Environmental influences on Adelie penguin breeding schedules, endocrinology, and chick survival.

To understand how the social and physical environment influences behaviour, reproduction and survival, studies of underlying hormonal processes are crucial; in particular, interactions between stress and reproductive responses may have critical influences on breeding schedules. Several authors have examined the timing of breeding in relation to environmental stimuli, while others have independently described endocrine profiles. However, few studies have simultaneously measured endocrine profiles, breeding behaviour, and offspring survival across seasons. We measured sex and stress hormone concentrations (oestrogens, testosterone, and corticosterone), timing of breeding, and chick survival, in Adelie penguins (Pygoscelis adeliae) at two colonies in two different years. Clutch initiation at Cape Bird South (CBS; year 1, ~14,000 pairs) occurred later than at Cape Crozier East (CCE; year 2, ~ 25,000 pairs); however, breeding was more synchronous at CBS. This pattern was probably generated by the persistence of extensive sea ice at CBS (year 1). Higher corticosterone metabolite and lower sex hormone concentrations at CBS correlated with later breeding and lower chick survival compared to at CCE - again, a likely consequence of sea ice conditions. Within colonies, sub-colony size (S, 50-100; M, 200-300; L, 500-600; XL, >1000 pairs) did not influence the onset or synchrony of breeding, chick survival, or hormone concentrations. We showed that the endocrine profiles of breeding Adelie penguins can differ markedly between years and/or colonies, and that combining measures of endocrinology, behaviour, and offspring survival can reveal the mechanisms and consequences that different environmental conditions can have on breeding ecology.

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae.

Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure that they correlate. We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma 'snapshot' concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, whilst plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure that they select the most appropriate matrix and method of hormone measurement to answer their research questions.

Trends in the incidence of bladder cancer in Nova Scotia: a twenty-year perspective.

INTRODUCTION: Bladder cancer is the most common malignant tumor of the urinary system. Tobacco smoking has been implicated as a major risk factor for the development of bladder cancer and Nova Scotia has some of the highest smoking rates in Canada. We examined trends in the incidence of bladder cancer in Nova Scotia between 1980 and 1999. MATERIALS AND METHODS: Data on incident cases of bladder cancer diagnosed in Nova Scotia over a twenty-year period (1980 - 1999) were obtained from the Nova Scotia Cancer Registry. The age- standardized incidence and mortality due to bladder cancer was calculated for both genders. Trends in the incidence of bladder cancer during the study period were analyzed for three different age groups in each gender as an estimate of birth cohort. The average annual percent change (AAPC) in incidence of bladder cancer was calculated. RESULTS: Between 1980 and 1999, 3569 cases of bladder cancer were reported (male: female = 2.9:1). The overall incidence of bladder cancer increased in both males (27.5 to 39.5 cases per 100 000) and females (7.0 to 10.7 cases per 100 000). Mortality rates were stable. There was a trend towards an increase in bladder cancer rates for all age groups analyzed, with a substantial rise occurring in females less than 65 years of age. The AAPC in incidence of bladder cancer was +1.5 for males and +2.6 for females. CONCLUSIONS: We hypothesize that the rising incidence of bladder cancer in Nova Scotia, particularly in individuals less than 65 years of age, is related to changes in cigarette smoking practices during the past century. As the population ages, we are likely to see an increased incidence of bladder cancer in females.

Body temperature in sedentary adults during moderate exercise: no effect from exercise the day before.

BACKGROUND: Epidemiological findings show a continued presence of exertional heat injury during military basic recruit training. Current guidelines do not consider the carry-over effects of prior exercise or exposure to high ambient temperatures on the risk of succumbing to heat illness. HYPOTHESIS: From the epidemiological evidence we hypothesized that both prior exercise and exposure to hot environments on the day before would increase the core temperature response during exercise the next day. METHODS: Seven sedentary and non heat-acclimated men and women each performed eight randomized exposures involving treadmill walking for a maximum of 2 h every 2 wk. Two separate control trials at a wet bulb globe temperature (WBGT) of 22.5 degrees C and 26.5 degrees C consisted of exercise during the morning only. Six experimental trials involved successive days of exercise with trials on the second day at either a WBGT of 22.5 degrees C or 26.5 degrees C. All of the experimental trials involved walking during the first morning at a WBGT of 22.5 degrees C. Further, four of these trials included additional exercise in the afternoon at either a WBGT of 22.5 degrees C (two trials) or 29.5 degrees C (two trials). RESULTS: There was no impact of prior exercise on the day preceding the tests at either WBGT for any of the dependent measures. Rectal temperatures increased to 38.0 degrees C at the WBGT of 22.5 degrees C and to 38.5 degrees C for trials at 26.5 degrees C. There were also no carry-over effects from exercise conducted during the preceding afternoon. CONCLUSIONS: Under situations where individuals are well hydrated, rested, and free of injury, illness, and drug use, repeated exercise bouts on successive days do not alter the thermoregulatory response to exercise.

Effect of caffeine and ephedrine ingestion on anaerobic exercise performance.

PURPOSE: Ingestion of a combination of caffeine (C) and ephedrine (E) prolongs time to exhaustion during high-intensity aerobic exercise. CNS stimulation by C and E was proposed as part of the mechanism for the improvement. It was thought that this arousal might also be of benefit during anaerobic exercise. The purpose of this study was to investigate the effect of C, E, and C+E ingestion on performance of anaerobic exercise. METHODS: Two groups were used to evaluate the effect of C and E on anaerobic performance. Group 1 (WIN) consisted of 16 healthy untrained male subjects who performed a 30-s Wingate test. Group 2 (MAOD) consisted of 8 healthy untrained male subjects who performed a supramaximal (125%VO(2peak)) cycle exercise trial to exhaustion to determine maximum accumulated oxygen deficit. The trials commenced 1.5 h after ingesting either C (5 mg x kg(-1)), E (1 mg x kg(-1)), a combination of C+E, or a placebo (P). All trials were randomized and double blind. Blood samples were assayed for lactate and glucose post drug ingestion just before exercise, and again 3, 5, and 10 min post exercise. Catecholamines were measured in the preexercise and 10-min postexercise blood samples. RESULTS: Ephedrine increased power output during the early phase of the Wingate test, whereas C increased time to exhaustion and O(2) deficit during the MAOD test. C, E, and C+E increased blood lactate, glucose, and catecholamine levels. CONCLUSION: The improvement in anaerobic exercise performance is likely a result of both stimulation of the CNS by E and skeletal muscle by C.

Caseating granulomas on the glans penis as a complication of bacille calmette-guérin intravesical therapy.

Intravesical instillation of bacille Calmette-Guérin (BCG) in patients with superficial bladder cancer or with carcinoma in situ of the bladder is a frequently used therapeutic option. As with other cancer therapies, BCG instillation has its share of side effects and complications. This case report highlights an uncommon complication.

Reducing the dose of combined caffeine and ephedrine preserves the ergogenic effect.

BACKGROUND: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine (E) was reported to have an ergogenic effect on high intensity aerobic exercise performance, but 25% of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment. The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect. METHODS: Twelve healthy untrained male subjects completed four randomized and double-blind, cycle ergometer trials to exhaustion at a power output equivalent to approximately 85% Vo2peak 1.5-2 hours after ingesting a placebo (P) or a mixture of C+E in the following doses: 5 mg x kg(-1) of C plus 0.8 mg x kg(-1) of E (CLE); 4 mg x kg(-1) of C plus 1 mg x kg(-1) of E (LCE); or 4 mg x kg of C plus 0.8 mg x kg(-1) of E (LCLE). Trials were separated by 1 wk. Venous blood samples were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion. Vo2, Vco2, VE, and RQ were measured every minute throughout the exhaustion ride. Heart rate and perceived exertion (RPE) were also recorded every 5 min and at the end of the exercise session. RESULTS: Plasma levels of C and E immediately before the exhaustion ride were (mean +/- SD): 38.7+/-5.2 micromol x L(-1) C, 1.285+/-0.275 micromol x L(-1) E in the CLE trial; 33.2+/-5.8 micromol x L(-1) C, 1.462+/-0.283 micromol x L(-1) E in the LCE trial; 33.0+/-2.9 micromol x L(-1) C, 1.229+/-0.202 micromol x L(-1) E in the LCLE trial. The times to exhaustion for the treatment trials (CLE = 27.5+/-12.4 min, LCE = 27.6+/-10.9 min, LCLE = 28.2+/-9.3 min) were similar and were significantly greater than placebo (p = 17.0+/-3.0 min). The drugs did not affect Vo2, Vco2, or VE. Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E, LCLE. CONCLUSIONS: A lower dose of C+E resulted in an ergogenic effect similar in magnitude to that reported previously with a higher dose, and with a reduced incidence of negative side effects.

Efficacy of air and liquid cooling during light and heavy exercise while wearing NBC clothing.

BACKGROUND: Studies, to date, have not revealed the extent to which the heat strain of continuous heavy exercise while wearing NBC protective clothing can be reduced by providing liquid- or air-cooling and whether one system is more effective than the other in aiding heat transfer from the body and the clothing. It was of interest to know to what extent present-day cooling technologies can reduce the heat strain of light and heavy exercise in NBC clothing and to compare these reductions to other strategies that have employed changes in clothing design. HYPOTHESIS: It was hypothesized that there would be no difference between the liquid and air cooling systems and that sufficient cooling power would be delivered to the body to reduce the heat strain of heavy exercise to a level similar to that experienced with light exercise when no cooling was provided. METHODS: Eight males performed 6 randomized exposures for a maximum of 3 h at 40 degrees C and 30% relative humidity that involved either light (L) (walking at 3.5 km x h(-1) or heavy (H) (walking at 4.8 km x h(-1) and a 5% grade) exercise while wearing the NBC protective clothing ensemble with no cooling (N), liquid (L) or air (A) cooling. RESULTS: For L exercise, tolerance time was significantly increased from 100 min with N to the maximum of 3 h with either cooling system. There was no difference between L and A cooling in the extent of the changes in rectal temperature, heart rate and heat flow. For H exercise, tolerance time was significantly increased 150% from 57 min with N to 149 min with L and 140 min with A. These latter values for HL and HA were not different from each other but both were significantly greater than L exercise with N. Rectal temperature increased more quickly during HL compared with HA during the first 60 min of exposure but there were no differences between cooling trials for the remainder of the heat exposure. CONCLUSIONS: It was concluded that sufficient cooling power could be delivered to the body to effectively reduce the heat strain of wearing NBC protective clothing during heavy exercise in a hot environment to a level comparable to or slightly lower than that experienced with light exercise and no cooling.

Accurate PEG tube placement with magnetic positional imaging.

BACKGROUND: Percutaneous endoscopic gastrostomy (PEG) is a common procedure and accounts for an increasing proportion of an endoscopist's workload. Serious complications can occur from inaccurate abdominal wall puncture. Electronic three-dimensional imaging has been used to aid colonoscopy. We adapted the principles of this technique to PEG insertion in a procedure called magnetic positional imaging. METHODS: Magnetic positional imaging was used to determine the abdominal wall puncture site and angle of insertion that would provide the shortest distance from abdominal wall to the stomach. The pull-through technique was used to perform PEG. RESULTS: PEG insertion with magnetic positional imaging was performed on four patients without complications. The average distance between the internal and external sensors was 5 mm. CONCLUSION: A new technique, magnetic positional imaging, facilitates the pull-through technique for PEG. Additional studies are needed to clarify the potential benefit in endoscopic practice.

Thermal regulation in the heat during exercise after caffeine and ephedrine ingestion.

BACKGROUND: Ingesting a combination of caffeine and ephedrine (C+E) has been shown to raise metabolic heat production and body temperature. This side effect of C+E ingestion may be positive during a cold stress scenario, however, during heat stress it could prove to be detrimental. Thus, the purpose of this study was to clarify the effect of C+E ingestion on body temperature regulation during moderate exercise in a hot dry environment. METHODS: Ten, healthy, non heat acclimated, males exercised at 50% VO2peak in a 40 degrees C and 30% RH environment until rectal temperature reached 39.3 degrees C; heart rate (HR) remained at 95% of peak value or greater for 3 min, dizziness or nausea precluded further exercise, or 3 h had elapsed. They did this four times at weekly intervals: familiarization (Fam), control (Cont), placebo, and C+E (5 mg . kg(-1) caffeine + 1 mg . kg(-1) ephedrine) trials. The Fam and Cont treatments were done first and sequentially while the placebo and C+E treatments were balanced and double-blind. Tolerance times, mean skin temperature (Tsk), rectal temperature (Tre), Vo2, Vco2, VE, sweat rate (SR), HR, and sensation of thermal comfort were measured. RESULTS: Tolerance times (mean+/-SD in minutes) were similar for the placebo (120.0+/-28.4) and C+E (121.3+/-33.9) trials and both times were significantly longer than Cont (106.6+/-24.0) trial. C+E did not affect Tsk, initial TrC, delta Tre, SR or the sensation of thermal comfort. VO2 and VF, were significantly increased by C+E. HR was elevated by C+E compared with the other trials, but only during the initial 20 min of exercise. CONCLUSION: Although the metabolic rate was slightly increased with C+E treatment, it was sufficiently offset by increased heat loss mechanisms so that internal body temperature was not increased during moderate exercise in a hot, dry environment.

Combined caffeine and ephedrine ingestion improves run times of Canadian Forces Warrior Test.

The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exercise time to exhaustion during cycle ergometry at 85% VO2max. The present study was undertaken to investigate whether this enhancement would occur in a field setting and if drug ingestion on 1 d would affect performance 1 d later. Two hours after ingesting either a combination of 375 mg of C and 75 mg E (C+E), or a placebo (P), 9 healthy male recreational runners completed six balanced and double-blind trials of the Canadian Forces Warrior Test (WT), a 3.2 km run wearing "fighting order" which weighed about 11 kg. The trials were performed in sets of two runs, i.e., two runs were done 24 h apart, and these sets were separated by a minimum of 7 d. The sets were: C+E trial on day 1 (D1), placebo on day 2 (P2); placebo first (P1), C+E second (D2); and placebo first (P3), placebo second (P4). In addition, 1 wk before the treatment trials the subjects performed a control trial WT. During the WT, heart rates (HR) were recorded every minute. Plasma C and E levels immediately before the WT were similar for both C+E trials, but were undetectable for all P trials. Run times (mean+/-SD) were 15.3+/-0.6, 15.4+/-0.9, 15.5+/-1.2, 15.4+/-0.9, 15.4+/-0.9, 14.8+/-0.7, and 14.6+/-0.8 min for control, P1, P2, P3, P4, D1, D2 trials, respectively. The two C+E trial run times were similar and both were significantly faster (p < 0.05) than control and all placebo trials. HR during the WT was significantly higher (p < 0.05) for the C+E trials compared with the other trials. WT performance was not impaired by C+E ingestion 24 h earlier. In conclusion, performance of the WT was improved by ingestion of C+E.

Effects of caffeine, ephedrine and their combination on time to exhaustion during high-intensity exercise.

This study investigated the effects of acute ingestion of caffeine (C), ephedrine (E) and their combination (C+E) on time to exhaustion during high-intensity exercise. Using a repeated-measures, double-blind design, eight male subjects exercised on a cycle ergometer at a power output that led to exhaustion after about 12.6 min during a placebo (P) control trial. They did this 1.5 h after ingesting either C (5 mg x kg[-1]), E (1 mg x kg[-1]), C+E, or P. Trials were separated by 1 week. Venous blood was sampled before and during exercise. The mean (SD) times to exhaustion were 12.6 (3.1) (P), 14.4 (4.1) (C), 15.0 (5.7) (E) and 17.5 (5.8) (C+E) min. Only the C+E treatment significantly increased time to exhaustion compared to P. Oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE) and the respiratory exchange ratio (RER) were similar during exercise for all trials. Heart rate during exercise was significantly increased for the C+E and C trials compared to P. Subjective ratings of perceived exertion during exercise were significantly lower after C+E compared to P. All treatments significantly increased lactate levels. Free fatty acid (FFA) levels were significantly increased by C ingestion. Glycerol levels were increased by C+E and C ingestion. Glucose levels were also higher with the drug treatments compared to P. Increased monamine availability after C+E treatment was suggested by measurements of catecholamines and dopamine. In conclusion, the combination of C+E significantly prolonged exercise time to exhaustion compared to P, while neither C nor E treatments alone significantly changed time to exhaustion. The improved performance was attributed to increased central nervous system stimulation.

Hereditary prostate cancer in Nova Scotia.

A case control study of 244 prostate cancer patients and 240 of their female partners was performed. The study sample was generated by the following methods: 1) an advertisement was placed in two newspapers with province-wide distribution 2) all Nova Scotia urologists were asked to identify patients with a positive family history and 3) consecutive patients treated for prostate cancer in an ambulatory setting were contacted by telephone. Seven men and 27 women did not know their family history. Patients with a positive family history (43/237, 18%) became case group. Wives who had family members affected by prostate cancer (16/213, 7.5%) comprised the control group. Both cases and controls completed a standardized questionnaire by mail or telephone. The heredity variant of prostate cancer accounted for 5 %, the familial 12% and the sporadic 83% of cases studied and 0%, 9% and 91%, respectively of the control group. The odds ratio calculated for first-and second-degree relatives was 2.73 (95% confidence interval, 1.49-5.01). The mean age at diagnosis of these cases was 68 years. There was not a statistically significant difference between the familial (69 years) and hereditary (67 years) subgroups' mean age at diagnosis (p=0.4). Most men with prostate cancer in the Nova Scotia population sample were affected by the sporadic variant. Small but important groups were affected by familial or hereditary types. Identification of these families will have important implications for screening and gene mapping studies.

Bilateral temporal lobe MRI changes in uncomplicated hypoglycemic coma.

We report bilateral temporal lobe MRI findings in a patient following an episode of prolonged hypoglycemia uncomplicated by coexisting anoxia, hypotension, acidosis, drug intoxication, infection, or status epilepticus. The MRI findings are discussed in relation to the experimental and human data on hypoglycemic neuronal injury.

Heart rate and oxygen uptake relationship: a comparison of loaded marching and running in women.

Heart rate (beats.min-1; fc) measured during marching with a load is often used to predict the oxygen cost (l.min-1; VO2) of the activity. The prediction comes from the fc/VO2 relationship determined from laboratory measures of fc and VO2 during treadmill running. Studies in men have suggested that this may not be appropriate although this has yet to be examined in women. This study, therefore, compared the fc/VO2 relationship between loaded marching and maximal running protocols in women. Sixteen female subjects [mean (SD), age 21.9 (2.3) years, height 6 (0.06) m, weight 62.6 (7.6) kg] had their fc (from three-lead chest electrodes) and VO2 measured first during standard treadmill run protocols, and again 1 week later during loaded marching protocols. The slopes and intercepts determined from linear regression of fc on VO2 for each individual for each protocol were compared as were the maximal fc(fcmax), VO2 and ratings of perceived exertion (RPE) from the last work period of each protocol in paired t-tests. The fc/VO2 slopes (P < 0.01) and intercepts (P < 0.05) differed significantly between loaded marching and running. fcmax for loaded marching were 90% of fcmax for running (P < 0.01) and VO2peak for loaded marching were 80% of those for running (P < 0.01). However, RPE at the final levels for the two protocols were not significantly different. The data suggest that in women the fc/VO2 relationships for loaded marching and for running are different. This difference is similar to that found in men when speed is held constant and the load and gradient are varied. The results suggest that it would be erroneous to use fc and VO2 measured during running protocols in the laboratory to estimate energy expenditure and work intensity during loaded marching in the field.

Heat strain with combat clothing worn over a chemical defense (CD) vapor protective layer.

The purpose of the present study was to quantify and compare the heat strain when a new chemical defense (CD) vapor protective layer was worn under combat clothing. There were 23 unacclimatized males (27.1 +/- 5.6 y, 80.9 +/- 9.3 kg, 1.78 +/- 0.05 m) assigned to a light intermittent (L, n = 7), moderate continuous (M, n = 8) or heavy continuous (H, n = 8) exercise group. All subjects performed three trials at 40 degrees C and 30% relative humidity wearing the current CD protective clothing over combat clothing (CD-current), the CD vapor protective layer alone (CD-vapor) or under combat clothing (CD-vapor/combats). Tolerance times were significantly different among the three clothing trials for each exercise group. For group L, tolerance time increased from 116 min for CD-current to 208 min for CD-vapor/combats and to 289 min for CD-vapor. For group M, tolerance time increased from 67 to 87 and to 133 min for CD-current, CD-vapor/combats and CD-vapor, respectively. Finally for group H, respective times for CD-current, CD-vapor/combats and CD-vapor were 50 min, 59 min and 80 min. Significant differences among the clothing configurations were found also for the evaporative efficiency of sweat from the clothing, heart rates, rectal and skin temperatures. In all conditions, the response during CD-vapor/combats was between CD-current and CD-vapor. Although heat strain was reduced compared with CD-current, the improvements with CD-vapor/combats might be considered significant in an operational environment only at low metabolic rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Unusual presentations of advanced prostate cancer.

With the advent of prostatic-specific antigen, transrectal ultrasound and an increasing awareness of prostate cancer among the population, prostate cancer is being detected at an increasingly early stage. Despite this, it is estimated that up to 40% of the patients present with manifestations of metastatic prostate cancer. Although the most common sites for metastases at presentation are the obturator lymph nodes and the bony skeleton, advanced prostate cancer may produce a variety of clinical scenarios by involving contagious and distant organs. Such presentations of advanced prostate cancer can add significantly to the morbidity and mortality of this disease. In brief review, we will focus on uncommon presentations of advanced prostate cancer.

The influence of air temperature on the EMG/force relationship of the quadriceps.

Surface electromyography (EMG) in the past has been used to estimate the intensity of muscle contraction. These estimates were derived from the EMG/force relationship measured at room temperature. How the surface EMG signal is influenced by varying air temperature as it relates to the EMG/force relationship has yet to be investigated. Thus, this study evaluated the influence of different air temperatures (10, 23 and 40 degrees C) on surface EMG during contractions of the quadriceps muscle. Ten subjects [mean (SD) age 29 (7) years and weight 78.3 (7.8) kg] performed a criterion task of five contractions ranging from 10 to 100% of a maximal voluntary contraction, five times over a 1.5-h period in all conditions. The EMG signals generated from the rectus femoris, and the forces associated with the contractions, were captured on FM tape and subsequently digitized at a sampling rate of 2000 Hz. The relationship between EMG and force was different under the different conditions; EMG was reduced at a given force as temperature increased, and the EMG increased in the 10 degrees C environment over time. The differences that occurred at the various temperatures were believed to be related to fluid distribution in the muscle, muscle conduction velocity and sweating. The data imply that the EMG/force relationship measured using surface electrodes is influenced by ambient temperature.

Relative intensity of muscular contraction during shivering.

The intensity of cold-induced shivering, quantified by surface electromyography (EMG) and then expressed as a function of the maximal myoelectrical activity (integrated EMG) obtained during a maximum voluntary contraction (MVC), was examined in this study in individuals classified by body fat. In addition, the relationship between shivering and metabolic rate (MR) and the relative contribution of various muscle groups to total heat production were studied. Ten seminude male volunteers, 5 LEAN (less than 11% body fat) and 5 NORM (greater than 15% body fat) were exposed to 10 degrees C air for 2 h. EMG of six muscle groups (pectoralis major, rectus abdominis, rectus femoris, gastrocnemius, biceps brachii, and brachioradialis) was measured and compared with the EMG of each muscle's MVC. A whole body index of shivering, determined from the mass-weighted intensity of shivering of each muscle group, was correlated with MR. After the initial few minutes of exposure, only the pectoralis major, rectus femoris, and biceps brachii continued to increase their intensity of shivering. Shivering intensity was higher in the central muscles, ranging from 5 to 16% of MVC compared with that in the peripheral muscles, which ranged from 1 to 4% of MVC. Shivering intensities were similar in the peripheral muscles for the LEAN and NORM groups, whereas differences occurred in the trunk muscles for the pectoralis major and rectus abdominis. The whole body index of shivering correlated significantly with each individual's increase in MR (r = 0.63-0.97).(ABSTRACT TRUNCATED AT 250 WORDS)