30 This study aimed to determine if a quantifiable relationship exists between the peak 31 sound amplitude and peak vertical ground reaction force (vGRF) and vertical loading 32 rate during running. It also investigated whether differences in; peak sound 33 amplitude, contact time, lower limb kinematics, kinetics and foot strike technique 34 existed when participants were verbally instructed to run quietly compared to their 35 normal running. Twenty-six males completed running trials for two

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... nd 36 conditions; normal running and quiet running. Simple linear regressions revealed no 37 significant relationships between impact sound and peak vGRF in the normal and 38 quiet conditions and vertical loading rate in the normal condition. T-tests revealed 39 significant within subject decreases in peak sound, peak vGRF and vertical loading 40 rate during the quiet compared to the normal running condition. During the normal 41 running condition, 15.4% of participants utilized a non-rearfoot strike technique as 42 compared to 76.9% in the quiet condition, which was corroborated by an increased 43 ankle plantarflexion angle at initial contact. This study demonstrated that quieter 44 impact sound is not directly associated with a lower peak vGRF or vertical loading 45 rate. However, given the instructions to run quietly, participants effectively reduced 46 peak impact sound, peak vGRF and vertical loading rate. 47 48 49 Keywords: augmented feedback, locomotion, biomechanics, ground reaction force, 50 running technique, foot strike technique sound amplitude, vGRF, vertical loading rate and contact time. It was further 121 hypothesized that habitual RFS runners would increase their plantarflexion angle at 122 initial contact and thereby change to a non-RFS technique, but that the joint 123 kinematics of non-RFS runner's would be unaffected. 124 125 microphone. Future research should investigate runners of different abilities, female 413 runners, different surfaces, shod running, running speeds and an outdoor 414 environment. 415 416 Conclusion 417 This study demonstrated that running quietly is not directly associated with a lower 418 vGRF or vertical loading rate. However, when healthy male participants were asked 419 to intentionally run quietly, compared to their normal running, peak impact sound 420 amplitude, peak vGRF and vertical loading rate were reduced. This may have 421 important injury prevention implications for coaches, athletes and clinicians. 621-624 439