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Original Research

Test-Retest Reliability of Three Different Countermovement Jumping Tests

Slinde, Frode1,3; Suber, Cathrine2; Suber, Louise2; Edwén, Cecilia Elam2; Svantesson, Ulla2

Author Information
Journal of Strength and Conditioning Research: March 2008 - Volume 22 - Issue 2 - p 640-644
doi: 10.1519/JSC.0b013e3181660475
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Abstract

Introduction

It is important to have access to accurate measuring tools to be able to measure the effects of an intervention or to evaluate the physical fitness among athletes in different sports. Measuring instrument should ideally provide data with high reproducibility since large variations in test results have been reported (4). Jumping is a movement that requires complex motor coordination between upper- and lower-body segments. The propulsive action of the lower limbs during a vertical jump has been considered particularly suited for evaluating explosive characteristics of sedentary individuals and elite athletes (2,12). The ability to develop power is important in many sports, for example, football, ice hockey, handball, and track-and-field athletics. A dominant factor in these sports is explosive strength, where the body or a tool shall accelerate in the fastest possible speed, in the shortest possible time. To assess specific training or an intervention in these sports the countermovement jump (CMJ) is a common test (1,3,17). A standardized CMJ uses a combined eccentric/concentric muscle action defined as a stretch-shortening cycle (SSC) (9,10).

A CMJ starts with the subject standing in an upright position. A fast downward movement to about 90° knee flexion immediately followed by a fast upward vertical movement as high as possible, all in one sequence. Earlier studies have shown that a CMJ is a reliable test to evaluate the explosive strength in the lower extremity extensor muscles in athletes (3,12). CMJ is often performed by using a contact mat which measures flight time and calculates jump height. The Abalakow jump (AJ) is also a CMJ, but it is performed with a measuring tape attached to a belt, which is placed on the hip. Jump height is calculated by the difference between pre- and postjump measurements (8).

In a study by Markovic et al. (12), 5 field tests to assess explosive strength were evaluated regarding reliability and validity. Two of the jumps included were the CMJ and the AJ with arm swing and without arm swing. CMJ showed to be the most reliable and valid test for the estimated explosive power of the lower limbs in physically active men. The AJ without arm swing showed an overall higher result, as much as 11 centimeters when compared with the CMJ without arm swing. AJ had the lowest reliability coefficient among the vertical jumps performed (12).

Both the CMJ and the AJ can be performed either with arm swing or with the hands placed on the hips. Jumps with arm swing have shown to contribute with 8-11% of the jumping height and thus give a more positive effect on the outcome (6). Lees et al (11) also showed that the subjects jumped higher (8.6 cm) using arm swing compared to the no-arm swing condition.

Kettonen et al. (7) evaluated lifetime athletic activity concerning the ability to perform a vertical jump. Lower-limb explosive strength was measured with vertical jump height on a contact mat. Male runners, soccer players, weightlifters and shooters were tested. Hours spent in team training during the past 12 months and the hours spent during their lifetime in power training were associated with improved vertical jump height.

Body composition has shown to be a predictor of physical performance (14,15). Okely et al. (13) showed that children and adolescents ability to perform fundamental movement skills significantly correlated to body mass index, BMI and waist circumference. Relationships between jumping performance, muscle strength and body composition such as lean body mass as well as the percentage of fat and muscle tissue were measured in elite junior basketball players and body composition showed to have a moderate impact (18). Body composition can be a predictable factor among people when it comes to physical performance, but when it comes to elite athletes this factor might be of less importance. Studies have shown that the higher the percentage of body fat, the poorer the person's performance. This is true of all activities in which the body weight must be moved through space, such as in sprinting and long jumping. In general, leaner athletes' perform better. The aims of this study were to determine test-retest reliability of AJ and CMJ on a contact mat with and without arm-swing and to correlate jump height with body composition and physical activity.

Methods

Experimental Approach to the Problem

Jump height, body composition, and physical activity were assessed on one occasion. About 1 week later, a retest jump was performed. Test-retest jumps were performed with a median of 7 (4-14) days' interval. The participants were randomly assigned to start with CMJ or AJ. Before each test, the participants were asked to jog for a couple of minutes and to perform 6 jumps on a submaximal level for familiarization. During testing, no verbal encouragement took place, which was consistent throughout all tests and retests.

Subjects

Thirty women (n = 13) and men (n = 17) between 18 and 25 years participated in the study. Written information and oral instructions were given to each participant before each test and all participants gave oral consent of participation. The participants were physiotherapy and technical students, colleagues, and acquaintances of the authors, and none of the participants performed exercise on an elite level. Mean (SD) age of the women was 23 (1) years and for the men 22 (2) years. Mean body weight, height, and body mass index were 61 (9) kg, 167 (5) cm, and 21.7 (2.4) kg·m−2 for the women and 77 (8) kg, 180 (6) cm, and 23.8 (1.9) kg·m−2 for the men.

Procedures

A CMJ with arm swing or with hands on the hips was performed with the subject standing on a contact mat (Time-it®, Eleiko sport, Halmstad, Sweden) with the legs in a hip wide position. A fast downward movement to about 90° knee flexion immediately followed by a fast upward vertical movement as high as possible all in one sequence. When landing, both feet have to be within the frames of the contact mat. Three maximal jumps were performed and the highest result was registered as the final result. When performing CMJ without arm swing they kept their hands on their hips throughout the jump.

The AJ test was performed with a measuring tape attached to a special belt, which was placed on the hip. The measuring tape was then put underneath a ruler that was attached on the floor with tape (8). The subjects had the feet as close to the ruler as possible. The measuring tape was straightened and the number above the ruler on the measuring tape was written down. After the jump the number where the measuring tape stopped was also written down. The difference between the two numbers was registered. Three maximal jumps were performed and the highest result was registered as the final result.

Body weight was measured on a Soehnle body scale and self-reported body height were used to calculate BMI as body weight (kg) divided by squared body height in meters. Body composition was assessed using single-frequency bioelectrical impedance. Before each test the participants lied down and rested for a period of 10 minutes. Four electrodes were attached to the right side of the body, at the ankle, the foot at metatarsal II, the wrist and the back of the hand at metacarpal II. A low current passed through the two distal electrodes (hand and foot) and the two proximal electrodes received the flow. Reactance, resistance and the impedance were measured by RJL-101 Akern equipment (Florence, Italy) and body composition was calculated using manufacturer supplied equations. The results are expressed as body fat %. During the rest preceding the bioelectric impedance assessment, the participants filled in a form regarding their physical activity. The Activity registration form (5) referred to the physical activity during the last month.

Statistical Analyses

Because of the small sample size and variables that were not normally distributed, non-parametric tests were used. The results were calculated with Spearman's rank coefficient (rs) and Wilcoxons Signed Rank Test. Intraclass correlation was performed to calculate intraclass correlation coefficient (ICC) and Cronbach-alpha was calculated. Test-retest results were also analyzed using Bland-Altman plots. For the statistical analysis, SPSS 13.0 (SPSS Inc., Chicago, IL) was used. Significance level was set at P ≤ 0.05.

Results

Table 1 shows that CMJ without arm-swing results in significantly lower jump height for both women (P = 0.0020) and men (P = 0.00042) compared to CMJ with arm-swing. The mean difference between CMJ with arm swing and no arm swing was 14%. AJ results in significantly higher results than the CMJ for both women (P = 0.0014) and men (0.00029). The mean difference was 11 cm and the correlation between CMJ with arm swing and AJ was high (rs = 0.86, P < 0.01). Test-retest analysis is presented in Table 2. High and statistically significant intraclass correlation coefficients were found in all jumps, except for the AJ in the female group. However, as shown in Figure 1, no systematically changes between test occasions could be found.

Table 1
Table 1:
Reference values for test one (median and range) for CMJ with arm swing, CMJ without arm swing and AJ.
Table 2
Table 2:
ICCs (95% confidence interval) and Cronbach´s alpha for CMJ with arm swing, CMJ without arm swing, and AJ in men and women, separately, and the whole group.
Figure 1
Figure 1:
Bland-Altman plots for test-retest results regarding AJ, CMJ with and without arm swing. Lines indicate mean ± 2 SD.

The subjects had a moderate physical activity level (median 5, range 1-8). The relationship between physical activity from the activity registration form and jump height resulted in a nonsignificant correlation coefficient (rs = 0.24). A moderate correlation was observed when comparing CMJ with no arm swing and body fat % in women (rs = −0.57, P = 0.043). The participant having the highest jump also had a high body fat content and was a former elite handball player. When excluding her from the analysis, the correlation improved to rs = −0.76, P = 0.0045. A nonsignificant correlation appeared between CMJ with no arm swing compared to body fat % for men (rs = −0, 37, n.s.).

Discussion

The present study showed very good test-retest reliability in the CMJ both with and without free arm swing as well as for the AJ. The correlation was moderate/high between body composition and jump height for the women but low and non-significant for the men. The highest vertical jump height was registered performing the CMJ with free arm swing, which is in line with other studies (6). In the present study, it was found that the arm swing contributed with 14 % compared with the jump with no arm swing. This is slightly greater than what was found in Harman et al. (6), where they recorded a difference in height between 8% and 11% with arm swing.

Overall, the 2 measurement methods show good reliability, as do the 3 different jump methods in test-retest. As found in other studies, the present results showed greater jumping heights with the AJ method compared with the CMJ method. We believe that these 2 methods can be used and compared against each other if approximately 25% is subtracted from the AJ method results. In our study and in the study by Marcovic et al. (12), the jump results performed with the AJ showed an overall greater result compared with the CMJ. We compared the CMJ and the AJ with arm swing, and Markovic et al. compared the CMJ and the AJ without arm swing; both studies showed a greater result, 11 cm, for the AJ method.

One explanation for the higher jumping heights in the present study could be the difference in measuring methods. When measuring the CMJ, the participant stands on a contact mat that measures flight time and convert the measured value into centimeters. The measuring starts when the whole foot is in the air, which is when the toe leaves the mat. When measuring the AJ, the belt is fastened at the subject's waist and follows the body up in the air as soon as the subject starts elevating. This might lead to the discrepancy in measuring values. However, high correlations were found between jumping tests allowing comparisons of data in different studies if an approximation of 25% is made between tests. This study points out the importance of taking the measuring method into consideration when using reference values in clinical practice.

The relation between body fat content and ability to jump high has been shown to be strong in populations of athletes (16,18). This was also the case for the women in the current study, but not for the men, which suggests that other factors than body composition determines jumping height, as illustrated by the former handball player included in this study. She had the highest jump and the highest body fat content, and reasonably, her earlier career had a larger impact on her jumping height than her body composition.

Several participants who had a very low score on the 2 activity registration forms were the participants who jumped the highest. If we had used a physical activity form that covered more than the last month, maybe we would have registered a different result. The activity registration form only considered the physical activity for the last month. The participants were normally more active on their spare time than they had been during this last month. This resulted in a low score in the activity registration though they jumped high when performing the test-retest jumps. We therefore believe that former activity performed during the participants' whole life had a greater influence on the ability to jump high. Among the male participants we found that the subject who jumped the highest had been very active in different sports a couple of years ago and during a longer period, but is not physically active on the same level today.

Practical Applications

In conclusion, this study shows good reliability for both the CMJ and a moderate reliability for the AJ, especially in women. The 3 different jump methods used in the present study showed good test-retest reliability. The assessment tools can be compared if approximately 25% of the AJ value is subtracted.

References

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Keywords:

countermovement jump; body composition; fat mass; reliability

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