# Validation of a Wearable IMU System for Gait Analysis: Protocol and Application to a New System
## 2 Materials and Methods
### Experimental Setup for Validation  
Subject selectionIn accordance with the criteria for sample sizing and subject inclusion (reliable statistical computation and homogeneous/comparable data), the research protocol defines the proper number and typology of subjects to be studied. If required, the experimental protocol must be approved by the Institutional Review Board and informed consent must be obtained from each subject. A collaboration with skilled clinicians permits us to define specific inclusion criteria for healthy and pathological subjects following the focus of the research. With respect to the normal gait, a population of pathological subjects has walking differences induced by their proper specific pathology. This selection has to be specific because the motor impairment could result in different patient outcomes. Single patients or a small population of impaired patients can then be considered as a case study or for functional assessment. It is true that having large numbers on which to do statistics makes the results even more robust, but we must also consider that, especially when studying pathological subjects, it is not always so easy to recruit homogenous clusters of pathological subjects. If this is the case, to have a comparison with normal or reference data, double the number of subjects needs to be examined. In this study, the voluntary subjects were selected and recruited by the clinical staff of Villa Beretta Rehabilitation Center Hospital, Costa Masnaga, Lecco, Italy. Informed consent was obtained from each subject. The selection for this study includes healthy subjects but with different genders (50%) and anthropometric features so to increase the reliability of the experiment with respect to human variability. In total, 10 subjects were examined: five males and five females, aged between 19 to 49 years with (mean value 32.1 \(\pm\) 9.5 years). All of them were in good health. The weight of the subjects ranged from 46 to 152 kg (mean value 73.1 \(\pm\) 30.3 kg). Their height ranged from 154 to 187 cm (mean value 170.6 \(\pm\) 10.7 cm). Their BMI ranged from 19.4 to 43.5 (mean value 24.5 \(\pm\) 7.0). The subjects have been selected to include a wide range of variation in relation to anthropometric parameters. \(S_{\text{anth}}\) anthropometric step length was calculated [23; 24; 27; 28] and ranged from 47.8 to 64.0 (mean value 59.1 cm) (Table 1). _Laboratory setup_. All testing was conducted in the same location: the Villa Beretta Rehabilitation Center Hospital, Costa Masnaga, Lecco, Italy. We considered the minimum number of steps for the trial equal to 8. At least these steps should be required from the subjects so to exclude the first two steps (starting gait) and the last two steps (ending and braking steps to stop walking). In this way, it is possible to consider the four (up to five to six) central steps to be analyzed as a straight gait. It means that we have two strides into the calibrated volume of GA for data analysis. This implies a proper linear length of the laboratory pathway of 8-10 m and a correct setup definition of the start and finish line of the walk (Figure 2). The measurement with the IMU includes all the movement of the subject along the path and not only the steps during the straight gait. Along the distance, no lines to identify the start and stop were used; distance is not fixed to avoid constraints and to generate natural walking.