Influence of higher-grade walking on metabolic demands in young untrained Japanese women

The primary purpose of this study was to document the physiological responses of level walking and running (LW/R) at various speeds, and grade walking (GW) at various grades on a treadmill. Twenty-four young untrained Japanese women performed 2 tests on the specially designed treadmill for a higher grade exercise. The first test was the LW/R with increase of speeds, 33.3, 66.7, 91.7, and 116.7 m.min(-1). The first 3 progressions were for walking and the last progression was for running. The second test was the GW with increase of grades 0, 10, 20, and 30% with the velocity of 33.3 m.min(-1) in all progressions. The different combinations of speeds and grade for the progressions used in this study were selected based on the results of preliminary pilot studies, so that the percent heart rate maximim (%HRmax) was reached at the minimum intensities recommended to allow improving cardiorespiratory fitness by the American College of Sports Medicine (ACSM). Significant (p 相似文献   

Longitudinal changes in aerobic power in older men and women.

The purpose of this study was to describe the longitudinal (10 yr) decline in aerobic power [maximal O(2) uptake (Vo(2 max))] and anaerobic threshold [ventilatory threshold (T(Ve))] of older adults living independently in the community. Ten years after initial testing, 62 subjects (34 men, mean age 73.5 +/- 6.4 yr; 28 women, 72.1 +/- 5.3 yr) achieved Vo(2 max) criteria during treadmill walking tests to the limit of tolerance, with T(Ve) determined in a subset of 45. Vo(2 max) in men showed a rate of decline of -0.43 ml.kg(-1).min(-1).yr(-1), and the decline in Vo(2 max) was consequent to a lowered maximal heart rate with no change in the maximum O(2) pulse. The women showed a slower rate of decline of Vo(2 max) of -0.19.ml.kg(-1).min(-1).yr(-1) (P < 0.05), again with a lowered HR(max) and unchanged O(2) pulse. In this sample, lean body mass was not changed over the 10-yr period. Changes in Vo(2 max) were not significantly related to physical activity scores. T(Ve) showed a nonsignificant decline in both men and women. Groupings of young-old (65-72 yr at follow-up) vs. old-old (73-90 yr at follow-up) were examined. In men, there were no differences in the rate of Vo(2 max) decline. The young-old women showed a significant decline in Vo(2 max), whereas old-old women, initially at a Vo(2 max) of 19.4 +/- 3.1 ml.kg(-1).min(-1), showed no loss in Vo(2 max). The longitudinal data, vs. cross-sectional analysis, showed a greater decline for men but similar estimates of the rates of change in women. Thus the 10-yr longitudinal study of the cohort of community-dwelling older adults who remained healthy, ambulatory, and independent showed a 14% decline in Vo(2 max) in men, and a smaller decline of 7% in women, with the oldest women showing little change over the 10-yr period.     

A single bout of exercise influences natural killer cells in elderly women, especially those who are habitually active

The purpose of our study was to examine the effects of a single exercise bout on the natural killer (NK) cell count and activity in physically active elderly people, sedentary elderly people, and sedentary young people. Eight elderly women who trained by walking (age, 64 +/- 1 years; Vo(2peak), 32.2 +/- 1.1 ml.kg(-1).min(-1)), 8 age-matched untrained women (63 +/- 1 years, 28.8 +/- 1.0 ml.kg(-1).min(-1)), and 8 young untrained women (25 +/- 1 years, 37.6 +/- 1.6 ml.kg(-1).min(-1)) were studied. Blood samples were taken before, immediately after, and 2 hours after a 30-minute bout of exercise at an intensity equivalent to 70-75% of Vo(2peak). Peripheral blood mononuclear cells were isolated and the NK cell count and activity were analyzed. The NK cell count of the elderly sedentary group immediately after exercise was significantly higher than those of the elderly women who walked and young sedentary women, whereas no significant interaction was detected in NK cell activity and NK cell activity per cell number among the 3 groups. Consequently, an intrinsic defect in the cytotoxic ability of NK cells appeared in sedentary elderly people but not in active elderly people who perform habitual exercise.     

The cardiorespiratory, anthropometric, and performance characteristics of an international/national touring ballet company

This study examined the cardiorespiratory and anthropometric indices of professional classical ballet dancers in relation to company seniority, gender, and supplemental training. Forty-nine participants from an international touring company carried out a peak Vo(2) test and vertical jump test. Anthropometric measurements and supplemental training activities were also recorded for each participant. Statistical analyses showed significant differences between gender and dancer seniority levels. Gender differences were seen for jump height (M = 52.7 +/- 7.12 cm; F = 37.6 +/- 5.32 cm) and peak Vo(2) (M = 49.32 +/- 3.72 ml.kg(-1).min(-1); F = 43.3 +/- 5.16 ml.kg(-1).min(-1)). Differences were also seen between dancer levels for peak Vo(2) (artist = 46.47 +/- 4.67 ml.kg(-1).min(-1); first artist = 42.72 +/- 5.81 ml.kg(-1).min(-1); soloist = 43.38 +/- 7.14 ml.kg(-1).min(-1); principal = 49.04 +/- 3.63 ml.kg(-1).min(-1)) and jump height (artist = 42.0 +/- 9.11 cm; first artist = 50.33 +/- 11.65 cm; soloist = 45.6 +/- 9.78 cm; principal = 44.67 +/- 9.53 cm). Pairwise post hoc comparisons showed that corps and principals had significantly greater relative peak Vo(2) than first artists and soloists (p < 0.05), while soloists and first artists had significantly greater jump heights compared to principals and corps (p < 0.05). Analysis of covariance modeling indicated that the self-reported mode of supplemental training had no association with relative peak Vo(2) or the percentage at which ventilatory threshold occurred. The present study has provided further insight into the cardiorespiratory profiles of classical ballet dancers, where soloists have significantly greater power capacities compared to principals and corps, who in turn had significantly greater aerobic power. These data can help guide strength and conditioning intervention strategies that need to take into account the nuances of the different seniority levels within a dance company.     

Effects of acetazolamide on aerobic exercise capacity and pulmonary hemodynamics at high altitudes.

Aerobic exercise capacity is decreased at altitude because of combined decreases in arterial oxygenation and in cardiac output. Hypoxic pulmonary vasoconstriction could limit cardiac output in hypoxia. We tested the hypothesis that acetazolamide could improve exercise capacity at altitude by an increased arterial oxygenation and an inhibition of hypoxic pulmonary vasoconstriction. Resting and exercise pulmonary artery pressure (Ppa) and flow (Q) (Doppler echocardiography) and exercise capacity (cardiopulmonary exercise test) were determined at sea level, 10 days after arrival on the Bolivian altiplano, at Huayna Potosi (4,700 m), and again after the intake of 250 mg acetazolamide vs. a placebo three times a day for 24 h. Acetazolamide and placebo were administered double-blind and in a random sequence. Altitude shifted Ppa/Q plots to higher pressures and decreased maximum O(2) consumption ((.)Vo(2max)). Acetazolamide had no effect on Ppa/Q plots but increased arterial O(2) saturation at rest from 84 +/- 5 to 90 +/- 3% (P < 0.05) and at exercise from 79 +/- 6 to 83 +/- 4% (P < 0.05), and O(2) consumption at the anaerobic threshold (V-slope method) from 21 +/- 5 to 25 +/- 5 ml.min(-1).kg(-1) (P < 0.01). However, acetazolamide did not affect (.)Vo(2max) (from 31 +/- 6 to 29 +/- 7 ml.kg(-1).min(-1)), and the maximum respiratory exchange ratio decreased from 1.2 +/- 0.06 to 1.05 +/- 0.03 (P < 0.001). We conclude that acetazolamide does not affect maximum exercise capacity or pulmonary hemodynamics at high altitudes. Associated changes in the respiratory exchange ratio may be due to altered CO(2) production kinetics.     

The relationship of the heart rate deflection point to the ventilatory threshold in trained cyclists

The purpose of this study was to assess the relationship of the heart rate deflection point (HRDP) to the ventilatory threshold (VT) in trained cyclists. Twenty-one endurance-trained cyclists (mean +/- SD: Vo(2)max = 67.6 +/- 4.7 ml x kg x min(-1)) completed a maximal cycle ergometer test of volitional fatigue using a ramped protocol. Ventilatory variables (Ve, Vo(2), Vco(2)) and power were measured online with averages reported every 20 seconds. Heart rate (HR) was recorded every 20 seconds using a Polar monitor. VT was calculated using the excess CO(2) elimination curve. The first derivative of a logistic growth curve fit to the HR-power data produced the HRDP. No significant differences (p > 0.01) existed between HR values at HRDP (171.7 +/- 9.6 b x min(-1)) and VT (169.8 +/- 9.9 b x min(-1)) or between Vo(2) values at HRDP (53.6 +/- 4.2 ml x kg x min(-1)) and VT (52.2 +/- 4.8 ml x kg x min(-1)). But power values at HRDP (318.7 +/- 30.7 W) were significantly different (p < 0.01) from those at VT (334.8 +/- 36.7 W). There were significant relationships between HRDP and VT for the physiological variables of HR (r = 0.92, p < 0.001), Vo(2) (r = 0.72, p < 0.001), and power (r = 0.77, p < 0.001). These findings indicate that HR and Vo(2) at HRDP are not significantly different from the values at VT in trained cyclists. HR values derived from HRDP may be used to set parameters for training intensity. Variability in the speed/power-HRDP relationship across detrained/trained states may be used to evaluate training programs.     

The metabolic cost of hatha yoga

To determine the metabolic and heart rate (HR) responses of hatha yoga, 26 women (19-40 years old) performed a 30-minute hatha yoga routine of supine lying, sitting, and standing asanas (i.e., postures). Subjects followed identical videotaped sequences of hatha yoga asanas. Mean physiological responses were compared to the physiological responses of resting in a chair and walking on a treadmill at 93.86 m.min(-1) [3.5 miles per hour (mph)]. During the 30-minute hatha yoga routine, mean absolute oxygen consumption (Vo(2)), relative Vo(2), percentage maximal oxygen consumption (%Vo(2)R), metabolic equivalents (METs), energy expenditure, HR, and percentage maximal heart rate (%MHR) were 0.45 L.min(-1), 7.59 ml.kg(-1).min(-1), 14.50%, 2.17 METs, 2.23 kcal.min(-1), 105.29 b.min(-1), and 56.89%, respectively. When compared to resting in a chair, hatha yoga required 114% greater O(2) (L.min(-1)), 111% greater O(2)(ml.kg(-1).min(-1)), 4,294% greater %Vo(2)R, 111% greater METs, 108% greater kcal.min(-1), 24% greater HR, and 24% greater %MHR. When compared to walking at 93.86 m.min(-1), hatha yoga required 54% lower O(2)(L.min(-1)), 53% lower O(2)(ml.kg(-1).min(-1)), 68% lower %Vo(2)R, 53% lower METs, 53% lower kcal.min(-1), 21% lower HR, and 21% lower %MHR. The hatha yoga routine in this study required 14.50% Vo(2)R, which can be considered a very light intensity and significantly lighter than 44.8% Vo(2)R for walking at 93.86 m.min(-1) (3.5 mph). The intensity of hatha yoga may be too low to provide a training stimulus for improving cardiovascular fitness. Although previous research suggests that hatha yoga is an acceptable form of physical activity for enhancing muscular fitness and flexibility, these data demonstrate that hatha yoga may have little, if any, cardiovascular benefit.     

Is running performance enhanced with creatine serum ingestion?

Runners Advantage (RA) creatine (Cr) serum has been marketed to increase running performance. To test this claim, cross-country runners completed baseline testing (BASE), an outdoor 5,000-m run followed by treadmill Vo(2)max testing on the same day. Subjects repeated testing after ingesting 5 ml of RA (n = 13) containing 2.5 g of Cr or placebo (n = 11). Heart rate (HR), rating of perceived exertion (RPE), and run time were recorded. With RA (56.48 +/- 8.93 ml.kg(-1.)min(-1)), Vo(2)max was higher (p = 0.01) vs. BASE (54.07 +/- 9.36 ml.kg(-1.)min(-1)), yet the magnitude of the increase was within the coefficient of variation of Vo(2)max. No effect of RA on maximal HR was exhibited, yet Vco(2)max and duration of incremental exercise were significantly higher (p < 0.025) vs. BASE. Vo(2)max was similar in PL (58.85 +/- 6.67 ml.kg(-1).min(-1)) and BASE (57.28 +/- 7.22 ml.kg(-1.)min(-1)). With RA, the 5,000-m time was unchanged, and RPE was lower (p < 0.025) vs. BASE. These data do not support the ergogenic claims of RA in its current form and dose.     

Human lung density is not altered following normoxic and hypoxic moderate-intensity exercise: implications for transient edema.

The purpose of this study was to examine the effects of exercise on extravascular lung water as it may relate to pulmonary gas exchange. Ten male humans underwent measures of maximal oxygen uptake (Vo2 max) in two conditions: normoxia (N) and normobaric hypoxia of 15% O2 (H). Lung density was measured by quantified MRI before and 48.0 +/- 7.4 and 100.7 +/- 15.1 min following 60 min of cycling exercise in N (intensity = 61.6 +/- 9.5% Vo2 max) and 55.5 +/- 9.8 and 104.3 +/- 9.1 min following 60 min cycling exercise in H (intensity = 65.4 +/- 7.1% hypoxic Vo2 max), where Vo2 max = 65.0 +/- 7.5 ml x kg(-1) x min(-1) (N) and 54.1 +/- 7.0 ml x kg(-1) x min(-1) (H). Two subjects demonstrated mild exercise-induced arterial hypoxemia (EIAH) [minimum arterial oxygen saturation (SaO2 min) = 94.5% and 93.8%], and seven subjects demonstrated moderate EIAH (SaO2 min = 91.4 +/- 1.1%) as measured noninvasively during the Vo2 max test in N. Mean lung densities, measured once preexercise and twice postexercise, were 0.177 +/- 0.019, 0.181 +/- 0.019, and 0.173 +/- 0.019 g/ml (N) and 0.178 +/- 0.021, 0.174 +/- 0.022, and 0.176 +/- 0.019 g/ml (H), respectively. No significant differences (P > 0.05) were found in lung density following exercise in either condition or between conditions. Transient interstitial pulmonary edema did not occur following sustained steady-state cycling exercise in N or H, indicating that transient edema does not result from pulmonary capillary leakage during sustained submaximal exercise.     

Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.

We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O(2) uptake (Vo(2)) slow component during heavy-cycle exercise. Ten subjects (mean +/- SD, age 26 +/- 4 yr, body mass 71.5 +/- 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peak Vo(2), and the baseline power output was adjusted to account for differences in the O(2) cost of unloaded pedaling. The gain of the Vo(2) primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean +/- SE, 10.6 +/- 0.3, 9.5 +/- 0.2, and 8.9 +/- 0.4 ml. min(-1). W(-1), respectively; P < 0.05). The amplitude of the Vo(2) slow component was significantly greater at 115 rpm (328 +/- 29 ml/min) compared with 35 rpm (109 +/- 30 ml/min) and 75 rpm (202 +/- 38 ml/min) (P < 0.05). There were no significant differences in the time constants or time delays associated with the primary and slow components across the pedal rates. The change in blood lactate concentration was significantly greater at 115 rpm (3.7 +/- 0.2 mM) and 75 rpm (2.8 +/- 0.3 mM) compared with 35 rpm (1.7 +/- 0.4 mM) (P < 0.05). These data indicate that pedal rate influences Vo(2) kinetics during heavy exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.     

Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure.

To investigate the effect of altitude exposure on running economy (RE), 22 elite distance runners [maximal O(2) consumption (Vo(2)) 72.8 +/- 4.4 ml x kg(-1) x min(-1); training volume 128 +/- 27 km/wk], who were homogenous for maximal Vo(2) and training, were assigned to one of three groups: live high (simulated altitude of 2,000-3,100 m)-train low (LHTL; natural altitude of 600 m), live moderate-train moderate (LMTM; natural altitude of 1,500-2,000 m), or live low-train low (LLTL; natural altitude of 600 m) for a period of 20 days. RE was assessed during three submaximal treadmill runs at 14, 16, and 18 km/h before and at the completion of each intervention. Vo(2), minute ventilation (Ve), respiratory exchange ratio, heart rate, and blood lactate concentration were determined during the final 60 s of each run, whereas hemoglobin mass (Hb(mass)) was measured on a separate occasion. All testing was performed under normoxic conditions at approximately 600 m. Vo(2) (l/min) averaged across the three submaximal running speeds was 3.3% lower (P = 0.005) after LHTL compared with either LMTM or LLTL. Ve, respiratory exchange ratio, heart rate, and Hb(mass) were not significantly different after the three interventions. There was no evidence of an increase in lactate concentration after the LHTL intervention, suggesting that the lower aerobic cost of running was not attributable to an increased anaerobic energy contribution. Furthermore, the improved RE could not be explained by a decrease in Ve or by preferential use of carbohydrate as a metabolic substrate, nor was it related to any change in Hb(mass). We conclude that 20 days of LHTL at simulated altitude improved the RE of elite distance runners.     

Ascorbic acid does not affect the age-associated reduction in maximal cardiac output and oxygen consumption in healthy adults.

Maximal aerobic capacity (Vo(2max)) decreases progressively with age, primarily because of a reduction in maximal cardiac output (Q(max)). This age-associated decline in Vo(2max) may be partially mediated by the development of oxidative stress that can suppress beta-adrenergic-receptor responsiveness and, consequently, reduce Q(max). To test this hypothesis, Vo(2max) (indirect calorimetry) and Q(max) (open-circuit acetylene breathing) were determined in 12 young (23 +/- 1 yr, mean +/- SE) and 10 older (61 +/- 1 yr) adults following systemic infusion of either saline (control) and/or the powerful antioxidant ascorbic acid (acute: bolus 0.06; drip 0.02 g/kg fat-free mass) and following chronic 30-day oral administration of ascorbic acid (500 mg/day). Plasma ascorbic acid concentration was not different between young and older adults and was increased similarly, independent of age [change (Delta) acute = 1,055 +/- 117%; Delta chronic = 62 +/- 19%]. Oxidized low-density lipoprotein concentration was greater (P < 0.001) in older (57 +/- 5 U/l) compared with young (34 +/- 3 U/l) adults and was reduced in both groups (P < 0.02) following acute (Delta = -6 +/- 2%) but not chronic (P = 0.18) ascorbic acid administration. Control (baseline) Vo(2max) and Q(max) were positively related (r = 0.76, P < 0.001) and were lower (P < 0.05) in older (34 +/- 2 ml.kg(-1).min(-1); 16.1 +/- 1.1 l/min) compared with young (43 +/- 3 ml.kg(-1).min(-1); 20.2 +/- 0.9 l/min) adults. Following ascorbic acid administration, neither Vo(2max) (young acute = 41 +/- 2; young chronic = 42 +/- 2; older acute = 34 +/- 2; older chronic = 34 +/- 2 ml.kg(-1).min(-1)) nor Q(max) (young acute = 20.1 +/- 0.9; young chronic = 19.1 +/- 0.8; older acute = 16.2 +/- 1.1; older chronic = 16.6 +/- 1.4 l/min) was changed. These data suggest that ascorbic acid administration does not affect the age-associated reduction in Q(max) and Vo(2max).     

Effects of rate of decrease in power output in decrement-load exercise on oxygen uptake

The purpose of this study was to examine how oxygen uptake (Vo2) in decrement-load exercise (DLE) is affected by changing rate of decrease in power output. DLE was performed at three different rates of decrease in power output (10, 20 and 30 watts.min(-1): DLE10, DLE20 and DLE30, respectively) from power output corresponding to 90 % of peak Vo2. Vo2 exponentially increased and then decreased, and the rate of its decrease was reduced at low power output. The values of Vo2 in the three DLE tests were not different for the first 2 min despite the difference in power output. The relationship between Vo2 and power output below 50 watts was obtained as a slope to estimate excessive Vo2 (ex-Vo2) above 50 watts. The slopes were 10.0+/-0.9 for DLE10, 9.9+/-0.7 for DLE20 and 10.2+/-1.0 ml.min(-1).watt(-1) for DLE30. The difference between Vo2 estimated from the slope and measured Vo2 was defined as ex-Vo2. The peak value of ex-Vo2 for DLE10 (189+/-116 ml.min(-1)) was significantly greater than those for DLE20 and for DLE30 (93+/-97 and 88+/-34 ml.min(-1)). The difference between Vo2 in DLE and that in incremental-load exercise (ILE) below 50 watts (DeltaVo2) was greater in DLE30 and smallest in DLE10. There were significant differences in DeltaVo2 among the three DLE tests. The values of DeltaVo2 at 30 watts were 283+/-152 for DLE10, 413+/-136 for DLE20 and 483+/-187 ml.min(-1) for DLE30. Thus, a faster rate of decrease in power output resulted in no change of Vo2 at the onset of DLE, smaller ex-Vo2 and greater DeltaVo2. These results suggest that Vo2 is disposed in parallel in each motor unit released from power output or recruited in DLE.     

The energy expenditure of snowshoeing in packed vs. unpacked snow at low-level walking speeds

Snowshoeing is currently ranked as one of the top 20 participatory sports in the United States, and the number of participants almost tripled, from 440,000 to 1.2 million in 1998. Despite this large increase in participation, no scientific evidence exists to quantify any physiologic response to the activity. Therefore, the purpose of this investigation was to assess the energy expenditure of snowshoeing at selected low-level speeds and evaluate its acceptability as a form of aerobic conditioning exercise. Ten habitually active subjects (7 men, 3 women, mean age = 24 +/- 3.9 years, mass = 76.6 +/- 14.5 kg, height = 173.7 +/- 9.6 cm) were recruited. Steady state heart rate data were determined from 2 treadmill tests at 4 and 6 mph. Steady state heart rates at 4 mph and 6 mph from treadmill speeds were then reproduced outdoors under 2 snow conditions, packed, and unpacked snow, while caloric expenditure and speed were determined. Expired gases were collected in Douglas bags for both snowshoe and treadmill trials and then analyzed and corrected indoors for the fractional concentrations of carbon dioxide and oxygen. Data analyses indicate that caloric expenditure during snowshoeing may be considerably higher than previously reported. Snowshoeing on packed snow at 2.95 mph elicited a similar heart rate and energy expenditure response as walking on a treadmill at 4 mph or snowshoeing in unpacked snow at 2.04 mph (Vo(2) = 18.18 +/- 0.8 ml x kg(-1) x min(-1)). Snowshoeing on packed snow at 3.97 mph elicited the same heart rate and energy expenditure response as walking on a treadmill at 6 mph or snowshoeing on unpacked snow at 2.87 mph (Vo(2) = 36.72 +/- 0.8 ml x kg(-1) x min(-1)). Furthermore, increasing walking speed on snow by just 1 mph at slow speeds (2 and 3 mph) resulted in approximately twice the energy expenditure. Our data indicate that current estimates of energy expenditure while snowshoeing underestimate by greater than 50%. Apparently the energy expenditure during snowshoeing is much higher than previously considered and varies considerably because of snow terrain. Furthermore, energy expenditure levels similar to walking can be achieved on snowshoes at much slower speeds. This study represents an original investigation into energy expenditure during snowshoeing.     

Metabolism and thermoregulation during fasting in king penguins, Aptenodytes patagonicus, in air and water

We measured oxygen consumption rate (Vo(2)) and body temperatures in 10 king penguins in air and water. Vo(2) was measured during rest and at submaximal and maximal exercise before (fed) and after (fasted) an average fasting duration of 14.4 +/- 2.3 days (mean +/- 1 SD, range 10-19 days) in air and water. Concurrently, we measured subcutaneous temperature and temperature of the upper (heart and liver), middle (stomach) and lower (intestine) abdomen. The mean body mass (M(b)) was 13.8 +/- 1.2 kg in fed and 11.0 +/- 0.6 kg in fasted birds. After fasting, resting Vo(2) was 93% higher in water than in air (air: 86.9 +/- 8.8 ml/min; water: 167.3 +/- 36.7 ml/min, P < 0.01), while there was no difference in resting Vo(2) between air and water in fed animals (air: 117.1 +/- 20.0 ml O(2)/min; water: 114.8 +/- 32.7 ml O(2)/min, P > 0.6). In air, Vo(2) decreased with M(b), while it increased with M(b) in water. Body temperature did not change with fasting in air, whereas in water, there were complex changes in the peripheral body temperatures. These latter changes may, therefore, be indicative of a loss in body insulation and of variations in peripheral perfusion. Four animals were given a single meal after fasting and the temperature changes were partly reversed 24 h after refeeding in all body regions except the subcutaneous, indicating a rapid reversal to a prefasting state where body heat loss is minimal. The data emphasize the importance in considering nutritional status when studying king penguins and that the fasting-related physiological changes diverge in air and water.     

Negative metabolic and coronary flow effects of decreases in cAMP and increases in cGMP in control and renal hypertensive rabbit hearts.

The interaction during stimulation of cGMP and inhibition of cAMP was investigated in control and renal hypertensive hearts. Control and hypertensive [1 kidney, 1 clip (1K1C)] rabbits were used. The anesthetized open-chest groups were vehicle, 8-bromo-cGMP (8-Br-cGMP; 10(-3)M), propranolol (Prop; 2 mg/kg), and Prop + 8-Br-cGMP. O(2) consumption levels (Vo(2)) in the subepicardium (Epi) and subendocardium (Endo) were determined from coronary flow (microspheres) and O(2) extraction (microspectrophotometry). Wall thickening and cAMP levels were also determined. In control, no significant change in Vo(2) was seen for the 8-Br-cGMP group, but Vo(2) was decreased from Epi (9.7 +/- 1.5 ml O(2) x min(-1) x 100 g(-1)) and Endo (10.5 +/- 0.4 ml O(2) x min(-1) x 100 g(-1)) to 6.8 +/- 0.6/7.8 +/- 0.5 ml O(2) x min(-1) x 100 g(-1) in the control Prop group. Control Prop + 8-Br-cGMP did not cause a further fall in Vo(2) but lowered Endo flow. In 1K1C, Vo(2) decreased from Epi/Endo (10.8 +/- 1.3/11 +/- 1.0 ml O(2).min(-1).100 g(-1)) to 7.8 +/- 1.1/8.7 +/- 0.5 ml O(2) x min(-1) x 100 g(-1) in the 1K1C 8-Br-cGMP group and to 7 +/- 0.5/8.1 +/- 0.5 ml O(2) x min(-1) x 100 g(-1) in the 1K1C Prop group. 1K1C Prop + 8-Br-cGMP did not cause a further fall in Vo(2) but lowered blood flow. No significant changes in cAMP levels were present with 8-Br-cGMP in control or 1K1C rabbits, but significant decreases were seen with Prop in both control and 1K1C rabbits. No further change was seen in Prop + 8-Br-cGMP for either control or 1K1C. Thus the negative metabolic effect of stimulating cGMP was seen only in the hypertensive rabbit heart. The negative metabolic effect of inhibiting cAMP was seen in both the control and the hypertensive rabbit heart. However, the negative metabolic effects of cGMP and cAMP were nonadditive.     

Augmented hypoxic ventilatory response in men at altitude.

To test the hypothesis that the hypoxic ventilatory response (HVR) of an individual is a constant unaffected by acclimatization, isocapnic 5-min step HVR, as delta VI/delta SaO2 (l.min-1.%-1, where VI is inspired ventilation and SaO2 is arterial O2 saturation), was tested in six normal males at sea level (SL), after 1-5 days at 3,810-m altitude (AL1-3), and three times over 1 wk after altitude exposure (PAL1-3). Equal medullary central ventilatory drive was sought at both altitudes by testing HVR after greater than 15 min of hyperoxia to eliminate possible ambient hypoxic ventilatory depression (HVD), choosing for isocapnia a P'CO2 (end tidal) elevated sufficiently to drive hyperoxic VI to 140 ml.kg-1.min-1. Mean P'CO2 was 45.4 +/- 1.7 Torr at SL and 33.3 +/- 1.8 Torr on AL3, compared with the respective resting control end-tidal PCO2 of 42.3 +/- 2.0 and 30.8 +/- 2.6 Torr. SL HVR of 0.91 +/- 0.38 was unchanged on AL1 (30 +/- 18 h) at 1.04 +/- 0.37 but rose (P less than 0.05) to 1.27 +/- 0.57 on AL2 (3.2 +/- 0.8 days) and 1.46 +/- 0.59 on AL3 (4.8 +/- 0.4 days) and remained high on PAL1 at 1.44 +/- 0.54 and PAL2 at 1.37 +/- 0.78 but not on PAL3 (days 4-7). HVR was independent of test SaO2 (range 60-90%). Hyperoxic HCVR (CO2 response) was increased on AL3 and PAL1. Arterial pH at congruent to 65% SaO2 was 7.378 +/- 0.019 at SL, 7.44 +/- 0.018 on AL2, and 7.412 +/- 0.023 on AL3.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of nightly normobaric hypoxia and high intensity training under intermittent normobaric hypoxia on running economy and hemoglobin mass.

We investigated the effects of nightly intermittent exposure to hypoxia and of training during intermittent hypoxia on both erythropoiesis and running economy (RE), which is indicated by the oxygen cost during running at submaximal speeds. Twenty-five college long- and middle- distance runners [maximal oxygen uptake (Vo(2max)) 60.3 +/- 4.7 ml x kg(-1) x min(-1)] were randomly assigned to one of three groups: hypoxic residential group (HypR, 11 h/night at 3,000 m simulated altitude), hypoxic training group (HypT), or control group (Con), for an intervention of 29 nights. All subjects trained in Tokyo (altitude of 60 m) but HypT had additional high-intensity treadmill running for 30 min at 3,000 m simulated altitude on 12 days during the night intervention. Vo(2) was measured at standing rest during four submaximal speeds (12, 14, 16, and 18 km/h) and during a maximal stage to volitional exhaustion on a treadmill. Total hemoglobin mass (THb) was measured by carbon monoxide rebreathing. There were no significant changes in Vo(2max), THb, and the time to exhaustion in all three groups after the intervention. Nevertheless, HypR showed approximately 5% improvement of RE in normoxia (P < 0.01) after the intervention, reflected by reduced Vo(2) at 18 km/h and the decreased regression slope fitted to Vo(2) measured during rest position and the four submaximal speeds (P < 0.05), whereas no significant corresponding changes were found in HypT and Con. We concluded that our dose of intermittent hypoxia (3,000 m for approximately 11 h/night for 29 nights) was insufficient to enhance erythropoiesis or Vo(2max), but improved the RE at race speed of college runners.     

Measurement of maximum oxygen consumption in Guinea fowl Numida meleagris indicates that birds and mammals display a similar diversity of aerobic scopes during running

Judgement of exercise performance in birds has been hampered by a paucity of data on maximal aerobic capacity. We measured the maximal rate of oxygen consumption (Vo2,max) in running guinea fowl Numida meleagris, a bird that has been used in several previous studies of avian running. Mean Vo2,max during level treadmill running was 97.5+/-3.7 mL O(2) kg(-1) min(-1) (mean+/-SEM, N=5). Vo2,max was on average 6% higher when the birds ran uphill compared with the value during level running (paired t-test, P=0.041, N=5). The mean basal rate of oxygen consumption (Vo2,bmr) of the same individuals was 7.9+/-0.5 mL O(2) kg(-1) min(-1). Mean factorial aerobic scope based on individually measured values of Vo2,max and Vo2,bmr was 13.2+/-0.6 (mean+/-SEM, N=5). This value was considerably lower than the factorial aerobic scope previously measured during running in Rhea americana, a large flightless ratite. The difference in factorial scope between these two running birds likely reflects the effects of body size as well as size-independent differences in the ability to deliver and use oxygen. These data confirm a previous prediction that birds have a diversity of factorial aerobic scopes similar to that exhibited by mammals.     

Physical fitness profile of Army ROTC cadets

One role of Army Reserved Officer's Training Corps (ROTC) programs is to physically prepare cadets for the demands of a military career. Cadets participate in physical training 3 days per week as part of their military science curriculum. Limited research has been conducted on the fitness level of ROTC cadets; therefore, the purpose of this study was to profile the physical fitness status of a cadre of ROTC cadets. Forty-three cadets (30 men and 13 women) performed Army Physical Fitness Test (APFT) assessments (2-mile run, 2-minute maximum push-ups and sit-ups) and clinical assessments of fitness (Bruce protocol Vo(2)max, underwater weighing, and 1 repetition maximum [1RM] bench press tests). Mean +/- standard deviations were calculated to provide the physical fitness profile for each parameter. Male cadets (21 +/- 2.2 years; height 177.4 +/- 6.6 cm; mass 79.2 +/- 9.4 kg) scored 49.6 +/- 6.1 ml.kg(-1).min(-1) for Vo(2)max, 14.8 +/- 4.2% fat, 86.5 +/- 24.9 kg 1RM bench press, 2-mile run of 13.97 +/- 1.4 minutes, 70.5 +/- 12.8 sit-ups, and 60.2 +/- 13.2 push-ups. Female cadets (20 +/- 2.4 years; height 165.1 +/- 8.0 cm; mass 63.5 +/- 10.0 kg) scored 40.8 +/- 3.9 ml.kg(-1).min(-1) for Vo(2) max, 23.9 +/- 3.8% fat, 35.3 +/- 8.2 kg 1RM bench press, 2-mile run of 17.0 +/- 1.6 minutes, 65.0 +/- 12.9 sit-ups, and 33.3 +/- 11.2 push-ups. The mean scores were above the 83rd percentile on all APFT items and average (percent fat) to above average (Vo(2)max and men's bench press scores) when compared with peer-age and sex-corrected norms. Only the women's bench press score was below average. With the exception of the women's bench press, these ROTC cadets possessed average to above average levels of fitness.