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At least 217 records · Page 12Linked to original sources

PubMed1995

Effect of prolonged exercise at 65 and 80% of VO2max on running economy.

The purpose of this study was to investigate the effect of prolonged exercise at 65 and 80% of VO2max on running economy. Fourteen male long distance runners performed two 90-min runs on an outdoor 400 m track at velocities of 65 and 80% of VO2max. Prior to and following each 90-min run, running economy was measured as the steady-state VO2 during treadmill runs at speeds of 188 and 228 m/min. During the 90-min run at 65% of VO2max, the mean weight loss was 1.3 kg. HR increased from 143 bpm between minutes 5-10 to 150 bpm between minutes 85-90. During the 90-min run at 80% of VO2max, the mean weight loss was 1.4 kg. The HR was 161 bpm between minutes 5-10 and increased to 165 bpm between minutes 85-90. When the post running economy test was conducted following each 90-min run, there was a significant increase in VO2 expressed in both l/min and ml/kg min. The increase in VO2 following the 90-min run at 80% of VO2max. These results suggest that 90-min runs at 65 and 80% of VO2max alter running economy with a significant increase in oxygen cost.

Adult↗

PubMed2006

Effect of different types of cricket batting pads on the running and turning speed in cricket batting.

The aim of this study was to compare a batsman's running and turning speed during three runs while wearing either traditional batting pads or one of two models of newly designed cricket batting pads. Fifteen cricketers participated. The running and turning speeds were measured on three different days with players using the three pairs of batting pads for each trial in random order. The weights of the pads were 1.85 kg, 1.70 kg and 1.30 kg for P1, P2 and P3 respectively. Each player had to run three runs (3 x 17.68m), with the times recorded at the completion of each run, as well as the time to cover the distance from 5 m before and after the turn at the end of the first run. The fastest time from two trials for each pair of pads was retained for analysis. An analysis of variance (ANOVA) with repeated measures was used to determine the differences between the mean times of the three trials. The results showed no significant differences between the types of batting pads and the time to complete the run-three-runs test (P1 = 10.67 +/- 0.48 s; P2 = 10.67 +/- 0.43; P3 = 10.69 +/- 0.44 s), the turning time (P1 = 2.34 +/- 0.18 s; P2 = 2.32 +/- 0.18 s; P3 = 2.35 +/- 0.19 s) and to complete the third run (P1 = 3.49 +/- 0.44 s; P2 = 3.53 +/- 0.34 s; P3 = 3.51 +/- 0.36 s). Of the 45 trials of three runs used for analysis, P1 recorded the fastest time on 16 trials (36%), P2 on 19 trials (42%) and P3 on 10 trials (22%). The results showed no significant differences in the running or turning speeds, although there may be some practical relevance to using the newly designed cricket batting pads.

Biomechanical Phenomena↗

PubMed2001

Biomechanical factors affecting running economy.

PURPOSE: The present study was designed to investigate kinematics, kinetics, and muscle activity for explaining running economy at different running speeds. METHODS: A total of 17 young endurance runners ran at 12-13 different running speeds. Respiratory gases were collected. Kinematic records were obtained by a high-speed video camera, and 3-D ground reaction forces (GRF) were measured simultaneously with telemetric EMG recordings of the selected leg muscles. In the analysis, joint moments and power were calculated by inverse dynamic methods. RESULTS: The oxygen consumption and energy expenditure increased quite linearly with increasing running speed. However, already at the slowest speed, interindividual differences in running economy were noticed, and they increased with increasing running speed. Simultaneously, the instantaneous joint moment-angular velocity curves of the ankle and knee joints shifted to the right and upward, thus increasing joint power in the push-off phase of contact. Most definitive was the increase in EMG-activity of the BF muscle and its correlation with energy expenditure (r = 0.48, P < 0.05). This two-joint muscle seems to be very active during the maximal running: its amplitude increased (P < 0.05) both in the swinging and contact phases with increasing running speed. CONCLUSIONS: The increased EMG of working muscles and the associated increase in power output may partly explain the increased energy expenditure with increasing running speed. Lower performances in running economy by some of the athletes may also be explained by poor running technique, such as unusually high braking and mediolateral forces, which may be caused by limited action of the hamstring muscles. However, no exclusive biomechanical parameters could be identified to explain the running economy.

Adolescent↗

PubMed2004

Relationship between skeletal muscle MCT1 and accumulated exercise during voluntary wheel running.

We examined whether the quantity of exercise performed influences the expression of monocarboxylate transporter (MCT) 1 and MCT4 in mouse skeletal muscles (plantaris, tibialis anterior, soleus) and heart. Wheel running exercise (1, 3, and 6 wk) was used, which results in marked variations in self-selected running activity. Differences in muscle MCT1 and MCT4 among animals, before the initiation of running, were not related to the quantity of exercise performed on the first day of wheel running. No changes in MCT4 were observed over the course of the study (P > 0.05). After 6 wk of running, were there significant increases in heart (50%; P < 0.05) and muscle MCT1 (31-60%; P < 0.05) but not after 1 and 3 wk (P > 0.05). Because skeletal muscle MCT1 and running distances varied considerably, we examined the relationship between these two parameters. Within the first week of training, MCT1 was negatively correlated with the accumulated running distance (r = -0.70, P < 0.05). On further analysis, it appears that, in the first week, excessive running (>20 km/wk) represses MCT1 (-16.1%; P < 0.05), whereas more modest amounts of running (<20 km/wk) increase MCT1 (+37%; P < 0.05). After 3 wk of running, a positive relationship was observed between MCT1 and running distance (r = +0.76), although there is a threshold that must be exceeded before an increase over the control animals occurs. Finally, in week 6, when MCT1 was increased in the tibialis anterior and plantaris muscles, there were no correlations with the accumulated running distances. These studies have shown that mild exercise training fails to increase MCT4 and that changes in MCT1 are complex, depending not only the accumulated exercise but also on the stage of training.

Adaptation, Physiological↗

PubMed1985

The role of compliance in mammalian running gaits.

The running gaits used by both bipedal and quadrupedal animals are reviewed and contrasted. At high speeds, bipeds use both ordinary running, in which the legs move opposite one another, and hopping. Quadrupeds generally use the trot or its variations at moderate speeds, and first the canter and then the gallop as speed increases. Running in both bipeds and quadrupeds generally involves at least one aerial phase per stride cycle, but certain perturbations to running including running in circles, running under enhanced gravity, running on compliant surfaces and running with increased knee flexion (Groucho running) can reduce the aerial phase, even to zero. A conceptual model of running based on the idea that an animal rebounds from the ground like a resonant mass-spring system may be used to compare the various gaits. The model makes specific predictions which show that galloping is generally faster than cantering, pronking or trotting, and requires lower peak vertical forces on the legs while also giving a smoother ride. Even so, trotting might be preferred to galloping at low and moderate speeds for the same reason that normal running is preferred to Groucho running-the more compliant gait offers a smoother ride and lower vertical ground-reaction forces on the feet, but this can only be obtained at a high cost of increased metabolic power.

Animals↗

PubMed2005

Running 8000 m fast or slow: Are there differences in energy cost and fat metabolism?

PURPOSE: To compare energy requirements and substrate use for running a given distance fast versus slow under field conditions. METHODS: Ten males and four females who were moderately endurance trained (32 +/- 6 yr; 71 +/- 11 kg; body mass index: 22.7 +/- 2.3 kg x m(-2); VO2max: 62.0 +/- 6.0 mL x min(-1) x kg(-1); individual anaerobic threshold [IAT]: 13.7 +/- 1.4 km x h(-1)) performed an incremental running protocol to determine IAT. Subsequently, two 8000-m runs at 70 and 95% IAT were performed on separate days in randomized order on an indoor track. Energy expenditure (EE) was measured by means of a portable metabolic device (indirect calorimetry). A meaningful difference in EE was defined as >10%. RESULTS: EE was significantly greater during the 95% IAT run than during the 70% IAT run (2650 +/- 276 and 2554 +/- 348 kJ, respectively). However, this difference was only 3.8 +/- 4.8%. Including measurements up to 10 min postexercise, the difference rose to 5.1 +/- 4.7% (95% IAT: 2830 +/- 301 kJ; 70% IAT: 2692 +/- 368 kJ). There was no significant difference between the absolute amounts of fat oxidized during the runs (70% IAT: 26 +/- 5 g; 95% IAT: 20 +/- 5 g). During the 95% IAT run, significantly more carbohydrates were metabolized than during the 70% IAT run (108 +/- 14 and 90 +/- 5 g, respectively). The difference in EE between the two runs increased from the first to the third part of the running distance (first: no significance; second: P < 0.01; third: P < 0.001). CONCLUSION: Energy requirements for a commonly run distance in recreational endurance training differ significantly but not relevantly between slow and fast speeds. However, increasing total running distance might lead to larger differences.

Adipose Tissue↗

PubMed1996

Biomechanics and running economy.

Running economy, which has traditionally been measured as the oxygen cost of running at a given velocity, has been accepted as the physiological criterion for 'efficient' performance and has been identified as a critical element of overall distance running performance. There is an intuitive link between running mechanics and energy cost of running, but research to date has not established a clear mechanical profile of an economic runner. It appears that through training, individuals are able to integrate and accommodate their own unique combination of dimensions and mechanical characteristics so that they arrive at a running motion which is most economical for them. Information in the literature suggests that biomechanical factors are likely to contribute to better economy in any runner. A variety of anthropometric dimensions could influence biomechanical effectiveness. These include: average or slightly smaller than average height for men and slightly greater than average height for women; high ponderal index and ectomorphic or ectomesomorphic physique; low percentage body fat; leg morphology which distributes mass closer to the hip joint; narrow pelvis and smaller than average feet. Gait patterns, kinematics and the kinetics of running may also be related to running economy. These factors include: stride length which is freely chosen over considerable running time; low vertical oscillation of body centre of mass; more acute knee angle during swing; less range of motion but greater angular velocity of plantar flexion during toe-off; arm motion of smaller amplitude; low peak ground reaction forces; faster rotation of shoulders in the transverse plane; greater angular excursion of the hips and shoulders about the polar axis in the transverse plane; and effective exploitation of stored elastic energy. Other factors which may improve running economy are: lightweight but well-cushioned shoes; more comprehensive training history; and the running surface of intermediate compliance. At the developmental level, this information might be useful in identifying athletes with favourable characteristics for economical distance running. At higher levels of competition, it is likely that 'natural selection' tends to eliminate athletes who failed to either inherit or develop characteristics which favour economy.

Age Factors↗

PubMed2001

Running economy and delayed onset muscle soreness.

BACKGROUND: The main purpose of this study was to test the effects of a duathlon competition on running economy. METHODS. EXPERIMENTAL DESIGN: A prospective study. SETTING: University. PARTICIPANTS: nine male and six female physical education students, which mean (SEM) age was 24.0 (1.3) years. MEASURES: Subjects participated in two competitive duathlons: D1 and D2 (5 km running + 16 km cycling + 2 km running). Before D1, an incremental exercise test on the treadmill was performed to determine the V O2max, the running speed at exhaustion (vmax), and the V O2, as well as the running speed (u) attained at the first and second ventilatory threshold (V O2V T1, uV T1, V O2V T2, uV T2). Two days later running economy (RE1) was assessed at four different speeds corresponding to 58, 63, 67 and 71% of the umax. During the following six weeks the subjects trained 4 days a week, running all them 210 km in total. At the end of the training program the incremental exercise test and the duathlon competition were repeated (D2). Two and seven days after the second duathlon running economy was measured again (RE2 and RE3, respectively). RESULTS: Small, but significant improvements were observed in duathlon performance, V O2max, umax, uV T1, V O2V T2 and uV T2, after training. Two days after D2 the oxygen cost of running was approximately 5% higher than seven days after D2 (p < 0.001). The respiratory exchange ratio increased by approximately 0.04 units between RE2 and RE3 (p < 0.001). However, the increase in fat oxidation in RE2 only accounted for approximately 20% of the extra oxygen cost of running (RE2 vs RE3). No significant differences across tests were observed for ventilation (V E), heart rate, V CO2 and V E/V CO2. CONCLUSIONS: This study shows that two days after a duathlon competition running economy is impaired, however, seven days after the competition the oxygen cost of running is restored.

Adult↗

PubMed1996

Human blood lactate and ammonia levels after supramaximal uphill and downhill running.

The purposes of this study were 1) to confirm whether there is a difference in the levels of blood lactate and ammonia after supramaximal uphill and downhill running for the same short duration and 2) to examine the relationship between peak blood lactate levels and work/lean body mass (LBM), as well as the relationship between peak blood ammonia levels and work/LBM following supramaximal uphill and downhill running. Eight healthy, untrained male subjects performed supramaximal uphill and downhill running on a motor-driven treadmill for about 70 sec. Though there was a significant difference (p < 0.05) in running speed and work/LBM between supramaximal uphill and downhill running, no significant difference was found in exhaustion time or heart rate. Both the peak blood lactate and ammonia concentrations were significantly lower after downhill running than after uphill running (p < 0.05). Although there was no significant relationship between peak blood ammonia levels and work/LBM following either uphill or downhill running, significant linear relationships between the peak blood lactate levels and work/LBM were observed following uphill running (r = 0.74, p < 0.05) and downhill running (r = 0.72, p < 0.05). These results suggest that the differences in the blood lactate and ammonia concentration between supramaximal downhill and uphill running of the same duration may be due to the total recruitable muscle mass during exercise, and that peak blood lactate can be used as an index of anaerobic work capacity for untrained subjects under these running conditions.

Adult↗

PubMed2003

Differential sensitivity to acute administration of Ritalin, apomorphine, SCH 23390, but not raclopride in mice selectively bred for hyperactive wheel-running behavior.

RATIONALE: Previous studies of mice ( Mus domesticus) selectively bred for high voluntary wheel running have suggested that the hyperactivity is associated with dysfunction in the dopaminergic neuromodulatory system and that high-running mice may represent a useful genetic model for attention deficit hyperactivity disorder (ADHD). OBJECTIVES: We tested the hypothesis that mice from the four replicate hyperactive lines would respond differently to methylphenidate (Ritalin), apomorphine (non-selective dopamine agonist), SCH 23390 (selective D1-like dopamine antagonist), and raclopride (selective D2-like dopamine antagonist) than individuals from the four replicate, randomly bred, control lines. METHODS: After animals were habituated (3 weeks) to their cages with attached wheels, drugs were administered via intraperitoneal injections, at night, during peak wheel-running activity. Revolutions on wheels 10-70 min post-injection were used to quantify drug responses. RESULTS: Ritalin (15 mg/kg and 30 mg/kg) increased wheel running in control lines but decreased running in selected lines. A low-dose (0.125 mg/kg) of apomorphine reduced wheel running by a similar amount in control and selected lines; however, higher doses of apomorphine (0.25 mg/kg and 0.5 mg/kg) produced greater reductions in wheel running in the control lines. SCH 23390 (0.025, 0.05, and 0.1 mg/kg) caused greater reductions in wheel running in control than in selected lines. Raclopride (0.5, 1, and 2 mg/kg) reduced wheel running by a similar amount in control and selected lines. CONCLUSIONS: These results support the interpretation that genetically determined hyperactive wheel-running behavior is associated with altered dopaminergic function in this mouse model. More specifically, results suggest that D1-like (D1 or D5), but not D2-like (D2, D3, or D4), dopamine receptors have reduced function in the high-running mice. The fact that Ritalin decreased wheel running in selected lines further supports their use as an animal model of ADHD.

Animals↗

PubMed2003

Relationship between wheel running, feeding, drinking, and body weight in male rats.

The amount of wheel running varies widely between rats. Wheel introduction and running also have profound effects on the animal's energy balance. We explored the effects of ad lib wheel access and running levels on feeding, drinking, and body weight in 30 young adult male rats with wheel access and in 30 rats without wheel access. The initial running period (Days 1-8) and a time of stable running [Days 29-32 (DEnd)] were analyzed using both between- and within-group approaches. Initially, wheel access suppressed feeding (by about 25% over the 8 days) but not drinking. There were no significant correlations between the amount of wheel running and the other behaviors. The degree of feeding suppression was also not correlated to the amount of running. When running had stabilized (animal ran from 841 to 13,124 wheel turns per day), food intake was increased by about 0.75 g per 1000 wheel turns. Running at this time correlated positively with feeding and drinking and negatively with body weight and weight gain. In animals without wheel access, feeding and drinking were positively correlated with weight and weight gain, but in animals with wheel access, these correlations were close to zero. Only early running predicted later levels of running but accounted for only 23% of the variance in running. Wheel access has profound but very different immediate and long-term effects on the rats' energy balance.

Animals↗

PubMed2006

Differences in oxygen uptake but equivalent energy expenditure between a brief bout of cycling and running.

BACKGROUND: We examined aerobic and anaerobic exercise energy expenditure and excess post-exercise oxygen consumption (EPOC) between a 250 Watt, 1-minute bout of cycling and uphill treadmill running. METHODS: Fourteen active to well-trained subjects volunteered for the investigation (VO2 max: 57.0 +/- 12.9 ml x kg x min(-1) cycle; 59.3 +/- 13.7 ml x kg x min(-1) run; p = 0.44). Anaerobic energy expenditure was estimated from Deltablood lactate. Statistical analysis was completed using a paired t-test (mean +/- SD). RESULTS: Perceived exertion did not differ between exercise bouts (14.0 +/- 2.3 cycle; 13.2 +/- 2.1 run; p = 0.29). Exercise oxygen uptake was significantly greater for running (41.4 +/- 6.9 kJ) compared to cycling (31.7 +/- 7.7 kJ) (p = 0.0001). EPOC was not different between cycling and running (p = 0.21) so that exercise oxygen uptake + EPOC was greater for running (103.0 +/- 13.5 kJ) as compared to cycling (85.4 +/- 20.2 kJ; p = 0.008). Anaerobic energy expenditure was significantly greater for cycling (32.7 +/- 8.9 kJ) versus running (22.5 +/- 11.1 kJ) (p = 0.009). Aerobic + anaerobic exercise energy expenditure (cycle 64.3 +/- 12.2 kJ; run 63.9 +/- 10.1 kJ) (p = 0.90) and total energy expenditure (including EPOC; cycle 118.0 +/- 21.8 kJ; run 125.4 +/- 19.1 kJ; p = 0.36) were similar for cycling and running. CONCLUSION: Oxygen-only measures reveal discrepancy in energy expenditure between cycling and uphill running. Measurements of exercise oxygen uptake, Deltablood lactate and a modified EPOC promote the hypothesis of a similarity in exercise and total energy expenditure between 1-minute work-equivalent bouts of cycling and uphill running.

Journal Article↗

PubMed1996

Critical velocity of continuous and intermittent running exercise. An example of the limits of the critical power concept.

The relationship between exhaustion time (tlim) and distance Dlim for running exercises at constant velocity until exhaustion can be described by a linear relationship (Dlim = a + b tlim) whose slope corresponds to a critical velocity. Seven runners participated to the study which compared the critical velocity of continuous versus intermittent running exercises. The critical velocity for continuous running (Vcritc) was calculated from the results (tlimc and Dlimc) of running exercises performed at 95 and 105% of the final velocity of the Montreal Track Test (vMTT). The intermittent running consisted of repetitions of running exercises performed at 95 and 105% vMTT during a time equal to half the value of the corresponding tlimc. The subjects recovered during a time equal to running time while jogging at a slow pace. The critical velocity for intermittent running (Vcriti) was calculated from the cumulated running distance (Dlimi) and cumulated running time (tlimi) corresponding to 95 and 105% vMTT. Vcriti was equal to Vcritc (4.56 +/- 0.444 m.s-1 vs 4.60 +/- 0.416 m.s-1). Nevertheless, in some subjects, the repetition numbers were very different for the intermittent running exercises at 95 and 105% vMTT. This paradoxical result could be explained by the fact that the value of Vcrit should be theoretically little sensitive to a large error in the value of tlim corresponding to a velocity slightly higher than critical velocity, for intermittent exercises as well as continuous exercises.

Adult↗

PubMed1986

Validation of two running tests as estimates of maximal aerobic power in children.

In order to validate the "Maximal Multistage 20 Meter Shuttle Run Test" by Leger and Lambert (1982) (20-MST) as an estimate of maximal aerobic power (VO2max) and to compare the results of this test with the results of a 6 min endurance run, 82 subjects (41 boys and 41 girls) aged 12-14 performed the 20-MST and the 6 min endurance run, and had their VO2max directly measured during maximal treadmill running. The 20-MST is a maximal running test starting at a running speed of 8.0 km X h-1, which is increased every minute and in which the pace is set by an audio signal. Performing the test, one runs a 20-meter course back and forth. The test result is expressed as "palier" (one palier is approximately one minute). The mean results of the 20-MST were, for boys, 8.0 palier (+/- 1.7) and for girls, 6.4 palier (+/- 1.5). The mean results of the 6 min endurance run were for boys, 1264.4 meters (+/- 160.8), and for girls, 1103.9 meters (+/- 144.7). The mean VO2max for boys was 53.2 ml X kg-1 X min-1 (+/- 5.4) and for girls, 44.1 (+/- 4.8) ml X kg-1 X min-1. The correlation coefficient between VO2max and the 20-MST was found to be 0.68 (+/- 3.9) for boys, 0.69 (+/- 3.4) for girls and 0.76 (+/- 4.4) for both sexes, and that of VO2max with the 6 min endurance run was 0.51 (+/- 4.6) for boys, 0.45 (+/- 4.3) for girls and 0.63 (+/- 5.3) for both sexes. The conclusion is that the 20-MST is a suitable tool for the evaluation of maximal aerobic power. Although the differences in validity between the 20-MST and the 6 minutes endurance run were statistically not significant (p greater than 0.05), for reasons of practicability the 20-MST should be preferred to the 6 minutes endurance run when used in physical education classes.

Adolescent↗

PubMed1992

[Effect of carbohydrate intake during a long distance run on work capacity and metabolism].

The present study addressed the effects of carbohydrate consumption during endurance exercise on performance, energy turnover, and metabolism. Well-trained endurance runners consumed a beverage with (cho[+]) or without (cho[-]) carbohydrates during a long-distance run (46.6 km). The respiratory quotient (RQ), plasma levels of carbohydrate and fat metabolites, and of hormones (insulin, glucagon) were measured before, several times during, and after the run. The mean running speed for the entire distance was 13.6 and 13.4 km/h with the cho[+] and cho[-] beverage, respectively. The decrease in speed that was observed towards the end of the run was somewhat more pronounced with consumption of the cho[-] beverage. The RQ decreased during the run almost linearly. This decrease was independent of the consumed beverage. The changes in plasma levels of lactate, free fatty acids (FFA), glycerol, D-3-hydroxybutyrate (DHB), glucagon and insulin that occurred during the run were not affected by intake of the cho[+] beverage. However, intake of the cho[+] beverage prevented the decrease in plasma glucose observed towards the end of the run under control conditions, and eliminated the steep postexercise increase in plasma DHB. The intake of the cho[+] beverage also caused a rapid decrease in plasma levels of FFA and glucagon after the run, and slightly increased plasma insulin. The results demonstrate that ingestion of a carbohydrate-containing beverage during a long-distance run affects metabolism only during the final phase of the run and during the subsequent recovery period. Moreover, carbohydrate consumption improves performance only during the final phase of a long-distance run.

3-Hydroxybutyric Acid↗

PubMed2002

Effect of fatigue on spontaneous velocity variations in human middle-distance running: use of short-term Fourier transformation.

Best performances in middle-distance running are characterized by coefficients of variation of the velocity ranging from 1% to 5%. This seems to suggest that running at constant velocity is a strain inducing an increase in physiological variables such as oxygen uptake. This study tested three questions. (l) Does velocity variability during a middle-distance all-out run increase with fatigue? (2) Does velocity variability alter the slow phase of the oxygen kinetic because of small spontaneous recoveries, compared with the same distance run at constant velocity? (3) Is a maintained average velocity over a given distance enhanced by a variable-pace rather than by a constant-pace? Ten long-distance runners performed two series of all-out runs over the distance (previously determined) which they could cover maintaining a velocity equal to 90% of that eliciting maximal oxygen consumption. In the first series ( free-pace) the subjects were asked to run as fast as possible, without any predetermined velocity profile. In the second series, the same distance was covered at a constant velocity (equal to the average in the previous free-pace run), set by a cyclist preceding the runner. Short-term Fourier transform was used to analyse velocity oscillations. Our results show that: (1) for all subjects, the mean energy spectrum did not change throughout the free-pace runs, suggesting that velocity variability did not increase with fatigue (2-way ANOVA, P=0.557); (2) the kinetic of oxygen uptake and its asymptote were not changed during the free-pace runs compared to the constant-velocity run; (3) performance was not significantly improved by free-pace average velocity [mean (SD) 4.22 (0.47) compared to 4.25 (0.52) m x s(-1) for constant and free-pace respectively, t=-0.58, P=0.57]. These results indicate that during middle-distance running, fatigue does not increase variations in velocity, and free-pace changes neither performance nor the oxygen kinetic.

Adult↗

PubMed2000

Time to exhaustion during severe intensity running: response following a single bout of interval training.

The primary aim of this study was to examine any change in performance caused by a fatiguing interval training session (TS). A secondary aim of this study was to examine the change in oxygen uptake (VO(2)) during moderate and severe intensity running, and the relationship with the change in performance. Seven male runners [mean age 24 (SD 6) years, height 1.79 (SD 0.06) m, body mass 67.9 (SD 7.6) kg, maximal oxygen uptake (VO(2max)) 4.14 (SD 0.49) l. min(-1)] were studied. The VO(2) during moderate and severe intensity running and running performance were studied immediately prior to, 1 h following, and 72 h following TS. The TS was performed on a treadmill, and consisted of six bouts of 800 m at 1 km. h(-1) below the velocity at VO(2max) (v(V)O(2max)), with 3-min rest intervals. Performance was also assessed at 1 km. h(-1) below v(V)O(2max), in the form of time to exhaustion (t(lim)). The VO(2) and heart rate (f(c)) were assessed both during the severe intensity performance trial, and the moderate intensity run at 50% v(V)O(2max). Whilst a significant change was observed in running performance and the VO(2) during both moderate and severe intensity running prior to and following TS, no relationship was observed between the magnitude of change in these variables. At 1 h following TS, t(lim) had decreased by 24%, VO(2) during moderate intensity running had increased by 2%, and the difference in VO(2) between 2 min 45 s and the end of severe intensity running had increased by 91% compared with values recorded prior to TS. At 1 h following TS, f(c) had also increased significantly during moderate intensity running by 5% compared to the value recorded prior to TS. These findings demonstrated that TS resulted in a reduction in performance, and that the relationship between running performance and VO(2) during running may be altered under conditions of prolonged fatigue.

Adult↗

PubMed2000

Advantages of smaller body mass during distance running in warm, humid environments.

The purpose of this study was to examine the extent to which lighter runners might be more advantaged than larger, heavier runners during prolonged running in warm humid conditions. Sixteen highly trained runners with a range of body masses (55-90 kg) ran on a motorised treadmill on three separate occasions at 15, 25 or 35 degrees C, 60% relative humidity and 15 km x h(-1) wind speed. The protocol consisted of a 30-min run at 70% peak treadmill running speed (sub-max) followed by a self-paced 8-km performance run. At the end of the submax and 8-km run, rectal temperature was higher at 35 degrees C (39.5+/-0.4 degrees C, P<0.05) compared with 15 degrees C (38.6+/-0.4 degrees C) and 25 degrees C (39.1+/-0.4 degrees C) conditions. Time to complete the 8-km run at 35 degrees C was 30.4+/-2.9 min (P<0.05) compared with 27.0+/-1.5 min at 15 degrees C and 27.4+/-1.5 min at 25 degrees C. Heat storage determined from rectal and mean skin temperatures was positively correlated with body mass (r=0.74, P<0.0008) at 35 degrees C but only moderately correlated at 25 degrees C (r=0.50, P<0.04), whereas no correlation was evident at 15 degrees C. Potential evaporation estimated from sweat rates was positively associated with body mass (r=0.71, P<0.002) at 35 degrees C. In addition, the decreased rate of heat production and mean running speed during the 8-km performance run were significantly correlated with body mass (r=-0.61, P<0.02 and r=-0.77, P<0.0004, respectively). It is concluded that, compared to heavier runners, those with a lower body mass have a distinct thermal advantage when running in conditions in which heat-dissipation mechanisms are at their limit. Lighter runners produce and store less heat at the same running speed; hence they can run faster or further before reaching a limiting rectal temperature.

Blood Volume↗