Concurrent Validity of Power From Three On-Water Rowing Instrumentation Systems and a Concept2 Ergometer

Abstract

Purpose: Instrumentation systems are increasingly used in rowing to measure training intensity and performance but have not been validated for measures of power. In this study, the concurrent validity of Peach PowerLine (six units), Nielsen-Kellerman EmPower (five units), Weba OarPowerMeter (three units), Concept2 model D ergometer (one unit), and a custom-built reference instrumentation system (Reference System; one unit) were investigated. Methods: Eight female and seven male rowers [age, 21 ± 2.5 years; rowing experience, 7.1 ± 2.6 years, mean ± standard deviation (SD)] performed a 30-s maximal test and a 7 × 4-min incremental test once per week for 5 weeks. Power per stroke was extracted concurrently from the Reference System (via chain force and velocity), the Concept2 itself, Weba (oar shaft-based), and either Peach or EmPower (oarlock-based). Differences from the Reference System in the mean (representing potential error) and the stroke-to-stroke variability (represented by its SD) of power per stroke for each stage and device, and between-unit differences, were estimated using general linear mixed modeling and interpreted using rejection of non-substantial and substantial hypotheses. Results: Potential error in mean power was decisively substantial for all devices (Concept2, -11 to -15%; Peach, -7.9 to -17%; EmPower, -32 to -48%; and Weba, -7.9 to -16%). Between-unit differences (as SD) in mean power lacked statistical precision but were substantial and consistent across stages (Peach, ∼5%; EmPower, ∼7%; and Weba, ∼2%). Most differences from the Reference System in stroke-to-stroke variability of power were possibly or likely trivial or small for Peach (-3.0 to -16%), and likely or decisively substantial for EmPower (9.7-57%), and mostly decisively substantial for Weba (61-139%) and the Concept2 (-28 to 177%). Conclusion: Potential negative error in mean power was evident for all devices and units, particularly EmPower. Stroke-to-stroke variation in power showed a lack of measurement sensitivity (apparent smoothing) that was minor for Peach but larger for the Concept2, whereas EmPower and Weba added random error. Peach is therefore recommended for measurement of mean and stroke power.

Keywords: Concept2; Nielsen-Kellerman EmPower; Peach PowerLine; Weba OarPowerMeter; between-unit differences; random error; systematic error; technical error of measurement.

FIGURE 1

Birds-eye view diagram (not drawn to scale) of Swingulator-system illustrating location of devices. Pin, point of oar rotation. Pulley 2 is attached to the oar, Pulleys 3 and 4 are located on the underside of the Swingulator framing. Dashed line represents the Concept2 chain and Swingulator cord which passes under the framing after Pulley 2. The black diamond near Pulley 1 indicates the anchor point of the Swingulator cord.

FIGURE 2

Custom Swingulator attachment with force transducer at Pulley 4.

FIGURE 3

Schematic of testing session protocol showing periods of rowing (rower icon), rest (pause icon), and when power was recorded from the five devices (lightning icon). Participants performed the same protocol in each of the five testing sessions, which were separated by 7 days.

FIGURE 4

Oarlock angle plotted against Concept2 chain position used to derive a, b, and c in Equation 1 (A); and the ratio of predicted-to-measured force plotted against oarlock angle used to derive the coefficients d, e, f, and g in Equation 4 (B). Dashed lines represent the fitted trendlines.

FIGURE 5

Free body diagram of Swingulator-system illustrating the location of the applied force (F_A), distance i, distance o, angle σ, and angle ϕ in Equation 3.

FIGURE 6

Power per stroke for each device during Stage 5 of two consecutive testing sessions by the same participant. Data for the Weba and Concept2 were recorded in every session but for reasons of clarity are not shown for the Weba (above) or the Concept2 (below).

FIGURE 7

Means of the mean (left) and SD (right) of power for each device in each stage for all the testing sessions. SD bars represent between-unit SD for the means and SD. The Reference System and the Concept2 have no SD bars, as only one unit was tested. SD bars on the right are omitted from some stages for Peach and EmPower, reflecting negative variance. Stage 0 represents the 30-s maximal test.