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.

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.

Functional evaluation and rehabilitation engineering.

Life is complex and all about movement, which allows us to interact with the environment and communicate with each other. The human nervous system is capable of performing a simultaneous and integrated control of 100-150 mechanical degrees of freedom of movement in the body via tensions generated by about 700 muscles. In its widest context, movement is carried out by a sensory motor system comprising multiple sensors (visual,auditory, and proprioceptive),multiple actuators (muscles acting on the skeletal system),and an intermediary processor that can be summarized as a multiple-input­multiple-output nonlinear dynamic time-varying control system. This grand control system is capable of responding with remarkable accuracy,speed, appropriateness,versatility, and adaptability to a wide spectrum of continuous and discrete stimuli and conditions and is certainly orders of magnitude more complex and sophisticated than the most advanced robotic systems currently available. In the last decades,a great deal of research has been carried out in the fields of functional evaluation of human performance and rehabilitation engineering. These fields combine knowledge, concepts, and methods from across many disciplines (e.g., biomechanics,neuroscience, and physiology), with the aim of developing apparatuses and methods fort he measurement and analysis of complex sensory motor performance and the ultimate goal of enhancing the execution of different tasks in both healthy people and persons with reduced capabilities from different causes (injury, disease, amputation,and neural degeneration).