Test-Retest Reliability of Velocity and Power in the Deadlift and Squat Exercises Assessed by the GymAware PowerTool System

Abstract

We explored the test-retest reliability of velocity and power assessed by the GymAware PowerTool system (GYM) in the deadlift and squat by simulating a context with and without a familiarization session. Sixteen resistance-trained individuals completed three testing sessions. In all sessions, velocity and power were assessed by the GYM system in the deadlift and squat exercises with loads of 30, 45, 60, 75, and 90% of onerepetition maximum. The consistency of test results between the first session and the second session was considered to represent the reliability with no familiarization session. The consistency of test results between the second session and the third session was considered to represent the reliability with one familiarization session because the first session simulates a familiarization session. Intraclass correlation coefficients (ICCs) ranged 0.63-0.99 in the deadlift, and 0.78-0.99 in the squat. ICCs were higher than 0.75 for 93 and 100% of all deadlift and squat tests, respectively. For velocity and power, standard error of measurement ranged 0.03-0.08 m/s and 20-176 W, respectively. The coefficient of variation ranged 2.2-10.6% for the deadlift and 2.6-6.9% for the squat tests. Except for peak and mean velocity at 30% of 1RM in the squat, we found no significant improvements in reliability with a familiarization session. The test-retest reliability of velocity and power assessed by the GYM system was moderate-to-excellent for the deadlift and good-to-excellent for the squat. Reliability of velocity and power did not seem to improve with a familiarization session.

Validity and Reliability of the Inertial Measurement Unit for Barbell Velocity Assessments: A Systematic Review

“…For this purpose, different commercial devices can be used to quantify velocity [ 23 ]. Among the available options, solutions can be grouped as follows [ 24 ]: (i) isoinertial dynamometers consisting of a cable-extension linear velocity transducer attached to the barbell [ 25 , 26 , 27 ], (ii) optical motion sensing systems or optoelectronic systems [ 28 , 29 , 30 , 31 ], (iii) smartphone applications involving frame-by-frame manual inspections [ 29 , 32 , 33 ], and (iv) inertial measurement units (IMUs) [ 34 ]. Since these different technologies offer different possibilities, it can be considered that IMUs represent the most easy-to-use solution because no cable-extension is needed—the sensor simply needs to be attached to the barbell.…”

Assessment of Back-Squat Performance at Submaximal Loads: Is the Reliability Affected by the Variable, Exercise Technique, or Repetition Criterion?

“…Mean and peak values of velocity and power are commonly collected with LPTs against the same absolute loads before and after training to detect changes in strength performance [5][6][7][8]. Previous studies have reported an acceptable reliability for velocity and power variables collected across a wide range of submaximal loads in different exercises such as the bench press [9][10][11], back-squat [10,12,13], and deadlift [12,14,15]. However, there is no definitive evidence regarding which of the different velocity and power variables (mean velocity [MV] vs. mean power [MP] vs. peak velocity [PV] vs. peak power [PP]) that can be collected with a LPT provides the most reproducible assessment of performance in basic resistance training exercises [9,10,12,14].…”

“…The back-squat exercise can be performed using the pause (i.e., a pause of 1-4 s is implemented between the lowering and lifting phases) or rebound techniques (i.e., the lifting phase is performed immediately after the lowering phase using the stretch-shortening cycle) [19,20]. Previous studies have reported acceptable levels of reliability for the measurements of MV, PV, MP, and PP (coefficient of variation [CV] ≤ 8.40%; intraclass correlation coefficient [ICC] ≥ 0.58) collected by the LPT GymAware PowerTool across a wide range of relative loads (20-90% of one-repetition maximum [1RM]) during the free-weight back-squat exercise performed with the rebound technique [10,12]. More importantly, although the reliability was not explicitly compared in these studies, MV (CV range = 3.10-6.70%) and PV (CV range = 2.60-5.50%) were generally collected with a higher reliability than MP (CV range = 3.00-8.00%) and PP (CV range = 3.60-7.40%).…”

“…Practitioners then need to decide whether the best (i.e., the highest) or the average value of these repetitions will be used for comparative analyses. Some studies have used the average score of all repetitions [10,11,14,15,22], other studies have used the best score [23,25], and others did not directly specify the repetition criteria used for data analysis [12,19]. Given the diversity of repetition criteria, previous research has explored whether the best or average scores are more appropriate as an indicator of physical performance [26][27][28][29].…”

“…Specifically, this study aimed to compare the betweensession reliability between (i) 4 performance variables (MV vs. MP vs. PV vs. PP), (ii) 2 exercise techniques (pause vs. rebound), and (iii) 2 repetition criteria (best vs. average scores). It was hypothesized that (i) MV and PV would be the most reliable variables, followed by MP, and finally PP [10,12], (ii) the pause technique would provide more reliable outcomes than the rebound technique [19], and (iii) the average score would provide comparable or greater reliability outcomes than the best score [26,28].…”