Karate is a martial art of Japanese origin, attack and defense using the arms and legs [1] [2]. Very popular sport, the goal of its practice is to impose itself on the other by carrying out a decisive action (ippon or more advantage) while striking in a vital point or making give up. Karate was a demonstration sport in the Olympics Games before becoming year official sport in the 2020 Olympics Games in Tokyo. The time-motion analysis and heart rate and blood lactate responses to the fights suggested that karate competition places high demands on one short-term anaerobic power and ability to recovery [3]. The research of performance for a practitioner is characterized by complex problems. Thus, the increasing knowledge of the physiological phenomena brought into play in the high level sporting preparation makes it possible to better define its effects and to control its progression. The organized competition of weight category rests on fights of min duration each one; the surface of competition is 64 m² (8 m on side). Consequently, the techniques used with the maximum of effectiveness and power ask for training of often high intensity, including running, endurance and muscular resistance exercises, series of kicks techniques, strike blows techniques of fist and edge of hand. For good to involve itself, one thus makes recourse mainly to the anaerobic metabolic way, but also to the aerobic way [2]. It is in this context that several studies have been undertaken in karate black belt athletes for more than 20 years [4] [5] [6] [7] [8]. In Congo, the studies devoted to the haemodynamic responses to exercise at the martial arts practice are rare [9] and the heart rate observed during meetings in the majority of the competitive sports is always very high [10]. In the margin of these observations, the medical follow-up of sportsmen taking share with the tests registered with the official calendar of the competitions of the Congolese Karate Federation is irregular, even specific. It is to fill this gap that we carried out a metabolic and cardiovascular follow-up in the karate athletes, during the preparation of the national championship. Thus, this exploratory work evaluates haemodynamic and blood lactate concentrations responses during the training and the fights in Congolese karate athletes according to the age category. The objectives of this study were: 1) to evaluate and analyze peak aerobic power (PAP) and maximum oxygen consumption (VO₂ max) of Congolese karate athletes; 2) to determine their recovery capacity, following a submaximal exercise; 3) to evaluate and analyze the variations of heart rate, blood pressure and blood lactate concentrations throughout fights. The interest of this study is to be able to draw the conclusions on level of regulation and control of training of karate in the African environment.

This study shows mainly that the specific karate exercises and the simulated competition significantly affect the evolution of HR, SBP and [La] concentrations in the athlete. Data obtained reveal that age, weight and height of our subjects (Table 1) are comparable with those reported by the literature in subjects involved to the martial arts [15] [16] [17]. However, our values (height, PAP and VO₂ max) are lower than those of taekwondo athletes reported by Bouhlel et al.

[18]. Congolese karate athlete is also characterized by a moderate recovery capacity with an mean RI value of 6.1. In our work, we used the Ruffier test to evaluate cardiovascular recovery before the series of the measurements taken at the time of the fights. Several factors explain the choice of this test among several tests available (Trip hammer test, Flack test, Systolic Tension Time, …).

It is about a dynamic and submaximal test a minima. Its total energy cost in 45 s estimated at 27.8 ± 1.95 ml STPD/kg, cardiac cost at 101 beats (60 to 144) and oxygen debt at 22.2 ± 5 ml STPD/kg [12]. Ruffier test allows, in current medical practice, to detect in sensitive populations blood pressure anomalies (SBP value higher than 280 mmHg), disorders of rhythm (passage in auricular fibrillation, or tachysystolic auricular) and anginous pains or an honest know-shift of the ST segment. However, duration of test (45 s) and its intensity are major factors which influence recovery, but they are not only. The physical form, food ingestion (post-prandial thermogenesis), familiarity of subjects with the procedures of evaluation, variations of body temperature, catecholamines concentrations, metabolic cost of the use of lactates and substrates, are as many factors which can modify not only HR, but also oxygen uptake. It is cavity that at the time of a muscular exercise, it is very difficult to control the whole of parameters; but we could assure us that each subject consumed neither alcohol, nor cafeine or other substances before Ruffier test and that its sleep was good the night preceding the test. Moreover, we adopted a rhythm of inflections-extensions of legs, compatible with an activity with lactic anaerobic dominant. This protocol made it possible to raise the HR at the end of the test between 110 - 140 bpm and authorized raised capacities for work, likely not to modify the lactate rate. That undoubtedly explains the good tolerance of exercise observed at our subjects, thanks to a spreading out of the cardiorespiratory constraints over one limited duration. The use of cardiofrequencemeter for the monitoring of HR in our study which can be discussed, achieves the unanimity nowadays because it is a reliable tool for assessment of physical activity intensity in trained athletes and older people who are trying to reduce risk factors for coronary heart disease through exercise [19].

Thus, the adaptation slower to the recovery of our karate athletes testifies to an increase in peripheral resistances, accused in the opposition to the modifications induced by physical exercise. Moreover, it is known that values of the relaxation time differ according to capacities from adaptation in hot medium surrounding [20], one characteristic of our environment during study where the temperatures of ambient air bordered 33˚C. Thus, at these temperatures the time of retardation is lengthened at the less adapted subjects, and the speed with which the restoration of the cardiac function is carried out towards values at rest is lengthened. The exposure of the body to heat then modifies the dynamics of mechanisms of cardiovascular adjustment during post-exercise recovery. However, evaluation of recovery capacity in the sportsman is not sufficient to predict the good physical condition, as specified by the studies of Packa-Tchissambou et al. [21], Vandewalle et al. [22].

Our work also highlighted the superiority of our HR values in comparison to those noted by MassambaMiabaou et al. [23] during African Games 2015 in karate athletes, 62.7 bpm and taekwondo athletes, 61.3 bpm, Moulongo et al. [9] in Congolese judo athletes, 64.5 bpm, and Artioli et al. [24] in Kung Fu athletes, 59.2 bpm. HR values at rest of our subjects (Table 2) were 76.2 ± 9.4 bpm for seniors and 72.7 ± 11.3 bpm for juniors, as variation of 4.9% between two age groups being no significant. Higher values are reported by the literature in sedentary congolese subjects [25] [26], 80.2 bpm and 79.5 bpm respectively. A reduction in HR values at rest is also observed in other experiments. In those brought back by Alexander et al. [27] in the professional football players, HR at rest decreases by a beat per minute, by week of training. The more one is involved, the more HR at rest drops. According to Chatard [28], HR at rest in the individuals who involve themselves regularly is often lower than 50 bpm (effects on sympathetic nerve tonicity), whereas the usual values at the sedentary subjects are higher than 60 bpm. Indeed, sinusal bradycardia meets with higher frequency in sporting population than in sedentary population. Its origin is allotted partly to vagal hypertonicity as can develop it the endurance sport, but a genetic factor predisposing seems necessary. Bradycardia is indeed far from being systematic as show it the following statistics. For Camus [29], out of 1000 sportsmen HR is 65 bpm in men and 75 bpm among women, all confused sports; the variations show HR value in men at 63.5 bpm in athletics, 62.5 bpm in cycling for example, against 70.7 bpm in tennis and 71.2 bpm in the sportsmen practising several sports. In the male athletes, HR varies from 52 to 74 bpm, and in tennis players from 60 to 81 bpm. For Venerando [30], mean HR values in cyclists were 53 bpm and 71 bpm in no sportsmen; values vary from 47 to 60 bpm in cyclists and from 60 to 81 bpm among sedentaries, which confirms the genetic disparity. The bradycardias towards 32, 34 bpm quoted with predilection by sporting press are very rare. They are not obligatorily an unquestionable sign of sporting value. Moreover, vagal origin of this bradycardia is confirmed by disorders of sino-auricular and auriculo-ventricular conduction which are sometimes observed. The theory of Reindell [31] making increase in the volume of the heart the cause of deceleration of the rhythm cannot thus be retained, because bradycardia precedes hypertrophy. It is banal, in addition to observe clearly a PR space above 0.17 s reaching 0.24 s for moderate bradycardia of 60 bpm. Even if we did not study the electrocardiogram of our sportsmen, this fact signs two sinusal and nodal components of ascribable sporting bradycardia to the action of two pneumogastric ones, the right acting preferentially on the node of Keith and Flack, it left on the node of Tawara. However, it is excluded only our high HR values at rest compared to those brought back by the authors quote previously, undoubtedly seem to be associated the bad management of training by the trainers in Congolese context (low volume of training, amateur status of Congolese karate athlete, low lifestyle).

In addition, our data show that the distribution of the blood pressure values at rest (Table 2) does not revealed blood pressure anomalies. Indeed, SBP and DBP mean values at rest, 117.4 mmHg and 87.8 mmHg, are close to those reported in a former study in judo athletes [9], 120.0 ± 1.5 mmHg. The tiny variations observed are to be registered with a cardiac adaptation to the muscular exercise, particularly to ventricular hypertrophy (not objectified in our study). Indeed, the cardiac response to exercise represents the integration of efforts of tachycardia, of sympathetic nerve stimulation of the mechanism of Franck-Starling himself related to the increase in the venous return. De Plaen and Detry [32] finds values of 120.4 ± 1.1 mmHg/82.6 ± 2.3 mmHg for 108 karate athletes aged to 25 - 34 years. Meckel et al. [33], in 29 Israeli karate athletes and students in physical education, bring back values of 119.3 ± 1.8 mmHg/83.8 ± 3.2 mmHg. The weekly frequency of training of subjects in the two studies was 5 meetings with one 5 - 6 hours daily duration. In addition, the cardiovascular request has a variable repercussion from one subject to another. Among the accused factors, it acts inter alia of aerobic capacity, aerobic endurance, level of training and technico-tactic level of the subject. At the end of Ruffier test, our SBP values increased significantly among senior athletes (∆ = +20.8%) and juniors (∆ = +15%), whereas DBP values varied little. Thus, a widening of differential (SBP-DBP) was observed. A mechanism likely to explain this change is the increase of cardiac flow with the intensity of exercise.

Moreover, HR values were increasing throughout the 3 fights, ranged between 72% - 89% of the theoretical HR_max (Figure 1). If the fight is the meeting which increases more the rate of heart rhythm, HR increasing is significant as of the 1stfight. This increase is concomitant with those of SBP values (Figure 2) and lactatemia (Figure 4) which are also statistically significant and progressive. The [La] concentrations reach after 420 s of effective fight 10.8 ± 1.2 mmol/l among juniors and 10.3 ± 1.5 mmol/l in seniors. Heller et al. [15] found peak [La] concentrations after 143 s fight of 11.4 mmol/l, Bouhlel et al. [18] after 720 s 10.2 ± 1.2 mmol/l. High HR response and [La] concentrations observed during fights proved the high intensity of exercise. Indeed, the fight of karate is characterized by sequences that vary from attack (kicks, blows of fist, kicks combined with blows of fist, mowing of legs followed by blows of fist...) and observations of adversary for counter-attacks. The duration of attack varies between 1 - 5 s, and its intensity is high. Consequently, anaerobic way is strongly requested during the fight. However, the relative share of aerobic metabolism is not yet well elucidated. However, the missing of steady state showed that the energetic demand during 3 fights surpassed the potential of aerobic metabolism and solicited the anaerobic glycolysis [34] [35] [36]. Francescato et al. [37] suggested that the overall energy requirement (VO_eq) given by the sum of VO₂ and VO₂-lactate is very high for the karate style. The zone of aerobic-anaerobic transition determined by a lactatemia from 4 mmol/l is thus rather close to the maximum effort. All things considered, validation of two criteria out of the three brought back by literature [38], namely: relatively high VO₂ max, low lactatemia and HR_max, suggest that our karate athletes developed a significant aerobic endurance by their training.

Finally, a fight of karate can be regarded as an intermittent anaerobic exercise, which is close to the concept of alternatively aerobic and anaerobic activity proposed byDel Monte and Menchinelli [39]. Using kihon and ju-kumite exercise which belong to “the culture’’ karate athletes, the latter request enormously aerobic way to carry out the gestural economy. However, the competitive preparation requires the development of the anaerobic metabolism because techniques used at the time of fights, ju-kumite and kihon solicit by brief, explosive, intense and fast actions of upper and lower limbs. Analysis of our results leads us to draw conclusions for training. In terms of training for karate in the pre-competitive period, we have noted that the heart rate and the lactatemia vary with the intensity of the fights during the competition. Thus, the coach can relate to a graph HR values-[La] concentrations. We then establish the profile of the homogeneity or the discrepancy of aerobic training. The intermittent test of 2 min 30 - 60 s - 2 min 30 and successive fights have a good performance. This profile highlights the sectors that must be improved as a priority and the procedures to be used. For example, the trainer can insert in his training cycle one or two microcycles where he would use in priority the intermittent forms of work of the type 2 min - 2 min, 3 min - 3 min, 4 min - 4 min to reach relatively quickly 2 min - 30 s, 3 min - 45 s, 4 min - 1 min. It is therefore a question of efficiency that is to say of the adaptation of systems to a type of effort specific to karate. In addition, we also believe that it is possible to offer high performance senior athletes, particularly to the classic training sessions, sessions favoring short duration and high intensity exercises. In terms of junior training, the content of the sessions must be adapted to meet the physiological demands expressed for this age category. Indeed, the use of anaerobic metabolism in adolescents at the end of puberty is strongly recommended. Since the energy expenditure in karate in competitive form requires brief and intense exercises requesting the anaerobic metabolism, it is necessary to be vigilant as for the situations to be set up in the sessions of competitive preparation.

Our study showed that the karate Congolese experts have a moderate recovery capacity and a required aerobic capacity. The evolution of HR, SBP and [La] concentrations during fights shows the importance of anaerobic and aerobic metabolisms to karate practice. This work thus makes it possible to validate the reliability of variables: HR, SBP, DBP, blood lactate concentrations to discriminate a certain number of karate experts during a selection starting from the cardiovascular and metabolic criteria relevant. Thus, the karate trainer, in the sub-Saharan African environment, can start from these criteria simple and easy to implement to build a system of control of training.

The authors gratefully thank Dr. Martin Mvitu for excellent scientific devices and technical assistance, to Dr. Joseph Bonazebi for statistical treatment. We would like to particularly thank all participants who made by to their authorities and commitment this possible study.

MJGA designed the study, participated in the implementation of experimental procedure and wrote the first version of the article. MJM, MELS and MKFN were involved in the acquisition of field data. PTB and MBJR have validated the experimental procedure and reread the first version of article. MA performed the statistical analysis of data and reread the final version of the article that has received the approval of all authors.

None.

Moulongo, J.G.A., Moussoki, J.M., Massamba, E.L.S., Massala Kitanga, F.N., Packa Tchissambou, B., Mabiala Babela, J.R. and Massamba, A. (2020) Recovery Capacity, Haemodynamic and Blood Lactate Changes during Training and Competition in Elite Congolese Karate Athletes. World Journal of Cardiovascular Diseases, 10, 257-273. https://doi.org/10.4236/wjcd.2020.105024