Validity and Reliability of a Smartphone Accelerometer for Measuring Lift Velocity in Bench-Press Exercises

Abstract

The aim of this study was to determine the validity and reliability that a smartphone accelerometer (ACC) used by a mobile basic program (MBP) can provide to measure the mean velocity of a bench-press (BP) lift. Ten volunteers participated in the study (age 23.1 ± 2.5 years; mean ± SD). They had more than one year of resistance training experience in BP exercise. All performed three attempts with different loads: 70%, 90%, and 100% of the estimated value of the one-repetition maximum (1RM). In each repetition, the mean velocity was measured by a validated linear transducer and the ACC. The smartphone accelerometer used by the mobile basic program showed no significant differences between the mean velocities at 70% 1RM lifts (ACC = 0.52 ± 0.11 m/s; transducer = 0.54 ± 0.09 m/s, p > 0.05). However, significant differences were found in the mean velocities for 90% 1RM (ACC = 0.46 ± 0.09 m/s; transducer = 0.31 ± 0.03 m/s, p < 0.001), and 100% 1RM (ACC = 0.33 ± 0.21 m/s; transducer = 0.16 ± 0.04 m/s, p < 0.05). The accelerometer is sensitive enough to measure different lift velocities, but the algorithm must be correctly calibrated.

Validity and Reliability of Mobile Applications for Assessing Strength, Power, Velocity, and Change-of-Direction: A Systematic Review

“…Characteristics of the included studies can be found in Table 3 . The apps presented in the included articles were compared with motion a capture system [ 40 , 61 , 68 , 69 ], linear encoder and transducers [ 56 , 59 , 60 , 62 , 63 , 64 , 71 ], as well as with contact platforms [ 37 , 39 , 41 , 57 , 61 , 62 , 63 , 66 ], accelerometers [ 59 , 62 , 63 , 68 , 70 ], and time photocells [ 55 , 65 , 67 , 70 ].…”

“…Among the included studies, [ 39 , 53 , 56 , 59 , 62 , 63 , 64 ] tested the bench press, [ 64 , 68 ] the back squat, [ 60 ] the half squat and full squat [ 39 , 53 ], [ 40 ] the snatch, [ 53 ] the hip thrust, [ 68 ] the power clean, [ 37 , 41 , 57 , 61 , 66 , 71 ] the vertical jump (CMJ, SJ or DJ), [ 58 ] the running, [ 65 , 67 ] the sprint or agility [ 55 , 70 ] the static and dynamic arm swing.…”

“…The study of Viecelli et al [ 69 ] revealed that the accelerometer app had a strong correlation (r > 0.93; p < 0.05) and a small absolute mean error (0.16%) when compared to a video recording system. Conversely, the other study [ 56 ] compared the accelerometer app with an LPT, revealing a lower correlation with the “reference” device (r = 0.54) than Viecelli et al [ 69 ]. Moreover, the authors suggested that the app may not be completely valid for measuring strength because meaningful differences were found in mean velocities with higher lifting loads >90% 1RM [ 56 ].…”

“…Notwithstanding the fact that, overall, the studies revealed acceptable validity of the My Lift app for measuring different displacement velocities for different exercises, most of the studies compared the My Lift app with different “reference” devices. In fact, while some authors refer to 3D capture systems as the gold standard device for velocity-based training (VBT) [ 40 , 68 ], others refer to LPTs as the gold standard [ 56 ]. Indeed, other studies noted that there is no evidence supporting the use of a 3D system as a reference device [ 59 ].…”

“…Furthermore, two other studies used basic smartphone accelerometer data to assess the mean bar velocity of different strength exercises [ 56 , 69 ]. The study of Viecelli et al [ 69 ] revealed that the accelerometer app had a strong correlation (r > 0.93; p < 0.05) and a small absolute mean error (0.16%) when compared to a video recording system.…”