# Effectiveness of Lower-Cost Strategies for Running Gait Retraining: A Systematic Review
## 4 Discussion
### Limitations of Studies and Future Directions  
Some limitations should be considered when interpreting the findings of this review. To quantitatively evaluate the articles, the AXIS tool was used, which showed that all studies presented a very high quality for a cross-sectional design. However, the majority of the studies were unable to justify the sample size or its representativeness as a target population or to explain how they recruited the runners. This information was important to ensure that the recreational runners evaluated in these studies truly represented the population of interest. There were also significant limitations for some of the retraining studies: 54% of the studies did not incorporate a control group (Tables 3 and 5), which is essential to determine the effectiveness of the intervention. Still, in relation to the sample, of the 22 studies included, only the studies by [PERSON] et al. and [PERSON] et al. [47; 58] examined the effects of real-time feedback in runners who had presented injuries in the past 12 months, which limited the clinical applicability of the evidence-synthesis findings. Although the use of biofeedback in healthy runner populations demonstrates the clinical feasibility of this intervention potentially for purpose or prevention, there is no evidence that achieving the biomechanical modifications sought during feedback training will positively affect pain and functional outcomes in an injured population [34].  
In relation to the intervention protocols performed in the studies, a great variability in duration was found: 54% of the studies had eight or more interventions [30; 31; 32; 47; 54; 55; 57; 60; 62; 66; 67; 68] and 27% of the studies performed the intervention through a single session to verify the immediate effects of feedback [48; 56; 61; 63; 64; 65]. Variability was also noted in the instructions provided to the experimental group, and 68% of the studies instructed the sample to run more smoothly, more quietly, and/or with the PPA below a threshold, which ranged from 10% to 50% in relation to the baseline depending on the study [30; 31; 32; 47; 48; 57; 58; 61; 62; 64; 65; 66; 67; 68]; 27% of the studies instructed the sample to increase the rate of steps [40; 54; 55; 56; 59; 60]; and one study did not provide instructions to the participants [63]. In addition, only two studies [48; 67] included an assessment of the long-term running retraining retention (12 months) that met the Cochrane Group guidelines [80]. As a result, it is unclear what effect some of these interventions might have once incorporated into a habitual running pattern rather than being tested when the intervention is still new.  
We identified only nine (41%) studies [40; 48; 55; 56; 57; 59; 60; 65; 69] that included only lower-cost equipment in their methodology to conduct the intervention/assessment. As a result, the methodological replicability of many studies was limited to most clinicians and trainers due to the lack of accessibility to high-cost equipment. There was a trend in recent studies to use an accelerometer to examine the external impact load during running, but few studies used an accelerometer for monitoring outside the laboratory environment in order to make the intervention/assessment more ecological. It is necessary for future studies that use lower-cost equipment in their interventions to effectively report their validation. Finally, there is a need for future studies that include new wearable technologies that provide feedback, such as instrumented socks and insoles, in order to identify their validity in terms of monitoring biomechanical variables and their effectiveness in running retraining programs.