# Effectiveness of Lower-Cost Strategies for Running Gait Retraining: A Systematic Review
## 4 Discussion
Collectively, the effectiveness of metronomes, smartwatches, digital cameras, and instrumented socks and insoles, which are lower in cost and consequently clinically accessible, in retraining programs that aim at the intervention and/or evaluation of the results of the cadence and foot strike pattern can be effective in reducing the impact load variables. Effectiveness of Lower-Cost Equipment for Changes in the Peak Positive Acceleration of the Tibia and Footwear  
Several studies used kinetic measures to analyze impact loads (forces applied to the skeleton when contact with the ground occurs) because these measures demonstrate a potential association with injuries due to overuse of the lower limbs [72; 73; 74; 75; 76]. For the analysis of impact loads, the most commonly used variables are peak vertical impact, average vertical load rate, instantaneous vertical load rate, tibia and footwear PPA, shock attenuation, vertical stiffness, and leg/lower extremity stiffness [35]. Accelerometers, which are small, lightweight devices, make it possible to identify the PPA of the tibia, which is strongly correlated with mean vertical force and instantaneous vertical load rates, two common biomechanical parameters that indicate impact load and are associated with running-related injuries [77]. Previous studies used laboratory equipment such as force platforms or instrumented treadmills to provide biofeedback of kinetic parameters to participants [78; 79]. However, the accessibility of biomechanics laboratories for clinical applications is generally limited, and treadmills equipped with force transducers are expensive equipment and are not readily available. On the other hand, accelerometers are relatively inexpensive compared to instrumented treadmills and are readily available [61]. Therefore, lightweight accelerometers have been used as a substitute instrument for impact load estimation in the absence of instrumented treadmills [31]. In the current study, we found that accelerometers were used as a tool for intervention through the provision of real-time feedback in 91.7% of the analyzed studies (Tables 4 and 5); in 54.5% of the studies the feedback was visual [31; 32; 61; 62; 65; 66], in 18.2% it was auditory [30; 64], in 9.1% it was tactile [68], in 9.1% it was auditory and visual [63], and in 9.1% it was auditory and verbal [69]. Only the study by [PERSON] et al. [67] used an accelerometer to assess the results of the intervention in relation to the PPA of the tibia. Based on the results of studies that performed interventions with the use of an accelerometer to reduce the PPA of the tibia and/or footwear, a significant mean decrease of \(\sim\)31% in PPA values between pre- and post-training was identified; in some studies, these values were close to 50%. In a study by [PERSON] and [PERSON] [62], a sample constituted by runners with a tibial PPA \(>\)8 g and an intervention of eight sessions was conducted in which the runners were required to run more smoothly, make the steps silently, and (through visualization of a screen) keep their PPA below a horizontal line that represented 50% of the average PPA in the pre-training. The results showed that the tibial PPA decreased 48% after retraining, which was maintained in the one-month follow-up. In a study by [PERSON] et al. [68] that was conducted using runners with high tibial acceleration and an intervention of eight sessions, runners were required to run with softer steps and eliminate the tactile feedback of vibration, the threshold of which was 10% below the tibial acceleration that resulted from the baseline. The results showed that the tibial acceleration from pre- to post-intervention when running on a treadmill decreased by 50%; while for running on the ground, it decreased by 28%. Based on the above, it can be stated that there is strong evidence of the effectiveness of accelerometers in interventions with feedback for running retraining. According to [PERSON] et al.