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The Five-Jump Test for Distance as a Field Test to Assess Lower Limb Explosive Power in Soccer Players

Chamari, Karim1; Chaouachi, Anis1; Hambli, Mourad1; Kaouech, Fethi1; Wisløff, Ulrik2; Castagna, Carlo3,4

Journal of Strength and Conditioning Research: May 2008 - Volume 22 - Issue 3 - p 944-950
doi: 10.1519/JSC.0b013e31816a57c6
Original Research
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The 5-jump test (5JT) was proposed to evaluate lower limb explosive power of athletes competing in various disciplines. Although 5JT performance is usually expressed in absolute terms as the overall distance covered (i.e., in meters), subject size can play a significant role in the performance. The aims of the present study were to test the relationship of 5JT absolute performance with laboratory tests for explosive power and to develop performance notations useful to improve the diagnostic value of 5JT. Fifteen elite soccer players, members of the Under-23 Tunisian national team, were tested for 5JT, force platform vertical jumping (squat jump [SJ] and arm-aided countermovement jump [Arm-CMJ]), and concentric isokinetic leg extension/flexion (90°·s−1 and 240°·s−1). 5JT performance was expressed in absolute terms (meters), relative to leg length (5JT-relative) and with body mass-dependent notations (Body mass × 5JT, 5JT-body mass). 5JT performance was significantly correlated with SJ height and scaled (W·kg−0.67) peak power (0.72 and 0.77, respectively, p < 0.01). 5JT-relative values were significantly related to SJ and Arm-CMJ height (0.61 and 0.71, respectively, p < 0.05) and scaled peak power (0.57 and 0.59, respectively, p < 0.05). 5JT-body mass revealed significantly related of SJ (0.82, p < 0.0001) and Arm-CMJ peak power (0.54, p < 0.05) and to SJ and Arm-CMJ peak force (0.67 and 0.65, respectively p < 0.05). 5JT-relative and 5JT-body mass correlated significantly with knee extensors 240°·s−1 (0.60, p < 0.05) and knee flexors 90°·s−1 (0.67, p < 0.01) isokinetic acceleration time, respectively. The results of this study suggest that the 5JT may be regarded as an explosive strength diagnostic tool under field conditions in elite soccer players. The use of performance notation accounting for body size differences may improve the diagnostic ability of 5JT.

1Research Unit on Evaluation, Sport, Health, National Centre of Medicine and Science in Sport, Tunis, Tunisia; 2Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; 3School of Sport and Exercise Sciences, Faculty of Medicine and Surgery, Tor Vergata University, Rome, Italy; 4Scuola Regionale dello Sport delle Marche, Italian Olympic Committee, Ancona, Italy

Address correspondence to Carlo Castagna, castagnac@libero.it.

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Introduction

Soccer is a multifaceted team sport that requires well-developed speed and power to be played at an elite level (12,39), given that a number of laboratory and field tests have been proposed to assess explosive power of selected population of soccer players (38). Recently, vertical jump height was shown to be significantly related to short sprint performance (10-30 meters) in well-trained elite soccer players (39). Furthermore, Arnason et al. (1) showed that vertical jump performance was related to team success in semiprofessional soccer players.

Despite its wide use in soccer (38), vertical jump (height jumped) testing requires specific testing setup and devices (i.e., force platform and switch mats) that may limit its use in field conditions. Additionally, Rampinini et al. (29) showed that vertical jump performance was not related to actual match activities in elite-level professional soccer players.

Recent studies have proposed the 5-jump test (5JT) for distance as a practical alternative to estimate lower limb explosive power of selected population of athletes (5,9,28,34,35,37) including soccer players (31,36).

The 5JT consists of 5 consecutive strides with joined feet position at the start and end of the jumps. With respect to other tests, the 5JT is very easy to perform and does not require any sophisticated equipment. 5JT performance is usually expressed in absolute terms as the overall distance covered (i.e., in meters) and is then very easy to perform. Nevertheless, the height of the subject can play a significant role in the performance since, with equivalent slit, the strides are proportional to the length of the lower limbs, favoring tall athletes. Furthermore, because 5JT involves a body mass displacement within a limited lapse of time, similar absolute distance achievements may require important differences in force/power expression in subjects with different body masses (7). Thus, strategies to account for difference in body size when evaluating athletes' 5JT performance (i.e., relative and absolute performances) might be of great interest for those involved with field testing.

Despite its proposed practicability and utilization (9,28,31,34-37), no study has been carried out in order to specifically investigate the nature of the 5JT and how to express the results of the test in soccer players. Therefore, the aims of the present study were to test the external validity of the 5JT and to improve the diagnostic value of the 5JT in soccer players.

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Methods

Experimental Approach to the Problem

The 5JT is currently used in field conditions with the aim to estimate athletes' lower limb explosive power (9,28,31,34-37) and to measure horizontal stretch-shortening cycle capabilities in the distance traveled using lower limb actions similar to those of the sprint stride usually performed by soccer players (36). Moreover, the 5JT has been recently proposed as test to successfully assess the insurgence of training adaptations in endurance athletes (34,35,37). 5JT performance is usually reported as the total distance covered (in meters); however, this notation may mask differences in body size and thus giving misleading results.

In fact, tall athletes may perform better than shorter ones because of their greater lower limb length. Additionally, heavier subjects may have their 5JT performance underestimated in terms of power expressed (7). In order to improve the diagnostic strength of the 5JT, we proposed relative and body mass-dependent notations that may account for the limitation involved with the absolute expression of results.

As athletic squads are usually composed of subjects differing in body height (38), we proposed a relative expression of 5JT performance (5JT-relative) taking into account the subjects' lower limb length. In order to achieve this, 5JT performance was divided by 5 to obtain an average tread value (1Tread). 1Tread was then divided by the length of the lower limbs (5JT-relative = 1Tread/LgLowLimbs). With the aim of accounting for the difference in body mass between athletes, the absolute 5JT performance was multiplied by the individual body mass (5JT-body mass = 5JT × body mass). This notation was used because it could be considered a rough measure of work performed over the distance jumped by the subject (work = distance × force).

Dimensional scaling should be considered when evaluating strength measures (6,7,17,21,40). In two geometrically similar and quantitatively identical individuals, one may expect all linear dimensions (L) to be proportional. The length of the arms, legs, and individual muscles will have a ratio of L:1, the cross-section area L2:1, and the volume ratio L3:1. Since muscular strength is directly proportional to the muscle cross-sectional area and body mass (mb) varies directly with body volume, whole-body muscular strength measures will vary in proportion to mb0.67. Given that, in the present study, peaks of force, torque, and power variables were therefore expressed in N·kg−0.67, N·m·kg−0.67, and W·kg−0.67, respectively. Dimensional scaling should ideally be based on fat-free mass because fat has very low metabolic activity (2). We chose to use dimensional scaling based on body mass to allow the possibility of direct comparison of our results to other studies (8,16,40).

The work hypothesis was that these new notations could further improve the diagnostic power of the 5JT.

Despite the popularity of the 5JT (9,28,31,34-37), to our knowledge, no studies are currently available investigating the performance components of this field test. Thus, in the present study, 5JT performance expressed either in absolute, relative, or mass-dependent terms was compared with laboratory tests of vertical jump performance (4,14) and isokinetic leg-extension strength testing (32) for external validity and to examine in detail the determining variables of 5JT performance. Information in this context may be of great help to coaches and fitness trainers for training monitoring and prescription.

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Subjects

Fifteen elite-level male soccer players, all members of the Under-23 Tunisian National Olympic team, volunteered to participate in the study. Players' physical characteristics are presented in Table 1. Subjects' body fat percentage was calculated according to the formula of Siri (33) based on four skinfold measurements (biceps, triceps, subscapularis, and suprailiac)(13).

Table 1

Table 1

Before the start of this study, the subjects were informed about the test protocols, but blinded about the aims of the investigation. In order to be included in the investigation, each subject provided written informed consent in accordance with the Declaration of Helsinki. Participants were aware that they could withdraw from the study at any time.

All players were starters in their senior teams participating in the Tunisian national soccer championship. At the time of the experiment, their weekly training schedule included 6-9 training sessions per week (approximately 90 minutes per training session). A training session consisted mainly in soccer training and very rarely in track running or muscular strengthening. Official games took place once weekly, usually on weekends. The investigation was carried out at mid-season while the national team was engaged in the qualifications for the Olympic Games (Athens 2004) and was leading the continental group. The studied cohort was composed of 2 goal keepers, 4 defenders, 6 mid-field players, and 3 forwards. The research design gained clearance from the University of Tunis Ethical Committee before the start of the testing sessions and subject recruitment.

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Testing Protocol

The participants came to the laboratory for a physical examination and anthropometric measurements. Lower limb length was measured by subtracting their seated height from their body height. The players then performed the 2 laboratory tests, and 1 week later performed the field 5JT. Both testing sessions were performed on Wednesday (i.e., away from Sunday official games). Each player was instructed and verbally encouraged to give their maximal effort during all tests. The subjects were familiar with the testing procedures undertaken as they routinely performed these tests as a part of their scientific follow-up. Laboratory testing was scheduled between 9:00 and 11:00 am (19°C) and was performed by the subjects wearing shorts and T-shirts. The 5JT was performed from 10:00 to 11:00 am (18°C) with subjects wearing soccer sportswear. Testing on both days was performed after a standardized caffeine-free breakfast for each player.

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Pretest Warm-up

A standardized warm-up consisting of 10 minutes of jogging and 5 minutes of coordination movements was performed before the lab and field tests. Thereafter, a 5-minute specific warm-up was performed using exercises mimicking and priming test movements. No static passive stretching was allowed during warm-up (10,22,23,27), and 3 minutes of recovery separated the warm-up from the tests.

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Laboratory Testing

Force Plate Vertical Jumping

The subjects performed 2 jumping protocols on a force platform (Kistler 9281 C; Kistler, Winterthur, Switzerland). The first protocol consisted of jumping from a fixed semisquat position with the hands held at the hips [squat jump (SJ)]. The second vertical jump test was a free counter movement jump during which the players freely used their hands while jumping [arm-aided countermovement jump (arm-CMJ)]. Each player performed 3 SJs and 3 arm-CMJs with 2 minutes of rest in between. The best jump of each jumping protocol was selected for analysis. Peak jumping force (Fpeak), peak jumping velocity [peak jumping power (Wpeak), and the peak height of the jumps (Hpeak)] were recorded (8).

Vertical jump performance was used as paradigm for explosive strength and lower limb abilities as recent studies showed that maximal power development is not significantly different between vertical and horizontal jumps (30).

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Isokinetic Testing

Each player was placed in an upright seated position and secured to both the dynamometer (Cybex NORM; Henley Healthcare, Cybex International, Inc., Medway, MA) and the corresponding chair according to manufacturer specifications in order to eliminate extraneous movements and to maintain a constant hip joint angle (90°). Two maximal voluntary measurements were made at 90°·s−1 (1·57 rad·s−1) and 240°·s−1 (4.19 rad·s−1) angular velocities. At each velocity, 3 extension/flexion movements of the leg were allowed as a habituation movement, followed by 1 minute of rest. Thereafter, 5 and 20 maximal extension/flexions were performed at 90°·s−1 and 240°·s−1, respectively, with 2 minutes of recovery between series. Each knee extension/flexion was performed from an initial knee angle of approximately 110° and went through a full range of motion to a final knee angle of 0°. The NORM system sensitivity was set at 5 for both measurements according to the manufacturer's recommendations, and peak torque was calculated and adjusted for the effects of gravity by the NORM system software (27). The right leg was tested first, then after having measured the left leg gravity, the left leg evaluation began. For each angular velocity, the best extension/flexion repetition was kept for analysis of peak torque and mean power. The recorded isokinetic variables were as follows: peak torque (N·m, and N·m·kg−0.67), Mean Power (W and W·kg−0.67), and time to reach the imposed angular velocity [acceleration time (AT) in seconds]. Calculations were performed, averaging the left and right leg values of knee flexor and extensor scores.

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Field Testing

5JT

This test was performed on the grass with the players equipped with appropriate soccer boots. The 5JT consists of 5 consecutive strides with joined feet position at the start and end of the jumps. From the starting joined feet position, the participant was not allowed to perform any back step with any foot; rather, he had to directly jump to the front with a leg of his choice. After the first 4 strides, i.e., alternating left and right feet for 2 times each, he had to perform the last stride and end the test again with joined feet. If the player fell back on completion of the last stride, the test was performed again (only 2 cases of this happening in the present study). 5JT performance was measured with a tape measure from the front edge of the player's feet at the starting position to the rear edge of the feet at the final position. The person assessing the landing had to focus on the last stride of the player in order to exactly determine the last foot print on the grass, as the players could not always stay on their feet on landing. The starting position was set on a fixed point.

Reliability of 5JT performance was assessed before the start of this study, making elite soccer players (n = 67) repeat the test 1 week apart. Results showed an intraclass correlation (ICC) of 0.91 for 5JT performance. The resulting typical error of measure as a coefficient of variation (TEM) was 2.2% (3,18,20). These findings are similar to those previously reported by Slattery et al. (35) for experienced triathletes (TEM = 2.3%, ICC = 0.94).

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Statistical Analyses

Values are expressed as mean ± SD A Pearson correlation matrix was performed among the variables of the vertical jump (Hpeak, Wpeak, Wpeak·kg−0.67, Fpeak) and isokinetic tests (peak torque and AT) and 5JT notations considered as independent variables. Statistical significance was fixed at p ≤ 0.05.

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Results

Results from the different tests are summarized in Table 2. Table 3 shows the main results of the correlation matrix between 5JT performance and vertical jump data. There were significant correlations of both absolute and scaled (kg−0.67) expressions of 5JT performance with all SJ variables except the Fpeak variable. Arm-CMJ variables showed a significant correlation with 5JT-relative and 5JT-body mass performances. 5JT-relative and 5JT-body mass correlated significantly with knee extensors 240°·s−1 (r = 0.60, p < 0.05) and knee flexors 90°·s−1 (r = 0.67, p = 0.006) AT performance, respectively.

Table 2

Table 2

Table 3

Table 3

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Discussion

The present study showed that 5JT performance was significantly correlated with vertical jump height and power variables and 1 explosiveness variable measured during isokinetic testing. Specifically, 5JT-relative was significantly correlated with laboratory tests in more cases than the absolute form (Table 3).

In order to take into account differences in body weight, we estimated the amount of work performed during the 5JT. Results showed that 5JT-body mass was strongly correlated with SJ peak power and to a lesser extent with SJ peak force (r = 0.82, p < 0.0001 and r = 0.67, p = 0.006, respectively). Similarly, arm-CMJ peak power and force were revealed to be significantly related to 5JT-body mass (r = 0.54, p = 0.04 and r = 0.65, p = 0.009, respectively). These findings demonstrate that by simply multiplying 5JT performance by body mass, we can obtain a measure that is significantly related to explosive strength (4).

5JT performance was significantly related to SJ scaled (kg−0.67) power output (r = 0.77, p = 0.001) and to a lesser extent (r = 0.58, p = 0.024) to absolute SJ power output. This means that 5JT performance depends mostly on the explosive strength ability of subjects and that body weight may be regarded as a 5JT performance-limiting factor (7). Peak explosive strength was related to 5JT performance only when expressed with body mass-dependent notation (r = 0.67, p = 0.006 and r = 0.65, p = 0.009 for SJ and arm-CMJ, respectively). These findings were expected as we thought that 5JT-body mass performance could be regarded as a reflection of work exerted during 5JT (work = distance × force). However, because 5JT-body mass was strongly related to SJ power output (r = 0.82, p = 0.000), contraction speed may have influenced performance (power = force × speed). As a result, the 5JT may be regarded as a very useful and simple testing tool that provides information about athletes' stride power, which is considered a crucial variable in many sport activities, such as team sports (26).

Nevertheless, 5JT performance, differently from vertical jump and isokinetic tests, measures horizontal stretch-shortening cycle capabilities in distance (36). Consequently, this may explain why the shared common variance (r2) between 5JT performance and vertical jump and isokinetic peak variables was higher than 50% in only few cases (11). However, although the differences in exercise mode are evident between 5JT and lab tests (i.e., vertical jump and isokinetic extension), the muscular groups recruited are mainly the same. This possibly explains the positive correlations observed in the present study.

The results of the present study show that absolute and body mass-dependent expressions of 5JT performance may be regarded as a valid estimate of explosive power (11) such as that developed during the SJ. Nevertheless, as seen in Table 2, arm-CMJ power and force correlated significantly only with the 5JT-relative and 5JT-body mass, respectively. These findings suggest that the ability to develop high power force peaks during stretch-shortening cycle actions may positively affect 5JT performance when considered in relative or body mass-dependent terms. However, coordination factors may also have had some influence on the relationship between SJ and arm-CMJ with 5JT performance. In fact, studies that addressed the performance difference between arm-CMJ and the SJ showed that muscle coordination may play an important role. This is probably due to coordination factors representing the main difference between the arm-CMJ and the SJ (15,24,25).

Thus, we emphasize the importance of the relative expression of the 5JT, i.e., 5JT-relative, which was found to be correlated with both vertical jump performances (arm-CMJ and SJ) and acceleration time of knee extensors in isokinetic testing.

As it is very easy to perform, sensitive to training effects (28,34), and valid with respect to anaerobic tests, we strongly recommend the use of the 5JT in order to assess soccer players' stride power. Indeed, soccer performance depends not only on endurance and repeated sprint ability, but also on the players' power for a number of actions during the game, even if it is well-known that soccer players are far from being the most powerful athletes (38). In heterogeneous groups of players with respect to body height and mass, the relative expression and the body mass-dependent notation of 5JT performance should be used for comparison purposes (7).

The results of this study indicate that the 5JT may be an appropriate field test for measuring stride power in soccer players. The use of the 5JT as measure of lower limb explosive power is even more attractive because of the limited facilities needed compared to vertical jumping or for reliable short-distance sprinting. As a result, it could be suggested that coaches who do not have direct access to laboratory equipment can use the 5JT to test lower limb horizontal explosive power, a performance variable that is very close to running movement (i.e., logical validity) and other training methods for the development of explosiveness in soccer players (26,36). In addition, 2 simple anthropometric measures (body mass and seated heights) allow the calculation of 5JT performance notations, which are very practical when comparing athletes differing in body size.

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Practical Applications

The study results are similar to those recently reported by Bouhlel et al. (5) for children (age, 12 ± 0.4 years). In that study, a significant relationship was reported between 5JT performance (distance) and CMJ height (r = 0.63, p < 0.01) and relative power (W·kg−1, r = 0.74, p < 0.001). This supports the validity of the 5JT in evaluating lower limb explosiveness.

With respect to 5JT performance, Paavolainen et al. (28) reported values increasing from 12.47 to 13.04 meters in the experimental training group that concomitantly increased its endurance performance. Assuming a body height-to-LgLowLimbs ratio similar to that observed in the present study, the calculated 5JT-relative values of Paavolainen et al. (28) are around 2.94 and 2.92 for the experimental and control groups, respectively. This is very close to the 2.91 mean value found in the present study. This is an average value with respect to stride power. Indeed, the maximal single player values observed are >3.00, (i.e., 3.13) for the present study and 3.22 for a senior player (personal data). Values >3.2 could be interpreted as reflecting good muscular power and values <2.8 as weak values.

Recent studies have shown that the 5JT is a valid test to assess training adaptation in a selected population of athletes (9,28,31,34-37). In this regard, training improvement in 5JT performance should be >2.2% in order to be considered meaningful (18-20) in well-trained soccer players.

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Acknowledgments

The authors thank the coaches Khemaïes Laabidi and Boubaker Hannachi as well as the National Technical Director of the Tunisian Soccer Federation: Belhassen Malouche, and the CNMSS physiotherapists Amel Hammouda and Néjib Tekaïa for their technical support. This study was financially supported by the Ministère de la Recherche Scientifique et du développement des compétences, Tunisia. The authors have no conflicts of interest that are directly relevant to the content of this review.

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Keywords:

soccer; vertical jump; isokinetic; allometric scaling; explosive strength; football

© 2008 National Strength and Conditioning Association