James W. Navalta

Predictors of calcium retention in adolescent boys

CONTEXT The relationship between calcium (Ca) intake and Ca retention in adolescent boys was recently reported. OBJECTIVE This study evaluated the influence of Ca intake, serum hormone levels, biomarkers of bone metabolism, habitual physical activity, habitual Ca intake, and physical fitness on Ca retention in the same sample. DESIGN This study was a randomized, cross-over design that consisted of two 3-wk metabolic balance periods. SETTING The study took place on a university campus as a summer camp. PATIENTS OR OTHER PARTICIPANTS A total of 31 American white boys (13-15 yr) participated in the study. INTERVENTIONS Each subject consumed a controlled diet with one of five high-low Ca intake pairs that ranged from 670-2003 mg/d, which was manipulated utilizing a fortified beverage. MAIN OUTCOME MEASURES Ca retention was determined by Ca intake minus urinary and fecal Ca excretion during each balance period. RESULTS Ca intake explained 21.7% of the variability in Ca retention, and serum IGF-I concentration explained an additional 11.5%. Other serum hormone levels did not significantly add to the model. Biomarkers of bone metabolism, habitual physical activity, habitual Ca intake, and physical fitness were not significant predictors of Ca retention in adolescent boys. CONCLUSIONS IGF-I, a regulator of growth during puberty, is an important predictor of Ca retention in adolescent boys. However, dietary Ca intake is an even greater predictor of Ca retention during this period of growth.

Association of body composition with sarcopenic obesity in elderly women

The aim of the present study was to investigate the prevalence of sarcopenic obesity and its association with obesity and sarcopenia in elderly Brazilian women. Two hundred and seventy-two sedentary women with a mean age of 66.75 ± 5.38 years were recruited for participation in this study. Obesity was determined by both body mass index and dual-energy X-ray absorptiometry (DXA) evaluations. Sarcopenic obesity diagnosis was established from the ratio between fat-free mass and body surface area as obtained by DXA. There was no association of obesity with sarcopenic obesity (P = 0.424). In contrast, sarcopenia was significantly related to sarcopenic obesity (P < 0.001), although most of the elderly women with sarcopenia (n = 171) did not exhibit sarcopenic obesity. These results highlight the importance of diagnosing sarcopenic obesity as elderly women exhibiting sarcopenia could be either eutrophic or obese.

Decreased functional capacity and muscle strength in elderly women with metabolic syndrome

Purpose To compare the metabolic parameters, flexibility, muscle strength, functional capacity, and lower limb muscle power of elderly women with and without the metabolic syndrome (MetS). Methods This cross-sectional study included 28 older women divided into two groups: with the MetS (n = 14; 67.3 ± 5.5 years; 67.5 ± 16.7 kg; 1.45 ± 0.35 m; 28.0 ± 7.6 kg/m2), and without the MetS (n = 14; 68.7 ± 5.3 years; 58.2 ± 9.9 kg; 1.55 ± 0.10 m; 24.3 ± 3.8 kg/m2). Body composition was evaluated by dual-energy X-ray absorptiometry and dynamic muscle strength was assessed by one-maximum repetition (1RM) tests in leg press, bench press and biceps curl exercises. Six-minute walk test, Timed Up and Go (TUG); 30-second sitting-rising; arm curl using a 2-kg dumbbell, sit-and-reach (flexibility), and vertical jump tests were performed. Results There was no difference between groups regarding age (P = 0.49), height (P = 0.46), body fat (%) (P = 0.19), systolic (P = 0.64), diastolic (P = 0.41) and mean blood pressure (P = 0.86), 30-second sitting-rising (P = 0.57), 30-s arm curl (P = 0.73), leg press 1RM (P = 0.51), bench press 1RM (P = 0.77), and biceps curl 1RM (P = 0.85). However, women without the MetS presented lower body mass (P = 0.001), body mass index (BMI) (P = 0.0001), waist circumference (P = 0.02), waist-to-height ratio (P = 0.02), fat body mass (kg) (P = 0.05), lean body mass (kg) (P = 0.02), blood glucose (P = 0.05), triglycerides (P = 0.03), Z-score for the MetS (P = 0.05), higher high-density lipoprotein-cholesterol (HDL-C) (P = 0.002), better performance on TUG (P = 0.01), flexibility (P = 0.03), six-minute walk test (P = 0.04), vertical jump (P = 0.05) and relative muscle strength for leg press (P = 0.03), bench press (P = 0.04) and biceps curl (P = 0.002) exercises as compared to women with the MetS. Conclusion Elderly women with the MetS have higher metabolic risk profile and lower functional capacity, muscle strength, lower limb power and flexibility as compared to women without the MetS. The evaluation of functional capacity may help to determine the degree of physical decline in older persons with the MetS, while exercise interventions should be encouraged.

Effects of combined exercise training on immunological, physical and biochemical parameters in individuals with HIV/AIDS

Abstract The practice of exercise has shown to be beneficial to quality of life of individuals with HIV/AIDS. Thus, the present study analysed the effects of a combined exercise training in persons living with HIV/AIDS. Ten participants participated in the present study. The following variables were analysed: viral load and cell counts for TCD4+/TCD8; maximal oxygen consumption (VO2max); total mass, absolute fat mass, relative fat mass, absolute lean mass, relative lean mass and body mass index; fasting glycaemia, fasting insulinaemia, homeostatic model assessment (HOMA) index (insulin resistance – homeostatic model assessment (IR-HOMA)); total cholesterol, triglycerides, high-density lipoprotein (HDL), very low-density lipoprotein (VLDL), low-density lipoprotein (LDL); superoxide dismutase, catalase, glutathione peroxidase activities; thiobarbituric acid reactive substances. The combined exercise training consisted of resistance exercises plus aerobic training (60 min · session−1, three times per week, during 20 weeks). The number of TCD4+ cells, absolute lean mass and relative lean mass, muscle strength for the 45° leg press, seated row and triceps extension, HDL-c levels as well as VO2max increased post-training. The activity of superoxide dismutase, catalase, glutathione peroxidase enzymes and thiobarbituric acid reactive substances levels were diminished post-training. Finally, it can be concluded that combined exercise training is able to change positively several variables related to health of individuals with HIV/AIDS, mainly the immune system as well as antioxidant mechanisms re-establishment.

Acute effects of resistance exercise on 24-h blood pressure in middle aged overweight and obese women.

This investigation was designed to evaluate responses of blood pressure (BP) following an acute resistance exercise (RE) session. Middle-aged women (N=13) who were classified as overweight (N=8) or obese (N=5) according to body mass index (BMI) participated in the investigation. Participants were randomly submitted to a control session (30-min seated rest) and a exercise session (3 sets, 10 repetitions at 60% 1RM of exercises for the upper and lower body) with systolic (SBP), diastolic (DBP) and mean blood pressure (MBP) obtained at rest and 10, 20, 30, 40, 50, and 60-min following exercise, and through 24 h. Acute RE decreased SBP at 10, 30, and 40-min compared with pre-exercise and control (P<0.05). DBP decreased at 10 and 40-min post-exercise compared with the control trial (P<0.05). Both SBP and DBP decreased in the nighttime period (-4.2 mmHg and -4.1 mmHg, respectively) and in the overall 24 h period (-3.6 mmHg and -4.5 mmHg, respectively) following the acute RE session when compared with the control trial. These findings indicate important benefits of acute RE on BP circadian rhythm, particularly at night as well as in the morning, which are critical periods associated with increased risk for cardiovascular events.

Neither gender nor menstrual cycle phase influences exercise-induced lymphocyte apoptosis in untrained subjects

Lymphocyte apoptosis increases following maximal exercise. Estrogen hormones (E2) have been shown to protect lymphocytes from apoptosis in vitro, but it is unknown whether they can attenuate the apoptotic response to maximal exercise. The purpose of this study was to examine the effect of menstrual cycle variation on exercise-induced lymphocyte apoptosis in humans following exercise. Untrained healthy young men and regularly menstruating women not using hormonal contraceptives volunteered for the study. Women performed a maximal effort treadmill test for VO2 max once in the follicular phase (FOL) and once in the mid-luteal phase (ML) of their cycles. Men completed two VO2 max tests with periods of time between tests matched to those of the female subjects. Blood was collected before (PRE) and immediately after exercise (POST), and analyzed for apoptotic lymphocytes and estradiol. E2 concentrations in women were significantly greater during ML versus during FOL, both PRE and POST (p<0.0001). The percent of exercise-induced lymphocyte apoptosis was similar between women (23.2%+/-1.0%) and men (21.5%+/-0.4%). In women, the apoptotic response to maximal exercise was similar regardless of menstrual cycle phase (FOL=23.7%+/-0.9%, ML=22.7%+/-1.1%). Although elevated female sex hormones in vitro may exert anti-apoptotic effects, these data suggest that in vivo concentrations confer no protection to lymphocytes during exhaustive exercise.

Acute effects of resistance training on cytokines and osteoprotegerin in women with metabolic syndrome

Chronic inflammation has been identified as an important component of metabolic syndrome (MetS). Inhibition of the inflammatory mediator signals is a promising strategy against insulin resistance, atherosclerosis and other problems associated with MetS. Regular exercise decreases the components associated with MetS, including inflammatory cytokines. However, the relationship between an acute resistance training (RT) session, cytokine levels and MetS is unclear. Therefore, the aim was to evaluate the effects of a single bout of acute RT on tumour necrosis factor (TNF‐α), interleukins (IL) IL‐1a, IL‐1β, IL‐12, IL‐6, IL‐10 and osteoprotegerin (OPG) in women with MetS. Twenty‐four women were divided into 2 groups: metabolic syndrome (MetS) and non‐metabolic syndrome (Non‐MetS). After the familiarization and testing for 1 repetition maximum (1RM), participants completed 3 sets of 10 repetitions in the following exercises: machine leg press, leg extension, leg curl, chest press, lat front pull‐down and machine shoulder press with 60% of 1RM followed by 15 repetitions of abdominal crunches. A rest interval of 1 min was allowed between sets and exercises. Plasma TNF‐α, IL‐1a, IL‐1β, IL‐12, IL‐6, IL‐10 and OPG were measured before, immediately post and 60 min after RT. MetS group showed significantly higher concentrations of IL‐1β (P = 0·024) and IL‐6 (P = 0·049) and a trend for higher TNF‐α values (P = 0·092) compared with Non‐MetS. There was no group × time interactions after the RT session on the measured cytokines and osteoprotegerin. In conclusion, acute RT session induced no additional increase in pro‐inflammatory cytokines nor a decrease in anti‐inflammatory cytokines and OPG in women with MetS.

Blood treatment influences the yield of apoptotic lymphocytes after maximal exercise.

PURPOSE No systematic investigation has been reported assessing the effect of cell isolation processes on postexercise apoptosis. Therefore, the effect of cell isolation procedures on apoptosis was evaluated in this study. METHODS Untrained healthy individuals participated (N=13). Blood samples obtained at rest and immediately after an incremental exercise test to exhaustion were partitioned into three treatments: 1) whole blood smears made immediately after the sample was obtained (WB), 2) cells subjected to density-gradient isolation before smears were made (ISO), and 3) samples allowed to sit at room temperature (i.e., time-treated) before centrifugation and smearing (TT). Blood smears were stained using the May-Grünwald Giemsa procedure and lymphocytes were evaluated under a light microscope for characteristic features of apoptosis. Data were analyzed using a 2x3 ANOVA. RESULTS A significant interaction effect existed (P<0.0001) such that at rest, no difference was detected in the amount of lymphocyte apoptosis among WB, ISO, or TT samples. However, after exhaustive exercise, the amount of apoptotic lymphocytes was significantly greater in WB compared with ISO and TT samples (P<0.0001). CONCLUSION Lymphocyte isolation results in a significant decrease in the percent of apoptotic lymphocytes after exhaustive exercise. This reduction is likely due to the time needed to isolate cells, rather than the isolation process itself. Because apoptosis is a time-sensitive process that occurs within minutes rather than hours, the length of time from initial sampling to the preparation of cells for assessment of apoptosis is critical and should be considered in future exercise studies.

Understanding the individual responsiveness to resistance training periodization

This study was designed to compare the effects of linear periodization (LP) and undulating periodization (UP) on functional capacity, neuromuscular function, body composition, and cytokines in elderly sedentary women. We also aimed to identify the presence of high responders (HR), medium responders (MR), and low responders (LR) for irisin, interleukin-1 beta (IL-1β), toll-like receptor-4 (TLR-4), and brain-derived neurotrophic factor (BDNF) to resistance training (RT). Forty-nine elderly women were assigned to a control group, LP, and UP scheme. Functional capacity, body composition, maximal strength, irisin, TLR-4, BDNF, and IL-1β were evaluated. Both periodization models were effective in improving 45° leg press 1RM, chair-stand, arm curl, and time-up and go tests, with no significant differences in body composition and cytokines. Furthermore, HR, MR, and LR were identified for irisin, IL-1β, TLR-4, and BDNF, with differences between groups and moments. This study provides evidence that both periodization models were effective in improving functional capacity and neuromuscular function, with no effect on body composition and cytokines (probably as a consequence of the different responsiveness). Furthermore, for the first time, HR, MR, and LR were identified for irisin, IL1-β, TLR-4, and BDNF in response to RT.

Core stabilization exercises enhance lactate clearance following high-intensity exercise.

Dynamic activities such as running, cycling, and swimming have been shown to effectively reduce lactate in the postexercise period. It is unknown whether core stabilization exercises performed following an intense bout would exhibit a similar effect. Therefore, this study was designed to assess the extent of the lactate response with core stabilization exercises following high-intensity anaerobic exercise. Subjects (N = 12) reported twice for testing, and on both occasions baseline lactate was obtained after 5 minutes of seated rest. Subjects then performed a 30-second Win- gate anaerobic cycle test, immediately followed by a blood lac- tate sample. In the 5-minute postexercise period, subjects either rested quietly or performed core stabilization exercises. A final blood lactate sample was obtained following the 5-minute intervention period. Analysis revealed a significant interaction (p = 0.05). Lactate values were similar at rest (core = 1.4 ± 0.1, rest = 1.7 ± 0.2 mmol·L−1) and immediately after exercise (core = 4.9 ± 0.6, rest = 5.4 ± 0.4 mmol·L−1). However, core stabilization exercises performed during the 5-minute postexercise period reduced lactate values when compared to rest (5.9 ± 0.6 vs. 7.6 ± 0.8 mmol·L−1). The results of this study show that performing core stabilization exercises during a recovery period significantly reduces lactate values. The reduction in lactate may be due to removal via increased blood flow or enhanced uptake into the core musculature. Incorporation of core stability exercises into a cool-down period following muscular work may result in benefits to both lactate clearance as well as enhanced postural control.