Transport of fluid by lens epithelium

We report for the first time that cultured lens epithelial celllayers and rabbit lenses in vitro transport fluid. Layers of the TN4mouse cell line and bovine cell cultures were grown to confluence onpermeable membrane inserts. Fluid movement across cultured layers andexcised rabbit lenses was determined by volume clamp (37°C).Cultured layers transported fluid from their basal to their apicalsides against a pressure head of 3 cmH₂O. Rates were (inµl · h¹ · cm²)3.3 ± 0.3 for TN4 cells (n = 27) and 4.7 ± 1.0 for bovine layers (n = 6). Quinidine, a blocker ofK⁺ channels, andp-chloromercuribenzenesulfonate andHgCl₂, inhibitors of aquaporins,inhibited fluid transport. Rabbit lenses transported fluid from theiranterior to their posterior sides against a2.5-cmH₂O pressure head at 10.3 ± 0.62 µl · h¹ · lens¹(n = 5) and along the same pressurehead at 12.5 ± 1.1 µl · h¹ · lens¹(n = 6). We calculate that this flowcould wash the lens extracellular space by convection about once every2 h and therefore might contribute to lens homeostasis and transparency.     

Increased compliance in diaphragm muscle of the cardiomyopathic Syrian hamster

We investigatedthe hypothesis that diaphragm compliance was abnormal incardiomyopathic Syrian hamsters (CSH), an experimental model ofmyopathy. The passive elastic properties of isolated diaphragm muscleswere analyzed at both the muscle and sarcomere levels. We used thefollowing passive exponential relationship between stress () andstrain ():  = (E_o/)(e  1), where E_o is the initialelastic modulus and  is the stiffness constant. Immunocytochemistryprocedures were used to analyze the distribution of two key elasticcomponents of muscle, extracellular collagen and intracellular titinelastic components, as well as the extracellular matrix glycoproteinlaminin. Muscle and sarcomere values of  were nearly twofold lowerin CSH (8.7 ± 1.9 and 8.3 ± 1.4, respectively) than in controlanimals (19.7 ± 1.7 and 16.8 ± 2.1, respectively)(P < 0.01 for each). Compared withcontrols, E_o was higher in CSH.Sarcomere slack length was significantly longer in CSH than in controlanimals (2.1 ± 0.1 vs. 1.9 ± 0.1 µm,P < 0.05). The surface area ofcollagen I was significantly larger in CSH (17.4 ± 1.8%) than incontrol animals (12.4 ± 0.7%, P < 0.05). There was no change in the distribution of titin or lamininlabelings between the groups. These results demonstrate increaseddiaphragm compliance in cardiomyopathic hamsters. The increase in CSHdiaphragm compliance was observed despite an increase in the surfacearea of collagen and was not associated with an abnormal distributionof titin or laminin.

     

Hypohydration and thermoregulation in cold air

O'Brien, Catherine, Andrew J. Young, and Michael N. Sawka.Hypohydration and thermoregulation in cold air.J. Appl. Physiol. 84(1): 185-189, 1998.This study examined the effects of hypohydration onthermoregulation during cold exposure. In addition, the independentinfluences of hypohydration-associated hypertonicity and hypovolemiawere investigated. Nine male volunteers were monitored for 30 min at25°C, then for 120 min at 7°C, under three counterbalancedconditions: euhydration (Eu), hypertonic hypohydration (HH), andisotonic hypohydration (IH). Hypohydration was achieved 12 h beforecold exposure by inducing sweating (HH) or by ingestion of furosemide(IH). Body weight decrease (4.1 ± 0.2%) caused by hypohydrationwas similar for HH and IH, but differences(P < 0.05) were found between HH andIH in plasma osmolality (292 ± 1 vs. 284 ± 1 mosmol/kgH₂O) andplasma volume reduction (8 ± 2 vs. 18 ± 3%).Heat debt (349 ± 14 among) did not differ(P > 0.05) among trials. Mean skintemperature decreased throughout cold exposure during Eu but plateauedafter 90 min during HH and IH. Forearm-fingertemperature gradient tended (P = 0.06)to be greater during Eu (10.0 ± 0.7°C) than during HH or IH(8.9 ± 0.7°C). This suggests weaker vasoconstrictor tone duringhypohydration than during Eu. Final mean skin temperature was higherfor HH than for Eu or IH (23.5 ± 0.3, 22.6 ± 0.4, and 22.9 ± 0.3°C, respectively), and insulation was lower on HH than onIH (0.13 ± 0.01 vs. 0.15 ± 0.01°C · W¹ · m²,respectively), but not with Eu (0.14 ± 0.01°C · W¹ · m²).This provides some evidence that hypertonicity impairs the vasoconstrictor response to cold. Although mild hypohydration did notaffect body heat balance during 2-h whole body exposure to moderatecold, hypohydration-associated hypertonicity may have subtle effects onvasoconstriction that could become important during a more severe coldexposure.

     

Estimating occupancy of Chinese pangolin (Manis pentadactyla) in a protected and non‐protected area of Nepal

Chinese pangolin is the world's most heavily trafficked small mammal for luxury food and traditional medicine. Although their populations are declining worldwide, it is difficult to monitor their population status because of its rarity and nocturnal behavior. We used site occupancy (presence/absence) sampling of pangolin sign (i.e., active burrows) in a protected (Gaurishankar Conservation Area) and non‐protected area (Ramechhap District) of central Nepal with multiple environmental covariates to understand factors that may influence occupancy of Chinese pangolin. The average Chinese pangolin occupancy and detection probabilities were  ± SE = 0.77 ± 0.08;  ± SE = 0.27 ± 0.05, respectively. The detection probabilities of Chinese pangolin were higher in PA (  ± SE = 0.33 ± 0.03) than compared to non‐PA (  ± SE = 0.25 ± 0.04). The most important covariates for Chinese pangolin detectability were red soil (97%), food source (97.6%), distance to road (97.9%), and protected area (97%) and with respect to occupancy was elevation (97.9%). We recommended use of remote cameras and potentially GPS collar surveys to further investigate habitat use and site occupancy at regular intervals to provide more reliable conservation assessments.     

O2 uptake kinetics after acetazolamide administration during moderate- and heavy-intensity exercise

Inhibition of carbonic anhydrase (CA) isassociated with a lower plasma lactate concentration([La]_pl)during fatiguing exercise. We hypothesized that a lower[La]_plmay be associated with faster O₂uptake (O₂) kinetics during constant-load exercise. Seven men performed cycle ergometer exercise during control (Con) and acute CA inhibition with acetazolamide (Acz,10 mg/kg body wt iv). On 6 separate days, each subject performed 6-minstep transitions in work rate from 0 to 100 W (below ventilatory threshold,<ET)or to a O₂ corresponding to~50% of the difference between the work rate atET and peakO₂(>ET).Gas exchange was measured breath by breath. Trials were interpolated at1-s intervals and ensemble averaged to yield a single response. The mean response time (MRT, i.e., time to 63% of total exponential increase) for on- and off-transients was determined using a two- (<ET) or athree-component exponential model(>ET).Arterialized venous blood was sampled from a dorsal hand vein andanalyzed for[La]_pl.MRT was similar during Con (31.2 ± 2.6 and 32.7 ± 1.2 s for onand off, respectively) and Acz (30.9 ± 3.0 and 31.4 ± 1.5 s for on and off, respectively) for work rates<ET. Atwork rates >ET, MRTwas similar between Con (69.1 ± 6.1 and 50.4 ± 3.5 s for on andoff, respectively) and Acz (69.7 ± 5.9 and 53.8 ± 3.8 s for on and off, respectively). On- and off-MRTs were slower for>ET thanfor <ETexercise.[La]_plincreased above 0-W cycling values during<ET and>ET exercise but was lower at the end of the transition during Acz (1.4 ± 0.2 and 7.1 ± 0.5 mmol/l for<ET and>ET,respectively) than during Con (2.0 ± 0.2 and 9.8 ± 0.9 mmol/lfor <ETand >ET,respectively). CA inhibition does not affectO₂ utilization at the onset of<ET or>ETexercise, suggesting that the contribution of oxidative phosphorylationto the energy demand is not affected by acute CA inhibition with Acz.

     

Age and growth of the blackchin guitarfish Glaucostegus cemiculus (Geoffroy Saint-Hilaire, 1817) from Iskenderun Bay (Northeastern Mediterranean)

Between September 2010 and June 2012, a total 291 (166 females and 125 males) blackchin guitarfish Glaucostegus cemiculus were captured by a commercial bottom trawler (F/V Coşkun Reis) in Iskenderun Bay, Turkey (northeastern Mediterranean Sea). The total length (L) and total weight (W) of the female and male guitarfish ranged between 32.0–165.0 cm and 88 g–16.68 kg, and 34.3–128.3 cm and 112 g–6.00 kg, respectively. Vertebral age estimates ranged from 0 to 8 years for females and 0 to 5 years for males. The growth models of von Bertanlanffy and Gompertz were fitted to the length at age data using the nonlinear regression method. Model selection was based on the values of the residual standard error and the Akaike's information criterion corrected for small sample size (AIC_C) associated with each fit. The von Bertalanffy growth model provided the best fitting growth curves for each sex with parameters reaching L_∞ = 187.17 cm, K = 0.195 year^-1, t₀ = −1.38 year for females, and L_∞ = 144.85 cm, K = 0.321 year^-1, t₀ = −1.13 year^-1 for males. The W–L relationship parameters did not differ significantly between sexes, the estimated values of a and b were 0.0018 and 3.11, respectively. By using these values of a and b, and also respective estimates of L_∞, the values of W_∞ were obtained as 20.53 kg for females and 9.25 kg for males. The overall percentage ratios of females and males in the samples were 57% and 43% respectively.     

Diffusional permeability of rabbit mesothelium

Diffusional permeability (P) to sucrose(P_suc) andNa⁺(P_Na⁺)was determined in specimens of rabbit sternal parietal pericardium,which may be obtained without stripping. Specimens were mounted in anUssing apparatus with ³H-labeledsucrose and²²Na⁺in a luminal (L) or interstitial (I) chamber.P_suc was 2.16 ± 0.44 for LI and 2.63 ± 0.45 (SE) × 10⁵ cm/s for IL,i.e., ~10 times smaller than that previously obtained in strippedspecimens of pleura despite the similarity of intercellular junctionsin pericardium and pleural mesothelium of various species. Thesefindings suggest that previousP_suc wasoverestimated because stripping damages the mesothelium.P_Na⁺ (×10⁵ cm/s) was 7.07 ± 0.71 for LI and 7.37 ± 0.69 × 10⁵ cm/s for IL.Measurements were also done with phospholipids, which are adsorbed onthe luminal side of mesothelium in vivo. With phospholipids in L,P_suc was 0.75 ± 0.10 and 0.65 ± 0.08 andP_Na⁺was 3.80 ± 0.32 and 3.76 ± 0.15 × 10⁵ cm/s for LI andIL, respectively, i.e., smaller than without phospholipids.With phospholipids in I (where they are not adsorbed), P_suc (2.33 ± 0.42 × 10⁵ cm/s) andP_Na⁺(7.01 ± 0.45 × 10⁵ cm/s) were similar tothose values without phospholipids. Hence, adsorbed phospholipidsdecrease P of mesothelium. If themesothelium were scraped away from the specimen,P_suc of theconnective tissue would be 13.2 ± 0.76 × 10⁵ cm/s.P_suc of themesothelium, computed fromP_suc of theunscraped and scraped specimens, corrected for the effect of unstirredlayers (2.54 and 19.4 × 10⁵ cm/s, respectively),was 2.92 and 0.74 × 10⁵ cm/s without and withphospholipids, respectively. Hence, most of the resistance to diffusionof the pericardium is provided by the mesothelium.

     

Allometric modeling does not determine a dimensionless power function ratio for maximal muscular function

Batterham, Alan M., and Keith P. George. Allometricmodeling does not determine a dimensionless power function ratio formaximal muscular function. J. Appl.Physiol. 83(6): 2158-2166, 1997.In the exercise sciences, simple allometry(y = ax^b) israpidly becoming the method of choice for scaling physiological andhuman performance data for differences in body size. The purpose ofthis study is to detail the specific regression diagnostics required tovalidate such models. The sum (T, in kg) of the "snatch" and"clean-and-jerk" lifts of the medalists from the 1995 Men's andWomen's World Weightlifting Championships was modeled as a function ofbody mass (M, in kg). A log-linearized allometric model (ln T = lna + bln M) yielded a common mass exponent(b) of 0.47 (95% confidenceinterval = 0.43-0.51, P < 0.01). However, size-related patterned deviations in the residuals wereevident, indicating that the allometric model was poorly specified and that the mass exponent was not size independent. Model respecification revealed that second-order polynomials provided the best fit, supporting previous modeling of weightlifting data (R. G. Sinclair. Can. J. Appl. Sport Sci. 10:94-98, 1985). The model parameters (means ± SE) were T = (21.48 ± 16.55) + (6.119 ± 0.359)M  (0.022 ± 0.002)M²(R² = 0.97) for men and T = (20.73 ± 24.14) + (5.662 ± 0.722)M  (0.031 ± 0.005)M²(R² = 0.92) for women. We conclude that allometric scaling should beapplied only when all underlying model assumptions have been rigorouslyevaluated.

     

Clinical and pathological associations of the activating RAC1 P29S mutation in primary cutaneous melanoma

Activating mutations in the GTPase RAC1 are a recurrent event in cutaneous melanoma. We investigated the clinical and pathological associations of RAC1^P29S in a cohort of 814 primary cutaneous melanomas with known BRAF and NRAS mutation status. The RAC1^P29S mutation had a prevalence of 3.3% and was associated with increased thickness (OR=1.6 P = 0.001), increased mitotic rate (OR=1.3 P = 0.03), ulceration (OR=2.4 P = 0.04), nodular subtype (OR=3.4 P = 0.004), and nodal disease at diagnosis (OR=3.3 P = 0.006). BRAF mutant tumors were also associated with nodal metastases (OR=1.9 P = 0.004), despite being thinner at diagnosis than BRAF WT (median 1.2 mm versus 1.6 mm, P < 0.001). Immunohistochemical analysis of 51 melanomas revealed that 47% were immunoreactive for RAC1. Melanomas were more likely to show RAC1 immunoreactivity if they were BRAF mutant (OR=5.2 P = 0.01). RAC1 may therefore be important in regulating the early migration of BRAF mutant tumors. RAC1 mutations are infrequent in primary melanomas but may accelerate disease progression.     

How do Different Indices of Obesity Correlate with Cardiometabolic Disease Risk Factors in Multiethnic Youths?

ObjectiveTo investigate the relationship between cardiometabolic disease risk factors (CDRFs) among ethnic minorities and anthropometric factors including body mass index z score, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHTR) in Hispanic and non-Hispanic black youths originating primarily from Central America, South America, and the Caribbean.MethodsClinical data of 167 young persons 2 to 19 years of age encountered in an outpatient pediatric endocrinology clinic were analyzed. The CDRFs included fasting insulin and glucose, homeostasis model assessment of insulin resistance (HOMA-IR), systolic blood pressure (SBP) and diastolic blood pressure (DBP), high-density lipoprotein cholesterol, triglycerides, cardiac C-reactive protein (CRP), and apolipoproteins.ResultsFor both the non-Hispanic black and the Hispanic youths, WC was significantly correlated with SBP (r = 0.63; P < .001 and r = 0.50; P < .001, respectively), DBP (r = 0.61; P < .001 and r = 0.47; P < .001, respectively), and cardiac CRP (r = 0.76; P < .001 and r = 0.26; P = .026, respectively). Similarly, WHTR was significantly correlated with SBP, DBP, and cardiac CRP for the non-Hispanic black study subjects, whereas SBP (r = 0.22; P = .01), DBP ( r = 0.34; P < .001), fasting insulin ( r = 0.43; P < .001), HOMA-IR (r = 0.38; P < .001), apolipoprotein A-I (r = 0.30; P = .01), and CRP (r = 0.44; P < .001) were significantly correlated for the Hispanic group. For both groups, body mass index z score was not consistently correlated with CDRFs, and waist-to-hip ratio was not significantly correlated with any CDRFs, except for apolipoprotein B in non-Hispanic black youths.ConclusionOur study shows that WC and WHTR may be useful anthropometric factors for better identification of ethnic minority youths at risk for adult-onset cardiometabolic disease. (Endocr Pract. 2009;15:403-409)     

Effect of prolonged, heavy exercise on pulmonary gas exchange in athletes

During maximalexercise, ventilation-perfusion inequality increases, especially inathletes. The mechanism remains speculative. Wehypothesized that, if interstitial pulmonary edema is involved, prolonged exercise would result in increasing ventilation-perfusion inequality over time by exposing the pulmonary vascular bed to highpressures for a long duration. The response to short-term exercise wasfirst characterized in six male athletes [maximal O₂ uptake(O_{2 max}) = 63 ml · kg¹ · min¹] by using 5 minof cycling exercise at 30, 65, and 90%O_{2 max}. Multiple inert-gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained. Resting log SD of the perfusion distribution (logSD) was normal [0.50 ± 0.03 (SE)] and increased with exercise (logSD = 0.65 ± 0.04, P < 0.005), alveolar-arterialO₂ difference increased (to 24 ± 3 Torr), and end-capillary pulmonary diffusion limitation occurred at 90%O_{2 max}. The subjectsrecovered for 30 min, then, after resting measurements were taken,exercised for 60 min at ~65%O_{2 max}.O₂ uptake, ventilation, cardiacoutput, and alveolar-arterial O₂difference were unchanged after the first 5 min of this test, but logSD increased from0.59 ± 0.03 at 5 min to 0.66 ± 0.05 at 60 min(P < 0.05), without pulmonary diffusion limitation. LogSD was negativelyrelated to total lung capacity normalized for body surface area(r = 0.97,P < 0.005 at 60 min). These data are compatible with interstitial edema as a mechanism and suggest that lungsize is an important determinant of the efficiency of gas exchangeduring exercise.

     

Magnitude and time course of hemodynamic responses to Mueller maneuvers in patients with congestive heart failure

To simulate theimmediate hemodynamic effect of negative intrathoracic pressure duringobstructive apneas in congestive heart failure (CHF), without inducingconfounding factors such as hypoxia and arousals from sleep, eightawake patients performed, at random, 15-s Mueller maneuvers (MM) attarget intrathoracic pressures of 20 (MM 20) and40 cmH₂O (MM 40),confirmed by esophageal pressure, and 15-s breath holds, as apneic timecontrols. Compared with quiet breathing, at baseline, before theseinterventions, the immediate effects [first 5 cardiac cycles(SD), P values refer to MM 40compared with breath holds] of apnea, MM 20, and MM 40 were, for left ventricular (LV) systolic transmural pressure (Ptm), 1.0 ± 1.9, 7.2 ± 3.5, and 11.3 ± 6.8 mmHg(P < 0.01); for systolic bloodpressure (SBP), 2.9 ± 2.6, 5.5 ± 3.4, and 12.1 ± 6.8 mmHg (P < 0.01); and forstroke volume (SV) index, 0.4 ± 2.8, 4.1 ± 2.8, and6.9 ± 2.3 ml/m²(P < 0.001), respectively.Corresponding values over the last five cardiac cycles were for LVPtm6.4 ± 4.4, 5.4 ± 6.6, and 4.5 ± 9.1 mmHg (P < 0.01); for SBP6.9 ± 4.2, 8.2 ± 7.7, and 24.2 ± 6.9 mmHg (P < 0.01); and for SVindex 0.4 ± 2.1, 5.2 ± 2.8, and 9.2 ± 4.8 ml/m²(P < 0.001), respectively.Thus, in CHF patients, the initial hemodynamic response to thegeneration of negative intrathoracic pressure includes an immediateincrease in LV afterload and an abrupt fall in SV. The magnitude ofresponse is proportional to the intensity of the MM stimulus. By theend of a 15-s MM 40, LVPtm falls below baseline values, yet SVand SBP do not recover. Thus, when 40cmH₂O intrathoracic pressure issustained, additional mechanisms, such as a drop in LV preload due toventricular interaction, are engaged, further reducing SV. The neteffect of MM 40 was a 33% reduction in SV index (from 27 to 18 ml/min²), and a 21% reductionin SBP (from 121 to 96 mmHg). Obstructive apneas can have adverseeffects on systemic and, possibly, coronary perfusion in CHF throughdynamic mechanisms that are both stimulus and timedependent.

     

Enhancement of intestinal water absorption and sodium transport by glycerol in rats

Wapnir, Raul A., Maria C. Sia, and Stanley E. Fisher.Enhancement of intestinal water absorption and sodium transport byglycerol in rats. J. Appl. Physiol.81(6): 2523-2527, 1996.Glycerol (Gly) is a hydrophilic,absorbable, and energy-rich solute that could make water absorptionmore efficient. We investigated the use of Gly in a high-energybeverage containing corn syrup (CS) by using a small intestineperfusion procedure in the rat, an approach shown earlier to providegood preclinical information. The effectiveness of several formulationswith Gly and CS was compared with commercial products and toexperimental formulas where Gly substituted for glucose (Glc). TheCS-Gly combination was more effective than preparations on the marketcontaining sucrose and Glc-fructose syrups (G-P and G-L, respectively)in maintaining a net water absorption balance in the test jejunal segment [CS-Gly = 0.021 ± 0.226, G-L = 1.516 ± 0.467, and G-P = 0.299 ± 0.106 (SE)µl ^· min^{1 ·} cm¹(P = 0.0113)] and in reducingsodium release into the lumen [CS-Gly = 133.2 ± 16.2, G-L = 226.7 ± 25.2, and G-P = 245.6 ± 23.4 nmol ^· min^{1 ·} cm¹(P = 0.0022)]. In otherpreparations, at equal CS concentrations (60 and 80 g/l, respectively),Gly clearly improved net water absorption over a comparableGlc-containing product [CS60-Gly = 0.422 ± 0.136 and CS80-Gly = 0.666 ± 0.378 vs. CS60-Glc = 0.282 ± 0.200 andCS80-Glc = 1.046 ± 0.480 µl ^· min^{1 ·} cm¹(P = 0.0019)]. On the basis ofthe data of this rat intestine perfusion model, Gly could be a usefulingredient in energy-rich beverages and might enhance fluid absorptionin humans.

     

Copy number variation and neuropsychiatric illness

Identification of neuropsychiatric CNVs. A) Schematic of a deletion and duplication. B) Example of a locus enriched for deletions in cases. C) Number of risk CNVs implicated in published studies of neuropsychiatric disorders. The number of cases included in each study is shown on the x axis, and larger points represent studies with more control samples (see Table 1 for further details). SCZ = schizophrenia, ASD = autism spectrum disorder, ID = intellectual disability, MDD = major depressive disorder, ADHD = attention-deficit hyperactivity disorder, TS = Tourette syndrome, OCD = obsessive compulsive disorder, BD = bipolar disorder.

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Effect of luteal phase elevation in core temperature on forearm blood flow during exercise

Kolka, Margaret A., and Lou A. Stephenson. Effect ofluteal phase elevation in core temperature on forearm blood flow duringexercise. J. Appl. Physiol. 82(4):1079-1083, 1997.Forearm blood flow (FBF) as an index of skinblood flow in the forearm was measured in five healthy women by venousocclusion plethysmography during leg exercise at 80% peak aerobicpower and ambient temperature of 35°C (relative humidity 22%;dew-point temperature 10°C). Resting esophagealtemperature (T_es) was 0.3 ± 0.1°C higher in the midluteal than in the early follicular phase ofthe menstrual cycle (P < 0.05).Resting FBF was not different between menstrual cycle phases. TheT_es threshold for onset of skinvasodilation was higher (37.4 ± 0.2°C) in midluteal than inearly follicular phase (37.0 ± 0.1°C; P < 0.05). The slope of the FBF toT_es relationship was not different between menstrual cycle phases (14.0 ± 4.2 ml · 100 ml¹ · min¹ · °C¹for early follicular and 16.3 ± 3.2 ml · 100 ml¹ · min¹ · °C¹for midluteal phase). Plateau FBF was higher during exercise inmidluteal (14.6 ± 2.2 ml · 100 ml¹ · min¹ · °C¹)compared with early follicular phase (10.9 ± 2.4 ml · 100 ml¹ · min¹ · °C¹;P < 0.05). The attenuation of theincrease in FBF to T_es occurred when T_es was 0.6°C higher andat higher FBF in midluteal than in early follicular experiments(P < 0.05). In summary, the FBF response is different during exercise in the two menstrual cycle phasesstudied. After the attenuation of the increase in FBF and whileT_es was still increasing, thegreater FBF in the midluteal phase may have been due to the effects ofincreased endogenous reproductive endocrines on the cutaneousvasculature.

     

Excess postexercise oxygen consumption and recovery rate in trained and untrained subjects

Short, Kevin R., and Darlene A. Sedlock. Excesspostexercise oxygen consumption and recovery rate in trained anduntrained subjects. J. Appl. Physiol.83(1): 153-159, 1997.The purpose of this study was todetermine whether aerobic fitness level would influence measurements ofexcess postexercise oxygen consumption (EPOC) and initial rate ofrecovery. Twelve trained [Tr; peak oxygen consumption(O_{2 peak}) = 53.3 ± 6.4 ml · kg¹ · min¹]and ten untrained (UT;O_{2 peak} = 37.4 ± 3.2 ml · kg¹ · min¹)subjects completed two 30-min cycle ergometer tests on separate days inthe morning, after a 12-h fast and an abstinence from vigorous activityof 24 h. Baseline metabolic rate was established during the last 10 minof a 30-min seated preexercise rest period. Exercise workloads weremanipulated so that they elicited the same relative, 70%O_{2 peak} (W70%), orthe same absolute, 1.5 l/min oxygen uptake(O₂) (W1.5), intensity forall subjects, respectively. RecoveryO₂, heart rate (HR), andrespiratory exchange ratio (RER) were monitored in a seated positionuntil baseline O₂ wasreestablished. Under both exercise conditions, Tr had shorter EPOCduration (W70% = 40 ± 15 min, W1.5 = 21 ± 9 min) than UT(W70% = 50 ± 14 min; W1.5 = 39 ± 14 min), but EPOC magnitude(Tr: W70% = 3.2 ± 1.0 litersO₂, W1.5 = 1.5 ± 0.6 liters O₂; UT: W70% = 3.5 ± 0.9 liters O₂, W1.5 = 2.4 ± 0.6 liters O₂) was not different between groups. The similarity of Tr and UT EPOCaccumulation in the W70% trial is attributed to the parallel declinein absolute O₂ during mostof the initial recovery period. Tr subjects had faster relative declineduring the fast-recovery phase, however, when a correction for theirhigher exerciseO₂ was taken.Postexercise O₂ was lowerfor Tr group for nearly all of the W1.5 trial and particularly duringthe fast phase. Recovery HR kinetics were remarkably similar for bothgroups in W70%, but recovery was faster for Tr during W1.5. RER valueswere at or below baseline throughout much of the recovery period in both groups, with UT experiencing larger changes than Tr in both trials. These findings indicate that Tr individuals have faster regulation of postexercise metabolism when exercising at either thesame relative or same absolute work rate.