Validity of the Myotest® during the bench press

Validity of the Myotest® during the bench press:Preliminary resultsJidovtseff BorisPhysical Fitness Evaluation and Training Service – University of Liège – BelgiumIntroductionIn order to explore validity, we compared the measurements provided by the Myotest® withmeasurements from another recognized isoinertial dynamometer (Jidovtseff et al., 2006) obtainedfrom a dynamic bench press test. Analysis of the results was carried out in two parts – on the onehand the correlations that occur between the results recorded by each measuring system are evaluated,and on the other hand the Myotest®’s ability to detect minor performance modifications betweenattempts using different weights was investigated.Experimental procedure14 subjects (5 girls and 9 boys), all of whom study physical education and exhibit no injuries to thelower limbs, took part in the bench press isoinertial evaluation procedure.Following a brief familiarization session to determine 1RM, the subjects carried out the same teststhree times within the space of one week. The weights used, the number of attempts and the recoverytime permitted are listed in table 1.Familiarization Session tests 1 – 2 – 3• Determination of the positionWeights (% 1RM) Method Attempt Recovery30% Concentric 4 1’• Familiarization30% With4 1’projection• Determination of 1RM 50% Concentric 3 1’70% Concentric 2 3’95% Concentric 2 3’Table 1 – Experimental procedureIn all of the tests, the performances were measured using the Myotest® and the isoinertialdynamometer developed at the University of Liège (ULg) by combining an accelerometer and adisplacement sensor. The parameters used in our analysis are as follows:• Time : Total time to lift the bar• Dmax : Maximum bar displacement• Pmax : Maximum power during the bench press• Pave : Average power during the entire lifting phase of the bar• Vmax : Maximum bar velocity• Vave : Average velocity during the entire lifting phase of the barPreliminary resultsThe preliminary results involve 152 tests collected from 7 of the 14 subjects.Initially, we studied the correlations that exist between the parameters measured by the twodynamometers (Myotest® and Ulg) during the same test.The time taken to lift the bar is perfectly correlated by the two dynamometers (r = 0.997). Thecorrelations were very high for Pmax, Vmax and Vave (0.955

The measurements observed for the first three loads (30, 50 and 70% of 1RM) appear to be in astraight line. All of the measurements carried out to 95% demonstrate a linear decline that isdetermined by the weights.Myotest3000Time2500200015001000y = 1,1014x - 12,302500R 2 = 0,9934ULg00 500 1000 1500 2000 2500 3000Myotest100908070605040Displacement302010y = 1,6194x - 41,986R 2 = 0,7468ULg00 20 40 60 80 100Myotest1000900800700600500400300200Pmaxy = 1,1285x - 122,01R 2 = 0,9154100ULg00 200 400 600 800 1000MyotestPave400350300250200150100y = 1,3088x - 122,650R 2 = 0,8835ULg00 50 100 150 200 250 300 350 400Myotest3VmaxMyotest1,6Vave2,51,421,211,50,81y = 1,0412x - 0,14610,5R 2 = 0,9882ULg00 0,5 1 1,5 2 2,5 30,60,40,2y = 1,0446x - 0,1482R 2 = 0,9884ULg00 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6Figure 1 – Correlations between the measurements observed by the two dynamometers for the mainparameters.Equally interesting is a comparison of the measurements of each dynamometer when a subject carriesout the bench press test.(m.s -2 )1,6Vave(m.s -2 )3Vmax1,42,51,2120,81,50,60,40,20ULgMytest(%1RM)30 30 30 30 30 30 30 30 50 50 50 70 70 95 9510,50ULgMytest(%1RM)30 30 30 30 30 30 30 30 50 50 50 70 70 95 95

(watts)400Pave(watts)900Pmax350300250200150100500ULgMytest(%1RM)30 30 30 30 30 30 30 30 50 50 50 70 70 95 958007006005004003002001000ULgMytest(%1RM)30 30 30 30 30 30 30 30 50 50 50 70 70 95 95Figure 2 – Performances measured by the dynamometers with a subject lifting different weights during asingle session.Clear parallels between the power (Pave and Pmax) and velocity (Vave and Vmax) measurements canbe observed among the results received from the two dynamometers.The average values provided by Myotest® appear to be slightly lower. At 95% of 1RM on the otherhand, the results provided by the two measuring systems prove to be very different.Interpretations and conclusionsThis collection of preliminary results shows that the Myotest® provides valid values during the firstthree loads (30, 50 and 70% of 1RM). The parallel observed by the ULg dynamometer alsodemonstrates that it is highly sensitive to minor variations in performance. This sensitivity remains abasic useful quality when trying to track the long-term effects and results of training. However, at 95%of 1Rm, the Myotest® appears to have reached the limits of its validity: The results no longer entirelymatch those obtained with the ULg dynamometer.At this load, it is probably the case that the movement,being very slow and very long, is plaguedby a parasitic signal that favors an accumulationof errors, and thus has a direct chain-reactioneffect on the velocity and power measurements.The error could stem from the procedure used tocalculate the two scales. We were in fact able tocorrect most of the data drift by going back to theaccelerometer’s original signal. Within the scopeof this type of procedure, this observation leadsus to believe that an improvement in the dataanalysis process would increase the validity ofthe Myotest® measurements across all loads.(m.s -2 )VmaxReferenceJidovtseff et al. – The concept of iso-inertial assessment: Reproducibility analysis anddescriptive data. Isokinetics Exerc Sci, 14, 53-62, 2006.32,521,510,50ULgMytestMyo-Corr(%1RM)30 30 30 30 30 30 30 30 50 50 50 70 70 95 95Figure 3 – The yellow curve represents the Vmaxrecalculated for each load based on the gross accelerationdata of the Myotest®