Acute physiological, biomechanical, and perceptual responses of runners wearing downward-curved carbon fiber insoles

Abstract

In a randomized controlled cross-over study ten male runners (26.7 ± 4.9 years; recent 5-km time: 18:37 ± 1:07 min:s) performed an incremental treadmill test (ITT) and a 3-km time trial (3-km TT) on a treadmill while wearing either carbon fiber insoles with downwards curvature or insoles made of butyl rubber (control condition) in light road racing shoes (Saucony Fastwitch 9). Oxygen uptake, respiratory exchange ratio, heart rate, blood lactate concentration, stride frequency, stride length and time to exhaustion were assessed during ITT. After ITT, all runners rated their perceived exertion, perceived shoe comfort and perceived shoe performance. Running time, heart rate, blood lactate levels, stride frequency and stride length were recorded during, and shoe comfort and shoe performance after, the 3-km TT. All parameters obtained during or after the ITT did not differ between the two conditions [range: p = 0.188 to 0.948 (alpha value: 0.05); Cohen's d = 0.021 to 0.479] despite the rating of shoe comfort showing better scores for the control insoles (p = 0.001; d = -1.646). All parameters during and after the 3-km TT showed no differences (p = 0.200 to 1.000; d = 0.000 to 0.501) between both conditions except for shoe comfort showing better scores for control insoles (p = 0.017; d = -0.919). Running with carbon fiber insoles with downwards curvature did not change running performance or any submaximal or maximal physiological or biomechanical parameter and perceived exertion compared to control condition. Shoe comfort is impaired while running with carbon fiber insoles. Wearing carbon fiber insoles with downwards curvature during treadmill running is not beneficial when compared to running with control insoles.

Keywords: footwear; running economy; running performance; running shoes; shoe technology.

Figure 1

Saucony fastwitch 9 used in the study during all incremental treadmill tests and all 3-km time trials.

Figure 2

Downwards curved carbon insole (A) footwear used in this study in the three-point bending test apparatus (B) force deformation curves of the no insole and carbon insole condition (C) note the offset in force values resulting from the downwards curved shape of the insole. Average bending stiffness values between 5 mm and 6 mm deformation (D).

Figure 3

(A) time to exhaustion; (B) shoe comfort; (C) shoe performance of the 10 runners during incremental treadmill testing. The bar represents the mean values of 10 runners. Circles joined by lines represent the individual data of each runner for carbon fiber and control insoles.

Figure 4

(A) in the 3-km TT; (B) mean heart rate during the 3-km TT; (C) rating of perceived exertion during the 3-km TT of the ten runners. The bars represent mean values of the 10 runners. The circles joined by lines represent individual data of each runner.

Figure 5

(A) stride frequency during 3-km TT; (B) stride length during 3-km TT in the ten runners. The bars represent mean values of the ten runners. Circles joined by lines represent individual data of each runner.

Figure 6

(A) shoe comfort; and (B) shoe performance during 3-km TT in the ten runners. The bars represent mean values of 10 runners. Circles joined by lines represent individual data of each runner.