Reliability and variability of Speed4lifts compared to 6 other devices for the assessment of movement velocity at different intensities in the bench press.
In this article we will present the key points of the study published in the Journal of Strength and Conditioning Research (2019). It is carried out by the research group of the University of Granada.
The aim of this study was to compare the reliability and validity of seven devices available on the market to measure the speed of movement during the bench press exercise. It also studied the variability in the measurements that occurred in the devices between different repetitions.Two test sessions were completed with a sample of fourteen men. All of them knew the bench press movement and did not have any type of musculoskeletal injury.Two sessions were performed with a difference of 48-72 hours between them. In the first session the maximum repetition was determined (1RM) and in the second session each session performed three repetitions with five loads with the following percentages: 45-55-65-75-85%. Lower percentages were discarded, as they were of little use in real practice, and higher percentages were also discarded in order not to distort the exercise technique due to fatigue.
Mean velocity was taken as a measurement simultaneously with all the devices. They were measured:
- – 1 Linear speed transducer (T-Force)
- – 2 linear position transducers (Chronojump and Speed4lits)
- – 1 optoelectronic camera based on a camera (Velowin)
- – 1 application for Smartphone (PowerLift)
- – 2 inertial measurement units (PUSH band and Beast sensor)
- – 1 optical motion detection system (Trio-OptiTrack) as standard Gold.
In the following image it gathers a representation of the taking of data together with all the devices ordered from the most to the least reliable.
The hetereoscedasticity of the results was also studied. This means the value of variability of each device. It was observed that although all devices always present some error, only in the measurements with Speed4lifts the error in the data was not variable. That means that it will always take data reliably and constantly, under the same circumstances.
A perfect association was observed between Trio-optiTrack and the different devices. Range of Pearson’s product-moment correlation coefficient (r) = 0.947-0.995; P < 0.001) With the exception of Beast Sensor (r = 0. 765; P < 0.001).
These results suggest that velocity/position linear transducers, camera-based optoelectronic systems, and the smartphone application could be used to obtain accurate velocity measurements for restricted linear movements, while the inertial measurement units used in this study were less reliable and valid.
As a final conclusion, the authors themselves with these results suggest that it is this device, Speed4lifts, the most appropriate to measure execution velocity due to its high precision, ease of use and affordable price.
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Direct access to full paper HERE