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Original Research

The Use of Yo-Yo Intermittent Recovery Level 1 and Andersen Testing for Fitness and Maximal Heart Rate Assessments of 6- to 10-Year-Old School Children

Bendiksen, Mads1; Ahler, Thomas2; Clausen, Helle1; Wedderkopp, Niels3; Krustrup, Peter1,4

Author Information
Journal of Strength and Conditioning Research: June 2013 - Volume 27 - Issue 6 - p 1583-1590
doi: 10.1519/JSC.0b013e318270fd0b
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Abstract

Introduction

Childhood physical inactivity and obesity are associated with risk factors for cardiovascular disease (14,25) and are serious concerns all over the world as low aerobic fitness and obesity track from childhood into adulthood (3,31). Testing of aerobic fitness in school children would provide schoolteachers, parents, and health professionals with information about the state and development of the pupils’ fitness level during childhood and indicate whether the physical education in schools and the sport club activities are sufficient to gain a high aerobic fitness and reduce the long-term risk of developing cardiovascular disease in adult life. However, the use of gold standard determination of maximal oxygen uptake using a metabolic cart during incremental treadmill running is time consuming and expensive, and the training-induced changes in V[Combining Dot Above]O2peak are generally small for children (5,23).

Several field tests have been introduced for children including the bleep test, the Yo-Yo tests, and the Andersen test (2,21,22), and we have recently shown that the Yo-Yo intermittent recovery level 1 children’s test (YYIR1C) and the Andersen test are reliable and valid for children younger than 10 years (1). These field tests are simple and inexpensive and are commonly used to test large groups at the same time with 10–15 individuals in each heat (2,8,20). Both tests are intermittent and can be performed on half a handball court (2 × 20 m), but the protocols are different with regard to running speed and exercise-rest periods. The YYIR1C test consists of 2 × 16-m running bouts at gradually increasing speeds until exhaustion, interspersed with 10-second active recovery jogs of 2 × 4 m. In contrast, the Andersen test is performed over a fixed 10-minute period with alternations between a total of twenty 15-second running bouts at self-controlled speed, interspersed with 15-second periods with passive recovery.

Knowledge about the intermittent exercise capacity of children is of great interest as most of the physical activity that takes place in the schoolyard and sports clubs are intermittent in nature. Recent studies with adults and adolescents have shown that the Yo-Yo intermittent recovery level 1 test (YYIR1) test is a valid measure of intermittent exercise capacity (20,26) and that the test is sensitive to rapid changes in fitness level and can clearly discriminate between participant groups with poor, intermediate, and high intermittent exercise capacity (7,29). However, to our knowledge the discriminant validity and the sensitivity of the YYIR1 test are still to be evaluated for children younger than 10 years.

Determination of maximal heart rate is frequently used as a tool to evaluate the participant effort and the quality of aerobic fitness tests. It is also necessary to ensure an accurate measure of the relative intensity of any type of physical training for an individual (11,28), as the predicted maximal heart rate equations like 220 − age and 208 − (0.7 × age) do not always provide accurate group measures and provide poor measures of individual maximal heart rates as the maximal heart rates usually ranges from 175 to 230 b·min−1 for 6- to 10-year-olds (2,4). In physical education activities, the intensity varies significantly between different types of activity and also varies between subjects participating in the same type of physical activity (12). Considering that recent evidence suggests that intense intermittent training is more effective for adults and children in improving aerobic and anaerobic fitness than moderate intensity training (17–19,30), it appears to be a good idea to measure the relative loading during physical education (PE) activities for school children by determining their individual maximal heart and the actual heart rate (HR) loading of all the pupils during their PE lessons. Previous investigations have shown that the YYIR1 test is a good tool to determine maximal heart rate for adolescent and adult football players (7) and that the Andersen test can determine maximal heart rate for 10- to 15-year-old children (2). However, none of the tests have been evaluated for their ability to elicit maximal heart rate for young children.

Accurate measurements of maximal heart rate are also required for optimizing submaximal testing protocols, which can be used for frequent nonexhaustive evaluation of fitness status (7,8,20,24). Recent investigations have shown that measurements of the HR loading in percentage of maximal heart rate during brief nonexhaustive YYIR1 and Yo-Yo intermittent endurance Level 2 (YYIE2) test protocols can be used to estimate the intermittent exercise performance and aerobic fitness of junior and elite football players. Submaximal Yo-Yo testing is appealing to sports coaches when only limited time is available for testing and when exhaustive testing would interfere with training and competition. In the school setting, submaximal Yo-Yo testing may also have a pedagogical advantage, as the test can be performed while the children are running side-by-side until the test cessation, without displaying the good and bad performers. However, so far, no submaximal tests have been shown to be valid for estimating intermittent exercise performance in children younger than 10 years.

Thus, the aims of this study were to evaluate whether the YYIR1 and the Andersen test can be used (a) to determine maximal heart rate of children aged 6–7, 8–9, and 9–10 years and to detect possible differences in the intermittent exercise performance of children in 2 groups aged 6–7 and 8–9 years, and (b) whether a brief submaximal version of the tests can be used to estimate intermittent exercise performance and changes in physical fitness.

Methods

Experimental Approach to the Problem

To evaluate the discriminant validity of the modified YYIR1C test and Andersen test for children in comparison to other tests, the modified YYIR1C test and the Andersen test were performed twice within 1 week for the 26 grade 0 and grade 2 children along with an incremental V[Combining Dot Above]O2peak treadmill running test. These tests were also used to evaluate the ability of the YYIR1C and Andersen tests to determine maximal heart rate. Heart rate measurements were obtained in 5-second intervals using Polar Team2 heart rate monitors (Polar Electro, Kempele, Finland) and stored on a computer for later analysis. For further evaluation of the ability of the tests to elicit maximal heart rate and to evaluate whether a brief submaximal version of the YYIR1C test can be used to estimate intermittent exercise performance and changes in physical fitness, 49 grade 3 pupils performed 3 repetitions of the YYIR1C test and 2 repetitions of the Andersen test 6 weeks apart. In the 6-week period between the tests, the pupils had a heterogenic physical activity ranging from inactivity to 3 weekly sessions of high-intensity training. The children were familiarized to the YYIR1C and the Andersen tests before the main testing days. The familiarization was done by a pretest 4 days before the first actual test. Before each of the tests, the children had a 5-minute warm-up including the first 2 minutes of the specific test they were about to carry out. All tests were performed at the same time of the day and in the same sports hall, i.e., at 9 AM for the G0 children and at 10 AM for the G3 children. The participants performed no strenuous physical activity for 24 hours before each of the testing sessions and were encouraged to digest a normal diet on the testing days.

Subjects

A total of 88 pupils were enrolled in the study of which 49 were from grade 3 (23 girls and 22 boys aged 9 years), 17 were from grade 2 (9 girls and 8 boys aged 8–9 years), and 18 were from grade 0 (12 girls and 6 boys aged 6–7 years). The 49 pupils from grade 3 had a body mass, height, and body mass index (BMI) of 34.8 ± 8.0 kg, 1.40 ± 0.06 m, and 17.7 ± 3.1, respectively, with corresponding values being 31.3 ± 5.2 kg, 1.36 ± 0.05 m, and 16.9 ± 2.5 for the grade 2 pupils and 24.8 ± 4.5 kg, 1.24 ± 0.04 m, and 16.2 ± 1.8 for the grade 0 pupils, respectively. Written consents were obtained from the parents of all participating pupils and verbal consent from all pupils. The study was carried out in accordance with the Declaration of Helsinki and was approved by the Regional Ethics Committee of Funen.

Test Protocol

The Yo-Yo Intermittent Recovery Level 1 Children’s Test

The test was performed indoors on one half of a timber floor handball court in accordance with the original YYIR1 test (7,10,20), with 2 modifications that the running shuttles were 2 × 16 m rather than 2 × 20 m and that the active recovery jogs were 2 × 4 m rather than 2 × 5 m. The rationale for these modifications is that the running distances had to be shortened to ensure a reasonably long running time for pupils at the age of 6–10 years (1). As in the original test, the participants run back and forth between cones placed at the starting/finishing line and turning line at progressively increasing speeds, interspersed by 10 seconds of jogging after each running bout around a cone placed behind the starting/finishing line. The rest periods, running periods, and the speed progression were controlled by beep sounds from a CD player using the same CD as for the YYIR1 test. The width of the running lanes was 1.3 m, and 6–12 pupils were tested at the same time. The performance outcome of the pupils was recorded by 3 investigators of which 2 were standing at the level of the starting/finishing line and 1 was standing at the level of the turning line. Each session was also video filmed to ensure correct notation of the test results. When a pupil had failed twice to reach the finishing line in time, the test was over and the distance covered was recorded as the test performance. The total duration of the test varied from 3 to 12 minutes. Before the test, the participants were thoroughly informed about the test protocol and had a 5-minute controlled warm-up before the test and a trial run for the first 2 minutes of the test to get acquainted with the initial running speeds.

The Andersen Test

The test was carried out indoors on one half of a timber floor handball court as for the YYIR1C test. Subjects ran from one line to the other on 20-m running lanes marked by cones, where they had to touch the floor behind the line with one foot, turn around, and run back. After 15 seconds, the test leader blew a whistle and the subjects stopped as quickly as possible (about 2 steps) and rested for the next 15 seconds. This procedure was followed for 10 minutes. Subjects ran as fast as they could to cover the longest possible distance during the 10-minute test, and the total distance covered was the test result. The test leader announced the end of each resting period by counting backward from 3 to 0. To collect data, each runner had a partner sitting at one end of the course and counting the number of completed laps (2 × 20 m) (2). Each test round was video filmed to ensure correct notation of the test results. The participants were thoroughly informed about the proceedings and had a 5-minute warm-up before the test.

Progressive Treadmill Test to Determine V[Combining Dot Above]O2peak

The progressive treadmill test had sex-differentiated protocols. Boys and girls started with a 3-minute walk at 4 km·h−1 to get acquainted with the treadmill, the face mask, and the safety harness. Then, the speed was increased to 7 km·h−1 for girls and 8 km·h−1 for boys for 2 minutes. After this, the inclination of the treadmill was raised by 3° every 2 minutes until a 9° inclination was reached. At 9° inclination, they ran for 1 minute and then the speed was increased by 0.5 km·h−1 for each minute until the child was exhausted as evaluated either by physiological criteria (HR > 200 b·min−1, RER ≥ 0.99 or leveling off on the V[Combining Dot Above]O2 curve) (28) or by subjective criteria (uncoordinated running, sweating, hyperventilating, or clear signs of unwillingness to continue). During the entire test, V[Combining Dot Above]O2, V[Combining Dot Above]CO2, and ventilation were measured breath by breath by the COSMED K4 online system (COSMED, Rome, Italy) and HR was determined in 5-second intervals by POLAR HR monitors (POLAR Team System, Polar Electro Oy, Kempele, Finland). The highest values obtained for V[Combining Dot Above]O2 and HR in 30-second intervals were used as the peak values.

Statistical Analyses

Differences in test performance and physical capacity between the 2 age groups were tested using 1-way analyses of variance. The test-retest reproducibility of peak heart rate was tested for the YYIR1C and the Andersen tests by calculating the coefficient of variation (CV), expressed as the SD of the differences between test-retest results divided by the mean values of test results and multiplied by 100 (6). The relationship between HRs after 1, 2, 3, and 4 minutes of tests and the test performance and V[Combining Dot Above]O2 was tested using linear regression analyses (Pearson’s product moment test). The data were tested for normality using the Shapiro-Wilk’s test. Magnitude of correlation coefficients was considered as trivial (r < 0.1), small (0.1 < r < 0.3), moderate (0.3 < r < 0.5), large (0.5 < r < 0.7), very large (0.7 < r < 0.9), and nearly perfect (r > 0.9) and perfect (r = 1) (15). Significance level in all analyses was set at 0.05. Data are presented as mean ± SD unless otherwise stated.

Results

Physical Capacity and Performance

Performance in the YYIR1C test and the Andersen test was 690 ± 375 m (range, 256–1,728 m) and 1,001 ± 79 m (866–1,161 m), respectively. For grade 2 pupils, the YYIR1C test performance was 84% better (994 ± 399 vs. 536 ± 218 m, p < 0.01) and the Andersen test performance was 10% better (1,050 ± 71 vs. 955 ± 56 m, p < 0.05) than grade 0 pupils (Figure 1).

Figure 1
Figure 1:
Intermittent exercise capacity, expressed as performance in the modified YYIR1C and Andersen tests and maximal oxygen uptake for grade 0 school children (6–7 years, n = 17, open bars) and grade 2 school children (8–9 years, n = 16, filled bars). Data are presented as mean ± SD. #Significantly different from grade 0 pupils. YYIR1C = Yo-Yo intermittent recovery level 1 children’s test.

V[Combining Dot Above]O2peak was 51.2 ± 6.7 ml·min−1·kg−1 (range, 38.9–65.1 ml·min−1·kg−1) or 1.45 ± 0.35 L·min−1 (0.83–2.13 L·min−1). Incremental treadmill test (ITT) exhaustion time was 11.5 ± 1.5 minutes (8.5–14.3 minutes). For grade 2 pupils, the ITT exhaustion time was 13% higher (12.3 ± 1.4 vs. 10.9 ± 1.3 minutes, p < 0.01) and V[Combining Dot Above]O2peak expressed in absolute values was 41% higher (1.71 ± 0.27 vs. 1.21 ± 0.22 L·min−1, p < 0.01) than grade 0 pupils, whereas V[Combining Dot Above]O2peak expressed relative to body mass was not significantly different between grades (12%, 54.2 ± 6.1 and 48.4 ± 6.2 ml·min−1·kg−1) (Figure 1).

Determination of Maximal Heart Rate

For the grade 0 and grade 2 pupils, the peak heart rate reached during the YYIR1C, the Andersen test, and the ITT were 205 ± 11, 207 ± 9, and 203 ± 7 b·min−1, respectively, corresponding to 98 ± 2, 99 ± 1 and 97 ± 2%, respectively, of the individual maximal heart rate (209 ± 9 b·min−1) (Figure 2). The peak heart rate value reached during the YYIR1C test and the Andersen test was 101 ± 4% (n = 30, p > 0.05) and 102 ± 2% (n = 29, p < 0.05) of the value reached during ITT (Figure 2). For the grade 3 pupils, the peak heart rate reached during the YYIR1C test was 208 ± 9 b·min−1, which was higher (p < 0.05) than during the Andersen test (204 ± 9 b·min−1; Figure 2). No significant differences were observed in peak heart rate between grades 0, 2, and 3 (207 ± 10, 210 ± 8, and 209 ± 8 b·min−1, respectively) or between boys and girls (207 ± 9 and 210 ± 9 b·min−1, respectively). The peak heart rate was slightly higher (210 ± 9 vs. 206 ± 8 b·min−1, p < 0.05) for children with BMI values below 17.5 (15.7 ± 1.0) compared to children with BMI values above 17.5 (20.3 ± 2.5). The CV value for test-retest peak heart rate response was 2.2% for the YYIR test (n = 63) and 1.9% for the Andersen test (n = 57).

Figure 2
Figure 2:
Peak heart rate values reached during the modified YYIR1C test, the Andersen test, and the ITT for 32 grade 0–2 children (6–9 years) and 49 grade 3 children (9–10 years). Mean and individual values are shown. The full lines connect the values obtained for each individual. ¤Significantly different from the ITT for grade 0–2 pupils. §Significantly different from the Andersen test for grade 3 pupils. ITT = incremental treadmill test; YYIR1C = Yo-Yo intermittent recovery level 1 children’s test.

Submaximal Yo-Yo Intermittent Recovery Level 1 and Andersen Testing

For the grade 0 and grade 2 pupils, the HRs after 1, 2, 3, and 4 minutes of the YYIR1C test was 168 ± 14, 183 ± 12, 191 ± 10, and 193 ± 9 b·min−1 or 80 ± 6, 88 ± 5, 91 ± 4, and 92 ± 3% of maximal heart rate, with corresponding values for the Andersen test being 192 ± 11, 195 ± 9, 196 ± 9, and 197 ± 9 b·min−1 and 92 ± 3, 93 ± 2, 94 ± 2, and 94 ± 2% of maximal heart rate (%HRmax). The grade 2 pupils had a lower (p < 0.05) relative HR than the grade 0 pupils after 2 minutes of the YYIR1C test (86 ± 4 vs. 90 ± 4%HRmax), whereas no difference was observed for the 2 groups after 2 minutes of the Andersen test (93 ± 2 and 94 ± 2%HRmax, p > 0.05).

For the grade 0 and grade 2 pupils, the observed %HRmax value after 1, 2, and 3 minutes of the YYIR1C test showed large inverse correlations with YYIR1C test performance (r = −0.61, −0.54, and −0.67, respectively, n = 26, p < 0.02) and the %HRmax value after 2 minutes correlated moderately with maximal oxygen uptake (r = −0.42, n = 26, p < 0.05). No significant correlations were observed between the 1-, 2-, and 3-minute HR response during the Andersen test and/or maximal oxygen uptake or Andersen test performance (r = −0.17 to 0.09, NS).

For the grade 3 pupils, the observed %HRmax values after 1, 2, and 3 minutes showed large inverse correlations with YYIR1C test performance (r = −0.56, −0.63, and −0.62, respectively, p < 0.05, n = 49) (Figure 3). No significant correlations were observed between the 1-, 2-, and 3-minute HR response during the Andersen test and the Andersen test performance (r = −0.15 to −0.02, n = 43, NS). When 2 YYIR1C tests were performed 6 weeks apart for grade 3 pupils, moderate to large inverse correlations were observed between the difference in HR after 2 minutes (r = −0.42, p < 0.05, n = 37) and 3 minutes (r = −0.53, p < 0.05, n = 32) of the YYIR1C test and the change in YYIR1C test performance (Figure 4) but not after 1 minute (r = −0.18, n = 38, NS) or 4 minutes (r = −0.29, n = 23, NS). No significant correlations were observed between changes in Andersen test HR after 1–4 minutes and the changes in Yo-Yo test performance (r = −0.17 to 0.16, n = 34, NS).

Figure 3
Figure 3:
Relationship between the HR after 2 minutes (open symbols) and 3 minutes (closed symbols) of the modified YYIR1C test, expressed in percentage of individual maximal heart rate, and performance in the modified YYIR1C test. Individual data for 49 grade 3 school children (9–10 years) are shown. HR = heart rate; YYIR1C = Yo-Yo intermittent recovery level 1 children’s test.
Figure 4
Figure 4:
Differences in HR after 2 minutes (open symbols) and 3 minutes (closed symbols) of 2 trials of the modified YYIR1C test performed 6 weeks apart, in relation to the change in performance of the modified YYIR1C test. Individual data for 36 grade 3 school children (9–10 years) are shown. HR = heart rate; YYIR1C = Yo-Yo intermittent recovery level 1 children’s test.

Discussion

The major findings of the present study were that the YYIR1C and the Andersen tests can be used to determine maximal heart rate and to detect differences in intermittent exercise performance of children aged 6–10 years. Moreover, HR measurements during a short version of the YYIR1C test may be used for frequent nondemanding testing of intermittent exercise performance and aerobic fitness for 6- to 10-year-old children.

The present study is the first to examine the HR response during intermittent running tests for 6- to 10-year-old children. It was revealed that the peak HR were high both for the YYIR1C and the Andersen tests, with average values for the entire subject group of 207 and 206 b·min−1, respectively. For the grade 0 and grade 2 pupils, it was observed that the peak HR reached during the YYIR1C test (205 b·min−1) and the Andersen test (207 b·min−1) were similar to or even higher than the values obtained during the ITT (203 b·min−1), which is usually considered as the gold standard maximal HR test (28). Interestingly, this was observed for both boys and girls, with the girls reaching peak HR of 208 and 210 b·min−1 in the YYIR1C and Andersen tests compared with 204 b·min−1 in the treadmill test. For the grade 3 pupils, the peak HR was slightly higher for the YYIR1C test than the Andersen test (208 vs. 204 b·min−1). These findings add to the previous findings that peak HR are as high in the YYIR1 test as in the ITTs for habitually active adults and elite soccer players (7,20). Only 1 of the 88 participating pupils had a peak HR in the YYIR1C test that was more than 5 b·min−1 lower than in the treadmill test. For this pupil, the YYIR1C test performance was only 256 m corresponding to a total exercise time of 3 minutes, which is usually considered to be too short to reach maximal HR (28). The peak heart rates during the YYIR1C test were almost similar to the values reached during the Andersen test, although it should be emphasized that a majority of the 8- to 10-year-old pupils reached a higher peak value in the YYIR1C test (45 of 67) and vice versa for the 6- to 7-year-old pupils (3 of 13). With regard to measurements of peak HR, the test-retest CV values were 2.2% (6–7 years: 2.6%, 8–10 years: 1.8%) for the YYIR1C test and 1.9% (6–7 years: 1.9%, 8–10 years: 1.8%) for the Andersen test, which are similar to or slightly higher than values obtained for adolescents and adults (7,21). For a majority of subjects who performed the 2 tests twice, the difference in test-retest HR was 0–4 b·min−1 (YYIR1C: 49 of 63, Andersen test: 47 of 57). Taken together, the present observations reveal that the YYIR1C test and the Andersen test can be used to make a valid estimation of maximal HR for large groups of 6- to 10-year-old children. The results also suggest that it is a good idea to carry out 2 tests per child and may indicate that the YYIR1C test is preferable for the 8- to 10-year-olds and that the Andersen test is preferable for the youngest children if only one of the tests is applied. Further studies are, however, warranted to provide more insight into the use of the tests for 6- to 7-year-olds and for heavily obese children with very low physical capacity.

The present results show that the YYIR1C and the Andersen tests can detect differences in exercise performance between grade 2 and grade 0 pupils, having a 10% difference in exhaustion time during incremental treadmill running. Thus, the YYIR1C test performance was 458 m (84%) better for the grade 2 than the grade 0 pupils, with corresponding values of 95 m (10%) for the Andersen test. The usefulness of a test is among other things related to its ability to detect systematic differences at group level (15), and the absolute level of reliability does not give any information on whether the reliability is acceptable (16). Nonetheless, it should be noted that the range in test performances and the CV values are very different for the 2 tests, due to the differences in test protocols with the YYIR1C test being an incremental test with 2 × 20 m shuttle runs with rather small speed increments, separated by 10-second rest periods (20), and the Andersen test being a fixed 10-minute test with the children running as far as they can in repeated 15-second exercise bouts, separated by 15-second rest period. Thus, for the grade 0 and 2 pupils, the ranges in performance were 256–1,728 and 866–1,161 m, respectively, and the CVs were 19% and 2.6%, respectively, for the YYIR1C test and the Andersen test (1). This means that the ratios between the group difference and the CVs are similar and large for the 2 tests (4.4 and 3.9, respectively), underlining that both tests can be used to discriminate exercise performance between subject groups within the age range of 6–10 years.

The present study also investigated whether HR measurements during a submaximal version of the YYIR1C test can provide information about intermittent exercise performance and maximal oxygen uptake. Actually, large inverse correlations were observed between the relative aerobic loading (%HRmax) after 1, 2, and 3 minutes and YYIR1C test performance for grade 0 and 2 pupils (r = −0.54 to −0.67) and grade 3 pupils (r = −0.56 to −0.63), and the 2-minute value showed a moderate inverse correlation with V[Combining Dot Above]O2peak (r = −0.42). Recent studies investigating adult elite soccer players and untrained middle-aged men have shown similar correlations between HR loading during the 4- to 6-minute YYIR1C and Yo-Yo IE2 test protocols and the Yo-Yo test performance and intermittent exercise performance during soccer matches (9,13,19,27). Moreover, the HR after 2 minutes of the YYIR1C test was significantly lower for the fitter grade 2 than the grade 0 pupils, and interestingly, when 2 YYIR1C tests were performed 6 weeks apart, moderate to large inverse correlations were observed between the difference in HR after 2 and 3 minutes of the YYIR1C test (r = −0.42 to −0.53) and the change in YYIR1C test performance (Figure 4). In accordance with recent studies on untrained adults and well-trained football players, this suggests that the HR response to submaximal YYIR1C testing is sensitive to training adaptations (9,13), although it should be emphasized that intermittent exercise performance is not only affected by central and peripheral aerobic factors and running economy but also anaerobic capacity. Therefore, a 2-minute version of the YYIR1C test may be appealing for schoolteachers for frequent nonexhaustive fitness testing, and a 2-minute version of the YYIR1C test also has the pedagogical advantage that all the children run all the shuttles beside each other at the same speeds. However, the correlations are not sufficiently high for complete replacement of the maximal testing, and further studies are required to elucidate whether the 2-minute version of the YYIR1C test is also a sensitive tool for detection of training adaptations for children. Moreover, the usefulness of a submaximal YYIR1C test relies on the availability of HR monitors, which are not common in many primary schools.

In summary, the YYIR1C and the Andersen tests are reproducible and valid for determining maximal heart rate for children aged 6–10 years. Moreover, the results suggest that the YYIR1C and the Andersen tests are sensitive in detecting differences in intermittent exercise performance of specific subject groups and that a short submaximal version of the YYIR1C test may be used for frequent nondemanding testing of intermittent exercise performance and aerobic fitness.

Practical Applications

The results of the present study reveal that 2 simple and inexpensive intermittent field tests, the YYIR1C and the Andersen tests, can be used to detect differences and changes in fitness level for 6- to 10-year-old children and to determine maximal heart rate. Together with the recent findings that these tests are reproducible and are valid in estimating maximal oxygen uptake (1), it is now clear that schoolteachers, health workers, and sports club coaches have been provided with tools to conduct tests that can provide reliable and valid information about physical fitness and cardiovascular health status of 6- to 10-year-old children. When using these tests for the determination of maximal heart rate, it is also possible to evaluate the pupils individual exercise intensity during the physical education lessons or sports club training sessions and also to conduct submaximal or maximal intermittent testing to provide feedback on the changes in physical fitness after interventions with intensified physical training.

Acknowledgments

The authors would like to thank the participants for their contribution and enthusiasm and the schoolteachers and schools for their support. The authors also thank Sarah R Jackman for technical support. A special thanks to Jesper Kloppenborg from the Municipality of Copenhagen for his expertise and assistance. The project was partly financed with funding from the Department of Exercise and Sport Sciences, University of Copenhagen, and with kind assistance from Team Denmark and the Center for Research in Childhood Health, University of Southern Denmark.

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Keywords:

intermittent exercise performance; submaximal YYIR1 children’s test; treadmill test; V[Combining Dot Above]O2peak; kids

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