Exercise intensity at RPE13 in female Kendo practitioners
A pilot study exploring the detection of mental fortitude
Abstract
Abstract:Introduction: Kendo, a Japanese martial art, requires rigorous physical and mental training. Kendo practitioners who engage in daily mental training may experience a disparity between their subjective perception of exertion and the actual physiological load on their bodies. Methods: Fifteen healthy adult female kendo practitioners were recruited as participants. Participants were asked to report levels of exertion using the Ratings of Perceived Exertion (RPE) during a progressive, load-incremented stress test. The participants’ heart rate at the time of reporting RPE13, which is considered a “somewhat hard” level of exertion, as well as heart rate at the anaerobic threshold (AT) to measure actual load, were compared to the maximum heart rate measurement obtained during the test. Results: The participants’ heart rates at RPE13 were found to be higher than those at AT, based on their values as percentages of maximum heart rates. Conclusion: This study discovered that kendo practitioners engaged in regular mental training exhibited a higher heart rate at “somewhat hard” exertion (RPE13) compared to the anaerobic threshold (AT), indicating a relative increase in RPE. Additional research is necessary to determine if this effect is attributable to mental training.
Introduction
Kendo, a traditional Japanese martial art, demands both physical and mental training [1, 2, 3]. Training to increase mental discipline is effective in improving patience; studies on the psychological-competitive ability of kendo practitioners report that practitioners with higher performance have better patience [3, 4].
Meanwhile, psychological research suggests that the athletes’ mental toughness lies in the strength of their psychological defense mechanisms [5]. In psychoanalysis, the term repression is used to describe the act of shutting out uncomfortable feelings that threaten the stability of the ego and keeping them under consciousness. Athletes may adapt to a demanding competitive lifestyle through psychological defense mechanisms such as repression, and if their use of psychological defense mechanisms is excessive, they are at risk of facing problems such as overtraining syndrome and burnout [6].
Kendo practitioners must engage in mental training exercises during their practice sessions, and specific training methods have been developed for this purpose. These exercises are known to require an extremely high level of physical intensity [7], and kendo practitioners are expected to withstand this rigorous training. However, there is minimal research concerning their mental health. When competing, kendo practitioners generally do not acknowledge or express their feelings, and even if they encounter a difficult challenge, they do not complain; often, they focus on enduring and overcoming difficulties with mental strength alone, and their instructors provide guidance on these mental aspects. In other words, there is no method for quantitatively estimating how kendo practitioners - who perform in a culture of endurance, making it difficult to condition the body and mind - tolerate hard training.
Ratings of Perceived Exertion (RPE) is a complementary measure of exertion; it is a subjective but quantitative scale ranging from “very easy” to “very hard” on a scale of 6 to 20. RPE13 is the point where one feels that the level of exertion is “somewhat hard” and is also the first point where one perceives how “hard” it is. RPE is very positively correlated with heart rate [8]. In addition, the RPE when anaerobic threshold (AT) appears during a progressive, load-incremented stress test is 11–13; this result is not affected by exercise training, gender, or age [9, 10, 11].
In essence, under typical circumstances, there should be congruence between the values of RPE13 and heart rate at the AT. However, according to certain academic investigations, mental training exercises have been demonstrated to potentially mitigate the perception of fatigue [12, 13]. Consequently, RPE13 values of kendo practitioners who routinely engage in such mental training exercises may exhibit a relative elevation. This can result in a disparity between the subjective exertion (RPE) and actual physiological load (AT). Nevertheless, it remains to be elucidated whether such a deviation indeed manifests among kendo practitioners.
In this study, we hypothesized that the exercise intensity of RPE13, which kendo practitioners who engage in daily mental training feel as “somewhat hard,” increases and does not match the AT, and we attempted to verify this hypothesis.
Methods
Participants
Participants were 15 healthy adult female kendo practitioners. The participants had had long experience in kendo and were designated as national athletes by the prefecture. The purpose and procedures of the study were explained orally to all participants, and their consent to participate in the study was obtained in writing.
Research protocol
This study investigated which exertions are reported as RPE13 “somewhat hard” during a progressive, load-incremented stress test. The main evaluation items were the following: heart rate when RPE13 “somewhat hard” is reported, heart rate at the AT calculated by the V-slope method; and percentage of heart rate at the above 2 points to the maximum heart rate obtained in the progressive, load-incremented stress test.
The heart rate when RPE13 “somewhat hard” is reported is expressed as HRRPE13, and the HRRPE13 percentage of the maximum heart rate is expressed as %HRmaxatRPE13; the heart rate at the AT is expressed as HRAT, and the HRAT percentage of the maximum heart rate is expressed as %HRmaxatAT. The calculation method is as follows: %HRmaxatRPE13 = HRRPE13/maximum heart rate x 100, and %HRmaxatAT = HRAT/maximum heart rate x 100.
RPE13 during the progressive, load-incremented stress test
We implemented this study at Tochigi Institute of Sports Medicine and Science in Tochigi Prefecture, Japan. The participants visited the facility in the evening (5–7 p.m.), and we investigated which exertions are reported as RPE13 “somewhat hard” during a progressive, load-incremented stress test. Using a bicycle ergometer (Fujin-Raijin, OCLabo, Tokyo, Japan), respiratory measurement device (Aero Monitor AE-310S, Minato Medical Science), and heart rate monitor chest strap (PolarH10, Polar), a progressive, load-incremented stress test was performed with an increase of 45 watts/3 min until the participants were exhausted. RPE13 was reported by indicating a mark, and AT was determined by the V-slope method. Before starting the measurement, the participants were instructed on how to report RPE to make sure the reporting method was accurate. From the day before the progressive, load-incremented stress test, participants were prohibited from alcohol and caffeine consumption as well as strenuous exercise. In addition, based on the opinions of a psychiatrist and an orthopedic surgeon, the participants were confirmed to have no injuries or pain and no psychological problems that would lead to official diagnoses.
Analysis method
All values are expressed as mean ± standard deviation (SD). Statistics calculations were performed using SPSS11.0 J for Windows with a significance level of 5%. As the assumption of normality was confirmed by the Shapiro-Wilk test, a paired t-test was used to compare the heart rate and percentage of the maximum heart rate at RPE13 and at the AT.
Results
The study involved 15 healthy adult female kendo practitioners. The participants’ characteristics were as follows: age = 29.4 ± 8.8 years, height = 162.2 ± 6.0 cm, and weight = 62 ± 6.9 kg (mean ± SD). They had an extensive background in kendo, with an average experience of 23.0 ± 2.5 years.
Table 1 shows the results of the progressive, load-incremented stress test. At the AT, the heart rate (HRAT) was 143.5 ± 17.3 beats per minute, which was lower than that at RPE13 (HRRPE13, 156.6 ± 14.6 beats per minute). Figure 1 illustrates the comparison between HRAT and HRRPE13 and shows a significant difference (p < 0.05). Similarly, the ratio of the heart rate at to the maximum heart rate (%HRmaxatAT) was 78.7% ± 8.6%, which was lower than that at RPE13 (%HRmaxatRPE13, 86.2% ± 6.5%). Figure 2 illustrates the comparison between %HRmaxatAT and %HRmaxatRPE13 and shows a significant difference (p < 0.05).
Discussion
In this study, we explored the hypothesis that the heart rate at RPE13 (Ratings of Perceived Exertion) in women kendo practitioners who regularly participate in mental training is higher than the heart rate at the anaerobic threshold (AT). Contrary to previous research, the results indicated that exercise intensity surpassed AT levels when RPE13 was described as “somewhat hard.”
Earlier studies employing load-incremented stress tests in a general adult population estimated that AT occurs at an intensity of RPE 11–13, and the heart rate at RPE13 “somewhat hard” is 70–80% of the maximum heart rate [8, 9, 10, 11, 14, 15]. However, in this investigation, 11 out of 15 participants exhibited heart rates above 80% of their maximum while exercising at a level they identified as “somewhat hard.” This divergence might be attributed to several factors, including the enhancement of exercise efficiency through practice, which could lead to lower heart rates at the same exercise intensity, and the potential for subjective ratings of exercise to evolve, resulting in alterations in RPE.
Research utilizing RPE to gauge exercise load during practice among seasoned judo athletes has confirmed that RPE is a consistent and reliable measure of exercise load. Nonetheless, this research also suggests that practice can enhance exercise efficiency, yielding lower heart rates at identical exercise intensities, and that subjective assessments of exercise can shift, causing changes in RPE [16].
Previous research on RPE using a progressive, load-incremented stress test on the general adult population reported a subjective bias in RPE [17]. The present study of kendo practitioners also confirmed that the %HRRPE13 when reporting RPE13 “somewhat hard” exertion ranged from 77.1 to 95.9%.
RPE is a subjective assessment method based on individual perceptions, which is a weakness of this test as it cannot objectively assess exercise intensity, such as through the presence of lactic acid. However, we can mitigate the degree of subjective bias by integrating this method with an objective indicator that can be measured with relative ease, such as heart rate [18, 19].
Kendo, a sport originating in Japan, is said to cultivate the spirit; yet, there has been little quantitative evaluation of this aspect. This study is thus valuable because it sought to elucidate the mental aspect of kendo through the use of the RPE and heart rate. In the future, to further clarify the impact of mental aspects on RPE (Ratings of Perceived Exertion) and heart rate in kendo practitioners, it will be essential to delineate the characteristics of kendo practitioners by comparing them with general adults and athletes from other sports. This comparison aims to determine their influence on the relationship between RPE and heart rate and to elucidate the modifications in the RPE-heart rate relationship brought about by practicing kendo, including mental training.
Limitations
The study had several limitations. First, the skills of all the participants in this study were at a high level, representative of their prefectures. Just as higher technical levels of kendo are associated with higher levels of perseverance [3, 4], it is possible that the results have turned out differently for athletes at lower levels. Further research is necessary to ascertain whether the findings of this study are applicable to all women kendo practitioners, irrespective of their competition level. Second, the study was conducted in one team at only one time. Due to the small size of the study population, the published results should be interpreted with caution. Finally, the psychocultural background of the participants was not evaluated. Attitude and mentality in many traditional Japanese sports including kendo are said to impact the perceptions of sports in Japan [20]; thus, it is possible that Japanese athletes as a whole have an unyielding spirit of “self-discipline” and “spiritualism.” In future studies, a comparison should be made with foreign athletes and Japanese athletes in other sports to determine if these are truly characteristics of kendo practitioners.
Conclusion
This study investigated the subjective exercise intensity (RPE) and physiological load in kendo practitioners who routinely undergo mental training. The analysis revealed that heart rate at the point where one feels that the level of exertion is “somewhat hard” (RPE13) was significantly higher than the heart rate at. This may show that RPE increases relatively in kendo practitioners. However, further testing is needed to validate that these are the results of mental training. A future study should explore the possibility that mental training increases RPE relatively based on the results of this study.
The present study was supported by F-MIRAI (R&D Center for Frontiers of MIRAI in Policy and Technology) in University of Tsukuba. We would like to thank Editage for English language editing.
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