Paul J. Arciero

Leptin concentrations experience a delayed reduction after resistance exercise in men.

PURPOSE Leptin is an important metabolic hormone providing the brain with information concerning energy balance. Most studies have reported that circulating leptin concentrations are unaltered by acute, moderate exercise. We hypothesized that these studies have been limited by short sampling schemes (<4 h) postexercise and may have missed a time-delayed reduction in circulating leptin concentrations. METHODS Ten men (age = 21 +/- 1 yr, height = 177 +/- 2 cm, body mass = 79 +/- 3 kg, body fat = 11 +/- 1%BF, .VO(2max) = 51 +/- 1 mL.kg-1.min-1) completed an acute heavy-resistance exercise protocol (AHREP) (50 total sets comprised of the squat, bench press, leg press, and lat pull-down) from 1500 to 1700 h. Blood was sampled hourly postexercise until 0600 h the next morning and also during a time-matched control period. Leptin concentrations were measured by an immunoradiometric assay. Resting energy expenditure (REE) was measured via indirect calorimetry using a ventilated hood beginning approximately 0600 h after both overnight conditions. RESULTS The estimated caloric expenditure from the AHREP was 856 +/- 114 kcal. No significant differences (P > 0.05) between the control and exercise conditions were observed for serum leptin concentrations until 9 h postexercise. Significant interaction effects (P < 0.05) indicated lower serum leptin concentrations postexercise at hours 9 (2.9 vs 2.2 ng.mL-1), 10 (2.7 vs 2.0 ng.mL-1), 12 (2.5 vs 1.8 ng.mL-1), and 13 (2.6 vs 1.8 ng.mL-1). This delayed reduction was accompanied by a 12% elevation (P < 0.05) in morning-after REE (0.25 +/- 0.02 vs 0.28 +/- 0.02 L.min-1). CONCLUSION Leptin concentrations experience a delayed ( approximately 9 h) reduction in the systemic circulation after acute resistance exercise. This decline is likely associated with the disruption in metabolic homeostasis created by the high-intensity, long-duration, energy expenditure and subsequent excess post oxygen consumption from the AHREP and is not due to losses in fat mass.

Moderate protein intake improves total and regional body composition and insulin sensitivity in overweight adults

A high protein intake (approximately 40% of energy intake) combined with aerobic and resistance exercise training is more closely associated with improved body composition and cardiovascular risk profile than a traditional protein intake (approximately 15% of intake) combined with moderate-intensity aerobic exercise. However, there is concern that such high-protein diets may adversely affect health. We therefore tested the hypothesis that moderate protein intake (approximately 25% of energy intake) would elicit similar benefits on body composition and metabolic profile as high protein intake. Twenty-four overweight/obese men and women (body mass index [BMI] = 32.2 +/- 3.4, percentage of body fat [%BF] = 37.3 +/- 8.0) were matched for BMI and %BF and randomly assigned to one of 3 groups for a 3-month nutrition/exercise training intervention: (1) high-protein diet (approximately 40% of energy intake) and combined high-intensity resistance and cardiovascular training (HPEx, n = 8, 5 female and 3 male), (2) moderate-protein diet (approximately 25% of energy intake) and combined high-intensity resistance and cardiovascular training (MPEx, n = 8, 5 female and 3 male), or (3) high-protein diet only (HPNx, n = 8, 5 female and 3 male). Total and regional body composition (dual-energy x-ray absorptiometry), insulin sensitivity (insulin sensitivity index to the oral glucose tolerance test), insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), IGF binding protein-3 (IGFBP-3), and blood lipids were measured at baseline and after the intervention. All groups experienced significant (P < .05) and similar losses of body weight, BMI, and total and abdominal %BF, and similar improvements in insulin sensitivity (HPEx, 6.3 +/- 1.2 vs 9.5 +/- 0.98; MPEx, 6.2 +/- 1.4 vs 8.4 +/- 1.6; HPNx, 3.7 +/- 1.1 vs 7.0 +/- 1.1; insulin sensitivity index to the oral glucose tolerance test; P < .05) and leptin levels. Furthermore, the HPEx group demonstrated decreases in total cholesterol (TC) and triglycerides, and increases in IGF-1 and IGFBP-1. The MPEx group experienced decreases in TC, whereas the HPNx group had increases in high-density lipoprotein cholesterol, TC to high-density lipoprotein, IGF-1, and IGFBP-1. In conclusion, moderate protein intake elicits similar benefits in body composition and insulin sensitivity as a high-protein diet. These findings may have practical implications for individuals interested in diets containing elevated dietary protein.

A Practical Equation to Predict Resting Metabolic Rate in Older Females

Objective: To develop a practical and accurate age‐specific equation for predicting resting metabolic rate (RMR) in older women and, thereafter, to cross‐validate existing equations for predicting RMR in older females.

Increased protein intake and meal frequency reduces abdominal fat during energy balance and energy deficit

Unrefined, complex carbohydrates and lean protein diets are used to combat obesity, although its unknown whether more frequent meals may improve this response. The effects of consuming traditional (∼15%) versus higher (∼35%) protein intakes as three or six meals/day on abdominal fat, postprandial thermogenesis (TEM), and cardiometabolic biomarkers in overweight individuals during 28 days of energy balance (BAL) and deficit (NEG), respectively were compared.

Social facilitation in virtual reality-enhanced exercise: competitiveness moderates exercise effort of older adults.

This study examined the effect of virtual social facilitation and competitiveness on exercise effort in exergaming older adults. Fourteen exergaming older adults participated. Competitiveness was assessed prior to the start of exercise. Participants were trained to ride a “cybercycle;” a virtual reality-enhanced stationary bike with interactive competition. After establishing a cybercycling baseline, competitive avatars were introduced. Pedaling effort (watts) was assessed. Repeated measures ANOVA revealed a significant group (high vs low competitiveness) × time (pre- to post-avatar) interaction (F[1,12] = 13.1, P = 0.003). Virtual social facilitation increased exercise effort among more competitive exercisers. Exercise programs that match competitiveness may maximize exercise effort.

Plasma adiponectin and insulin sensitivity in overweight and normal-weight middle-aged premenopausal women

Adiponectin has been reported to regulate systemic insulin sensitivity as a part of a broader control mechanism in energy balance. However, it is not clear whether adiponectin exerts its positive effects on insulin sensitivity equally in a wide range of obesity. We investigated the association of plasma adiponectin concentration with insulin resistance (IR) in a cross-sectional sample of 98 middle-aged premenopausal women with a wide range of obesity. In addition, we studied the relationship between adiponectin, body composition, and blood biochemical and cardiorespiratory fitness variables. Body composition and fat distribution were measured via dual-energy x-ray absorptiometry in normal-weight (NW) (n = 41, body mass index [BMI] < 25 kg/m(2)) and overweight (OW) (n = 57, BMI > or = 25 kg/m(2)) women. Fasting blood samples were obtained; adiponectin, leptin, insulin, glucose, and insulin-like growth factor-I were measured; and IR index was calculated. The IR index from fasting plasma insulin and plasma glucose levels was estimated using the homeostasis model assessment (HOMA), as follows: fasting plasma insulin (in microliter units per milliliter) x fasting plasma glucose (in millimoles per liter)/22.5. Adiponectin was significantly higher (P = .0001) in NW (14.7 +/- 4.7 microg/mL) compared with OW (9.9 +/- 3.1 microg/mL) women. Significant differences (P < .003) in body mass, BMI, percentage of fat mass, fat mass, trunk fat, trunk fat-leg fat ratio, leptin, insulin, and HOMA were also observed between NW and OW groups. Leptin was independently related to plasma adiponectin (beta = -.259, P = .001) in the overall study group. Plasma adiponectin was only related to trunk fat-leg fat ratio (beta = -.242, P = .002) among NW subjects, whereas plasma adiponectin was related to fat-free mass (beta = .182, P = .0001) and HOMA (beta = -.576, P = .002) among OW women. The inverse relationship between adiponectin and leptin concentrations suggests that leptin may be involved in the regulation of adiponectin in middle-aged premenopausal women. Our data also demonstrate that adiponectin may play an important role in sustaining insulin sensitivity only in OW middle-aged premenopausal women.

Plasma Visfatin and Ghrelin Response to Prolonged Sculling in Competitive Male Rowers

PURPOSE The aim of this investigation was to measure plasma visfatin and ghrelin responses to a single endurance rowing training session in male competitive single scull rowers. METHODS Nine national level male rowers (20.1 +/- 1.5 yr; 183.9 +/- 4.3 cm; 81.0 +/- 5.0 kg; 10.8 +/- 3.3% body fat) completed two trials (exercise or control) on separate days. The exercise consisted of a prolonged rowing training session lasting approximately 2 h (distance = 20.7 +/- 1.4 km; HR = 133 +/- 4 bpm; intensity = 80.2 +/- 1.6% of the HR turn point) followed by a 30-min rest. Venous blood samples were collected before and after on-water rowing. The control trial consisted of rest and blood collection similar to exercise trial. RESULTS No differences were found at baseline values for plasma visfatin, ghrelin, and leptin for both trials. The estimated energy expenditure of the exercise trial was 1200-1500 kcal. Plasma visfatin (-10.0%; P < 0.05) and leptin (-20.0%; P < 0.05) were reduced, and ghrelin concentration was increased (+12.2%; P < 0.05) after a 30-min postexercise. No differences in plasma visfatin, ghrelin, or leptin over time were observed during control trial. There was no relationship between basal visfatin and body composition, energy balance, aerobic power, or blood biochemical data. Plasma visfatin (r = -0.76) and ghrelin (r = 0.75) measured immediately after the training session were related (P < 0.05) to the distance covered, and no relation was observed for postexercise leptin (r = -0.16; P > 0.05). CONCLUSION Acute negative energy balance induced by a single endurance rowing training session elicited an inverse metabolic response in visfatin and ghrelin in competitive male rowers. Our results suggest that peripheral markers of negative energy balance, such as visfatin and ghrelin, may be regarded as signals for metabolic reaction to the energy cost of acute exercise. The results of our study also suggest that an energy-deficit threshold must be met for the response to occur.

Relationship of blood pressure, behavioral mood state, and physical activity following caffeine ingestion in younger and older women

The purpose of this study was to examine the age-related differences in blood pressure, heart rate, and behavioral mood state after caffeine ingestion in younger and older women. Using a placebo-controlled, double-blind design, 10 younger (Y; 18-22 years) and 10 older (O; 50-67 years) healthy women who were moderate consumers of caffeine (self-reported mean intake: Y, 139 +/- 152 mg.day-1; O, 204 +/- 101 mg.day-1) were investigated. All volunteers were characterized for fasting plasma glucose, insulin, free-fatty acids and caffeine levels, body composition, cardiovascular fitness, physical activity, and energy intake. Before and after placebo and caffeine ingestion (5 mg.kg-1 fat-free mass; approximately 208-270 mg) test days, the following variables were measured in all subjects: plasma caffeine levels, heart rate, blood pressure, and behavioral mood state. Results showed that, following caffeine ingestion: (i) both systolic and diastolic blood pressure (SBP and DBP, respectively) increased significantly (p < 0.05) in the older women (SBP, 128.4 +/- 14.2 vs. 132.1 +/- 13.0 mm Hg (3%); DBP, 80.2 +/- 6.9 vs. 83.4 +/- 7.5 mm Hg (4%), whereas only DBP increased in the younger women (67.1 +/- 4.7 vs. 69.9 +/- 5.4 mm Hg (4.2%); p < 0.05); (ii) heart rate decreased significantly (Y, 59.2 +/- 8.7 to 53.9 +/- 10.6 beats.min-1 (p < 0.05); O, 61.9 +/- 9.2 to 59.2 +/- 8.4 beats.min-1 (p < 0.05)) in both groups; and (iii) self-reported feelings of tension and vigor increased and feelings of fatigue decreased (p < 0.05) in younger women, whereas depression decreased (p < or = 0.05) in older women. Self-reported level of physical activity was inversely related to change in DBP following caffeine ingestion in younger women. In conclusion, blood pressure response is augmented and subjective feelings of behavioral mood state are attenuated to a greater degree in older than in younger women following acute caffeine ingestion. Less physically active younger women are more vulnerable to the pressor response to caffeine than more active younger women. It should be noted that these findings are limited to moderate consumers of caffeine who abstained for 48 h prior to testing, and who ingested caffeine in pill form (approximately 240 mg).

An acute bout of endurance exercise but not sprint interval exercise enhances insulin sensitivity

An acute bout of endurance exercise (EE) enhances insulin sensitivity, but the effects of sprint interval exercise (SIE) have not yet been described. We sought to compare insulin sensitivity at baseline and after an acute bout of EE and SIE in healthy men (n = 8) and women (n = 5) (age, 20.7 +/- 0.3 years; peak oxygen consumption (VO2 peak), 42.6 +/- 1.7 mL.kg(-1).min(-1); <1.5 days.week(-1) structured exercise; body fat, 21.1 +/- 1.9%). Subjects underwent 3 oral glucose tolerance tests (OGTT(s)) the day after each of the following 3 conditions: no exercise, baseline (OGTT(B)); SIE at approximately 125% VO(2 peak) (OGTT(SIE)); and EE at approximately 75% VO(2 peak )(OGTT(EE)). SIE and EE sessions were randomized for each subject. Subjects consumed identical meals the day preceding each OGTT. Two insulin sensitivity indices - composite whole-body insulin sensitivity index (ISI-COMP) and ISI-hepatic insulin sensitivity (HOMA) - were calculated, using previously validated formulas (ISI-COMP = 10 000/ radical(glucose(fasting)) x insulin(fasting) x glucose(mean OGTT) x insulin(mean OGTT)); ISI-HOMA = 22.5/(insulin(fasting) x glucose(fasting)), and the plasma concentrations of cytokines interleukin-6 and tumor necrosis factor-alpha were measured. There were no differences by sex for any condition (men vs. women, p > 0.05). Pearsons correlation coefficients between ISI-COMP and ISI-HOMA for each condition were highly correlated (p < 0.01), and followed similar patterns of response. ISI-COMP(EE) was 71.4% higher than ISI-COMP(B) (8.4 +/- 1.4 vs. 4.9 +/- 1.0; p < 0.01) and 40.0% higher than ISI-COMPSIE (8.4 +/- 1.4 vs. 6.0 +/- 1.5; p < 0.05), but there was no difference between ISI-COMP(B) and ISI-COMP(SIE) (p = 0.182). VO(2 peak) was highly correlated with both ISI-COMP and ISI-HOMA during baseline and SIE test conditions (p < 0.02). These findings demonstrate that an acute bout of EE, but not SIE, increases insulin sensitivity relative to a no-exercise control condition in healthy males and females. While these findings underscore the use of regular EE as an effective intervention strategy against insulin resistance, additional research examining repeated sessions of SIE on insulin sensitivity is warranted.

Sports drinks, exercise training, and competition.

A plethora of investigations examining fluid intake before, during, and after training and competition have suggested that a lack of adequate fluid intake will impair or decrease physical performance. Depending upon the type of training or competition, individuals training for prolonged endurance events should drink fluids containing carbohydrates and electrolytes during and after training or competition. Inadequate hydration will cause significant decrements in performance, increase thermal stress, reduce plasma volume, accelerate fatigue, and possibly cause injuries associated with fluid and sweat loss. However, overdrinking may cause Na+ depletion and in some cases lead to hyponatremia. Maintaining proper hydration before, during, and after training and competition will help reduce fluid loss, maintain performance, lower submaximal exercise heart rate, maintain plasma volume, and reduce heat stress, heat exhaustion, and possibly heat stroke.