To correctly prescribe a strength training program, it is essential to assess an individual`s maximal strength (1RM). Determination of 1RM can be done directly and indirectly by prediction equations. The aim of the present study was to evaluate the validity and the reliability of the prediction of 1RM assessed with an inertial measurement unit during 4 different trials. Methods: Six males (23±2yrs; 76±11kg; 177±6cm), all trained from different sports, with no experience in weight lifting, were recruited for the present study. The participants performed 4 trials (T1, T2, T3 and T4) for the upper (UL) and lower (LL) limbs, with a rest of minimum 2 days. The 1RM for UL was conducted at the chest press (Technogym, Gambettola, Italy) whereas the LL 1RM on a horizontal leg press (Technogym Gambettola, Italy). Each trial consisted in a direct measurement (1RM) and an indirect measurement for UL and LL. Tests on the same trial were randomized. The direct measurement was performed with an incremental test arriving at the load that participants could lift only once. The prediction of 1RM was assessed using FreePower (Sensorize S.r.l., Italy), a software that inputs acceleration data measured by a wireless inertial measurement unit fixed to the weight stack of the machine through a magnetic pocket. The software estimates 1RM by using a mathematical relationship between force, power and velocity measured in correspondence of at least three increasing loads. Repeated measures ANOVA (p<0.05) was used to evaluate differences between trials and between direct and indirect measurements. Intraclass correlation coefficients (ICC) were used to evaluate reliability. Retest correlation was measured by Pearson correlation coefficient (p<0.05). Results: Differences emerged for 1RM between T1 and T2 (p<0.05) and T3 and T4, in both direct and indirect measurements for UL and LL. Thus, to evaluate the ICC only T3 and T4 were considered. A high ICC (range 0.973-0.998) were fond for UL and LL in both direct and indirect measurements. In addition, the retest correlation was >0.95. No differences emerged between direct and indirect measurements. Discussion: Determination of 1RM is fundamental to prescribe correct resistance training programs in different sports. Direct 1RM measurement is time consuming, and may lead to muscle soreness as well as temporary deterioration of the function of the tested muscles. Differences founded for T1 and T2 demonstrate that a familiarization session is needed both for direct and indirect measurements. Since no differences emerged between direct and indirect measurements, results of this study demonstrated that FreePower is a reliable and useful device to determine 1RM.
© Copyright 2012 17th Annual Congress of the European College of Sport Science (ECSS), Bruges, 4. -7. July 2012. Published by Vrije Universiteit Brussel. All rights reserved.