runrhythm: a custom smartphone application for enhancing locomotor-respiratory coupling in runners

Enhancing Running Performance and Comfort Using RunRhythm

Running is perhaps the most widely popular form of exercise in part due to its accessibility and range of physical and mental health benefits1,2. Nonetheless, many aspiring runners struggle to start or maintain running habits. This could be due to breathing difficulties, which affect an estimated 20-40% of runners3,4,5. Reducing exercise-induced breathlessness is theoretically possible with the use of specific breathing techniques, but the exact methods, risks, and benefits of doing so are unclear. While improving fitness and/or slow-paced breathing at rest may alleviate respiratory discomfort during exercise6,7, these solutions take weeks or months to realize benefits. Some research has speculated that the direct implementation of breathing techniques during exercise may be more effective at producing acute benefits8, although such investigations are limited. Digital tools that enable individualized instruction might be needed to perform such studies in an effective intervention format.
Locomotor-respiratory coupling (LRC) is a synchronization phenomenon in which breathing and movement are frequency- and/or phase-synchronized. In specific exercises such as running, LRC indicates a whole-integer ratio between breathing (BR) and step rate (SR), as well as phase locking of footstrike to breath onset (i.e., stepping exactly on inspiration). LRC can be expressed volitionally or automatically and may emerge as a learned behavior with exercise training9. Humans naturally synchronize gait with interfering auditory noises (including breathing) perhaps to reduce auditory stimulation, which suggests LRC has evolutionary phenomenology10. Some reports indicate that LRC benefits movement economy and performance, and reduces breathlessness11,12,13,14,15. Some studies reported negligible benefits16,17,18. Any physiological benefits could be related to &#34;step-driven flows&#34;: each footstrike creates downward momentum of the abdominal contents (the &#34;visceral piston&#34;), which when synchronized with the onset of inhale or exhale can be additive to ventilation.
Daley et al.19 measured ventilatory flow and impact forces during treadmill running and speculated that step-driven flows can contribute up to 10-12% to total ventilation. They also reported that it could speed up ventilatory transitions. Other neuromechanical mechanisms may interact with this phenomenon9. While the visceral piston is a result of precise phase coupling, frequency coupling may be independently valuable, especially to the novice runner. BR is closely related to effort across different exercise intensities20. As SR is generally stable and associated with running speed21, LRC may support self-awareness and enable easy pacing of BR and, thus, intensity throughout the run. Finally, LRC at uneven ratios (e.g., 5:1 steps per breath) could help to prevent exercise-related transient abdominal pain (&#34;side stitch&#34;). A majority of runners experience this temporary, but distracting and painful symptom each year22, often leading to their need to stop running. One theory of side stitch etiology is that repeated breathing on the same side footstrike may irritate the phrenic nerve. Thus, it might be avoided by LRC at uneven ratios, which leads to breathing on alternate legs.
Few reports have discussed how to support runners in performing LRC. At least two studies have exhibited biofeedback-style methods14,23 while many utilized simple verbal coaching24,25. While these methods have shown promise in stimulating LRC acutely, they are highly standardized and require specialized equipment. As such, they are likely not suitable for field applications, nor are they accessible to most runners. Regardless, sound guidance is a natural choice since humans intuitively synchronize movement to predictable auditory events (metronome or music)26. Applications should thus carefully consider sound tempo and structure in the context of motor learning. While simple, constant-tempo audio is predictable and efficacious for stimulating entrainment, it contradicts the naturally nonlinear behavior of step and respiratory rhythms in healthy runners27,28. Changing a runner&#39;s preferred SR might reduce running economy 29 or could modify injury risk factors30. Thus, sound instructions should be continuously adapted in real time to follow the runner&#39;s SR31.
We recently introduced a concept that integrates the above recommendations into a simple, user-friendly, custom smartphone application32. The first iteration allows for the selection of a single LRC ratio to be instructed throughout the run. The phone&#39;s stock SR algorithm is leveraged to provide real-time SR information to the application. Then, step-synchronized sounds are produced indicating when the runner should exhale and inhale: a high-pitched tone for steps during inhalation, and a low-pitched tone during expiration. Prescribed LRC ratios were derived from a control visit without breathing instruction. We found a large increase in LRC from 26.3 &#177; 10.7% to 69.9 &#177; 20.0% of the run with the application instruction during outdoor submaximal running. Limitations noted with the protocol and application include extensive familiarization required, limited sample size, and constant sound instruction. Hence, a new version of this application was developed to improve user experience and enable more broad testing and experimentation in field exercise. This application is titled RunRhythm since its intended purpose is to support runners in finding and maintaining a rhythm during running. It will be referred to hereafter as the app.
The purpose of this report is to introduce a new digital tool and methodological approach that enables intuitive and field-ready LRC guidance for research studies involving experienced or aspiring runners. The app is a research-grade application in beta testing for Android devices. The core functionalities of the application are SR detection and LRC guidance. When running is detected, breathing sounds are created according to the selected settings in the user interface. The application calculates SR from the phone accelerometer using one of two algorithms: either the factory SR algorithm implemented by the device manufacturer or a custom SR algorithm created by the application manufacturer. Both algorithms produce a constant livestream of SR, which is then smoothed on a moving average according to an adaptive window. The window size is dynamic to balance reactivity and outlier smoothing. The result is a constantly updated value of live SR.
Since the app calculates SR from the device movement, the placement of the phone on the body is of utmost importance. Most stock SR algorithms are position-agnostic, and therefore, can be placed on any part of the body during running to produce accurate SR values. The custom algorithm implemented here also behaves as such. However, a firm placement closer to the center of mass may improve the stability of the SR detection, and as a result, the sound quality produced by the app. Pilot testing shows that placements with 1-dimensional oscillation (i.e., vertically up and down such as in a chest pocket or waist pack) may perform better than those with 2-dimensional movement (i.e., swinging such as in a thigh pocket or armband).
SR data are fed to an integrated sound engine (see the Table of Materials). Step sounds are played only if the system detects SR &#62; 0. When the SR is above a preset threshold (determined in backend settings [protocol section 3.6]; i.e., 120), the application understands that the user is running and triggers the start of breathing guidance sounds. Then, this live SR value is used to set the tempo of the step and breathing guidance sounds as long as a &#34;running&#34; SR value is maintained. When SR &#62; threshold, the sounds generated match the tempo of SR by default. The exception is when the backend setting &#34;sound tempo&#34; is altered (determined in backend settings [protocol section 3.5]). For example, with a selected upper limit of 180, even if the runner begins running at a higher SR of 185, the sound tempo will not exceed 180. When they lower their SR down to 175, the sounds will lower to 175, continuously adjusting within the preset limits. As described in protocol step 3.5, these sliders allow the user or researcher to set limits on the minimum and maximum sound tempo (bpm). The app allows different LRC ratios (steps:breath) to be selected before or changed during the run. The number of steps per breath phase can be changed from 2 to 9; i.e., a 2:3 ratio reflects 2 steps per inhale and 3 steps per exhale.
Different &#34;soundscapes&#34; were designed to provide a pleasant audio experience to more runners with diverse music tastes based on user feedback and early in-lab experiments33. They have different sounds mapped to the real-time step rate, the instructed breathing phases, and background ambient noise. Step sounds are simple beats that play at the tempo of each footstrike (i.e., right and left steps). Breath sounds integrate several sonic elements and play at a much slower tempo depending on the chosen LRC ratio. The soundscapes available are tribal: organic and instrumental with sharp breathing transitions and step sounds; calming: light and ocean-inspired with smooth transitions and step sounds; energizing: electronic and driving with sharp transitions and step sounds; minimal: simple and smooth with only breath sounds (no step sounds).
The voiceover feature adds simple voice cues corresponding to best-practice research findings regarding LRC familiarization. It provides a series of instructions at the start of the run and then every 5 min after that. First, it states the selected LRC ratio. Then, it states the intended breathing phase in sync with the sound cues for the first three breath cycles. Then it reminds the user, &#34;find your step rate, and step to the beat.&#34; For each run, a pre and post run questionnaire is integrated to add subjective feeling data to each run. The subjective vitality short scale34 asks a single item regarding the runner&#39;s feeling from 0 to 10. A 0-10 rating of the fatigue scale asks the user to rate their current state of fatigue. Finally, a 0-10 scale rates the degree of breathlessness currently experienced. All of these scales are asked before and after each run. Only after the run, the user is asked to rate their experience of the run&#39;s intensity (i.e., light, medium, high, intervals). Users can change the LRC ratio and temporality during the run using the on-screen interface or headphone controls. This may help users feel agency during the run and enables the exploration of personal suitability. In addition, the ratio may need to be quickly changed in response to running events (e.g., hills, fatigue). This protocol includes a description of how to run with the app and later recommendations for its use within research protocols of various types (i.e., indoor, outdoor, interventional, cross-sectional).

Author Spotlight: Exploring Breathing Techniques and Digital Solutions for Enhancing Running Performance

Custom Smartphone Application to Guide Locomotor-Respiratory Coupling in the Field Using Step-Adaptive Breathing Sounds 

We are interested in understanding breathing during exercise. While many runners experience respiratory limitations, few attempts have been made to address this directly during exercise. Locomotive respiratory coupling is one such breathing technique that could help, although it is rather difficult to learn.Digital solutions such as smartphone applications could potentially enable this. Breathing strategies might help to alleviate respiratory pathologies and dysfunction as well as improve performance. However, altering highly automated processes such as breathing are likely to be acutely ineffective.Therefore, habitation and practice is necessary to realize such benefits. Mobile low-friction tools such as smartphone apps have the potential to provide such benefits in a more accessible and user friendly manner. We've previously demonstrated that step synchronized sound guidance can effectively support coupling in novice runners within only one or two sessions.Furthermore, while lab studies have shown mixed results for the benefits of coupling, we were the first to report that coupling in free running conditions is associated with increases in running speed as well as decreased ventilatory variability. Run rhythm differs from previous solutions since it utilizes generic smartphone and headphones, making it easy accessible for longitudinal studies. And furthermore, it uses easily understandable sound feedback, which was optimized throughout various user studies.Clever solutions such as music integration and temporality improved their user experience during the run. The creation of the application and the related studies paved a way for new research questions such as how can runners be dynamically supported with these breathing techniques during the run? And how can these breathing techniques be enhanced and integrated in run trainings programs such as interval training?

RunRhythm: A Custom Smartphone Application for Enhancing Locomotor-Respiratory Coupling in Runners

To begin, ask the participant to fill out a pre-participation questionnaire with elements such as informed consent, running history and respiratory health. Download the run rhythm application to a functioning smartphone running Android 8 or higher version. Familiarize the runner with coupling, and the application.Before discussing and instructing locomotor respiratory coupling with the app, perform an individual calibration to determine the runner's natural coupling ratio. Choose a simple running task, and record their step and breath rate during the trial. calculate the nearest whole integer ratio from their quotient.Begin with rhythmic foot tapping, and instructions to breathe at a given ratio in sync with the feet. Repeat while walking, and then while running in place. In the application, choose the desired soundscape.using the horizontal toggle. Select start run to begin. If using the app for the first time, press allow to permit the device logging of movement and location.Before each run, complete the onscreen questionnaires by pressing on the numbers corresponding to the current feeling experienced by the runner. Use the up or down toggle to change the desired coupling ratio. Lock the toggle with the lock icon.Then toggle the voiceover feature with the interface toggle at the bottom right. Set the sound tempo sliders to the desired step rate thresholds. After describing the user interface to the runner, fasten the device to the runner's body.using a waist pack fitted firmly to the body. Click start run and begin running. When the step sounds activate, listen closely and step to the beat.Then match inspiration and expiration precisely to the sound when the breathing guidance is activated. Encourage the runner to keep stepping at their own pace while the sounds adjust to their step rate. Instruct the runner to breathe according to the breathing sounds.Continue stepping and breathing with the sounds for 30 to 60 seconds. Have the researcher and runner run together while playing the guidance sounds over a Bluetooth speaker. to reinforce coupling fundamentals.Use headphones during outdoor running to improve the delivery of the sound instructions, and enable headphone controls on the application. During the run, change the coupling ratio and temporality using the toggles on the onscreen interface. After the run, press end run to stop the application.A summary screen displays key metrics including total distance, average pace, and average step rate. Finally, download log files to access timestamped data of the run and application parameters. Running with LRC guidance greatly increased LRC adherence in 17 novice runners exemplified by one participant's increase from 7.9%to 84.1%After a four week intervention, one participant's LRC increased from 39.7%to 53.4%resulting in a lower average breath rate, and increased ventilatory efficiency.

runrhythm-custom-smartphone-application-for-enhancing-locomotor

Research

JoVE Journal

Biology

While running is amongst the most popular activities for competition and leisure, an estimated 20-40% of runners may suffer from respiratory limitations. Some of these runners may benefit from breathing techniques to improve performance or alleviate respiratory discomfort. One such technique is locomotor-respiratory coupling (LRC), a frequency and phase synchronization of breath to step. Studies have demonstrated that LRC may benefit ventilatory efficiency via "step-driven flows," and some experts have argued it could be used for pacing exercise or increasing positive emotional states. Nevertheless, it may be difficult to perform without coaching or guidance. Here we propose RunRhythm, a custom smartphone application to deliver step-synchronized sound guidance for LRC. This concept builds on previous evidence that sound guidance can be effective and integrates features to maximize adherence and individualization. Preliminary results show that this application is a promising and efficacious method suitable for research on LRC in field exercise. Recommendations for use and further development are discussed to further develop this concept for the benefit of a wider population.

Locomotor-respiratory coupling (LRC) is potentially advantageous for runners but may be difficult to perform. We introduce a custom solution implemented on a smartphone to individualize and guide runners toward LRC.

While running is amongst the most popular activities for competition and leisure, an estimated 20-40% of runners may suffer from respiratory limitations. ...