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A Journal on Applied Physiology, Biomechanics, Preventive Medicine,
Sports Medicine and Traumatology, Sports Psychology

Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,111

Frequency: Monthly

ISSN 0022-4707

Online ISSN 1827-1928


The Journal of Sports Medicine and Physical Fitness 2012 February;52(1):40-6



Comparison of velocity and power output data derived from an inertial based system and an optical encoder during squat lifts in a weight room setting

Squadrone R. 1, Rodano R. 2, Preatoni E. 2,3,4

1 Ab-Acus, Milan, Italy;
2 Department of Bioengineering, Politecnico di Milano, Milan, Italy;
3 INDACO Department, Politecnico di Milano, Milan, Italy;
4 Sport, Health & Exercise Science, Department for Health, University of Bath, Bath, UK

AIM: The purpose of this study was to assess a new wireless, light and portable inertial measurement system (FreePower; Sensorize, Rome, Italy), by comparing the measures of velocity and power it provides to the same measures derived from a high resolution optical encoder (Ergotest Technology a.s., Langesund, Norway).
METHODS:Fifteen male tennis and soccer players performed back squat lifts at the Smith Machine at loads ranging from 30% to 90% of their established 1RM load. The two devices measured the kinematics of the barbell simultaneously. The mean and peak velocity of the barbell and the mean and peak power applied to the barbell-body system were extracted and used for the comparison.
RESULTS: Measures of velocity and power, both in mean and peak values evidenced significant correlations (P<0.05) between the two systems. Linear regression r-squared values ranged from 0.978 for mean velocity to 0.993 for peak power, showing high-shared variance between the FreePower and the encoder values. Peak velocity, peak power and mean power values showed an absolute percentage difference of 2.8%, 3%, and 3.8%, respectively. The greatest discrepancy between the two systems was found in mean velocity values, where significantly lower values (P<0.05) were measured with the inertial system (-5.3%).
CONCLUSION:The FreePower® inertial system can provide practitioners with measures of velocity and power that are consistent, within reasonable error limits, with a high resolution optical encoder, when it is used in a standard weight room setting and a significant number of lifts are included in the analysis.

language: English


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