Reliability and factorial validity of squat and countermovement jump tests.
01 Aug 2004-Journal of Strength and Conditioning Research (J Strength Cond Res)-Vol. 18, Iss: 3, pp 551-555
TL;DR: It can be concluded that CMJ and SJ, measured by means of contact mat and digital timer, are the most reliable and valid field tests for the estimation of explosive power of the lower limbs in physically active men.
Abstract: The primary aim of this study was to determine reliability and factorial validity of squat (SJ) and countermovement jump (CMJ) tests. The secondary aim was to compare 3 popular methods for the estimation of vertical jumping height. Physical education students (n = 93) performed 7 explosive power tests: 5 different vertical jumps (Sargent jump, Abalakow's jump with arm swing and without arm swing, SJ, and CMJ) and 2 horizontal jumps (standing long jump and standing triple jump). The greatest reliability among all jumping tests (Cronbach's alpha = 0.97 and 0.98) had SJ and CMJ. The reliability alpha coefficients for other jumps were also high and varied between 0.93 and 0.96. Within-subject variation (CV) in jumping tests ranged between 2.4 and 4.6%, the values being lowest in both horizontal jumps and CMJ. Factor analysis resulted in the extraction of only 1 significant principal component, which explained 66.43% of the variance of all 7 jumping tests. Since all jumping tests had high correlation coefficients with the principal component (r = 0.76-0.87), it was interpreted as the explosive power factor. The CMJ test showed the highest relationship with the explosive power factor (r = 0.87), that is, the greatest factorial validity. Other jumping tests had lower but relatively homogeneous correlation with the explosive power factor extracted. Based on the results of this study, it can be concluded that CMJ and SJ, measured by means of contact mat and digital timer, are the most reliable and valid field tests for the estimation of explosive power of the lower limbs in physically active men.
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TL;DR: Variables derived from the CMJ5 may respond differently than their CMJ1 counterparts and should provide insights into differential mechanisms of response and adaptation and the impact of both acute and chronic training and competition.
Abstract: Purpose: To establish the reliability of various measures obtained during single and repeated countermovement jump (CMJ) performance in an elite athlete population. Methods: Two studies, each involving 15 elite Australian Rules Football (ARF) players were conducted where subjects performed two days, separated by one week, of AM and PM trials of either a single (CMJ1) or 5 repeated CMJ (CMJ5). Each trial was conducted on a portable force-plate. The intraday, interday, and overall typical error (TE) and coefficient of variation (CV%) were calculated for numerous variables in each jump type. Results: A number of CMJ1 and CMJ5 variables displayed high intraday, interday, and overall reliability. In the CMJ1 condition, mean force (CV 1.08%) was the most reliable variable. In the CMJ5, flight time and relative mean force displayed the highest repeatability with CV of 1.88% and 1.57% respectively. CMJ1Mean force was the only variable with an overall TE < smallest worthwhile change (SWC). Conclusion: Selected variables obtained during CMJ1 and CMJ5 performance can be used to assess the impact of both acute and chronic training and competition. Variables derived from the CMJ5 may respond differently than their CMJ1 counterparts and should provide insights into differential mechanisms of response and adaptation.
495 citations
Cites methods or result from "Reliability and factorial validity ..."
...Based on the influence of arm swing on CMJ performance, previous research has also used this technique.(1,2,9,11,24) In the CMJ1, subjects were instructed to jump as high as possible, while in the CMJ5, subjects were required to jump as high as possible for 5 consecutive efforts without a pause between jumps....
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...8% have been reported when Height is measured using a timing mat.(11,18) These results are similar to those of the current study despite the different measurement apparatus used....
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TL;DR: The results of this study indicate that linear sprinting, agility, and vertical jumping are independent locomotor skills and suggest a variety of tests ought to be included in an assessment protocol for high school and college female athletes.
Abstract: The aim of this study was to assess the relationships between various field tests in female athletes. Altogether, 83 high school soccer, 51 college soccer, and 79 college lacrosse athletes completed tests for linear sprinting, countermovement jump, and agility in a single session. Linear sprints (9.1, 18.3, 27.4, and 36.6 m) and agility tests (Illinois and pro-agility) were evaluated using infrared timing gates, while countermovement jump height was assessed using an electronic timing mat. Pearson's product – moment correlation coefficients (r) were used to determine the strength and directionality of the relationship between tests and coefficients of determination (r 2) were used to examine the amount of explained variance between tests. All of the performance scores were statistically correlated with each other; however, the coefficients of determination were low, moderate, and high depending on the test pairing. Linear sprint split times were strongly correlated with each other (r = 0.775 to 0...
314 citations
Cites background from "Reliability and factorial validity ..."
...Although jumping is not extremely common in soccer (Bangsbo, 1994 ) and probably occurs with less frequency in lacrosse, the countermovement jump is typically used as an indirect indicator of lower body power (Canavan & Vescovi, 2004 ; Markovic, Dizdar, Jukic, & Cardinale, 2004 )....
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TL;DR: It is concluded that short-term sprint training produces similar or even greater training effects in muscle function and athletic performance than does conventional plyometric training.
Abstract: The purpose of this study was to evaluate the effects of sprint training on muscle function and dynamic athletic performance and to compare them with the training effects induced by standard plyometric training. Male physical education students were assigned randomly to 1 of 3 groups: sprint group (SG; n = 30), plyometric group (PG; n = 30), or control group (CG; n = 33). Maximal isometric squat strength, squat- and countermovement jump (SJ and CMJ) height and power, drop jump performance from 30-cm height, and 3 athletic performance tests (standing long jump, 20-m sprint, and 20-yard shuttle run) were measured prior to and after 10 weeks of training. Both experimental groups trained 3 days a week; SG performed maximal sprints over distances of 10-50 m, whereas PG performed bounce-type hurdle jumps and drop jumps. Participants in the CG group maintained their daily physical activities for the duration of the study. Both SG and PG significantly improved drop jump performance (15.6 and 14.2%), SJ and CMJ height ( approximately 10 and 6%), and standing long jump distance (3.2 and 2.8%), whereas the respective effect sizes (ES) were moderate to high and ranged between 0.4 and 1.1. In addition, SG also improved isometric squat strength (10%; ES = 0.4) and SJ and CMJ power (4%; ES = 0.4, and 7%; ES = 0.4), as well as sprint (3.1%; ES = 0.9) and agility (4.3%; ES = 1.1) performance. We conclude that short-term sprint training produces similar or even greater training effects in muscle function and athletic performance than does conventional plyometric training. This study provides support for the use of sprint training as an applicable training method of improving explosive performance of athletes in general.
304 citations
Cites methods from "Reliability and factorial validity ..."
...Subjects performed SLJ on a long jump mat (Elan, Slovenia), and the distance from the starting point to the landing point at heel contact was used as the result....
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...Both SG and PG groups significantly (p 0.001) improved SLJ (3.2%; ES 0.5 vs. 2.8%; ES 0.4), and these improvements were significantly (p 0.001) higher compared with CG (Figure 4a)....
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...Three tests previously used to measure jumping (18), sprinting (19), and agility performance (23, 24) were used for the assessment of athletic performance....
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...Horizontal jump performance was assessed using a long jump from a standing position with arm swing (SLJ) (18)....
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...Although both vertical and horizontal jumps are usually considered as explosive power tests, we decided to include SLJ in analysis as an athletic performance test....
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TL;DR: The SLJ test is practical, time efficient, and low in cost and equipment requirements and might be considered a general index of muscular fitness in youth.
Abstract: The purpose of the present study was to examine the association among different measures of lower body muscular strength in children, and the association between measures of lower- and upper-body muscular strength. The study population comprises 94 (45 girls) healthy Caucasian children aged 6-17 years. Children performed several lower body explosive muscular strength tests (i.e., standing long jump [SLJ], vertical jump, squat jump, and countermovement jump) and upper body muscular strength tests (i.e., throw basketball, push-ups, and isometric strength exercises). The association among the study tests was analyzed by multiple regression. The SLJ was strongly associated with other lower body muscular strength tests (R = 0.829-0.864), and with upper body muscular strength tests (R = 0.694-0.851). The SLJ test might be therefore considered a general index of muscular fitness in youth. The SLJ test is practical, time efficient, and low in cost and equipment requirements.
293 citations
TL;DR: The results of the present study showed that CMJ height can be easily, accurately and reliably evaluated using a specially developed iPhone 5 s app.
Abstract: The purpose of this investigation was to analyse the concurrent validity and reliability of an iPhone app (called: My Jump) for measuring vertical jump performance. Twenty recreationally active healthy men (age: 22.1 ± 3.6 years) completed five maximal countermovement jumps, which were evaluated using a force platform (time in the air method) and a specially designed iPhone app. My jump was developed to calculate the jump height from flight time using the high-speed video recording facility on the iPhone 5 s. Jump heights of the 100 jumps measured, for both devices, were compared using the intraclass correlation coefficient, Pearson product moment correlation coefficient (r), Cronbach’s alpha (α), coefficient of variation and Bland–Altman plots. There was almost perfect agreement between the force platform and My Jump for the countermovement jump height (intraclass correlation coefficient = 0.997, P < 0.001; Bland–Altman bias = 1.1 ± 0.5 cm, P < 0.001). In comparison with the force platform, My Ju...
286 citations
References
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TL;DR: A wider understanding of reliability and adoption of the typical error as the standard measure of reliability would improve the assessment of tests and equipment in the authors' disciplines.
Abstract: Reliability refers to the reproducibility of values of a test, assay or other measurement in repeated trials on the same individuals. Better reliability implies better precision of single measurements and better tracking of changes in measurements in research or practical settings. The main measures of reliability are within-subject random variation, systematic change in the mean, and retest correlation. A simple, adaptable form of within-subject variation is the typical (standard) error of measurement: the standard deviation of an individual’s repeated measurements. For many measurements in sports medicine and science, the typical error is best expressed as a coefficient of variation (percentage of the mean). A biased, more limited form of within-subject variation is the limits of agreement: the 95% likely range of change of an individual’s measurements between 2 trials. Systematic changes in the mean of a measure between consecutive trials represent such effects as learning, motivation or fatigue; these changes need to be eliminated from estimates of within-subject variation. Retest correlation is difficult to interpret, mainly because its value is sensitive to the heterogeneity of the sample of participants. Uses of reliability include decision-making when monitoring individuals, comparison of tests or equipment, estimation of sample size in experiments and estimation of the magnitude of individual differences in the response to a treatment. Reasonable precision for estimates of reliability requires approximately 50 study participants and at least 3 trials. Studies aimed at assessing variation in reliability between tests or equipment require complex designs and analyses that researchers seldom perform correctly. A wider understanding of reliability and adoption of the typical error as the standard measure of reliability would improve the assessment of tests and equipment in our disciplines. CURRENT OPINION
4,149 citations
"Reliability and factorial validity ..." refers background or methods in this paper
...Within-subject variation for all tests was determined by calculating coefficient of variation (CV) as outlined by Hopkins (9)....
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...According to Hopkins (9), reasonable precision for estimates of reliability requires approximately 50 study participants and at least 3 trials....
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Journal Article•
TL;DR: The results suggest that although the leg extensor muscles of the men subjects could sustain much higher stretch loads, the females may be able to utilize a greater portion of the stored elastic energy in jumping activities.
Abstract: An alternating cycle of eccentric-concentric contractions in locomotion represents a sequence when storage and utilization of elastic energy takes place. It is possible that this storage capacity and its utilization depends on the imposed stretch loads in activated muscles, and that sex differences may be present in these phenomena. To investigate these assumed differences, subjects from both sexes and of good physical condition performed vertical jumps on the force-platform from the following experimental conditions: squatting jump (SJ) from a static starting position; counter-movement jump (CMJ) from a free standing position and with a preparatory counter-movement; drop jumps (DJ) from the various heights (20 to 100 cm) on to the platform followed immediately by a vertical jump. In all subjects the SJ, in which condition no appreciable storage of elastic energy takes place, produced the lowest height of rise of the whole body center of gravity (C.G.). The stretch load (drop height) influenced the performance so that height of rise of C. of G. increased when the drop height increased from 26 up to 62 cm (males) and from 20 to 50 cm (females). In all jumping conditions the men jumped higher than the women. However, examination of the utilization of elastic energy indicated that in CMJ the female subjects were able to utilize most (congruent to 90%) of the energy produced in the prestretching phase. Similarly, in DJ the overall change in positive energy over SJ condition was higher in women as compared to men. Thus the results suggest that although the leg extensor muscles of the men subjects could sustain much higher stretch loads, the females may be able to utilize a greater portion of the stored elastic energy in jumping activities.
829 citations
"Reliability and factorial validity ..." refers background in this paper
...However, during the past 20 years, 2 laboratory vertical jump tests gained a lot of attention because of the possibility of discriminate leg contribution and the effect of prestretch: the squat jump (SJ) and the countermovement jump (CMJ) (16) measured by means of contact mats or force plates....
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...In particular, vertical jumping tests performed on contact mats are highly considered in the coaching community because flight time–based measurements have been reported to produce a very small error of measurement when compared with video analysis (16)....
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TL;DR: The experimental group which trained with the load that maximized mechanical power achieved the best overall results in enhancing dynamic athletic performance recording statistically significant (P < 0.05) improvements on most test items and producing statistically superior results to the two other training modalities on the jumping and isokinetic tests.
Abstract: This study was performed to determine which of three theoretically optimal resistance training modalities resulted in the greatest enhancement in the performance of a series of dynamic athletic activities. The three training modalities included 1) traditional weight training, 2) plyometric training, and 3) explosive weight training at the load that maximized mechanical power output. Sixty-four previously trained subjects were randomly allocated to four groups that included the above three training modalities and a control group. The experimental groups trained for 10 wk performing either heavy squat lifts, depth jumps, or weighted squat jumps. All subjects were tested prior to training, after 5 wk of training and at the completion of the training period. The test items included 1) 30-m sprint, 2) vertical jumps performed with and without a countermovement, 3) maximal cycle test, 4) isokinetic leg extension test, and 5) a maximal isometric test. The experimental group which trained with the load that maximized mechanical power achieved the best overall results in enhancing dynamic athletic performance recording statistically significant (P < 0.05) improvements on most test items and producing statistically superior results to the two other training modalities on the jumping and isokinetic tests.
772 citations
TL;DR: It is suggested that the elastic energy is stored in the active muscles, and it is demonstrated that the muscles of the legs are activated in the downward jumps before contact with the platform is established.
Abstract: ASMUSSEN, E. and F. BONDE-PETERSEN. Storage of elastic energy in skeletal muscles in man. Acta physiol. scand. 1974. 91. 385-392 The question, if muscles can absorb and temporarily store mechanical energy in the form of elastic energy for later re-use, was studied by having subjects perform maximal verticaljumps on a registering force-platform. The jumps were performed 1) from a semi-squatting position, 2) after a natural counter-movement from a standing position, or 3) in continuation of jumps down from heights of 0.23, 0.40, or 0.69 m. The heights of the jumps were calculated from the registered flight times. The maximum energy level, Eneg, of the jumpers prior to the upward movement in the jump, was considered to be zero in condition 1. In condition 2 it was calculated from the force-time record ofthe force-platform; and in condition 3 it was calculated from the height of the downward jump and the weight of the subject. The maximum energy level after take-off, E,,,, was calculated from the height of the jump and the jumper’s weight. It was found that theheight of the jump and Epns increased with increasing amounts of Eneg, up to a certain level (jumping down from 0.40 m). The gains in Epos over t$at in condition 1, were expressed as a percentage of Eneg and found to be 22.9 % in condition 2, and 13.2, 10.5, and 3.3 % in the three situations ofcondition 3. It is suggested that the elastic energy is stored in the active muscles, and it is demonstrated that the muscles of the legs are activated in the downward jumps before contact with the platform is established. The elastic properties of muscles have been known and studied extensively for many years. The original concept of e.g. Levin and Wyman (1927), viz. that the energy liberated at contraction was immediately stored as elastic energy in the series elastic components for subsequent use in performing work, has been abandoned, not least after the discovery of the “Fenn effect” (Fenn and Marsh 1935). Nevertheless muscle elasticity has continued to arouse the interest of muscle physiologists, and its possible role as a buffer and temporary store of mechanical energy has anew been brought to the attention of work physiologists e.g. by the studies of Cavagna et al. (1968). One way of investigating this possible function of the elastic component in muscle is to compare the release of external mechanical energy without and with a previous stretching of the involved muscles. This was done by Marey and Demeny (1885) who compared the heights of vertical jumps performed without and with a preliminary counter-movement and found the height to be higher in the latter case. Recently Cavagna et al. (1971) repeated these experiments, using a force-platform
470 citations
"Reliability and factorial validity ..." refers background in this paper
...Determination of jumping height in CMJ is based on the flight time (2), where the flight-time measurement starts at the time an athlete leaves the ground....
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424 citations