Post-exercise Blood Lactate Concentration Research Articles

The effects of changing pace on metabolism and stroke characteristics during high-speed breaststroke swimming

Performances often vary between the heats and finals of breaststroke swimming competitions possibly because the swimmers try to conserve their energy, or for other tactical reasons. Additionally, coaches might advise either a ‘positive’ or ‘even’ pace race strategy during the final. The effect of such pacing changes on metabolism (blood lactate, heart rate, ventilation), ratings of perceived exertion, stroke kinematics and turning times have not been investigated. Nine male competitive breaststroke swimmers swam three paced (Aquapacer™) 200-m trials, 48 h apart and in random order, at 98%, 100% and at an attempted 102% of their maximal 200-m time-trial speed. Responses in metabolic variables were similar between the 98% and 100% trials, but higher post-exercise blood lactate concentrations and respiratory exchange ratios were observed following the 102% trial. As the pace of trials increased, stroke rate was found to increase proportionately with stroke count. However, during the latter stages of the 100% trial, a disproportionate increase in the stroke count was observed, which led to a significant pacing error. This feature was more obvious in the 102% trial, where participants demonstrated ‘positive pacing’ and reported higher ratings of perceived exertion than for the 98% trial. During the early stages of the trials, turning times were initially shorter the faster the pace of the trial; however, as the trials progressed, this pattern was found to reverse. We conclude that a slight reduction in pace during near maximal breaststroke swimming altered kinematic but not post-exercise metabolic responses, while an increase in pace led to positive pacing and an increase in both kinematic responses and anaerobic metabolism.

Climbing-specific finger endurance: a comparative study of intermediate rock climbers, rowers and aerobically trained individuals

The aim of this study was to compare the climbing-specific finger endurance of climbers, rowers and aerobically leg trained athletes. Twenty-seven males aged 21.2±2.2 years (mean±s) volunteered for the study. The participants were intermediate rock climbers (n = 9), rowers (n = 9) and leg trained athletes (n = 9). Maximal voluntary contraction (MVC) was determined on climbing-specific finger apparatus. Endurance isometric exercise was performed at 40% MVC in three tests performed in a random order: (1) sustained exercise; (2) 6 s exercise, 4 s rest; and (3) 18 s exercise, 12 s rest. Pre- and post-exercise blood pressure and blood lactate concentration, together with post-exercise pain perception, were measured. The climbers had a significantly greater MVC (383±35.6 N) than the rowers (321±49.5 N, P = 0.007) and aerobically leg trained athletes (288±60.6 N, P = 0.001). There were no significant differences between the groups in terms of endurance times for any of the tests. In the test with 18 s exercise and 12 s rest, the climbers showed a significantly higher increase in blood lactate concentration, on average, than the rowers by 0.01-0.89 mmol · l−1 (P = 0.006); there were no significant differences, on average, in the comparisons of climbers and the leg trained athletes and rowers and the leg trained athletes. There were no significant differences in the average changes in blood pressure from rest to post-exercise between any of the groups. Although the climbers had greater MVC on average than the other two groups, there were no significant differences in average endurance times among the groups. These findings suggest that training for rock climbing and participation in rock climbing may result in some specific adaptations. However, we acknowledge that this study is descriptive and there is the possibility that differences between groups could be attributed to self-selection.

Effect of paddling cadence on time to exhaustion and VO2 kinetics at the intensity associated with VO2max in elite white-water kayakers.

The influence of paddling cadence on the time to exhaustion (t.lim) and VO2 kinetics at the intensity associated with VO2max (IVO2max) was examined in seven highly-trained white water kayakers. All subjects were engaged in national or international competitions. Subjects took part in three constant-load tests at IVO2max, each test performed at a different paddling cadence (50, 60 or 70 cycles min(-1). The VO2 kinetics recorded during these constant-load tests at IVO2max were fitted with a mono-exponential equation. A significant increase in t.lim (P <.05) was observed as the paddling cadence increased from 50 to 70 cycles min(-1). No effect was found either on values of VO2peak, post-exercise blood lactate concentration, or on the time at which VO2peak was attained (TAVO2peak). Our results suggest that experienced kayakers may choose a high paddling cadence during physiological assessments at IVO2max. Further experiments are needed in order to identify the physiological significance of t.lim at IVO2max.

Changes in physiological parameters in overtrained Standardbred racehorses.

Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial increased by 4.0% (95% probable range of true value 1.7-5.8) and peak velocity decreased by 6.9% (4.7-8.9), indicating that overtraining had occurred. Acute overtraining coincided with an increase in blood lactate concentration after the time trial and submaximal test. There were also substantial decreases in bodyweight, plasma cortisol concentration and packed cell volume after the time trial, and in the velocity at a heart rate of 200/min (V200). Parameters that showed no clear-cut change with overtraining included maximal and recovery heart rate, basal plasma cortisol, plasma and red cell volume, and markers of skeletal damage (plasma concentrations of creatine kinase and aspartate aminotransferase). Bodyweight, V200, postexercise blood lactate and plasma cortisol concentrations may all be useful for detecting acute overtraining in equine athletes.

Clinical Effects of a Dietary Antioxidant Silicate Supplement, Microhydrin((R)), on Cardiovascular Responses to Exercise.

Amorphous silicate minerals, often described as rock flour, were once common in natural water sources and abundant in glacial stream waters. Not only do the silica mineral particles bond water and other elements for transport; they also can be adsorbed with reduced hydrogen, which releases electrons, providing antioxidant or reducing potential to surrounding fluids. The purpose of this investigation was to examine the cardiovascular responses during exercise after consumption of a dietary silicate mineral antioxidant supplement, Microhydrin((R)) (Royal BodyCare, Inc., Irving, TX). A clinical trial incorporating a double-blind, placebo-controlled, crossover experimental design was employed. Subjects received either active agent or placebo, four capsules per day, for 7 days before the trial. The trial evaluated six exercise bicycle-trained subjects performing a 40-km bicycling time trial. Ratings of perceived exertion and measurements of oxygen uptake, heart rate, performance workload, and preexercise and postexercise blood lactate concentrations were obtained. Although there were no differences (P >/=.05) in work performed, heart rate, oxygen uptake, and ratings of perceived exertion during the time trial, the postexercise blood lactate concentrations were significantly lower (P </=.05) when the silicate mineral supplement was used, compared with placebo. These data suggest a beneficial effect of Microhydrin on lactate metabolism.

The effect of recovery duration on running speed and stroke quality during intermittent training drills in elite tennis players

The aim of this study was to assess the effect of the recovery duration in intermittent training drills on metabolism and coordination in sport games. Ten nationally ranked male tennis players (age 25.3±3.7 years, height 1.83±0.8 m, body mass 77.8±7.7 kg; mean ±s x ) participated in a passing-shot drill (baseline sprint with subsequent passing shot) that aimed to improve both starting speed and stroke quality (speed and precision). Time pressure for stroke preparation was individually adjusted by a ball-machine and corresponded to 80% of maximum running speed. In two trials (T10, T15) separated by 2 weeks, the players completed 30 strokes and sprints subdivided into 6 2 5 repetitions with a 1 min rest between series. The rest between each stroke-and-sprint lasted either 10 s (T10) or 15 s (T15). The sequence of both conditions was randomized between participants. Post-exercise blood lactate concentration was significantly elevated in T10 (9.04±3.06 vs 5.01±1.35 mmol·l-1, P ≪ 0.01). Running time for stroke preparation (1.405±0.044 vs 1.376±0.045 s, P ≪ 0.05) and stroke speed (106±12 vs 114±8 km·h-1, P ≪ 0.05) were significantly decreased in T10, while stroke precision - that is, more target hits ( P ≪ 0.1) and fewer errors (P ≪ 0.05) - tended to be higher. We conclude that running speed and stroke quality during intermittent tennis drills are highly dependent on the duration of recovery time. Optimization of training efficacy in sport games (e.g. combined improvement of conditional and technical skills) requires skilful fine-tuning of monitoring guidelines.

Physiological responses that account for the increased power output in speed skating using klapskates.

The present study investigates which physiological sources support the increase in mechanical power output (W out) that can be obtained using klapskates in speed skating. It was hypothesized that the increase in W out could be achieved through an increase in gross efficiency or an increase in aerobic power (W aer). Six speed skaters performed a submaximal and maximal 1,600-m skating test with both klapskates and conventional skates, to measure gross efficiency and maximal W aer during speed skating. The rate of oxygen uptake (VO2) and post-exercise blood lactate concentrations ([La]) were measured and video recordings were made. W aer was calculated from VO2. W out was derived from the power needed to overcome air and ice friction. Gross efficiency was calculated as the ratio of W out and W aer. In the maximal tests, the subjects skated faster with klapskates compared to conventional skates (10.0 vs 9.6 m x s(-1)). They sustained the resulting higher W out with klapskates with an equal VO2. [La] was, however, 1.7 mmol x l(-1) higher when klapskates were used, which might reflect an increase in anaerobic power. During the submaximal tests the skaters generated equal W out with both types of skate. Although not statistically significant, VO2 and W aer were, on average, lower when klapskates were used compared to conventional skates [mean (SD) 0.3 (0.43) l x min(-1), 105 (143) W]. Despite the lack of a statistically significant difference in W aer, gross efficiency was shown to be significantly higher with klapskates compared to conventional skates (16.3% vs 14.8%, P = 0.02). We conclude that the increase in W out when the subjects were using klapskates could be explained by an increase in gross efficiency rather than an increase in W aer.

Plasma catecholamine responses and neural adaptation during short-term resistance training.

Low exercise-induced plasma adrenaline (A) responses have been reported in resistance-trained individuals. In the study reported here, we investigated the interaction between strength gain and neural adaptation of the muscles, and the plasma A response in eight healthy men during a short-term resistance-training period. The subjects performed 5 resistance exercises (E1-E5), consisting of 6 sets of 12 bilateral leg extensions performed at a 50% load, and with 2 days rest in between. Average electromyographic (EMG) signal amplitude was recorded before and after the exercises, from the knee extensor muscles in isometric maximal voluntary contraction (MVC) as well as during the exercises (aEMGmax and aEMGexerc, respectively). Total oxygen consumed during the exercises (VO2tot) was also measured. All of the exercises were exhaustive and caused significant decreases in MVC (34-36%, P < 0.001). As expected, the concentric one-repetition maximum (1-RM), MVC and aEMGmax were all higher before the last exercise (E5) than before the first exercise (E1; 7, 9 and 19%, respectively, P < 0.05). In addition, in E5 the aEMGexerc:load and VO2tot:load ratios were lower than in E1 (-5 and -14%, P < 0.05), indicating enhanced efficiency of the muscle contractions, However, the post-exercise plasma noradrenaline (NA) and A were not different in these two exercises [mean (SD) 10.2 (3.8) nmol x l(-1) vs 11.3 (6.0) nmol x l(-1), ns, and 1.2 (1.0) nmol x l(-1) vs 1.9 (1.1) nmol x l(-1), ns, respectively]. However, although NA increased similarly in every exercise (P < 0.01), the increase in A reached the level of statistical significance only in E1 (P < 0.05). The post-exercise A was also already lower in E2 [0.7 (0.7) nmol x l(-1), P < 0.05) than in E1, despite the higher post-exercise blood lactate concentration than in the other exercises [9.4 (1.1) mmol x l(-1), P < 0.05]. Thus, the results suggest that the observed attenuation in the A response can not be explained by reduced exercise-induced strain due to the strength gain and neural adaptation of the muscles. Correlation analysis actually revealed that those individuals who had the highest strength gain during the training period even tended to have an increased post-exercise A concentration in the last exercise as compared to first one (r = 0.76, P < 0.05).

A Nonmotorized Treadmill Test to Assess Children’s Short-Term Power Output

The purpose of this study was to develop a nonmotorized treadmill sprint test (ExNMT) to assess children’s short-term power output, to establish the test’s repeatability, and to compare the results to corresponding Wingate anaerobic test (WAnT) measurements. Nineteen children (aged 10.9±0.3 years) completed 2 ExNMTs and 2 WAnTs. Statistical analysis revealed coefficients of repeatability for the ExNMT that compared very favorably with the WAnT for both peak power (26.6 vs. 44.5 W) and mean power (15.3 vs. 42.1 W). The validity of the ExNMT as a test of anaerobic performance is reflected by significant correlations (p ≤.05) with the WAnT (peak power, r = 0.82; mean power, r = 0.88) and reinforced by the relatively high post-exercise blood lactate concentrations (7.1 ± 1.3 vs. 5.6 ± 1.5 mmol · L−1 for the ExNMT and WAnT, respectively). This study has developed a promising laboratory running test with which to examine young people’s short-term power output.

Prolonged incremental tests do not necessarily compromise V̇O 2max in well-trained athletes

Existing literature suggests that tests for maximal oxygen uptake (VO2max) should last 8-12 minutes and that prolonged tests do not produce valid measurements. The research underlying this suggestion has been performed with non-athletic populations and trained athletes may be more tolerant of longer protocols. Eleven rowers (8 males, 3 females) each underwent four different incremental tests on a standard rowing ergometer in randomised counterbalanced order. One of the tests was continuous with workload increments each minute (IT1MIN). This test lasted an average of 12 min+/-4 s (SEM). The other three tests were discontinuous and consisted of 7 stages separated by 1-minute recovery intervals. Stage durations of 3, 4 and 5 min were used in the different tests (IT3MIN, IT4MIN and IT5MIN). Mean values for VO2max were almost identical for IT1MIN (4.56+/-0.22 L x min(-1)), IT3MIN (4.60+/-0.23 L x min(-1)) and IT4MIN (4.60+/-0.21 L x min(-1)), while IT5MIN produced a significantly lower value (4.47+/-0.21 L x min(-1), p<0.05). There was no significant difference between protocols in peak post-exercise blood lactate concentration (approx 13 mmol x L(-1) in each case), but IT1MIN produced lower peak heart rates and higher respiratory exchange ratios. We conclude that with well trained rowing athletes discontinuous test protocols involving 7 stages of 3-4 minutes duration can provide valid measurements of VO2max.

Exercise-induced cerebral deoxygenation among untrained trekkers at moderate altitudes.

The pathophysiology of altitude-related disorders in untrained trekkers has not been clarified. In the present study, the effects of workload on cardiovascular parameters and regional cerebral oxygenation were studied in untrained trekkers at altitudes of 2700 m and 3700 m above sea level. We studied 6 males and 4 females at each altitude, and their average ages were 31.3+/-7.1 y at 2700 m and 31.2+/-6.8 y at 3700 m, respectively. The resting values of heart rate and mean blood pressure were not significantly different at 2700 m and 3700 m than at sea level. However, increases in these values after exercise were more prominent at high altitudes (heart rate increase = 51.6% at 2700 m and 70.4% at 3700 m; mean blood pressure increase: 19.0% at 2700 m and 17.2% at 3700 m). In addition, post-exercise blood lactate concentration was significantly higher at 3700 m than at sea level or at 2700 m (i.e., 7.6 mM at 3700 m, 3.8 mM at 2700 m, and 4.17 mM at 0 m, respectively). Exercise induced an acute reduction in the arterial oxygen saturation value (SpO2) at 2700 m and 3700 m (i.e., 11.2% reduction at 2700 m and 9.4% at 3700 m), whereas no changes were observed at sea level. The resting values of regional oxygen saturation (rSO2)--measured by a near infra-red spectrophotometer at sea level, 2700 m, and 3700 m-were nearly identical. Exercise at sea level did not reduce this value. In contrast, we observed a decrease in rSO2 after subjects exercised at 2700 m and 3700 m (i.e., 26.9% at 2700 m and 48.1% at 3700 m, respectively). The rSO2 measured 2 min and 3 min after exercise at 3700 m was significantly higher than the preexercise value. From these observations, we concluded that alterations in cardiovascular parameters were apparent only after an exercise load occurred at approximately 3000 m altitude. Acute reduction in cerebral regional oxygen saturation might be a primary cause of headache and acute mountain sickness among unacclimatized trekkers.

Anaerobic Power of the Arms and Legs of Young and Older Men

The purpose of this study was to examine differences in the anaerobic exercise performance of young and older men. Eight healthy, active older (68.5 +/- 2.4 years old, mean S.D.) and eight healthy, active young (30.6 +/- 4.5 years old) subjects were assessed for peak and mean power output (PP and MP, respectively) of the legs and arms, during 30 s Wingate tests. PP during leg exercise was significantly (P < 0.05) higher in the young (14.6 +/- 1.6 W kg-1) compared with the older (10.7 +/- 1.0 W kg-1) group. MP of the legs was also greater in the young subjects (10.7 +/- 0.7 vs. 7.4 +/- 0.9 W kg-1). These differences in PP and MP remained significant when expressed relative to lean leg volume. PP during arm cranking was significantly greater in the young subjects (8.9 +/- 0.7 vs. 7.5 +/- 0.6 W kg-1) as was MP (6.4 +/- 0.7 vs. 5.0 +/- 0.7 W kg-1). Post-exercise blood lactate concentration in the older group (7.0 +/- 1.6 mmol l-1) was less (P < 0.05) than in the young group (10.6 +/- 2.0 mmol l-1), for leg work only. The significant loss of anaerobic power in the older group could not be explained by a difference in muscle mass. Power output was also lower in the arms, but to a lesser extent. The results of this study suggest that a reduction in the ability to perform high intensity exercise may be an inevitable consequence of ageing. The extent, however, of this decline varies with different muscle groups.

Isokinetic Exercise Velocities and Blood Lactate Concentrations in Strength/Power and Endurance Athletes

We examined the effect of different isokinetic exercise velocities on blood lactate concentration in strength/power (SP) and endurance (EN) athletes. Ten SP athletes (96.8 6 16.2 kg) and 10 EN athletes (70.1 6 9.4 kg) performed 20 maximal isokinetic knee extensions and flexions at 3 velocities (1.05, 2.09, and 5.23 rad·s21 ) on an isokinetic dynamometer. Trials were randomly assigned and separated by at least 48 hours. Capillary blood samples (150 ml) were collected before and 2, 4, and 6 minutes after exercise. Significant differences were observed for blood lactate concentrations among velocities for SP athletes with postexercise values at 1.05 rad·s21 (2 minutes, 6.64 6 0.46; 4 minutes, 6.87 6 0.50; 6 minutes, 6.34 6 0.39 mmol·L 21 ) and 2.09 rad·s 21 (2 minutes, 6.49 6 0.30; 4 minutes, 6.57 6 0.34; 6 minutes, 6.67 6 0.45 mmol·L21 ) higher than 5.23 rad·s 21 (2 minutes, 5.40 6 0.30; 4 minutes, 5.46 6 0.33; 6 minutes, 5.40 6 0.32 mmol·L 21 ). No significant difference was observed in blood lactate concentrations among velocities for EN. The postexercise blood lactate concentrations were significantly higher for SP athletes compared with EN athletes at each velocity; however, this difference was eliminated when corrected for body mass. Total work was significantly greater for SP athletes compared with EN athletes at each velocity. Total work performed by both SP and EN athletes was significantly higher at 1.05 and 2.09 rad·s21 compared with 5.23 rad·s 21 . The data indicate that SP athletes will produce the highest blood lactate concentrations when using slower isokinetic velocities, which may be due to the total amount of work performed.

Rate pressure product and oxygen saturation in tourists at approximately 3000 m above sea level.

Using modern transportation technology, many travelers easily access moderate altitudes of approximately 3000 m above sea level. In the present study the effects of this altitude on cardiovascular parameters were studied among office workers dwelling at sea level. Heart rate, blood pressure, arterial oxygen saturation (SpO2), and electrocardiography were monitored before and after Master's double-step exercise at 2700 and 3700 m. The test consisted of stepping onto and off of two 23-cm steps for 3 min at a predefined rate. The resting values recorded for the heart rate and mean blood pressure at 2700 and 3700 m did not statistically significantly differ from those noted at sea level. However, the increases in these values after exercise were significantly greater at high altitude. The rate pressure product more than doubled after exercise at 3700 m. Electrocardiographic abnormalities were observed in some cases. The postexercise blood lactate concentration was significantly higher at 3700 m than at sea level or at 2700 m, suggesting that the oxygen supply-demand relationship was not balanced at this altitude. Furthermore, exercise provoked an acute reduction in SpO2 at 2700 and 3700 m but showed no effect at sea level. These observations suggest that the oxygenation status of the heart might be at risk in many travelers and workers during and after exercise load at an altitude of approximately 3000 m.

The Assessment of Children’s Anaerobic Performance Using Modifications of the Wingate Anaerobic Test

Twenty-five girls and 25 boys (mean age 9.7 ± 0.3 years) each completed a 20- and 30-s Wingate Anaerobic Test (WAnT). Oxygen uptake during the WAnTs, and postexercise blood lactate samples were obtained. Inertia and load-adjusted power variables were higher (18.6–20.1% for peak, and 6.7–7.5% for mean power outputs, p &lt; .05) than the unadjusted values for both the 20- and 30-s WAnTs. The adjusted peak power values were higher (7.7–11.6%, p &lt; .05) in both WAnTs when integrated over 1-s than over 5-s time periods. The aerobic contributions to the tests were lower (p &lt; .05) in the 20-s WAnT (13.7–35.7%) than in the 30-s WAnT (17.7–44.3%) for assumed mechanical efficiencies of 13% and 30%. Postexercise blood lactate concentration after the WAnTs peaked by 2 min. No gender differences (p &gt; .05) in anaerobic performances or peak blood lactate values were detected.

Influence of test duration and event specificity on maximal accumulated oxygen deficit of high performance track cyclists.

This study examined the relationship between the time required to fully utilise the maximal accumulated oxygen deficit (MAOD) and event specificity of track cyclists. Twelve track endurance and 6 sprint high performance track cyclists performed four treatments of 70 s, 120 s, 300 s and 115% VO2max of maximal cycling on an air-braked ergometer. Peak blood lactate was measured immediately after each test with VO2 kinetics being assessed during the 115% VO2max time to exhaustion test. When the two cycling groups were combined there was no significant difference in the MAOD when assessed under the four different exercise durations. However, when the groups were analysed separately the following results were apparent: (1) the sprint cyclists achieved a significantly greater MAOD (66.9 +/- 2.2 ml.kg-1) compared to the track endurance cyclists (57.6 +/- 6.7 ml.kg-1) when a 70 s test duration was employed (2) even though the track endurance cyclists achieved their greatest MAOD during the 300 s test protocol (62.1 +/- 11.0 ml.kg-1), it was not significantly different to the MAOD's measured during the three other test durations and (3) the sprint cyclists recorded their greatest MAOD during the 70 s supramaximal test protocol (66.9 +/- 2.2 ml.kg-1). This was not significantly different to the 120 s test MAOD, but it was significantly higher than the MAOD values recorded during the 115% VO2max and 300 s test durations. There was no significant difference between the two groups in the peak post-exercise blood lactate concentrations for any of the tests and only the 70 s test produced a significant correlation between peak blood lactate and the MAOD. The VO2 kinetics (VO2 t1/2) of the sprinters was significantly slower than that of the track endurance cyclists (26.3 +/- 2.3 vs 23.9 +/- 2.8 s.). The findings of this study demonstrate that sprint cyclists can fully express their anaerobic capacity within an event specific 70 s all-out test and that these cyclists progressively decrease their anaerobic capacity during a 120 s, 115% VO2max (mean time = 210 s) or 300 s test, despite giving all-out efforts. Conversely, track endurance cyclists achieve their highest mean score during an event specific 300 s test and their lowest during a 70 s test. These findings have important implications when testing high performance cyclists for determination of MAOD, with the implication that it is necessary to assess MAOD under exercise conditions (i.e., duration, pacing) specific to the cyclist's chosen event.

Time course of anaerobic and aerobic energy expenditure during short-term exhaustive running in athletes.

The aim of the present study was to investigate the time course of aerobic and anaerobic energy yield during supramaximal exhaustive running on the treadmill in sprint and endurance athletes. In addition, the relationships between O2 deficit, excess post-exercise O2 consumption (EPOC) and peak post-exercise blood lactate concentration (peak BLa) values were examined, Oxygen uptake during the exhaustive run and 15 min recovery period was measured using a breath-by-breath method. The accumulated O2 deficit was calculated by an extrapolation procedure. Total running time was the same for eight male sprint runners (49.5 +/- 6.0s) and for six male endurance athletes (49.4 +/- 5.3 s). The sprint group had significantly higher O2 deficit (p < 0.01) during the run as well as higher peak BLa (p < 0.05) and EPOC (p < 0.01) after the run than the endurance group. The relative contribution of anaerobic energy yield decreased from 80% to 60% during the first 15 s of the exhaustive run in both groups. The VO2 peaked and was almost unchanged from 25th to 40th s of the run in both groups, although only 79% of their VO2max was attained. The relative contribution of aerobic energy yield was significantly higher (p < 0.05) in the endurance (54-63%) than in the sprint group (43-47%) during the second half of the run. No correlation was found between the O2 deficit and EPOC but peak BLa correlated significantly (p < 0.05) with the O2 deficit (r = 0.53) and EPOC (r = 0.53). In conclusion, the energy release of the sprint and endurance athletes was different only during the second half of the exhaustive supramaximal run, when the sprinters used more the anaerobic and endurance athletes aerobic pathways for energy production.

Crocetin administration increases exercise endurance in trained rats

The carotenoid crocetin has been shown to relieve the hypoxic condition caused by many diseases. Since hypoxia is also a limiting factor in endurance performance, this study evaluated the effect of crocetin administration on exercise endurance. Eleven treadmill trained rats were randomly divided into an experimental or control group. Sixty minutes prior to exhaustive exercise, the exercise group received a 0.3 mL intraperitoneal injection of 0.2 mg crocetin/kg body weight, and the control group received a placebo injection. The experimental group improved running time by 18± 3 minutes (t test, p ≤ 0.01) and showed a reduction in postexercise blood lactate concentration by 1.84 ± 0.52 mM (t test, p ≤0.01). The results demonstrate that crocetin increased exercise endurance and decreased blood lactate concentration in trained rats. The mechanism of action may be that, by increasing oxygen diffusion, crocetin enhanced aerobic production of adenosine triphosphate while reducing anaerobic adenosine triphosphate...

The physiology of bottlenose dolphins (Tursiops truncatus): heart rate, metabolic rate and plasma lactate concentration during exercise.

Despite speculation about the swimming efficiency of cetaceans, few studies have investigated the exercise physiology of these mammals. In view of this, we examined the physiological responses and locomotor energetics of two exercising adult Tursiops truncatus. Oxygen consumption, heart rate, respiratory rate and post-exercise blood lactate concentration were determined for animals either pushing against a load cell or swimming next to a boat. Many of the energetic and cardiorespiratory responses of exercising dolphins were similar to those of terrestrial mammals. Average heart rate, respiratory rate and oxygen consumption for dolphins pushing against a load cell increased linearly with exercise levels up to 58 kg for a female dolphin and 85 kg for a male. Oxygen consumption did not increase with higher loads. Maximum rate of oxygen consumption (VO2max) ranged from 19.8 to 29.4 ml O2 kg-1 min-1, which was 7-11 times the calculated standard metabolic rate (VO2std) of the dolphins. Blood lactate concentration increased with exercise loads that exceeded VO2max. The maximum lactate concentration was 101.4 mg dl-1 (11.3 mmol l-1) for the male, and 120.6 mg dl-1 (13.6 mmol l-1) for the female. When swimming at 2.1 m s-1, heart rate, respiratory rate and post-exercise blood lactate concentration of the dolphins were not significantly different from values at rest. The cost of transport at this speed was 1.29 +/- 0.05 J kg-1 min-1. The energetic profile of the exercising bottlenose dolphin resembles that of a relatively sedentary mammal if the exercise variables defined for terrestrial mammals are used. However, the energetic cost of swimming for this cetacean is low in comparison to that of other aquatic and semi-aquatic mammals.

Maximal-intensity intermittent exercise: effect of recovery duration.

Seven male subjects performed 15 x 40m sprints, on three occasions, with rest periods of either 120 s (R120), 60 s (R60) or 30 s (R30) between each sprint. Sprint times were recorded with four photo cells placed at 0, 15, 30 and 40 m. The performance data indicated that whereas running speed over the last 10 m of each sprint decreased in all three protocols (after 11 sprints in R120, 7 sprints in R60 and 3 sprints in R30), performance during the initial acceleration period from 0-15 m was only affected with the shortest rest periods increasing from (mean +/- SEM) 2.58 +/- .03 (sprint 1) to 2.78 +/- .04 s (spring 15) (p < .05). Post-exercise blood lactate concentration was not significantly different in R120 (12.1 +/- 1.3 mmol.l-1) and R60 (13.9 +/- 1.2 mmol.l-1), but a higher concentration was found in R30 (17.2 +/- .7 mmol.l-1) (p < .05). After 6 sprints there was no significant difference in blood lactate concentration with the different recovery durations, however, there were significant differences in sprint times at this point, suggesting that blood lactate is a poor predictor of performance during this type of exercise. Although the work bouts could be classified primarily as anaerobic exercise, oxygen uptake measured during rest periods increased to 52, 57 and 66% of maximum oxygen uptake in R120, R60 and R30, respectively. Evidence of adenine nucleotide degradation was provided by plasma hypoxanthine and uric acid concentrations elevated post-exercise in all three protocols. Post-exercise uric acid concentration was not significantly affected by recovery duration.(ABSTRACT TRUNCATED AT 250 WORDS)