = standard error of the
mean (*) P<0.001.

Table 2. Values of the Correlations Found between the Variables of
Sprints and Vertical Jumps in Brazilian Professional Soccer Players.

Variable 1 vs.   Variable 2      r =    95% CI =        [r.sup.2] =

20 m Sprint      0.83   0.64 a 0.92    0.68
ZZT              0.47   0.09 a 0.73    0.22
10 m Sprint vs.  SJ              -0.60  -0.80 a -0.26   0.36
CMJ             -0.69  -0.85 a -0.41   0.48
Acyclic Sprint   0.56   0.21 a 0.78    0.32
ZZT              0.65   0.35 a 0.83    0.43
SJ              -0.54  -0.77 a -0.19   0.29
20 m Sprint vs.  CMJ             -0.58  -0.79 a -0.24   0.33
Acyclic Sprint   0.61   0.28 a 0.81    0.37
SJ              -0.51  -0.75 a -0.14   0.26
ZZT vs.          CMJ             -0.53  -0.76 a -0.17   0.28
Acyclic Sprint   0.79   0.57 a 0.90    0.62
CMJ              0.86   0.70 a 0.94    0.74
SJ vs.           Acyclic Sprint  -0.50  -0.74 a -0.12   0.25
CMJ vs.          Acyclic Sprint  -0.54  -0.77 a -0.18   0.29

Variable 1 vs.   P =      Magnitude

<0.0001  very large
0.0176  moderate
10 m Sprint vs.   0.0016  large
0.0001  large
0.0034  large
0.0004  large
0.0051  large
20 m Sprint vs.   0.0025  large
0.0012  large
0.0096  large
ZZT vs.           0.0068  large
<0.0001  very large
<0.0001  very large
SJ vs.            0.0118  moderate
CMJ vs.           0.0055  large

ZZT = Zig Zag Test, SJ = Squat Jump, CMJ = Counter Movement Jump

Table 3. Multiple Regression of Variables such as Sprints and Vertical
Jumps Performed by Brazilian Professional Soccer Players.

Dependent                                 r =     [R.sup.2] =
Independent variables
variable

S20m                           0.83    68%
S10m       S20m + CMJ                     0.87    75%
S20m + CMJ + ZZT               0.89    79%
S10m                           0.83    68%
S20m
S10m + ZZT                     0.88    77%
SJ         CMJ                            0.86    74%
SJ                             0.86    74%
CMJ        SJ + S10m                      0.89    79%
Acyclic Sprint                 0.79    62%

Acyclic Sprint + S20m          0.82    67%
ZZT        Acyclic Sprint + S20m + S10m   0.85    72%

ZZT                            0.79    62%
Acyclic    ZZT + S20m                     0.80    64%
Sprint     ZZT + S20m + S10m              0.82    67%

Dependent  [R.sup.2]  F value =
variation
variable

68%       49.504
S10m       + 7%       33.202
+ 4%       14.526
68%       49.504
S20m
+ 9%       37.311
SJ          74%       64.086
74%       64.086
CMJ        + 5%       40.321
62%       37.616

+ 5%       22.071
ZZT        + 5%        9.947

62%       37.616
Acyclic    + 2%       19.301
Sprint     + 3%       14.328

ZZT = Zig Zag Test, SJ = Squat Jump, CMJ = Counter Movement Jump
```
COPYRIGHT 2017 American Society of Exercise Physiologists
No portion of this article can be reproduced without the express written permission from the copyright holder.