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Objective To predict the tissue-level failure strain of the cortical bone and discuss the effects of different running speeds on the mechanical properties of rat femoral cortical bone.Methods The threshold for cortical bone tissue-level failure strain was assigned,and fracture simulation under three-point bending was performed on a rat femoral finite element model.The predicted load-displacement curves in each simulation were compared and fitted with the experimental data to back-calculate the tissue-level failure strain.Results The cortical bone tissue-level failure strains at different running speeds were statistically different,which indicated that different running speeds had certain impacts on the micromechanical properties of the cortical bone structures.At a running speed of 12 m/min,the cortical bone structure expressed the greatest tissue-level failure strain,and at a running speed of 20 m/min,the cortical bone structure expressed the lowest tissue-level failure strain.Conclusions Based on the changing trends of tissue-level failure strain and in combination with the changes in macro-level failure load and tissue-level elastic modulus of cortical bone structures,the effects of different running speeds on the mechanical properties of cortical bone structures were discussed in this study.The appropriate running speed for improving the mechanical properties of the cortical bone was explored,thereby providing a theoretical basis for improving bone strength through running exercises.
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The aim of the present study was to analyse the lactate threshold (LT) changes in rats submitted to an aerobic treadmill-training programme. Twenty-five Wistar rats were divided into two groups: a sedentary control group (CG), and a trained group (TG) submitted to an aerobic training during 5 weeks. All the animals were submitted to an incremental treadmill exercise test in order to determine LT. There was an increase in the maximum running speed in the TG (from 32.25 ± 1.27 to 47.75 ± 3.13 m.min–1 – p = 0.001), and running speed at LT (from 26.21 ± 1.15 to 35.30 ± 2.24 m.min–1 – p = 0.004), a part from the reduction in blood lactate at LT. LT can be determined in rats, and aerobic training induced positive oxidative physiological adaptations in the animals.
O objetivo do presente estudo foi analisar as mudanças no limiar de lactato (LL) em ratos submetidos a um programa de treinamento aeróbio em esteira. Vinte e cinco ratos Wistar foram divididos em dois grupos: um grupo controle sedentário (CG), e um grupo treinado (GT) submetido a um treinamento aeróbio durante 5 semanas. Todos os animais foram submetidos a um teste de exercício incremental em esteira, a fim de determinar o LL. Houve um aumento na velocidade máxima de corrida no GT (de 32,25 ± 1,27 para 47,75 ± 3,13 m.min–1 - p = 0,001), e velocidade de corrida no LL (de 26,21 ± 1,15 para 35,30 ± 2,24 m.min–1 - p = 0,004), além da redução na concentração de lactato no LL. O LL pode ser determinado em ratos e o treinamento aeróbio induziu a adaptações fisiológicas oxidativas positivas nos animais.
Subject(s)
Animals , Male , Adaptation, Physiological/physiology , Lactates/blood , Oxygen Consumption/physiology , Physical Conditioning, Animal/physiology , Running/physiology , Rats, Wistar , Time FactorsABSTRACT
OBJECTIVES: This study investigated performance trends and the age of peak running speed in ultra-marathons from 50 to 3,100 miles. METHODS: The running speed and age of the fastest competitors in 50-, 100-, 200-, 1,000- and 3,100-mile events held worldwide from 1971 to 2012 were analyzed using single- and multi-level regression analyses. RESULTS: The number of events and competitors increased exponentially in 50- and 100-mile events. For the annual fastest runners, women improved in 50-mile events, but not men. In 100-mile events, both women and men improved their performance. In 1,000-mile events, men became slower. For the annual top ten runners, women improved in 50- and 100-mile events, whereas the performance of men remained unchanged in 50- and 3,100-mile events but improved in 100-mile events. The age of the annual fastest runners was approximately 35 years for both women and men in 50-mile events and approximately 35 years for women in 100-mile events. For men, the age of the annual fastest runners in 100-mile events was higher at 38 years. For the annual fastest runners of 1,000-mile events, the women were approximately 43 years of age, whereas for men, the age increased to 48 years of age. For the annual fastest runners of 3,100-mile events, the age in women decreased to 35 years and was approximately 39 years in men. CONCLUSION: The running speed of the fastest competitors increased for both women and men in 100-mile events but only for women in 50-mile events. The age of peak running speed increased in men with increasing race distance to approximately 45 years in 1,000-mile events, whereas it decreased to approximately 39 years in 3,100-mile events. In women, the upper age of peak running speed increased to approximately 51 years in 3,100-mile events. .
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Young Adult , Age Factors , Athletic Performance/physiology , Running/physiology , Physical Endurance/physiology , Regression Analysis , Sex Factors , Time FactorsABSTRACT
Comparou-se a velocidade de corrida no limiar de lactato (vLL) determinada pelo método Dmax utilizando-se os ajustes de curva exponencial mais constante (vLLexp) e polinomial de terceira ordem (vLLpol). Dezessete corredoras recreacionais realizaram um teste incremental descontínuo em esteira rolante até a exaustão voluntária com coleta de sangue entre os estágios para análise do lactato. A vLL Exp (10,9 ± 0,8 km/h) foi estatisticamente diferente (P < 0,05) da vLL Pol (10,4 ± 1,1 km/h) utilizando-se o teste t de Student pareado. A correlação entre a vLL Exp e a vLL Pol foi de r = 0,84. As correlações entre a velocidade pico e as vLL foram r = 0,94 (vLLexp) e r = 0,69 (vLLpol). Foi concluído que a escolha da curva de regressão do lactato sanguíneo influi no valor da vLL, sendo a vLLpol consistentemente inferior à vLLexp.
The running speed at lactate threshold (vLT) determined by the Dmax method was compared using the exponential plus constant (vLTexp) and third level polynomial (vLTpol) curve fitting. Seventeen female recreational runners underwent a treadmill incremental test until voluntary exhaustion. Blood samples were collected between the stages for lactate analysis. The vLTexp (10.9 ± 0.8 km/h) was statistically different (P < 0.05) from vLTpol (10.4 ± 1.1 km/h) using paired Student's t test. The correlation between vLTexp and vLTpol was r = 0.84. The correlations between peak speed and vLT were r = 0.94 (vLTexp) and r = 0.69 (vLTpol). It was concluded that the choice of the blood lactate regression curve influences the vLT value, in which the vLTpol was consistently lower than the vLTexp.
Se comparó la velocidad de carrera en el umbral de lactato (vLL) determinado por el método Dmax utilizando la curva exponencial más constante (vLLexp) y polinómica de tercer grado (vLLpol). Diecisiete corredoras recreativas ejecutaron una prueba incremental discontinua en la cinta rodante hasta la extenuación voluntaria con la extracción de sangre entre las etapas para el análisis de lactato. La vLL Exp (10,9 ± 0,8 km/h) fue estadísticamente diferente (P < 0,05) de la vLL Pol (10,4 ± 1,1 km/h) mediante la prueba t de Student pareado. La correlación entre vLL Exp y vLL Pol fue de r = 0,84. Las correlaciones entre el pico de velocidad y las vLL fueron de r = 0,94 (vLLexp) y r = 0,69 (vLLpol). Fue concluido que la elección de la curva de regresión de lactato sanguíneo influye en el valor de la vLL, siendo la vLLpol sistemáticamente inferior a la vLLexp.
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Objective To measure the activity energy expenditure(AEE) of healthy adults during level walking by using indirect calorimetry,and to analyze the characteristics and underlying influencing factors such as age and gender. Methods A total of 60 healthy adults aged 20-50 years (30 males and 30 femdes) participated in the study.All the subjects were divided into six groups by gender and age (the age span of each group was 10 years). The subjects were arranged to walk at speeds of 3.5,4.5,5.5km/h and run at 5.5,6.5,7.5km/h, respectively, on the treadmill. The resting energy expenditure ( REE ) and AEE were measured during walking and running at different speeds.There was a 5-minute rest among the test sessions. Results No difference in terms of AEE between the female and male at the same age ( P ＞ 0. 05 ). During 3.5km/h walking,AEE of 21-30 year-old females was lower than 31-40 yearold females and males( P ＜0.05 ) ;During 4.5km/h walking,AEE of 31-40 year-old females was higher than 21-30 yearold females and males and 41-50 year-old females; AEE of 21-30 year-old females was lower than 41-50 year-old males (P ＜ 0.05 ) ;During 5.5km/h walking,AEE of 31-40 year-old females was higher than 21-30 year-old females and males ( P ＜ 0. 05 ). During 6.5 km/h running, AEE of 31-40 year-old females was higher than 41-50 year-old females ( P ＜0.05), while during 7.5km/h running, AEE of 21-30 year-old males was higher than 41-50 year-old females (P ＜0.05 ). It was also found that the AEE of all groups except the 41-50 year-old females group was higher when walking at the speed of 5.5km/h than running at the same speed( P ＜ 0.05 ). Conclusions Age has more effect on REE and AEE than the gender. AEE of elder subjects is higher than that of the younger ones during walking, however, AEE of younger people increases faster than the elders during running. AEE of 31-40 year-old females is the highest in all groups both in walking and running. AEE in running is higher than in walking at the same speed.
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Effects of running speed and duration on a treadmill on bone properties were investigated in ovariectomized (OVX) mice. Sixty female ICR mice, twelve-weeks-old, were used in this study. They were divided into six groups of 10 mice each : either the SHAM, OVX, OVX+running groups (AS, AL, BS, BL), randomly. Running groups ran on the treadmill at 8 (A) or 16 (B) m/min, for 25 (S) or 50 (L) min, 5 days/week, for 10 weeks, respectively. After this, both femur and tibia bones were excised from the hind limb, and removed off surrounding tissues. Thereafter, bone mechanical strength (3 point bending test), dry bone weight and also ash content of the bones were determined. Bone mechanical strength and ash content of the femur and tibia in AL, BS, and BL mice were significantly higher than those in OVX mice. Running speed had effects on the bone mechanical strength and ash content of both bones significantly. Group BL showed the maximum values in bone properties among the running groups. This study suggested that a combination of running speed and duration could affect bone properties more significantly than the amount of exercise alone.
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In order to give more effective instruction for running in sports medicine, the mechanical stresses in the knee joint during running at various speeds and step lengths were investigated.<BR>The subjects were five male sprinters. Running conditions were as follows : 1) running at four speeds (2.5 m/s, 4.5 m/s, 6.5 m/s and maximum running speed) with natural step lengths, 2) run-ning with three different step lengths (1.0 m, 1.5m and preferred step length) at 4.5 m/s running speed, and 3) running at maximum speed using four different step lengths (1.0 m, 1.5m 2.5m and preferred step length) . Running movements were recorded using a high speed video camera. And ground reaction forces were also measured by a force platform. The compressive force and shear force in the tibiofemoral joint were computed from the results of two dimensional motion analysis. That is, the external force caused by ground reaction forces, the internal force produced by the mus-cle to develop joint torque and total force (external+internal force) were computed for both com-pressive and shear forces.<BR>The total compressive force that affects the meniscus and articular cartilage in the tibiofemoral joint depended on the magnitude of internal force. The total compressive force increased with running speed and step length. Therefore, caution should be employed in changing running speed and step length for regulating the magnitude of total compressive force on the tibiofemoral joint. On the other hand, the total shear force that caused traction stress in the posterior cruciate ligament depended on the magnitude of external force. The posterior shear force was generated during the foot contact period, and increased with step length. As for total shear force in the tibiofemoral joint, care must be taken to regulate step length.
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The influence of aerobic and anaerobic components of muscular endurance on the lower limbs, on sprint ability while under conditions of muscular fatigue, was investigated. Fifteen track and field athletes (400 m sprinters, decathletes and middle distance runners) participated in the study in which running and sprinting movements at respective points (360 m and 50 m) along two distance conditions (400 m and 80 m, respectively), were filmed by high-speed video camera. Running speeds at each point were computed from the film analysis. The running speed at 360 m point was defined as the speed under fatigue, while the running speed at the 50m point was defined as the maximal speed. Further, the rate between speed under fatigue and maximal speed was defined as %Max. Speed. Maximal O<SUB>2</SUB> intake, O<SUB>2</SUB> debt and isokinetic muscular endurance were measured.<BR>The results were summarized as follows :<BR>1) Oxygen debt showed significant correlation with the average speed during 400m running (r=0.546 ; p<0.05), but not with the speed under fatigue (r=0.388 ; p>0.05) .<BR>2) Speed under fatigue was positively correlated with muscular endurance of hip flexion and extension (r=0.683 ; p<0.01, r=0.572 ; p<0.05) .<BR>3) Percent Max. Speed was negatively correlated with the maximal speed (r = -0.643 ; p <0.01) and positively correlated with the muscular endurance of hip flexion and extension, and knee flexion (r=0.640 ; p <0.05, r=0.517 ; p<0.05, r=0.646 ; p<0.01) .<BR>These results suggest that; raising %Max. Speed to improve the muscular endurance of lower limbs and, to improve aerobic ability by developing the number of capillaries in the muscle, is important.