Abstract
“A day without exercise, is a day without meaning”. Daily exercise is for many people throughout the world what nourishes their lives. For children exercise is an enjoyable and embedded part of daily life, for the teenagers an important way of learning and handling their social relationships, and in the elite adult setting as an essential tool in the pursuit of glory. The issues addressed in this thesis are the physiological responses to a wide variety of exercise, from the 6 yr old pupil playing Unihockey, via the recreational under 18 yr (U18) teenage female soccer player and to the elite soccer players performing at the top level. Investigating the important questions requires high quality testing protocols; therefore the present thesis designed and carefully investigated a number of testing protocols.
In study 1 the reliability and validity of two intermittent running tests, the Yo–Yo Intermittent Recovery level 1 children’s test (YYIR1c) and the Andersen test were investigated as tools for estimating VO2max in children under the age of 10. No significant differences were observed in test–retest performance of the YYIR1c (693±418 (±SD) and 670±328 m, r2=0.79, CV=19%, p>0.05, n=32) and the Andersen test (988±77 and 989±87 m, r2=0.86, CV=3%, p>0.05, n=31). The YYIR1c (r2=0.47, n=31, p<0.05) and Andersen test performance (r2=0.53, n=32, p<0.05) correlated with the VO2max, which highlighted that both the YYIR1c and the Andersen tests are reproducible and can be used as an indicator of aerobic fitness for 6- to 9-year-old children.
The YYIR1c was also shown to have a high contruct validity, meaning that it can detect differences in fitness levels between subject-groups, since two repetitions of the YYIR1c and Andersen tests, carried out within 1 week by 6- to 7-year-olds and 8- to 9-year-olds (grade 0, n=17; grade 2, n=16) showed that grade 2 pupils had a 84% better (p<0.05) YYIR1c test performance and 10% better (p<0.05) Andersen test performance than grade 0 pupils. Grade 3 pupils was tested 6 weeks apart (n=49), and changes in the sub-maximal HR correlated with the change in YYIR1c test performance (r=-0.42 to -0.53, HR after 2 and 3 min respectively, p<0.05), proving that submaximal YYIR1c testing can be used for frequent non-exhaustive fitness assessments. The maximal version of the YYIR1c and the Andersen test showed to elicit HRmax (p<0.05) in both grade 0-2, and grade 3 pupils, with HRpeak during the Andersen test reaching significantly higher values than observed during the incremental treadmill test (ITT), even though this is thought as a golden standard HRpeak test.
The ball games investigated in study 3, consisted of small-sided football (FO), Basketball (BA) and Unihockey (UH), and elicited significantly higher aerobic loading in the subject group of 87 pupils 8-9 yr old pupils than Circuit training (CT), Walking (W) and Nintendo Wii (NW) games. Time spent with HR>80 and 90%HRmax, respectively in FO (45±3 (±SD) and 12±3, BB (39±3 and 13±2%) and UH (23±3 and 11±2%) was higher (p<0.05) than in CT, W and NW (0-5%), with time spent with >80%HRmax being higher (p<0.05) in FO than UH. No significant differences were observed in HR response to ball games between genders, different fitness levels; BMI’s and sports club participation. A simple short-term, low-volume, PE-based ball game intervention of 6-weeks, improved (p<0.05) the physical fitness in young school children, whereas traditional PE sessions created no adaptations (p>0.05) in sub-maximal exercise response or maximal intermittent exercise performance.
In study 4, the physiological demands in youth female football matches was shown to be high, with average heart rates of 170±2 bpm during Under-18 (U18) female soccer matches and a total number of activity changes of 1401±55. Total distance covered and high-intensity running was 9.11±0.25 and 1.11±0.07 km respectively. Decrements in running performance occurred towards the end of games as the high-intensity running decreased (p<0.05) from 0–20 to 60–80 min with 37%.
In study 5, the physiological response to the Copenhagen Soccer Test (CST) was shown to be reproducible and comparable to that of high-level competitive match-play, since no differences were observed between CST and the competitive match. Results showed that heart rate (HR) mean was 85±1% and 86±1% HRmax (p>0.05) and recovery plasma creatine kinase (24 h:312±57 and 324±76U/L, p>0.05). Muscle glycogen decreased (p<0.05) ̴50% during CST, which was not different from the competitive match (p<0.05). The CST allowed for rapid muscle sampling and showed a four-fold higher glycogen utilization during the warm-up and the first 15 min of CST than during 60-90 min of CST. Muscle lactate was elevated (p<0.05) approximately five-fold after an intense exercise period, and muscle creatine phosphate was lowered (p<0.05) by ̴60%. Sprint velocity (2•20 m) decreased (p<0.05) by 7% during CST.
In study 6, the physiological response to the Copenhagen Soccer Test for women (CSTw) was comparable to that of high-level female competitive matches, with no significant differences between total distance covered, amount of high intensity running and sprinting (p>0.05) measured with ZXY Sports Tracking System. During CSTw, HRmean was 85±2 %HRmax with 35±2% of playing time spent above 90% of HRmax. Blood lactate increased (p<0.05) from 1.4±0.3 mmol/L to an average of 4.7±0.5 mmol/L during CSTw, with no changes during the test. Sprint performance (2•20 m) decreased (p<0.05) by 3% during CSTw, whereas the technical performance during CSTw showed no significant changes.
In study 7, the Yo-Yo Intermittent Endurance level 2 test (YYIE2) was proven to be reproducible for elite female players (CV=3.5%). Moreover, YYIE2 performance can be used as an indicator of the match specific physical capacity of female soccer players, since it correlated to the amount of high-intensity (>15 km/h) running in competitive matches (r=0.70) and could be used to differentiate the intermittent exercise performance of players in different playing positions and different competitive levels. Thus, wide midfielders (2057±550 m) had a higher YYIE2 test performance (p<0.05) than central defenders (1588±534 m) and attackers (1516±401 m), but not central midfielders (1764±473 m) or full-backs (1964±522 m). Moreover elite senior female players (1774±532 m) performed better than elite youth (1490±447 m; n=42), domestic (1261±449 m; n=46) and sub-elite players (994±373 m; n=19; p<0.05). Also in the stages of the season, differences occurred, with middle and end season being higher than the preparation period for elite youth female players (1767±539 and 1742±503 vs 1564±504 m) and in elite senior female players, YYIE2 test performance increased by 14% (p<0.05) after completing 4 weeks of intense training before participation in FIFA Womens World Cup.
In study 1 the reliability and validity of two intermittent running tests, the Yo–Yo Intermittent Recovery level 1 children’s test (YYIR1c) and the Andersen test were investigated as tools for estimating VO2max in children under the age of 10. No significant differences were observed in test–retest performance of the YYIR1c (693±418 (±SD) and 670±328 m, r2=0.79, CV=19%, p>0.05, n=32) and the Andersen test (988±77 and 989±87 m, r2=0.86, CV=3%, p>0.05, n=31). The YYIR1c (r2=0.47, n=31, p<0.05) and Andersen test performance (r2=0.53, n=32, p<0.05) correlated with the VO2max, which highlighted that both the YYIR1c and the Andersen tests are reproducible and can be used as an indicator of aerobic fitness for 6- to 9-year-old children.
The YYIR1c was also shown to have a high contruct validity, meaning that it can detect differences in fitness levels between subject-groups, since two repetitions of the YYIR1c and Andersen tests, carried out within 1 week by 6- to 7-year-olds and 8- to 9-year-olds (grade 0, n=17; grade 2, n=16) showed that grade 2 pupils had a 84% better (p<0.05) YYIR1c test performance and 10% better (p<0.05) Andersen test performance than grade 0 pupils. Grade 3 pupils was tested 6 weeks apart (n=49), and changes in the sub-maximal HR correlated with the change in YYIR1c test performance (r=-0.42 to -0.53, HR after 2 and 3 min respectively, p<0.05), proving that submaximal YYIR1c testing can be used for frequent non-exhaustive fitness assessments. The maximal version of the YYIR1c and the Andersen test showed to elicit HRmax (p<0.05) in both grade 0-2, and grade 3 pupils, with HRpeak during the Andersen test reaching significantly higher values than observed during the incremental treadmill test (ITT), even though this is thought as a golden standard HRpeak test.
The ball games investigated in study 3, consisted of small-sided football (FO), Basketball (BA) and Unihockey (UH), and elicited significantly higher aerobic loading in the subject group of 87 pupils 8-9 yr old pupils than Circuit training (CT), Walking (W) and Nintendo Wii (NW) games. Time spent with HR>80 and 90%HRmax, respectively in FO (45±3 (±SD) and 12±3, BB (39±3 and 13±2%) and UH (23±3 and 11±2%) was higher (p<0.05) than in CT, W and NW (0-5%), with time spent with >80%HRmax being higher (p<0.05) in FO than UH. No significant differences were observed in HR response to ball games between genders, different fitness levels; BMI’s and sports club participation. A simple short-term, low-volume, PE-based ball game intervention of 6-weeks, improved (p<0.05) the physical fitness in young school children, whereas traditional PE sessions created no adaptations (p>0.05) in sub-maximal exercise response or maximal intermittent exercise performance.
In study 4, the physiological demands in youth female football matches was shown to be high, with average heart rates of 170±2 bpm during Under-18 (U18) female soccer matches and a total number of activity changes of 1401±55. Total distance covered and high-intensity running was 9.11±0.25 and 1.11±0.07 km respectively. Decrements in running performance occurred towards the end of games as the high-intensity running decreased (p<0.05) from 0–20 to 60–80 min with 37%.
In study 5, the physiological response to the Copenhagen Soccer Test (CST) was shown to be reproducible and comparable to that of high-level competitive match-play, since no differences were observed between CST and the competitive match. Results showed that heart rate (HR) mean was 85±1% and 86±1% HRmax (p>0.05) and recovery plasma creatine kinase (24 h:312±57 and 324±76U/L, p>0.05). Muscle glycogen decreased (p<0.05) ̴50% during CST, which was not different from the competitive match (p<0.05). The CST allowed for rapid muscle sampling and showed a four-fold higher glycogen utilization during the warm-up and the first 15 min of CST than during 60-90 min of CST. Muscle lactate was elevated (p<0.05) approximately five-fold after an intense exercise period, and muscle creatine phosphate was lowered (p<0.05) by ̴60%. Sprint velocity (2•20 m) decreased (p<0.05) by 7% during CST.
In study 6, the physiological response to the Copenhagen Soccer Test for women (CSTw) was comparable to that of high-level female competitive matches, with no significant differences between total distance covered, amount of high intensity running and sprinting (p>0.05) measured with ZXY Sports Tracking System. During CSTw, HRmean was 85±2 %HRmax with 35±2% of playing time spent above 90% of HRmax. Blood lactate increased (p<0.05) from 1.4±0.3 mmol/L to an average of 4.7±0.5 mmol/L during CSTw, with no changes during the test. Sprint performance (2•20 m) decreased (p<0.05) by 3% during CSTw, whereas the technical performance during CSTw showed no significant changes.
In study 7, the Yo-Yo Intermittent Endurance level 2 test (YYIE2) was proven to be reproducible for elite female players (CV=3.5%). Moreover, YYIE2 performance can be used as an indicator of the match specific physical capacity of female soccer players, since it correlated to the amount of high-intensity (>15 km/h) running in competitive matches (r=0.70) and could be used to differentiate the intermittent exercise performance of players in different playing positions and different competitive levels. Thus, wide midfielders (2057±550 m) had a higher YYIE2 test performance (p<0.05) than central defenders (1588±534 m) and attackers (1516±401 m), but not central midfielders (1764±473 m) or full-backs (1964±522 m). Moreover elite senior female players (1774±532 m) performed better than elite youth (1490±447 m; n=42), domestic (1261±449 m; n=46) and sub-elite players (994±373 m; n=19; p<0.05). Also in the stages of the season, differences occurred, with middle and end season being higher than the preparation period for elite youth female players (1767±539 and 1742±503 vs 1564±504 m) and in elite senior female players, YYIE2 test performance increased by 14% (p<0.05) after completing 4 weeks of intense training before participation in FIFA Womens World Cup.
| Original language | English |
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| Publisher | Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen |
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| Number of pages | 86 |
| Publication status | Published - 2013 |