Avoiding Systematic Errors in Isometric Squat-Related Studies without Pre-Familiarization by Using Sufficient Numbers of Trials

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There is no scientific evidence in the literature indicating that maximal isometric strength measures can be assessed within 3 trials. We questioned whether the results of isometric squat-related studies in which maximal isometric squat strength (MISS) testing was performed using limited numbers of trials without pre-familiarization might have included systematic errors, especially those resulting from acute learning effects. Forty resistance-trained male participants performed 8 isometric squat trials without pre-familiarization. The highest measures in the first “n” trials (3 ≤ n ≤ 8) of these 8 squats were regarded as MISS obtained using 6 different MISS test methods featuring different numbers of trials (The Best of n Trials Method [BnT]). When B3T and B8T were paired with other methods, high reliability was found between the paired methods in terms of intraclass correlation coefficients (0.93-0.98) and coefficients of variation (3.4-7.0%). The Wilcoxon’s signed rank test indicated that MISS obtained using B3T and B8T were lower (p < 0.001) and higher (p < 0.001), respectively, than those obtained using other methods. The Bland- Altman method revealed a lack of agreement between any of the paired methods. Simulation studies illustrated that increasing the number of trials to 9-10 using a relatively large sample size (i.e., ≥ 24) could be an effective means of obtaining the actual MISS values of the participants. The common use of a limited number of trials in MISS tests without pre-familiarization appears to have no solid scientific base. Our findings suggest that the number of trials should be increased in commonly used MISS tests to avoid learning effect-related systematic errors

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  • Abernethy P Wilson G Logan P. Strength and power assessment. Issues controversies and challenges. Sports Med 1995; 19(6): 401-417

  • Alegre LM Jimenez F Gonzalo-Orden JM Martin-Acero R Aguado X. Effects of dynamic resistance training on fascicle length and isometric strength. J Sports Sci 2006; 24(5): 501-508

  • Atkinson G Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine. Sports Med 1998; 26(4): 217-238

  • Balshaw TG Hunter AM. Evaluation of electromyography normalisation methods for the back squat. J Electromyogr Kines 2012; 22(2): 308-319

  • Bland JM Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res 1999; 8(2): 135-160

  • Blazevich AW Cannavan D. Strength Testing. In E. M. Winter (Ed.) Sport and exercise physiology testing guidelines: The British Association of Sport and Exercise Sciences Guide - Volume II: Exercise and clinical testing (1st ed.). New York NY: Routledge 130-137; 2006

  • Brown LE Weir JP. ASEP procedures recommendation I: Accurate assessment of muscular strength and power. J Exerc Physiol 2001; 4(3): 1-21

  • Cormie P Deane RS Triplett NT McBride JM. Acute effects of whole-body vibration on muscle activity strength and power. J Strength Cond Res 2006; 20(2): 257-261

  • Demura S Miyaguchi K Shin S Uchida Y. Effectiveness of the 1RM estimation method based on isometric squat using a back-dynamometer. J Strength Cond Res 2010; 24(10): 2742-2748

  • Dumke CL Pfaffenroth CM McBride JM McCauley GO. Relationship between muscle strength power and stiffness and running economy in trained male runners. Int J Sports Physiol Perform 2010; 5(2): 249-261

  • Gabriel DA Kamen G Frost G. Neural adaptations to resistive exercise: mechanisms and recommendations for training practices. Sports Med 2006; 36(2): 133-149

  • Gallagher S Moore JM Stobbe TJ. Isometric Isoinertial and Psychophysical Strength Testing: Devices and Protocols. In S. Kumar (Ed.) Muscle strength. Boca Raton: CRC Press 129-156; 2004

  • Gallagher S Moore JS Stobbe TJ. Physical strength assessment in ergonomics. Fairfax Va.: American Industrial Hygiene Association 1-64; 1998

  • Green LA Parro JJ Gabriel DA. Quantifying the familiarization period for maximal resistive exercise. Appl Physiol Nutr Metab 2014; 39: 1-7

  • Herda TJ Cramer JT Ryan ED McHugh MP Stout JR. Acute effects of static versus dynamic stretching on isometric peak torque electromyography and mechanomyography of the biceps femoris muscle. J Strength Cond Res 2008; 22(3): 809-817

  • Hopkins WG. Measures of reliability in sports medicine and science. Sports Med 2000; 30(1): 1-15

  • Hopkins WG Schabort EJ Hawley JA. Reliability of power in physical performance tests. Sports Med 2001; 31(3): 211-234

  • Kline RB. Beyond significance testing: Reforming data analysis methods in behavioral research. Washington DC American Psychological Association 58; 2004

  • Krishnan C Allen EJ Williams GN. Torque-based triggering improves stimulus timing precision in activation tests. Muscle Nerve 2009; 40(1): 130-133

  • Kroemer KH. Assessment of human muscle strength for engineering purposes: a review of the basics. Ergonomics 1999; 42(1): 74-93

  • Kunz R Oxman AD. The unpredictability paradox: review of empirical comparisons of randomised and non-randomised clinical trials. Brit Med J 1998; 317(7167): 1185-1190

  • Markovic G Jaric S. Movement performance and body size: the relationship for different groups of tests. Eur J Appl Physiol 2004; 92(1-2): 139-149

  • Markovic G Jaric S. Is vertical jump height a body size-independent measure of muscle power? J Sport Sci 2007; 25(12): 1355-1363

  • McBride JM Cormie P Deane R. Isometric squat force output and muscle activity in stable and unstable conditions. J Strength Cond Res 2006; 20(4): 915-918

  • McBride JM Deane R Nimphius S. Effect of stretching on agonist-antagonist muscle activity and muscle force output during single and multiple joint isometric contractions. Scand J Med Sci Sports 2007; 17(1): 54-60

  • Morrow JR Jackson AW. How significant is your reliability. Res Q Exercise Sport 1993; 64(3): 352-355

  • Newton RU Hakkinen K Hakkinen A McCormick M Volek J Kraemer WJ. Mixed-methods resistance training increases power and strength of young and older men. Med Sci Sports Exerc 2002; 34(8): 1367-1375

  • Nuzzo JL McBride JM Cormie P McCaulley GO. Relationship between countermovement jump performance and multijoint isometric and dynamic tests of strength. J Strength Cond Res 2008; 22(3): 699-707

  • Rahmani A Viale F Dalleau G Lacour JR. Force/velocity and power/velocity relationships in squat exercise. Eur J Appl Physiol 2001; 84(3): 227-232

  • Tillin NA Bishop D. Factors modulating post-activation potentiation and its effect on performance of subsequent explosive activities. Sports Med 2009; 39(2): 147-166

  • Verdera F Champavier L Schmidt C Bermon S Marconnet P. Reliability and validity of a new device to measure isometric strength in polyarticular exercises. J Sport Med Phys Fit 1999; 39(2): 113-119

  • Wallerstein LF Barroso R Tricoli V Mello MT Ugrinowitsch C. The influence of familiarization sessions on the stability of ramp and ballistic isometric torque in older adults. J Aging Phys Act 2010; 18(4): 390-400

  • Watanabe K Akima H. Normalized EMG to normalized torque relationship of vastus intermedius muscle during isometric knee extension. Eur J Appl Physiol 2009; 106(5): 665-673

  • Weir JP. Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res 2005; 19(1): 231-240

  • Whitley JDElliott. Learning component in repetitive maximal static contractions. Percept Motor Skill 1968; 27: 1195-1200

  • Wilson G. Assessment of muscle function by isometric tests. In V. R. Preedy and T. J. Peters (Eds.) Skeletal muscle: Pathology diagnosis and management of disease. London: Greenwich Medical Media 443; 2002

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