Validity of the Wahoo KICKR Power Trainer and Reliability of a 4 km Cycle Time Trial

Emma K Zadow, James W Fell, Stuart T Smith, Cecilia M Shing


Purpose: To assess the validity of power and the reliability of a 4 km cycle time trial (TT) using the Wahoo KICKR Power Trainer.

Methods: The Wahoo KICKR power output was assessed using a dynamic calibration rig (DCR) over power outputs of 100-600 W at cadences of 80, 90 and 100 rpm. Twelve trained male cyclists (mean ± SD; age: 34.0 ± 6.5 years, height: 178.4 ± 6.2 cm, body mass: 76.8 ± 9.6 kg) completed three 4 km TTs on the Wahoo KICKR, each separated by a minimum of two and a maximum of three days. Mean power (W), cadence (rpm), speed (km.h-1), heart rate (bpm) and total time (s) were recorded for each TT while ratings of effort (0-10) and sessional ratings of perceived exertion (6-20) were collected immediately and 10 mins post each TT.

Results: Bias for differences in power (%) recorded by the Wahoo KICKR to the DCR was 0.8% (95%LOA -4.0- 5.6%) (Figure 1). Average ICC between trials (2-1, 3-2, 3-1) for power was 0.95 (95%CI 0.89-0.98), cadence 0.80 (95 %CI 0.60- 0.92), speed 0.70 (95%CI 0.46- 0.88), heart rate 0.93 (95%CI 0.85- 0.98) and total time 0.75 (95%CI 0.53-0.90). Coefficient of variation was 2.9%, 4.5%, 3.7%, 1.5%, 3.6% for power, cadence, speed, heart rate and total time, respectively (Table 2).

Results: sIgA concentrations (μ ٰ̄) before and after the treadmill were [mean 595, s = 64.6 and mean 841, s = 76.3] and before and after the bike were [mean 593.9, s = 51.1 and 778.8 s = 99.3]. sIgA secretion rates (μg.min ٰ̄) before and after the treadmill were [mean 396.2, s = 73.7 and 223 s = 99.6] and before and after the bike were [mean 284.1, s = 74.3 and 216.6, s = 29.5]. Saliva flow rates (μl.min ٰ̄) before and after the treadmill were [mean 657.8, s = 92.2 and 289.3, s = 56.6] and before and after the bike were [mean 487.2, s = 123.3 and 319.5, s = 66.5]. The results indicated that sIgA secretion rate (P < 0.028) and saliva flow rate (P < 0.01) were significantly decreased following the 2 hour treadmill protocol but not the 2 hour bike protocol. sIgA concentration was also significantly elevated following the treadmill (P < 0.01), with no significant increase following the bike protocol.

Conclusion: These results suggest that when compared to a DCR, the Wahoo KICKR Power Trainer displays a small mean bias across all measures of power, with caution to be applied at the lower ranges of power output (<200 W). When completed on the Wahoo KICKR Power Trainer, a 4 km TT in trained cyclists is highly reproducible.

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