Objective The aim of this study was to investigate the cumulative effects of prolonged, intensive training and rapid weight loss on immunological parameters and antioxidation activity of elite male Taiwanese taekwondo athletes.
Design 16 Elite male taekwondo athletes (mean age, 21.6 (1.3) years; mean height, 173.7 (5.5) cm) volunteered to participate in this study. Beginning at 30 days before a national competition, saliva samples were obtained during a 7-week training, the competition and the postcompetition period. Levels of salivary IgA, cortisol, lactoferrin and free-radical scavenging activity were measured at 30-, 14-, 7- and 1-day precompetition and 1-, 7- and 19-day postcompetition. Body weight and body fat were also recorded.
Results The mean body weight was notably decreased during the week immediately before the competition. Results reveal that the levels of salivary IgA were differentially regulated during the training, competition and recovery period, while the salivary cortisol and lactoferrin concentrations and free-radical scavenging activity were not appreciably affected during the training and the competition period. Furthermore, the results of an upper respiratory tract infection incidence indicate that following the decreases of mucosal immunity, the risk of acquiring infection was significantly increased.
Conclusions Our results demonstrated that mucosal immunity in elite male taekwondo athletes is modulated by exercise and rapid weight reduction during the training, competition and recovery period. Cumulative effects of prolonged intensive training and rapid weight reduction suppressed mucosal immunity. Furthermore, because of the “open window” of impaired immunity during the precompetition period, the incidence of upper respiratory tract infection was significantly increased after the competition.
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Taekwondo (TKD) is a modern martial art that was inducted as an official Olympic sport at the 2000 Sydney Olympic Game. TKD is a high-speed, high-tension, full-contact combat sport. As a result, it consumes a large amount of energy during competition. Elite TKD athletes require sophisticated techniques, high aerobic and anaerobic capacities, and great muscular strength and endurance for successful performance.1 Therefore, the precompetition training programme for TKD athletes includes a series of intensified, vigorous physical exercises and technical/tactical trainings. Recent studies reported that elite athletes undertaking repeated, strenuous bouts of prolonged training are at an increased risk to infections, particularly the upper respiratory tract infections (URTIs).2,–,9 An “open window” of impaired immunity was observed, which lasts for 3–72 h following each bout of strenuous exercise.10 11
Like other combat sports, TKD is a weight-classified athletic contest where athletes are required to meet specific weight categories for competition. To compete at a lower weight category, a significant proportion of elite TKD athletes try to decrease their body weight for a short period before competitions.6 12 13 Rapid weight loss (RWL) methods employed by athletes include energy restriction, increased exercise load and dehydration.6 12,–,15 Previous researches have revealed that RWL during intensive training can have serious detrimental effects on various aspects of human physiology, especially the immune functions.4 14,–,19
Mucosal immunity constitutes the first line of defence against pathogen invasion.20 Salivary IgA (sIgA) prevents attachment of external pathogens and toxic molecules to mucosal surfaces and thus plays a key role in mucosal immunity.21 Studies demonstrated that the secretion of sIgA was significantly decreased during a prolonged training programme and the levels of sIgA were inversely correlated with the risk of URTI.22 23 In addition, Oliver et al24 reported that combined fluid and energy restriction for 48 h significantly decreased the sIgA secretion rate. Lactoferrin has been well recognised as an antimicrobial protein and plays important roles in host defence against respiratory infections.25,–,30 Previous studies showed that the plasma levels of stress hormones increased shortly after strenuous exercise. Stress hormones shift the type 1/type 2 balance towards a predominant type 2 response.4 31 32 Therefore, the exercise-induced increase in susceptibility to URTI has been attributed to the increased secretion of stress hormones, like cortisol. Human saliva is rich in antioxidants.33 The free-radical scavenging activity (FRSA) exerted by these salivary antioxidants can contribute significantly in the antioxidation activity by scavenging free radicals and thus preventing oxidative damage to cells and tissues.34,–,36 Recently, Atsumi et al37 demonstrated that physical activities and mental stresses can modulate the salivary FRSA. Therefore, it is interesting to examine whether the antioxidation activity provided by saliva is affected by intense training and RWL.
Although acute effects of strenuous exercise were reported by many studies, only a handful of studies have been conducted on cumulative effects of intensified training on elite athletes. Moreover, many studies reported the effects of exercise and/or weight reduction on immunity; however, there were no mentions about the physiological responses of elite TKD athletes to the combination of intensified training and rapid weight change during the training, competition and postcompetition period. The aim of this study was to investigate the cumulative effects of prolonged intensive training and rapid weight change on immunological parameters and oxidative stress of elite male TKD athletes. The physiological responses measured included body weight, body fat, incidence of URTI and levels of sIgA, cortisol, lactoferrin and FRSA.
Materials and methods
Sixteen male athletes from the National Taiwan Sport University TKD team volunteered to participate in this study. All participants had at least 8 years of professional TKD training, and most of them had won gold medals in the national TKD tournaments in Taiwan. Some participants even have won medals in the international TKD tournaments, including the World University TKD Championships and the Asian TKD Championships. Moreover, some of them were selected as members of the Chinese Taipei TKD Training Team for 2008 Beijing Olympic Game. Ethical approval was obtained from the Human Ethics Committee of the National Taiwan Sport University before the onset of this study. Written informed consent was obtained from all participants before study entry.
The body weight, body fat and per cent body fat were measured by the eight-electrode bioimpedance analyzer InBody 3.0 (Biospace, Seoul, Korea). Body height was measured in triplicate in a standing position and without shoes, using a stadiometer (Holtain, Crymych, Dyfed, UK) to the nearest 0.1 cm. The stadiometer was calibrated daily with a metal measuring tape for accuracy. Body mass index (BMI) was calculated by dividing the body weight (kg) by the square of height (m).
All participants participated in a 4-week precompetition training programme in preparation for a national TKD tournament in Taiwan. They were trained 4–6 h/day six times a week before competition. From −30 to −21 days, 70% of the training time was devoted to technique training and 30% to physical training. From −20 to −14 days, the participants spend 80% of the time on technique training and 20% on physical training. From −13 to −7 days, times spent on technique training and physical training were 90 and 10%, respectively. From −6 days to −1 day, 100% of the time was devoted to technique training. No training was given to the athletes the day after the competition. Afterwards, the participants spend approximately the same amount of time on technique training and physical training. From +2 to +7 days after competition, the participants were trained 2 h/day. From +8 to +19 days after the competition, the participants were subjected to a regular training programme and trained 4 h/day. Each technique training session includes basic techniques (ie, round house, axe, side, back and spin hook kicks and punch), simulated fighting techniques (ie, offensive attack, defensive counter-attack, rhythm-breaking and clinch scoring training models) and simulated matches. A physical training session includes running, jumping, pushing up and other aerobic activities.
Incidence of URTI
Incidence and duration of URTI was recorded during the entire study period. The participants were asked to fill out a health checklist each day. URTI was recorded when participants reported two or more flu symptoms, such as fever, headache, sore throat, sneezing, stuffy nose, nasal discharge, cough, malaise and chilliness, for at least two consecutive days.
Before the training session of the day, saliva samples were collected at 15:00, at least 2 h after meal, to minimise the circadian variations and meal time effects that have been demonstrated to cause alterations in salivary cortisol and immunoglobulin levels.38,–,40 Beginning at 30 days before the competition, saliva samples were obtained at 30-, 14-, 7- and 1-day precompetition and 1-, 7- and 19-day postcompetition. These time points are referred to as −30, −14, −7, −1, +1, +7 and +19 days, respectively. Before sample collection, each participant was asked to thoroughly rinse his mouth with sterile distilled water. The participants were asked to spit out the water to minimise possible contamination that could interfere with the analyses. Two millilitres of unstimulated whole-saliva specimens were then collected into sterile plastic containers and immediately stored at −80°C until use.
Total protein concentration in saliva was determined using the Bio-RAD protein assay kit (Bio-RAD, Hercules, California, USA). sIgA was measured using an ELISA kit as described previously.41 Briefly, 100 μl of saliva aliquots were assayed at a dilution of 1:500. An antihuman IgA (I-9889; Sigma, Poole, UK) was used as the primary antibody, and the secondary antibody was a horseradish peroxidase-conjugated antihuman IgA (A3062; Sigma). The assay was calibrated by reference to a standard curve prepared from human colostrum IgA (I-2636; Sigma). Salivary cortisol was assayed by using a commercial ELISA kit (DRG Instruments, Marburg, Germany). Salivary lactoferrin was measured by an ELISA. Saliva aliquots (100 μl) were assayed at a dilution of 1:2000. Sheep antihuman lactoferrin (ab36303; Abcam, Cambridge, UK) was used as the primary antibody, and rabbit antihuman lactoferrin (ab15811; Abcam) was used as the secondary antibody. The tertiary antibody was an alkaline phosphatase-conjugated goat antirabbit IgG (816122; ZYMED, South San Francisco, California, USA). The assay was calibrated by reference to a standard curve prepared from various dilutions of human lactoferrin (L0502; Sigma). All samples were measured in triplicate. Salivary FRSA was measured as described previously.37 In brief, 10 min after the addition and mixing of 20 μl of saliva to 1,1-diphenyl-2-picrylhydrazyl solution (0.2 mM dissolved in 40% ethanol), the absorbance at 540 nm was measured. FRSA was presented as the percentage of decreased 1,1-diphenyl-2-picrylhydrazyl compared with the control experiment without the addition of saliva and was calculated by the following formula:
whereas Ac and As represents the absorbance with the addition of phosphate-buffered saline and saliva samples, respectively.
All the assays in this study were performed in triplicate. The mean intra-assay coefficient of variation was 3% for sIgA, 4% for cortisol and 4% for lactoferrin.
All data are expressed as mean (SD). Statistical comparisons were analysed using repeated-measures analysis of variance. The significant difference between the values obtained at −1 day and other times was set at p<0.05, p<0.01 and p<0.001. The significant difference between the values obtained at −30 day and other times was set at p<0.05, p<0.01 and p<0.001.
The physical characteristics of the 16 elite male TKD athletes at the beginning (30 days before competition) of the study are summarised in table 1. The mean (SD) age of the athletes was 21.6 (1.3) years. The total training volume for the participants was 4–6 h/week during the precompetition training period. The mean body weights were 71.06 (10.16) and 71.44 (9.91) kg at −30 and −19 days, respectively. However, these were significantly decreased to 69.41 (9.16) kg at −1 day (fig 1A). Among these 16 participants, eight have at least 2 kg of weight reduction during the week before competition (data not shown). The body weight records reveal that elite male TKD athletes dramatically decreased their body weights shortly before the competition (fig 1A). The mean BMI was significantly decreased at 1 day before the competition (fig 1B). Body fat and body fat percentage were significantly increased after competition (fig 1C,D).
Incidence of URTI
The incidence of URTI is shown in fig 2. Infection rates were low (<10%) during the training period until 1 day before competition (−1 day; incidence, 4/16 (25%)). The incidence of URTI was significantly increased 1 week after the competition (+7 days; incidence, 10/16 (62.5%)) and remained high for at least 3 weeks (+19 days; incidence, 8/16 (50%)).
We observed that the sIgA levels measured at −14 days (fig 3A,B) were significantly increased compared with those measured at −30 days (fig 3A,B). However, this effect was clearly reversed at −7 days and −1 day (fig 3A,B). The sIgA levels measured at −7 days and −1 day were significantly lower than those measured at the beginning of the training programme (−30 days). In addition, when compared with the sIgA levels measured at −1 day, results reveal that the sIgA levels were gradually and persistently increased with time (fig 3A,B; +1, +7 and +19 days) after competition.
Salivary levels of other factors
Compared with 1 day before competition (fig 4A, −1 day), the mean salivary lactoferrin level was decreased at +1 day (p<0.05; fig 4A, +1 day). Other than that, the salivary lactoferrin levels were not significantly different between times (fig 4A,B). As shown in figs 5 and 6, the levels of salivary cortisol and FRSA were not significantly different between times.
The present study of highly trained male TKD athletes showed that their body weights were rapidly reduced during the week before the competition to meet specific weight categories for competition. We also observed that mucosal immunity in elite male TKD athletes is clearly modulated by exercise during the training, competition and recovery period. Furthermore, the results of URTI incidence indicate that following the decrease of mucosal immunity, the risk of acquiring infection was significantly increased.
Studies showed that a substantial number of TKD athletes reduced their body weight shortly before competitions.6 12 13 In addition, van Dijk et al13 reported that 28.2% of the 342 TKD athletes who participated the 2004 European Championships had a rapid weight gain within 1 day after the official weight-in. The data presented here also revealed that the mean body weight of the 16 participants was reduced significantly 1 day before the competition. Furthermore, 1 day after the competition, the mean body weight was increased significantly (fig 1). Although effects of rapid weight changes on athletes' performance are still discussed controversially,13 14 the suboptimal nutritional intake and repeated weight cycling before and after each important competition may cause potential detrimental effects on the health of elite TKD athletes.42 43
Two weeks after the start of training (−14 day), sIgA levels of elite male TKD athletes were significantly increased comparing with those measured at −30 day (fig 3). This result reveals that the training performed during the first 2 weeks actually enhanced the mucosal immunity of elite male TKD athletes. It is in good agreement with previous studies that proper amount of exercise can stimulate the immune response.44 Apparently, highly trained elite male TKD athletes are adapted to a higher amount of training load as applied in the current study without having adverse effects on mucosal immunity in the first 2 weeks.
As shown in fig 1A, a large amount of weight loss was observed during −14 days to −1 day. Moreover, data show that a significant proportion of elite TKD athletes (50%) decreased their body weight (≥2 kg) during the week before the competition (fig 1A and data not shown). At the same time, we also observed that the sIgA levels measured at −7 days and −1 day were significantly reduced compared with those measured at −30 days (fig 3A,B). These results indicate that the mucosal immunity of the participants was suppressed during this period. Because of the upcoming national competition, the combination of cumulative effects of prolonged intensive training, psychological stress and the weight loss programme conducted by the participants might have caused immune suppression. Previous studies suggest that intensive training plus RWL may have detrimental effects on human health, especially on immune functions.4 14,–,18 Our results provide further evidence that cumulative effects of prolonged intensive training and/or RWL exert adverse effects on mucosal immunity in elite male TKD athletes.
After the competition, the sIgA levels measured at +1 day were significantly higher than those measured at −1 day and were not statistically different from those measured at −30 days (fig 3). Our data suggest that when the participants were relieved from stress arising from intensive training and weight reduction programme, the suppressed mucosal immunity was rapidly restored. However, because of the “open window” of impaired immunity during the precompetition period, the incidence of URTI was significantly increased after the competition (fig 2; 62.5% at +7 days and 50% at +19 days). Our results is in good agreement with those of Neville et al45, who reported that the sIgA levels were significantly reduced 3 weeks before athletes' acquiring URTI. The elevated secretion of sIgA observed at +7 and +19 days (fig 3) may be due to the immune response to respiratory infection.
In this study, although the salivary lactoferrin levels measured at +1 day were lower than those measured at −1 day (p<0.05; fig 4A), we observed that the secretion of salivary lactoferrin was not significantly modulated during the entire study period. Similarly, the levels of salivary cortisol were also not significantly different between times (fig 5). Although the levels of cortisol are expected to be higher before the competition because of the increases of stress, a number of studies suggested that elite athletes are more adept competitors and thus they tend to manage stress more effectively.46 47 The results of this study are in line with this notion, but more research should be conducted to further investigate the underlying mechanisms. As shown in fig 6, the levels of FRSA were not significantly modulated between times. Although it has been shown by Atsumi et al37 that the levels of FRSA were affected by various physical and mental activities, significant variations in FRSA were not observed in elite TKD athletes during the study period. As we are investigating the cumulative effects of prolonged intensive training and RWL, saliva samples were collected after resting and before the daily training programme. Most studies that observed modulated levels of FRSA and lactoferrin collected samples shortly after training.25 37 Although we are unable to exclude the possibility that levels of salivary lactoferrin and FRSA are associated with physiological changes induced by other stressful situations, available data suggest that levels of salivary lactoferrin and FRSA may not be directly associated with the prolonged intensive training and/or RWL in elite male TKD athletes.
In summary, to our knowledge, this study is the first to explore that the sIgA levels were differentially modulated by exercise and rapid weight reduction during the training, competition and recovery period in elite male TKD athletes. We suggest that sIgA can be used as an ideal indicator for assessing the physical stress in elite male TKD athletes. On the other hand, it will be also interesting to know how the physiological parameters of female TKD athletes are affected by these stressful situations. The current study intended to use a noninvasive method to explore the relationship between intensive training/RWL and physiological responses of elite male TKD athletes. In the future, a set of more complete serum immunological tests will be carried out on elite male and female TKD athletes to study a wide range of immunological responses towards intense training and/or RWL.
The authors warmly thank the coach, Yong-Sung Ha, and all the TKD athletes for their patience and participation in this study. This study was supported by NSC 97-2320-B-028-001-MY3 granted by the National Science Council, Republic of China, and 97DG0008 granted by the National Taiwan Sport University. We thank Pei-Yu Shih for the expert technical assistance.
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Human Ethics Committee of the National Taiwan Sport University.
Provenance and peer review Not commissioned; externally peer reviewed.
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