Moderators of Perceived Effort in Adolescent Rowers during a Graded Exercise Test

Physical activity promotes mental health. A key factor is self-regulation. In the eld of sports, self-regulation is related to the psychophysiological competence of rating of perceived e ort (RPE). It was reported that adolescents have lower RPE competencies than adults, and it was hypothesized that this e ect depends on physiological and cognitive development. The present study investigated in a sample of adolescents whether the RPE is related to basic cognitive competencies. Twelve rowers performed cognitive tests and a graded exercise test on a rowing ergometer, in which they continuously rated their perceived e ort. Objective load measures and subjective perceptions were highly correlated (rho=0.95–0.99). Furthermore, these correlations were inter-individually moderated by measures of mental speed and spontaneous exibility. The results con rm the signi cance of basal cognitive competencies for conscious load perception. It is discussed whether regular sport has bene cial e ects on the development of RPE competencies by enhancing cognitive regulation. Keywords:adolescence; perceived exertion; cognition; mental health; rowing 1. Introduction Physical activity promotes the mental health of adolescents [1]. Adherence to physical activity is a great individual challenge [2], and the key factors are motor competences, control and self-regulation competences as well as perceptual competences [3,4]. In the eld of sports, these competences refer to the ability to plan, execute and regulate physical performance autonomously and to choose adequate loads for achieving physical and mental health. A signi cant perceptual component is the competence for rating of perceived e ort (RPE). Accordingly, RPE-based load regulation is a widely applied method in health sports [5,6]. Investigating the factors of the RPE is relevant for evidence-based health promotion through improvement of self-perception, e ective self-regulation as well as for supporting personality development [5,7]. The present study investigates the relationship between RPE, cognitive information processing speed and cognitive exibility. RPE

perceived e ort (RPE). Accordingly, RPE-based load regulation is a widely applied method in health sports [5,6]. Investigating the factors of the RPE is relevant for evidence-based health promotion through improvement of self-perception, e ective self-regulation as well as for supporting personality development [5,7]. The present study investigates the relationship between RPE, cognitive information processing speed and cognitive exibility. RPE is regarded as psychophysical competence [8], which develops during maturation [9]: Until the age of 12 years, children are only able to discriminate up to four intensities. During adolescence (13–18 years) a more ne-grained perception develops, and adolescents become able to di erentiate 10 to 15 intensity levels [9]. However, the RPE performance is still lower than in adults and the reasons are still unclear. Groslambert and Mahon [9] hypothesized that cardiorespiratory factors become more important for the RPE with increasing age. Furthermore, as the RPE also has cognitive components, it seems to depend on the cognitive developmental status. Physical activity typically declines in adolescence [10]. Investigating the mediating factors of the RPE is important for understanding control and self-regulation as well as engagement of adolescents in physical activities. Int. J. Environ. Res. Public Health2020,17, 8063; doi:10.3390 /ijerph17218063 /journal/ijerph

Int. J. Environ. Res. Public Health2020,17, 8063 2 of 10 Competence for Rating of Perceived E ort The RPE results from the integration of multiple a erent signals from the body periphery into a single percept. It is a subjective measure, but the rating of perceived e ort correlates highly with objective cardiorespiratory and metabolic parameters. This has been shown across nearly all age groups and in a variety of populations: trained, untrained, sedentary, overweight persons and coronary heart disease patients [11–14]. St.Clair-Gibson [6] understood the perception of e ort as an exchange of information between the brain and the peripheral physiological system involved in energetic regulation. Furthermore, according to the Corollary Discharge hypothesis, the brain makes assumptions about how the e ort will feel in the near future based on motor commands to the muscles [15]. The underlying concepts correspond essentially to the idea of forward modelling in motor control. Here, the anticipated feeling of the movement has direct consequences on perception and action [16]. Empirical ndings from studies with adults highlight the signi cance of speci c cognitive abilities for RPE. Lohse and Sherwood [17] showed that the attentional focus a ects RPE. Schmitz et al. [18] investigated individuals with and without intellectual disabilities and found weaker correlations between heart rate and RPE in individuals with intellectual disabilities. Furthermore, they reported signi cant correlations between RPE and the speed of information processing as well as cognitive exibility in male soccer players. In a follow-up study, Schmitz and Sommer [19] replicated these results with female soccer players. Anderson et al. [20] assign these abilities to the executive control system of children, which is a framework derived from developmental neuropsychological literature. It subsumes information processing (including processing speed), cognitive exibility, attentional control and goal setting as main components. The present study investigates the signi cance of the rst two abilities for the RPE competence in adolescents. In this regard, subjective load perceptions were correlated with objective performance indicators and it was analyzed whether information processing and cognitive exibility moderate these correlations. Information processing was operationalized by the speed of the

attentional control and goal setting as main components. The present study investigates the signi cance of the rst two abilities for the RPE competence in adolescents. In this regard, subjective load perceptions were correlated with objective performance indicators and it was analyzed whether information processing and cognitive exibility moderate these correlations. Information processing was operationalized by the speed of the information processing [20]. Cognitive exibility was operationalized by spontaneous and reactive exibility [21]. In contrast to the eld study from Schmitz et al. [18], the present study was performed as a laboratory study in order to control the load and reduce the inter-individual variability. Load can be well controlled during graded exercise tests performed on a treadmill, a cycling ergometer or a rowing ergometer. The study focused on ergometer rowing, because the force production depends more on whole body movements (arm, upper body and leg movements) than during cycling and running, which might support the perception of e ort. The study investigated the following hypotheses in a sample of adolescent rowers: 1. The correlation between heart rate and RPE is moderated by the speed of the information processing measured by the Number Connection Test. 2. The correlation between heart rate and RPE is moderated by spontaneous and reactive exibility measured by the Five-Point Test. 2. Materials and Methods Twelve junior athletes (9 boys, 3 girls) participated in the study. They belonged to a regional selection team and therefore were regarded as skilled. They were on average 15.9 years old (standard deviation SD: 1.2 years) and had 9.9 (SD: 1.1) years of education. All of them had regularly participated in competitive rowing sports. As part of their admission to the regional rowing federation, all of them had been medically examined within the last year with regard to their tness for competitive sports. Moreover, they all answered a questionnaire from the German Society for Sports Medicine and Prevention, which is an adapted version of the Physical Activity Readiness Questionnaire (PAR-Q) of the Canadian Society for Exercise Physiology. The questionnaire yielded no results pointing to a health restriction. The participants and their legal

the last year with regard to their tness for competitive sports. Moreover, they all answered a questionnaire from the German Society for Sports Medicine and Prevention, which is an adapted version of the Physical Activity Readiness Questionnaire (PAR-Q) of the Canadian Society for Exercise Physiology. The questionnaire yielded no results pointing to a health restriction. The participants and their legal representatives gave their

Int. J. Environ. Res. Public Health2020,17, 8063 3 of 10 written informed consent to participation. The study was performed in accordance to the Declaration of Helsinki inclusive its later amendments and had been pre-approved by the Ethics Committee of the author's former institution, the Carl von Ossietzky University of Oldenburg. 2.1. Procedure The participants were instructed to eat a su ciently high carbohydrate diet on the test day and to take their last meal two hours before the start of the test. On the test day, each participant rst performed the cognitive tests and then the physical exercise. 2.1.1. Cognitive Assessment The present study applied the same cognitive performance tests as [18,19]. Two non-verbal neuropsychological paper–pencil tests assessed the speed of information processing and cognitive exibility. In the Number Connection Test the participants had to connect the numbers one to ninety in ascending order as quickly as possible. On a DIN A4 sheet of paper, consecutive numbers were located directly above, below, to the left, to the right or at a diagonal position to each other. Performance time was regarded as a measure for speed of information processing. The outcome correlates on a medium-to-large level (r=0.40–0.83) with the outcome of the intelligence tests. It is related to uid intelligence [22,23]. In the Five-Point Test, the participants received two sheets of paper (DIN A4) with forty preprinted rectangles. Each rectangle contained ve dots. The participants had to produce unique designs by connecting two to ve dots. The instruction was to produce as much di erent designs as possible within 3 min while avoiding repetitions [24]. The test measured two aspects of exibility. The number of unique designs re ects spontaneous exibility; the percentage of perseveration errors re ects cognitive exibility emerging from inhibition, i.e., reactive exibility [21,25–27]. The normative data of adults were published by Goebel et al. [25] and Cattelani et al. [28]. A correction index for age and education has been provided by Cattelani et al. [28], allowing comparing the number of unique designs with age-standardized normative data. The correction is not necessary for perseveration. 2.1.2. Exercise Performance test

from inhibition, i.e., reactive exibility [21,25–27]. The normative data of adults were published by Goebel et al. [25] and Cattelani et al. [28]. A correction index for age and education has been provided by Cattelani et al. [28], allowing comparing the number of unique designs with age-standardized normative data. The correction is not necessary for perseveration. 2.1.2. Exercise Performance test All participants were familiar with the graded exercise test, since they had already participated in a similar test one year before. All tests were performed on a Concept II (model D) rowing ergometer. The drag factor was set to 145 for men and 135 for women. A higher drag factor re ects a higher air resistance of the ywheel. One to two weeks prior to the study, all participants had participated in a 2000-max test during performance assessment in the regional selection team, in which they had to row the distance of 2000 m as fast as possible. This test is one of the standard procedures in rowing-speci c performance diagnostics and is typically used by the head coach to determine the peak power (Ppeak) of each athlete [29–32]. For the graded exercise test, six submaximal intensities were de ned relative to Ppeak. After resting for four minutes on the ergometer, the participants rowed with 35%, 45%, 55%, 65%, 75% and 85% of Ppeak for four minutes each. Before the intensity increased, they had a break of one minute. During rest, during the breaks as well as 150 s and 330 s after test termination, capillary blood samples were drawn from a hyperemised earlobe into 10 L end-to-end capillaries to analyze the lactate concentrations. Lactate concentrations were determined by the Super GL compact system (Dr. Müller Geraetebau GmbH, Freital, Germany). The software Winlactat 4.6.2.15 (mesics, GmbH, Muenster, Germany) was used to determine the individual lactate thresholds. The lactate threshold (LT) and the individual anaerobic lactate threshold (IAT) were calculated according to the method proposed by Dickhut et al. [33]. The times of LT and IAT were determined by a polynomial t (quartic polynomials).

The software Winlactat 4.6.2.15 (mesics, GmbH, Muenster, Germany) was used to determine the individual lactate thresholds. The lactate threshold (LT) and the individual anaerobic lactate threshold (IAT) were calculated according to the method proposed by Dickhut et al. [33]. The times of LT and IAT were determined by a polynomial t (quartic polynomials).

Int. J. Environ. Res. Public Health2020,17, 8063 4 of 10 Peak heart rate (HRpeak) was calculated according to the formula proposed by Hottenrott et al. [34]. Heart rate was measured continuously with 1 Hz (acentas GmbH, Hoegertshausen, Germany). The participants wore a breast belt, which transmitted the data wirelessly to a laptop computer. The software enables setting markers, which was used to denote the points in time when perceived e ort was rated. Perceived e ort was rated with the Borg scale. The rating scale di erentiates 15 intensity levels ranging from 6 (no e ort at all) to 20 (maximal exertion) [8]. Perceived e ort was rated during rest, and at 60 s and 210 s of each stage of the graded exercise test. Thus, the RPE was assessed every 150 s. 2.2. Statistics Means and standard deviations (SD) were calculated for the physiological data. Medians and interquartile ranges (IQR) were calculated for the data from the cognitive performance tests. Di erences between the cognitive data with reference data from normative samples were tested for signi cance with Wilcoxon rank-sum tests. To get an indicator for the individual RPE competence, for each participant a Spearman's rho was calculated by correlating the ranks of the heart-rate data and the ranks of the RPE data. Spearman rank correlation analyses focus on the monotonicity between two variables and can be used to analyze linear as well as non-linear relationships. To test Hypothesis 1, the rho-coe cients from these analyses were taken as the dependent variable in another Spearman rank correlation analysis and the performance time in the Number Connection Test as the independent variable. The same procedure was applied for testing Hypothesis 2 with unique designs and perseveration errors from the Five-Point Test as independent variables. Thep-levels from the analysis for Hypothesis 2 were corrected according to the stepwise Bonferroni–Holm procedure, because the Five-Point Test provides two measures for exibility. Furthermore, a Bayesian linear regression analysis was performed with all cognitive variables as predictors. Fisher's z-transformation was applied to the coe cients of the Spearman rank correlations between heart rate and RPE,

Test as independent variables. Thep-levels from the analysis for Hypothesis 2 were corrected according to the stepwise Bonferroni–Holm procedure, because the Five-Point Test provides two measures for exibility. Furthermore, a Bayesian linear regression analysis was performed with all cognitive variables as predictors. Fisher's z-transformation was applied to the coe cients of the Spearman rank correlations between heart rate and RPE, which were then taken as a criterion variable. Bayesian approaches have been recommended for sport scienti c studies with low sample sizes [35]. Power (ß) is described for insigni cant results. 3. Results 3.1. Graded Exercise Test The mean Ppeak was 273.80 (SD: 49.03) W. In the graded exercise test, the participants yielded a maximum power output of 222.33 (SD: 46.44) W, which corresponds to 81% of Ppeak. The relative power output was 3.09 (SD: 0.69) W/kg. The individual heart rate data and lactate concentrations are shown in Figure. During the graded exercise test, the heart rates increased linearly. The participants had a maximum heart rate of 187.8 (SD: 9.9) beats per minute. Participants 2, 5, 6 and 12 reached their HRpeak. Three to six minutes after completion, the heart rates decreased towards the initial level during rest, but none of the participants reached resting heart rate. Lactate concentrations are shown in Figureb. They increased exponentially during the graded exercise test. The maximum lactate averaged 7.03 (SD: 2.6) mmol/L. The mean lactate threshold was determined at 0.93 (SD: 0.24) mmol/L and the individual anaerobic threshold at 2.30 (SD: 0.34) mmol/L. The participants reached the IAT on average after 21.5 (SD: 3.4) min. The span ranged from 17.3 to 26.2 min, indicating that the energy metabolism di erent inter-individually, which is also re ected by di erent rates of lactate decrease during the six minutes after the test had ended. Ratings of perceived e ort are plotted against the heart rate data in Figure. Individual data are provided as Supplementary Material (Data_Rowing.xlsx). The RPE also increased linearly during the graded exercise test. The individual coe cients of the correlations between heart rate and RPE ranged from 0.95 to 0.99 (median rho:

during the six minutes after the test had ended. Ratings of perceived e ort are plotted against the heart rate data in Figure. Individual data are provided as Supplementary Material (Data_Rowing.xlsx). The RPE also increased linearly during the graded exercise test. The individual coe cients of the correlations between heart rate and RPE ranged from 0.95 to 0.99 (median rho: 0.98 IQR: 0.02) and were all highly signi cant (p<0.001).

Int. J. Environ. Res. Public Health2020,17, 8063 5 of 10Int. J. Environ. Res. Public Health 2020, 17, x 4 of 10 Perceived effort was rated with the Borg scale. The rating scale differentiates 15 intensity levels ranging from 6 (no effort at all) to 20 (maximal exertion) [8]. Perceived effort was rated during rest, and at 60 s and 210 s of each stage of the graded exercise test. Thus, the RPE was assessed every 150 s. 2.2. Statistics Means and standard deviations (SD) were calculated for the physiological data. Medians and interquartile ranges (IQR) were calculated for the data from the cognitive performance tests. Differences between the cognitive data with reference data from normative samples were tested for significance with Wilcoxon rank-sum tests. To get an indicator for the individual RPE competence, for each participant a Spearman’s rho was calculated by correlating the ranks of the heart-rate data and the ranks of the RPE data. Spearman rank correlation analyses focus on the monotonicity between two variables and can be used to analyze linear as well as non-linear relationships. To test Hypothesis 1, the rho- coefficients from these analyses were taken as the dependent variable in another Spearman rank correlation analysis and the performance time in the Number Connection Test as the independent variable. The same procedure was applied for testing Hypothesis 2 with unique designs and perseveration errors from the Five-Point Test as independent variables. The p-levels from the analysis for Hypothesis 2 were corrected according to the stepwise Bonferroni–Holm procedure, because the Five-Point Test provides two measures for flexibility. Furthermore, a Bayesian linear regression analysis was performed with all cognitive variables as predictors. Fisher’s z-transformation was applied to the coefficients of the Spearman rank correlations between heart rate and RPE, which were then taken as a criterion variable. Bayesian approaches have been recommended for sport scientific studies with low sample sizes [35]. Power (ß) is described for insignificant results. 3. Results 3.1. Graded Exercise Test The mean Ppeak was 273.80 (SD: 49.03) W. In the graded exercise test, the participants yielded a maximum power output of 222.33 (SD:

The study explores how cognitive abilities affect perceived effort in adolescent rowers.