Evaluation of the laboratory based football-specific treadmill protocol and the effect of high ambient temperature on physiological responses

Authors Avatar

Evaluation of the laboratory based football-specific treadmill protocol and the effect of high ambient temperature on physiological responses.

Introduction

The physiological demand in soccer is a significant factor that determines performance. In a match, players are required to perform different types of exercise, from walking, jogging, sprinting, jumping, to tackling, and the intensity varies accordingly (Bangsbo, 1994). On average, an outfield player has to cover 8-12 km during the course of a match (Reilly, 1996). Results from Reilly et al. (2000) indicated that a soccer player has to run with effort every 90 seconds and input high-intensity efforts every 30 seconds. Hence, the ability to endure and exercise with high power output becomes very important. Whether or not a player could sustain this high work rate depends on the body’s energy production mechanisms. Meyhew and Wenger (1985) found that 88% of a game is aerobic in nature while Bangsbo (1997) argued that anaerobic energy production is vital for intense activities such as sprinting and jumping. One major problem faced by scientists, when studying the function of these mechanisms during a game, was that the measurement of certain variables such as oxygen uptake (VO2) would interfere with match play and only small parts of a match could be analyzed (Bangsbo, 1994). As a result, several laboratory-based exercise protocols were developed to measure metabolic and physiological responses in intermittent exercise (Holmyard et al., 1988; Nevill et al., 1995). However, they are generally too uniform to represent the complex nature of a soccer game. Drust et al. (2000) went on to develop a protocol that includes variations in the intensity and duration of exercise as well as a more irregular resting period to simulate the intermittent trait of a soccer game. This soccer-specific treadmill protocol is more representative of match-play work rates; it allows one to examine physiological responses and quantify physiological performance in a soccer game. The aim of the present paper is to critically evaluate this laboratory based football-specific treadmill protocol as a simulation of football match-play and further examine the effect of acute heat on physiological responses.


Method

Subject

Six physically active male soccer players were recruited. The characteristics of the players are shown in Table 1. The participants were tested in post-absorptive state, after an overnight fast, with no vigorous exercise or any alcohol consumption in the 24 hours prior to testing. Each subject was tested at the same time of the day to prevent the effects of circadian variation on the variables measured (Reilly and Brooks, 1986, as cited in Drust et al., 2000). They were fully informed about the aims and the procedures of the study and signed an informed consent form. The study obeyed the laws of the country and was approved by the Ethical Committee of Liverpool John Moores University.

Table 1. Physical characteristics of the participants (n = 6; mean ± s).

Design

The participants visited the laboratory on two separate occasions, which was separated by a week time. The intermittent exercise protocols were completed under two different environmental conditions. In the first visit, the laboratory temperature and relative humidity were set at 18˚C and 50% respectively. In the second visit, the laboratory temperature was raised to 30˚C while the humidity remained the same. During the course of the protocol, heart rate (HR), oxygen uptake (VO2), core temperature, blood lactate, thermal comfort (TC), and rate of perceived exertion (RPE) were measured at specific time intervals.

Procedures

The soccer-specific intermittent protocol was performed on a motorized treadmill (HP Cosmos, Nussdorf, Germany). Heart rate monitor (Polar 610i, Kempele, Finland) was used to record heart rate every 5 minutes. Oxygen uptake was measured by a spiroergometric device (MetaLyzer 3B, Cortex Biophysic GmbH, Leipzig, Germany) during 5-10, 20-25, 35-40, 50-55, 65-70, 80-85 min. Core temperature was measured using a rectal probe placed 10 cm beyond the anal sphincter (ELLAB, Denmark) and was monitored every 5 minutes. Fingertip capillary blood samples were obtained every 15 minutes and analyzed immediately to represent the overall blood lactate concentration (Lactate Pro, Arkray, Kyoto, Japan). The Borg scale (1970, as cited in Drust et al., 2000) was used to provide a rating of perceived exertion (RPE) reported by each subject every 5 minutes. Thermal comfort was also reported at the same time in a scale of 1 to 10 with 10 being the hottest. After the test, all subjects were asked to have a post-exercise muscle temperature measured. They were then allowed to shower, try, and nude body mass was obtained afterwards. At the end, they were free to re-hydrate and refuel.

Join now!

Soccer-specific protocol

The soccer-specific intermittent protocol (see Fig. 1) was designed by Drust et al. (2000). The treadmill speed follows the observation by Van Gool et al. (1988, as cited in Drust et al., 2000) for specific movements; the speed for walking, jogging, cruising, and sprinting was 6 km/h, 12 km/h, 15 km/h, and 21 km/h respectively. Duration of each bout was determined by matching the percent total time of each movement with the data collected by Reilly and Thomas (1976) (see Fig. 2). Static recovery periods were also included, in which participants remained stationary on ...

This is a preview of the whole essay