Subjects and study design

Five male regional level taekwondo athletes (black or red and black striped belt; degree: at least 1^st Dan) who belong to the light weight categories (range: -54 up to -68 kg) participated in this study. The anthropometric data of the participants were as follows (Mean ± SD): age: 17.40 ± 1.67 years, body weight: 57.77 ± 7.04 kg, height: 170.30 ± 4.91 cm. Average endurance training volume was between 10–12 h per week and all participants exhibited individual experiences in body weight loss. The athletes did not take any medication during all procedure and did without alcohol and nicotine consumption for at least 24 h before the study.

The study consisted of two phases, a control phase without body weight reduction and a RWR phase in which the participants were told to reduce body weight by 5% during 3½ days according to previous studies [4–8]. Due to study organization to display real weigh-in time, the duration of RWR was modified (3½ days instead of 4 days). Weigh-in was scheduled at the fourth day of RWR [4, 7, 8]. During RWR, weight loss was conducted by individual methods of athletes and included fasting, decreased fluid intake, dehydration trough sauna sessions, increased training intensity/volume. Nutritional intake and activity report were shown in Table 1 [4, 8].

Data are present as mean ± SD of n = 5.

A two day recovery phase was scheduled between control and RWR period. Each study phase consisted of a pretest, weigh-in test after 3½ days and a competition day after a 16 h recovery time (usual method of weight recovery) (Fig 1). During 16 h recovery, athletes recovered their body water and carbohydrate storage.

The study consisted of a control phase without body weight reduction and a rapid weight reduction (RWR) phase. A two day recovery phase was scheduled between control and RWR period. The participants were told to reduce body weight by 5% during 3 ½ days. Each phase consisted of a pretest, weigh-in test after 3½ days and a simulated competition day after 16 h recovery time. On SCD, each athlete executed three TKD simulation matches (SMs) with a 1 h rest between SMs. Blood sampling was conducted at pretest, weigh-in test, SCD and after 3^rd SM of both phases.

On the simulated competition days (SCD), each athlete executed three TKD simulation matches (SMs; 1^stSM, 2^ndSM and 3^rdSM) with a 1 h rest between SMs. According to the guidelines of G1 or G2 (ranking point chart by grade) World Taekwondo (WT) tournaments in Europe, the period of rest between of matches should approximately last 30 min– 2 h. Thus, a mean of resting time of 1 h between matches was chosen in the study. However, these durations depend fully on number of participants (athletes) and organization of tournaments.

In each SM, one test athlete fought against a sparring partner; an opponent who was not a test athlete. The fight displayed real competition conditions: The same athletes fought against each other in both phases (control and RWR).

In accordance with the World Taekwondo rules, each SMs consisted of three rounds and 2 min each, with a resting interval of 1 min in-between. During resting intervals, subjects remained in a seated position (passive). Each match conducted within an official area (8 x 8m). A gas analyzer was placed on the back of the competing athlete and no attack to this area was allowed. The sparring partner remained in a passive position during SM such as blocking and fake motion with the intensive steps. Electronic body protectors and headgear were not used because they would interfere with the spirometry [33–35].