Sammenhængen mellem kønsopdelte pubertetsstadier og fysisk præstation hos unge konkurrencesvømmere

Transkript

1 Sammenhængen mellem kønsopdelte pubertetsstadier og fysisk præstation hos unge konkurrencesvømmere The association between gender divided puberty stages and physical performance in young competitive swimmers Et bachelorprojekt af Steffen Søgaard & Søren Gravholt Juni 2014 Fysioterapeutuddannelsen University College Lillebælt

2 Intern vejleder: Tina Junge Ekstern vejleder: Hans Kromann Knudsen Antal anslag i artikel: Antal anslag i supplement: Antal anslag i figurer og tabeller: Antal anslag samlet: Antal ord i abstrakt: 309 Antal sider i bilag: 21 Denne opgave er udarbejdet af fysioterapeutstuderende ved Fysioterapeutuddannelsen i Odense, University College Lillebælt som led i et uddannelsesforløb. Den foreligger urettet og ukommenteret fra skolens side og er således udtryk for den/ de studerendes egne synspunkter.

3 Resumé Titel: Sammenhængen mellem kønsopdelte pubertetsstadier og fysisk præstation hos unge konkurrencesvømmere. Af: Steffen Søgaard, Søren B. Gravholt. Introduktion: Pubertet har indflydelse på fysisk præstation hos unge konkurrencesvømmere. Her ses både individuelle og kønsopdelte forskelle. Et højere pubertetsstadie udmøntes i en bedring i fysisk præstation. Det er derfor væsentligt at skelne mellem biologisk og kronologisk alder, når de unge konkurrencesvømmere skal trænes og vurderes på fysisk præstation. Formål: Formålet med dette studie er at undersøge sammenhængen mellem kønsopdelte pubertetsstadier og fysisk præstation hos unge konkurrencesvømmere. Materiale og metode: I dette kvantitative tværsnitsstudie, som er del 2 af paraplyprojektet Physical Performance in Young Competitive Swimmers (PPYCS), deltog 238 unge konkurrencesvømmere, 100 drenge og 138 piger i alderen De unge konkurrencesvømmere blev målt ift. hoppehøjde, gribestyrke, Andersen test, 100mFT og selvvurderet Tanner score. Resultater: Der var signifikante kønsforskelle mellem drenge og piger (p<0.05) i alle testene. Multiple lineære regressioner viste, at der ingen signifikante sammenhænge var mellem pubertetsstadier og fysisk præstation hos drenge konkurrencesvømmere. Hos piger var der en signifikant sammenhæng (p<0,05) mellem pubertetsstadier og alle de fysiske præstationer. En udvikling på et pubertetsstadie resulterede i en forbedring på 1,82 kg. i gribestyrke, en forbedring af hoppehøjde på 1,11 cm., en forbedring af VO2 max på 0,79 ml/kg/min., samt en forbedring af 100mFT på 2,89 sek. Konklusion: Der er fundet en signifikant sammenhæng for piger mellem pubertetsstadier og fysisk præstation, når der er taget højde for højde og vægt. Dette betyder, at en udvikling ift. pubertetsstadie resulterer i en forbedring af fysisk præstation hos unge pigekonkurrencesvømmere. For drengene er der ingen signifikant sammenhæng mellem pubertetsstadier og fysisk præstation hos unge konkurrencesvømmere. Perspektivering: Dette studie skaber baggrund for fremtidig undersøgelse af emnet biologisk modning. Målet kunne være at følge kohorten over tid, og derved kunne årsagsforklare de fundne sammenhænge. Nøgleord: Sammenhæng, Svømmere, Pubertet, Tanner score, Hoppehøjde, Gribestyrke, Andersen test, 100m. Fri svømmetider. Side 1 af 66

4 Abstract Title: The association between gender divided puberty stages and physical performance for young competitive swimmers By: Steffen Søgaard, Søren B. Gravholt. Introduction: Puberty impacts physical performance for young competitive swimmers, where both individual and gender divided differences is found. A development in puberty stages culminates in an increase in physical performance. It is therefore essential to distinguish between biological and chronological age, when young competitive swimmers are trained and assessed on physical performance Purpose: The purpose of this study is to examine the association between gender divided puberty stages and physical performance for young competitive swimmers. Material and method: This quantitative cross-sectional study is part 2 of the umbrella project Physical Performance in Young Competitive Swimmers (PPYCS). 238 competitive swimmers participated and the group consisted of 100 boys and 138 girls aged from The young competitive swimmers were measured in vertical jump, grip strength, Andersen test, 100mFT and self-assessment Tanner score. Results: There is found significant difference between genders in all of the test results (p<0,05). Multiple linear regressions show that there isn t significant association between puberty stages and physical performance in young competitive boy swimmers. For the girls there is found a significant association between puberty stages and physical performance in young competitive swimmers (p<0,05). With an improvement of 1 puberty stage, the HG will increase 1,825 kg, the VJ increase 1,114 cm., the VO2max will increase 0,792 ml/kg/min. and the 100mFT will improve 2,891 sec. Conclusion: A significant association was found for girls for all 4 performance tests and puberty stages, when adjusted for height and weight. Meaning that an increase in puberty stage for young competitive girl swimmers means an increase in physical performance. For young competitive boy swimmers, there wasn t found a significant association between puberty stages and physical performance. Perspective: The present study provides a basis for further investigation in this topic of biological maturation. The goal could be following the cohort over time, and thereby establish the causes behind the shown association Keywords: Association, Swimmers, Puberty, Tanner score, jump height, grip strength, Andersen test, 100m. freestyle swim times. Side 2 af 66

5 Indholdsfortegnelse INDLEDNING... 4 FORMÅL... 5 PROBLEMSTILLINGER... 5 ARTIKEL... 6 TEORI PUBERTET MAKSIMAL MUSKELSTYRKE KONDITION MATERIALE OG METODE DESIGN MATERIALE MÅLEMETODER Tanner Sexual Development (Tanner) Hoppehøjde Gribestyrke Andersens test LITTERATURSØGNING DATAINDSAMLING DATABEARBEJDNING Deskriptiv Prædiktiv RESULTATER DESKRIPTIV DATA PRÆDIKTIV DATA DISKUSSION KONKLUSION PERSPEKTIVERING REFERENCELISTE BILAGSLISTE Side 3 af 66

6 Indledning Denne opgave er skrevet som en del af paraplyprojektet: Physical Performance in Young Competitive Swimmers, forkortet PPYCS. PPYCS er styret af University College Lillebælt, Fysioterapeutuddannelsen i Odense. Projektet har til formål at undersøge fysisk præstation hos årige konkurrencesvømmere ud fra en fysioterapeutisk tilgang. Det blev startet i 2013 af 5 bachelorgrupper, som testede 5 klubber på Fyn. Projektet bliver nu, af 6 nye bachelorgrupper, udvidet med 5 nye klubber i Københavnsområdet, ligesom de tidligere omtalte fynske klubber vil blive re-testet. Dette projekt er et kvantitativt tværsnitsstudie, hvor formålet er at undersøge hvilke sammenhænge, der er mellem pubertetsstadierne og fysisk præstation hos unge konkurrence svømmere. Dette undersøges ved en standardiseret testprotokol bestående af styrke, kondition og bevægelighed. Vi har valgt at designe bacheloropgaven som en videnskabelig artikel med supplement. Artiklen er rettet mod det videnskabelige tidsskrift Scandinavian Journal of Medicine & Science in Sports. Artiklen skal i henhold til tidsskriftets retningslinjer indeholde: Title (max 120 tegn), Nøgleord (3-8 ord) Abstract (max 200 ord), Introduktion, Materiale og Metode, Resultater, Diskussion, Perspektivering (max 200 ord) og Referencer 1. Supplement indeholder: Uddybende teori, metode og materiale, diskussion, konklusion og perspektivering. 1 Side 4 af 66

7 Formål Hvilke sammenhænge ses mellem pubertetsstadierne og fysisk præstation kønsopdelt hos unge konkurrencesvømmere. Problemstillinger Hvilken sammenhæng ses mellem de 5 pubertetsstadier og hoppehøjde? Hvilken sammenhæng ses mellem de 5 pubertetsstadier og gribestyrke? Hvilken sammenhæng ses mellem de 5 pubertetsstadier og udholdenhed? Hvilken sammenhæng ses mellem de 5 pubertetsstadier og 100 m. fri svømmetider? Side 5 af 66

8 Artikel The association between gender divided puberty stages and physical performance for young competitive swimmers S. Søgaard, S. Gravholt, T. Junge, H.K. Knudsen University College Lillebælt, Department of Physical Therapy, Odense, Denmark. Puberty impacts physical performance for young competitive swimmers where both individual and gender divided differences are found. The development in puberty stages for young competitive swimmers aged culminates in an increase of physical performance. It is therefore essential to distinguish between biological and chronological age when young competitive swimmers are trained and assessed on physical performance. This study includes 238 competitive swimmers (100 boys and 138 girls). The aim of the project is to investigate the association between puberty stages and 4 physical performance tests divided in genders. The subjects are assessed in vertical jump, grip strength, Andersen test, 100mFT and selfassessment Tanner score. Multiple linear regressions are used to calculate associations. A significant relationship (p< 0,05) is found for girls for all 4 performance tests when adjusted for height an weight. This shows an increase in puberty stages for young competitive girl swimmers means an increase in physical performance. For young competitive boy swimmers, no significant association between puberty stages and physical performance was found. Introduction Physical ability such as strength in the upper and lower body, flexibility, fitness and coordination (Olbrecht, 2007), and anthropometric factors such as height, weight, hand and foot length and breast development are among the factors that have impact on the performance of young competitive swimmers (Geladas et al., 2005). These factors influence the performance individually, but are at the same time mutually dependent (Lätt et al., 2009). In addition, it is assumed that puberty has an impact on either the physical or anthropometric factors, or both. This is supported by a study of Lätt et al., which displays that the link between performance and puberty depends on the biomechanical and physical factors (Lätt et al., 2009). Side 6 af 66

9 Reflections about puberty and puberty stages are therefore essential to consider in the training of young competitive swimmers in order to optimize performance. The Swimming Union and Team Denmark have jointly prepared an Age-related Fitness Concept (ATK), that divides swimmers into 5 age groups, as these groups need different foci in the training. The groups span the ages of years, taking the puberty into account, since the swimmers go through an individual development during this period. Furthermore the swimmers in this age span are showing a big difference between the genders (Hinge and Sørensen, 2008). This is expressed in the different in height and strength increase of the genders (Madsen, 2011). ATK recommends that there are made plans for the individual swimmers in this period (Hinge and Sørensen, 2008). Nevertheless, in the division of the training groups the biological age is not taken into account, only the chronological age. For physiotherapists and swim coaches to chose focus areas for swimmers it is essential that they know the impact from the different puberty stages on the performance, considering that there can be areas that develop earlier or later in relation to the puberty stages. In Denmark, there is limited knowledge about puberty conditions for Danish adolescents, and especially the area of development and growth is poorly examined. Therefore, it is difficult to investigate what is applicable to puberty and what influences young people's development ( Forskning - Rigshospitalet ). The study Mero et al. examines the differences between biological and chronological age. The study is looking on endurance, strength and speed capacity on two groups. 12 boys aged classified as promising junior athletes was the athletic group (AG), and 9 normally active boys in the control group. The two groups had the same chronological age, but the AG group scored an average of 1,1 higher in the biological age. The study shows a greater performance of the AG group than the control group. This could be a result of two factors, the training background or the more advanced biological age (Mero et al., 1990). A swimmer s puberty stage has a high correlation with swimming times. In the study Lätt et al. a group of young swimmers are followed for 2 years. This longitudinal study shows that a higher average rating in Tanner score gives a faster average swim time (Lätt et al., 2009). Studies of Geladas et al. and Lätt et al. support this. It is showed that puberty has an influence on the swimming Side 7 af 66

10 performance. A 0,7 advance in tanner resulted in an improvement of 7,1 sec in 400 meter swimming time, second year the results was 0,5 advance in tanner lead to an improvement of 12,6 in swimming time (Lätt et al., 2009). In these studies, the results are found by analyzing an average puberty score (Tanner Score) compared with the various physical performances and biological differences. As described above, the physical and anthropometric factors impact the swimming performance. Also, there is a connection between puberty stages and swimming times. Therefore our project is based on the assumption that puberty is an important factor to include in the planning of swimming training for young people. Our approach will be to divide the population according to genders, and into the 5 puberty stages. Then we will analyze the physical performance of the groups to see if there is a link between the two puberty and performance. That study and supposed association is interesting for coaches and physiotherapists providing them with knowledge on physical performance in the period of puberty, which enables them to plan the training better for the individual swimmer. The aim of this project is to investigate the association between puberty stages and 4 physical performance tests divided in genders. The physical performance tests include Vertical jump height, Andersen s fitness test, handgrip strength, and the swimming times on a 100-meter distance. In addition, they will make a self-assessed test the Tanner Sexual Development test. Materials and Methods This study is performed as a cross-sectional design with a quantitative approach. The study is part 2 of the umbrella project Physical Performance in Young Competitive Swimmer (PPYCS). Part 1 involved 4 bachelor groups, and part 2 involves 6 bachelor groups, all with different focus on the subject. The goal of PPYCS is to create parameters on this specific population, to allow future research. The end product of PPYCS is a cohort with several crosssectional studies. Subjects The population in this study consists of young competitive swimmers from both Funen and Zealand. The participating swimmers come from five clubs on Funen, who where tested in part 1, and the Zealand based swimmers came from 8 of the biggest clubs in the Copenhagen area. The inclusion criteria for the participants were to be a competitive swimmer aged Exclusion criteria were Side 8 af 66

11 lack of consent form parent or guardian, injuries that affects their physical performance, fever or penicillin in the last 2 weeks and lack of meal or asthma medicine. With these criteria the population was made up of 238 competitive swimmers between years old and the group consisted of 100 boys and 138 girls. Vertical Jump Vertical Jump (VJ) where assessed using a belt attached to a measuring tape strapped to the waist. This was attached to the ground with duct tape. The subjects where positioned close to the tape. The jumping height was then calculated, by the difference between standing position and the peak of the jump. One test jump was allowed, followed by minimum 3 valid jumps. VJ where found comparable with Countermovement Jump (CMJ). Rate of Force Development in lower extremities where found to have a significant correlation with CMJ (McLellan et al., 2011). The inter- reliability of CMJ where investigated by Nuzzo et al, and found to be 0,88 for women and 0,94 for men (Nuzzo et al., 2011). Handgrip The handgrip test (HG) is measuring maximum grip strength in kg. Using a SAEHAN Digital Hand Dynamometer that calculates in kilogram. The subject is positioned with a fully extended arm along the body. Both hands are tested followed by 1-minute intermission before a retest. Arm and dynamometer is not allowed to touch the body during the test. The handgrip strength is shown in the study Wind et al to correlate significantly with total muscle strength concerning adolescents and young adults (Wind et al., 2010). The reliability was in Shechtman et al. shown to be high (Shechtman et al., 2005). Andersen test The Andersen test is measuring the aerobic capacity of the test subject, using a 20-meter course one lap being 2x40 meters. The test time is 10 minutes, with the test subject running 15 seconds followed by 15 minutes rest. At every turn the subject has to touch the floor behind the line. The correlation between Andersen test and VO 2max was found high in the two studies Andersen et al. and Ahler et al. These two studies also found the reliability to be high (Ahler et al., 2012; Andersen et al., 2008). The test results are then converted to VO 2max, for a more useful and comparable data. VO!!"# = distance 5.92 gender boys = 0; girls = 1. The equation is developed in the study Andersen et al, (Andersen et al., 2008). Side 9 af 66

12 Tanner Sexual Development test Tanner Sexual Development test (Tanner) is a self-assessment puberty scoring tool. It divides the subjects into 5 developments stages, from before puberty until fully matured. The subject is being shown a questionnaire containing a picture and a corresponding text for each stage. The subjects then have to choose the picture fitting their maturity stage. Boys are divided based on pubic hair, and girls based on pubic hair and breast size. It is essential that the test is performed anonymously because the results are sensitive for the subjects. The Tanner score is found as a valid and reliable method to assess sexual maturity in the study Leone et al., (Leone and Comtois, 2007). Swimming time The swimming time is the official individual time in 100 freestyle (100mFT), and is obtained from the database OctoOpen ( OctoOpen, n.d.) handgrip test. To compare difference in genders the independent T-test was used. Except on puberty stages were median was used, because of the different scale. Multiple linear regressions (MLR) were used to assesse the association between biological age and physical performance. The assumptions for MLR were assessed. Puberty stages were set as the independent variable and the physical performance as the dependent variable. Height and weight where set as confounders (Hicks, 2009). Results Descriptive data of puberty, height, weight and physical performance tests are shown in Table 1. There is significant difference between genders in all 4 physical performance tests, height and weight except on puberty stages. The boys generally scores higher in the physical performance test, shown in handgrip (6,04 kg), vertical jump (5,6 cm), aerobic capacity (8,33 ml/kg/min) and swim faster in 100 mft (-4,82 sec). Statistic Procedures IBM SPSS Statistics 22 (SPSS Inc., Chicago, IL, USA) was used to process and analyze the data. All data was first assessed to be normal distributed, using a Q-Q plot, Box-Plot and a histogram. A paired T-test was used to compare mean values in right and left hand in Side 10 af 66

13 Table 1. Descriptive statistic of the subjects Mean ± SD Variabler Boys N=100 Girls N=138 Combined N=238 Mean dif. 95% CI P Puberty(Tanner) * Height (cm) 166,15 ± ,74 ± 8,76 162,98 5,41 2,86 ; 7,97 0,000 Weight (kg) 53,02 ± ,12 ± 9,58 51,4 2,91 0,27 ; 5,54 0,031 Handgrip (kg) 34,55 ± 10,28 28,51 ± 6,31 30,96 6,04 3,91 ; 816 0,000 Vertical jump (cm) 44,47 ± 7,09 39,22 ± 5,13 41,48 5,6 4,09 ; 7,22 0,000 VO2 max(ml/kg/min) 56,11 ± 2,48 47,78 ± 2,67 51,4 8,33 7,62 ; 9,03 0, mft(sec) # 67,72 ± 8,30 72,54 ± 8,59 71,01-4,82-7,08 ; -2,57 0,000 * Calculated as median ; boys N=99 girls N=135 ; boys N=94 girls N=120 ; # boys N=94 girls N=131 Figure 1. Difference between genders on distribution of tanner stages boys girls 0 As shown in Figure 1 the Tanner stages in both genders are distributed with a small population in stage 1 and 5, and in all stages population of girls are bigger than for boys. The genders are distributed equally throughout stages, which is consistent with table 1, that shows no significant difference between genders. The assumptions for multiple linear regressions were fulfilled. Multiple linear regression models for gender divided puberty stages and the 4 physical performance tests are shown in Table 2 and 3. Table 2 Association between puberty stages and HG, VJ, VO2max and 100mFT for boys Dependent Variable B 95 % CI P-value R 2 HG Puberty -0,009-1,64 ; 1,63 0,992 Height 0,296 0,09 ; 0,51 0,006 Weight 0,541 0,31 ; 0,775 0,000 Constant -43,227-68,27 ; -18,18 0,001 0,767 VJ Puberty 0,221-1,52 ; 1,96 0,802 Height 0,144-0,78 ; 0,36 0,201 Weight 0,28 0,03 ; 0,52 0,028 Constant 5,347-21,21 ; 31,90 0,69 0,457 VO2 max Puberty 0,366-0,41 ; 1,14 0,352 Height 0,124 0,02 ; 0,23 0,02 Weight -0,061-0,17 ; 0,53 0,292 Side 11 af 66

14 100 mft Constant 37,649 25,20 ; 50,10 0,000 Puberty -0,676-2,43 ; 1,08 0,446 Height -0,355-0,58 ; -0,13 0,003 Weight -0,199-0,46 ; 0,06 0,461 Constant 139, ,42 ; 166,27 0,000 0,18 0,602 The results from boys Table 2 show no association between puberty and performance in boys. The height and weight shows a higher association with performance. Table 3 Association between puberty stages and HG, VJ, VO2max and 100mFT for girls Dependent Variable B 95 % CI P-value R2 HG Puberty 1,825 0,99 ; 2,67 0,000 Height 0,063-0,07 ; 0,2 0,352 Weight 0,32 0,2 ; 0,44 0,000 Constant -3,212-20,24 ; 13,81 0,71 0,625 VJ Puberty 1,114 0,04 ; 2,19 0,042 Height -0,025-0,2 ; 0,15 0,775 Weight 0,064-0,1 ; 0,23 0,435 Constant 36,68 14,58 ; 58,78 0,001 0,08 VO2 max Puberty 0,792 0,20 ; 1,38 0,009 Height 0,107 0,01 ; 0,20 0,031 Weight -0,147-0,24; 0,05-0, mft Constant 35,566 23,47 ; 47,67 0,000 0,112 Puberty -2,891-4,34 ; -1,44 0,000 Height -0,324-0,56 ; 0,09 0,007 Weight -0,022-0,24 ; 0,19 0,838 Constant 134,42 104,69 ; 164,15 0,000 0,415 The results from girls Table 3 shows an improvement of 1 puberty stage, the HG will increase 1,825 kg, the VJ increase 1,114 cm., the VO2max will increase 0,792 ml/kg/min. and the 100mFT will improve 2,891 sec. Side 12 af 66

15 The associations between puberty and the physical performance for girls are all significant (<0,05) From the value R 2 is it possible to tell how much a change in physically performance could be explained by development in puberty. Puberty and the confounders can explain 63% of HG, 8% of VJ, 11% of VO2max and 41% of 100mFT. Discussion The aim of this project is to investigate the association between puberty stages and 4 physical performance tests divided in genders. A significant association is found for girls for all 4 performance tests when adjusted for height an weight. This means, that an increase in puberty stage for young competitive girl swimmers shows an increase in physical performance. For young competitive boy swimmers, no significant association (p > 0,005) between puberty stages and physical performance is found. A significant difference between genders is found. Boys score significantly higher in physical performance than girls (p < 0,005). The results for girls show a R 2 value between 8-63%, when examine puberty impact on physical performance. It is especially low in VJ and VO 2 max, meaning that in these test most of the improvement is a result of randomness. Changes of physical performance can best be explained by puberty in HG and 100mFT. To find external validity for this study we have looked at other similar studies. It has not been possible to find studies using same structure in design and method. Therefore, to make comparisons and to validate our study and results we have selected studies with compatible methods and aims. These studies are for example not using puberty stages as the independent variable, but instead looking at physical variables compared to swimming time. Some are using chronological age as the independent variable. A study examining competitive girl swimmers over 2 periods shows that an advance in mean tanner resulted in an improvement of mean 400 meter swimming time. First year 0,7 advance in tanner resulted in an improvement of 7,1 sec in swimming time, second year the results was 0,5 advance in tanner leads to an improvement of 12,6 in swimming time (Lätt et al., 2009)This coincides with the present study where an improvement of 1 puberty stage leads to an improvement of 2,891 sec in 100mFT. Lätt et al are using the same tanner scoring method. They are using the 400-meter swimming time; which includes more turns and requires more aerobe capacity. Also they are following the same subjects over time, Side 13 af 66

16 compared to the present study, which is a cross-sectional study. The Lätt et al study is using the mean value (Lätt et al., 2009). This has to be taken into account when the studies are compared. We still think it is possible to compare, because the to studies are using the puberty and physical performance as variables. As shown in Table 1 the mean value of GS in the present study is 34,55 ± 10,28 kg and 28,51 ± 6,31 kg respectively for boys and girls. In the study Garrido et al. it shows a GS score of 46.6±9.73 kg and 32.83±5.45 kg respectively for boys (14.96±0.5 year) and Girls (12.53±0.49 year). The higher score in the Garrido study could be a result of a difference in test methods and the higher mean age of the population(garrido et al., 2012). The increase in age resulting in increase in GS is also shown in the present study in Table 1. The VJ presented in Tabel 1 (41,48 cm) can be compared to the VJ results in Potdevin et al. They showed a lower mean VJ at 28,92 ± 4,82. The subjects in Potdevin et al are not instructed to have their arms at the hip during jump which is different from the method in the current study that allows arm swing during jump. It is shown that arm swing increases the VJ (Nuzzo et al., 2011). Also the study Potdevin only included both genders age in tanner stage 3-4. The age and method difference in the test could explain the 12,56 difference (Potdevin et al., 2011). The VO2 max results are a calculated result from the AT, because it is used for comparison with VO2 max and puberty stages. This study is made with a population of swimmers and therefore it could be more precise to have a VO2 max test in water, measured from a swimming performance. But in the study by Wakayoshi et al. there it is showed that VO2 max measured on land could be compared by VO2max measured in water (Wakayoshi et al., 1993). The problem with the comparison is whether the swimmers are used to run and thereby would get a better result (higher VO2 max) compared to swimming in water. The cross-sectional design limits the ability to explain the causation between puberty stages and physical performance. The nature of this design only provides a momentary picture of the sample and therefor it is possible to talk about association and reference values, but difficult to compare values with other study designs. A cohort study could have shown the individual development of each swimmer and provide causations between puberty and physical performance. Therefore it is possible Side 14 af 66

17 to provide more reliable results about biological age versus chronological age when the full cohort of PPYCS is finished. Another challenge with the results giving a momentary picture is possible differences in the peak of physical performance during the swimmers season. Therefore the results could vary depending on the test date. This could have an effect of the outcome. Puberty classification is essential for this study, and the test selected was the tanner sexual development scoring. Another method to measure biological age, would be taking the subjects to closed surroundings at an exam with the doctor. Because the present study method had a pragmatic approach that shows in a limitation of time, money and surroundings. The Tanner test is assessed to be the most compatible method. This I supported by the study Leone et al, which shows a high correlation between a doctor exam and Tanner method (Leone and Comtois,2007). One problem with the test could be the subject s aversion against classifying them in stage 1 ore 5. It could be considered to use height as a marker for puberty stage. This is also supported by the advice from Danish sports federation (Madsen, 2011). This shows in the present study in Figure 2 where height has a significant impact on physical performance (only regarding HG, VJ and 100mFT) and puberty doesn t have. When the test results where investigated, there where several girls whom had reached their menstrual period, but still scored themselves in stage 1 or 2 on tanner. This shows that there could be some problems with the self-assessment scoring method and supports that there is some bias in using tanner too measure biological age. The testing position is important for the reliability of the results in GS (Liao et al., 2013). The time of the day might also influence the GS, where a significant increased GS was found during the afternoon compared to the morning test slot(innes, 1999). Individual warm-up by the subjects is difficult to prevent, and could have effected the results. 10 min warm-up has in the study Innes et al been shown to increase the GS (Innes, 1999). It wasn t possible to locate other studies using the same device at used in the present study (SAEHAN digital hand dynamometer). But there was found similar devices to prove the validity and reliability of the method. The 100mFT results are obtained from the database Octoopen. This database is a homepage with the official swimming times, from competition in Denmark ( OctoOpen, ). Side 15 af 66

18 In this study all swimmers without an official time from the database, were excluded to proceed in the statistics. Therefore some of the swimmers that are being excluded could have given a different outcome to the results. It could be assumed that the swimmers who do not have an official time, is the youngest and slowest in the project. If this is a correct assumption the results of physical performance would be drawn down. The official times where all obtained from competitions the past year, therefore, it is a possibility that swimmers have improved their time since. Based on the theory presented in (Madsen, 2011) on the present population of young competitive swimmers. It is shown that chronological age alone cannot be a precise marker for physical performance. For example 2 young swimmers at the same chronological age, could have different biological age, and thereby different physical performance. In the present study it is shown that biological age could be an alternative marker. Based on the association found between girls biological age and physical performance. 16 different physiotherapists collected the data in the PPYCS. This could lead to possible differences in approaches to the tests methods, and thereby compromising the reliability. Another possible bias that could compromise reliability of the study, are the different test surroundings. All the swimming clubs are tested at different surroundings. Involving factors like temperature, wind, light, space, surface and etc. that could influence the physical performances. The fact that the study includes a population of 238 subjects is strengthening the validity of the study. The population is a great representative sample of the young competitive swimmers In Denmark. When the population is divided in gender and puberty stages. The boys have a 28,6 % smaller population than girls, which resulted in a small distributed population in stage 1 and 5. This resulted in some difficulty examining the association with physical performance, and could be one of the reasons that p>0,05 in all 4 physical performance tests for boys. A way to avoid the above mentioned imbalanced population, could be a more strict selection of the test sample. Thereby securing an equal division, containing 20 swimmers in each stage. Perspective The present study provides a basis for further investigation in this topic of biological maturation. The goal could be following the Side 16 af 66

19 cohort over time, and thereby establish the causes behind the shown association. Also this could allow us to follow the same population during their maturation. Another goal could be to investigate possibility of height being a marker of puberty maturation. Acknowledgements Thanks to Tina Junge (main supervisor) and Hans Kromann Knudsen (second supervisor) for guiding and advising during the process of this project. Thanks to Dorte Gravholt and Kathrine Gravholt for grammatical correction of the study. Furthermore we will like to thank the participating swimming clubs, coaches, swimmers and their parents for good collaboration. Key words Swimming, Puberty Tanner score, Vertical jump, Grip strength, Andersen test, 100m. Freestyle swimming time, association. References Ahler, T., Bendiksen, M., Krustrup, P., Wedderkopp, N., Aerobic fitness testing in 6- to 9-year-old children: reliability and validity of a modified Yo- Yo IR1 test and the Andersen test. Eur. J. Appl. Physiol. 112, doi: /s Andersen, L.B., Andersen, T.E., Andersen, E., Anderssen, S.A., An intermittent running test to estimate maximal oxygen uptake: the Andersen test. J. Sports Med. Phys. Fitness 48, Forskning - Rigshospitalet [WWW Document], n.d. URL LINGER/Enheder+paa+tvaers/Boern+og +unge/viden+om/pubertet/forskning.htm?siu=true (accessed ). Garrido, N.D., Silva, A.J., Fernandes, R.J., Barbosa, T.M., Costa, A.M., Marinho, D.A., Marques, M.C., High level swimming performance and its relation to non-specific parameters: a cross-sectional study on maximum handgrip isometric strength. Percept. Mot. Skills 114, Geladas, N.D., Nassis, G.P., Pavlicevic, S., Somatic and physical traits affecting sprint swimming performance in young swimmers. Int. J. Sports Med. 26, doi: /s Hicks, C., Research methods for clinical therapists: applied project design and analysis, 5th ed. ed. Churchill Livingstone/Elsevier, Edinburgh ; New York. Hinge, M., Sørensen, L., Aldersrelateret træning i svømning. Dansk Svømmeunion, Team Danmark. Innes, E., Handgrip strength testing: A review of the literature. Aust. Occup. Ther. J. 46, doi: /j x Lätt, E., Jürimäe, J., Haljaste, K., Cicchella, A., Purge, P., Jürimäe, T., Physical development and swimming performance Side 17 af 66

20 during biological maturation in young female swimmers. Coll. Antropol. 33, Leone, M., Comtois, A.S., Validity and reliability of self-assessment of sexual maturity in elite adolescent athletes. J. Sports Med. Phys. Fitness 47, Liao, W.-C., Wang, C.-H., Yu, S.-Y., Chen, L.-Y., Wang, C.-Y., Grip strength measurement in older adults: A comparison of three testing positions. Australas. J. Ageing. doi: /ajag Madsen, J., Aldersrelateret træning : for børn og unge. Danmarks Idræts-Forbund, Brøndby. McLellan, C.P., Lovell, D.I., Gass, G.C., The role of rate of force development on vertical jump performance. J. Strength Cond. Res. Natl. Strength Cond. Assoc. 25, doi: /jsc.0b013e3181be305c Mero, A., Kauhanen, H., Peltola, E., Vuorimaa, T., Komi, P.V., Physiological performance capacity in different prepubescent athletic groups. J. Sports Med. Phys. Fitness 30, Moir, G., Shastri, P., Connaboy, C., Intersession reliability of vertical jump height in women and men. J. Strength Cond. Res. Natl. Strength Cond. Assoc. 22, doi: /jsc.0b013e318185f0df Nuzzo, J.L., Anning, J.H., Scharfenberg, J.M., The reliability of three devices used for measuring vertical jump height. J. Strength Cond. Res. Natl. Strength Cond. Assoc. 25, doi: /jsc.0b013e3181fee650 OctoOpen [WWW Document], n.d. URL (accessed ). Olbrecht, J., The science of winning: planning, periodizing and optimizing swim training. F&G Partners, Partners in Sport, Antwerp. Potdevin, F.J., Alberty, M.E., Chevutschi, A., Pelayo, P., Sidney, M.C., Effects of a 6-week plyometric training program on performances in pubescent swimmers. J. Strength Cond. Res. Natl. Strength Cond. Assoc. 25, doi: /jsc.0b013e3181fef720 Shechtman, O., Gestewitz, L., Kimble, C., Reliability and validity of the DynEx dynamometer. J. Hand Ther. Off. J. Am. Soc. Hand Ther. 18, doi: /j.jht Wakayoshi, K., Yoshida, T., Udo, M., Harada, T., Moritani, T., Mutoh, Y., Miyashita, M., Does critical swimming velocity represent exercise intensity at maximal lactate steady state? Eur. J. Appl. Physiol. 66, Wind, A.E., Takken, T., Helders, P.J.M., Engelbert, R.H.H., Is grip strength a predictor for total muscle strength in healthy children, adolescents, and young adults? Eur. J. Pediatr. 169, doi: /s Side 18 af 66

21 Teori Dette afsnit har til formål at danne en teoretisk baggrund for det valgte formål: Pubertetsstadier og fysisk præstation hos unge konkurrence svømmere. Pubertet Puberteten giver sig udtryk ved kønsspecifikke fysiske forandringer, som er et resultat af hormonelle ændringer i hypothalamus. Hormonerne starter en øget udskillelse af kønshormoner (østrogen for piger og testosteron for drenge), der resulterer i øget vækst af æggestokke og testikler. Samtidig starter det også vækstspurten, der indtræffer i det sidste år af kønsmodenheden og de 2 efterfølgende år. De første tegn på puberteten ses i gennemsnitsalderen 10,3 hos piger og 11,8 ved drenge. Dette er dog med en variation på ca. 2 år på begge sider af middelværdien ( Pubertet - Rigshospitalet ). Målgruppen i dette projekt er årige svømmere, hvor netop disse pubertetsforandringer spiller en betydelig rolle for den enkelte svømmer. Individuel udvikling I pubertetsperioden er der udfordringer ved at generalisere på aldersgrupper, da udviklingen er individuel og sker på forskellige alderstrin for den enkelte dreng eller pige. Det giver sig til udtryk ved en forskel på biologisk- og kronologisk alder. Dette ses ved en sammenhæng mellem naturlig fysisk udvikling og 3 faktorer. Ændringen af kropsvægt og størrelse, den neuromuskulære og den generelle fysiske kapacitet. Hvis man blot kigger på kronologisk alder, når der skal trænes målgrupper, så kan svømmerne have forskellig biologisk alder og derved forskellig fysisk kapacitet (Madsen, 2011 s. 6-8). En markør, som kan anvendes til begge køn, er maksimal højdetilvækst, også kaldet peak heigth velocity (PHV). Denne markør kan sige noget om deres fremskredne biologiske modning/alder. Hos pigerne er menarch-alder en bedre indikator for biologisk modning/alder (Madsen, 2011 s. 7). Kønsopdelt udvikling Der ses store forskelle i udviklingen af drenge og piger, når man kigger på den kønsopdelte udvikling i pubertetsperioden. I den præpubertære periode har begge køn ens vækstmønstre, som kan ses både ved højde og styrke (Madsen, 2011 s. 7-11). Dette ændres når begge køn kommer i den pubertære periode. Her ses der forskel på fx styrkeøgning, hvor drenge har en væsentlig større Side 19 af 66

22 øgning end pigerne. Dette er primært pga. drengenes høje produktion af testosteron. Pigerne derimod har en større vækst af fedtmasse end drengene pga. øget produktion af østrogen. Pigernes PHV kommer oftest 2 år før drengene og er derfor i en tidligere alder længere fremme i biologisk udvikling end aldersvarende drenge. Dette ses også i inddelingen af svømmere i ATK-svømning, hvor f.eks. målgruppen år piger og drenge år anbefales at træne sammen (Hinge and Sørensen, 2008 s. 9-16). Følgende nedenstående studier har kigget på forskellige kønsmæssige forskelle i puberteten: De føromtalte neuromuskulære forskelle hos unge piger og drenge, der ses som en følge af PHV, betyder en forøgelse af styrke og koordination hos unge drenge men ikke for unge piger. Dette giver sig udtryk ved håndstyrke, hoppehøjde, længdespring, sprint og balance (Hewett et al., 2004). Studiet Kellis et al understøtter denne teori. Her ses det, at 10 kvindelige basketball spillere ikke opnår en forøgelse i hoppehøjde følgende deres alder, hvorimod drenge opnår en markant forøgelse (Kellis et al., 1999). Samtidig giver denne neuromuskulære ændring en nedsat kontrol af knæet hos piger. Dette udtrykker sig ved deres landing, hvor den totale mediale bevægelse af knæet samt underbenets maximale valgus vinkel er større end hos drenge (Hewett et al., 2004). Dette kan skyldes den øgede mængde af østrogen hos piger i puberteten, som har en påvirkning på den mekaniske funktion af ACL samtidig med den nedsatte neuromuskulære styrke hos piger. Den manglende neuromuskulære aktivitet ses specielt som nedsat hamstrings styrke i forhold til quadriceps styrke (Wild et al., 2012). I studiet af Vänttinen et al. lavet på unge fodbolddrenge ses der, at vækstspurten i gennemsnit indtræder ved 14,1 år. Her vises det også, at muskeltilvæksten i 15 års alderen stiger med 25 % som et resultat af deres naturlige fysiske udvikling. Ydermere ses der, at året efter den kraftigste vækst i højde (vækstspurten) ses den kraftigste stigning af muskelmassen. Dette betyder, at man i denne periode vil have lavere muskelstyrke ifht. højde, når højdevæksten er større end væksten i muskelmassen. Undersøgelsen viste også at muskelmassen i den samlede kropsvægt stiger fra 47.8%, når du er 11 år til 51.9%, når du er omkring 17 år. Dette forklares ved den øgede udskillelses af testosteron (Vänttinen et al., 2011). Side 20 af 66

23 Overført til målgruppen unge konkurrencesvømmere betyder den store forskel på kønnene, at pigerne tidligere får en biologisk modning. Senere i puberteten udvikles drengene muskulært hurtigere end piger, og de vil derfor overhale pigerne på fysiske præstationer. Maksimal muskelstyrke I dette projekt undersøges den fysiske præstation hos unge konkurrencesvømmere. En væsentlig del af den fysiske præstation er maksimal muskelstyrke. Specielt når testpersonerne udfører gribestyrke, er denne definition vigtig. Maksimal muskelstyrke defineres som, det moment en given muskel gruppe kan producere omkring de involverede led. Den maksimale muskelstyrke afhænger af graden af overlap mellem myosin og aktin, der påvirker forholdet mellem muskelspænding og muskellængde. Hvis der er et stort overlap mellem myosin og aktin, betyder det et større moment og derved en højere maksimal muskelkraft. Dette kan forklares ud fra længdespændingsrelationen. Figur 2 - Længde-spændingsrelationen (Beyer and Klinge, 2011 s. 44). Figur 2 viser, at den totale muskelkraft ved en given muskellængde består af summen af både den passive og aktive kraftudvikling. Den passive kraft udvikles af stræk på de passive elementer omkring det givne led. Dette betyder at den maksimale muskelstyrke er størst i midten af bevægebanen, da det er her, myosin og aktin har det største overlap. Derfor kan udgangsstillingen Side 21 af 66

24 for måling af den maksimale muskel- styrke i f.eks. håndkraft testen have betydning for resultatet (Beyer and Klinge, 2011 s ). Rate of Force Development (RFD) Figur 3 Explosiv muskelstyrke (Beyer and Klinge, 2011 s. 52) RFD er defineret ved en given muskels evne til at udvikle maksimal acceleration over kort tid. Det forklares ud fra Figur 3., hvor RFD udregnes ved Δ-kraft/Δ-tid. Det betyder, at RFD kan bestemmes som hældningen på kraft-tids kurven. Det betyder, at en stejl hældning på kurven er udtryk for en stor eksplosiv muskelkontraktion. Denne evne bestemmes af motorneuronernes fyringsevne samt fordelingen af muskelfibre typer. Der findes 3 typer af muskel fibre, type 1(fast twitch) og type 2a og x(slow twitch). Fast twitch er den type med det højeste RFD, og det er dermed mængden af fast twitch i forhold til slow twitch, der afgør, om en person kan udvikle en stor kraft på kort tid. Det kan specielt overføres til VJ testen, hvor det kræves af testpersonerne, at der udvikles en stor RFD i specielt quadraceps ved hoppet. (Beyer and Klinge, 2011 s ; Bojsen- Møller, 2011 s ). Kondition En del af den fysiske præstation, som bliver målt og vurderet i dette studie, er den maksimale iltoptagelse(vo 2 max). Denne defineres som kroppens evne til at optage ilt i musklerne. VO 2 max er afhængig af både centrale og perifere faktorer i kroppen. De centrale skal forstås som hjertets evne til at transportere blodet og dermed ilten ud til de arbejdende muskler. Dette måles ved minutvolumen. De perifere faktorer består af musklernes og det omkringliggende vævs evne til at optage og udnytte ilten. Ved træning over tid kan man derved forbedre VO 2 max ved enten at øge Side 22 af 66

25 minutvolumen eller øge antallet af kapillærer og mitokondrier i musklerne. Denne ændring opnås over måneder med hård træning, hvorefter forøgelsen vil bliver mindre og nærmer sig et plateau. Hvis man ser på det perifere system omkring musklerne, arbejdes der enten aerobt eller anaerobt. En persons evne til at arbejde inden for disse typer af arbejde afhænger af kroppens fordeling af muskelfibre typer. Som beskrevet tidligere i afsnittet findes der slow twitch og fast twitch. Slow twitch er de mest udholdelige og er dermed mængden af denne type, der er med til at bestemme VO 2 max. Hvis dette overføres til de unge konkurrencesvømmerne i dette projekt, er det specielt dette forhold mellem muskelfibertyperne, der bestemmer deres fysiske præstation. Der er i hoppehøjde og gribestyrke specielt brug for fast twitch og i andersentesten er der brug for flere slow twitch muskelfibre. Derfor vil der for svømmerne være et behov for et sammenspil mellem de to typer og dermed et behov for både aerob og anaerob træning (Beyer and Klinge, 2011 s ). Materiale og metode I følgende afsnit vil der blive redegjort for projektets design, materiale, målemetode, dataindsamling, etiske overvejelser, litteratursøgning og databearbejdning. Design Dette studie er en kvantitativ tværsnitsundersøgelse, hvor sammenhænge for en aktuel population undersøges. I dette tilfælde de årige konkurrencesvømmere i Danmark. Ud fra tværsnittet kan den prædikative fysiske præstation for f.eks. en svømmer i pubertetsstadie 2 udregnes. Da der er tale om et prævalensstudie, er det ikke muligt at forklare årsagssammenhænge, men derimod give et umiddelbart billede af studiepopulationens fordeling (Juul, 2012 s ). Tværsnitsstudier er rangereret som evidensniveau III, styrke C (Bak Andersen and Matzen, 2010 s. 57). Fokus i dette studie er at se, om der er sammenhæng mellem pubertetsstadier og 3 fysiske test samt svømmerens 100 mft. De unge konkurrencesvømmere bliver testet i Vertical hoppehøjde, Andersen konditionstest og Håndtrykskraft, desuden udfylder de en selvvurderet Tanner Sexual Development. Projektet udmunder i en statistisk analyse af resultaterne, hvor der anvendes en Multiple Lineære Regression (Bak Andersen and Skov Madsen, Jonna, 2010 s ). Side 23 af 66

26 Materiale Population i dette studie består af 238 unge konkurrencesvømmere fra både Fyn og Sjælland. Klubberne, som er blevet inviteret, er 5 fynske klubber og 8 af de største klubber i og omkring Københavnsområdet. Der er 100 drenge og 138 piger med i projektet. Deltagerne i projektet er blevet udvalgt ud fra en række inklusions- og eksklusionskriterier Figur 5. På Figur 4 er et flowchart over antal deltagere i projektet, og ydermere hvordan udvælgelsen af populationen har været efter inklusions- og eksklusions kriterier til de enkelte test. Figur 4: Flowchart diagram over antal deltagere. 330 blev inviteret til at deltage 81 udeblev på selve testdagen 250 mødte op på testdagen 12 blev ekskluderet pga. skader eller manglende samtykke 238 gennemførte gribestyrke 24 blev ekskluderet 238 deltog i testene 234 gennemførte hoppehøjde 225 havde en off. 100 mft tid 214 gennemførte Andersen test Side 24 af 66

27 Figur 5: Inklusions- og eksklusionskriterier Inklusionskriterier Alder mellem år Er på et konkurrence- eller talenthold i svømning Eksklusionskriterier Manglende samtykke Skader der kan påvirke deres fysiske præstation Uregelementeret påklædning Andersen test: Pencillin inden for de sidste 14 dage Feber inden for de sidste 14 dage Har ikke spist på selve testdagen Har ikke taget astmamedicin før testen, hvis dette er normalt inden fysisk aktivitet Målemetoder Tanner Sexual Development (Tanner) Tanner score er en pubertets test, der har til formål at inddele børn og unge i udviklingsstadier. Testen består af et spørgeskema, der viser 5 stadier fra før pubertet til voksen. Hvert stadie har et billede og en tekst for hvert stadie til hvert køn. Testpersonen skal vælge billede og dertil hørende tekst, der passer til hans eller hendes udvikling. For drenge går inddelingen på kønsbehåring og penisudvikling, og for piger er det kønsbehåring og bryststørrelse. Det er vigtigt, at testen er anonym. Derfor skal skemaet efter instruktion om scoring udfyldes i et aflukket rum og afleveres med siden vendt ned. På den måde kan hverken tester eller andre børn se svarene (se bilag 1-3). Validitet og Reliabilitet I et studie af Leone et al. undersøger man, om selvvurderet Tanner er et validt redskab til at måle seksuel modenhed. 24 mandlige og 23 kvindelige atleter i alderen 12 til 17, bliver alle modenhedsvurderet af en læge og efterfølgende selvvurderet med Tanner. Der ses en høj korrelation mellem den selvvurderede Tanner og lægens vurdering, med en korrelation på 0,67-0,79 for drenge og 0,75-0,85 for piger. Side 25 af 66