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PURPOSE: This study aimed to evaluate the differences between predicted resting energy expenditure (REE), using fat-free mass (FFM)-based prediction equations, and measured REE in Korean male collegiate soccer players. METHODS: Fifteen male collegiate soccer players (18-21 years) participated in this study. The REE measurements were conducted using the Douglas bag method. Body composition was measured by dual-energy X-ray absorptiometry (DXA). The differences between the measured REE and predicted REE, using the five FFM-based REE equations, were analyzed using the t-test, calculation of errors, regression analysis, and the Bland-Altman method. RESULTS: The Cunningham (1980) and ten Haaf and Weijs (2014) equations showed significantly overestimated REE (1,808 ± 99 kcal/d, p <0.01; 1,838 ± 103 kcal/d, p <0.01; respectively), but the Owen (1988), Taguchi (2011), and Kim (2015) equations' estimations were not significantly different from the measured REE (1,589 ± 106 kcal/d, 1,640 ± 124 kcal/d, and 1,622 ± 68 kcal/d, respectively). The Taguchi equation gave the best prediction of REE with the lowest constant error (-6 ± 125) and effect size (-0.05), and a non-significant proportional bias (p = 0.95). CONCLUSION: The Taguchi equation is recommended for predicting REE in Korean collegiate soccer players. The selection process of a REE-prediction equation must take into consideration the target population's characteristics. Future studies are recommended to evaluate the validity of the different FFM-based REE-prediction equations in various Korean athletes.
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Calf muscle plays an important function in driving the movement of stepping on the ground and moving forward when walking or running. The Achilles tendon has been reported to be closely related to the elasticity of tendons to absorb shock and rebound and convert energy into propulsion. We wanted to determine the effect and correlation of the anatomical structure of the calf region on function. Measurements of anatomical structures were conducted with 51 volunteers using ultrasonography, and exercise capacity tests were conducted to measure anaerobic power, elasticity, and flexibility. The mean power and length of the calf (LoC), muscle thickness (MT), and fascicle angle (FA) of the medial head of gastrocnemius (p < 0.001) showed the strongest positive correlation among the variables of anatomical structures. MT of the Gastrocnemius and LoC Gastrocnemius were also correlated with peak power. In the anatomical structure variables, the FA of the lateral head of gastrocnemius, length and width of the Achilles tendon, and part of the athletic ability, the standing long jump test and sitting trunk flexion test, were not significantly correlated. Based on these results, it can be concluded that the height and degree of development of the calf muscles are structures that affect the exercise of anaerobic power. Hence, it can be used as a predictor of athletic ability. Furthermore, the trainer can predict athletic ability according to the characteristics of the event by first understanding the athlete's physical condition.
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Tendón Calcáneo , Deportes , Tendón Calcáneo/diagnóstico por imagen , Humanos , Pierna/diagnóstico por imagen , Movimiento/fisiología , Músculo Esquelético/fisiología , Ultrasonografía/métodosRESUMEN
Metabolic suppression due to relative energy deficiency can cause various physiological impairments in athletes. The purpose of this study was to evaluate within-day energy balance (WDEB) and the ratio between measured and predicted resting energy expenditure (REEratio) and to investigate the relationships between the markers of metabolic suppression. Ten male collegiate soccer players completed a 7-day food diary, physical activity, and heart rate records during the training and rest days. Energy intake (EI) and energy expenditure (EE) were analyzed to evaluate WDEB components. Body composition was measured using dual-energy X-ray absorptiometry (DXA), and blood sampling was conducted for hormonal analysis. The REE was measured using the Douglas bag method and predicted using the DXA-predicted method to calculate the REEratio. Participants were categorized into the normal (REEratio ≥ 0.94, n = 5) and suppressed (REEratio < 0.94, n = 5) groups. There were no group differences in the components of WDEB, except diet-induced thermogenesis (DIT), but EI was significantly higher in the normal group than in the suppressed group (7-day total: 3660 ± 347 vs. 3024 ± 491 kcal/day, p = 0.046 and rest days: 3772 ± 463 vs. 2796 ± 800 kcal/day, p = 0.046). Analysis of hormonal markers of metabolic suppression only showed a significant positive association between insulin-like growth factor-1 (IGF-1) and REEratio (r = 0.771, p = 0.009). The relationships between metabolic suppression and the markers of energy deficiency were inconclusive. There are possible associations of insufficient EI and IGF-1 levels with metabolic suppression, and further study is required to understand energy deficiency in male soccer players.
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Metabolismo Basal , Metabolismo Energético/fisiología , Fútbol/fisiología , Adolescente , Atletas , Composición Corporal/fisiología , Registros de Dieta , Ingestión de Energía , Ejercicio Físico , Humanos , Masculino , República de Corea , Adulto JovenRESUMEN
Athletes cultivate highly developed muscles based on their sport category, creating a body shape that matches the characteristics of that sports category. We tested the significance of the correlation between muscle development characteristics and anaerobic power in athletes to build a database for each category. Fifty-eight college athletes participated in this study. To assess muscle characteristics, muscle thickness (MT) and fascicle angle (FA) were measured by ultrasonography (US) in lower limb. Furthermore, anaerobic power was measured with the Wingate test. Analysis of the correlation between muscle structure and anaerobic power revealed significant differences between the sports categories, except for the MT of the medial head of gastrocnemius (Gm), lateral head of gastrocnemius, and FA of Gm. A significant difference was observed for all parameters, except for the arrival time to peak power in the anaerobic power items; in particular, a high degree of correlation in mean power/kg and peak power/kg was observed. A similar tendency was observed in the correlation between muscle structure and anaerobic power in most sports categories, but certain muscle characteristic factors were prominent in each sport. Based on these, it is possible to contribute to predicting and promoting athletic performance.
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Umbral Anaerobio/fisiología , Anaerobiosis/fisiología , Rendimiento Atlético/fisiología , Músculo Esquelético/fisiología , Adulto , Atletas , Prueba de Esfuerzo/métodos , Humanos , Extremidad Inferior/fisiología , Masculino , Fuerza Muscular/fisiología , Ultrasonografía/métodos , Adulto JovenRESUMEN
Low energy availability (EA) can impair physiological function in athletes. The purpose of this study was to investigate EA status, metabolic status, and bone metabolism with biochemical analysis in Korean male soccer players. Twelve male athletes (18-20 years) completed the study. Body composition and bone mineral density were measured using dual energy X-ray absorptiometry (DXA), while VO2 max was determined by an incremental exercise test. Blood samples were taken for bone marker and hormone analyses. Resting energy expenditure (REE) was measured using the Douglas bag method and predicted using the DXA method. Food diaries and heart rates (HR) during training were recorded, and the Profile of Mood States 2 and Eating Attitude Test 26 were completed. Group differences between low EA (LEA <30 kcal/kg FFM/d, n = 5) and high EA (HEA ≥30 kcal/kg FFM/d, n = 7) were evaluated. The mean EA of the all participants was 31.9 ± 9.8 kcal/kg FFM/d with only two participants having an EA above 45 kcal/kg FFM/d. LEA showed suppressed REE (LEA: 26.0 ± 1.7 kcal/kg/d, HEA: 28.8 ± 1.4 kcal/kg/d, p = .011) with a lower REEratio (LEA: 0.91 ± 0.06, HEA: 1.01 ± 0.05, p = .008) as well as a lower insulin-like growth factor 1 (IGF-1) level (LEA: 248.6 ± 51.2 ng/mL, HEA: 318.9 ± 43.4 ng/mL, p = .028) compared to HEA. There were no group differences in bone markers or other hormone levels. Korean male athletes exhibited low EA status with suppressed metabolism, but there was limited evidence on the effect of EA on bone metabolism, endocrine system, and psychological parameters.
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Composición Corporal/fisiología , Ingestión de Energía/fisiología , Metabolismo Energético/fisiología , Fútbol , Densidad Ósea , Registros de Dieta , Humanos , Masculino , Proyectos Piloto , República de Corea , Fenómenos Fisiológicos en la Nutrición Deportiva , Adulto JovenRESUMEN
BACKGROUND: An increase in bone mineral density during adolescence increases resistance to fractures in older age. The Korean Society for Bone and Mineral Research and the Korean Society of Exercise Physiology developed exercise guidelines to increase the peak bone mass (PBM) in adolescents based on evidence through a systematic review of previous research. METHODS: Articles were selected using the systematic method, and the exercise guidelines were established by selecting key questions (KQs) and defining the effects of exercises based on evidence through a literature review for selecting the final exercise method. There were 9 KQs. An online search was conducted on articles published since 2000, and 93 articles were identified. RESULTS: An increase in PBM in adolescence was effective for preventing osteoporosis and fractures in older age. Exercise programs as part of vigorous physical activity (VPA) including resistance and impact exercise at least 5 to 6 months were effective for improving PBM in adolescents. It is recommended that resistance exercise is performed 10 to 12 rep·set-1 1-2 set·region-1 and 3 days·week-1 using the large muscles. For impact exercises such as jumping, it is recommended that the exercise is performed at least 50 jumps·min-1, 10 min·day-1 and 2 days·week-1. CONCLUSIONS: Exercise guidelines were successfully developed, and they recommend at least 5 to 6 months of VPA, which includes both resistance and impact exercises. With the development of exercise guidelines, the incidence of osteoporosis and fractures in the aging society can be reduced in the future, thus contributing to improved public health.
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PURPOSE: This study was to clarify the effect of age and competition level by measuring bone metabolism markers and bone mineral density measurements of junior high school and high school female rhythmic gymnasts, who restrict their diets to maintain a low body weight, while routinely undertaking long hours of high-intensity exercise, comparing the gymnasts based on their elite/non-elite. METHODS: The study investigated 7 junior high school and 12 high school female rhythmic gymnasts. For comparison by competition level, the 7 junior high school gymnasts were separated into 3 gymnasts who competed at national level (junior high school elite), and 4 gymnasts who did not compete at that level (junior high school non-elite), and the 12 high school gymnasts were separated into 7 gymnasts who competed at national level (high school elite) and 5 gymnasts who did not compete at that level (high school non-elite). The measurement items were bone mineral density, bone metabolism markers (undercarboxylated osteocalcin (ucOC), osteocalcin (OC), bone-specific alkaline phosphatase (BAP), calcium (Ca), inorganic phosphorus (P), alkaline phosphatase (ALP), parathyroid hormone (PTH), type 1 collagen cross-linked N-telopeptide (NTx)). We also surveyed the gymnasts' height, weight and nutrition. RESULTS: In this study we found: 1) The high school gymnasts who competed at high-level rhythmic gymnastics had good results for bone metabolism markers and bone mineral density. 2) Elite high school gymnasts had restricted diets. 3) Nutritionally, their energy intake and carbohydrate intake was low, but their intake of protein, calcium, iron, vitamin D and vitamin K was good. CONCLUSION: The results found that the elite gymnastics showed a higher bone density than the non-elite group that suggests the possibility of inhibiting bone formation in the bone metabolism.
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PURPOSE: This study was performed to assess the effects of high-intensity intermittent swimming training(HIT) on bone in ovariectomized rats. METHODS: Six-week-old female Sprague-Dawley rats were randomly assigned to either sham operation or bilateral ovariectomy. After surgery, they were divided into the following four groups: 1) sham-operated sedentary (S), 2) sham-operated exercise training (SE), 3) OVX sedentary (O), 4) OVX exercise training (OE) 5) OVX given 17ß-estradiol (OE2) and 6) OVX exercise training and given 17ß-estradiol (OEE). SE, OE and OEE rats were used extremely high-intensity swim exercise. The rats repeated fourteen 20-s swimming bouts with a weight equivalent to 14, 15, and 16% of body weight for the first 5, the next 9, and the last 5 days, respectively. Between exercise bouts, a 10-s pause was allowed. HIT was originally designed as an exercise method; a method that very quickly induces an increase in the maximum oxygen intake (Tabata I et al., 1996). OEE and OE2 rats were subcutaneously injected ethanol with 25µg/kg body weight 17ß-estradiol 3 times per week. RESULTS: Bone strength, bone mineral density and trabecular bone parameters were measured after a 8-weeks experimental period. Bone strength was significantly higher in the SE, OE, OE2 and OEE group compared with the O group. BV/TV was significant increase in the SE, OE groups compared with the O group. BMD showed no difference in the OE group compared with the O group. CONCLUSION: This study demonstrate some beneficial effects of postmenopausal osteoporosis of high-intensity intermittent swimming training on bone structure and strength.
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PURPOSE: we aim to examine whether adding exercise has impact on obesity prevention and bone metabolism in senior rats, to which dietary obesity was induced through skim milk intake. METHODS: We used 47, 14-week old Sprague -Dawley (SD) female rats (CLEA Japan, Inc.). The Rats were separated into four random groups: 1) a Non-Ex group with a normal diet (n = 12), 2) an Ex group with a normal diet (n = 12), 3) a Non-Ex group with a skim milk diet (n = 11), and 4) an Ex group with a skim milk diet (n = 12). As the exercise for each Ex group, rats ran on a treadmill starting at 27-week old (TREADMILL CONTROL LE8710 and TREADMILL CONTROL LE8700, Harvard Bioscience). Training protocol stipulated a frequency of five times a week for 12 weeks. RESULTS: The leptin concentration differed with dietary content: compared to the Ex group with a skim milk diet, Non-Ex and Ex groups with a normal diet showed significantly higher values (p < 0.05). The Ex group had significantly lower values in both the normal diet and skim milk diet groups with or without exercise (p < 0.05). Compared to the Non-Ex group with a normal diet, BS/BV (mm(2)/mm(3)), BV/TV (%), Tb.Th (µm), TBPf (/mm) and Tb.N (/mm) had significantly lower in the Ex group, the Ex and Non-Ex groups with a whey protein diet, and the Ex group with a skim milk protein diet (p < 0.05). CONCLUSION: These findings suggest that senior female rats fed SMP would have higher bone structural and strength parameters than rats fed a normal diet.
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BACKGROUND: This study aimed to determine the optimal number of steps per day needed to meet the current physical activity guidelines in a large population sample of Japanese adults. METHODS: An accelerometer-based activity monitor (Kenz Lifecorder) was used to simultaneously measure moderate-to-vigorous intensity physical activity (MVPA) and step counts in 940 Japanese adults (480 women) aged 20 to 69 years. The step count per day equivalents to 2 different physical activity recommendations (23 MET-h/wk and 150 min/wk of MVPA) were derived using linear regression analysis and receiver operating characteristic (ROC) methodology. RESULTS: Linear regression analysis showed that daily step counts correlated with weekly PAEE (r = .83) and daily minutes of MVPA (r = .83). Linear regression analysis also showed that 23 MET-h/wk of MVPA is equivalent to 11,160 steps/d, and 150 min/wk of MVPA is equivalent to 7716 steps/d. ROC analysis yielded similar findings: 10,225 steps/d are required to accumulate ≥ 23 MET-h/wk of MVPA and 7857 steps/d are needed to meet the recommendation of ≥ 150 min/wk of MVPA. CONCLUSIONS: The findings suggest that 10,000 to 11,000 and 7700 to 8000 steps/d represent the optimal thresholds for accumulating ≥ 23 MET-h/wk of MVPA and ≥ 150 min/wk of MVPA, respectively, for Japanese adults.
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Monitoreo Fisiológico/métodos , Acondicionamiento Físico Humano/normas , Caminata/fisiología , Adulto , Anciano , Estudios Transversales , Femenino , Guías como Asunto , Humanos , Japón , Modelos Lineales , Masculino , Persona de Mediana Edad , Curva ROC , Adulto JovenRESUMEN
We investigated the effects of two carbohydrate-based sports drinks on fluid intake and immunoendocrine responses to cycling. Six well-trained male cyclists completed trials on three separate days that involved cycling at 60% VO(2peak) for 90 min in hot conditions (28.1 ± 1.5ºC and 52.6 ± 3.1% relative humidity). During each trial, the subjects consumed ad libitum (1) an isotonic sports drink (osmolality 317 mOsm/kg), (2) a hypotonic sports drink (osmolality 193 mOsm/kg) or (3) plain water. The cyclists consumed significantly (p<0.05) more of the isotonic drink (1.23 ± 0.35 L) and hypotonic drink (1.44 ± 0.55 L) compared with water (0.73 ± 0.26 L). Compared with water (-0.96 ± 0.26 kg), body mass decreased significantly less after consuming the hypotonic drink (-0.50 ± 0.38 kg) but not the isotonic drink (-0.51 ± 0.41 kg). Blood glucose concentration was significantly higher at the end of the isotonic and hypotonic drink trials compared with the water trial. Neutrophil count and the plasma concentrations of catecholamines, interleukin 6 (IL-6), myeloperoxidase, calprotectin and myoglobin increased significantly during all three trials. IL-6 and calprotectin were significantly lower following the hypotonic drink trial compared with the water trial. In conclusion, hypotonic sports drinks are appealing for athletes to drink during exercise, and may help to offset fluid losses and attenuate some inflammatory responses to exercise.
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Ciclismo/fisiología , Deshidratación/prevención & control , Carbohidratos de la Dieta/administración & dosificación , Ingestión de Líquidos , Calor , Soluciones para Rehidratación/uso terapéutico , Equilibrio Hidroelectrolítico , Adulto , Bebidas , Glucemia/metabolismo , Catecolaminas/sangre , Deshidratación/sangre , Deshidratación/inmunología , Humanos , Humedad , Interleucina-6/sangre , Complejo de Antígeno L1 de Leucocito/sangre , Masculino , Mioglobina/sangre , Neutrófilos/metabolismo , Concentración Osmolar , Consumo de Oxígeno , Peroxidasa/sangre , Soluciones para Rehidratación/química , Soluciones para Rehidratación/farmacología , Estrés Fisiológico , Agua , Pérdida de Peso/fisiología , Adulto JovenRESUMEN
Previous studies have demonstrated that meeting the dietary recommendations for macronutrients was significantly associated with higher cardiorespiratory fitness (CRF) levels in adults. However, the relation between the status of micronutrient intake and CRF still remains unclear. This study examined the association between micronutrient intake status (based on adherence to the dietary reference intakes (DRI)) and CRF in Japanese men. The study comprised 373 Japanese men aged 30-69 years. Dietary intake was assessed with a self-administered diet history questionnaire. Overall micronutrient intake status was quantified using an overall nutrient adequacy score (ONAS) for thirteen selected micronutrients. ONAS was calculated based on adherence to the DRI for Japanese. CRF was defined as VÌO2max during a maximal incremental test on a bicycle ergometer. Physical activity was measured using accelerometer-based activity monitors for seven consecutive days. We observed a significant inverse trend for the prevalence of inadequacy for the intake of vitamin A and Ca across incremental CRF categories (P < 0·05). In a multivariate model, the ONAS was positively associated with absolute (ß = 0·10, P = 0·02) and relative VÌO2max (ß = 0·09, P = 0·04), independent of physical activity. The OR for being unfit (the lowest 25 % of the age-specific distribution of VÌO2max) in the third ONAS tertile compared with the first ONAS tertile was 0·52 (95 % CI 0·28, 0·96). These results demonstrated that the intake of several individual micronutrients and overall micronutrient intake status are independently and positively associated with CRF in Japanese men.
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BACKGROUND: Since it is essential to maintain a high level of cardiorespiratory fitness to prevent life-style related disease, the Ministry of Health, Labour and Welfare of Japan in 2006 proposed to determine the maximal oxygen uptake (Vo2max: mL.kg-1.min-1) reference values to prevent life-style related diseases (LSRD). Since muscle mass is one of the determinant factors of Vo2max, it could be used as the reference parameter for preventing LSRD. The aim of this study was to determine and quantify the muscle mass required to maintain the Vo2max reference values in Japanese women. METHODS: A total of 403 Japanese women aged 20-69 years were randomly allocated to either a validation or a cross-validation group. In the validation group, a multiple regression equation, which used a set of age and the percentage of muscle mass (%MM, percentage of appendicular lean soft tissue mass to body weight), as independent variables, was derived to estimate the Vo2max. After the equation was cross-validated, data from the two groups were pooled together to establish the final equation. The required %MM for each subject was recalculated by substituting the Vo2max reference values and her age in the final equation. RESULTS: The mean value of required %MM was identified as (28.5 +/- 0.35%). Thus, the present study proposed the required muscle mass (28.5% per body weight) in Japanese women to maintain the Vo2max reference values determined by the Japanese Ministry of Health Labour and Welfare. CONCLUSION: The estimated required %MM (28.5% per body weight) can be used as one of the reference parameters of fitness level in Japanese women.
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Ejercicio Físico/fisiología , Estilo de Vida , Músculo Esquelético/anatomía & histología , Consumo de Oxígeno , Adulto , Factores de Edad , Anciano , Antropometría , Composición Corporal/fisiología , Enfermedad Crónica/prevención & control , Estudios Transversales , Femenino , Humanos , Japón , Persona de Mediana Edad , Músculo Esquelético/fisiología , Valores de Referencia , Análisis de RegresiónRESUMEN
The present study was designed to determine the effects of various levels of capsaicin (CAP) on endurance capacity in forty-nine male Sprague-Dawley rats, aged 4 weeks, which were assigned to four groups. Rats were given orally either control (0) or 6, 10 or 15 mg CAP/kg body weight 2 h before exercise by stomach intubations using a round-ended needle. The rats in each group were divided into two subgroups for resting or swimming exercise. Swimming exercise was performed with a weight corresponding to 3 % body weight attached to the tail, and endurance capacity was evaluated by swimming time to exhaustion. The highest dose (15 mg/kg) of CAP significantly (P<0.05) increased endurance performance time and caused plasma non-esterified fatty acid to rise significantly by about 1.4-fold compared with that of non-CAP treated rats at exhaustion (P<0.05). The highest dose of CAP had no effect on liver and gastrocnemius muscle glycogen (white and red) in resting rats, but significantly increased glycogen contents of both muscles at exhaustion (P<0.05). At rest, plasma noradrenalin levels of the rats receiving the highest dose were greater than that of non-CAP-treated rats and remained greater until exhaustion. The effects of CAP on endurance capacity have received little attention and have conveyed conflicting impressions. Kim et al. (1997) failed to show the maximal effect of 10 mg/kg doses of CAP on swimming endurance time in mice. The influences of various doses of CAP on endurance capacity were still unclear. Matsuo et al. (1996) reported that the intake of CAP have little sparing effect on glycogen in the liver and soleus muscles at rest and during exercise in rats previously fed a CAP-containing diet ad libitum for 1 week. Our present results suggest more than the highest dose of CAP (15 mg/kg) can cause the increase of endurance capacity, which might be induced through the sparing of muscle glycogen and the rise of non-esterfied fatty acids following the increase of circulating catecholamine.
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Capsaicina/farmacología , Resistencia Física/efectos de los fármacos , Natación/fisiología , Animales , Catecolaminas/sangre , Relación Dosis-Respuesta a Droga , Ácidos Grasos no Esterificados/sangre , Glucógeno/metabolismo , Masculino , Fatiga Muscular , Músculo Esquelético/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
The influences of various doses of capsaicin on endurance capacity remain to be clarified. The purpose of this study was to determine whether or not capsaicin delays stored tissue glycogen depletion. Rats were orally given either a vehicle or a dose of capsaicin, 6, 10, or 15 mg/kg of body weight, 2 h before exercise. The rats in each group were divided into three subgroups for resting and swimming exercise (30 min, exhaustion). Swimming exercises were performed with a weight corresponding to 3% body weight attached to the tail, and the endurance capacity was evaluated by the swimming time until exhaustion. The 15 mg/kg dose of capsaicin significantly (p < 0.05) enhanced the endurance performance time and plasma concentration of epinephrine, norepinephrine, free fatty acid and glucose rose to significantly higher levels within 30 min; swimming exercise compared to rest (p < 0.05). At the 15 mg/kg capsaicin dosage. the plasma insulin level decreased to significantly lower levels in group subjected to 30-min swimming as compared to the resting group (p < 0.05), while plasma glucagon rose to a significantly higher level (p < 0.05). Liver and gastrocnemius muscle glycogen in the group subjected to 30-min swimming was maintained at significantly higher concentrations in the rats fed 15 mg/kg of capsaicin as compared to the vehicle counterparts (p < 0.05). These results suggest that the improvement in swimming endurance with the high capsaicin dosage is caused by an increase in fatty acid utilization as the energy source, resulting in the sparing of glycogen.
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Capsaicina/farmacología , Glucógeno/metabolismo , Lipólisis/efectos de los fármacos , Resistencia Física/efectos de los fármacos , Análisis de Varianza , Animales , Glucemia/metabolismo , Capsaicina/sangre , Relación Dosis-Respuesta a Droga , Epinefrina/sangre , Ácidos Grasos no Esterificados/sangre , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Norepinefrina/sangre , Hormonas Pancreáticas/sangre , Ratas , Ratas Sprague-Dawley , Natación/fisiologíaRESUMEN
We have demonstrated that the habitual intake of chitosan can decrease bone mass in ovariectomized (OVX) SHRSP rats fed a low-Ca diet (0.1%). In the present study, we examined both the etiology of bone loss induced by dietary chitosan and the preventive effect of vitamin C supplementation. Rats were OVX and maintained on one of the following diets for 6 wk: 10% cellulose (CE). 10% chitosan (CH) or 10% chitosan with sodium ascorbate (CHVC). CH caused a significant reduction in bone mineral density (BMD) and stiffness in femurs and the fourth lumbar vertebrae (L4). There was no significant difference in intestinal Ca absorption between CH and CE, whereas CH intake significantly reduced intestinal P absorption. The bone loss in CH rats was accompanied with an increase in urinary Ca excretion and a decrease in serum Ca as well as a significant increment In serum PTH and 1,25(OH)2D3. The vitamin D receptor and calcium binding protein D9K mRNAs were also significantly increased in the duodenum of CH rats. Vitamin C supplementation to CH caused an increase in the Ca and P contents of femurs as well as BMD of the L4, with a decrease in urinary Ca excretion. These results indicate that dietary chitosan with low Ca intake possibly induces the loss of bone mass by enhancing urinary Ca excretion rather than by inhibiting Ca absorption, and that vitamin C supplementation could prevent bone loss caused by chitosan through the increment of retained Ca followed by suppression of urinary Ca excretion.