Elsevier

Journal of Biomechanics

Volume 47, Issue 7, 7 May 2014, Pages 1739-1741
Journal of Biomechanics

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Use of audio biofeedback to reduce tibial impact accelerations during running

https://doi.org/10.1016/j.jbiomech.2014.03.008Get rights and content

Abstract

Visual biofeedback of tibial peak positive acceleration (PPA) during running has been used successfully as a method of gait retraining to reduce PPAs. Audio biofeedback generated from PPA may present a novel, portable alternative. The purpose of this study was to investigate the feasibility of using PPA-generated audio biofeedback to reduce PPAs while running. Nine runners were fitted with a wireless accelerometer on their left tibia. PPAs were recorded and a custom LabVIEW program was used to emit a single beep once the PPA reached a preset threshold. The numerical difference between this threshold and peak PPA during running was scaled to the pitch of the beep, such that a foot strike with greater PPA would result in a beep with higher pitch. Subjects were then instructed to (1) run without any beeps, and/or (2) keep the pitch of the beep as low as possible. Subjects participated in a single testing session that included a five minute warm-up and two rounds of biofeedback, which consisted of five minutes of running with biofeedback followed by five minutes of running without biofeedback. Subjects were able to significantly reduce PPAs during exposure to audio biofeedback. In addition, two rounds of biofeedback were sufficient for subjects to retain a reduction in PPAs without biofeedback. PPA-generated audio biofeedback therefore appears to be a feasible method of gait retraining to reduce PPAs in runners.

Introduction

Stress fractures are among the most common overuse injuries suffered by runners (Joy and Campbell, 2005, Fredericson and Misra, 2007, Plisky et al., 2007, Wen, 2007). Tibial stress fractures specifically, may account for up to 55% of all stress fractures (Matheson et al., 1987). In an attempt to decrease the risk of tibial stress fractures, several modifiable injury risk factors have been studied (Crowell et al., 2010, Crowell and Davis, 2011). A large portion of research into modifiable risk factors for tibial stress fractures has concentrated on biomechanical variables associated with running. As a part of biomechanical running assessments, researchers have studied the peak positive accelerations (PPA) of the tibia during running (Crowell et al., 2010, Crowell and Davis, 2011). The importance of PPA with respect to tibial stress fractures is demonstrated in a retrospective study by Milner et al. (2006), who found that the PPA magnitude successfully predicted history of stress fracture in female runners in 70% of the cases. In addition, a preliminary prospective investigation by Davis et al. found that runners who went on to develop tibial stress fractures had PPAs almost twice as large as healthy controls (Davis et al., 2004). Collectively, these studies suggest that the magnitude of PPAs of the tibia during running are associated with risk of a tibial stress fracture.

Real-time biofeedback has been posited as a viable method in injury prevention and rehabilitation settings (Tate and Milner, 2010, Giggins et al., 2013). Indeed, real-time biofeedback has recently been used to decrease PPAs in runners. For example, gait retraining programs that provide real-time biofeedback of PPAs during running have been used. Two recent studies used real-time visual biofeedback to help runners positively modify their running mechanics so as to reduce tibial PPAs (Crowell et al., 2010, Crowell and Davis, 2011). Although these studies have successfully used visuzal biofeedback of PPAs, the logistics and equipment used in these studies present some inherent limitations. Specifically, the use of visual biofeedback in a gait retraining study almost certainly implicates that runners rely on a computer screen to receive biofeedback. The reliance on a computer screen subsequently restricts gait retraining to the laboratory or clinic, which in turn, may limit patients to the use of indoor treadmills. Real-time biofeedback paradigms that are based on visual biofeedback therefore restrict the portability of biofeedback devices, which may also limit the ecological validity of their use. To counter these shortcomings, some researchers have proposed the use of audio biofeedback. For example, Cheung and Davis (2011) used audio biofeedback to modify foot-strike patterns in individuals with patellofemoral pain. Although the audio biofeedback in this study was generated from an in-sole footswitch, and only provided information on whether or not individuals ran with a heel-strike pattern, the results provided preliminary data that showed individuals are able to modify running mechanics through the use of audio biofeedback.

The purpose of this study was to investigate the feasibility of using PPA-generated audio biofeedback in real-time to reduce PPAs during running. To this end, we developed a novel LabVIEW-based computer program that collected PPA in real-time, scaled the magnitude of PPA to the pitch of an audible beep, and then played that beep as part of a real-time audio biofeedback protocol. It was hypothesized (1) that runners would be able to use the audio biofeedback to reduce their PPA in real-time and (2) that multiple exposures to audio biofeedback within a single session would have a carry-over effect so that runners would be able to retain a reduction in PPAs in the absence of biofeedback.

Section snippets

Subjects

Nine healthy runners (6 females and 3 males) were recruited from a university population of recreational runners (Table 1). At enrollment and at the time of the study, all participants were running at least 10 miles per week and at least two times per week. All participants ran with a heel-strike footfall pattern. All subjects were healthy and free of any cardiovascular or musculoskeletal conditions that would have hindered full participation in the study. All participants signed an

Results

Average treadmill running speed for all conditions was 7.0±5.6 mph. During the warm-up period PPAs were 5.9±0.7g. The post-hoc analyses identified significant differences between baseline PPAs during the warm-up period and several of the biofeedback conditions (Fig. 1). During the first 5 min of audio biofeedback, subjects were able to significantly (p=0.015) reduce their PPAs to 5.3±0.8g. During the first period of no biofeedback PPAs were 5.6±1.1g, which did not differ from the baseline. During

Discussion

The most important finding of this study was that subjects were able to significantly decrease PPAs during running while listening to real-time audio biofeedback that was generated from an accelerometer attached to the runners׳ tibias. In addition, the results also showed that a total of ten minutes of audio biofeedback was enough for subjects to retain a temporary decrease in PPAs even without real-time biofeedback. Collectively, these results suggest that PPA-generated real-time audio

Conclusion

Runners in this study were able to significantly decrease their PPAs during treadmill running after just five minutes of receiving real-time audio biofeedback. Furthermore, a total of ten minutes of audio biofeedback was enough for subjects to retain a temporary decrease in PPAs even without real-time biofeedback. The observed decrease in tibial impact accelerations during running that occurred as a result of real-time audio biofeedback suggests that this method is a viable option for gait

Conflict of interest

None.

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