Reliability and Validity of Running Cadence and Stance Time Derived from Instrumented Wireless Earbuds

Abstract

Instrumented earbuds equipped with accelerometers were developed in response to limitations of currently used running wearables regarding sensor location and feedback delivery. The aim of this study was to assess test–retest reliability, face validity and concurrent validity for cadence and stance time in running. Participants wore an instrumented earbud (new method) while running on a treadmill with embedded force-plates (well-established method). They ran at a range of running speeds and performed several instructed head movements while running at a comfortable speed. Cadence and stance time were derived from raw earbud and force-plate data and compared within and between both methods using t-tests, ICC and Bland–Altman analysis. Test–retest reliability was good-to-excellent for both methods. Face validity was demonstrated for both methods, with cadence and stance time varying with speed in to-be-expected directions. Between-methods agreement for cadence was excellent for all speeds and instructed head movements. For stance time, agreement was good-to-excellent for all conditions, except while running at 13 km/h and shaking the head. Overall, the measurement of cadence and stance time using an accelerometer embedded in a wireless earbud showed good test–retest reliability, face validity and concurrent validity, indicating that instrumented earbuds may provide a promising alternative to currently used wearable systems.

A Comparison of a Novel Stretchable Smart Patch for Measuring Runner’s Step Rates with Existing Measuring Technologies

“…With slow running in place, the mean bias was less than 1 step/min (between −0.4 and 0.2 steps/min) for all four devices-lowest (0.1 steps/min) for the Qualisys motion capture system and highest (−0.4 steps/min) for the Garmin Running Pod. In their investigation of the validity of measuring running cadence (step rate) with earbuds, Nijs et al [20] observed a maximal mean cadence of 181 steps/min, which is comparable to our slow rate of running in place (179 steps/min). In their study, the mean bias between the values provided by the force plates and the earbuds was 1.3 steps/min, which is higher than the mean bias for any of the devices evaluated here.…”

Wearables for Running Gait Analysis: A Systematic Review

“…Eight studies combined controlled and self-selected speeds [ 35 , 62 , 76 , 116 , 118 , 127 , 132 , 135 ]. For example, Giandolini et al examined participants at 10, 12, 14 (female) and 16 km/h (male), maximum aerobic speed and participant’s preferred speed [ 116 ].…”

“…Self-selected speeds were used in 21 studies, with a range from jogging [ 136 ] to maximum effort/sprint [ 86 , 99 , 100 , 102 , 104 , 105 , 129 , 133 ]. An additional five studies combined controlled and self-selected speeds [ 62 , 76 , 116 , 127 , 135 ]. One study did not comment on the treadmill speeds used [ 93 ].…”

“…The most common inertial wearable locations were the tibia (n = 42), mostly located at the distal anteromedial aspect; shoe (n = 38), varying locations of dorsal aspect/shoelaces/ instep, cavity, ankle, heel and fifth metatarsal; and lower back [including sacrum] (n = 24). One study used instrumented earbuds [135], and a further four studies placed wearables on the sternum/chest and these were always in combination with a lower body sensor placement [19,20,89,93]. In the seven studies that used wearables on the upper back, five studies placed the sensor in a harness/vest [21,38,105,121,129,130,133].…”

“…Within reliability studies, ten analysed test-re-test reliability in a single day (i.e. two sessions in 1 day) [98,99,103,104,106,110,130,[134][135][136] and 11 studies performed a test-re-test analysis on different days [34,47,87,117,120,122,138,140,142,144,149]. Those studies that assessed running gait on different days separated testing by a minimum of 24 h [34,140,144], and repeated testing within 1 week [120,149], 2 weeks [47,87] or 1 month [117,142], with one study repeating testing at 1 week and 6 months [138] (Table 2 of the ESM).…”