Authors' Response : The Journal of Strength & Conditioning Research

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Manuscript Clarification

Authors' Response

Burr, Jamie F.; Aubry, Rachel L.; Powers, Geoff A.

Journal of Strength and Conditioning Research 32(12):p e62, December 2018. | DOI: 10.1519/JSC.0000000000002893
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Authors' Response:

We thank the employees from Stryd for their interest in our article and are happy to address their points raised.

  • Surface: It is correct that different intervals were used indoors and outdoors when comparing the O2 cost of running between a treadmill and world class track, but the sampling period was identical. Indoors, desired treadmill speed was imputed, and the athlete simply needed to accelerate and maintain this pace for 2 minutes. Outdoors, the athlete had to be paced to ensure accurate velocity, and thus, additional time was provided to ensure that the minimal pacing error was included. The lag in O2 kinetics was small because successive stages merely increased from the slightly slower one which preceded. The reference offered to support this because an insufficient time refers specifically to the transition from rest, which differs greatly. We would expect that the design team is glad that kinetics do not lag for such an extended period, for if they did, the reflection of metabolic demand by a real-time accelerometer/speed-based device such as the Stryd would be incorrect for a matter of minutes with each and every change in pace. In any event, we confirm the achievement of steady state during measurement at all stages.
  • Speed: As is stated in the article, we elected to divide both power and oxygen consumption by speed to allow for the presentation of combined data and to avoid presenting numerous subsets with low statistical power. We believe we were quite transparent in highlighting our methods/presenting our results and regret if “several readers” mistook the meaning of these data. If we equally remove the influence of speed on 2 variables that are linearly related to speed, then the relationship of those 2 variables to each other should not differ greatly. Indeed, when non-normalized “power” and are correlated, relationships remain of “moderate” strength (r = 0.3–0.5). Irrespective of the strength of correlational data, we have addressed the changes in non-normalized “power” and in Table 2, and it is apparent that the changes observed in with increasing speed were not reflected in “power.”
  • Subject: Data were not aggregated by subject; it was aggregated across groups to present the relationship (or differences) between oxygen consumption and “power” measured simultaneously on the same person with differing exposures.

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