The aim of this study were the verification of criterion based familiarization by Intraclass  Correlation Coefficient (ICC) and Standard Error of Measurement (SEM) and the  identification of possible differences of performance and dynamic variables at squat  positions with 90o (SJ90  o) and 120o (SJ120  o) of knee angle. Fifteen male junior volleyball  players performed three randomly performed jumps with maximal intensity from each  squat position. SJ90  o results in lower peak force and higher vertical impulse, impulse  duration and time for peak force than SJ120  o. ICC and SEM show that familiarization that  consisted of three series of 5 jumps for each squat position with 1 minute of rest between  the jumps, is sufficient to ensure adequate test conditions

Araújo, Sílvia R. Santos

Lima, Júlia Sanna B.

Menzel, Hans-Joachim

Monteiro, Thamara

Peixoto, Gustavo Henrique

Pereira de Andrade, André Gustavo

English

ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive

33rd International Conference on Biomechanics in Sports, Poitiers, France, June 29 - July 3, 2015Floren Colloud, Mathieu Domalain & Tony Monnet (Editors)Injuries / Rehabilitation434RELIABILITY OF KINETIC VARIABLES OF SQUAT JUMPS WITH DIFFERENTSTARTING POSITIONS AFTER CRITERION BASED FAMILIARIZATIONHans-Joachim Menzel, Júlia Sanna B. Lima, Gustavo Henrique Peixoto, SílviaR. Santos Araújo, Thamara Monteiro and André Gustavo Pereira de AndradeFederal University of Minas Gerais, Belo Horizonte, BrazilThe aim of this study were the verification of criterion based familiarization by IntraclassCorrelation  Coefficient  (ICC)  and  Standard  Error  of  Measurement  (SEM)  and  theidentification  of  possible  differences  of  performance  and  dynamic  variables  at  squatpositions with 90o (SJ90o) and 120o (SJ120o) of knee angle. Fifteen male junior volleyballplayers  performed  three  randomly performed jumps with  maximal  intensity from eachsquat  position.  SJ90o results  in  lower  peak force and higher vertical impulse,  impulseduration and time for peak force than SJ120o. ICC and SEM show that familiarization thatconsisted of three series of 5 jumps for each squat position with 1 minute of rest betweenthe jumps, is sufficient to ensure adequate test conditions.KEY WORDS: criterion, familiarization, squat jump, starting positionINTRODUCTION:  For the assessment of jump performance different jump techniques likesquat jump (SJ), countermovement jump (CMJ) and drop jump (DJ) are applied. While CMJand DJ assess jump performance in more natural stretch-shortening-cycle muscle actions,squat jump allows testing leg explosiveness (force production) in primarily concentric muscleconditions  (Maulder  &  Cronin,  2005).  SJ  are  also  applied  to  investigate  differences  ofdynamic strategies for vertical jumps (Amasay, 2008) or to identify performance differencesbetween different sports (Ravn et al., 1999).  Furthermore,  vertical  jumps  on  a  force  platform  can  be  applied  to  determine  dynamicvariables for the identification of bilateral strength asymmetries of lower limbs (Impellizzeri etal., 2007, Newton et al., 2006). Despite the wide range of application of SJ as diagnostic tool,different squat positions are described in the literature. The knee angle of the initial squatposition is reported as self-selected (Amasay, 2008), 75o (Driss et al.,  2001), 90 o (Moran &Wallace, 2007), 100 o (Hasson et al., 2004), 110 o (Moran & Wallace, 2007) or 120 o (Gehri etal., 1998). Since the aims and methods of these studies were different, their results do notprovide consistent information about possible differences of dynamic variables between thedifferent squat positions. In order to verify the influence of squat depth on jump performanceDomire and Challis (2007) determined kinematic characteristics and the moments of  hip,knee and ankle between deep squat (knee flexion angle: 86.2±16.0o) and preferred squat(knee flexion angle: 105.3±10.3o). No significant differences between the deep and preferredsquat  position  could  be  found  concerning  jump  height,  and  normalized  maximal  jointmoments of hip,  knee and ankle, whereas the kinematic variables (elevation of center ofmass during impulse phase, time to maximum angle and initial angles of hip, knee and ankle)showed significant differences between the two investigated conditions. Since Domire andChallis  (2007) stated that  the influence of  squat depth on jump height  has not  yet  beensystematically examined, they investigated the effect of different squat positions on musclemodel parameters and joint angles of the lower limbs, but ground reaction forces were notanalyzed. Since SJ is a technique mostly used for diagnostic purposes and rarely practicedas  sports  specific  movement  technique,  familiarization  is  very  important  in  order  to  getconsistent  and  reliable  performance  and  diagnostic  results.  Bobbert  et  al.  (2008)  whoinvestigated  five different initial positions, where the  volunteers were familiarized  only withthe self-selected position, stated that the lack of familiarization might be the reason that nosignificant differences were found between SJ performance of the three lowest initial squatpositions. The analysis of the above mentioned studies show, that no specific informationcould be found about any criterion for sufficient familiarization.  In order to complement theknowledge about the influence of different squat positions and because of the importance ofground  reaction  forces  during  vertical  jumps  for  the  assessment  physical  condition33rd International Conference on Biomechanics in Sports, Poitiers, France, June 29 - July 3, 2015Floren Colloud, Mathieu Domalain & Tony Monnet (Editors)Injuries / Rehabilitation435(Wisløff et al.,  2004) and of bilateral strength differences of lower limbs (Impellizzeri  et al.,2007, Newton  et  al.,  2006),  the aims of  this study were the verification of  familiarizationbased  on  criterion  like  Intraclass  Correlation  Coefficient  (ICC)  and  Standard  Error  ofMeasurement  (SEM)  and  the  identification  of  possible  differences  of  performance  anddynamic variables at two different initial squat positions, 90o (SJ90o) and 120o (SJ120o) kneeangle.METHODS: Fifteen male volleyball players aged between 14 and 16 years (15.4 ± 0.6 years)with  no lower  limbs injury history participated  in  the  study.  The  study  consisted  of twosessions, with 24-hour interval between familiarization and data collection. The familiarizationconsisted of three series of 5 jumps for two squat positions (90° and 120° knee angle) with 1minute  of  rest  between  the jumps and three minutes between  the  series.  To avoid  anysequence  effect,  the jumps (SJ90o and SJ120o)  were  assigned randomly.  Prior  to  the  testprotocol athletes performed a 5 minutes preparatory activity, consisting of moderate intensityrunning and aerobic  exercises. The test  protocol consisted of  three randomly  performedjumps with maximal intensity from squat positions with  90° or 120° knee angle.  The initialposition was controlled by measuring the knee angle with a manual goniometer (Noraxon).The rest interval between trials was one minute. The vertical GRF were measured separatelyfor the right and left leg by two synchronized force platforms (PLA3-1D-7KN/JBAZb, Staniak,Poland),  operating  at 1000 Hz.  Data  acquisition  and  processing  were  performed withDasyLab 11 software. Familiarization was  determined  by  the  Intraclass  Correlation  Coefficient  (ICC3,1)  and  theStandard  Error  of  Measurement  of  the sample,  both  calculated by ANOVA for  repeatedmeasures analysis of variance. According to Weir (2005), the total error reflects systematicand random error (imprecision). That way, ICC is a measurement for the systematic error,which is represented in sport practice as the effect of motor learning. In the case of squatjump as diagnostic tool, motor learning should be concluded before the beginning of the testprocedure.  In  the present study,  the systematic error  of  the five SJ was assessed by arepeated measures analysis  of  variance (ANOVA).  The maximal  variation  of  the randomerror,  which represents the minimal  significant  difference of  measurements (MID),can becalculated as the SEM according to equation 1 (Weir, 2005).MID= SEM × 1.96x√2                                            (1)SEM = √mean square of error (MS error of ANOVA table)1.96 = z score associated with a 95% Confidence Interval Based on these criteria for systematic and random errors, the subjects were considered assufficiently familiarized if the result of ANOVA F-test were not significant  (Atkinson & Nevil,1998) and if the performance were within the limits of Mean ± MID (Claudino et al., 2012),which menas that every trial fell within these performance limits.Paired t-test was used to compare the jump height and kinetic variables between the twoinitial positions. The significance  level for  all  analyzes was p <0.05 and the  statisticalprogram used was SPSS 18.0.RESULTS: Table 1 shows the descriptive data and the results of paired t-test (*) for jumpheight,  impulse, impulse  duration,  time  to peak  force  and peak  force.  Statistical  resultsshowed that peak force was significantly higher for SJ120° than SJ90°  position and the time toreach peak  force was  lower  for  SJ120° position  than  SJ90°.  Impulse  and impulse durationshowed significantly higher means for SJ90° than for SJ120° position.The results of ICC with p-value of F-test and the SEM with  MID are shown in table 2 andconfirm the adequate and sufficient familiarization. The results confirm high reliability of theSJ  with  different  initial  squat  position  because  no  significant  difference  between  therepetitions could be identified.  This  means that  no further motor learning effect occurred33rd International Conference on Biomechanics in Sports, Poitiers, France, June 29 - July 3, 2015Floren Colloud, Mathieu Domalain & Tony Monnet (Editors)Injuries / Rehabilitation436during the experiment. Furthermore, the performance (jumping height) was within the limitsof Mean ± MID, that means within the range of acceptable random error.                                                            TABLE 1Descriptive statistics and results of paired t-test (*)I.P.  H (m) Impulse (N.s) Fmax (N) Δt (s) ΔtFmax (s)Mean SD Mean SD Mean SD Mean SD Mean SDSJ90° 0.30* 0.12 180.2* 27.91 793.7 127.45 0.42* 0.03 0.35* 0.03SJ120° 0.25 0.18 153.7 34.86 1279.6* 259.57 0.26 0.06 0.19 0.07I.P. – Initial position for squat jump; SD- Standard Deviation; SJ120° - SJ with 120° knee angle; SJ90° - SJ with 90° knee angle. H – Jump Height; Fmax – Peak Force;  Δt – Impulse duration; ΔtFmax – Time to Peak Force;  * significant differences between groups with p<0.05                                                                            TABLE 2Results of ICC, SEM and MID for jump heightICC p-value of F test SEM (m) MID (m) Mean ± MID (m)SJ90° 0.88 0.53 0.03 0.08 0.30 ± 0.08SJ120° 0.87 0.67 0.04 0.11 0.25 ± 0.11ICC - Intraclass Correlation Coefficient; SEM - Standard Error of Measurement;  MID - Minimal difference; SJ120° - SJ with 120° knee angle; SJ90° - SJ with 90° knee angle. DISCUSSION: Previous studies from Domire and Challis (2007) found no difference in jumpheight between 105.3º and 86.2º knee angle of initial squat position. However, Bobbert et al.(2008) investigated five positions (P1 = 124.39°, P2 =109.49° self-select = 95.73 °,  P4 =85.99°, P5 = 76.82°), and their results showed lower jump height at positions P1 and P2 thanat self-selected,  P4 and P5.  One explanation given by the authors was that  the lack offamiliarization with SJ could have affected these results.  The results of the present study,where  adequate  familiarization  was  verified  by  objective  criteria,  showed that  the  initialposition affects SJ performance, and that deeper squat position (SJ90°) leads to better jumpheight. The results corroborate those related by Kirby et al. (2011) that lower squat positionleads to lower peak reaction force and a longer period to achieve it. Quantitative verificationof  familiarization  by ICC with  p-value  of  F-test  and the Standard  Error  of  Measurementpermits the confirmation of concluded motor learning process and the estimation of randomerror that might be caused by different sources as motivation or varying test conditions (Weir,2005). Results of the present study show that a familiarization that consisted of three seriesof 5 jumps for each squat position with 1 minute of rest between the jumps and three minutesbetween  the  series,  is  sufficient  to  ensure  adequate  test  conditions  for  the  experimentperformed one day later. CONCLUSION: Squat Jump performance and kinetic variables of ground reaction forces arerelated to the initial squat position. Deeper initial squat position up to 90°of knee angle leadsto lower peak force and higher vertical impulse, impulse duration and time for  peak force.Especially the inverse relation of peak force and vertical impulse (performance) with differentsquat depths is important and should be considered, since some authors use vertical jumpsto analyze peak force (Impellizzeri et al., 2007, Newton et al., 2006), while others (Menzel etal.,  2013)  consider  the  impulse  as  criterion  for  the  analysis  of  bilateral  differences.Familiarization of squat jump and different initial squat positions is essential and should beverified by objective criteria like Minimal Significant Difference of Measurements (MID) andANOVA F-test.33rd International Conference on Biomechanics in Sports, Poitiers, France, June 29 - July 3, 2015Floren Colloud, Mathieu Domalain & Tony Monnet (Editors)Injuries / Rehabilitation437REFERENCES:Amasay, T. (2008). Static block jump techniques in volleyball: Upright versus squat starting positions.Journal of Strength & Conditioning Research, 22, 1242-1248.Atkinson, D.B. & Nevill, A.M. (1998). Statistical methods for assessing measurement error (reliability)in variables relevant to Sports Medicine. Sports Medicine. 26, 217–238.Bobbert, M., Casius, R., Sijpkens,I. & Jaspers, R. (2008). Humans adjust control to initial squat depthin vertical squat jumping. Journal of Applied Physiology, 105, 1428-1440.Claudino, J., Resende, B., Ribeiro, R., Ferreira, J., Couto, B. & Szmuchrowski, A. (2012). Pre verticaljump performance to regulate the training volume.  International  Journal  of  Sports Medicine,  33(2),101-107.Driss, T., Vandewalle, H., Quièvre, J., Miller, Ch. & Monod, H. (2001). Effects of external loading onpower output in a squat jump on a force platform: A comparison between strength and power athletesand sedentary individuals. Journal of Sports Sciences, 19(2), 99-105.Domire,  Z.J.  &  Challis,  J.H.  (2007).  The  influence  of  squat  depth  on  maximal  vertical  jumpperformance. Journal of Sports Sciences, 25, 193-200.Gehri, D., Ricard, M.D., Kleiner, D.M. & Kirkendall, D.T. (1998). A comparison of plyometric trainingtechniques  for  improving  vertical  jump  ability  and  energy  production.  Journal  of  Strength  andConditioning Research, 12(2), 85-89.Hasson, Ch.J., Dugan, E.L., Doyle, T.L.A., Humphries, B. & Newton, R.U. (2004). Neuromechanicalstrategies  employed  to  increase  jump  height  during  the  initiation  of  the  squat  jump.  Journal  ofElectromyography and Kinesiology, 14, 515-521.Impellizzeri, F.M., Rampinini, E., Maffiuletti, N. & Marcora, S.M. (2007). A vertical jump force test forassessing bilateral  strength asymmetry in  athletes.  Medicine & Science in  Sports  & Exercise,  39,2044-2050.Kirby,  T.,  McBride,  J.,  Haines,  T.  & Dayne,  A.  (2011).  Relative  Net  Vertical  Impulse  DeterminesJumping Performance. Journal of Applied Biomechanics, 27, 207-214.Maulder,  P.  &  Cronin,  J.  (2005).  Horizontal  and  vertical  jump  assessment:  reliability,  symmetry,discriminative and predictive ability. Physical Therapy in Sport, 6, 74-82.Menzel,  H.J.Chagas,  M.H.Szmuchrowski,  L.A.  Araújo,  S.R.S,  Andrade,  A.G.P  &  Jesus,  F.M.R.(2013).Analysis  of  lower  limb asymmetries  by  isokinetic  and  vertical  jump test  in  soccer  players.Journal of Strength and Conditioning Research, 27, 1370-1377.Moran,  K.A.  & Wallace,  E.S.  (2007).  Eccentric  loading  and range of  knee joint  motion effects  onperformance enhancement in vertical jumping. Human Movement Science, 26, 824-840.Newton, R.U., Gerber, A., Nimphius, S., Shin, J. Doan, B.K., Robertson, M., Pearson, D.R., Graig,B.W., Hakkinen, K. & Kraemer, W.J. (2006).  Determination of functional strength imbalance of thelower extremities. Journal of Strength & Conditioning Research, 20, 971-977.Ravn, S., Voigt,  M., Simonsen, E.B.,  Alkjær, T., Bojsen-Møller, F. & Klausen, K. (1999).  Choice ofjumping  strategy  in  two  standard  jumps,  squat  and  countermovement  jump  –  effect  of  trainingbackground or inherited preference?  Scandinavian Journal of Medicine and Science in Sports, 9, 201-208.Weir  S.  (2005)  Quantifying  test-retest  reliability  using  ICC and  the  SEM.  Journal  of   Strength  &Conditioning Research, 19, 231-240.Wisløff, U., Castagna, C., Helgerud, J., Jones, R. & Hoff, J. (2004) Strong correlation of maximal squatstrength with sprint  performance and vertical jump height in elite soccer players.  British Journal ofSports Medicine, 38, 285-288.

RELIABILITY OF KINETIC VARIABLES OF SQUAT JUMPS WITH DIFFERENT STARTING POSITIONS AFTER CRITERION BASED FAMILIARIZATION

https://ojs.ub.uni-konstanz.de/cpa/article/download/6419/5786

RELIABILITY OF KINETIC VARIABLES OF SQUAT JUMPS WITH DIFFERENT STARTING POSITIONS AFTER CRITERION BASED FAMILIARIZATION

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