Peak Running Speed Research Articles

Acute Exercise And Monocarboxylate Transporter (mct)1 And Mct4 In Thoroughbred Horses

MCT (monocarboxylate transporter) 1 and MCT4 are known as the key lactate transporters in skeletal muscle. As a part of lactate shuttle, MCT1 facilitates uptake of lactate, while MCT4 facilitates lactate extrusion. Thoroughbred horses are athletes with a high capacity for exercise. They have exceptionally high maximal oxygen uptake, and a high amount of energy stored as glycogen in the muscles. Blood lactate concentration reaches 30 - 40 mmol during exercise. Although it is suggested that MCT1 and MCT4 play an important role during exercise in horses, it is still not known that whether acute exercise can increase MCT1 and MCT4 protein content in horses. PURPOSE: To investigate effects of acute exercise on MCT1, MCT4 and lactate metabolism in Thoroughbreds muscle. METHODS: Six Thoroughbred horses (3-4 years old; 3 males and 3 females) were given an incremental exercise test (IET). The speed of treadmill was increased by 2 m/s every minute from 6 m/s until the horse could not maintain its position on the treadmill from exhaustion. Blood samples are taken during IET. Muscle samples were obtained from the middle gluteus muscle before and after 0, 3, 6, and 24 hours from IET. Protein contents of MCT1 and MCT4 were measured by Western blotting. RESULTS: The average VO2max was 168.5 ± 4.4 ml/kg/min. Peak running speed was 13.3 ± 0.4 m/s. Plasma lactate concentration at exhaustion was 23.2 ± 3.0 mmol. The protein contents of MCT1 and MCT4 were increased after 6 hours from IET (+19 and +34% vs PRE, respectively; P<0.05) and returned to the pre-training value after 24 hours. Muscle glycogen concentration was decreased after IET (-50% vs PRE, P<0.01) and remained decreased after 3 and 6 hours (-30% and -19% vs PRE, respectively; P<0.05), and returned to the pre-training value after 24 hours from IET. CONCLUSIONS: This study showed that MCT1 and MCT4 proteins can be increased by acute exercise. Therefore, MCT1 and MCT4 might belong to genes that are very rapidly up-regulated with an exercise stimulus.

Alternative methods of normalising EMG during running

We evaluated possible methods of normalising EMG measured during running. MVC, Sprint and 70% Peak Running Speed methods were evaluated and their repeatability, reliability and sensitivity to incremental running speed were compared. Twelve runners performed the same experimental protocol on three separate occasions. Each day, subjects firstly performed MVCs, followed by a 20 m maximal sprint (with a 20–30 m run-up). Following this, they performed the peak running speed (PRS) test until exhaustion. After which they ran at 70% of PRS for 5 laps. Results indicated that normalising EMG data to MVC and Sprint methods are more repeatable for VM, BF, MG and RF, VL, LG, respectively, with the average ICC > 0.80. The 70% PRS demonstrated poor to fair levels of repeatability ranging between ICC 0.27 and 0.70. Whereas the 70% PRS method had the least intra-subject variability and the greatest sensitivity to increasing running speeds. More specifically, demonstrating significant changes in muscle activity in VM with increasing running speed while MVC and Sprint methods were unable to detect these changes. The dynamic methods were the most appropriate for EMG normalisation showing repeatability, better intra-subject reliability and better sensitivity during running over different days and for once-off measurements.

Reliability and Validity of a Novel Intermittent Peak Running Speed Test for Australian Football

Australian football requires frequent intermittent sprinting close to peak running speed. However, tests assessing the capability to maintain intermittent peak running speed are not reported in scientific literature. Therefore, our objective is to report the reliability and validity of a novel intermittent peak running speed test. The intermittent peak running speed test required footballers to perform 10 repetitions on 25-second intervals. Each repetition required 15-m jogging, 20-m acceleration to peak speed, 10 m to sustain peak speed, 20-m deceleration, and finally a 15-m jog. Intermittent peak running speed was determined by portable global positioning system. To assess reliability, 26 footballers performed the intermittent peak running speed test on 2 occasions 3-5 days apart. Our results revealed that average peak speed had a coefficient of variation of 2.2% and an intraclass correlation of 0.91. To assess construct validity, average peak speed was compared between elite, sub-elite, and regional footballers. The average peak speed of the elite footballers (28.6 ± 1.7 km · h(-1)) was higher than that of the sub-elite (27.4 ± 1.7 km · h(-1)) and regional (27 ± 1.9 km · h(-1)) competitors (p < 0.05). Our study revealed that the intermittent peak running speed test possesses acceptable reliability and distinguishes between elite and sub-elite footballers.

Match Running Performance and Fitness in Youth Soccer

The activity profiles of highly trained young soccer players were examined in relation to age, playing position and physical capacity. Time-motion analyses (global positioning system) were performed on 77 (U13-U18; fullbacks [FB], centre-backs [CB], midfielders [MD], wide midfielders [W], second strikers [2 (nd)S] and strikers [S]) during 42 international club games. Total distance covered (TD) and very high-intensity activities (VHIA; >16.1 km·h (-1)) were computed during 186 entire player-matches. Physical capacity was assessed via field test measures (e. g., peak running speed during an incremental field test, VVam-eval). Match running performance showed an increasing trend with age ( P<0.001, partial eta-squared (η (2)): 0.20-0.45). When adjusted for age and individual playing time, match running performance was position-dependent ( P<0.001, η (2): 0.13-0.40). MD covered the greater TD; CB the lowest ( P<0.05). Distance for VHIA was lower for CB compared with all other positions ( P<0.05); W and S displayed the highest VHIA ( P<0.05). Relationships between match running performance and physical capacities were position-dependent, with poor or non-significant correlations within FB, CB, MD and W (e. g., VHIA vs. VVam-eval: R=0.06 in FB) but large associations within 2 (nd)S and S positions (e. g., VHIA vs. VVam-eval: R=0.70 in 2 (nd)S). In highly trained young soccer players, the importance of fitness level as a determinant of match running performance should be regarded as a function of playing position.

Physiological Measures Tracking Seasonal Changes in Peak Running Speed

It is unclear whether physiological measures monitored in an incremental treadmill test during a training season provide useful diagnostic information about changes in distance running performance. To quantify the relationship between changes in physiological measures and performance (peak running speed) over a training season. Well-trained distance runners (34 males; VO2max 64 +/- 6 mL x kg(-1) x min(-1), mean +/- SD) completed four incremental treadmill tests over 17 wk. The tests provided values of peak running speed, VO2max, running economy, and lactate threshold (as speed and %VO2max). The physiological measures were included in simple and multiple linear regression models to quantify the relationship between changes in these measures and changes in peak speed. The typical within-subject variation in peak speed from test to test was 2.5%, whereas those for physiological measures were VO2max (mL x min(-1) x kg(-1)) 3.0%, economy (m x kg x mL(-1)) 3.6%, lactate threshold (%VO2max) 8.7%, and body mass 1.8%. In simple models these typical changes predicted the following changes in performance: VO2max 1.4%, economy 0.8%, lactate threshold -0.3%, and body mass -0.2% (90% confidence limits approximately +/-0.7%); the corresponding correlations with performance were 0.57, 0.33, -0.05, and -0.13 respectively (approximately +/-0.20). In a multiple linear regression model, the contribution of each physiological variable to performance changed little after adjustment for the other variables. Change in VO2max in an incremental test during a running season is a good predictor of change in peak running speed, change in running economy is a moderate predictor, and lactate threshold and body mass provide little additional information.

Effects Of Dietary Antioxidants On Training And Performance In Runners

Some athletes believe that consumption of antioxidant supplements improve training, but such supplements could impair training by attenuating adaptive responses to the oxidative stress of exercise. PURPOSE: To investigate the effects of daily ingestion of antioxidants in the form of a vitamin-C megadose or blackcurrant juice on antioxidant status, training and performance in runners. METHODS: Twenty-three trained female runners (age, 31 ± 8 y; maximum oxygen consumption, 49 ± 4 ml.min-1.kg-1; incremental peak running speed, 16.6 ± 1.5 km.h-1; mean ± SD) completed three 3-wk blocks of high-intensity training sessions (2-3 per week) separated by washout periods of 4 wk. Each session consisted of four 3- to 5-min timed hill repetitions and six 2-min intense hill repetitions. During each block they consumed daily supplements of either vitamin C (1000 mg), blackcurrant juice (15 mg vitamin C, 300 mg anthocyanins) or placebo as isocaloric drinks in crossover fashion. Blood samples were taken for assessment of anti-oxidant status. Performance was assessed with an incremental treadmill test after each block and a 5-km road time-trial before and after each block. Effects of supplements were compared with a mixed linear model and magnitude-based inferences, using performance before each block to adjust for individual differences in the washout. RESULTS: Compared with placebo, there was a harmful clear effect on mean running speed during training with vitamin C (-1.3%; 90% confidence limits ±1.3%) and blackcurrant juice (-1.0%; ±1.3%), but effects on mean performance in the incremental test and time trial were unclear. Relative to placebo, some markers of oxidative stressed showed small increases with vitamin C and small increases or decreases with blackcurrant extract: erythrocyte catalase at rest, 23% and 13% (±21%); uric acid in exercise, 4.9% and 8.1% (±9.5%); protein carbonyls at rest, 27% and -6% (±38%); erythrocyte superoxide dismutase in exercise, 8.3% and -4.1% (±9.3%); and plasma malondialdehyde, 2% and -11% (±15%). Other effects of antioxidants, including those on erythrocyte malondialdehyde and glutathione, were trivial or unclear. CONCLUSION: Dietary antioxidants appear to reduce intensity of hard training intervals in runners, and vitamin C may act as a pro-oxidant.

The consistency of maximum running speed measurements in humans using a feedback-controlled treadmill, and a comparison with maximum attainable speed during overground locomotion

Consistent measurement of maximum running speed overground is problematic due to the difficulty in precise, continual measurement of speed, and the substantial workload in accelerating the body promoting the onset of fatigue. Treadmills remove the requirement for acceleration which enables more repeats. They also allow experiments to be carried out in controlled environments and where space is limited, but they usually depend on manual and subjective speed control. Here we used a draw-wire position sensor and a proportional–derivative (PD) controller to automatically adjust treadmill belt speed of a large equine treadmill. The feedback loop took the real-time position and velocity of the runner relative to the front of the treadmill as input. This control system allowed runners to accelerate from walking speed to a peak running speed within a few strides and then decelerate as quickly as they wished. We used the system to evaluate the variation in maximum speed determination that results from one trial to 10 trials, in eleven individuals. Three trials gave a maximum speed 97.8% of that achieved after ten. The approach used is appropriate for any treadmill where the running zone length is greater than three metres and the speed controller can be externally controlled. Subjects ran 11.5% faster on the treadmill than overground, part of which can be explained by the removal of aerodynamic drag and the fatigue of overground running. Additional factors may, however, contribute to athletes running faster on a treadmill, for instance some aspect of stability or control.

Do Seasonal Changes In Physiological Measures In An Incremental Running Test Track Peak Running Speed?

It is unclear whether physiological measures monitored in an incremental test during a training season provide useful diagnostic information about changes in distance running performance. PURPOSE: To quantify the relationship between changes in physiological measures and performance (peak running speed) over a winter training season. METHODS: Well-trained male distance runners (n=34, age 35.2 ± 1.1 y, VO2max 64.5 ± 6.2 ml.kg−1.min−1, training for 9.5 ± 0.9 h.wk−1, mean ± SD) completed four incremental treadmill tests over 17 wk. The test provided values of peak running speed, VO2max, running economy, and 4 mM lactate threshold (as speed and fraction of VO2max). The physiological measures were included in simple and multiple linear regression mixed models to quantify the effect of changes in these measures on changes in peak speed. RESULTS: The within-subject typical variation in peak speed from test to test was 1.9%, whereas those for physiological measures were: VO2max, 2.5%; economy, 2.6%; lactate threshold speed, 6.2%; lactate threshold fraction, 6.5%; and body mass, 1.6%. In simple models these typical changes in physiological variables predicted the following changes in performance: VO2max, 1.2% (90% confidence limits ±0.2%); economy, 0.5% (±0.3%); lactate threshold speed, 0.5% (±0.3%); lactate threshold fraction,−0.3% (±0.3%); and body mass,−0.4% (±0.3%). After adjustment for other predictors in a multiple linear regression, the effect of VO2max on peak speed was not diminished, but economy became a marginal predictor, while lactate threshold and body mass became ineffective. CONCLUSION: Change in VO2max in an incremental test during a running season is a good physiological predictor of change in peak running speed. Changes in running economy, lactate threshold and body mass provided little additional information about changes in performance.

Variation in Top Level Soccer Match Performance

This study examined the influence of the opposing team, seasonal variations and the influence of first half activity on match performance in top-level soccer players. Physical performance measures were collected using the ProZone match analysis system from 20 professional soccer players from the same team and their opponents (n = 188) during a season. Match activities (standing, walking, jogging, running, high-speed running and sprinting), distances (total distance [TD], high-intensity running [HIR] and very high-intensity running [VHIR]) and other measures including involvement with the ball and peak running speed were collected. The influence of opponent team, the level of opposition, first half physical activities on second half activities, and playing position were analysed. The main finding was that TD (r = 0.62, p < 0.05), HIR (r = 0.51, p < 0.05), and VHIR (r = 0.65, p < 0.05) of the reference team was influenced by the activity profile of the opponent teams. The TD and HIR was higher against Best opponent teams compared to Worst opponent teams (p < 0.05), and the TD, HIR and VHIR travelled in the first half significantly influenced the distances covered in the second half. TD, HIR and VHIR were greater at the end of the season. These results may be used to interpret meaningful changes in match performance in top level soccer.

A modified TRIMP to quantify the in-season training load of team sport players

The aims of the study were to modify the training impulse (TRIMP) method of quantifying training load for use with intermittent team sports, and to examine the relationship between this modified TRIMP (TRIMPMOD) and changes in the physiological profile of team sport players during a competitive season. Eight male field hockey players, participating in the English Premier Division, took part in the study (mean±s: age 26±4 years, body mass 80.8±5.2 kg, stature 1.82±0.04 m). Participants performed three treadmill exercise tests at the start of the competitive season and mid-season: a submaximal test to establish the treadmill speed at a blood lactate concentration of 4 mmol · l−1; a maximal incremental test to determine maximal oxygen uptake ([Vdot]O2max) and peak running speed; and an all-out constant-load test to determine time to exhaustion. Heart rate was recorded during all training sessions and match-play, from which TRIMPMOD was calculated. Mean weekly TRIMPMOD was correlated with the change in [Vdot]O2max and treadmill speed at a blood lactate concentration of 4 mmol · l−1 from the start of to mid-season (P<0.05). The results suggest that TRIMPMOD is a means of quantifying training load in team sports and can be used to prescribe training for the maintenance or improvement of aerobic fitness during the competitive season.

Exercise capacity and exercise-induced bronchoconstriction (EIB) in a cold environment

Exercise in a cold environment has been reported to increase exercise-induced bronchoconstriction (EIB). However, the effect of a cold environment upon exercise capacity in subjects with EIB has, to our knowledge, not been previously reported. Primary: To examine the influence of changing environmental temperature upon exercise capacity measured by peak oxygen uptake (VO(2 peak)), peak ventilation (VE(peak)) and peak running speed in subjects with diagnosed EIB. Secondary: To assess the influence of changing environmental temperature upon EIB. Twenty subjects (10-45 years old, male/female: 13/7) with EIB underwent exercise testing by running on a treadmill in a climate chamber under standardised, regular conditions, 20.2 degrees C (+/-1.1) and 40.0% (+/-3.3) relative humidity [mean(+/-SD)], and in a standardised cold environment, -18.0 degrees C (+/-1.4) and 39.2% (+/-3.8) relative humidity in random order on separate days. Oxygen uptake (VO(2)), minute ventilation (V E), respiratory exchange ratio (RER), heart rate (HR) and running speed were measured during exercise. Lung function (flow volume loops) was measured before and 1, 3, 6, 10 and 15 min after exercise and 15 min after inhalation of salbutamol. VO(2 peak) decreased 6.5%, from 47.9 (45.0, 50.8) to 44.8 ml kg(-1)min(-1) (41.2, 48.4) [mean (95% confidence intervals)] (p=0.004) in the cold environment. Also running speed was significantly lower in the cold environment (p=0.02). No differences were found for VE(peak), RER(peak) or HR(peak). The post-exercise reduction in forced expiratory volume in 1s (FEV(1)) (DeltaFEV(1)) increased significantly from 24% (19,29) to 31% (24,38), respectively (p=0.04) after exercise in the cold environment. No correlation was found between reduction in VO(2 peak) and the increased maximum fall in FEV(1) in the cold environment. Exercise capacity (VO(2 peak) and peak running speed) was markedly reduced during exercise in a cold environment whereas EIB increased in subjects suffering from EIB.

Effect of recovery modality on 4-hour repeated treadmill running performance and changes in physiological variables

The purpose of this study was to compare the effectiveness of three different recovery modalities--active (ACT), passive (PAS) and contrast temperature water immersion (CTW)--on the performance of repeated treadmill running, lactate concentration and pH. Fourteen males performed two pairs of treadmill runs to exhaustion at 120% and 90% of peak running speed (PRS) over a 4-hour period. ACT, PAS or CTW was performed for 15-min after the first pair of treadmill runs. ACT consisted of running at 40% PRS, PAS consisted of standing stationary and CTW consisted of alternating between 60-s cold (10 degrees C) and 120-s hot (42 degrees C) water immersion. Run times were converted to time to cover set distance using critical power. Type of recovery modality did not have a significant effect on change in time to cover 400 m (Mean +/- SD; ACT 2.7 +/- 3.6 s, PAS 2.9 +/- 4.2 s, CTW 4.2 +/- 6.9 s), 1000 m (ACT 2.2 +/- 4.0 s, PAS 4.8 +/- 8.6 s, CTW 2.1 +/- 7.2 s) or 5000 m (ACT 1.4 +/- 29.0 s, PAS 16.7 +/- 58.5 s, CTW 11.7 +/- 33.0 s). Post exercise blood lactate concentration was lower in ACT and CTW compared with PAS. Participants reported an increased perception of recovery in the CTW compared with ACT and PAS. Blood pH was not significantly influenced by recovery modality. Data suggest both ACT and CTW reduce lactate accumulation after high intensity running, but high intensity treadmill running performance is returned to baseline 4-hours after the initial exercise bout regardless of the recovery strategy employed.

Locomotion in terrestrial mammals: the influence of body mass, limb length and bone proportions on speed

Traditionally a few limb proportions or total limb lengths have been regarded as indicative of peak running velocity. This is due to physical principles (inferred in- and outvelocities around the joints, stride lengths) and also the observation that fast-moving animals tend to share a number of purported key features which are either absent or not developed to near the same extent in slower moving forms. Previous studies have shown hind limb length and metatarsus/femur ratio to be correlated significantly, albeit modestly with running speed. These studies have nearly all been bivariate analyses. Based on the physical principles, there is reason to suppose that more variables than just m/f ratio could be important as adaptations for fast locomotion, and also that bivariate analyses are too simple. In this study a sample of 76 running mammals was used, with running speeds taken from literature. A number of osteological parameters were discovered to covary significantly with peak running speed, albeit only modestly. Using the information from phylogeny reduced all correlations, often significantly so. Multivariate analyses resulted in markedly higher correlation coefficients. Animals probably do not optimize their anatomy for the purpose of running very fast, which occurs only on rare occasions, but for reducing costs of locomotion. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136, 685–714.

Bovine colostrum supplementation during endurance running training improves recovery, but not performance

This study examined the effect of supplementation with concentrated bovine colostrum protein powder (intact) on plasma insulin-like growth factor I (IGF-I) concentrations, endurance running performance and recovery. Thirty physically active males completed 8 weeks of running training whilst consuming 60 g x day(-1) of intact powder (n=17) or a concentrated whey protein powder placebo (n=13) in a randomised, double-blind, parallel design. Plasma IGF-I concentrations were measured prior to subjects performing two (approximately 30 min) incremental treadmill running tests to exhaustion (RUN1 and RUN2) separated by 20 min of passive recovery at Weeks 0. 4 and 8. Plasma IGF-I concentrations showed little change in either group (p=0.83). Effective peak running speed (PRSE; i.e. equivalent of peak power) during RUN1 was not different between groups at Week 0 (p>0.99), and had increased by a similar amount in both groups by Week 4 (mean+/-SD, intact 2.2+/-4.0%, placebo 3.2+/-3.3%; 95% confidence interval [95% CI 15.7 to -13.7%; p=0.89) and Week 8 (intact 3.6+/-5.6%, placebo 3.4+/-4.4 %; 95% CI -100.0 to 100.0%; p>0.99). PRSE was less in both groups during RUN2 (p<0.05), but was not significantly different between groups at Week 0 (p>0.99). PRSE during RUN2 tended to have increased more in the placebo group by Week 4 (intact 1.8+/-4.8%, placebo 4.2+/-3.9%; 95% CI 0.2 to -5 0%; p=0.07), but the intact group had increased PRSE significantly more by Week 8 (intact 4.6+/-6.1%, placebo 2.0+/-4.5%; 95% Cl 0.0 to 5.2%; p=0.05). resulting in a significantly faster PRSE (p=0.003). We conclude that supplementation with intact powder did not increase plasma IGF-I concentrations or improve performance during an initial bout of incremental running to exhaustion in our sample. However, performance during a second bout of exercise may be improved by as much as 5.2% in the average subject after 8 weeks of supplementation, possibly due to an enhancement of recovery.

Cardiorespiratory impact of the nitric oxide synthase inhibitor l-NAME in the exercising horse

To investigate the role of nitric oxide, NO, in facilitating cardiorespiratory function during exercise, five horses ran on a treadmill at speeds that yielded 50, 80 and 100% of peak pulmonary oxygen uptake ( V ̇ O 2 peak) as determined on a maximal incremental test. Each horse underwent one control (C) and one (NO-synthase inhibitor; N G- l-nitro-arginine methyl ester ( l-NAME), 20 mg/kg) trial in randomized order. Pulmonary gas exchange (open flow system), arterial and mixed-venous blood gases, cardiac output (Fick Principle), and pulmonary and systemic conductances were determined. l-NAME reduced exercise tolerance, as well as cardiac output (C, 291±34; l-NAME, 246±38 L/min), body O 2 delivery (C, 74.4±5.5; l-NAME, 62.1±5.6 L/min), and both pulmonary (C, 3.07±0.26; l-NAME, 2.84±0.35 L/min per mmHg) and systemic (C, 1.55±0.24; l-NAME, 1.17±0.16 L/min per mmHg) effective vascular conductances at peak running speeds (all P<0.05). On the 50 and 80% trials, l-NAME increased O 2 extraction, which compensated for the reduced body O 2 delivery and prevented a fall in V ̇ O 2 . However, at peak running speed in the l-NAME trial, an elevated O 2 extraction ( P<0.05) was not sufficient to prevent V ̇ O 2 from falling consequent to the reduced O 2 delivery. At the 50 and 80% running speeds (as for peak), l-NAME reduced pulmonary and systemic effective conductances. These data demonstrate that the NO synthase inhibitor, l-NAME, induces a profound hemodynamic impairment at submaximal and peak running speeds in the horse thereby unveiling a potentially crucial role for NO in mediating endothelial function during exercise.

Intraseptal procaine abolishes hypothalamic stimulation-induced wheel- running and hippocampal theta field activity in rats

Rats were implanted chronically with hippocampal recording electrodes, a microinfusion guide cannula aimed at the medial septal nucleus, and an electrode for electrical stimulation of the posterior hypothalamic nucleus (PH). PH stimulation elicited running in rats placed in a wheel and simultaneously occurring hippocampal theta field activity (HPC-theta). In the preprocaine (PRE) testing condition, a positive linear relationship was demonstrated among the intensity of electrical stimulation of the PH, wheel-running speed, and the peak frequency of HPC-theta. HPC-theta amplitude reached an asymptote at the lowest levels of electrical stimulation of the PH. Procaine hydrochloride (1.5 microliters, 20% solution), a local anesthetic, was then infused into the medial septal nucleus (MS). Five minutes after the infusion, PH stimulation no longer induced wheel-running behavior or HPC-theta, and the remaining irregular field activity was significantly reduced in amplitude. Fifteen minutes after the procaine infusion, PH stimulation still did not elicit HPC-theta or running behavior in the majority of animals but did evoke large-amplitude sharp-waves. Thirty minutes after the procaine infusion, PH stimulation again elicited HPC-theta and running behavior, but HPC-theta peak frequency and running speeds were both significantly reduced compared with PRE values. Forty-five minutes after the infusion, HPC-theta amplitude had recovered to PRE values, but HPC-theta frequency and running speeds elicited by PH stimulation were still significantly reduced. By 60 min after procaine administration, the amplitude and frequency of HPC-theta and the running speeds elicited by PH stimulation recovered to PRE values. Multiple regression analysis revealed that the recovery pattern of running behavior reflected the frequency rather than the amplitude of HPC-theta. Neither saline control infusions into the MS nor procaine infusions into the lateral septum and paraventricular thalamic nucleus affected HPC-theta or running behavior. These findings are consistent with the notion that both the locomotor activity and "movement-related" HPC-theta frequency induced by electrically stimulating the PH were attributable to ascending activation of a hypothalamo-septal pathway and not to activation of descending brainstem or peripheral motor systems.

Oxygen delivery does not limit peak running speed during incremental downhill running to exhaustion.

Oxygen consumption (VO2), ventilation (VI), respiratory exchange ratio (R), stride frequency and blood lactate concentrations were measured continuously in nine trained athletes during two continuous incremental treadmill runs to exhaustion on gradients of either 0 degree or -3 degrees. Compared to the run at 0 degree gradient, the athletes reached significantly higher maximal treadmill velocities but significantly lower VO2, VI, R and peak blood lactate concentrations (P less than 0.001) during downhill running. These lower VO2 and blood lactate concentrations at exhaustion indicated that factors other than oxygen delivery limited maximal performance during the downhill run. In contrast, stride frequencies were similar at each treadmill velocity; the higher maximal speed during the downhill run was achieved with a significantly longer stride length (P less than 0.001); maximal stride frequency was the same between tests. Equivalent maximal stride frequencies suggested that factors determining the rate of lower limb stride recovery may have limited maximal running speed during downhill running and, possibly, also during horizontal running.

Vitamin and mineral supplementation: effect on the running performance of trained athletes

There is limited scientific justification for the widespread use of vitamin and mineral supplements by athletes. We used a 9-mo, placebo-controlled crossover study design to determine whether a multivitamin and mineral supplement influenced the athletic performance of 30 competitive male athletes. At 0, 3, 6, and 9 mo the runners performed a progressive treadmill test to volitional exhaustion for measurement of maximal oxygen consumption, peak running speed, blood lactate turnpoint, and peak postexercise blood lactate level. Running time in a 15 km time trial was also measured. None of these variables was influenced by 3 mo of active supplementation. We conclude that 3 mo of multivitamin and mineral supplementation was without any measurable ergogenic effect.

High intensity training and treadmill sprint performance.

Twelve county standard hockey players completed a 30 second sprint on a non-motorised treadmill and an uphill treadmill running test to determine maximum oxygen uptake (VO2 max) before and after 6 weeks of high intensity training (fast runs 3-5 miles, intervals 30-300 m and circuit training), whilst 11 club standard players completed the same tests without any additional training. For the county standard group there was an 11.1% and 5.0% improvement in peak running speed and distance covered on the sprint treadmill respectively, a 4.2% improvement in VO2 max and an 11.5% improvement in run time to exhaustion during the VO2 max test (all p less than 0.01). No changes were observed for the club standard group. There were large increases in blood lactate (county group 13.26 +/- 1.83 mM) and blood glucose (county group 1.56 +/- 0.71 mM) concentrations as a result of the treadmill sprint, but there were no additional changes in these variables as a result of training. Thus, the mechanism of adaptation in this type of brief maximal exercise remains in question.

Sprinting with banked turns

Bank angle effects can attenuate peak running speed on the order of 10%. Experimental and theoretical results are presented here to quantify this phenomenon over a wide range of bank angles θ b and turn radii R. Experimentally, eleven subjects ran on a 34 m long plywood test track with variable radius and bank angle to sample the ( R, θ b ) space. From another study, ten subjects are borrowed to examine the θ b = 0° case in greater detail. Various gait parameters were measured from high-speed film, and after parallax correction, compared with the theoretical predictions. The theory is a simple two-parameter constant force model requiring only the effective ankle pulley ratio β and the runner's top speed v m . A closed-form dimensionless solution is presented for the speed ratio ( v v m ) as a function of the radius number ( Rg v 2 ) and the bank angle θ b . Agreement between theory and experiment is limited by experimental scatter. For twenty different subjects and twelve different combinations of R and θ b , the apparent ankle pulley ratio is β = 0.27 ± 0.22 based on 128 separate trials. Applications are discussed briefly for the design of indoor and outdoor running tracks. The theory allows a calculation of foot force, bone force, and tendon tension for the general case of arbitrary maximum speed, turn radius and bank angle.