Prolonged exercise in highly trained female endurance runners

The effects of prolonged exercise in a 21 degree C dry bulb and 15 degree C wet bulb environment at 65%-70% VO2max were examined in seven highly trained females. The subjects, aged 22-35 years, underwent an initial incremental treadmill test to exhaustion, with assessment of VO2max and related cardiorespiratory variables. One week later, under similar environmental conditions, subjects ran at approximately 65% VO2max for 80 min on a motor-driven treadmill. Approximately 10 ml of venous blood was withdrawn 10 min prior and immediately prior to the onset of prolonged exercise, and at 20, 40, 60, and 80 min, and 20 min post-exercise. Venous blood was analyzed for glucose, lactate, osmolality, Na+, K+, protein, and hemoglobin (Hb). Hematocrit was measured and changes in plasma volume calculated. VO2, VE, respiratory exchange ratio, and heart rate were recorded at 17, 37, and 77 min. The percent body fat estimated from skinfold thicknesses was 19 +/- 1%. The mean VO2max was 59.3 +/- 1.0 ml . kg-1 . min-1, with a mean max VE STPD and heart rate of 78.75 +/- 3.10 1 . min-1 and 175 +/- 4 beats . min-1, respectively. No significant changes occurred in VO2, VE, % VO2max, heart rate, venous lactate, plasma glucose, or plasma protein during the prolonged exercise. A significant decrease in respiratory exchange ratio was noted. Significant changes also occurred in hematocrit, Hb, Na+, K+, and osmolality. An interesting finding was the pre-exercise expansion of the plasma volume.     

Physiological variables to use in the gender comparison in highly trained runners

AIM: The aims of this investigation were to compare physiological characteristics between highly trained middle-distance and marathon male (n=17) and female (n=11) runners; to determine the most suitable variables to use in the gender comparison in these subjects, considering physical difference between genders; and to indicate some of the best predictors of performance in running events in which oxidative metabolism prevails. METHODS: Subjects performed a progressive maximal exercise on the treadmill to determine maximal oxygen uptake (VO(2max)) and velocities corresponding to a blood lactate concentration of 4 mmol x L(-1) (upsilon(OBLA)) and to the lactate threshold (upsilon(LT)). Cost of running (Cr) and maximal aerobic velocity (upsilon(a max)) were calculated from VO(2) measurements. RESULTS: Males presented higher VO(2max), upsilon(a max), upsilon(OBLA), upsilon(LT), and VO(2) @ upsilon(OBLA) and upsilon(LT) (p<0.001), but females had higher upsilon(OBLA) and upsilon(LT) (p<0.01) expressed as %VO(2max). upsilon(a max) correlated with performance time relative to the world record in both, females (r=-0.77, p<0.01) and males (r=-0.58, p<0.05); and upsilon(LT) with performance only in males (r=-0.59, p<0.05). CONCLUSION: In conclusion, female athletes seemed to compensate partly their aerobic profile with higher %VO(2max) @ u(OBLA) and u(LT), suggesting that both maximal and submaximal physiological variables should be considered when evaluating and comparing highly trained athletes of both genders. upsilon(a max) is one of the best predictors of performance in running events in which oxidative metabolism prevails.     

Potential markers of heavy training in highly trained distance runners.

Markers of a heavy increase in training were examined in ten highly trained distance runners (mean(s.d.) age 29.8(1.7) years, maximal oxygen intake 65.3 ml kg-1 min-1, personal best 10-km time 31 min 4 s) who undertook a deliberate 38% increment of training over a 3-week period. Their running performance did not improve, and six of the ten subjects developed sustained fatigue, suggesting that training was excessive, although the full clinical picture of overtraining did not develop. The Profile of Mood States was the best single marker of disturbed function, indicating increased fatigue and decreased vigour. There were no useful changes of resting heart rate or perceived exertion during submaximal running, sleep was undisturbed, and there were no orthopaedic injuries. Two subjects developed rhinoviral infections following the heavy training, and a third complained of symptoms that were diagnosed 2 weeks later as exercise-induced asthma. The increase of serum cortisol normally induced by 30 min of submaximal exercise was no longer seen when the same acute exercise was performed after heavy training. Resting lymphocyte proliferation tended to increase in response to phytohaematoglutinin (PHA) and concanavalin A (Con A), the ratio of helper to suppressor cells (H/S) decreased, and pokeweed mitogen induced smaller increases in IgG and IgM synthesis. Whereas before heavy training, PHA-stimulated lymphocyte proliferation was unchanged by 30 min of acute submaximal exercise, after 3 weeks of heavy training the same bout of exercise caused an 18% suppression of proliferation. Likewise, heavy training brought about a decrease of T-lymphocytes in response to acute submaximal exercise, but an abolition of the acute exercise-induced decrease in the H/S ratio. The previously observed exercise-induced decrease of IgG synthesis did not occur when the same acute bout of exercise was performed after heavy training. We conclude that such minor and transient changes of immune function may possibly be a warning that training is becoming excessive, but they have only a limited significance for overall immune function.     

Effects of beta-hydroxy-beta-methylbutyrate and creatine monohydrate supplementation on the aerobic and anaerobic capacity of highly trained athletes

AIM: The aim of this study was to investigate the effects of 6 wks oral supplementation of beta-hydroxy-beta-methylbutyrate (HMB) and a mixture of HMB and creatine monohydrate (HMBCr) on aerobic and anaerobic capacity in highly trained athletes. It was hypothesised that HMB and HMBCr would have positive effects on aerobic and anaerobic power. METHODS: A prospective study involving a repeated measures design was utilised where subjects underwent testing prior to, and immediately after, a 6 wks supplementation period. Elite, male rugby league players (n=27) were divided into 3 groups, a control group (n=6), a HMB group (3 g/d; n=10) and a HMBCr group (3 g/d HMB + 3 g/d Cr; n=11). Testing involved a multistage fitness test to determine aerobic power and a 60 sec maximal cycle test to determine anaerobic capacity. Peak power, total work and peak lactate levels were measured in the anaerobic cycle test. RESULTS: Two-way repeated measures ANOVA revealed no effect of HMB or HMBCr on any of the measured parameters in comparison to the control group. CONCLUSION: Aerobic and anaerobic ability of highly trained male athletes is unaffected by 6 wks oral supplementation with HMB or a combination of HMB and creatine monohydrate.     

Influence of body mass and height on the energy cost of running in highly trained middle- and long-distance runners

Previous studies about the influence of body dimensions on running economy have not compared athletes specialized in different competition events. Therefore, the purpose of the present study was to assess the influence of body mass (m(b)) and height (h) on the energy cost of running (Cr) in 38 highly trained male runners, specialized in either marathon (M, n = 12), long middle-distance (5000 - 10000 m, LMD, n = 14) or short middle-distance (800 - 1500 m, SMD, n = 12), and to assess possible differences in body dimensions for each event. Subjects performed a progressive maximal exercise on the treadmill to determine oxygen uptake VO(2)) at different submaximal velocities and maximal oxygen uptake VO(2)max). Cr was calculated from VO(2) measurements. LMD runners had significantly higher mean Cr (0.192 +/- 0.007, 0.182 +/- 0.009, and 0.180 +/- 0.009 ml O(2) x kg(-1) x m(-1) for LMD, M and SMD, respectively) and VO(2)max (74.1 +/- 3.7, 68.5 +/- 2.9 and 69.7 +/- 3.4 ml x kg (-1) x min (-1)). Cr correlated with h (r = -0.86, p < 0.001) and m(b) (r = -0.77, p < 0.01) only in the SMD group. In conclusion, these data suggest that highly trained distance runners tend to show counterbalancing profiles of running economy and VO(2)max (the higher Cr, the higher VO(2) max and vice versa), and that anthropometric characteristics related with good performance are different in long-distance and middle-distance events.     

Factors affecting running economy in trained distance runners

Running economy (RE) is typically defined as the energy demand for a given velocity of submaximal running, and is determined by measuring the steady-state consumption of oxygen (VO2) and the respiratory exchange ratio. Taking body mass (BM) into consideration, runners with good RE use less energy and therefore less oxygen than runners with poor RE at the same velocity. There is a strong association between RE and distance running performance, with RE being a better predictor of performance than maximal oxygen uptake (VO2max) in elite runners who have a similar VO2max). RE is traditionally measured by running on a treadmill in standard laboratory conditions, and, although this is not the same as overground running, it gives a good indication of how economical a runner is and how RE changes over time. In order to determine whether changes in RE are real or not, careful standardisation of footwear, time of test and nutritional status are required to limit typical error of measurement. Under controlled conditions, RE is a stable test capable of detecting relatively small changes elicited by training or other interventions. When tracking RE between or within groups it is important to account for BM. As VO2 during submaximal exercise does not, in general, increase linearly with BM, reporting RE with respect to the 0.75 power of BM has been recommended. A number of physiological and biomechanical factors appear to influence RE in highly trained or elite runners. These include metabolic adaptations within the muscle such as increased mitochondria and oxidative enzymes, the ability of the muscles to store and release elastic energy by increasing the stiffness of the muscles, and more efficient mechanics leading to less energy wasted on braking forces and excessive vertical oscillation. Interventions to improve RE are constantly sought after by athletes, coaches and sport scientists. Two interventions that have received recent widespread attention are strength training and altitude training. Strength training allows the muscles to utilise more elastic energy and reduce the amount of energy wasted in braking forces. Altitude exposure enhances discrete metabolic aspects of skeletal muscle, which facilitate more efficient use of oxygen. The importance of RE to successful distance running is well established, and future research should focus on identifying methods to improve RE. Interventions that are easily incorporated into an athlete's training are desirable.     

Daily variation in running economy of moderately trained male runners

The purpose of this study was to quantify total within-subject variation in running economy (RE) in moderately trained male runners (N = 10). Subjects (ages 20-34 yr) were monitored during treadmill running, five times a week (Mon-Fri) for 4 wk, at 2.68, 3.13, and 3.58 m.s-1. Oxygen consumption (VO2) was determined via the open-circuit method during each of the three running paces. Coefficients of variation among the three paces were not significantly (P greater than 0.05) different. An analysis of variance with repeated measures and a three-factor (3 x 4 x 5) design indicated that speed was the only significant (P less than 0.05) effect. Reliability tests performed on the data indicated that although there is an improvement in the percentage of variation accounted for as the number of tests conducted is increased, the benefit obtained by testing 5 d is very small when compared with testing 2 d. When effect sizes are used in the determination of subject numbers needed to detect significant effects, it is apparent that smaller anticipated effect sizes necessitate large sample sizes. In conclusion, RE appears to be a stable physiological measure in moderately trained male runners, and a criterion value based on the average of two measures per subject is recommended to obtain an acceptably stable RE value.     

Aerobic exercise adaptations in trained adolescent runners following a season of cross-country training

Adaptations in aerobic exercise responses as well as the relationship between aerobic exercise responses and running performance were examined in a group of previously trained adolescent runners (n = 9; 15.9 +/- 1.0 years) over the course of a competitive cross-country season. Running economy (RE), submaximal blood lactate concentration [BLa] and VO2max were assessed before and immediately after the season. Five-km race time improved (P < 0.05) from 18.68 +/- 1.10 min at the beginning of the season to 18.16 +/- 1.11 min at the end of the season. Significant increases were observed in peak VO2 (61.6 +/- 3.5 to 65.3 +/- 2.9 mL x kg(-1) x min(-1)) and graded exercise test time (11.32 +/- 1.56 to 12.22 +/- 0.79 min). There was a tendency for RE (P = 0.051) to worsen slightly and for [BLa] (P = 0. 057) to decline as a result of training. At the beginning of the season submaximal [BLa] at 14 km x hr(-1) (r = 0.86) and graded exercise test time (r = -0.87) were significantly related to 5-km time. At the end of the season, RE (r = 0.78) and [BLa] (r = 0.77) at 14 km x hr(-1) and graded exercise test time (r = -0.69) were significantly related to race time. In this well-trained group of runners, further training during the cross-country season increased peak VO2 and improved race time. Submaximal [BLa] and graded exercise test time appear to be the most robust predictors of performance, while RE became a significant predictor of race time at the end of the season.     

Mood state and running economy in moderately trained male runners

The purpose of this study was to determine the relationship between psychological states as measured by the Profile of Mood States (POMS) inventory and within-subject variation in running economy (RE) in moderately trained male runners (N = 10). Subjects (ages 20-34 yr) were monitored during treadmill running, five times a week (Monday through Friday) for 4 wk, at 2.68, 3.13, and 3.58 m, s-1. Tension, depression, anger, vigor, fatigue, confusion, and a total mood disturbance (TMD) score were assessed every Friday prior to the treadmill running sessions. Oxygen consumption (VO2) was determined via the open-circuit method during each of the three running paces. VO2 values were averaged over 5 d and three speeds for each week (RE) and were correlated with the weekly TMD scores, resulting in a nonsignificant group correlation of r = -0.28. The within-subject group correlation between TMD scores and RE was r = 0.88. This positive correlation indicates that, when the focus of attention was on within-subject variation, weeks featuring more economical values were associated with more positive mental health profiles. Correlations between average VO2 and the six POMS subscales were tension. r = 0.81; depression, r = 0.73; anger, r = 0.58; vigor, r = -0.60: fatigue, r = 0.18; and confusion, r = 0.60. All correlation coefficients except for fatigue were significantly (P less than 0.01) related to average VO2. In conclusion, it appears that short-term fluctuations in RE of moderately trained male runners are closely tied to their mood state.     

Variability in running economy and mechanics among trained male runners

Data from two studies were analyzed to quantify intraindividual variability and reliability in running economy (RE) and mechanics. Following 30-60 min of treadmill accommodation, stride-to-stride and day-to-day biomechanical stability were assessed in 31 male runners (studies 1 and 2) who performed two level treadmill runs (3.33 m.s-1) at the same time of day, in the same footwear, and in a nonfatigued state. Under the same testing conditions, daily stability in RE was determined in 17 of the 31 subjects (study 2). RE demonstrated high day-to-day reliability (r = 0.95), and the mean coefficient of variation in RE was 1.32% (range = 0.30-4.40%). Stride-to-stride reliability for temporal (T), kinematic (KNM), and kinetic (KIN) measures was very high (mean r = 0.96; range = 0.91-0.99), but day-to-day reliability was lower for KIN (mean r = 0.67; range = 0.28-0.88) compared with T and KNM (mean r = 0.91; range = 0.68-0.98). Further analyses revealed no significant (P less than or equal to 0.05) mean stride-to-stride differences for any biomechanical variable, and only three of 22 variables (peak resultant velocity of the ankle joint, step length, and swing time) demonstrated statistically significant day-to-day differences. Viewed in concert, these results suggest that, if the testing environment is controlled, multiple trials are not required to obtain stable measures of running economy and basic mechanical characteristics in trained male runners if group data from adequate sample sizes are considered. However, if individual records are scrutinized or if small sample sizes cannot be avoided, at least two measures of individual performances should be secured.     

Oxygen cost and energy expenditure of running in trained runners.

The oxygen cost and energy expenditure of submaximal treadmill running was evaluated in 9 male distance runners. The oxygen consumption--running speed relationship was highly significant (r = .917) and linear over the entire aerobic range. The caloric cost of 0.97 Kcal/kg/k was in close agreement with values found in the literature and was independent of running speed. The caloric cost per unit distance and time increased with acceleration in running speed. The slope of the regression line of oxygen consumption on running speed appear to measure a different component of efficiency than the fractional utilization coefficient of aerobic capacity. There is apparently a wide variation in the oxygen cost of running in trained runners.     

Effects of acute exercise on plasma erythropoietin levels in trained runners

PURPOSE: The purpose of this study was to investigate further the influence of exercise on erythropoietin. METHODS: We observed the effects of high intensity running on plasma erythropoietin concentration in competitive distance runners. A repeated measures design was used to compare the responses of intermittent high intensity (HIGH) exercise to continuous moderate intensity (MOD) exercise and rest (REST). The HIGH treatment consisted of 60 min of exercise alternating 5 min of running at approximately 90% of VO2max with 5 min of brisk walking. The MOD treatment consisted of a continuous 60-min run on the treadmill at 60% of VO2max. Blood samples were collected immediately before the exercise (PRE), immediately following the exercise (POST), and 4 (heart rate (4HR), 12 (12HR), 24 (24HR), and 48 (48HR)) h following the exercise. The variables examined included plasma erythropoietin concentration ([EPO]), hemoglobin (Hb) concentration ([Hb]), hematocrit (Hct), red blood cell count (RBC), and mean corpuscular volume (MCV). RESULTS: ANOVA revealed the expected treatment-by-time interaction for Hct and [Hb] suggesting a hemodilution at 24 and 48 h postexercise for the MOD and HIGH treatments. However, no significant treatment-by-time interactions were observed for [EPO], RBC, or MCV. CONCLUSION: These results indicate that intermittent high intensity exercise does not have a significant effect on [EPO] in trained distance runners.     

Exercise-induced hypoxaemia in highly trained athletes

Traditionally, the pulmonary system has not been considered the limiting factor in determining maximal oxygen uptake (VO2max) in healthy individuals since arterial oxygen-haemoglobin saturation is thought to remain high during intense exercise. However, there appears to be a major exception to this rule. Recent evidence suggests that arterial hypoxaemia results during heavy exercise in well trained individuals with a high VO2max. Further, the degree of arterial desaturation is inversely related to VO2max. This exercise-induced hypoxaemia does not appear to be due to hypoventilation although athletes who have limited hyperventilation seem to exhibit the lowest arterial oxygen-haemoglobin saturation. A significant venoarterial shunt has been ruled out as a primary cause of the hypoxaemia based on both experimental and theoretical considerations. Therefore, it appears that the exercise-induced hypoxaemia seen in highly trained athletes during heavy exercise is primarily due to diffusion limitations and ventillation-perfusion inequality. It is postulated that incomplete diffusion in the healthy lung may be due to a rapid red blood cell transit time through the pulmonary capillary. In summary, recent findings suggest that the limits of the human pulmonary system may be reached or even exceeded during intense exercise in some individuals. In light of these findings the role of the pulmonary system as a limiting factor during maximal exercise in the highly trained endurance athlete warrants further investigation.     

Chronic medium-chain triacylglycerol consumption and endurance performance in trained runners.

BACKGROUND: This study was designed to assess the effects of chronic consumption of medium-chain triacylglycerols (MCT) on endurance running performance. METHODS: Experimental design: participants completed the study in a randomized, cross-over, placebo-controlled, double-blind fashion. Setting: participants were recruited from the general community to participate in this university based study. Participants: twelve trained male endurance runners (30.5+/-5.2 years of age) completed the study. Interventions: participants consumed dietary supplements containing either 56 g of corn oil (LCT) or 60 g of MCT oil daily for 2 weeks. Following each dietary phase, participants completed a maximal treadmill test followed by an endurance treadmill test in which participants ran at 85% VO2max for 30 min proceeded by 75% VO2max until exhaustion. Measures: blood was taken at rest and after 45 min of exercise to assess concentrations of lactate, glucose, beta-hydroxybutyrate (beta-HBA), free fatty acids (FFA), glycerol and triacylglycerols (TG). Performance was assessed as time to exhaustion. RESULTS: VO2max (72.0+/-8.0 vs 72.4+/- 9.0 ml x kg(-1) x min(-1)) and endurance time (99.8+/-23.5 vs 106.5+/-29.4 min) did not differ (p>0.05) between MCT and LCT trials, respectively. No differences (p>0.05) in lactate, glucose, beta-HBA, FFA, glycerol or TG were detected between trials. Respiratory exchange ratio (RER) was higher (p<0.05) at 15 min for the MCT trial (0.97+/-0.10) versus the LCT trial (0.90+/-0.20), but was similar between trials at other timepoints. CONCLUSIONS: Results indicate that chronic MCT consumption neither enhances endurance nor significantly alters performance-related metabolism in trained male runners.