During childhood, varying exercise modalities are recommended to stimulate normal growth, development, and health. This project investigated hormonal and metabolic responses triggered by a resistance exercise protocol in lean children (age: 9.3 ± 1.4 y, body fat: 18.3 ± 4.9%), obese children (age: 9.6 ± 1.3 y, body fat: 40.3 ± 5.2%) and lean adults (age: 23.3 ± 2.4 y, body fat: 12.7 ± 2.9%). The protocol consisted of stepping onto a raised platform (height = 20% of stature) while wearing a weighted vest (resistance = 50% of lean body mass). Participants completed 6 sets of 10 repetitions per leg with a 1-min rest period between sets. Blood samples were obtained at rest preexercise, immediately postexercise and 2 times throughout the 1-hr recovery to analyze possible changes in hormones and metabolites. Children-adult differences included a larger exercise-induced norepinephrine increase in adults vs. children and a decrease in glucagon in children but not adults. Similarities between adults and children were observed for GH-IGF-1 axis responses. Metabolically, children presented with lower glycolytic and increased fat metabolism after exercise than adults did. Obesity in childhood negatively influenced GH, insulin, and glucose concentrations. While adults occasionally differed from children, amount of activated lean mass, not maturation, likely drove these dissimilarities.
Daniela A. Rubin, Diobel M. Castner, Hoang Pham, Jason Ng, Eric Adams and Daniel A. Judelson
Eduardo Federighi Baisi Chagas, Mariana Rotta Bonfim, Bruna Camilo Turi, Nair Cristina Margarida Brondino and Henrique Luiz Monteiro
Declines in ovarian function in postmenopausal women may contribute to increase inflammatory cytokines, which can lead to chronic diseases. However, studies have shown that exercise interventions are important to manage inflammatory conditions. Thus, the objective of this study was to analyze the effect of exercise intervention on inflammatory markers among obese and postmenopausal women.
70 women composed the sample (Exercise group [EG; n = 35] and nonexercise group [nEG; n = 35]). IL-6, TNF-α, and IL-10 were the inflammatory markers analyzed. Exercise program was 20 weeks long and consisted of aerobic and neuromuscular training. Data about chronic diseases, medication use, dietary intake, body composition and biochemical variables were collected.
EG showed significant reductions in body mass index, waist circumference and body fat percentage, as well as increased lean body mass. EG showed significant reductions in TNF-α and significant interaction between group and intervention time. Reductions in IL-10 were identified only in nEG. Substantial effect of exercise intervention was observed with increased ratio of IL-10/IL-6 and IL-10/TNF-α.
Combination of aerobic exercise and resistance training was effective in reducing inflammation. Thus, implementation and maintenance of similar exercise programs can contribute to reduce chronic inflammation among obese postmenopausal women.
Dan M. Cooper, Szu-Yun Leu, Candice Taylor-Lucas, Kim Lu, Pietro Galassetti and Shlomit Radom-Aizik
Consensus has yet to be achieved on whether obesity is inexorably tied to poor fitness. We tested the hypothesis that appropriate reference of cardiopulmonary exercise testing (CPET) variables to lean body mass (LBM) would eliminate differences in fitness between high-BMI (≥ 95th percentile, n = 72, 50% female) and normal-BMI (< 85th percentile, n = 142, 49% female), otherwise-healthy children and adolescents typically seen when referencing body weight. We measured body composition with dual x-ray absorptiometry (DXA) and CPET variables from cycle ergometry using both peak values and submaximal exercise slopes (peak VO2, ΔVO2/ΔHR, ΔWR/ΔHR, ΔVO2/ΔWR, and ΔVE/ΔVCO2). In contrast to our hypothesis, referencing to LBM tended to lessen, but did not eliminate, the differences (peak VO2 [p < .004] and ΔVO2/ΔHR [p < .02]) in males and females; ΔWR/ΔHR differed between the two groups in females (p = .041) but not males (p = .1). The mean percent predicted values for all CPET variables were below 100% in the high-BMI group. The pattern of CPET abnormalities suggested a pervasive impairment of O2 delivery in the high-BMI group (ΔVO2/ΔWR was in fact highest in normal-BMI males). Tailoring lifestyle interventions to the specific fitness capabilities of each child (personalized exercise medicine) may be one of the ways to stem what has been an intractable epidemic.
Scott C. Forbes, Nathan Sletten, Cody Durrer, Étienne Myette-Côté, D. Candow and Jonathan P. Little
High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness, performance, body composition, and insulin sensitivity. Creatine (Cr) supplementation may augment responses to HIIT, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of 4 weeks of HIIT (three sessions/week) combined with Cr supplementation in recreationally active females. Seventeen females (age = 23 ± 4 yrs; BMI = 23.4 ± 2.4) were randomly assigned to either Cr (Cr; 0.3 g・kg-1・d-1 for 5 d followed by 0.1 g・kg-1・d-1 for 23 days; n = 9) or placebo (PLA; n = 8). Before and after the intervention, VO2peak, ventilatory threshold (VT), time-trial performance, lean body mass and fat mass, and insulin sensitivity were assessed. HIIT improved VO2peak (Cr = +10.2%; PLA = +8.8%), VT (Cr = +12.7%; PLA = +9.9%), and time-trial performance (Cr = -11.5%; PLA = -11.6%) with no differences between groups (time main effects, all p < .001). There were no changes over time for fat mass (Cr = -0.3%; PLA = +4.3%), whole-body lean mass (Cr = +0.5%; PLA = -0.9%), or insulin resistance (Cr = +3.9%; PLA = +18.7%). In conclusion, HIIT is an effective way to improve cardiorespiratory fitness, VT, and time-trial performance. The addition of Cr to HIIT did not augment improvements in cardiorespiratory fitness, performance or body composition in recreationally active females.
Stephan P. Clancy, Priscilla M. Clarkson, Michael E. DeCheke, Kazunori Nosaka, Patty S. Freedson, John J. Cunningham and Bruce Valentine
The effects of 9 weeks of daily chromium supplementation (200μg Cr as picolinate) were investigated in a double-blind design in football players during spring training. Testing was done pre-, mid-, and postsupplementation on the following criterion measures: urinary chromium excretion, girth and skinfold measures, percent body fat and lean body mass, and isometric and dynamic strength. With the exception of 2 variables (of 65 variables analyzed), no significant group by trials interactions were found (based on a repeated measures ANOVA). The two exceptions were unrelated and inconsequential. For 27 of the 38 subjects, average urinary chromium loss at pre was 0.36 μg/24 hr, whereas it was undetectable (< 0.1 μg/24 hr) for 10 subjects and excessive in 1 subject (2.4 μg/24 hr). Subjects receiving chromium supplements demonstrated urinary chromium losses five times greater than those in the placebo group at mid and post. Chromium picolinate supplementation was ineffective in bringing about changes in body composition or strength during a program of intensive weight-lifting training.
Colin Wilborn, Lem Taylor, Chris Poole, Cliffa Foster, Darryn Willoughby and Richard Kreider
The purpose of this study was to determine the effects of an alleged aromatase and 5-α reductase inhibitor (AI) on strength, body composition, and hormonal profiles in resistance-trained men. Thirty resistance-trained men were randomly assigned in a double-blind manner to ingest 500 mg of either a placebo (PL) or AI once per day for 8 wk. Participants participated in a 4-d/wk resistance-training program for 8 wk. At Weeks 0, 4, and 8, body composition, 1-repetition-maximum (1RM) bench press and leg press, muscle endurance, anaerobic power, and hormonal profiles were assessed. Statistical analyses used a 2-way ANOVA with repeated measures for all criterion variables (p ≤ .05). Significant Group × Time interaction effects occurred over the 8-wk period for percent body fat (AI: –1.77% ± 1.52%, PL: –0.55% ± 1.72%; p = .048), total testosterone (AI: 0.97 ± 2.67 ng/ml, PL: –2.10 ± 3.75 ng/ml; p = .018), and bioavailable testosterone (AI: 1.32 ± 3.45 ng/ml, PL: –1.69 ± 3.94 ng/ml; p = .049). Significant main effects for time (p ≤ .05) were noted for bench- and leg-press 1RM, lean body mass, and estradiol. No significant changes were detected among groups for Wingate peak or mean power, total body weight, dihydrotestosterone, hemodynamic variables, or clinical safety data (p > .05). The authors concluded that 500 mg of daily AI supplementation significantly affected percent body fat, total testosterone, and bioavailable testosterone compared with a placebo in a double-blind fashion.
Jerry L. Mayhew, Michael G. Bemben and Donna M. Rohrs
The purpose of this study was to determine the relationships among the seated shot put (SSP), bench press power (BPP), and body composition in adolescent wrestlers. Seventy-five wrestlers from three high schools were tested during their preseason training. Upper body power was tested with a plate-loaded bench press machine equipped with infrared sensors attached to a digital timer. Each subject was given three trials with a constant 24.5-kg load (CLP) and with a variable load equal to 60% of body mass (VLP). Skinfolds were used to estimate body composition. The SSP was significantly related to both CLP and VLP as well as to body mass, lean body mass (LBM), and % fat. Removing the effect of body mass reduced the relationship between SSP and both CLP and VLP. Removing the effect of LBM had a slightly greater effect on the relationships between SSP and both CLP and VLP, although the correlations remained significant. Therefore it appears that the SSP is only moderately related to upper body power in adolescent wrestlers and may be greatly influenced by size and muscularity.
Michael H. Stone, Kimberly Sanborn, Lucille L. Smith, Harold S. O'Bryant, Tommy Hoke, Alan C. Utter, Robert L. Johnson, Rhonda Boros, Joseph Hruby, Kyle C. Pierce, Margaret E. Stone and Brindley Garner
The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohy-drate, Group P (n = 11) received calcium pyruvate. Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (Tl) and after (T2) the 5-week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL. CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.
Jay Hoffman, Nicholas Ratamess, Jie Kang, Gerald Mangine, Avery Faigenbaum and Jeffrey Stout
The effects of creatine and creatine plus β-alanine on strength, power, body composition, and endocrine changes were examined during a 10-wk resistance training program in collegiate football players. Thirty-three male subjects were randomly assigned to either a placebo (P), creatine (C), or creatine plus β-alanine (CA) group. During each testing session subjects were assessed for strength (maximum bench press and squat), power (Wingate anaerobic power test, 20-jump test), and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, IGF-1, and sex hormone binding globulin. Changes in lean body mass and percent body fat were greater (P < 0.05) in CA compared to C or P. Significantly greater strength improvements were seen in CA and C compared to P. Resting testosterone concentrations were elevated in C, however, no other significant endocrine changes were noted. Results of this study demonstrate the efficacy of creatine and creatine plus β-alanine on strength performance. Creatine plus β-alanine supplementation appeared to have the greatest effect on lean tissue accruement and body fat composition.
Tai T. Tran, Lina Lundgren, Josh Secomb, Oliver R.L. Farley, G. Gregory Haff, Laurent B. Seitz, Robert U. Newton, Sophia Nimphius and Jeremy M. Sheppard
To determine whether a previously validated performance-testing protocol for competitive surfers is able to differentiate between Australian elite junior surfers selected (S) to the national team and those not selected (NS).
Thirty-two elite male competitive junior surfers were divided into 2 groups (S = 16, NS = 16). Their age, height, body mass, sum of 7 skinfolds, and lean-body-mass ratio (mean ± SD) were 16.17 ± 1.26 y, 173.40 ± 5.30 cm, 62.35 ± 7.40 kg, 41.74 ± 10.82 mm, 1.54 ± 0.35 for the S athletes and 16.13 ± 1.02 y, 170.56 ± 6.6 cm, 61.46 ± 10.10 kg, 49.25 ± 13.04 mm, 1.31 ± 0.30 for the NS athletes. Power (countermovement jump [CMJ]), strength (isometric midthigh pull), 15-m sprint paddling, and 400-m endurance paddling were measured.
There were significant (P ≤ .05) differences between the S and NS athletes for relative vertical-jump peak force (P = .01, d = 0.9); CMJ height (P = .01, d = 0.9); time to 5-, 10-, and 15-m sprint paddle; sprint paddle peak velocity (P = .03, d = 0.8; PV); time to 400 m (P = .04, d = 0.7); and endurance paddling velocity (P = .05, d = 0.7).
All performance variables, particularly CMJ height; time to 5-, 10-, and 15-m sprint paddle; sprint paddle PV; time to 400 m; and endurance paddling velocity, can effectively discriminate between S and NS competitive surfers, and this may be important for athlete profiling and training-program design.