The relationship between running velocity and the energy cost of turning during running

Abstract

Ball game players frequently perform changes of direction (CODs) while running; however, there has been little research on the physiological impact of CODs. In particular, the effect of running velocity on the physiological and energy demands of CODs while running has not been clearly determined. The purpose of this study was to examine the relationship between running velocity and the energy cost of a 180°COD and to quantify the energy cost of a 180°COD. Nine male university students (aged 18-22 years) participated in the study. Five shuttle trials were performed in which the subjects were required to run at different velocities (3, 4, 5, 6, 7, and 8 km/h). Each trial consisted of four stages with different turn frequencies (13, 18, 24 and 30 per minute), and each stage lasted 3 minutes. Oxygen consumption was measured during the trial. The energy cost of a COD significantly increased with running velocity (except between 7 and 8 km/h, p = 0.110). The relationship between running velocity and the energy cost of a 180°COD is best represented by a quadratic function (y = -0.012+0.066x +0.008x(2), [r = 0.994, p = 0.001]), but is also well represented by a linear (y = -0.228+0.152x, [r = 0.991, p<0.001]). These data suggest that even low running velocities have relatively high physiological demands if the COD frequency increases, and that running velocities affect the physiological demands of CODs. These results also showed that the energy expenditure of COD can be evaluated using only two data points. These results may be useful for estimating the energy expenditure of players during a match and designing shuttle exercise training programs.

Figure 1

(a) Shuttle exercise protocol. Each stage lasted 3 min, with a 1-min rest between stages. COD frequencies of each stage were 13, 18, 24 and 30 CODs per minute. (b) EE of a COD while running. Extra energy expenditure occurs every time a COD is performed. The figure shows the estimation for all turn frequencies over 10 seconds. COD, change of direction; EE, energy expenditure.

Figure 2. Comparison of physiological responses and RPE while running at different velocities.

Relationship between turn frequency and oxygen consumption (A), heart rate (B), and RPE (C), while running at different velocities. HR, heart rate; RPE, rating of perceived exertion; VO_2, gross oxygen consumption.

Figure 3. Relationship between running velocities and energy cost of a turn.

Values are averages. The relationship was expressed by both an approximate quadratic (r = 0.994, p = 0.001, solid line) and a linear model (r = 0.991, p<0.001, dashed line).

Figure 4. Relationship between actual and estimated running VO₂ at different running velocities.

The VO₂ of straight running and the intercept of the linear regression VO₂ at 6 different running velocities (3–8 km/h) were significantly correlated (r = 0.966, p = 0.002). VO₂, gross oxygen consumption.

Figure 5. Comparison of turn cost for different data points.

There was strong correlation (r = 0.99994, p<0.00001) between the slopes of regression lines drawn using two data points and five data points to evaluate the energy cost of a COD. The slope of the regression line of gross VO₂ and the graded COD frequency test indicates the energy cost of a COD while running. COD, change of direction; VO₂, gross oxygen consumption.