Impact of starting strategy on cycling performance.

In order to determine an optimal starting technique, the first four-min of two 20 km time trials (TT) were manipulated. Thirteen competitive, male cyclists (22.7 +/- 0.8 yr, 180.6 +/- 2.2 cm; 77.1 +/- 2.8kg; 8.3+/-0.7% fat; 4.9+/-0.21 x min(-1), 71.7+/-1.4% of VO2max) performed three, 20 km TTs. The pace of the first TT was self-selected (SS). Min 1-4 of the subsequent, randomly assigned TTs were performed 15% below and 15% above the average power output (PO) of min 1-4 of the SS TT, subjects then completed the TT as quickly as possible. As a percent change from the SS TT, the 15% below TT was (p < 0.05) faster than 15% above TT. Lactic acid values at min 4 of the 15% below TT (4.87+/-0.73mM x l(-1)) were lower (p<0.05) than both SS TT (9.78+/-1.05mM x l(-1)) and 15% above TT (11.54+/-1.00mM x l(-1)). Following min 4 to the finish there were no differences in VE, HR, or RPE. However, VO2, VO2 with respect to lactic acid threshold, and PO were all elevated in the 15% below TT as compared to both SS TT and 15% above TT. The initially high LA resulting from the starting strategies of the SS TT and 15% above TT may have reduced the work capacity of active muscle.

Physiological determinants of cross-country ski racing performance.

PURPOSE: Previous laboratory testing has identified the importance of upper-body aerobic and anaerobic power to cross-country skiing performance. The purpose of this investigation was to extend laboratory research into a field setting to identify predictors of performance through ski-specific testing. METHODS: Thirteen male collegiate skiers performed three field-testing sessions on roller skis to establish lactate threshold (LT) and ski economy (ECON) and maximal oxygen uptake (SK VO(2max)) and a 1-km double-pole time trial (UBTT) to determine peak upper-body oxygen uptake (UB VO(2)). As a measure of skiing performance, the subjects performed a 10-km skating time trial (TT) and were ranked according to competitive season performance (RANK). RESULTS: Significant correlations (P < 0.05) were found between SK VO(2max), LT VO(2), UB VO(2), and RANK (r = -0.66 to -0.84) and TT time (r = -0.74 to -0.79), as well as ECON to RANK (r = 0.57) and TT time (r = 0.68). Time to complete the UBTT (UB time) exhibited the strongest correlation to both RANK (r = 0.95) and TT time (r = 0.92). Multiple regression analyses revealed that UB time was the best predictor of RANK and TT time, as demonstrated by the significant beta values (0.77, P < 0.001, and 0.79, P < 0.001, respectively). The importance of the UB component was further seen in that UB time was still the best predictor of performance when the subjects were divided into two distinct groups of greater and lesser competitive ability. CONCLUSIONS: These findings identify the importance of the upper body component to cross-country skiing performance, suggesting a need to focus on upper-body conditioning within a well-rounded endurance training program. Additionally, the UBTT exhibits potential as a simple field test to predict cross-country skiing performance over more sophisticated and costly laboratory and field testing.

Lactic acid accumulation in cardiac patients performing circuit weight training: implications for exercise prescription.

OBJECTIVE: Because blood lactic acid (LA) levels may be important in prescribing exercise for cardiac patients, this study documented the LA response to four different circuit weight training (CWT) protocols and compared these responses to both maximal treadmill and LA threshold values. DESIGN: Intervention study following a crossover trial design. SETTING: A phase III community-based setting. PATIENTS: All subjects had documented cardiac disease and were volunteers. INTERVENTIONS: We used 40% and 60% of the one-repetition maximum (1-RM) for six exercises and 30 or 60sec of rest between each station, resulting in four protocols, performed in random order. A discontinuous treadmill test was conducted, and the LA threshold was determined. MAIN OUTCOME MEASURE: The main dependent variable was LA after each CWT protocol. RESULTS: No signs or symptoms suggestive of cardiovascular distress during any of the four CWT protocols were reported. A repeated-measures analysis of variance showed that the LA threshold value was significantly less than all four CWT protocols (p < .05). The CWT responses were also compared with the traditional LA threshold value of 4.0mmol/L, and both 60% protocols were significantly elevated (p < .05). CONCLUSION: Because no positive signs or symptoms were reported, we recommend starting stable cardiac patients on a CWT program with an initial load between 40% and 60% 1-RM and allowing at least 60sec of rest between exercises.

Circuit weight training in cardiac patients: determining optimal workloads for safety and energy expenditure.

BACKGROUND: While most studies suggest circuit weight training (CWT) to be safe in cardiac rehabilitation populations, few investigators have controlled variables known to impact CWT intensity. Therefore, the purposes of this study were to determine the energy cost and evaluate safety of cardiac patients while varying rest interval duration and lifting load in a CWT format. METHODS: Nine male subjects with documented coronary artery disease had maximal oxygen uptake (VO2max), one-repetition maximum (1-RM), and body composition tested. In random order and on separate days, 4 CWT sessions using either 40% or 60% of the 1-RM, and either 30 or 60 seconds of rest between stations were completed. Energy cost, heart rate (HR), blood pressure (BP), and rate-pressure product (RPP) were measured. Data were analyzed with a repeated measures analysis of variance, and Tukey's post-hoc test was performed when significant results were found. The alpha level was set at < .05. RESULTS: Subjects exercised at 25% to 32% of VO2max (58%-67% of HRmax) during CWT. The HR and RPP responses were lower during all CWT protocols than at 85% of the treadmill VO2max. No subject displayed any ST-segment depression or angina during CWT. The 40%-60-second protocol had an energy cost (2.98 kcal/min) that was lower (P < .05) than the other protocols (3.48-3.81 kcal/min). Increasing the lifting load resulted in increases (P < .05) in energy cost, and decreasing the rest interval increased energy cost only during the 40% 1-RM protocols. CONCLUSIONS: Results indicate that CWT protocols of varied intensity are safe for cardiac patients when compared to treadmill exercise, and changes in rest interval duration and load can impact the energy cost.

Physiologic responses of cardiac patients to supine, recumbent, and upright cycle ergometry.

Physiological responses were compared in nine stable male cardiac patients (mean +/- standard error (SE): age, 68.3 +/- 8.1 years; height, 172.7 +/- 3.9cm; weight, 72.8 +/- 14.5kg) during stationary cycling in the supine, recumbent, and upright positions. A discontinuous exercise protocol was performed in which each stage included 3 minutes of exercise and 1 minute of recovery. Each subject's workload started at 150kgm.min-1 and increased by 150kgm.min-1 per stage until volitional fatigue. Testing sessions were randomized and performed 1 week apart. Subjects continued their normal medication regimen. All subjects were participants in a community-based cardiac rehabilitation program. Dependent variables were assessed at two different intensities; submaximal (300kgm.min +/- 1) and maximal. A two-way repeated measures ANOVA found no significant differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), minute ventilation (VE), respiratory exchange ratio (R), rate pressure product (RPP), and rating of perceived exertion (RPE) at submaximal (300kgm.min +/- 1) and maximal exercise efforts. Heart rate (HR) was significantly lower (p < or = .05) in the supine position compared with either the upright or recumbent positions during the submaximal workload. In addition, oxygen uptake (VO2) was significantly lower in the supine position at the submaximal workload (p < or = .05) compared with both upright and recumbent. No difference in HR or VO2 was observed at maximal exercise. Regressions of HR on VO2 showed similar slopes and intercepts for supine, recumbent, and upright ergometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Postexercise oxygen consumption in trained females: effect of exercise duration.

Many research studies report the long-lasting elevation of metabolism following exercise. However, little is known regarding the impact of duration and intensity on this phenomenon, particularly in trained women in whom the time of the menstrual cycle has been controlled. This study examined the effects of a constant walking intensity (70% of maximal oxygen uptake (VO2max)) on the treadmill at various levels of duration (20, 40, and 60 min) on 3-h recovery of oxygen uptake (VO2). Eight trained (mean +/- SD) (VO2max = 47.6 +/- 3.2 ml.kg-1.min-1) females (mean age = 30.2 +/- 5.0 yr, mean weight = 58.7 +/- 7.6 kg, mean height = 165.6 +/- 7.0 cm) participated in the study. Subjects reported to the lab for a maximal oxygen consumption test and returned on four additional occasions (control, 20, 40, 60 min) in random fashion. Treadmill speed and grade were established to yield the appropriate intensity for each subject. Following each exercise bout subjects sat quietly for a 3-h time period. Variables measured included VO2, minute ventilation (VE), respiratory exchange ratio (RER), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and core (rectal) temperature (Tc). Variables were measured each 15 min of recovery. An ANOVA was used to assess differences due to duration. Excess postexercise oxygen consumption (EPOC) was calculated by subtracting the resting VO2 from the absolute VO2 and summing the individual EPOCs during each 3-h postexercise session and comparing these individual values to the preexercise VO2 values. The EPOC was significantly elevated (P < 0.05) in each of the three durations as compared with the control (sitting) and preexercise periods. The total EPOC was significantly higher for the 60-min duration (15.2 l) as compared with either 20-min (8.b l) or 40-min (9.8 l) duration (P < 0.05). This was observed without significant changes in VE, RER, HR, SBP, DBP, or Tc. Additionally, there were no differences during exercise across the three durations in VO2, VE, RER, HR, SBP, DBP, or Tc. These data suggest that exercise duration increases EPOC significantly and that a 60-min duration yields approximately twice the EPOC than either 20 or 40 min.

Reflex venomotor responses to lower body negative pressure following endurance training.

The effect of endurance training on reflex venomotor control during an orthostatic challenge was investigated in 11 sedentary male volunteers. An exercise (E) group (n = 6) underwent 12 weeks of endurance exercise training, whereas a control (C) group (n = 5) remained sedentary. Training significantly increased VO2max values in E (pre-training: 37.0 +/- 2.5 ml.kg-1.min-1; post training: 44.6 +/- 2.5 ml.kg-1.min-1), while C showed no significant change. During exposures to two levels of lower body negative pressure (-10 and -40 mm Hg), both C and E groups showed similar graded decreases in forearm venous volume (FVV). The magnitude of the FVV decreases did not differ between groups or when comparing pre-training and post-training values. We conclude that the reflex venoconstrictor response to LBNP was not affected by endurance training.

Cardiovascular response to lower body negative pressure (LBNP) following endurance training.

Eleven sedentary male volunteers were assigned to either an exercise (E) group (n = 6; endurance exercise for 12 weeks) or a control (C) group (n = 5; no exercise). After training, E significantly increased (p less than 0.01) their VO2max (pretraining: 37.0 +/- 2.3; posttraining: 44.6 +/- 2.5), whereas C showed no significant change. Heart rate (HR), arterial blood pressure (BP) and forearm blood flow (FBF) were measured both pre- and posttraining at rest and during 2 levels of LBNP: -10 mm Hg and -40 mm Hg. Both C and E had similar decreases in systolic BP and similar increases in HR and diastolic BP during LBNP when comparing the pre- and posttraining periods. In both groups, FBF significantly decreased during -40 mm Hg of LBNP in the pretraining period. However, after training, E had a significantly attenuated (p less than 0.05) decrease in FBF at -40 mm Hg (pretraining: -45.0 +/- 3.7%; posttraining: -29.8 +/- 3.1%). In C, there was no difference in the response of FBF to -40 mm Hg of LBNP comparing pretraining and posttraining. These findings indicate that endurance exercise training decreases the forearm vasoconstrictor response to high levels of LBNP.

Effects of physical training and competition on the iron status of female field hockey players.

Female collegiate field hockey players showed decreases in iron stores (as measured by serum ferritin) in each of 3 successive fall seasons studied. After the 1st season of regular play, a decrease (25-23 ng/ml was observed, but measurements after post-season tournament play for the 2nd and 3rd seasons showed significant (P less than 0.05) decreases of 37% (30-19 ng/ml) and 30% (24-17 ng/ml), respectively. The added stress of tournament play appeared to cause additional loss of reserve iron nearly as great as that experienced during early season training. After several years of play, serum ferritin levels in these athletes were frequently between 10 and 20 ng/ml, with the lowest levels occurring in 3rd- and 4th-year athletes. Those women who participated in all 3 years had progressively declining serum ferritin levels throughout their collegiate careers. Participation in collegiate field hockey jeopardizes body iron stores, and iron reserves tend to become progressively more depleted after successive seasons of competition.

Effects of exercise-training on the thermic effect of food and body fatness of adult women.

Resting metabolic rate (RMR), thermic effect of food (TEF), aerobic capacity (VO2max), body fat, and food intake were measured in 10 healthy women before and after a 10 week graded exercise program of jogging. Pretraining TEF was a linear function of VO2max. Following exercise training, the women showed a significant increase (20%) in VO2max and loss (10.4%) of body fat; body weight did not change. Fat loss was directly related to changes in VO2max and RMR. The women showed a wide variation of changes in RMR (-21 to +2%) and TEF (-32 to +66%) from their pretraining levels. The changes in RMR and TEF were significantly positively correlated with improvements in VO2max. Analyses using multiple regression techniques, indicated that the changes in RMR and TEF accounted for 96.2% of the total variation in the changes of VO2max. Analyses of food intake indicated that diet composition (but not caloric intake) was highly related to the changes in VO2max, RMR, TEF and body fatness. Present results support further our hypothesis, that VO2max is an important physiological index of dietary thermogenesis and fat loss of individuals of normal body weight and fatness. Possible nutritional and physiological factors that may explain the wide variation in RMR and TEF of the women are discussed.

Normal variations in body surface electrocardiographic potential distributions during QRS: effects of exercise and exercise training.

Total body surface electrocardiographic potential distributions, oxygen uptake (VO2), blood pressure and heart rate were monitored during maximal exercise procedures performed by 26 normal adult subjects (male and female) covering a range from sedentary to fit. Normal variations in the exercise response of the ECG during QRS were found not to be related to variations in the level of cardiovascular fitness as quantified by maximal VO2 or to variations in maximal heart rate and blood pressure. In a second experiment, seven sedentary adult female subjects underwent an exercise training protocol for ten weeks. Maximal exercise tests were performed before and after the training period. Exercise-induced changes in the ECG during QRS were not affected by the physical training. We conclude that normal variations in the exercise response of the ECG during QRS are not related to the level of cardiovascular fitness of the subject.

Variations of dietary-induced thermogenesis and body fatness with aerobic capacity.

Resting metabolic rate (RMR), dietary thermogenesis (DIT), aerobic capacity (VO2 max), and percent body fat were measured in a group of sixteen women and ten men. DIT was significantly positively correlated with aerobic capacity (r = 0.658). Percent body fat was significantly negatively correlated with VO2 max (r = -0.727). RMR was independent of VO2 max, or body fatness, but women had a significantly higher average RMR than men. Three men and three women participated in an endurance training program which significantly increased VO2 max. DIT was increased in proportion to the increase in aerobic capacity (rs - 0.924), RMR was unchanged, and body fat decreased in males but not females. The controversy surrounding "luxuskonsumption" may stem in part from not taking into account individual differences in aerobic capacity when measuring DIT.