A laboratory running test: metabolic responses of sprint and endurance trained athletes.

A laboratory-based sprint running test has been devised to examine the performance characteristics and metabolic responses of an individual to 30 seconds of maximal exercise. A non-motorised treadmill was used so that the individual was able to sprint at his own chosen speed and also to vary his speed as fatigue occurred. The treadmill was instrumented so that the chosen speeds as well as the equivalent distance travelled could be monitored by micro-computer throughout the test. The test-retest reliability of the procedure was investigated with 14 recreational runners who performed the test on different days. A good correlation (r = 0.93) was found between the values obtained for peak running speeds on the two occasions. In an attempt to establish whether or not this test could be used to identify the differences in the performance characteristics of highly trained individuals, the responses to the test of eleven sprint trained and eleven endurance trained athletes were examined. The sprint trained athletes covered a greater distance (162.2 +/- 5.95 m vis 153.51 +/- 12.32 m; p less than 0.01) and had higher blood lactate concentrations (16.52 +/- 1.23 mM vis 12.98 +/- 1.77 mM; p less than 0.01) than the endurance trained athletes. Therefore this laboratory sprint running test offers an additional way of investigating human responses to brief periods of high intensity exercise.     

Neuromuscular characteristics and fatigue during 10 km running

This study investigated neuromuscular characteristics and fatigue during 10 km running (10 K) performance in well-trained endurance athletes with different distance running capability. Nine high (HC) and ten low (LC) caliber endurance athletes performed the 10 K on a 200 m indoor track, constant velocity lap (CVL, 4.5 m x s(-1)) 5 times during the course of the 10 K and maximal 20 m speed test before (20 m(b)) and after (20 m(a)) the 10 K. Running velocity (V), ground contact times (CT), ground reaction forces (F) and electromyographic activity (EMG) of the leg muscles (vastus lateralis; VL, biceps femoris; BF, gastrocnemius; GA) were measured during 20 m(b), 20 m(a), and CVLs. The 10 K times differed (p<0.001) between HC and LC (36.3+/-1.2 and 39.2+/-2.0 min, respectively) but no differences were observed in 20 m(b) velocity. The 10 K led to significant (p<0.05) decreases in V, F and integrated EMG (IEMG) and increases in CTs of 20 m(a) in both groups. No changes were observed in HC or LC in F and IEMG during the CVLs but HC showed shorter (p<0.05) mean CT of CVLs than LC. A significant correlation (r = -0.56, p<0.05) was observed between the mean CT of CVLs and velocity of 10 K (V10K). Pre-activity of GA in relation to the IEMG of the total contact phase during the CVLs was higher (p<0.05) in HC than LC. The relative IEMGs of VL and GA in the propulsion phase compared to the IEMG of the 20 m(b) were lower (p<0.05) in HC than LC. In conclusion, marked fatigue took place in both HC and LC during the 10 K but the fatigue-induced changes in maximal 20 m run did not differentiate endurance athletes with different V10K. However, a capability to produce force rapidly throughout the 10 K accompanied with optimal preactivation and contact phase activation seem to be important for 10 km running performance in well trained endurance athletes.     

Determinants of five kilometre running performance in active men and women.

Previous studies of elite endurance athletes have suggested that success in distance running is attributable to the possession of a high maximal oxygen uptake (VO2 max), the utilisation of a large fraction of the VO2 max and to running economy. The purpose of the present study was to examine the relationships between these physiological characteristics and running performance in active but not elite men and women. Maximal oxygen uptake values were 57.6 +/- 6.2 and 46.6 +/- 4.8 ml . kg.-1 min-1 for the men and women respectively (p less than 0.01). Running performance was assessed as a 5 km time trial and the men completed this distance in 19.77 +/- 2.27 min and the women in 24.44 +/- 3.19 min (p less than 0.01). Maximal oxygen uptake showed strong correlations (p less than 0.01) with running performance (men, r = -0.85; women, r = -0.80) but there was only a modest relationship between running economy and performance (men, r = 0.39; women, r = 0.34). The results of the present study suggest that the faster 5 km performance times recorded by the men were best explained by their higher VO2 max values.     

Lactate and glucose minimum speeds and running performance

This study aimed to analyse the validity of glucose minimum speed (GMS) for lactate minimum speed (LMS) assessment during running and their relationship to endurance performance. Eight male trained runners (28.7 +/- 9.0 years) volunteered to take part in this study and underwent an official 10-km road race and a track lactate minimum test (LMT) (0.5-km sprint plus 6 x 800 m from 87 to 98% of maximal 3-km speed). Lactate and glucose minimum speeds were considered those related to the minimum blood lactate and glucose concentrations respectively attained during the graded phase of LMT. Significant correlations (p < 0.05) were found between LMS and GMS (r = 0.72) and LMS and 10-km performance (r = 0.83), but not between GMS and 10-km performance (r = 0.49). No significant differences (p > 0.05) were found between LMS (4.75 +/- 0.08 m/s), GMS (4.73 +/- 0.07 m/s) and 10-km mean speed (4.79 +/- 0.17 m/s). In conclusion, we found GMS to be a good predictor of LMS during track LMT, LMS being well related to endurance running performance.     

Acute effects of muscle fatigue and recovery on force production and relaxation in endurance, power and strength athletes

Acute effects of fatigue produced by a maintained 60% isometric loading on force production and relaxation characteristics of the leg extensor muscles were studied in male endurance (n = 9), power (n = 6) and strength athletes (n = 9). The initial non-fatigued isometric force-time curves differed considerably (p less than 0.05-0.001) between the groups so that the times of force production were the shortest and correspondingly the maximal rate of force production the greatest in the power athletes but the longest and the smallest in the endurance athletes. The endurance time of 70.7 +/- 32.9 s at the 60% fatiguing loading was in the endurance athletes longer (p less than 0.01) than in the power (30.6 +/- 7.1 s) and strength groups (31.7 +/- 5.5 s). The present fatiguing loading resulted in all athlete groups in significant (p less than 0.05-0.001) worsening in maximal force, in the times of force production and in the maximal rates of force production and relaxation. However, this worsening in the endurance athletes in maximal force (to 92.9 +/- 7.1%) as well as in the maximal rates of force production (to 79.2 +/- 20.8%) and relaxation (to 73.1 +/- 29.2%) were significantly (p less than 0.05-0.01) smaller than the corresponding decreases in the power athletes (to 64.3 +/- 8.0%, 74.8 +/- 7.4% and to 40.9 +/- 12%, respectively) and in the strength athletes (to 65.7 +/- 7.0%, 56.7 +/- 16.0% and to 34.8 +/- 6.7%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Substantial influence of level of endurance capacity on the association of perceived exertion with blood lactate accumulation

Capillary blood lactate assessment is increasingly used by well-trained runners to monitor the intensity of endurance exercise. In order to examine the known association of exercise intensity with blood lactate accumulation also in less trained subjects, we analysed data from a standardized incremental maximal test on the treadmill of 319 men (age 22.9 +/- 5.5 years, [means +/- S.D.]) and 145 women (22.7 +/- 4.5 years) characterized by a wide variation in endurance capacity. Results showed that the running velocity eliciting a blood lactate concentration of 4 mmol/l did not correspond to the same exercise intensity in well endurance-trained vs poorly endurance-trained subjects. At 4 mmol/l blood lactate, the slowest decile of men (i.e. 32 out of 319) ran at 71 +/- 4.7% (corresponding to 2.9 +/- 0.3 m/s) of their maximal treadmill velocity attained during the test (4.1 +/- 0.4 m/s), indicating a rating of perceived exertion (RPE) of 12.3 +/- 1.8 points (Borg scale, range 6-20 points), while the fastest decile of men (n = 32) ran at 91 +/- 3.1% (corresponding to 5.4 +/- 0.2 m/s) of their maximal treadmill speed (5.9 +/- 0.2 m/s), indicating a RPE of 16.6 +/- 1.1 points. Very similar results were observed in women. There was a highly significant, positive correlation between running speed eliciting a blood lactate concentration of 4 mmol/l and RPE when running at this speed, with r = 0.64 in men and r = 0.55 in women. At the same proportional level of maximal running velocity, poorly endurance-trained athletes showed a 2-3 mmol/l higher capillary lactate concentration than well endurance-trained athletes, with both groups indicating the same RPE. These results suggest that fixed blood lactate concentrations not at all mean the same exercise intensity for well vs poorly endurance-trained subjects; this systemic trend should be considered when using blood lactate assessment for individual exercise counselling.     

Effect of the passive recovery period on the lactate minimum speed in sprinters and endurance runners

The objective of this study was to verify the effect of the passive recovery time following a supramaximal sprint exercise and the incremental exercise test on the lactate minimum speed (LMS). Thirteen sprinters and 12 endurance runners performed the following tests: (1) a maximal 500 m sprint followed by a passive recovery to determine the time to reach the peak blood lactate concentration; (2) after the maximal 500 m sprint, the athletes rested eight mins, and then performed 6 x 800 m incremental test, in order to determine the speed corresponding to the lower blood lactate concentration (LMS1) and; (3) identical procedures of the LMS1, differing only in the passive rest time, that was performed in accordance with the time to peak lactate (LMS2). The time (min) to reach the peak blood lactate concentration was significantly higher in the sprinters (12.76 +/- 2.83) than in the endurance runners (10.25 +/- 3.01). There was no significant difference between LMS 1 and LMS2, for both endurance (285.7 +/- 19.9; 283.9 +/- 17.8 m/min; r = 0.96) and sprint runners (238.0 +/- 14.1; 239.4 +/- 13.9 m/min; r = 0.93), respectively. We can conclude that the LMS is not influenced by a passive recovery period longer than eight mins (adjusted according with the time to peak blood lactate), although blood lactate concentration may differ at this speed. The predominant type of training (aerobic or anaerobic) of the athletes does not seem to influence the phenomenon previously described.     

Moment and power of lower limb joints in running

The aim of this study was to test the suitability of inverse dynamics method for instantaneous expression of joint kinetics and muscle function with various parts of the ground contact when running at different speeds. Nine male runners ran at speeds of 4.0 m x s(-1), 6.0 m x s(-1) and at their maximal speed. 2-D video analysis (200-frame x s(-1)) was synchronized with 3-D ground reaction force measurements (10 m-long force platform). Mechanical joint power was computed from 2-D segment dynamics associated with joint forces and net moments in multi-body movements. From these computations two successive functional phases during contact were found in the ankle and knee joints: 1) extensor negative and 2) extensor positive work. The hip joint showed three phases: 1) extensor positive, 2) flexor negative and 3) flexor positive work. Peak joint power increased in every investigated joint with increasing running speed. The highest changes were observed in the hip joint: from 327 +/- 203 W at a speed of 4.0 m x s(-1) to 1642 +/- 729 W (p < 0.01) at the maximal speed. The results may suggest that the role of the ankle and knee extensors is to create high joint stiffness before and during the contact phase, while the hip extensors are the prime forward movers of the body with increasing running speed. In conclusion, the inverse dynamics method may be of importance for use in specifying the joint kinetics and muscle function. However, the interpretation may become clearer when this method is used simultaneously with EMG measurements.     

The consequences of swim, cycle, and run performance on overall result in elite olympic distance triathlon

This study examined the consequences of performance in swim, cycle, and run phases on overall race finish in an elite "draft legal" Olympic distance (OD) triathlon. The subjects were 24 male athletes grouped by rank order into the top 50 % (n = 12) and bottom 50 % (n = 12) of the race population. Swimming velocity (m x s (-1)), cycling speed (km x h (-1)), and running velocity (m x s (-1)) were measured at regular intervals using a global positioning system, chip timing system, and video analysis. Actual rank after each stage and overall was obtained from the race results and video analysis. The top 50 % athletes overall swam faster over the first 400 m of the swim phase (p > 0.05). Their swim ranking was lower (p < 0.01) than the bottom 50 % athletes after this stage. There were no significant differences in actual race position between the groups after the cycle. However, the bottom 50 % athletes after the swim stage cycled faster (p < 0.01) at 13.4 km of the cycle. Speed at 13.4 km of the cycle stage was inversely correlated (r = 0.60, p < 0.01) to running performance. Performance (rank and velocity) in the running stage was highly correlated with overall race result (r = 0.86 and - 0.53, respectively, both p > 0.01). It appears that inferior swimming performance can result in a tactic that involves greater work in the initial stages of the cycle stage of elite OD racing, and may influence subsequent running performance.     

Concurrent endurance and explosive type strength training improves neuromuscular and anaerobic characteristics in young distance runners

To study effects of concurrent explosive strength and endurance training on aerobic and anaerobic performance and neuromuscular characteristics, 13 experimental (E) and 12 control (C) young (16 - 18 years) distance runners trained for eight weeks with the same total training volume but 19% of the endurance training in E was replaced by explosive training. Maximal speed of maximal anaerobic running test and 30-m speed improved in E by 3.0 +/- 2.0% (p < 0.01) and by 1.1 +/- 1.3% (p < 0.05), respectively. Maximal speed of aerobic running test, maximal oxygen uptake and running economy remained unchanged in both groups. Concentric and isometric leg extension forces increased in E but not in C. E also improved (p < 0.05) force-time characteristics accompanied by increased (p < 0.05) rapid neural activation of the muscles. The thickness of quadriceps femoris increased in E by 3.9 +/- 4.7% (p < 0.01) and in C by 1.9 +/- 2.0% (p < 0.05). The concurrent explosive strength and endurance training improved anaerobic and selective neuromuscular performance characteristics in young distance runners without decreases in aerobic capacity, although almost 20% of the total training volume was replaced by explosive strength training for eight weeks. The neuromuscular improvements could be explained primarily by neural adaptations.     

Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players

The aim of this study was to examine the construct validity of selected field tests as indicators of match-related physical performance. During the competitive season, eighteen professional soccer players (age 26.2 +/- 4.5 yrs, mass 80.8 +/- 7.8 kg, and height 181.9 +/- 3.7 cm) completed an incremental running field test to exhaustion, a vertical-jump and a repeated-sprint ability (RSA) test. Match physical performance was quantified during official matches using a video-computerized, semi-automatic, match analysis image recognition system, (ProZone, Leeds, UK). The selected measures of match physical performance were: total distance covered (TD), high intensity running (HIR: > 14.4 km . h (-1)), very high intensity running (VHIR:> 19.8 km . h (-1)), sprinting (> 25.2 km . h (-1)) and top running speed. Significant correlations were found between peak speed reached during the incremental field test and TD (r = 0.58, R (2) = 0.34; p < 0.05), HIR (r = 0.65, R (2) = 0.42; p < 0.01) and VHIR (r = 0.64, R (2) = 0.41; p < 0.01). Significant correlations were also found between RSA mean time and VHIR (r = - 0.60, R (2) = 0.36; p < 0.01) and sprinting distance (r = - 0.65, R (2) = 0.42; p < 0.01). Significant differences were found between the best and worst group as defined by the median split technique for peak speed (TD = 12 011 +/- 747 m vs. 10 712 +/- 669, HIR = 3192 +/- 482 m vs. 2314 +/- 347 m, and VHIR = 1014 +/- 120 vs. 779 +/- 122 m, respectively; p < 0.05) and RSA mean time (VHIR = 974 +/- 162 m vs. 819 +/- 144 m, and sprinting = 235 +/- 56 vs. 164 +/- 58 m, respectively; p < 0.05). In conclusion, this study gives empirical support to the construct validity of RSA and incremental running tests as measures of match-related physical performance in top-level professional soccer players.     

The Yo–Yo intermittent recovery test in basketball players

The purpose of this study was to examine the physiological correlates of the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) in basketball players. Twenty-two male basketball players (means+/-S.D., body mass 72.4+/-11.4kg, height 181.7+/-6.9cm, age 16.8+/-2.0 years) were tested for maximal oxygen uptake (VO(2max)), ventilatory threshold (VT) and running economy (RE) on a motorized treadmill. Lower limb explosive strength and anaerobic-capacity was assessed using vertical jumps (CMJ), 15m shuttle running sprint (15mSR) and line drill (LD), respectively. The same test battery was replicated after an experimental basketball game in order to assess selective effect of fatigue on physical performance. Pre to post-game CMJ (40.3+/-5.7 versus 39.9+/-5.9cm) and 15mSR (5.80+/-0.25 versus 5.77+/-0.22s) performances were not significantly different (p>0.05). LD performance decreased significantly post-game (from 26.7+/-1.3 to 27.7+/-2.7s, p<0.001). Yo-Yo IR1 performances (m) were significantly related to VO(2max) (r=0.77, p=0.0001), speed at VO(2max) (r=0.71, p=0.0001) and %VO(2max) at VT (r=-0.60, p=0.04). Yo-Yo IR1 performance was significantly correlated to post-game LD decrements (r=-0.52, p=0.02). These findings show that Yo-Yo IR1 may be considered as a valid basketball-specific test for the assessment of aerobic fitness and game-related endurance.     

Control of training in middle- and long-distance running by means of the individual anaerobic threshold.

It was examined in 24 highly trained endurance athletes (middle- and long-distance runners, triathletes) whether concrete training recommendations can be made for endurance training and a speed session program (5 x 1000 m with 4.5-min breaks) by means of incrementally graded treadmill exercise with determination of the individual anaerobic threshold (IAT). The intensities of the different training sessions were decided upon using percentages of speed at the IAT and controlled by lactate determinations. The endurance runs were differentiated by terrain gradation and the speed sessions by climatic conditions. There is a significant correlation between the behaviour of lactate during training sessions and the IAT or percentages of speed at the IAT determined on a treadmill (endurance run flat terrain: r = 0.79, n = 13, p less than 0.01; endurance run graded terrain: r = 0.72, n = 20, p less than 0.001; 5 x 1000 m under good conditions: r = 0.97, n = 9, p less than 0.001; 5 x 1000 m under poor conditions: r = 0.91, n = 7, p less than 0.001). Both terrain gradation (endurance runs) and poor climatic conditions (speed sessions) lead to a left shifting of the regression line with unchanged slope. Conclusively the IAT determined during a treadmill exercise allows a sufficiently precise control of training both for endurance runs performed with different intensities and for the 5 x 1000-m speed session program. However, the external conditions have to be considered in order to provide correct training recommendations.     

Maximal but not submaximal performance is reduced by constant-speed 10-km run

AIM: Effects of endurance exercise on running economy, mechanics, force generating capacity and their interactions were examined. During the exercise, metabolic, kinetic and kinematic variables were recorded to find out adaptive mechanisms in the course of the fatiguing run. In addition, before and after it maximal force and power production was tested. METHODS: Experimental design: comparative. Setting: University. Participants and intervention: 7 men unaccustomed to endurance training run 10 km at individually chosen constant speed (3.5+/-0.5 m x s(-1)) on an indoor track. Measures: 3-D ground reaction forces, electromyographic (EMG) activities from 7 leg muscles, pulmonary ventilation, gas exchange, heart rate and movement kinematics were measured during the run. Blood lactate and serum creatine kinase activity were determined. Maximal voluntary contraction (MVC) with superimposed double twitch (DT), and passive DT tests in plantarflexor muscles were performed before and after the 10 km run. Changes in 20 m sprint performance were evaluated in before-after comparison. RESULTS: The 10 km run caused significant reductions in maximal running speed (8.2 vs 7.6 m x s(-1), p<0.05), in MVC (1216 vs. 984 N, p<0.05), and in passive DT (271 vs 211 N, p<0.05). During the submaximal run, however, the subjects were able to maintain relatively constant oxygen consumption and running kinematics. Greatest changes in EMG activity and kinetics were seen during the first 2 km. CONCLUSION: After initial adjustment, the runners are able to maintain submaximal running speed with very little changes in running economy, kinetics and kinematics. However, fatigue-induced impairment in the force generating capacity of the contractile component can be revealed by tests measuring maximum performance.     

Maximal strength training improves aerobic endurance performance

The aim of this experiment was to examine the effects of maximal strength training with emphasis on neural adaptations on strength- and endurance-performance for endurance trained athletes. Nineteen male cross-country skiers about 19.7 +/- 4.0 years of age and a maximal oxygen uptake (VO(2 max)) of 69.4 +/- 2.2 mL x kg(-1) x min(-1) were randomly assigned to a training group (n = 9) or a control group (n = 10). Strength training was performed, three times a week for 8 weeks, using a cable pulley simulating the movements in double poling in cross-country skiing, and consisted of three sets of six repetitions at a workload of 85% of one repetition maximum emphasizing maximal mobilization of force in the concentric movement. One repetition maximum improved significantly from 40.3 +/- 4.5 to 44.3 +/- 4.9 kg. Time to peak force (TPF) was reduced by 50 and 60% on two different submaximal workloads. Endurance performance measured as time to exhaustion (TTE) on a double poling ski ergometer at maximum aerobic velocity, improved from 6.49 to 10.18 min; 20.5% over the control group. Work economy changed significantly from 1.02 +/- 0.14 to 0.74 +/- 0.10 mL x kg(-0.67) x min(-1). Maximal strength training with emphasis on neural adaptations improves strength, particularly rate of force development, and improves aerobic endurance performance by improved work economy.     

Heart rate and blood pressure variability during heavy training and overtraining in the female athlete

We investigated heavy training- and overtraining-induced changes in heart rate and blood pressure variability during supine rest and in response to head-up tilt in female endurance athletes. Nine young female experimental athletes (ETG) increased their training volume at the intensity of 70-90% of maximal oxygen uptake (VO2max) by 125% and training volume at the intensity of < 70% of VO2max by 100% during 6-9 weeks. The corresponding increases in 6 female control athletes were 5% and 10%. The VO2max of the ETG and the control athletes did not change, but it decreased from 53.0 +/- 2.2 ml x kg(-1) x min(-1) to 50.2 +/- 2.3 ml x kg(-1) x min(-1) (mean+/-SEM, p < 0.01) in five overtrained experimental athletes. In the ETG, low-frequency power of R-R interval (RRI) variability during supine rest increased from 6 +/- 1 ms2 x 10(2) to 9 +/- 2 ms2 x 10(2) (p < 0.05). The 30/15 index (= RRI(max 30)/RRI(min 15), where RRI(max 30) denotes the longest RRI close to the 30th RRI and RRI(min 15) denotes the shortest RRI close to the 15th RRI after assuming upright position in the head-up tilt test), decreased as a result of training (analysis of variance, p = 0.05). In the ETG, changes in VO2max were related to the changes in total power of RRI variability during standing (r = 0.74, p < 0.05). Heart rate response to prolonged standing after head-up tilt was either accentuated or attenuated in the overtrained athletes as compared to the normal training state. We conclude that heavy training could increase cardiac sympathetic modulation during supine rest and attenuated biphasic baroreflex-mediated response appearing just after shifting to an upright position. Heavy-training-/overtraining-induced decrease in maximal aerobic power was related to decreased heart rate variability during standing. Physiological responses to overtraining were individual.     

Running economy is negatively related to sit-and-reach test performance in international-standard distance runners.

The purpose of this study was to investigate the relationship between running economy (RE) and lower body flexibility. Thirty-four international-standard male distance runners (mean +/- s, age 27 +/- 5 years; body mass 64.9 +/- 4.2 kg; VO(2)max 72.8 +/- 3.7 ml x kg(-1) x min(-1)) gave written consent to participate in this study. The subjects performed an incremental treadmill test for the assessment of RE, lactate threshold and VO(2)max, and the sit-and-reach test was used to assess their general lower body and trunk flexibility. Running speeds below the lactate threshold were used to explore the relationship between running economy and sit-and-reach test performance. At 16.0 km x h(-1), the VO(2) was 50.6 +/- 3.7 ml x kg(-1) x min(-1) (range: 44.2 to 57.1 ml x kg(-1) x min(-1)). Pearson product moment correlation coefficients revealed no significant relationships between aerobic demand at 16.0 km x h(-1) and age (r = - 0.19), height (r = 0.15), body mass (r = - 0.18), or VO(2)max (r = - 0.004). However, there was a highly significant relationship between aerobic demand at 16.0 km x h(-1) and the sit-and-reach test score (r = 0.68; p < 0.0001). These results suggest that the least flexible runners are also the most economical. It is possible that stiffer musculotendinous structures reduce the aerobic demand of submaximal running by facilitating a greater elastic energy return during the shortening phase of the stretch-shortening cycle.     

Effect of prolonged exercise on arterial oxygen saturation in athletes susceptible to exercise-induced hypoxemia

This study examined the effect of prolonged endurance exercise on the development of exercise-induced hypoxemia (EIH) in athletes who had previously displayed EIH during an incremental maximal exercise test. Five male and three female endurance-trained athletes participated. Susceptibility to EIH was confirmed through a maximal incremental exercise test and defined as a reduction in the saturation of arterial oxygen (SpO(2)) of >/=4% from rest. Sixty minutes of running was conducted, on a separate day, at an oxygen consumption corresponding to 95% of ventilatory threshold. Immediately following the 60 min exercise bout, athletes commenced a time trial to exhaustion at 95% maximal oxygen consumption (VO(2max)). The reduction in SpO(2) was significantly greater during the maximal incremental test, than during the 60 min, or time trial to exhaustion (-8.8+/-1.4%, -3.3+/-1.1%, and -4.1+/-2.3%, P<0.05, respectively). The degree of desaturation during the 60 min was significantly related to the relative intensity of exercise at 95% ventilatory threshold (adjusted r(2)=0.54, P=0.02). In conclusion, athletes who did not exercise at greater than 73% VO(2max) during 60 min of endurance exercise did not display EIH, despite being previously susceptible during an incremental maximal test.     

Blood lactate at 12 km/h and vOBLA as predictors of run performance in non-endurance athletes

Run velocity at the onset of blood lactate accumulation (vOBLA) has been reported to be highly correlated with performance in endurance runs. From capillary blood samples taken during incremental treadmill running, vOBLA and the blood lactate concentration at a run speed of 12 km/h (La12) were determined in a group of 11 men which excluded endurance athletes. The inter-relationships between these variables, 4-km run performance and maximal oxygen uptake (VO2max) were investigated. vOBLA and La12 were highly correlated with one another (r = -0.95). Mean 4-km run speed was found to be closely related to vOBLA (r = 0.86), La12 (r = -0.88) and VO2max (r = 0.86). Reproducibility of both vOBLA and La12 was found to be good; test and re-test scores were highly correlated (r greater than or equal to 0.93) and did not differ significantly (p greater than 0.05). The present study suggests that vOBLA may be a valid and reproducible predictor of run performance in individuals who are not endurance athletes. It was not, however, found to be better in these respects than La12, the measurement of which would be easier and less traumatic to the subject since it would require less blood sampling.