Search

This review addresses issues related to substrate metabolism in children and how this information compares and contrasts to that of adults. The relative percent of fat and carbohydrate (CHO) utilized by an individual can be estimated from respiratory exchange ratio (RER) values between 0.7 (100% fat, 0% CHO) and 1.0 (100% CHO, 0% fat). The rise in RER towards 1.0 in relation to increased exercise intensity demonstrates the augmented role of CHO as an energy source for muscle; however, fat oxidation also represents a major source of energy during exercise of moderate-to-heavy intensity. Preliminary reports suggest that children demonstrate patterns of fat and CHO use in response to exercise intensity similar to those of adults and also show a reduction in RER at submaximal exercise intensities after training. The use of the 'crossover concept' may simplify the presentation of how metabolism is affected by exercise intensity and training. [ABSTRACT FROM AUTHOR]

Objectives. The objectives of the present study were (1) to evaluate the pressor response to an isometric handgrip exercise in normotensive black and white males; (2) to measure plasma catecholamine levels pre- and post-exercise, as an index of sympathetic nervous system activity; and (3) to quantify the pressor response to bolus intravenous injections of phenylephrine (an alpha-specific agonist). Methods. Cardiovascular and catecholamine responses to an isometric handgrip exercise (3 minutes at 30% MVC) were measured in 15 normotensive blacks and whites. In another phase of the study, pressor responses to bolus injections of phenylephrine were assessed to evaluate alpha-adrenergic sensitivity. Results. The blood pressure in the blacks increased from 119/69 to 160/120 mm HG during isometric exercise, while in the whites it increased from 118/67 to 153/110 mm HG. The blacks exhibited a greater diastolic blood pressure reactivity, as evidenced by a significant race x time interaction (p < 0.05). The heart rate responses were not significantly different between the two groups. The plasma levels of norepinephrine were similar at rest, but were 25% lower in the blacks than in the whites following isometric exercise (p < 0.01). Black subjects also demonstrated an increased pressor response to intravenous injections of phenylephrine at rest (p < 0.05). Conclusions. The enhanced vascular sensitivity to norepinephrine may have contributed to the greater exercise pressor response in the blacks. [ABSTRACT FROM AUTHOR]

Editor-in-Chief Edward T. Howley, Ph.D., FACSM, highlights the content of this issue and thanks associate editors, authors, and reviewers. [ABSTRACT FROM AUTHOR]

Editor-in-Chief Ed Howley thanks the year's most outstanding contributors to the Journal and gives an overview of 2007 health/fitness trends. [ABSTRACT FROM AUTHOR]

Purpose: To compare the classic physiological variables linked to endurance performance (VO2max, %VO2max at lactate threshold (LT), and running economy (RE)) with peak treadmill velocity (PTV) as predictors of performance in a 16-km time trial., Methods: Seventeen healthy, well-trained distance runners (10 males and 7 females) underwent laboratory testing to determine maximal oxygen uptake (VO2max), RE, percentage of maximal oxygen uptake at the LT (%VO2max at LT), running velocity at LT, and PTV. Velocity at VO2max (vVO2max) was calculated from RE and VO2max. Three stepwise regression models were used to determine the best predictors (classic vs treadmill performance protocols) for the 16-km running time trial., Results: Simple Pearson correlations of the variables with 16-km performance showed vVO2max to have the highest correlation (r = -0.972) and %VO2max at the LT the lowest (r = 0.136). The correlation coefficients for LT, VO2max, and PTV were very similar in magnitude (r = -0.903 to r = -0.892). When VO2max, %VO2max at LT, RE, and PTV were entered into SPSS stepwise analysis, VO2max explained 81.3% of the total variance, and RE accounted for an additional 10.7%. vVO2max was shown to be the best predictor of the 16-km performance, accounting for 94.4% of the total variance. The measured velocity at VO2max (PTV) was highly correlated with the estimated velocity at vVO2max (r = 0.8867)., Conclusions: Among well-trained subjects heterogeneous in VO2max and running performance, vVO2max is the best predictor of running performance because it integrates both maximal aerobic power and the economy of running. The PTV is linked to the same physiological variables that determine vVO2max.

The accuracy of a computerized metabolic system, using inspiratory and expiratory methods of measuring ventilation, was assessed in eight male subjects. Gas exchange was measured at rest and during five stages on a cycle ergometer. Pneumotachometers were placed on the inspired and expired side to measure inspired (VI) and expired ventilation (VE). The devices were connected to two systems sampling expired O(2) and CO(2) from a single mixing chamber. Simultaneously, the criterion (Douglas bag, or DB) method assessed VE and fractions of O(2) and CO(2) in expired gas (FE(O(2)) and FE(CO(2))) for subsequent calculation of O(2) uptake (VO(2)), CO(2) production (VCO(2)), and respiratory exchange ratio. Both systems accurately measured metabolic variables over a wide range of intensities. Though differences were found between the DB and computerized systems for FE(O(2)) (both inspired and expired systems), FE(CO(2)) (expired system only), and VO(2) (inspired system only), the differences were extremely small (FE(O(2)) = 0.0004, FE(CO(2)) = -0.0003, VO(2) = -0.018 l/min). Thus a computerized system, using inspiratory or expiratory configurations, permits extremely precise measurements to be made in a less time-consuming manner than the DB technique.

Purpose: To define and describe the essential terminology associated with dose-response issues in physical activity and health., Methods: Recent consensus documents, position stands, and reports were used to provide reference definitions and methods of classifying physical activity and exercise., Results: The two principal categories of physical activity are occupational physical activity (OPA) and leisure-time physical activity (LTPA). OPA is usually referenced to an 8-h d, whereas the duration of LTPA is quite variable. LTPA includes all forms of aerobic activities, structured endurance exercise programs, resistance-training programs, and sports. Energy expenditure associated with aerobic activity can be expressed in absolute terms (kJ x min(-1)), referenced to body mass (METs), or relative to some maximal physiological response (i.e., maximal heart rate (HR) or aerobic power (VO(2max))). The net cost of physical activity should be used to express energy expenditure relative to dose-response issues. The intensity of resistance training is presented in terms relative to the greatest weight that can be lifted one time in good form (1RM). The intensity of OPA followed the guidance of a previous consensus conference. The intensity of most LTPA can be categorized using the standard aerobic exercise classifications; however, for long-duration (2+ hours) LTPA, the classifications for OPA may be more appropriate., Conclusion: Physical activities should be classified in a consistent and standardized manner in terms of both energy expenditure and the relative effort required.

The purpose of this investigation was to assess the accuracy of the COSMED K4 b2 portable metabolic measurement system against the criterion Douglas bag (DB) method. During cycle ergometry on consecutive days, oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and respiratory exchange ratio (R) were measured at rest and during power outputs of 50, 100, 150, 200, and 250W. No significant differences (P > 0.05) were observed in VO2 between the K4 b2 and DB at rest and at 250W. Though the K4 b2 values were significantly higher (P<0.05) than DB values at 50, 100, 150, and 200 W, the magnitude of these differences was small (0.088, 0.092, 0.096, and 0.088 L x min(-1), respectively). VCO2 and VE values from the K4 b2 were significantly lower than the DB at 200 and 250 W, while no significant differences were observed from rest through 150W. The slight overestimation of VO2 (50-200 W) combined with the underestimation of VCO2 (200 and 250W) by the K4 b2 resulted in significantly lower R values at every stage. These findings suggest the COSMED K4 b2 portable metabolic measurement system is acceptable for measuring oxygen uptake over a fairly wide range of exercise intensities.

Objective: The purpose of this study was to validate the use of the leg-to-leg bioelectrical impedance analysis (BIA) system in assessing change in body composition over 32 weeks in overweight and obese women participating in a community weight management program., Design: Intervention, with subjects prescribed an energy-restriction diet and exercise program for 32 weeks and body composition measured pre-study and after 12 and 32 weeks., Subjects and Setting: Overweight and obese premenopausal women (n=201) with no overt disease were recruited at six sites into community-based weight loss programs. One hundred and twenty-four women completed all aspects of the study., Intervention: Energy intake was set at 0.8 x resting metabolic rate (RMR) for weeks 1 through 12, 1.0 x RMR for weeks 13 through 20 and 1.2 x RMR for weeks 21 through 32. Energy intake was based on a food exchange table, with the number of food exchanges adjusted to encourage a percent distribution of 55% carbohydrate, 30% fat and 15% protein. Subjects increased their daily walking distance by 3.2 km above pre-study levels., Measures of Outcome: Underwater weighing, seven skinfolds, and leg-to-leg BIA tests were used to assess body composition., Results: A 3 x 3 repeated measures ANOVA revealed no significant difference in detecting change in FFM at 12 and 32 weeks among underwater weighing, BIA and skinfold, (F(4,492)=1.73, p=0.141) (decrease in FFM of 1.0+/-3.3 kg, 1.7+/-2.2 kg, and 1.4+/-3.3 kg respectively, 32 weeks)., Conclusions: The leg-to-leg BIA system provides a valid measure of body composition change in overweight premenopausal women during a 32-week community-based weight loss program.

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) were made at rest and at power outputs of 50, 100, 150, 200, and 250 W. No significant differences (P > 0.05) were observed for VE, VO2, and VCO2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (FEO2) and carbon dioxide (FECO2) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable metabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L x min(-1), using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

We examined the effect of acute exercise and reduced cortisol on pituitary and adrenal responsiveness and the impact of reduced plasma cortisol on maximal oxygen consumption (VO2max) in eight trained (T) and eight untrained (UT) males. Subjects completed two graded maximal exercise tests (GXT), each preceded by either overnight metyrapone (MET) or placebo (PLA) administration. Blood samples were collected before and after GXT. With PLA, resting corticotropin (ACTH) levels were higher in T versus UT men; however, cortisol and 11-deoxycortisol were similar between groups. Following GXT on PLA, cortisol was unchanged but 11-deoxycortisol increased in both groups; however, ACTH increased only in UT men. For both groups, cortisol, 11-deoxycortisol, and ACTH were different post-GXT with MET versus PLA. Furthermore, following GXT with MET, the ACTH response was greater in T versus UT subjects. VO2max was not altered by MET in either group. We conclude that (1) at rest, only ACTH levels differed between T and UT men; (2) individually, the GXT and MET provide a similar ACTH response in UT but not in T subjects; (3) when GXT and MET are superimposed, they provide a stronger stimulus to pituitary and adrenal reserve than either test alone; (4) the combination of MET and GXT elicits a greater ACTH response in T compared with UT men; and (5) an acute reduction in plasma cortisol does not alter VO2max.

Normotensive individuals who exhibit an exaggerated blood pressure (BP) response to exercise have an increased risk of future hypertension. However, previous studies failed to control for resting BP despite the fact that an elevated resting BP in the normotensive range is also a strong predictor of future hypertension. Therefore, we determined whether maximal systolic BP is associated with resting BP. Resting BP was measured in 68 healthy normotensive men on three separate days. The subjects then performed a graded, maximal exercise test on a Monark cycle ergometer. Maximal systolic BP was strongly correlated with resting systolic BP (r = 0.64, P < 0.0001). Subjects with elevations in systolic BP during maximal exercise (> 220 mmHg) also had higher (P < 0.005) resting BP than those without (< 220 mmHg). When stepwise regression analyses were performed, systolic BP at rest was a significant independent predictor of maximal systolic BP, explaining over 40% of the variability. These results suggest that exaggerated BP response as a predictor of future hypertension reported in previous studies may be little more than a simple reflection of elevated resting BP. Specifically, these studies should not be interpreted as demonstrating that exercise BP is a better predictor of future hypertension than resting BP alone. In the future, defining the BP 'response' to exercise as a change score (i.e. maximal BP minus resting BP) may be advantageous as it permits the effects of exercise to be examined independently of the level of resting BP.

This study examined the physiological effect of reduced plasma cortisol (C) during prolonged exercise in humans. The effects of normal C (NC) were compared with metyrapone-induced low C (LC) on plasma substrate availability and the respiratory exchange ratio during 2 h of exercise at approximately 60% peak O2 consumption in nine subjects. The C responses were compared with preexercise (Pre) levels and with a rest day (Con). At rest, C was attenuated by approximately 70% for LC compared with NC. At rest, plasma glucose, lactate, glycerol, beta-hydroxybutyrate, alanine, branched-chain amino acids, insulin, glucagon, growth hormone, epinephrine, and norepinephrine were similar under LC and NC (P > 0.05). During exercise under NC, plasma C increased compared with Pre, whereas it remained unchanged during LC. During NC, plasma C was elevated at 90 min (compared with Con) and at 120 min (compared with Con and Pre). During exercise, plasma glucose decreased to the same extent and lactate was similar under both conditions, whereas plasma glycerol, beta-hydroxybutyrate, alanine, and branched-chain amino acids were higher (P < 0.01) under NC. Plasma insulin declined (P = 0.01) to a greater extent under LC, whereas growth hormone, epinephrine, and norepinephrine tended to be higher (0.05

The beneficial effects of regular exercise are primarily based on data using land-based exercise. Currently, no data exist that demonstrate the efficacy of swimming exercise for the treatment of obesity and cardiovascular risk factors, despite the fact that swimming is a widely recommended exercise mode. Eighteen previously sedentary obese individuals were divided into a swim-training group and a non-exercising control group. The training group swam at 60% of maximal heart rate reserve for 45 min per day for 3 days per week for 10 weeks, whereas the control group remained sedentary. The swim-training programme produced significant cardiovascular training effects, as evidenced by reductions (P < 0.05) in resting and submaximal heart rate values in the training group. Significant reductions (P < 0.05) were also observed in the rating of perceived exertion and blood lactate concentrations during fixed submaximal exercise on an arm cycle ergometer. Caloric and macronutrient intake estimated from the dietary records stayed constant before and after training. Body mass, body fat percentage (36 +/- 2% vs. 35 +/- 2%) and body mass index, as well as regional adiposity, showed no statistically significant changes. Neither the training nor the control groups experienced significant changes in fasting serum glucose and insulin concentrations and glucose-insulin ratio during the study. Total, high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol did not change significantly in either group. It was concluded that swim training of the duration, frequency and intensity used in the present study failed to elicit favourable modifications in these traditional cardiovascular risk factors.

The purpose of this study was to compare muscle fibre type proportions and capillary density in untrained, college-aged blacks (n = 14) and whites (n = 14). Both groups were similar in terms of peak oxygen uptake (VO2peak), measured during cycle ergometry (blacks: 42.6 +/- 4, whites: 44.3 +/- 4 ml.kg-1 min-1, mean +/- SD). Muscle samples were obtained from the quadriceps femoris (vastus lateralis) by the needle biopsy technique. Fibre type was determined by myosin ATPase stain (pH = 4.54) and capillaries were identified by amylase-periodic acid Schiff (PAS) stain. The percentage of type I, IIa, and IIb fibres in the blacks was 39.5 +/- 11.5, 40.0 +/- 8.4, and 22.8 +/- 9.8, respectively. In whites the percentage of type I, IIa, and IIb fibres was 44.9 +/- 8.5, 36.6 +/- 6.9, and 18.3 +/- 9.6, respectively. No significant differences were noted between the two racial groups for type I, IIa, or IIb fibres. Capillary density was 277 +/- 39/mm2 in the blacks compared to 289 +/- 32/mm2 in the whites. Capillary density was positively correlated to percentage of type I fibres (r = 0.497) and negatively correlated to percentage of type IIa fibres (r = -0.389), in the overall study population. These data suggest that if racial differences in fibre type do exist, such differences are small compared to the variability in this measure.

In an attempt to determine whether the lactate threshold (LT) is the result of a sudden increase in plasma epinephrine (Epi), eight healthy college-aged males (22.4 +/- 0.4 yr) were recruited to perform three cycle ergometer exercise tests. Each subject performed a graded exercise test (GXT) to determine LT, Epi threshold, and norepinephrine threshold (64.6 +/- 2.4, 62.5 +/- 2.4, and 60.8 +/- 4.3% peak oxygen uptake, respectively). Each subject also completed, in random order, two 30-min submaximal (20% peak oxygen uptake below LT) exercise tests. During one test, graded Epi infusions were carried out at rates of 0.02-0.12 micrograms.kg-1.min-1; the other served as a control test. Infusion resulted in plasma Epi concentrations similar to those observed during GXT. The increase in blood lactate with Epi infusion was significantly greater than that during the control test (3.0 +/- 0.3 vs. 1.4 +/- 0.1 mmol/l at minute 30) but did not approach levels exhibited during GXT. We suggest an interaction of the increasing plasma Epi with other factors may be responsible for the sudden increase in blood lactate during graded exercise.

The purpose of this study was to examine the cardiovascular responses of sprinters and distance runners to isometric (IE) and dynamic exercise (DE). Normotensive males were selected and grouped according to prior running performance: sprinter (N = 6) or distance runner (N = 6). Each subject completed an incremental DE (cycle ergometry) test (6-min stages) at 20%, 40%, and 60% of VO2peak, and 3 min of isometric handgrip at 30% of MVC. Blood pressure (BP), heart rate (HR), cardiac output (Q), oxygen uptake, and blood lactate were measured, while mean arterial blood pressure (MABP), cardiac index (CI), and systemic vascular resistance (SVR) were calculated during each stage of DE. BP and HR were measured during each minute of IE. Muscle biopsies of the vastus lateralis revealed a significant difference in capillary density (capillaries per mm2 and capillaries per fiber) between the sprinters and distance runners (323 +/- 23 vs 409 +/- 27 and 2.2 +/- 0.2 vs 3.2 +/- 0.3, P < 0.05) and for the percentage of Type I fibers (46.4 +/- 4% vs 64.8 +/- 7%, P < 0.05). The IE challenge elicited a greater BP response at minute 3 in the sprinters, which was associated with a greater HR response. During DE, there were no significant differences in BP or HR between the groups. However, at 60% of VO2peak, the distance runners had a significantly higher cardiac index and a lower systemic vascular resistance than the sprinters (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Polylactate (PL), a semi-soluble amino acid/lactate salt, is a newly developed carbohydrate supplement purported to increase endurance. Our purpose was to determine if the addition of PL to a glucose polymer solution (GP) extends exercise time relative to a pure GP solution. In a double blind and random crossover design, 5 subjects exercised twice to exhaustion at 70% of VO2max. During the trials, they consumed GP or a GP/PL mixture at the rate of 0.3 g carbohydrate per kg of body wt in a 7% solution every 20 min until exhaustion. The GP/PL mixture contained 6.25 g GP to 0.75 g PL per 100 ml of water. Mixture composition was critical because PL, as supplied by the manufacturer and under our experimental conditions, produced severe gastro-intestinal efflux in concentrations > or = 2.5%; PL was tolerable in concentrations < or = 0.75%. At 20 min intervals, we measured VO2, respiratory exchange ratio, heart rate, and perceived exertion. At 30 min intervals, we measured serum glucose, insulin, free fatty acids, and glycerol as well as whole blood lactate and pH. We found that the addition of PL to a GP solution had no measurable physiological or performance effects.

The present investigation compared the pattern of substrate utilization during prolonged walking in obese women with upper (UB) and lower (LB) body fat patterns and the effect of beta-adrenergic receptor blockade on that response. Twenty healthy, premenopausal, obese volunteers (% fat > or = 30%) were characterized by waist-to-hip (WHR) circumference ratios into two distinct groups (UB: WHR > or = 0.85, LB: WHR < or = 0.75). The groups (n = 10 each) were similar for BMI, age, % fat, and maximal aerobic power (VO2max). Subjects participated in two 60-min walk bouts at 55-60% VO2max. The trials (placebo (C) and 80 mg propranolol (PR)) were performed in random order, 110 min after ingestion, with 2-4 days between tests. Open-circuit spirometry was employed to calculate the VO2, VCO2 and respiratory exchange ratio (RER) at 10 min intervals. A significant (P < 0.0001) decline in RER with time was evident in both trials. However, no group differences existed in RER values during either the C trial (RER range = 0.81-0.88) or the PR trial (RER range = 0.86-0.91). The PR trial induced a 23% reduction in the amount of calories utilized as fat compared to C in both WHR groups. Both groups of women showed equal capabilities for performing prolonged exercise with typical and appropriate metabolic shift in fuel mobilization from carbohydrate to fat. Despite the well-defined differences in metabolic activity of adipose cells shown in vitro, this study indicates that women with significantly different regions of adipose tissue stores have similar physiological potentials for substrate use during exercise.

The application of automated blood pressure measurement during exercise has been limited by inaccuracies introduced by the effects of accompanying motion and noise. We evaluated a newly developed automated blood pressure monitor for measuring exercise blood pressure (Colin STBP-680; Colin, San Antonio, Texas, USA). The STBP-680 uses acoustic transduction with the assistance of the electrocardiogram R-wave to trigger the sampling period for blood pressure measurement. The automated monitor readings were compared with simultaneous technician mercury sphygmomanometric readings in the same arm. Blood pressure was measured in 18 men at rest and during exercise at 40% VO2 peak, (low intensity), 70% VO2 peak (moderate intensity) and VO2 peak (high intensity) on the cycle ergometer. Mean(s.d.) systolic blood pressure difference between the automated monitor and mercury manometer readings at rest and during exercise at low, moderate and high work intensities were 3(0) mmHg, 3(2) mmHg, 1(1) mmHg, and 0(11) mmHg respectively (analysis of variance; P > 0.05). Resting diastolic blood pressure obtained with the STBP-680 was similar to the mercury manometer readings (78(10) versus 81(7) mmHg (P > 0.05). Exercise diastolic pressure at the low level of work intensity was almost identical between the automated monitor and mercury manometer readings (64(8) versus 65(10) mmHg (not significant)). Diastolic blood pressure readings between the STBP-680 and mercury manometer showed a greater difference at the moderate and high workloads (11 mmHg and 9 mmHg, respectively), but this difference was not significant (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this study was to examine the effect of one- and two-leg training on arm and two-leg maximum aerobic power. Seven subjects cycle-trained both legs simultaneously for 30 min.day-1, 4 days.week-1 for 4 weeks. Nine subjects cycle-trained each leg 15 min.day-1, 4 days.week-1 for 4 weeks. Both groups trained at a heart rate equal to that measured at 75% of their two-leg maximum aerobic power. Thus, during each training session the groups performed 30 min of work at the same heart rate intensity. Five subjects served as a non-training control group. Arm and leg maximum oxygen uptake tests were conducted before and after training. Only two-leg training induced significant gains in arm aerobic power (P < 0.0003), whereas both modes of training resulted in significant increases in two-leg aerobic power (P < 0.0008). The data demonstrate that improvements in arm aerobic power were dependent on the quantity of leg muscle mass involved in the training, whereas gains in two-leg aerobic power occurred regardless of whether the legs were trained separately or simultaneously.

The purpose of this study was to examine the effect of moderate resistance weight training (MRWT) on peak arm aerobic power as measured by arm cranking ergometry. Fourteen sedentary college age males, divided equally into two groups, served as subjects. The seven subjects in the MRWT group completed 12, 1-hr bouts of weight lifting over a 4 week period, exercising on Monday, Wednesday and Friday of each week. Exercise sessions included 3 sets of 10 repetitions of the following lifts: bench press, overhead dumbbell press, dumbbell arm curl, and behind the neck pull down. The remaining seven subjects served as a non-training control group, whose purpose was to account for possible learning effects on the arm ergometer test that could distort the statistical relevance of the aerobic power data. These subjects did not serve as a control for the weight training exercises, as the procedures used to determine muscular strength may produce a modest training effect. Peak arm aerobic power and muscular strength, as measured by the one-repetition maximum for each lift, were determined before and after the training program. The average increase in strength for all lifts combined for the trained group was 20.0%. They also experienced a 13.4% (p < .005) increase in peak arm aerobic power, whereas there was no significant change in this variable for the control group. It is concluded that peak arm aerobic power is enhanced by the changes in muscular strength produced by 4 wks of MRWT.

This study was performed to determine whether alterations in vascular structure exist in a biracial population of young (age 22.3 +/- 0.6 yrs [mean + SE]) normotensive men. We examined maximal vasodilatory capacity in 21 blacks and 20 whites (average blood pressure = 122/75 and 118/72 mm Hg, respectively). Forearm blood flow was determined at rest and after 10 min of ischemic handgrip exercise using venous occlusion plethysmography. Forearm vascular resistance was computed from blood flow and mean arterial blood pressure determined by auscultation. Minimum forearm vascular resistance was 23% higher in blacks (2.60 +/- 0.60) than in whites (2.11 +/- 0.41) (P = .005), and was unrelated to parental history of hypertension. The regression equation for minimum forearm vascular resistance (Y) and casual blood pressure (X) for blacks was Y = -1.782 + 0.0487X (r = 0.522); for whites it was Y = -1.165 + 0.0367X (r = 0.418). When the data were covaried on resting mean arterial blood pressure, blacks still had a higher minimum forearm vascular resistance (P = .014). The results suggest a racial difference in the vascular structure of the forearm resistance vessels.

The purpose of the present study was to assess possible racial differences in cardiovascular and plasma catecholamine responses to dynamic exercise. A biracial group of normotensive college-age men (15 blacks, 15 whites) were tested for maximal oxygen uptake, resting blood pressure, and heart rate. Subjects then rode a cycle ergometer at 25%, 50%, and 75% of peak oxygen uptake (6 minutes at each stage). Blood pressure and heart rate were measured during supine rest, seated rest, and at each stage of exercise with an automated blood pressure monitor. At each stage, venous blood was sampled to allow determination of plasma norepinephrine and epinephrine, and cardiac output was measured with the carbon dioxide rebreathing technique. The results indicated that resting blood pressure was similar for blacks and whites (114/68 versus 115/68 mm Hg, respectively). Blacks exhibited greater systolic and diastolic blood pressures during submaximal dynamic exercise. However, blacks also showed a trend toward a positive parental history of hypertension, which has been associated with an increased pressor response. Racial differences did not exist for heart rate or cardiac output, but blacks had higher values for total peripheral resistance both at rest and during exercise. Although no overall racial differences were seen for plasma catecholamine concentrations at rest, blacks had significantly lower levels of norepinephrine (1,275 versus 1,556 pg/ml) and higher levels of epinephrine (306 versus 216 pg/ml) than whites at the highest work rate. The current study confirms the increased pressor response to exercise in normotensive blacks. Blacks had an elevation in total peripheral resistance that was not accompanied by an increase in plasma norepinephrine levels.

The purposes of this study were to evaluate (a) the effects of step rate and upper body support on the VO2 and HR responses to fixed work rates on the StairMaster 4000 (SM), (b) the accuracy of the SM settings, and (c) how HR compared with that measured during grade-walking on a treadmill. Six subjects worked at a slow step rate for 6 min and then a faster step rate for the last 6 min of a 12-min test at SM settings of 4, 7, and 10 METs. Gas exchange and HR measurements were made at minutes 4-6 and 10-12. Variations in step rate had no effect on HR (P = 0.45) or VO2 (P = 0.84). The effect of using the arms and hands for support was studied using 6 subjects who worked for 12 min at 4, 7, and 10 METs; the first 6 min without support, and the second 6 min with support. Support resulted in lower HR (P = 0.017) and VO2 (P = 0.002) values at 10 METs. The measured MET values were about 20% lower than those specified by machine settings: True MET values = 0.556 + 0.745 (SM setting). Finally, at the same VO2, systematically higher (7-11 b.min-1) HR values were observed for the SM relative to the treadmill.

We examined the metabolic responses to front crawl swimming when following directly behind (drafting) another swimmer. Seven trained male swimmers participated as subjects. VO2max (l.min-1) was measured during a progressive tethered swim test and was also estimated from a 20 s sample of expired air collected immediately after an all-out, 549 m (600 yard) swim. On different days, each subject performed two 549 m trials at 95% of his maximal swim velocity, one with drafting and one without drafting, using a counter-balanced design. Underwater pace lights were used to establish the predetermined swim velocity. Drafting significantly reduced post-exercise VO2 (2.85 +/- 0.63 vs 3.12 +/- 0.66 l.min-1), blood lactate (3.4 +/- 0.6 vs 5.0 +/- 0.5 mM), and rating of perceived exertion (11.7 +/- 0.4 vs 14.9 +/- 0.5) (P less than 0.05). A repeated measures ANOVA (condition X distance) also revealed significant reductions in HR during the 549 m swim (137.7 vs 146.8 beats.min-1) (P less than 0.05). The results indicate that drafting results in a decrease in energy expenditure for the range of speeds examined.

This study has shown, for the first time, that the change in plasma adenosine 3',5' cyclic monophosphate (cAMP), from accommodation or trough levels, correlates highly in both progressive and continuous work stress experiments with epinephrine (E) at 0.990 and 0.898, and norepinephrine (NE) at 0.954 and 0.927, respectively, in men subjected to the same relative, rather than absolute, stress levels. All three analytes increased significantly (p less than 0.05) by the time each subject had reached 80% of their Vo2 max in the progressive experiments and after working at 80% of their Vo2 max continuously for 10 min. In no case did plasma cAMP rise before the catecholamines. The possible significance of these observations to net perceived relative physiological stress are discussed.

Plasma catecholamines (Ca) increase over time during prolonged exercise at a constant work rate. Possible reasons for this include hypoglycemia, dehydration, increased perceived exertion, and rising body temperature. In an effort to ascertain the contribution of elevated core temperature on the plasma Ca response to prolonged exercise four trained men were studied under two thermal conditions during 45 min of bicycle exercise (approximately 60% Vo2max) and during passive heating. On one testing day each subject was heat-stressed during exercise wearing a nylon pullover shell and cotton pants, (heat stress treatment); on the second day fans were directed on the subjects exercising in a thermoneutral environment (fan treatment). The passive heating experiment was conducted in a hot water bath (41 degrees C). The exercise heat stress treatment produced a higher plasma norepinephrine (NE) concentration (P less than 0.05) in all subjects than the fan treatment. The plasma epinephrine (E) concentration was not significantly (P greater than 0.05) different during exercise in the heat stress treatment from that found during fan treatment. A rise in rectal temperature (Tre) during passive heating resulted in quantitatively small changes in plasma E and NE. The heat load combined with the exercise task produced an increase in plasma NE concentration greater than the sum of the values measured during exercise in the thermoneutral environment and passive heating. This suggested that the combination of stressors caused an augmentation of the sympathetic nervous system's response. Finally, the added heat load caused changes in plasma NE and little change in plasma E, suggesting a differential Ca response with heat stress.

It has been suggested in the lay literature that static stretching and/or warm-up will prevent the occurrence of Delayed-Onset Muscle Soreness (DOMS). The primary purpose of this study was to determine the effects of static stretching and/or warm-up on the level of pain associated with DOMS. Sixty-two healthy male and female volunteers were randomly assigned to four groups: (a) subjects who statically stretched the quadriceps muscle group before a step, (b) subjects who only performed a stepping warm-up, (c) subjects who both stretched and performed a stepping warm-up prior to a step test, and (d) subjects who only performed a step test. The step test (Asmussen, 1956) required subjects to do concentric work with their right leg and eccentric work with their left leg to voluntary exhaustion. Subjects rated their muscle soreness on a ratio scale from zero to six at 24-hour intervals for 5 days following the step test. A 4x2x2 ANOVA with repeated measures on legs and Duncan's New Multiple Range post-hoc test found no difference in peak muscle soreness among the groups doing the step test or for gender (p greater than .05). There was the expected significant difference in peak muscle soreness between eccentrically and concentrically worked legs, with the eccentrically worked leg experiencing greater muscle soreness. We concluded that static stretching and/or warm-up does not prevent DOMS resulting from exhaustive exercise.

Anticipation of a potentially stressful situation can alter the activity of the sympathetic nervous system. The purpose of this study was to measure the effect of three different intensities of exercise on epinephrine (E) and norepinephrine (NE) excretion when the work test order was randomly assigned and the subjects were not informed of the test order. Six subjects exercised at work loads which averaged 49%, 65%, and 82% Vo2max. Each subject showed an increased rate of NE excretion as the work load increased. The differences among work loads were significant (P less than 0.01). The E response was less consistent. Two subjects showed the greatest rate of excretion at the lowest work load, and one subject showed no increase above his pre-exercise resting value. While NE excretion was closely related to the work load, factors other than exercise appeared to exert considerable influence on the rate of E excretion during exercise.