Formula and scale for body surface area estimation in high-risk infants

Advances in medical technology and the health sciences have lead to a rapid increase in the prevalence and morbidity of high-risk infants with chronic or permanent sequels such as the birth of early preterm infants. A suitable formula is therefore needed for body surface area (BSA) estimation for high-risk infants to more accurately devise therapeutic regimes in clinical practice. A cohort study involving 5014 high-risk infants was conducted to develop a suitable formula for estimating BSA using four of the existing formulas in the literature. BSA of high-risk infants was calculated using the four BSA equations (Boyd-BSA, Dubois-BSA, Meban-BSA, Mosteller-BSA), from which a new calculation, Mean-BSA, was arithmetically derived as a reference BSA measure. Multiple-regression was performed using nonlinear least squares curve fitting corresponding to the trend line and the new equation, Neo-BSA, developed using Excel and SPSS 17.0. The Neo-BSA equation was constructed as follows: Neo-BSA = 5.520 x W(0.5526) x L(0.300). With the assumption of the least square root relation between weight and length, a BSA scale using only weight was fabricated specifically for clinical applications where weight is more available in high-risk infant populations than is length. The validity of Neo-BSA was evaluated against Meban-BSA, the best of the four equations for high-risk infants, as there is a similarity of subjects in the two studies. The other formulas revealed substantial variances in BSA compared to Neo-BSA. This study developed a new surface area equation, Neo-BSA, as the most suitable formula for BSA measurement of high-risk infants in modern-day societies, where an emerging population of newborns with shorten gestational ages are becoming more prevalent as a result of new advances in the health sciences and new development of reproductive technologies. In particular, a scale for 400-7000 g body weight babies derived from the Neo-BSA equation has the clinical advantage of using only weight as a measurement, since length is often not feasible as a measurement due to the newborn's body posture. Further studies are required to confirm our findings for the application of Neo-BSA and the BSA scale (based on weight) for various populations and ethnicities under different clinical conditions.     

Body surface area prediction in normal-weight and obese patients

None of the equations frequently used to predict body surface area (BSA) has been validated for obese patients. We applied the principles of body size scaling to derive an improved equation predicting BSA solely from a patient's weight. Forty-five patients weighing from 51.3 to 248.6 kg had their height and weight measured on a calibrated scale and their BSA calculated by a geometric method. Data were combined with a large series of published BSA estimates. BSA prediction with the commonly used Du Bois equation underestimated BSA in obese patients by as much as 20%. The equation we derived to relate BSA to body weight was a power function: BSA (m(2)) = 0.1173 x Wt (kg)(0.6466). Below 10 kg, this equation deviated significantly from the BSA vs. body weight curve, necessitating a different set of coefficients: BSA (m(2)) = 0.1037 x Wt (kg)(0.6724). Covariance of height and weight for patients weighing <80 kg reduced the Du Bois BSA-predicting equation to a power function, explaining why it provides good BSA predictions for normal-size patients but fails with obesity.     

Scaling the physiological effects of exposure to radiofrequency electromagnetic radiation: consequences of body size

We have demonstrated that a comparative analysis of the physiological effects of exposure of laboratory mammals to radiofrequency electromagnetic radiation (RFR) may be useful in predicting exposure thresholds for humans if the effect is assumed to be due only to heating of tissue. The threshold specific absorption rate (SAR) necessary to affect a thermoregulatory parameter shows an inverse and linear relationship to body mass. The inverse relationship between threshold SAR and body mass is attributed to a surface area: body mass relationship. In comparison to small mammals, relatively large mammals have a reduced capacity to dissipate an internal heat load passively, and are therefore physiologically more sensitive to RFR exposure. The threshold for a thermoregulatory response depends on the type of response measured, species, ambient temperature, etc. By extrapolation, it can be shown that a SAR of only 0.2-0.4 W/kg is required to promote a thermoregulatory response in a mammal with a body mass of 70 kg (e.g. weight of adult human). The specific absorption rate bioeffects data collected from laboratory mammals can be related by means of a simple power formula: threshold SAR (W/kg) = aMb, where M is body mass in kg, a is a constant and b is equal to approximately -0.5. Through this equation we have illustrated that a threshold SAR measured in a species weighing 100 g would be 10 times greater than that of a species weighing 10 000 g. Accordingly, a relatively low SAR that is physiologically ineffective in small mammals may be stressful to larger species.     

Respiratory gill surface of the serrasalmid fish, Piaractus mesopotamicus

Gill element dimensions of pacu Piaractus mesopotamicus were estimated and correlated to body mass ( W ), according to the power equation Y=aW^b . The filament number ( b =0.154) and length ( b =0.457) increased with body mass, markedly influencing the respiratory gill surface area ( b =0.769). The high filament number and length, associated with a high secondary lamellae frequency ( a =40.21), are typical of active fish species and may be an adaptation to its migratory movements during reproduction. The comparatively small dimensions of its secondary lamellae are found more commonly in less active species, and may be related to the environmental conditions prevailing in lentic environments, where the species is normally found most of the year. Such features, together with its ability to compensate for oxygen reduction by means of a high ventilatory volume, and the use of aquatic surface respiration (ASR), may account for its adaptative capacity to withstand hypoxic conditions, with a low respiratory energy cost.     

The regularities in connection between fecundity with body weight and growth rate in fishes

The absolute and relative fecundity of freshwater, anadromous and marine fishes (102 species and subspecies from 33 families) and its dependence on body mass and growth rate were analyzed on the basis of published data. According to the spawning type all studied fishes were divided into species with short-term and single spawning and fishes with extended or long-term spawning. The equations of dependence of absolute fecundity (E) on body mass (W) were calculated: E = 1.033 W0.578 (the first group) and E = 0.792 W0.74 (the second group). If W < 177 g the equations don't differ significantly and one may use the equation E = 1.34(-0.742) for both groups. The body mass of females at age of maturity expressed as a portion of maximal definitive body mass equals 0.22 +/- 0.044 for many different species with 0.95 probability. The relative fecundity (a1) of some species negatively correlates with maximal body mass of adult individuals (Wmax). This dependence is expressed by equations: a1 = 3.033 Wmax-0.549 (for the first group) and a1 = 1.726 Wmax-0.351 (for the second group). Value of ratio Wov/W of different fish species changes irregularly from 0.054 to 0.32 and its average is 0.150 +/- 0.012 for the first group and 0.156 +/- 0.007 for the second one. In such a way, single reproduction effort of fishes is approximately 0.15. Comparison of data on Pisces, Crustacea, Amphibia, Reptilia, and Mammalia revealed that reproduction effort of different aquatic and terrestrial invertebrates and vertebrates varies within rather narrow limits (from 0.05 to 0.44). Average values of this index varies even less--from 0.097 to 0.238, on average 0.162, i.e. approximately 15-18% of animals' body mass falls on their reproduction constituent.     

Relationship between measures of body size and composition and velocity of lactate threshold

The purpose of this investigation was to explore the relationship between velocity of lactate threshold (vLT) and various measures of body mass and composition: mass, lean mass, fat mass, percent body fat (% fat), and body surface area (BSA). We hypothesized that mass would be inversely related to vLT, and that differences in measures of body mass and composition would account for a significant amount of variability in vLT. A total of 21 healthy male runners served as subjects. Body composition was assessed by hydrostatic weighing. A significant negative relationship (r = -0.759, p < or = 0.01) was between body mass and vLT. The coefficient of determination between vLT and body mass indicated that nearly 58% of the variability in vLT was explained by body mass in these subjects. Significant relationships were also between vLT and BSA (r = -0.72, p < or = 0.01), fat mass (r = -0.70, p < or = 0.01), % fat (r = -0.59, p < or = 0.01), and lean mass (r = -0.41, p < or = 0.05). Linear regression yielded the following model: y = 369.48 - 1.7343 (X), where y = predicted vLT (m.min(-1)) and X = body mass (kilograms) (SEE = 15.45). Velocity of lactate threshold was significantly inversely related with body mass in a group of male runners. The calculated coefficient of determination suggests that nearly 58% of the variability in vLT was explained by body mass. The present data suggest consideration of categorizing participants in 'road runs' by body mass to equate competition, as is done in other sports (e.g., weightlifting).     

关于中国人体表面积公式的研究

以纸模法测量１００名成人（男女各５０名）体表面积,并测量其身高、体重,比较以Ｓｔｅｖｅｎｓｏｎ公式计算之人体表面积与实测体表面积的差异。结果表明,Ｓｔｅｖｅｎｓｏｎ公式已不适用于计算当代中国人体表面积,据男女各５０例所得到的男女体表面积计算公式分别为：Ｓ男＝０００５７×身高＋００１２１×体重＋００８８２,Ｓ女＝０００７３×身高＋００１２７×体重－０２１０６,若不区别男和女,为中国人适用的通式为Ｓ＝０００６１×身高＋００１２４×体重－０００９９。     

Birth Weight,Adult Body Composition,and Subcutaneous Fat Distribution

Objectives: To investigate if birth weight is related to both body mass index (BMI) and distribution of subcutaneous fat at adult age. Research Methods and Procedures: A 9‐year longitudinal study was performed in 229 subjects (192 women) with ages ranging from 27 to 36 years. Birth weight was retrieved by a questionnaire, and adult weight, height, skinfold thicknesses, and waist‐to‐hip ratio (WHR) were repeatedly measured at mean ages 27, 29, 31, and 36 years. BMI, sum of four skinfolds (S4S), the ratio between two truncal skinfolds and S4S (SS/S4S), and the ratio between WHR and the cross‐sectional area of the left thigh were calculated with the available data. Results: The adjusted model showed that in women, birth weight was significantly negatively related to adult S4S [β = ?5.211; (?9.768 to ?0.654)], waist circumference [β = ?1.449; (?2.829 to ?0.069)], and SS/S4S ratio [β = ?3.579; (?5.296 to ?1.862)]. In men, a significant negative association was observed between birth weight and adult WHR [β = ?1.096; (?2.092 to ?0.100)] only. Other relationships showed, although not significantly, the same negative trend, namely that lower birth weight is related to higher adult body fat mass (S4S) and a more truncal subcutaneous fat distribution (SS/S4S). No associations were found between birth weight and either adult BMI or the cross‐sectional area of the thigh. Discussion: Lower birth weight is, in both adult men and women, related to a higher adult subcutaneous fat mass and a more truncal distribution of subcutaneous fat, indicating a higher risk for obesity.     

Determination of hand surface area by sex and body shape using alginate

Hand surface area (HSA) has been utilized for burned skin area estimation in burn therapy, heat exchange in thermal physiology, exposure assessment in occupational toxicology, and the development of manual equipment/ protective gloves in ergonomics. The purpose of this study was to determine the hand surface area to the total body surface area (BSA) and derive a formula for estimating HSA. Thirty-four Korean males (20-60 years old; 158.5-187.5 cm in height; 48.5-103.1 kg in body weight) and thirty-one Korean females (20-63 years old; 140.6-173.1 cm; 36.8-106.1 kg) participated as subjects. The HSA and BSA of 65 subjects were directly measured using alginate. The measurements showed 1) the surface area of the hand had a mean of 448 (371-540) cm(2) for males, and 392 (297-482) cm(2) for females. 2) The hand as a percentage of the total body surface area for males and females was 2.5% and 2.4% respectively, showing no significant difference. 3) The hand as a percentage of BSA by body shape was 2.5% for the lean group and 2.3% for overweight people (p=0.001). 4) When estimating the surface area of a hand, formulae based on hand length or hand circumference were more valid than formulae based on height and body weight. We obtained the following formula for estimating HSA: Estimated HSA(cm(2))=1.219 Hand length(cm) x Hand circumference(cm).     

Body water content over a range of ambient salinities in the sheepshead minnow

Body water content was determined on groups of Cyprinodon variegatus after sequential acclimation to ambient salinities in the range from fresh water to 100%. A multiple linear regression model applied to the data included body mass ( M ) of individuals and acclimation salinity ( S ) as independent variables, and body water content ( W ) as the dependent variable. The model that described the relationship was W (g) = 0·059 + 0·723 M (g)–0001 S (%). Converting values of body water content to percent of wet body mass produced a range of values from 74·5% in fresh water to 72·0% at 100%, only a 2·5% difference in body water content over this wide range of ambient salinities.     

Predicting euarchontan body mass: A comparison of tarsal and dental variables

Objective: Multiple meaningful ecological characterizations of a species revolve around body mass. Because body mass cannot be directly measured in extinct taxa, reliable body mass predictors are needed. Many published body mass prediction equations rely on dental dimensions, but certain skeletal dimensions may have a more direct and consistent relationship with body mass. We seek to evaluate the reliability of prediction equations for inferring euarchontan body mass based on measurements of the articular facet areas of the astragalus and calcaneus. Methods: Surface areas of five astragalar facets (n = 217 specimens) and two calcaneal facets (n = 163) were measured. Separate ordinary least squares and multiple regression equations are presented for different levels of taxonomic inclusivity, and the reliability of each equation is evaluated with the coefficient of determination, standard error of the estimate, mean prediction error, and the prediction sum of squares statistic. We compare prediction errors to published prediction equations that utilize dental and/or tarsal measures. Finally, we examine the effects of taxonomically specific regressions and apply our equations to a diverse set of non‐primates. Results: Our results reveal that predictions based on facet areas are more reliable than most linear dental or tarsal predictors. Multivariate approaches are often better than univariate methods, but require more information (making them less useful for fragmentary fossils). While some taxonomically specific regressions improve predictive ability, this is not true for all primate groups. Conclusions: Among individual facets, the ectal and fibular facets of the astragalus and the calcaneal cuboid facet are the best body mass predictors. Since these facets have primarily concave curvature and scale with positive allometry relative to body mass, it appears that candidate skeletal proxies for body mass can be identified based on their curvature and scaling coefficients. Am J Phys Anthropol 157:472–506, 2015. © 2015 Wiley Periodicals, Inc.     

What does body size mean,from the “plant's eye view”?

Alternative metrics exist for representing variation in plant body size, but the vast majority of previous research for herbaceous plants has focused on dry mass. Dry mass provides a reasonably accurate and easily measured estimate for comparing relative capacity to convert solar energy into stored carbon. However, from a “plant's eye view”, its experience of its local biotic environment of immediate neighbors (especially when crowded) may be more accurately represented by measures of “space occupancy” (S–O) recorded in situ—rather than dry mass measured after storage in a drying oven. This study investigated relationships between dry mass and alternative metrics of S–O body size for resident plants sampled from natural populations of herbaceous species found in Eastern Ontario. Plant height, maximum lateral canopy extent, and estimated canopy area and volume were recorded in situ (in the field)—and both fresh and dry mass were recorded in the laboratory—for 138 species ranging widely in body size and for 20 plants ranging widely in body size within each of 10 focal species. Dry mass and fresh mass were highly correlated (r² > .95) and isometric, suggesting that for some studies, between‐species (or between‐plant) variation in water content may be unimportant and fresh mass can therefore substitute for dry mass. However, several relationships between dry mass and other S–O body size metrics showed allometry—that is, plants with smaller S–O body size had disproportionately less dry mass. In other words, they have higher “body mass density” (BMD) — more dry mass per unit S–O body size. These results have practical importance for experimental design and methodology as well as implications for the interpretation of “reproductive economy”—the capacity to produce offspring at small body sizes—because fecundity and dry mass (produced in the same growing season) typically have a positive, isometric relationship. Accordingly, the allometry between dry mass and S–O body size reported here suggests that plants with smaller S–O body size—because of higher BMD—may produce fewer offspring, but less than proportionately so; in other words, they may produce more offspring per unit of body size space occupancy.     

Large differences in peak oxygen uptake do not independently alter changes in core temperature and sweating during exercise

The independent influence of peak oxygen uptake (Vo(? peak)) on changes in thermoregulatory responses during exercise in a neutral climate has not been previously isolated because of complex interactions between Vo(? peak), metabolic heat production (H(prod)), body mass, and body surface area (BSA). It was hypothesized that Vo(? peak) does not independently alter changes in core temperature and sweating during exercise. Fourteen males, 7 high (HI) Vo(? peak): 60.1 ± 4.5 ml·kg?1·min?1; 7 low (LO) Vo(? peak): 40.3 ± 2.9 ml·kg?1·min?1 matched for body mass (HI: 78.2 ± 6.1 kg; LO: 78.7 ± 7.1 kg) and BSA (HI: 1.97 ± 0.08 m2; LO: 1.94 ± 0.08 m2), cycled for 60-min at 1) a fixed heat production (FHP trial) and 2) a relative exercise intensity of 60% Vo(? peak) (REL trial) at 24.8 ± 0.6°C, 26 ± 10% RH. In the FHP trial, H(prod) was similar between the HI (542 ± 38 W, 7.0 ± 0.6 W/kg or 275 ± 25 W/m2) and LO (535 ± 39 W, 6.9 ± 0.9 W/kg or 277 ± 29 W/m2) groups, while changes in rectal (T(re): HI: 0.87 ± 0.15°C, LO: 0.87 ± 0.18°C, P = 1.00) and aural canal (T(au): HI: 0.70 ± 0.12°C, LO: 0.74 ± 0.21°C, P = 0.65) temperature, whole-body sweat loss (WBSL) (HI: 434 ± 80 ml, LO: 440 ± 41 ml; P = 0.86), and steady-state local sweating (LSR(back)) (P = 0.40) were all similar despite relative exercise intensity being different (HI: 39.7 ± 4.2%, LO: 57.6 ± 8.0% Vo(2 peak); P = 0.001). At 60% Vo(2 peak), H(prod) was greater in the HI (834 ± 77 W, 10.7 ± 1.3 W/kg or 423 ± 44 W/m2) compared with LO (600 ± 90 W, 7.7 ± 1.4 W/kg or 310 ± 50 W/m2) group (all P < 0.001), as were changes in T(re) (HI: 1.43 ± 0.28°C, LO: 0.89 ± 0.19°C; P = 0.001) and T(au) (HI: 1.11 ± 0.21°C, LO: 0.66 ± 0.14°C; P < 0.001), and WBSL between 0 and 15, 15 and 30, 30 and 45, and 45 and 60 min (all P < 0.01), and LSR(back) (P = 0.02). The absolute esophageal temperature (T(es)) onset for sudomotor activity was ～0.3°C lower (P < 0.05) in the HI group, but the change in T(es) from preexercise values before sweating onset was similar between groups. Sudomotor thermosensitivity during exercise were similar in both FHP (P = 0.22) and REL (P = 0.77) trials. In conclusion, changes in core temperature and sweating during exercise in a neutral climate are determined by H(prod), mass, and BSA, not Vo(? peak).     

Articular area responses to mechanical loading: effects of exercise, age, and skeletal location.

How reliable are reconstructions of body mass and joint function based on articular surface areas? While the dynamic relationship between mechanical loading and cross‐sectional geometry in long bones is well‐established, the effect of loading on the subchondral articular surface area of epiphyses (hereafter, articular surface area, or ASA) has not been experimentally tested. The degree to which ASA can change in size and shape is important, because articular dimensions are frequently used to estimate body mass and positional behavior in fossil species. This study tests the hypothesis that mechanical loading influences ASA by comparing epiphyses of exercised and sedentary sheep from three age categories: juvenile, subadult, and adult (n = 44). ASA was measured on latex molds of subchondral articular surfaces of 10 epiphyses from each sheep. Areas were standardized by body mass, and compared to diaphyseal cross‐sectional geometrical data. Nonparametric statistical comparisons of exercised and control individuals found no increases in ASA in response to mechanical loading in any age group. In contrast, significant differences in diaphyseal cross‐sectional geometry were detected between exercised and control groups, but mostly in juveniles. The conservatism of ASA supports the hypothesis that ASA is ontogenetically constrained, and related to locomotor behavior at the species level and to body mass at the individual level, while variations in diaphyseal cross‐sectional geometry are more appropriate proxies for individual variations in activity level. Am J Phys Anthropol 116:266–277, 2001. © 2001 Wiley‐Liss, Inc.     

Body mass variation is negatively associated with brain size: Evidence for the fat-brain trade-off in anurans

Species can evolve diverse strategies to survive periods of uncertainty. Animals may either invest in energy storage, allowing them to decrease foraging costs, such as locomotion or risk of predation, or they may invest in better cognitive abilities helping them to flexibly adapt their behavior to meet novel challenges. Here, we test this idea of a fat-brain trade-off in 38 species of Chinese anurans by relating the coefficient of variation of body mass (CV_bodymass; as an indicator of how much animals invest into storage over the season) to brain anatomical features. After correcting for shared ancestry and body mass, we found a negative relationship between relative brain size and CV_bodymass. This indicates that anurans seem to trade-off physiological and cognitive buffering during energy shortages. As similar patterns have been reported in arboreal mammals and primates our findings suggest that the fat-brain trade-off, where animals either invest into physiological or cognitive strategies to survive harsh conditions, may be a general pattern across vertebrates.     

The relative gonadal index: an alternative index for quantification of reproductive condition

Gonadal indices (i.e. GSI = gonadal wt/body wt X 100) commonly are used to quantify reproductive condition in fishes. These indices may be inappropriate with specimens of different sizes, however, for gonadal growth often is allometric. A new gonadal index (relative gonadal index, RGI) was developed to quantify the reproductive condition of animals independent of body size. The RGI is based on the underlying model W = alpha i X S beta i, where W is gonadal weight, S is body size (less gonadal weight if body weight is used), and alpha i and beta i are parameters to be estimated for gonadal developmental stage i. Assuming that a multiplicative lognormal error is appropriate, parameter estimates for alpha i and beta i were obtained by linear least squares regression for the log-transformed model ln(W) = beta i X ln(S) + ln(alpha i), where, in this form, beta i is the slope and ln(alpha i) is the intercept. Only if estimates of beta i do not differ significantly among ovarian developmental stages, as in our case, can a pooled estimate of beta be used to obtain the relative gonadal index, RGI = alpha i = W/S beta. Applicability of the RGI was tested using ovaries of three ecologically distinct fish species. The RGI was found to be more appropriate than the gonosomatic index for all three species.     

Comparison of BMI and the body mass/body surface ratio: is BMI a biased tool?

For decades we are used to judge our body composition by using the body mass index (BMI). Since the BMI denominator can be considered as a substitute for body surface area (BSA), the body mass/body surface ratio (BM/BSA) can be calculated. For a distribution of BM/BSA values comparable to the distribution of normal BMI values, the range 35.5-39.9 kg/m2 is chosen as normal, although it covers BM range 50 to 90 kg. The proposed normal BM/BSA range suggests that heavy adults with less than 2 m of height are not obese only if they are less than 90 kg. If the described limitations of the BM/BSA ratio are valid, then the BMI should be regarded as a biased tool, less applicable to individuals with body masses outside the 55 to 90 kg BM range. If we consider many health problems related to the increased body mass, it is possible that the BMI should be used with caution in heavy individuals.     

Metabolic rate and body size

In larger animals a considerable part of the total body mass (e.g. body water, dissolved substances, mineral and organic deposits) does not consume significant amounts of oxygen. These materials can be considered to form a metabolically inert infrastructure which mainly serves three functions: (1) structural support to the organism, (2) storage of nutrients (building material and energy stores) and (3) transport and distribution of these materials. Considering the transport and support function of the metabolically inert structures and their interconnections it is likely that the infrastructure will basically show some tree-like, branching building plan. The weight of the metabolically inert infrastructure of an organism, can be given by bW/(c+W), in which W=body weight, b and c are constants. With increasing size the weight of the metabolic inert infrastructure increases disproportionably. Experimental data concerning basic metabolic rate (M) in relation to body weight (W) better fit the equation M=a W(1-bW)/(c+W), (a=constant) than the conventional power law.     

Lanthanide Salts of Heteropoly Molybdotungstosilicate LnHSiMo10W2O40·xH2O (Ln?=?Pr, Nd, Sm, Gd, Tb, Dy, Yb) Binding to Bovine Serum Albumin: A Fluorescence Quenching Study

In the present work, the interaction between a series of novel lanthanide salts of heteropoly molybdotungstosilicate LnHSiMo(10)W(2)O(40)·xH(2)O (LnW(2); Ln = Pr (x = 23), Nd (x = 24), Sm (x = 26), Gd (x = 20), Tb (x = 23), Dy (x = 21), Yb (x = 25)), and bovine serum albumin (BSA) was investigated by spectroscopic approach at different temperatures under imitated physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by LnW(2) is a result of the formation of LnW(2)-BSA complex. Binding affinity between LnW(2) and BSA was determined using Scatchard equation and the modified Stern-Volmer equation, and the corresponding electronic structure-affinity relationship were discussed. The results of thermodynamic parameters ?G, ?H, ?S at different temperatures indicate that the electrostatic interactions play a major role in LnW(2)-BSA binding process. Moreover, the enthalpy change (?H) and entropy change (?S) were in accordance with the "enthalpy-entropy compensation" equation obtained from this and previous work. Furthermore, the distance r between donor (BSA) and acceptor (LnW(2)) was obtained according to fluorescence resonance energy transfer.     

Efficacy of intermittent, regional microclimate cooling.

The vasomotor response to cold may compromise the capacity for microclimate cooling (MCC) to reduce thermoregulatory strain. This study examined the hypothesis that intermittent, regional MCC (IRC) would abate this response and improve heat loss when compared with constant MCC (CC) during exercise heat stress. In addition, the relative effectiveness of four different IRC regimens was compared. Five heat-acclimated men attempted six experimental trials of treadmill walking ( approximately 225 W/m(2)) in a warm climate (dry bulb temperature = 30 degrees C, dewpoint temperature = 11 degrees C) while wearing chemical protective clothing (insulation = 2.1; moisture permeability = 0.32) with a water-perfused (21 degrees C) cooling undergarment. The six trials conducted were CC (continuous perfusion) of 72% body surface area (BSA), two IRC regimens cooling 36% BSA by using 2:2 (IRC(1)) or 4:4 (IRC(2)) min on-off perfusion ratios, two IRC regimens cooling 18% BSA by using 1:3 (IRC(3)) or 2:6 (IRC(4)) min on-off perfusion ratios, and a no cooling (NC) control. Compared with NC, CC significantly reduced changes in rectal temperature ( approximately 1.2 degrees C) and heart rate ( approximately 60 beats/min) (P < 0.05). The four IRC regimens all provided a similar reduction in exercise heat strain and were 164-215% more efficient than CC because of greater heat flux over a smaller BSA. These findings indicate that the IRC approach to MCC is a more efficient means of cooling when compared with CC paradigms and can improve MCC capacity by reducing power requirements.