Creatine monohydrate supplementation on body weight and percent body fat

Seventeen active males (age 22.9 +/- 4.9 year) participated in a study to examine the effects of creatine monohydrate supplementation on total body weight (TBW), percent body fat, body water content, and caloric intake. The TBW was measured in kilograms, percent body fat by hydrostatic weighing, body water content via bioelectrical impedance, and caloric intake by daily food log. Subjects were paired and assigned to a creatine or placebo group with a double-blind research design. Supplementation was given for 4 weeks (30 g a day for the initial 2 weeks and 15 g a day for the final 2 weeks). Subjects reported 2 days a week for supervised strength training of the lower extremity. Significant increases before and after the study were found in TBW (90.42 +/- 14.74 to 92.12 +/- 15.19 kg) and body water content (53.77 +/- 1.75 to 57.15 +/- 2.01 L) for the creatine group (p = 0.05). No significant changes were found in percent body fat or daily caloric intake in the creatine group. No significant changes were noted for the placebo group. These findings support previous research that creatine supplementation increases TBW. Mean percent body fat and caloric intake was not affected by creatine supplementation. Therefore weight gain in lieu of creatine supplementation may in part be due to water retention.     

Age and body mass index associations with body segment parameters

Body segment parameters (BSPs) such as segment mass, center of mass, and radius of gyration are required in many ergonomic tools and biomechanical models to estimate injury risk, and quantify muscle and joint contact forces. Currently, the full effects of age and obesity have not been taken into account when predicting BSPs. The goal of this study is to quantify the impact of body mass index (BMI) and age on BSPs, in order to provide more representative measures necessary for modeling inputs. A whole body dual energy X-ray absorptiometry (DXA) scan was collected for 280 working men and women with a wide range of BMI and aged 21 to 70 years. Established DXA processing methods were used to determine in-vivo estimates of the mass, center of mass, and radius of gyration for the upper arm, forearm, torso, thigh, and shank for males and females. Regression models were used to determine if age and BMI terms, as well as their interactions, were associated with these BSPs. The variability in BSPs explained by BMI alone ranged from 4 to 51%, and age explained an additional 3–19%. Thus, BMI and age are significant correlates of BSPs, and need to be taken into account when predicting certain BSPs in order to obtain accurate and representative results in biomechanical models.     

Scaling of body frontal area and body width in birds

By analyzing a homogenous dataset we show, in contradiction to a previous study, that the scaling of body frontal area (S(b)) with body mass (m(b)) does not differ between passerine and nonpasserine birds. It is likely that comparison of data collected from live passerines with data collected from frozen nonpasserines had led to the incorrect conclusion that the scaling of S(b) varied between the taxa. We suggest that body dimensions collected from frozen specimens, or specimens stored in alcohol, are not applicable to live birds, and that both the current equations presented in the literature for predicting S(b) from m(b) may lead to inaccurate estimates. Using data from preserved specimens, we found that S(b) scales isometrically with m(b) (S(b) proportional, variant m(b) (0.66)), and therefore we found no evidence for larger birds being more streamlined than smaller birds. S(b) scales with negative allometry against wingspan (b), however, and b scales with positive allometry against m(b), so larger birds have smaller S(b) relative to b. In addition, it appears that dorsoventral flattening of the body is a general characteristic of bird's bodies but that it is more pronounced in larger birds, suggesting perhaps a function in terms of increased lift during forward flight. It appears that bird's bodies obey the surface-to-area geometric scaling law, but bird body shape may vary in relation to aerodynamic function. We suggest that a large-scale study, simultaneously measuring S(b) and m(b) in live passerines and nonpasserines, is required to improve the predictive power of S(b) upon m(b) scaling equations, which play a key role in the estimation of mechanical power consumption in flight in birds. Furthermore, the relations between bird body shape and axial skeleton dimensions, with reference to aerodynamic adaptation, warrant further investigation.     

The neural basis of body form and body action agnosia

Visual analysis of faces and nonfacial body stimuli brings about neural activity in different cortical areas. Moreover, processing body form and body action relies on distinct neural substrates. Although brain lesion studies show specific face processing deficits, neuropsychological evidence for defective recognition of nonfacial body parts is lacking. By combining psychophysics studies with lesion-mapping techniques, we found that lesions of ventromedial, occipitotemporal areas induce face and body recognition deficits while lesions involving extrastriate body area seem causatively associated with impaired recognition of body but not of face and object stimuli. We also found that body form and body action recognition deficits can be double dissociated and are causatively associated with lesions to extrastriate body area and ventral premotor cortex, respectively. Our study reports two category-specific visual deficits, called body form and body action agnosia, and highlights their neural underpinnings.     

Cooling different body surfaces during upper and lower body exercise

The effect of varying the body surface area being cooled by a liquid microclimate system was evaluated during exercise heat-stress conditions. Six male subjects performed a total of six exercise (O2 uptake = 1.2 l/min) tests in a hot environment (ambient temperature = 38 degrees C, relative humidity = 30%) while dressed in clothing having low moisture permeability and high insulation. Each subject completed two upper body exercise (U; arm crank) tests: 1) with only the torso surface (T) cooled; and 2) with the surfaces of both the torso and upper arms (TA) cooled [coolant temperature at the inlet (Ti) was 20 degrees C for all upper body tests]. Each subject also completed four lower body exercise (L; walking) tests: 1) with only the T cooled (Ti = 20 degrees C); 2) with only the T cooled (Ti = 26 degrees C); 3) with torso, upper arm, and thigh surface (TAT) cooled (Ti = 20 degrees C); and 4) with TAT cooled (Ti = 26 degrees C). During U exercise, TA cooling had no effects compared with cooling only T. During L exercise, sweat rates, heart rates, and rectal temperature (Tre) changes were less with TAT cooling compared with cooling only the T. Altering Ti had no effect on Tre changes, but higher heart rates were observed with 26 than with 20 degrees C. These data indicate that cooling arms during upper body exercise provides no thermoregulatory advantage, although cooling the thigh surfaces during lower body exercise does provide an advantage.     

Effect of body fat and gender on body temperature distribution

It is well known that body composition can influence peripheral heat loss and skin temperature. That the distribution of body fat is affected by gender is well known; however, there is little information on how body composition and gender influences the measure of skin temperature. This study evaluated skin temperature distribution according to body fat percentage (BF%) and gender. A sample of 94 apparently healthy volunteers (47 women and 47 men) was assessed with Dual-Energy X-Ray Absorptiometry (DXA) and infrared thermography (mean, maximum and minimum temperatures – T_Mean, T_Max and T_Min). The sample was divided into groups, according to health risk classification, based on BF%, as proposed by the American College of Sports Medicine: Average (n = 58), Elevated (n = 16) or High (n = 20). Women had lower T_Mean in most regions of interest (ROI). In both genders, group High had lower temperature values than Average and Elevated in the trunk, upper and lower limbs. In men, palms and posterior hands had a tendency (p < 0.05) for increased temperature along with increased BF%. T_Mean, T_Max and T_Min of trunk, upper and lower limbs were negatively correlated with BF% and the fat percentage of each segment (upper limbs, lower limbs and trunk). The highest correlations found in women were between posterior trunk and BF% (rho = −0.564, p < 0.001) and, in men, between anterior trunk and BF% (rho = −0.760, p < 0.001). Overall, this study found that women have lower skin temperature than men, which was related with higher BF%. Facial temperature seems not to be influenced by body fat. With the future collection of data on the relationship between BF% and skin temperature while taking into account factors such as body morphology, gender, and ethnicity, we conclude that measurement of BF may be reliably estimated with the use of thermal imaging technology.     

Social stress and recovery: implications for body weight and body composition

Social stress resulting from dominant-subordinate relationships is associated with body weight loss and altered body composition in subordinate (SUB) male rats. Here, we extend these findings to determine whether stress-induced changes in energy homeostasis persist when the social stress is removed, and the animal is allowed to recover. We examined body weight (BW), body composition, and relevant endocrine measures after one or two cycles of 14 days of social stress, each followed by 21 days of recovery in each rat's individual home cage. SUB lost significantly more BW during social housing in a visible burrow system (VBS) compared with dominant (DOM) animals. Weight loss during social stress was attributable to a decrease in adipose tissue in DOM and SUB, with an additional loss of lean tissue in SUB. During both 21-day recovery periods, DOM and SUB regained lost BW, but only SUB were hyperphagic. Following recovery, SUB had a relatively larger increase in adipose tissue and plasma leptin compared with DOM, indicating that body composition changes were dependent on social status. Control animals that were weight matched to SUB or male rats exposed to the VBS environment without females, and that did not form a social hierarchy, did not exhibit changes in body composition like SUB in the VBS. Therefore, chronic social stress causes social status-dependent changes in BW, composition and endocrine measures that persist after repeated stress and recovery cycles and that may ultimately lead to metabolic disorders and obesity.     

Exercise and body composition

We assessed changes in body composition in 41 young adults who engaged in various exercise and/or training programs on ad libitum diets. Most of those who gained weight sustained an increase in lean body mass (LBM), and most of those who lost weight lost LBM as well as fat. The change in LBM was directly related to the change in weight, with a regression slope of 0.500. An analysis of published data confirms these findings and, in concert with our data, provides the additional information that the magnitude of the change in body composition in exercising individuals is influenced by body fat content, just as it is for nonexercising individuals.     

Competition and body size

If being larger than competing conspecifics is important for fitness, then an unstable escalation of body size may result. In asexual populations, a cycling of sizes can occur but for sexual diploids, an irreversible size increase is more likely. Several factors can produce a stable distribution of sizes, but a single body size or even a narrow range of sizes cannot be stable. For example, enough environmental variance can produce stability without any genetic variability in the population. Or, with no environmental variance, a high cost of fighting between similar sizes or, for diploids, an increasing mortality with size may lead to a stable distribution of sizes. A game theory model is used to investigate the existence and form of a stable distribution of body sizes in a population.