Home About us Contact
|
Home About us Contact | ||
|
|
||
Maximal Speed (maximal + speed)
Selected AbstractsEvolutionary relationships of sprint speed in Australian varanid lizardsJOURNAL OF ZOOLOGY, Issue 4 2009C. J. Clemente Abstract Ecomorphological studies often seek to link morphology and performance to relevant ecological characteristics. Varanid lizards are unique in that species can vary in body size by almost four orders of magnitude within a single genus, and a question of considerable interest is whether similar ecomorphological relationships exist when constraints on body size are reduced. We studied sprint speed in relation to size, shape and ecology for 18 species of varanid lizards. Maximal speed scaled positively with mass0.166 using least squares regression, and mass0.21 using reduced major-axis regression. However, a curvilinear trend better described this relationship, suggesting an optimal mass of 2.83 kg with respect to speed. Including data for the komodo dragon Varanus komodoensis moves the optimum mass to 2.23 kg. We use this relationship to predict the sprint speed of the Komodo's giant extinct relative Varanus (Megalania) prisca to be 2.6,3 m s,1 similar to that of extant freshwater crocodiles Crocodylus johnstoni. When differences in speed were compared to ecological characteristics, species from open habitats were significantly faster than species from semi-open or closed habitat types, and remained so after correction for size and phylogeny. Thus, despite large variation in body size, varanids appear to share similar associations between performance and ecology as seen in other lizard groups. Varanids did, however, differ in morphological relationships with sprint speed. Differences in relative speed were not related to relative hindlimb length, as is commonly reported for other lizard groups. Instead, size-free forefoot length was negatively related to speed as was the size-free thorax,abdomen length. While shorter forefeet were thought to be an adaptation to burrowing, and thus open habitats, rather than speed per se, the reduction in the thorax,abdomen length may have significant advantages to increasing speed. Biomechanical models predicting this advantage are discussed in relation to a trade-off between speed and manoeuvrability. [source] Effect of conditioning horses with short intervals at high speed on biochemical variables in bloodEQUINE VETERINARY JOURNAL, Issue S36 2006A. LINDNER Summary Reasons for performing study: There is limited published work on the effect of training using intensive and short intervals of exercise to condition horses for racing. Objectives: To examine the effect of conditioning horses 1, 2 or 3 x a week using 2 short fast exercise intervals on blood lactate (LA), plasma ammonia (NH3) and urea (urea) as well as creatine kinase (CK) activity. Methods: Thoroughbreds (age 4,5 years) were conditioned at near maximal speed (12,14 m/sec) over 100 m, on 2 occasions separated by a 10 min period at walk, on dirt track (conditioning exercise; CE) during a 6 week conditioning period (CP). The CE was undertaken either once (5 horses), twice (5 horses) or 3 times a week (4 horses) during a CP. Before, every 2 weeks during and after the CP, blood was drawn during the CE at 0, 2 and 4 min after each run and additionally 6 min after the 2nd run to measure blood LA and determine the maximal LA post exercise (LAmax). Plasma NH3 was measured in the same samples and the maximal NH3 post exercise (NH3max) determined. Additional blood samples were taken from the horses when stabled before the CE, and 12 and 24 h after to measure urea and CK activity in plasma. Results: There was no differential effect of the number of weekly CE on LAmax, NH3max, LA and NH3 immediately after exercise (LAO and NH30). Conditioning did not have an effect on LAmax and LAO after the 1st interval (P>0.05), but LAO after the 2nd interval was lower after conditioning. NH3max after the 1st and 2nd exercise interval decreased in response to the conditioning, but not NH3 immediately after exercise (P>0.05). Median plasma CK activity 12 h after exercise was higher than before exercise and returned to pre-exercise levels 24 h post exercise when horses were exercised once and twice/week. In contrast, the median plasma CK activity of horses exercising 3 times/week remained at the pre-exercise level 12 and 24 h post exercise (P>0.05). Conclusion: Conditioning horses with 2 intervals of 100 m at near maximal speed had a positive effect on blood LA and plasma NH3. Potential relevance: With the type of exercise examined, the fitness of racing horses can be maintained and eventually improved. In further studies the effect of increasing the number of runs in one exercise session should be investigated. [source] Behavioral tradeoffs when dispersing across a patchy landscapeOIKOS, Issue 2 2005Patrick A. Zollner A better understanding of the behavior of dispersing animals will assist in determining the factors that limit their success and ultimately help improve the way dispersal is incorporated into population models. To that end, we used a simulation model to investigate three questions about behavioral tradeoffs that dispersing animals might face: (i) speed of movement against risk of predation, (ii) speed of movement against foraging, and (iii) perceptual range against risk of predation. The first investigation demonstrated that dispersing animals can generally benefit by slowing from maximal speed to perform anti-predatory behavior. The optimal speed was most strongly influenced by the disperser's energetic reserves, the risk of predation it faced, the interaction between these two parameters, and the effectiveness of its anti-predatory behavior. Patch arrangement and the search strategy employed by the dispersers had marginal effects on this tradeoff relative to the above parameters. The second investigation demonstrated that slowing movement to forage during dispersal may increase success and that optimum speed of dispersal was primarily a function of the dispersing animal's energetic reserves, predation risk, and their interaction. The richness (density of food resources) of the interpatch matrix and the patch arrangement had relatively minor impacts on how much time a dispersing animal should spend foraging. The final investigation demonstrated animals may face tradeoffs between dispersing under conditions that involve a low risk of predation but limit their ability to perceive distant habitat (necessitating more time spent searching for habitat) and conditions that are inherently more risky but allow animals to perceive distant habitat more readily. The precise nature of this tradeoff was sensitive to the form of the relationship between predation risk and perceptual range. Our overall results suggest that simple depictions of these behavioral tradeoffs might suffice in spatially explicit population models. [source] MAXIMAL LACTATE STEADY STATE IN RUNNING MICE: EFFECT OF EXERCISE TRAININGCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2007Julio CB Ferreira SUMMARY 1Maximal lactate steady state (MLSS) corresponds to the highest blood lactate concentration (MLSSc) and workload (MLSSw) that can be maintained over time without continual blood lactate accumulation and is considered an important marker of endurance exercise capacity. The present study was undertaken to determine MLSSw and MLSSc in running mice. In addition, we provide an exercise training protocol for mice based on MLSSw. 2Maximal lactate steady state was determined by blood sampling during multiple sessions of constant-load exercise varying from 9 to 21 m/min in adult male C57BL/6J mice. The constant-load test lasted at least 21 min. The blood lactate concentration was analysed at rest and then at 7 min intervals during exercise. 3The MLSSw was found to be 15.1 ± 0.7 m/min and corresponded to 60 ± 2% of maximal speed achieved during the incremental exercise testing. Intra- and interobserver variability of MLSSc showed reproducible findings. Exercise training was performed at MLSSw over a period of 8 weeks for 1 h/day and 5 days/week. Exercise training led to resting bradycardia (21%) and increased running performance (28%). Of interest, the MLSSw of trained mice was significantly higher than that in sedentary littermates (19.0 ± 0.5 vs 14.2 ± 0.5 m/min; P = 0.05), whereas MLSSc remained unchanged (3.0 mmol/L). 4Altogether, we provide a valid and reliable protocol to improve endurance exercise capacity in mice performed at highest workload with predominant aerobic metabolism based on MLSS assessment. [source] Intensity of Nordic Walking in young females with different peak O2 consumptionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2009Toivo Jürimäe Summary The purpose of this cross - sectional study was to determine the physiological reaction to the different intensity Nordic Walking exercise in young females with different aerobic capacity values. Twenty-eight 19,24-year-old female university students participated in the study. Their peak O2 consumption (VO2 peak kg,1) and individual ventilatory threshold (IVT) were measured using a continuous incremental protocol until volitional exhaustion on treadmill. The subjects were analysed as a whole group (n = 28) and were also divided into three groups based on the measured VO2 peak kg,1 (Difference between groups is 1 SD) as follows: 1. >46 ml min,1 kg,1 (n = 8), 2. 41,46 ml min,1 kg,1 (n = 12) and 3. <41 ml min,1 kg,1 (n = 8). The second test consisted of four times 1 km Nordic Walking with increasing speed on the 200 m indoor track, performed as a continuous study (Step 1 , slow walking, Step 2 , usual speed walking, Step 3 , faster speed walking and Step 4 , maximal speed walking). During the walking test expired gas was sampled breath-by-breath and heart rate (HR) was recorded continuously. Ratings of perceived exertion (RPE) were asked using the Borg RPE scale separately for every 1 km of the walking test. No significant differences emerged between groups in HR of IVT (172·4 ± 10·3,176·4 ± 4·9 beats min,1) or maximal HR (190·1 ± 7·3,191·6 ± 7·8 beats min,1) during the treadmill test. During maximal speed walking the speed (7·4 ± 0·4,7·5 ± 0·6 km h,1) and O2 consumption (30·4 ± 3·9,34·0 ± 4·5 ml min,1 kg,1) were relatively similar between groups (P > 0·05). However, during maximal speed walking, the O2 consumption in the second and third groups was similar with the IVT (94·9 ± 17·5% and 99·4 ± 15·5%, respectively) but in the first group it was only 75·5 ± 8·0% from IVT. Mean HR during the maximal speed walking was in the first group 151·6 ± 12·5 beats min,1, in the second (169·7 ± 10·3 beats min,1) and the third (173·1 ± 15·8 beats min,1) groups it was comparable with the calculated IVT level. The Borg RPE was very low in every group (11·9 ± 2·0,14·4 ± 2·3) and the relationship with VO2and HR was not significant during maximal speed Nordic Walking. In summary, the present study indicated that walking is an acceptable exercise for young females independent of their initial VO2 peak level. However, females with low initial VO2 peak can be recommended to exercise with the subjective ,faster speed walking'. In contrast, females with high initial VO2 peak should exercise with maximal speed. [source] | |||||||||||||