Validating Two Systems for Estimating Force and Power

Abstract

This study examined the validity of 2 kinematic systems for estimating force and power during squat jumps. 12 weight-trained males each performed single repetition squat jumps with a 20-kg, 40-kg, 60-kg and 80-kg load on a Kistler portable force plate. A commercial linear position transducer (Gymaware [GYM]) and accelerometer (Myotest^® [MYO]) were attached to the bar to assess concentric peak force (PF) and peak power (PP). Across all loads tested, the GYM and MYO estimates of PF and PP were moderately to strongly correlated (P≤0.05–0.001) with the force plate measurements (r=0.59–0.87 and r=0.66–0.97), respectively. The mean PF and PP values were not significantly different between the 2 kinematic systems and the force plate, but the estimates did produce some systematic bias and relatively large random errors, especially with the 20-kg load (PF bias >170 N, PF error >335 N, PP bias >400 W, PP error >878 W). Some proportional bias was also identified. In summary, the estimation of PF and PP by a linear position transducer and accelerometer showed moderate to strong relative validity and equivalent absolute validity, but these estimates are limited by the presence of bias and large random errors.

Key words

force plate - kinetic - kinematic - acceleration

References

• 1 Atkinson G, Davison RCR, Nevill AM. Performance characteristics of gas analysis systems: what we know and what we need to know.  Int J Sports Med. 2005;  26 S2-S10
• 2 Atkinson G, Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine.  Sports Med. 1998;  26 217-238
• 3 Bland MJ, Altman DG. Applying the right statistics: analyses of measurement studies.  Ultrasound Obstet Gynecol. 2003;  22 85-93
• 4 Casartelli N, Muller R, Maffiuletti NA. Validity and reliability of the Myotest accelerometric system for the assessment of vertical jump height.  J Strength Cond Res. 2010;  24 3186-3193
• 5 Cormie P, Deane R, McBride JM. Methodological concerns for determining power output in the jump squat.  J Strength Cond Res. 2007;  21 424-430
• 6 Cormie P, McBride JM, McCaulley GO. Validation of power measurement techniques in dynamic lower body resistance exercises.  J Appl Biomech. 2007;  23 103-118
• 7 Crewther B, Cronin J, Keogh J. Possible stimuli for strength and power adaptation: acute mechanical responses.  Sports Med. 2005;  35 967-989
• 8 Cronin JB, Hing RD, McNair PJ. Reliability and validity of a linear position transducer for measuring jump performance.  J Strength Cond Res. 2004;  18 590-593
• 9 Drinkwater EJ, Galna B, McKenna MJ, Hunt PH, Pyne DB. Validation of an optical encoder during free weight resistance movements and analysis of bench press sticking point power during fatigue.  J Strength Cond Res. 2007;  21 510-517
• 10 Dugan EL, Doyle TLA, Humphries B, Hasson CJ, Newton RU. Determining the optimal load for jump squats: A review of methods and calculations.  J Strength Cond Res. 2004;  18 668-674
• 11 Gard SA, Miff SC, Kuo AD. Comparison of kinematic and kinetic methods for computing the vertical motion of the body center of mass during walking.  Hum Mov Sci. 2004;  22 597-610
• 12 Harriss DJ, Atkinson G. International Journal of Sports Medicine – Ethical Standards in Sport and Exercise Science Research.  Int J Sports Med. 2009;  30 701-702
• 13 Hatze H. Validity and reliability of methods for testing vertical jumping performance.  J Appl Biomech. 1998;  14 127-140
• 14 Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science.  Med Sci Sports Exerc. 2009;  41 3-12
• 15 Hori N, Newton RU, Andrews WA, Kawamori N, McGuigan MR, Nosaka K. Comparison of four different methods to measure power output during the hang power clean and the weighted jump squat.  J Strength Cond Res. 2007;  21 314-320
• 16 Jidovtseff B, Crielaard JM, Cauchy S, Croisier JL. Validity and reliability of an inertial dynamometer using accelerometry.  Sci Sport. 2008;  23 94-97
• 17 Li L, Olson MW, Winchester JB. A proposed method for determining peak power in the jump squat exercise.  J Strength Cond Res. 2008;  22 326-331
• 18 Ludbrook J. Statistical techniques for comparing measures and methods of measurement: A critical review.  Clin Exp Pharmacol Physiol. 2002;  29 527-536
• 19 Nevill AM, Atkinson G. Assessing agreement between measurements recorded on a ratio scale in sports medicine and sports science.  Br J Sport Med. 1997;  31 314-318
• 20 Thompson CJ, Bemben MG. Reliability and comparability of the accelerometer as a measure of muscular power.  Med Sci Sports Exerc. 1999;  31 897-902
• 21 Vanrenterghem J, De Clercq D, Van Cleven P. Necessary precautions in measuring correct vertical jumping height by means of force plate measurements.  Ergonomics. 2001;  44 814-818
• 22 Walsh M, Ford KR, Bangen KJ, Myer GD, Hewett TE. The validation of a portable force plate for measuring force-time data during jumping and landing tasks.  J Strength Cond Res. 2006;  20 730-734
• 23 Wood GA. Data smoothing and differentiation procedures in biomechanics.  Exerc Sport Sci Rev. 1982;  10 308-362

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