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The purpose of this investigation was to determine the effect of physostigmine (Phy) and/or concurrent exercise on lactate, pyruvate, and L/P ratio in plasma, skeletal muscle, and brain tissue in male Sprague-Dawley rats. The Phy-dosed (Phy-D) and Phy-dosed + concurrent acute exercise (Phy-D + CAE) groups elicited significantly higher L/P ratios in plasma compared to the acutely exercised (AE) group at 30 min postexercise. Physostigmine dosing, with or without exercise, resulted in significantly lower muscle pyruvate levels, from 30 to 50 min postdrug administration, in Phy-D and Phy-D + CAE groups compared to the AE group. In the brain, lactate values were significantly elevated in the acutely exercised groups at 5 min postexercise with or without Phy dosing. However, at 15 to 30 min postexercise, lactate values were significantly elevated in the Phy-D + CAE compared to the AE group. These data suggest that when Phy is administered prior to a 20-min moderately intensive exercise bout, there is an accumulation of lactate for a prolonged period of time in recovery.

The purpose of this study was to determine the effect of low, moderate and high wet bulb globe temperatures (Twbg) on cardiovascular variables and ratings of perceived exertion (RPE) during moderately prolonged, high-intensity exercise. Six subjects [four men and two women; mean (SD) age, 22.0 (1.2) years; maximum oxygen consumption (VO2peak), 51.0 (8.4) ml.kg-1.min-1] completed 30 min of exercise (80% VO2peak) on a cycle ergometer at low [14.7 (2.1) degrees C], moderate [21.0 (1.5) degrees C], and high [27.4 (2.3) degrees C] Twbg. Two additional subjects completed 20 min of exercise in the high temperature condition, but completed 30 min in the moderate and low Twbg. Heart rate (fc), blood pressure, blood lactate (La), mean skin temperature (Tsk), VO2, and RPE were measured at 10, 20 and 30 min. Results showed that fc, rate pressure product, RPE, pulmonary ventilation and ventilatory equivalent for oxygen increased (P < 0.05) across time for all conditions, while P(a) decreased across time. Tsk and fc were significantly greater across time in the high condition [35.9 (0.65) degrees C; 176 (12.6) beats.min-1] compared to the moderate [34.6 (1.5) degrees C; 170 (17.2) beats.min-1] and the low condition [31.7 (1.5) degrees C; 164 (17.1) beats.min-1]. However, there were no differences throughout exercise in RPE [high, 16.2 (2.0); moderate, 16.4 (2.2); low, 16.3 (1.9)] and VO2 across the conditions. These data suggest that RPE is closely related to metabolic intensity but is not a valid indicator of cardiovascular strain during exercise in high Twbg conditions.

The purpose of this investigation was to examine the accuracy of an exercise intensity prescription based upon perceptual responses obtained during a graded exercise test. Fifteen physically active men completed a graded exercise test (GXT) on a motor driven treadmill. Heart rate (HR), oxygen uptake (VO2), and RPE were measured each minute. An RPE intensity prescription was calculated as 75% of heart rate reserve from the GXT heart rate and RPE data. A minimum of 48 h later the subjects completed 10 min of exercise (EXT) on a level treadmill at the prescribed RPE. The subjects set the treadmill speed to elicit an exercise intensity equal to the prescribed perception of effort. There were significant mean differences (P < 0.05) in heart rate between the GXT (161.8 +/- 1.3) and EXT (154.9 +/- 4.5). However, by minute 6 the subjects were within four beats.min-1 of the target heart rate. There were no significant differences (P > 0.05) between GXT and EXT for VO2 (36.1 +/- 5.2, 33.1 +/- 6.4) and VE (64.1 +/- 10.8, 58.4 +/- 13.5) respectively. The present investigation demonstrates that a subject's perceptual response to a GXT can be used to accurately prescribe exercise intensity during level treadmill running. The intensity selected was within a typical range used for exercise prescription. The advantage of RPE as a method of exercise prescription is that an individual does not need to stop during exercise and measure a heart rate, but can make pace adjustments while exercising based solely upon the perception of effort.

Young (147 +/- 2 g) and adult (322 +/- 7 g) male Sprague Dawley rats were subjected to an incremental treadmill protocol and assessed via the Oxyscan Metabolic System in order to determine if differences exist relative to oxygen consumption (VO2, expressed in ml/kg/min), respiratory exchange ratio (RER) and caloric expenditure of two different age groups. The young rats attained a higher VO2 (81.55 +/- 1.22) compared to adult rats (68.97 +/- 2.05) at a maximal level of exercise. The adult rats became dependent upon carbohydrates as the primary source of energy until reaching 52% VO2 max, whereas the young rats did not resort to carbohydrate utilization as a primary fuel source until reaching 87% VO2max. At peak exercise, the adult animals burned only 15% less kcal/kg/h than the young rats, but the adult rats burned 37% more carbohydrate than the young animals. These data suggest that as exercise intensity increases, younger rats can more readily maintain a higher level of oxygen consumption accompanied by a more efficient use of fat as an energy source compared to adult rats. The clinical implication of this finding suggests that during the growth and development years of life, fat plays a significant role in energy expenditure needs and may therefore be more important than currently believed in young children's nutritional intake.

The purpose of this study was to compare the physiological and biomechanical responses of wheelchair-dependent persons (WCD) to able-bodied persons (AB) during manual wheelchair ergometry. Five WCD and five AB performed a discontinuous wheelchair ergometer test starting at 12.8 W at 30 rev.min-1 (57 m.min-1) with increments of 7.0 W at 6-min intervals. Biomechanical data were collected 3.5 min into each stage followed by the collection of physiological data. After the fifth stage, peak oxygen consumption was determined by having the subject work against a resistance of 14.7-19.6 N at 30 rev.min-1. The WCD had significantly higher net mechanical efficiency at 26.7, 33.6 and 40.6 W in comparison to the AB. The WCD had significantly greater shoulder extension at the point of initial wheel contact as measured by the shoulder angle, while the AB had significantly greater shoulder range of motion at all work rates in comparison to the WCD. The results demonstrate that a significant physiological difference exists in the manner by which WCD and AB accomplish wheelchair ergometry. The biomechanical differences between AB and WCD were found to be a prominent factor contributing to the higher mechanical efficiency of WCD over AB. It was concluded that basic physiological and biomechanical differences exist between WCD and AB in manual wheelchair locomotion and that these differences are important considerations to the interpretation of data in wheelchair ergometry studies.

The effects of obesity, exercise, and the interaction of obesity and exercise were examined in 6 caffeine naive, untrained, nonsmoking, college males (3 lean (LV), 3 obese (OV]. Each subject received caffeine (oral, 5.83 mg X kg-1 lean body weight) or placebo (50 mg citrate) prior to 3 h of seated rest and prior to 90 min of treadmill walking (40% of their maximal aerobic power) followed by 90 min of seated recovery. Serum samples were collected at various times and analyzed for caffeine by HPLC. Pharmacokinetic analysis indicated that at rest, OV had a significantly higher absorption rate constant (Ka 0.0757 vs. 0.0397 min-1), lower elimination rate constant (Ke 0.0027 vs. 0.0045 min-1), and longer serum half-life (t1/2 4.37 vs. 2.59 h) in comparison to LV. In exercise, as well as at rest LV and OV had a large difference in the volume of distribution (43.2 vs. 101.1) (rest, 54.1 vs. 103.1). Exercise consistently resulted in a decrease in the maximal serum concentration of caffeine and the area under the curve in OV while having no consistent effect on LV. The interactive effects of obesity and exercise could not be dissociated. However, these results demonstrate that both obesity and exercise have modified the pharmacokinetics of caffeine.

We investigated relationships of peak VO2 and percent body fat with postexercise plasma free fatty acid (FFA) and glycerol concentrations in 14 men using multiple-regression techniques. During 1 h of walking (36% of peak VO2), no significant differences in plasma-FFA response were attributed to either peak VO2 or percent body fat. However, individuals with higher peak VO2S tended to have greater elevations in plasma-glycerol concentration during exercise (p = 0.074). They also had greater peak FFA concentrations and FFA X glycerol(-1)-molar ratios immediately after exercise and faster subsequent clearing of excess FFA from the blood (p less than 0.05). Percent fat was not related to postexercise plasma glycerol, FFA, FFA X glycerol-1 responses. Differing postexercise FFA responses, as related to peak VO2, were due, not to varying rates of lipolysis but rather to different rates of FFA mobilization and utilization.

The purpose of this study was to determine the effects of long term use of a manual wheelchair by wheelchair-confined women (means = 14.6 years) on physiological responses to wheelchair ergometry. Six experimental subjects were compared to six able bodied women during maximal exercise as well as submaximal wheelchair ergometry at 50 and 80% of peak VO2. The wheelchair dependent women achieved higher power outputs, greater efficiency at the higher submaximal workload, less metabolic acidosis during submaximal exercise as well as less ventilatory stress. There was no significant difference in peak VO2 between the two groups of women. Because these were not athletically trained women, it was concluded that the long term use of a manual wheelchair leads to physiological adaptations favourable to the daily requirements of wheelchair locomotion.

The purpose of this investigation was to determine test-retest reliability for measuring maximal values of alactic capacity (ALCmax) and alactic power (ALPmax). For this, 31 men and 13 women each completed two ALCmax and ALPmax tests. Test-retest correlation coefficients for ALCmax and ALPmax values were 0.78 and 0.90, respectively. In addition, for both variables no significant differences were found between test no. 1 and test no. 2. Mean ALCmax values of 429 and 317 J . kg-1, as well as mean ALPmax values of 3.79 and 3.08 W . kg-1 were found for the men and women, respectively. Both ALCmax and ALPmax values were lower (p less than 0.05) for women than men. However, for the capacity power ratio (ALCmax . ALPmax-1) no difference was found between men and women. A correlation coefficient of r = 0.61 was found between mean values for ALCmax and ALPmax . ALCmax values were discussed as being related to skeletal muscle phosphagen concentrations, and ALPmax values were discussed as being related to phosphagen splitting rate. The observed sex differences were suggested to reflect a greater percent body fat in women than men.

The purpose of this study was to compare metabolic and cardiopulmonary responses for submaximal and maximal exercise performed several days preceding (pre-test) and 45 min after (post-test) 21 miles of high intensity (70% VO2 max) treadmill running. Seven aerobically trained subjects' oxygen uptake, oxygen pulse, respiratory exchange ratio, heart rate, pulmonary ventilation, ventilatory equivalent of oxygen, and blood lactate concentration were determined for exercise during the pre- and post-test sessions. No differences were found for submaximal oxygen uptake, oxygen pulse, pulmonary ventilation and ventilatory equivalent of oxygen between the pre- and post-test values. Generally, submaximal heart rate responses were higher, and respiratory exchange ratio values were lower during the post-test. Reductions of maximal work time (12%), maximal oxygen uptake (6%) and maximal blood lactate concentration (47%) were found during the post-test. Thermal stress and glycogen depletion are possible mechanisms which may be responsible for these observed differences.

Seven untrained male subjects were studied for the effects of mild warm-up on oxygen uptake and lactic acid production. Each subject completed two standardized workloads on a bicycle ergometer requiring 75% of their physical work capacity. Protocols of the two tests consisted of either no warm-up or a 4-min warm-up preceding a 5-min exercise at approximately 80% of their maximal oxygen uptake. The contrasting protocols did not reveal any significant differences between heart rate, lactic acid, and oxygen uptake. The dominant influence on the metabolic processes was the absolute workload of the tasks and not the presence or absence of preliminary related activity. It was concluded that an untrained individual lacks the cardiovascular and cellular adaptations necessary to demonstrate metabolic benefits from warm-up.

Toeclips secure the feet to bicycle pedals and are thought to enable greater anticipation of leg musculature in the pedaling motion. To determine the effects of toeclip use on metabolic and cardiopulmonary responses to BERG exercise, 13 female subjects, who had no prior experience with the devices, performed maximal and submaximal work with and without the use of toeclips. Similar oxygen uptake (V02), physical work capacity, pulmonary ventilation (VE), respiratory exchange ratio (R), heart rate (HR), and blood lactate concentration (LA) were found for maximal effort exercise under both conditions. For submaximal exercise (at 30, 60, and 80% maximal V02) performed with and without toeclips, no differences were found for V02, VE, R, HR, LA, cardiac output, stroke volume, and arteriovenous oxygen difference. These data suggest that toeclip use during BERG exercise may not alter metabolic and cardiopulmonary responses of individuals who have no prior experience with the devices.