| Abstract | Aim The main aim of the doctoral thesis is to describe the patterns of physical activity during high-school. Three specific goals for three independent studies (Study 1, Study 2 and Study 3) were set. Study 1 aimed to evaluate: (1) the objectively assessed physical activity (PA) patterns in urban 15-year-old male and female adolescents according to school type and (2) to assess the differences in PA between school days and weekend days. Study 2 aimed to evaluate PA, SBs and SP changes between 1st and 2nd grade of secondary school in urban adolescents. Study 3 aimed to evaluate the extent of tracking of physical activity (PA), sports participation (SP) and sedentary behaviors (SB) over 4 years of secondary school education among the Croatian Physical Activity in Adolescence Longitudinal Study (CRO-PALS) cohort. Study 1 methods In this cross-sectional study, participants were 187 secondary-school male and female adolescents (61.4% females) attending grammar and vocational schools. Patterns of PA were objectively evaluated using a multi-sensor body monitor for 5 consecutive days. Confounders assessed included biological age, socio-economic status, sum of 4 skinfolds, maximal temperature and the amount of rainfall. Study 1 results Males and females from grammar schools achieved higher total daily energy expenditure (TEE) and active energy expenditure (AEE) compared to their peers from vocational schools (TEE: 50 ± 12 kcal/kg/day vs. 47 ± 12 kcal/kg/day, p = 0.02; AEE: 23 ± 5 kcal/kg/day vs. vocational = 21 ± 6 kcal/kg/day, p = 0.04). No differences in time spent in light (LPA), moderate (MPA) or vigorous (VPA) physical activity were noted between the two groups (p = 0.16–0.43). Next, a significant decline in TEE and MPA between school days and weekends was observed (p< 0.001 and p = 0.02, respectively), while VPA remained the same throughout the week (p = 0.76). Weekly patterns of PA did not show differences by school type or gender (p for interactions = 0.21–0.50). In addition, significantly lower amount of MPA was accumulated during weekends compared to school days, resulting in lower TEE, regardless of school type or gender. Study 1 conclusion Policies and strategies on PA in adolescents should focus vocational schools and weekend days. Study 2 methods In this one year follow-up study, participants were 81 secondary-school students (28 boys and 53 girls) aged 15.5 years at the baseline. PA was assessed with the SenseWear Armband multi-sensor activity monitor, while SBs were assessed by using School Health Action, Planning and Evaluation System (SHAPES) physical activity questionnaire. SHAPES questionnaire was supplemented with 2 questions inquiring about SP in organized sports in school and outside of school. Study 2 results PA decreased markedly in both genders between the 1st and 2nd grade of secondary school. Total energy expenditure was reduced by 13 kcal/kg/day on average in boys and by 10 kcal/kg/day in girls (p for both <0.001), while mean daily active energy expenditure decreased by 7 kcal/kg/day (p<0.001) and 3 kcal/kg/day (p=0.04) in boys and girls, respectively. Similarly, the amount of moderate physical activity declined by 49 min/day in boys and 21 min/day in girls (p for both <0.001). At the same time vigorous physical activity was cut by 14 min/day (p<0.001) and 3 min/day (p=0.003) in boys and girls, respectively. Conversely, time spent in SBs did not show any change. Study 2 conclusion In conclusion, a decline in PA between 1st and 2nd grade of secondary school was marked, but was not accompanied with an increase in SBs. Policies aimed at increasing PA should be targeting the period of entering secondary school in order to offset the observed drop in PA. Study 3 methods In this investigation, participants were 844 secondary school students (15.6 years at baseline; 49% girls). SHAPES questionnaire was used to assess PA, SP and SB at ages 15, 16, 17, and 18 and continuous tracking was assessed by stability coefficients and odds ratios calculated using generalized estimating equations. Study 3 results Tracking coefficients for the duration of moderate and vigorous PA and physical activity energy expenditure (PAEE) were similar in both genders and indicated moderate tracking (0.49-0.61), while the stability of SB tended to be somewhat higher over the 4 years of follow-up (0.60-0.72 in boys and 0.60-0.70 in girls). In addition, youth that participated in sports at baseline had16 to 28 time higher odds of continued participation at follow-up, depending on sport type and gender. Finally, both low physical activity and high screen time showed strong tracking in both genders. Study 3 conclusion In conclusion, PA and SB tracked moderately between age 15 and 18, the tracking of SB being slightly stronger compared to PA. Moreover, strong tracking of low PA and high screen time indicates that detection of these risk factors at the beginning of secondary school should be strongly recommended. |
| Abstract (croatian) | Cilj Glavni cilj ove doktorske disertacije je proučiti obrasce tjelesne aktivnosti tijekom srednje škole. Tri specifična cilja su postavljena za tri nezavisne studije (Studija 1, Studija 2 i Studija 3). Studija 1 je imala cilj za utvrditi: (1) obrasce objektivno mjerene tjelesne aktivnosti kod petnaestogodišnjaka oba spola s obzirom na tip školovanja i (2) razlike u tjelesnoj aktivnosti između školskih dana i dana vikenda. Studija 2 imala je za utvrditi promjene u razini tjelesne aktivnosti i sedentarnih ponašanja između prvog i drugog razreda srednje škole. Studija 3 imala je za cilj utvrditi praćenje tjelesne aktivnosti, sudjelovanja u sportu i sedentarnih ponašanja tijekom četiri godine srednje škole. Studija 1 metode U ovoj poprečno-presječnoj studiji sudjelovalo je 187 muških i ženskih ispitanika (61.4% djevojaka) koji su pohađali gimnazije i strukovne škole. Obrasci tjelesne aktivnosti mjereni su objektivno koristeći multisenzorni uređaj tijekom 5 uzastopnih dana. Kovarijati korišteni u studiji bili su biološka dob, socioekonomski status, potkožno masno tkivo, maksimalna temperatura i količina padalina. Studija 1 rezultati Dječaci i djevojčice iz gimnazija ostvarili su veću ukupnu dnevnu količinu utrošene energije (UEP) i aktivne količine utrošene energije (KUE) s obzirom na učenike iz strukovnih škola (UEP: 50 ± 12 kcal/kg/danu vs. 47 ± 12 kcal/kg/danu, p = 0.02; KUE: 23 ± 5 kcal/kg/danu vs. strukovne = 21 ± 6 kcal/kg/danu, p = 0.04). Nisu pronađene značajne razlike u niskoj, umjerenoj i visokoj tjelesnoj aktivnosti između dvije grupe (p = 0.16–0.43). Nadalje, značajno smanjenje UEP i umjerene tjelesne aktivnosti je pronađeno (p< 0.001 and p = 0.02), dok je razina visoke razine tjelesne aktivnosti ostala nepromijenjena (p = 0.76). Tjedni obrasci tjelesne aktivnosti se nisu razlikovali po tipu škole ili spolu (p za interakciju = 0.21-0.50). Značajno manja razina umjerene tjelesne aktivnosti je zabilježena tijekom dana vikenda s obzirom na školske dane, rezultirajući manjom potrošnjom ukupne količine energije, bez obzira na tip škole i spol. Studija 1 zaključak Strategije za tjelesnu aktivnost bi se trebale koncentrirati na povećanje razine tjelesne aktivnosti u strukovnim školama i tijekom dana vikenda. Studija 2 metode U ovoj jednogodišnjoj studiji, ispitanici su bili dječaci i djevojke (81, 28 dječaka i 53 djevojke) u prosječnoj dobi od 15.5 godina na početku. Tjelesna aktivnost je mjerena uz pomoć Senswear multisenzornog uređaja, dok su se sedentarna ponašanja mjerila uz pomoć SHAPES upitnika. Upitniku su se dodala dva pitanja o sudjelovanju u sportu u školi i van škole. Studija 2 rezultati Razina tjelesne aktivnosti značajno se smanjila u oba spola između prvog i drugog razreda srednje škole. Ukupna energetska potrošnja smanjila se za 13 kcal/kg/danu u prosjeku kod dječaka i za 10 kcal/kg/danu kod djevojaka (p vrijednost za oboje <0.001), dok se prosječna dnevna aktivna količina utrošene energije smanjila za 7 kcal/kg/danu (p<0.001) i za 3 kcal/kg/danu (p=0.04) kod dječaka i djevojaka. Slično, količina umjerene tjelesne aktivnosti smanjila se za 49 min/danu kod dječaka i za 21 min/danu kod djevojaka (p za oboje <0.001). U isto vrijeme, razina visoke razine tjelesne aktivnosti smanjila se za 14 min/danu (p<0.001) i za 3 min/danu (p=0.003) kod dječaka i djevojaka. Vrijeme provedeno u sedentarnim ponašanjima se nije značajno promijenilo. Studija 2 zaključak U zaključku, smanjenje razine tjelesne aktivnosti između prvog i drugog razreda srednje škole je bilo značajno, ali nije bilo popraćeno povećanjem razine sedentarnih ponašanja. Strategije kojima je za cilj povećanje razine tjelesne aktivnosti umjesto vremena provedenog u sedentarnim ponašanjima bi trebale ciljati populaciju učenika koji upisuju srednju školu. Studija 3 metode U ovoj studiji, ispitanici su bili 844 učenika srednjih škola (prosječna dob 15.6 godina na početku, 49% djevojaka). SHAPES upitnik je korišten za prikupljanje informacija o razini tjelesne aktivnosti, sudjelovanja u sportu i sedentarnih ponašanja u dobi 15, 16, 17 i 18 godina na temelju kojeg je izračunato sudjelovanje koeficijentima praćenja i omjerima vjerojatnosti koristeći generalizirane jednadžbe. Studija 3 rezultati Koeficijenti praćenja za trajanje umjerene i visoke razine tjelesne aktivnosti bili su slični za oba spola i označavali su umjereno praćenje (0.49-0.61), dok je stabilnost sedentarnih ponašanja bila nešto viša tijekom četverogodišnjeg praćenja (0.60-0.72 u dječaka i 0.60-0.70 u djevojčica). Mladi koji su sudjelovali u sportu na početku su imali 16 do 28 puta veću vjerojatnost da će se nastaviti baviti sportom, s obzirom na tip sporta i spol. Konačno, niska razina tjelesne aktivnosti i visoka razina vremena provedenog pred računalom, televizijom i mobitelom je pokazala jako praćenje u oba spola. Studija 3 zaključak U zaključku, tjelesna aktivnost i sedentarna ponašanja pokazala su umjereno praćenje između 15.-te i 18.-te godine, gdje je praćenje bilo malo jače kod sedentarnog ponašanja s obzirom na tjelesnu aktivnost. Nadalje, jako praćenje niske razine tjelesne aktivnosti i visoke razine vremena provedenog pred računalom, televizijom i mobitelom naglašava da je otkrivanje tih rizičnih čimbenika preporučeno na početku srednje škole. |
