ObjectifsL’objectif principal a été de déterminer la quantité d’activité physique chez des enfants de 8- 16 ans,scolarisés dans la ville de Bogota (Colombie) vivant à l’altitude de 2640 mètres. Cette activité, mesurée pendant les périodes scolaires et de vacances et agrégée sur une année, a été exprimée en dépensed’énergie rapportée à la journée (DEJmA, kJ.kg-1.jour-1). Cette activité DEJmA a été secondairementanalysée en fonction de l’âge, du genre, du niveau Socioéconomique (NSE), des donnéesanthropométriques individuelles incluant l’âge biologique (Tanner), la composition corporelle, lesomatotype et la condition physique (EUROFIT).MéthodesCette étude d’épidémiologie descriptive et analytique a comporté cinq phases successives : 1)Elaboration d’un questionnaire QAPACE et formation des chercheurs; 2) Test de compréhension duquestionnaire QAPACE; 3) Etude de faisabilité et reproductibilité de QAPACE; 4) Etude de validationsur un échantillon (36 sujets) des mesures de DEJ par rapport à la mesure de VO2max, selon deuxméthodes directe (cycle d’ergospirométrie) et indirecte (test de Léger); 5) Analyse générale d’unéchantillon représentatif de 1840 enfants selon un sondage en grappe randomisé à deux niveaux (écoles,classes). Le questionnaire étudiait 13 grandes catégories d’activités.Les analyses des données de reproductibilité et de validation ont reposé la méthode de Bland et Altmanet la mesure du CCI. La dépendance de la DEJ en fonction des données socio- économiques et desdonnées anthropométriques a été étudiée avec des méthodes de régression linéaire uni- et multivariée(SPSS 21).RésultatsLe questionnaire, adapté à la population d’enfants de langue hispaniauem a présenté une corrélationintra classe CCI=0.96 (CI 0.95-0.97). La validité avec la mesure de VO2max (direct et indirect) a été de0.76(0.66) (p<0.01). La DEJ moyenne sur les 1840 enfants étaient, chez les 904 garçons, 167.98±37.30kJ.kg-1.jour-1 (valeur absolue : 6.83 MJ/Jour, relative : 170.41±39.92) et, chez les 936 filles165.64±34.26 kJ/kg/jour (p<0.01) (6.59 MJ/jour, 165.64 ±34.26 kJ/kg/j). La DEJ pour la périodescolaire et de vacances fut 158.43±42.99 et 199.44±18.55 kJ/kg/jour (p<0.01) pour les garçons et lesfilles respectivement. La DEJ durant le temps libre fut de 59.86±44.16 chez les garçons et 53.81±37.11kJ/kg/jour (p<0.01) pour les filles.ConclusionsSur la base d’une bonne reproductibilité et validité du questionnaire QAPACE, la DEJ (kJ.kg-1.jour-1)rapporté au poids corporel total ou au poids maigre a donné des résultats inférieurs à ceux d’autresétudes, avec notamment 51% des garçons et 61% de filles inactifs, respectivement. Les garçons furentplus actifs que les filles dans le groupe post pubères (p<0.01). Le temps consacré à regarder la TV étaitde 4.2 heures/jour. Les sports les plus pratiqués étaient le football, le cyclisme, et la marche pour lesgarçons et la marche, le cyclisme et le patinage pour les filles. / ObjectivesThe first statement was to determine the amount of physical activity expressed in expenditure weightedaverage day of a year (DEEmY) energy during the school year and holidays (kJ.kg-1.day-1) in terms ofequivalence caloric and metabolic cost of activities most commonly performed by young people. Thesecond statement was that of defining the relationship between the DEEmY vs age, gender,socioeconomic level (SEL), height, body weight, body surface (BS), the Body Mass Index (BMI),biological age (Tanner), body composition, somatotype and fitness (EUROFIT).MethodsThis descriptive study developed five different phases: the first phase: it was the training of researchers,the second phase: understanding and final questionnaire editing QAPACE, in the third phase: feasibilityand reproducibility of QAPACE in the fourth stage: it was the validation study by direct VO2max (36subjects) by ergospirometry and indirect through the test Leger and the fifth phase cycle was developedin 1840 with the general study subjects. The questionnaire was developed by 13 categories. Forreproducibility and validation of the test-Retest method and comparison of arithmetic by the method ofBland-Altman, Pearson correlation was applied. The data is stored in Visual Fox Pro 6.0 and analyzedusing SPSS 21 statistical program IBM. Means were compared using multivariate linear model applyingtipe II.The values used as fixed variables: gender (male and female), age (8-16 years) and three SEL (six strata:1-2, 3-4 and 5-6); as dependent variables were evaluated: height, weight, leisure time, expressed inhours/day and daily energy expenditure DEE (Kj.kg-1.day-1) during leisure time (DEE-LT) during thetime school (DEE-ST) during the holidays (DEE-VT), and DEE total mean year (DEEmTY).For a post-Hoc analysis was used the minimum significant difference (MSD) with fixed factors,interaction factors descriptive statistics, tests of homogeneity with a significance level of 0.05.ResultsThe questionnaire was correct understanding of the reproducibility intra-Class correlation was r = 0.96(CI 0.95-0.97), the validity of the direct and indirect VO2 was 0.76 (0.66) (p <0.01) and for generalstudy quantifying the average of the DEE of 1840 subjects was 167.98 ± 37.30; for boys (n = 904),absolute value: 6.83 MJ/day, relative: 170.41 ± 39.92 and for girls (n = 936): 6.59 MJ/day (p <0.001)165.64 ± 34.26 (kJ.kg-1.day-1) (p <0.01). The DEE to the school holiday period and was 158.43 ± 42.99and 199.44 ± 18.55 (kJ.kg-1.day-1) (p <0.01) for boys and girls respectively. The DEE during free timewas of 59.86 ± 44.16 for males and 53.81 ± 37.11 (kJ.kg-1.day-1) (p <0.01) for girlsConclusionsOn the basis of good reproducibility and validity of the questionnaire QAPACE applied to students inthe larger study, the DEE (kJ/kg/day) with total body weight or lean weight was less compared to ofother studies giving results for 51% of boys and 61% of inactive girls. Boys were more active than girlsin the post pubertal group (p <0.01). As for the time spent watching TV, it was 4.2 hours/day, and themost popular sports was soccer, cycling, and walking for boys and walking, cycling and skating for

Case control studies have shown that a high consumption of fish, olive oil, and cooked vegetables is associated with a decreased risk of developing rheumatoid arthritis (RA). These foods have a central position in the traditional Cretan Mediterranean diet, and it has been suggested that dietary factors contribute to the low prevalence of RA in Mediterranean countries. The overall aim of this thesis was to examine whether a modified Cretan Mediterranean diet can reduce signs and symptoms of RA. This was investigated in a three-month dietary intervention trial in which 51 patients with well controlled, although active RA of at least two years duration took part. A further aim was to study the compliance with the experimental and control diets used in the study, and to validate the diet history interview method used to assess the dietary intake. The validation was carried out by means of biological markers of dietary intake. From baseline to the end of the study the group that had adopted the Cretan Mediterranean diet (MD group; n=26) obtained a reduction in disease activity, improved physical function, and improved vitality, while no changes was seen in the control diet group (CD group; n=25). According to the dietary assessments, the intake frequencies of antioxidant-rich food items increased in the MD group. This group also had a significantly higher intake of vitamin E, vitamin C and selenium compared to the CD group. Despite the reported increase in the consumption frequencies of antioxidant-rich foods, the plasma levels of carotenoids, vitamin C, lipid adjusted tocopherols, uric acid and urine malondialdehyde, a marker of oxidative stress, were unchanged at the end of the study. The plasma levels of retinol, vitamin C and uric acid were, however, correlated to indices of disease activity. Changes in the reported consumption of food groups with relevance to the fat intake were also observed in the MD group, including an increased intake of fish, shellfish and poultry, and a decreased intake of meat and high fat dairy products. As a result, the total fat intake was lower in the MD group compared to the CD group. Furthermore, in the MD group a slightly higher percentage of the energy intake was derived from polyunsaturated fatty acids and a lower percentage from saturated fatty acids. This group also had a lower ratio of n-6:n-3 fatty acids. A corresponding change in the relation between n-6 and n-3 fatty acids was also observed in s-phospholipids. The validation of the diet history interview method showed that the diet history interview could capture the dietary intake fairly well. The validity of the reported dietary intake did not differ between the MD and the CD group, which indicates that the dietary assessment was not biased by the dietary intervention.

Energy intake (EI) and energy expenditure (EE) across the menstrual cycle (MC), while considering body adiposity, have not been previously evaluated in the same individuals. This study mainly examined the variations in energy balance (EB) across MC. Seventeen women (Body fat-DXA:28.5%) participated in three identical sessions during distinct phases of the MC: Early-follicular, Late-follicular/ovulation and Mid-luteal (confirmed by basal temperature and sex-steroid hormones). EI, resting metabolic rate (RMR), physical-activity EE (PAEE), severity of PMS, leptin and relative-reinforcing value (RRV) of preferred foods were measured during each phase. No differences in body fat, EI, RMR, PAEE, leptin and RRV of food were noted across MC. Trends were noted in preferred snack (p=0.06) and combined snack/fruit (p=0.06) intakes, while differences were noted in severity of PMS (p<0.05) across phases. Changes in EB across the MC were not noted. PMS was more severe, and preferred snack and combined snack/fruit intakes were slightly higher during mid-luteal phase.

Aim: The aim with the current study was to examine the physical activity levels (PAL) in a group of children and adolescents with cystic fibrosis (CF) and compare PAL-values between boys and girls. Further, the aim was to look at the total energy expenditure (TEE) estimated with an activity diary and measured with the accelerometer and compare values between these two measurement methods. Method: The sample consisted of 29 children and adolescents diagnosed with CF where PAL and TEE was measured during a three-day registration with activity diary and the ActiCal© accelerometer. The data was analyzed with the Mann-Whitney U-test. Results: The results indicated that the girls had a slightly higher median PAL-value than the boys. In addition, the range between the lowest and highest PAL-value was larger among the boys. The lowest PAL-value was lower among the boys than among the girls and the highest value was similar to the girls’ highest PAL-value. Overall, the subjective estimation of the PAL-values were slightly higher than what was objectively measured by the accelerometer. There was a slight difference between TEE estimated with the activity diary compared to the TEE measured by the accelerometer. There was no significant difference in PAL-values between boys and girls. Conclusion: There was no significant difference in PAL-value between boys and girls and that there was a slight difference in TEE estimated with the activity diary and measured with the accelerometer. Both methods of data collection are reliable enough when used together to produce a valid estimation of CF- children’s activity levels and TEE. The fact that both PAL and TEE values were higher in the activity diary may be because the participants perceived a higher level of physical activity then what was objectively measured with the accelerometer.

Energy intake (EI) and energy expenditure (EE) across the menstrual cycle (MC), while considering body adiposity, have not been previously evaluated in the same individuals. This study mainly examined the variations in energy balance (EB) across MC. Seventeen women (Body fat-DXA:28.5%) participated in three identical sessions during distinct phases of the MC: Early-follicular, Late-follicular/ovulation and Mid-luteal (confirmed by basal temperature and sex-steroid hormones). EI, resting metabolic rate (RMR), physical-activity EE (PAEE), severity of PMS, leptin and relative-reinforcing value (RRV) of preferred foods were measured during each phase. No differences in body fat, EI, RMR, PAEE, leptin and RRV of food were noted across MC. Trends were noted in preferred snack (p=0.06) and combined snack/fruit (p=0.06) intakes, while differences were noted in severity of PMS (p<0.05) across phases. Changes in EB across the MC were not noted. PMS was more severe, and preferred snack and combined snack/fruit intakes were slightly higher during mid-luteal phase.

Syfte med denna studie var att undersöka energiförbrukningen vid havspaddling. Energiförbrukningen undersöktes i vila och vid två olika hastigheter (4 och 7 km/h), först med en olastad och sedan med en lastad kajak (20 kg). Dessutom undersöktes hur det passiva motståndet förändrades vid successivt ökad hastigheten. Studien genomfördes i en försöksgrupp med jämn könsfördelning och med varierande ålder och paddlingserfarenhet. I studiens första del uppmättes försökspersonernas hjärtfrekvens i förhållande till syrgasupptag och koldioxidproduktion vid en successivt ökad belastning i en kajakergometer. För varje försöksperson kunde sedan en korrelationskurva beräknas mellan hjärtfrekvens och syrgasupptag. Utifrån den hjärtfrekvens som sedan försökspersonen hade under paddlingen kunde syrgasupptaget beräknas. Vid paddling med en olastad kajak och en hastighet av 4 km/h beräknades syrgasupptaget till 5 ml/kg/min. Vid en hastighet 7 km/h så ökade syrgasupptaget signifikant till 11.5 ml/kg/min (p&lt; 0.05). Vid paddling med en lastad kajak så ökade syrgasupptaget signifikant från 6,5 ml/kg/min vid 4 km/h till 14,5 ml/kg/min (p&lt; 0.05) vid 7 km/h. Om energiförbrukningen beräknas utifrån syrgasupptaget för en person på 75 kg skulle en paddelhastighet på 4 km/h innebära en förbrukning på 458 kJ (107,4 kcal/h) med en olastad kajak och 585 kJ (139.8 kcal/h) med en lastad kajak. Vid 7 km/h var motsvarande värden 1080 kJ (258 kcal/h) (olastad kajak) och 1350 kJ (322 kcal/h) (lastad kajak). Det passiva motståndet ökade exponentiellt med ökad hastighet. / The aim of this study was to examine energy consumption when sea kayaking. The energy consumption was examined at rest and at two different speeds (4 and 7 km/h respectively), first with an empty and then with a packed kayak (20 kg). Moreover, the kayaks’ passive drag in the water was measured in order to examine how this was influenced by the speed through the water. The study was implemented in a group of paddlers with even gender distribution but with varying age and experience. In the first part of the experiment, we measured the participants’ heart frequency, oxygen uptake and carbon dioxide production during gradually increased work load in a kayakergometer. For each test subject correlation curves were constructed from the recorded heart rate and oxygen uptake. Based on the persons heart rate during paddling, oxygen uptake was calculated using the individual regression equation which was calculated in the first part of the experiment. When paddling at 4 km/h with an unpacked kayak, the oxygen uptake was measured to 5 ml/kg/min. At 7 km/h, it increased significantly to 11.5 ml/kg/min (p&lt; 0.05). Paddling with a packed kayak oxygen consumption increased to 6.5 ml/kg/min at 4 km/h and significantly to14.5 ml/kg/min at 7 km/h. If energy consumption is calculated on the basis of oxygen uptake for a person weighing 75 kg, at 4 km/h this corresponds to a consumption of 450 kJ (107.4 kcal/h) when kayaking with an unpacked kayak and 585 kJ (139.8 kcal/h) with a packed ditto. At 7 km/h, energy consumption was calculated to 1080 kJ (258 kcal/h) (empty kayak) and 1350 kJ (322 kcal/h) (packed kayak). The passive drag increased exponentially with increased speed.

L’obésité et la sédentarité sont considérées comme des problèmes importants de santé publique. L’augmentation de l’activité physique est une des stratégies recommandées pour obtenir un bilan énergétique positif dans les interventions de perte de poids. Deux accéléromètres, le Sensewear Armband (SWA) et l’Actical (ACT), sont des outils simples à utiliser en recherche clinique, mais à notre connaissance, aucune étude n’a évalué leur capacité à détecter des hausses de la dépense énergétique. De plus, très peu d’études, avec des résultats par ailleurs contradictoires, ont été effectuées afin de déterminer la fiabilité de ces accéléromètres pour la mesure de la dépense énergétique au repos et au cours d’une activité physique au vélo stationnaire. Ainsi, les objectifs de cette étude étaient: 1) évaluer, pendant 3 journées consécutives, la reproductibilité des valeurs de la dépense énergétique obtenues avec le SWA et l’ACT, au repos et au cours d’une activité physique de 45 minutes sur un vélo stationnaire, 2) déterminer la capacité de ces accéléromètres à détecter des hausses de 5% et 10 % de la dépense énergétique totale (DET) au moyen de la modification d’une activité physique au tapis roulant pendant 45 minutes. Cette étude transversale effectuée auprès de 20 sujets en santé, âgés de 20 à 32 ans et avec un IMC moyen de 23 kg/m2, consistait en 5 visites à la clinique. Les 3 dernières visites, sous supervision directe pendant 10 heures, comportaient des activités programmées sur le vélo stationnaire et la marche sur tapis roulant pendant 45 minutes. Les résultats montrent que le SWA et l’ACT donnent des valeurs reproductibles pour estimer la dépense énergétique au repos et la dépense énergétique au vélo (corrélations intra classe, p<0,001). Par contre, pour des hausses préétablies de la DET de 5% et 10%, les estimations respectives obtenues étaient de 1,4% et 7,8% avec le SWA et de 3,4% et 13,1% avec l’ACT. Le SWA sous-estime les hausses de 5% et de 10% et l’ACT sous-estime la hausse de 5% et surestime la hausse de 10% de la DET. Plus de recherches sont nécessaires avant de confirmer l’usage du SWA et de l’ACT dans l’estimation des hausses de la dépense énergétique totale. / Obesity and physical inactivity are considered significant public health problems. Increasing physical activity is one strategy recommended to induce a positive energy balance in weight loss interventions. Two accelerometers, the Sensewear Armband (SWA) and Actical (ACT), are simple tools to use in research, but to our knowledge, no studies have assessed their capacity to detect increases in energy expenditure. Moreover, very few studies, and with conflicting results, have been conducted to determine the reliability of these accelerometers for the measurement of resting energy expenditure and physical activity energy expenditure on a stationary bicycle. Thus the objectives of this study were as follows : 1) evaluate, during 3 consecutive days, the reproducibility of values of energy expenditure obtained with the SWA and the ACT, at rest and during physical activity for 45 minutes on a stationary bicycle, 2) determine the capacity of these accelerometers to detect increases of 5% and 10% in total energy expenditure (TEE) obtained by modifying an activity on a treadmill for 45 minutes. This cross-sectional study conducted with 20 healthy subjects, aged 20-32 years with an average BMI of 23 kg/m2, consisted of 5 visits to the clinic. The last 3 visits, under direct supervision for 10 hours, included programmed physical activities on a stationary bicycle and on a treadmill for 45 minutes. The results show that the SWA and the ACT provide values which are reproducible for estimating resting energy expenditure and physical activity energy expenditure on the stationary bicycle (intra-class correlations, p<0,001). However, for pre-established increases in TEE of 5% and 10%, corresponding estimations obtained were 1.4% and 7.8% with the SWA and 3.4% and 13.1% with the ACT. The SWA underestimates increases of 5% and 10% and the ACT underestimates increases of 5% and overestimates increases of 10% of TEE. More research is needed before confirming the use of the SWA and the ACT in the estimation of increases in total energy expenditure.

Whole yellow pea flour (WPF) and fractionated yellow pea flour (FPF) are novel functional food ingredients that vary in nutritional composition. Consequently, the health benefits of WPF and FPF remain undefined. The purpose of this research was to identify the effects of WPF and FPF on risk factors and morbidities associated with cardiovascular disease, diabetes and obesity as well as the gastrointestinal microbiome. Using USDA recommended dosages of WPF and FPF, clinical endpoints and the colonic microbiome were investigated using a human clinical trial engaging a cross-over design and a diet and energy controlled paradigm. Humans were also utilized to investigate post-prandial glycemic responses and sensory characteristics of novel functional foods formulated with WPF. Finally, Golden Syrian hamsters were used to assess the impact of high doses of WPF and FPF on clinical endpoints and caecal microbial abundance. Results reveal that USDA recommended dosages of WPF and FPF in humans decreased (p<0.05) fasting insulin and estimates of insulin resistance compared to white wheat flour (WF). Android-to-gynoid fat ratios in women were lower (p=0.027) in the WPF group compared to the WF group. FPF decreased (p<0.05) post-prandial energy expenditure alongside a tendency (p<0.075) to reduce carbohydrate oxidation. Novel biscotti and banana bread formulated with WPF induced low post-prandial glycemic responses which were similar to boiled whole yellow peas and significantly lower (p<0.05) than white bread. Sensory analysis of novel WPF biscotti and banana bread demonstrated that WPF-based food products are palatable and acceptable for human consumption. Hamsters consuming diets containing 10% WPF and FPF induced similar reductions (p<0.05) in fasting insulin levels compared to controls. However, animals consuming WPF increased (p<0.05) oxygen consumption while FPF decreased (p<0.05) fasting glucose levels. In addition, terminal restriction fragment length polymorphism analysis revealed that WPF and FPF induced distinct shifts in caecal microbial populations within the phyla Firmicutes. Finally, pyrosequencing analysis of human fecal microbiota demonstrated that FPF and WPF induced shifts in bacterial genera, primarily within Bacteroidetes and Firmicutes. In conclusion, whole and fractionated yellow pea flours are functional food ingredients and can be utilized to manage risk factors for lifestyle-related diseases in humans.

Obesity is affecting an increasingly larger proportion of adolescents in the world, and this can be attributed to low resting metabolic rate (RMR) as well as reduced physical activity (PA) levels. Little is known about objectively determined habitual PA and RMR in 16 year old African adolescents. The purpose of this study is twofold. Firstly, to determine the objectively measured PA status of adolescents and secondly, to determine the relationship that exists between RMR and PA in 16 year old adolescents. Two hundred and twenty six (226) adolescents aged sixteen (16) wore the Actiheart® monitor, combined accelerometry and heart rate for seven (7) consecutive days. Six high schools were recruited to take part in the study: two from town (high socio-economic status) and four from the township (low socio-economic status) of the Potchefstroom area of the North West Province of South Africa. Times spent in moderate to vigorous physical activity, physical activity counts per minute (CPM), total energy expenditure (TEE), active energy expenditure (AEE) and physical activity levels (PAL) were assessed using the Actiheart®. The participants’ RMR was measured by indirect calorimetry using the Fitmate Pro (Cosmed, Italy). All data analyses were performed with the SPSS Version 20 software (IBM SPSS, II). The descriptive statistics (mean and standard deviations) as well as independent t-tests and Mann-Whitney U test were performed to determine differences between ethnicity and genders and to calculate practical significance. A Type I error rate of p ≤ 0.05 was used for statistical significance. To investigate the relationship between RMR and physical activity regression analysis was performed with adjustment for gender, race and fat free mass. Results: Significantly higher PAL (1.57 ± 0.15) were determined in girls compared to boys (PAL = 1.41 ± 0.10). Black adolescents indicated significant higher PAL (1.53 ± 0.14) compared to white adolescents (1.45 ± 0.16). On average, regardless of race or gender, the participants were more active on weekdays than weekends. The current study shows that girls spent more minutes/day in moderate to vigorous physical activity (MVPA) than the boys. The results show that 16.4% of the study sample was either overweight or obese. After adjustment for gender, ethnicity and FFM, linear regression between RMR and moderate-to-vigorous PA yielded an r2 = 0.46 (p ˂ 0.05.) Conclusion: Objectively determined PA of adolescents in South Africa indicates that only one third of adolescents are meeting the recommended 60 minutes of daily MVPA. Gender and race specific interventions are needed to increase habitual physical activity levels in adolescents. Given the fact that the studied sample did not meet recommended daily physical activity and the adverse effect of inactivity and chronic diseases of life style, urgent strategies to inculcate the culture of regular physical activity as a preventative measure of chronic diseases of life style are needed. Behaviour that is carried on into adulthood is established during adolescence. Civic health efforts should focus on encouraging adolescent involvement in regular moderate-to-vigorous PA, which will subsequently increase RMR and lower the risk of the development of non-communicable chronic diseases such as obesity. Further local research is needed to confirm the association between RMR and PA in the local population. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013.

Obesity is affecting an increasingly larger proportion of adolescents in the world, and this can be attributed to low resting metabolic rate (RMR) as well as reduced physical activity (PA) levels. Little is known about objectively determined habitual PA and RMR in 16 year old African adolescents. The purpose of this study is twofold. Firstly, to determine the objectively measured PA status of adolescents and secondly, to determine the relationship that exists between RMR and PA in 16 year old adolescents. Two hundred and twenty six (226) adolescents aged sixteen (16) wore the Actiheart® monitor, combined accelerometry and heart rate for seven (7) consecutive days. Six high schools were recruited to take part in the study: two from town (high socio-economic status) and four from the township (low socio-economic status) of the Potchefstroom area of the North West Province of South Africa. Times spent in moderate to vigorous physical activity, physical activity counts per minute (CPM), total energy expenditure (TEE), active energy expenditure (AEE) and physical activity levels (PAL) were assessed using the Actiheart®. The participants’ RMR was measured by indirect calorimetry using the Fitmate Pro (Cosmed, Italy). All data analyses were performed with the SPSS Version 20 software (IBM SPSS, II). The descriptive statistics (mean and standard deviations) as well as independent t-tests and Mann-Whitney U test were performed to determine differences between ethnicity and genders and to calculate practical significance. A Type I error rate of p ≤ 0.05 was used for statistical significance. To investigate the relationship between RMR and physical activity regression analysis was performed with adjustment for gender, race and fat free mass. Results: Significantly higher PAL (1.57 ± 0.15) were determined in girls compared to boys (PAL = 1.41 ± 0.10). Black adolescents indicated significant higher PAL (1.53 ± 0.14) compared to white adolescents (1.45 ± 0.16). On average, regardless of race or gender, the participants were more active on weekdays than weekends. The current study shows that girls spent more minutes/day in moderate to vigorous physical activity (MVPA) than the boys. The results show that 16.4% of the study sample was either overweight or obese. After adjustment for gender, ethnicity and FFM, linear regression between RMR and moderate-to-vigorous PA yielded an r2 = 0.46 (p ˂ 0.05.) Conclusion: Objectively determined PA of adolescents in South Africa indicates that only one third of adolescents are meeting the recommended 60 minutes of daily MVPA. Gender and race specific interventions are needed to increase habitual physical activity levels in adolescents. Given the fact that the studied sample did not meet recommended daily physical activity and the adverse effect of inactivity and chronic diseases of life style, urgent strategies to inculcate the culture of regular physical activity as a preventative measure of chronic diseases of life style are needed. Behaviour that is carried on into adulthood is established during adolescence. Civic health efforts should focus on encouraging adolescent involvement in regular moderate-to-vigorous PA, which will subsequently increase RMR and lower the risk of the development of non-communicable chronic diseases such as obesity. Further local research is needed to confirm the association between RMR and PA in the local population. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013.