RESUMO

We aimed to provide evidence for an a priori hypothesis and sample size for subjectively assessing physical activity intensity and duration in paediatric population, adopting objective methods as the reference. We searched electronic databases, reference lists and author databases. Correlation coefficients were pooled as an indicator of agreement estimates. We found 183 agreement analyses (94.5% based on correlation coefficients) from 89 studies that met our inclusion criteria. We identified four physical activity parameters addressing intensity and two parameters addressing duration. The physical activity parameters focusing on intensity were measured only by questionnaires, and the best correlation was achieved by moderate-to-vigorous physical activity compared with a heart rate monitor. In addition, total physical activity duration had a stronger correlation with an accelerometer when measured by diaries or logs than when measured by questionnaires. In both cases, the correlation was moderate. Studies with sample sizes between 50 and 99 subjects showed measurements that were stable in both magnitude and interpretation. Our findings suggest that the agreement between subjective and objective methods for assessing physical activity intensity and duration is weak to moderate. Furthermore, sample sizes ranging from 50 to 99 subjects provide stable agreement estimates between methods.

Assuntos

Assuntos

RESUMO

OBJECTIVES: The aims of this study were twofold: (i) to model changes in body mass index (BMI) of 10-18-year-old adolescents, and (ii) to investigate the effects of total physical activity (TPA), physical fitness (PF), sleep duration and fruit/vegetable consumption in BMI trajectories across time. METHODS: Data were obtained from the Oporto Growth, Health and Performance Study and comprised 6894 adolescents (3418 girls) divided into four age cohorts (10, 12, 14 and 16 years) measured annually for 3 years. BMI was computed using the standard formula (kg m(-2)); TPA was estimated with the Baecke questionnaire; PF measures included 1-mile run/walk, 50 yard dash (50YD), standing long jump (SLJ), handgrip strength (HGr) and agility shuttle run. Longitudinal changes in BMI were analyzed using the multilevel modeling approach. RESULTS: The average BMI at age of peak of height velocity was 20.7±0.07 kg m(-2) for girls (P<0.001) and 20.58±0.06 kg m(-2) for boys (P<0.001). The annual increment in BMI was 1.36±0.04 kg m(-2), P<0.001 and 1.23±0.03 kg m(-2), P<0.001 for girls and boys, respectively. PF were related to BMI trajectories in both sexes (Girls: ß1mile=0.12±0.02, P<0.001; ßSLJ=-0.01±0.00, P<0.001; ß50YD=0.28±0.05, P<0.001; ßHGr=-8.91±0.54, P<0.001; Boys: ß1mile=0.18±0.02, P<0.001; ßSLJ=-0.01±0.00, P<0.001; ß50YD=0.26±0.04, P<0.001; and ßHGr=-8.15±0.45, P<0.001). TPA only showed significant, but positive, association with girls' BMI trajectories (ß=0.10±0.03, P=0.001). After adjusting for the covariates, sleep duration and fruit/vegetable intake did not show any significant association with BMI trajectories either sex. CONCLUSIONS: BMI increased linearly with age in both gender. PF levels are negatively associated with BMI across time in both boys and girls. Therefore, promotion of PF in the adolescent years seems to be effective in the early prevention of obesity.

Assuntos

RESUMO

To compare post-resistance exercise hypotension (PREH) and its mechanisms in normotensive and hypertensive individuals, 14 normotensives and 12 hypertensives underwent two experimental sessions: control (rest) and exercise (seven exercises, three sets, 50% of one repetition maximum). Hemodynamic and autonomic clinic measurements were taken before (Pre) and at two moments post-interventions (Post 1: between 30 and 60 min; Post 2: after 7 h). Ambulatory blood pressure (BP) was monitored for 24 h. At Post 1, exercise decreased systolic BP similarly in normotensives and hypertensives (-8 ± 2 vs -13 ± 2 mmHg, P > 0.05), whereas diastolic BP decreased more in hypertensives (-4 ± 1 vs -9 ± 1 mmHg, P < 0.05). Cardiac output and systemic vascular resistance did not change in normotensives and hypertensives (0.0 ± 0.3 vs 0.0 ± 0.3 L/min; -1 ± 1 vs -2 ± 2 U, P > 0.05). After exercise, heart rate (+13 ± 3 vs +13 ± 2 bpm) and its variability (low- to high-frequency components ratio, 1.9 ± 0.4 vs +1.4 ± 0.3) increased whereas stroke volume (-14 ± 5 vs -11 ± 5 mL) decreased similarly in normotensives and hypertensives (all, P > 0.05). At Post 2, all variables returned to pre-intervention, and ambulatory data were similar between sessions. Thus, a session of resistance exercise promoted PREH in normotensives and hypertensives. Although this PREH was greater in hypertensives, it did not last during the ambulatory period, which limits its clinical relevance. In addition, the mechanisms of PREH were similar in hypertensives and normotensives.

Assuntos

RESUMO

This study investigated the effect of the dihydropyridine calcium channel antagonist, amlodipine, on blood pressure (BP) during resistance exercise performed at different intensities in hypertensives. Eleven hypertensives underwent 4 weeks of placebo and amlodipine (random double-blinded crossover design). In each phase, they performed knee extension exercise until exhaustion following three protocols: one set at 100% of 1 RM (repetition maximum), three sets at 80% of 1 RM, and three sets at 40% of 1 RM. Intraarterial BP was measured before and during exercise. Amlodipine reduced maximal systolic/diastolic BP values achieved at all intensities (100% = 225 ± 6/141 ± 3 vs. 207 ± 6/130 ± 6 mmHg; 80% = 289 ± 8/178 ± 5 vs. 273 ± 10/169 ± 6 mmHg; 40% = 289 ± 10/176 ± 8 vs. 271 ± 11/154 ± 6 mmHg). Amlodipine blunted the increase in diastolic BP that occurred during the second and third sets of exercise at 40% of 1RM (+75 ± 6 vs. +61 ± 5 mmHg and +78 ± 7 vs. +64 ± 5 mmHg, respectively). Amlodipine was effective in reducing the absolute values of systolic and diastolic BP during resistance exercise and in preventing the progressive increase in diastolic BP that occurs over sets of low-intensity exercise. These results suggest that systemic vascular resistance is involved in BP increase during resistance exercise, and imply that hypertensives receiving amlodipine are at lower risk of increased BP during resistance exercise than non-medicated patients.

Assuntos

RESUMO

Due to differences in study populations and protocols, the hemodynamic determinants of post-aerobic exercise hypotension (PAEH) are controversial. This review analyzed the factors that might influence PAEH hemodynamic determinants, through a search on PubMed using the following key words: "postexercise" or "post-exercise" combined with "hypotension", "blood pressure", "cardiac output", and "peripheral vascular resistance", and "aerobic exercise" combined only with "blood pressure". Forty-seven studies were selected, and the following characteristics were analyzed: age, gender, training status, body mass index status, blood pressure status, exercise intensity, duration and mode (continuous or interval), time of day, and recovery position. Data analysis showed that 1) most postexercise hypotension cases are due to a reduction in systemic vascular resistance; 2) age, body mass index, and blood pressure status influence postexercise hemodynamics, favoring cardiac output decrease in elderly, overweight, and hypertensive subjects; 3) gender and training status do not have an isolated influence; 4) exercise duration, intensity, and mode also do not affect postexercise hemodynamics; 5) time of day might have an influence, but more data are needed; and 6) recovery in the supine position facilitates systemic vascular resistance decrease. In conclusion, many factors may influence postexercise hypotension hemodynamics, and future studies should directly address these specific influences because different combinations may explain the observed variability in postexercise hemodynamic studies.

Assuntos

RESUMO

Due to differences in study populations and protocols, the hemodynamic determinants of post-aerobic exercise hypotension (PAEH) are controversial. This review analyzed the factors that might influence PAEH hemodynamic determinants, through a search on PubMed using the following key words: “postexercise” or “post-exercise” combined with “hypotension”, “blood pressure”, “cardiac output”, and “peripheral vascular resistance”, and “aerobic exercise” combined only with “blood pressure”. Forty-seven studies were selected, and the following characteristics were analyzed: age, gender, training status, body mass index status, blood pressure status, exercise intensity, duration and mode (continuous or interval), time of day, and recovery position. Data analysis showed that 1) most postexercise hypotension cases are due to a reduction in systemic vascular resistance; 2) age, body mass index, and blood pressure status influence postexercise hemodynamics, favoring cardiac output decrease in elderly, overweight, and hypertensive subjects; 3) gender and training status do not have an isolated influence; 4) exercise duration, intensity, and mode also do not affect postexercise hemodynamics; 5) time of day might have an influence, but more data are needed; and 6) recovery in the supine position facilitates systemic vascular resistance decrease. In conclusion, many factors may influence postexercise hypotension hemodynamics, and future studies should directly address these specific influences because different combinations may explain the observed variability in postexercise hemodynamic studies.

Assuntos

RESUMO

Post-resistance exercise hypotension has been extensively described in men and women. However, gender influence on this response has not yet been clear. Gender might change post-exercise hemodynamics, since men and women respond differently during exercise. Thus, the purpose was to compare post-resistance exercise hypotension and its hemodynamic determinants in men and women. Normotensive subjects (22-male, 22-female) underwent 2 sessions: control (40 min of rest) and exercise (6 resistance exercises, 3 sets, 20 repetitions, at 40-50% of 1RM). Blood pressure, heart rate, and cardiac output were measured prior to and following interventions. Blood pressure decrease after exercise was similar between the genders. However, hemodynamic determinants responded differently in men and women. Systemic vascular resistance reduced in women (-4.6±1.9U, P<0.05), while cardiac output decreased in men (-0.6±0.2 L/min, P<0.05). This response was accompanied by a decrease in stroke volume in men (-21.6±5.1 ml, P<0.05) and a more pronounced increase in heart rate in men than in women (+11.3±1.3 vs. +6.5±1.7 bpm, P<0.05, respectively). In conclusion, post-resistance exercise hypotension was similar in men and women. However, its hemodynamic determinants differ between the genders, depending on cardiac output decrease in men and on systemic vascular resistance decrease in women.

Assuntos

RESUMO

The purpose of this study was to investigate the effect of resistance training on resting blood pressure and heart rate variability in elderly postmenopausal women. 29 untrained, non-hypertensive elderly women were randomly assigned to 2 groups: an intervention group (n=15, 65.5±5.0 years, 57.3±6.5 kg, 156.7±5.1 cm) that underwent a supervised resistance training program (8 exercises, 2 sets, 10-15 repetitions, 3 times/week) or a control group (n=14, 66.2±4.1 years, 61.1±11.7 kg, 157.5±7.1 cm) that participated in a supervised stretching program (25-30 min/session, 2 times/week). Resting auscultatory blood pressure, heart rate variability, evaluated from short recordings in a seated position, and maximal dynamic strength (1-RM test) were measured at baseline and after 12 weeks. A group x time ANOVA revealed that muscular strength increased significantly in the resistance training group (+ 10.2% for bench press and +12.7% for leg extension, P<0.05). Systolic blood pressure was reduced significantly in the resistance training group from pre- to post-intervention period (- 5 mmHg; P<0.05), while no significant effect was noted for diastolic blood pressure and heart rate variability indexes (P>0.05). None of these variables changed in the control group throughout the study. In conclusion, a supervised resistance training program improved muscular strength and reduced systolic blood pressure without affecting diastolic blood pressure and heart rate variability in elderly postmenopausal women.

Assuntos

RESUMO

Moderate- to high-intensity strength training is recommended for healthy adults. In young subjects, a single session of strength training decreases blood pressure, while heart rate and cardiac work remain elevated afterwards. However, these effects have not been clearly demonstrated in elderly subjects. To investigate this issue, 16 elderly subjects each underwent a Control and an Exercise (3 sets, 8 RM, 9 exercises) session conducted in random order. Haemodynamic variables and heart rate variability were measured before and after the interventions. Systolic blood pressure did not change after the exercise session but did increase after the control session (+8.1±1.6 mm Hg, P≤0.05). Diastolic blood pressure, as well as systemic vascular resistance increased similarly after both sessions. Cardiac output and stroke volume decreased, while heart rate, rate-pressure product and the low- to high-frequency ratio of heart rate variability increased only after the exercise session ( - 0.5±0.1 L/min, - 9.3±2.0 ml,+3.8±1.6 bpm, +579.3±164.1 mmHg.bpm and +0.71±0.34, P≤0.05). Ambulatory blood pressure was similar after both sessions, while heart rate and rate pressure product remained higher after the exercise session for up to 4.5 h. After a single session of strength training, cardiac sympathetic modulation and heart rate remain elevated in elderly subjects, keeping cardiac work elevated for a long period of time.

Assuntos