Modeling of musculoskeletal structure and function using a modular bond graph approach     

Laura A. Wojcik 《Journal of The Franklin Institute》2003,340(1):63-76

The dynamic effects of muscle strength, timing of muscle activations, and body geometry have been modeled for a wide variety of human activities. These types of models require the development of complex system equations that account for the effects of rigid-body dynamics, musculotendon actuators, passive and active resistance to motion, and other physiological structures. One way in which model refinement can be expedited is through the use of bond graph modeling techniques. While bond graph techniques have been used extensively in a broad variety of applications, they have been used only sparingly in the field of biomechanics, despite the potential suitability of a modular, multidomain approach to the modeling of musculoskeletal function. In the current paper, bond graph modules representing muscle function and rigid-body motions of underlying bone structures are introduced. The system equations generated with the use of these models are equivalent to those developed with more traditional techniques, but the modules can be more easily used in conjunction with control models of neuromuscular function for the simulation of overall dynamic motor performance.  相似文献   

Dietary calcium and dairy intake and muscular fitness phenotypes in Australian children     

Costan G. Magnussen  Brooklyn J. Fraser  Kylie J. Smith 《Journal of sports sciences》2020,38(7):717-718

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Reduced fat oxidation during high intensity,submaximal exercise: is the availability of carnitine important?     

《European Journal of Sport Science》2013,13(2):191-199

Abstract

The increased energy demand that occurs with incremental exercise intensity is met by increases in the oxidation of both endogenous fat and carbohydrate stores up to an intensity of ~70% V˙O_2max in trained individuals. However, when exercise intensity increases beyond this workload, fat oxidation rates decline, both from a relative and absolute perspective. As endogenous glycogen use is accelerated, glycogen stores can become depleted, ultimately resulting in fatigue and the inability to maintain high intensity, submaximal exercise (>70% V˙O_2max). Despite a considerable accumulation of knowledge that has been gained over the past half century, the precise mechanism(s) regulating muscle fuel selection and underpinning the aforementioned decline in fat oxidation remain largely unclear. A greater understanding would undoubtedly lead to novel strategies to increase fat utilization and, as such, improve exercise capacity. The present review primarily addresses one of the most prominent theories to explain the phenomenon of diminished fat oxidation during high intensity, submaximal exercise; a reduced availability of muscle free carnitine for mitochondrial fat translocation. This is discussed in the light of recent work in this area taking advantage of the discovery that muscle carnitine content can be increased in vivo in humans. Furthermore, the evidence supporting the recently proposed theory that reduced muscle co-enzyme A availability to several key enzymes in the fat oxidation pathway may also exert a degree of control over muscle fuel selection during exercise is also considered. Strong correlational evidence exists that muscle free carnitine availability is likely to be a key limiting factor to fat oxidation during high intensity, submaximal exercise. However, it is concluded that further intervention studies manipulating the muscle carnitine pool in humans are required to establish a direct causal role. In addition, it is concluded that while a depletion of muscle coenzyme A availability during exercise also offers a viable mechanism for impairing fat oxidation, at present, this remains speculative.  相似文献   

Normal training response in skeletal muscle of post-infarction heart failure patients     

《European Journal of Sport Science》2013,13(2):231-239

Abstract

Congestive heart failure (CHF) patients experience reduced muscle fatigue resistance and exercise capacity. The aim of this study was to assess whether skeletal muscle in CHF patients has a normal training response compared to healthy subjects. We compared the effect of one-legged knee extensor (1-KE) endurance training in CHF patients (n=10), patients with coronary artery disease (CAD, n=9) and healthy subjects (n=13). The training response was evaluated by comparing trained leg and control leg after the training period. The fall in peak torque during 75 maximal 1-KE isokinetic contractions revealed that CHF patients were less fatigue resistant than healthy subjects in the control leg, but not in the trained leg. Peak power and peak oxygen uptake during dynamic 1-KE exercise was ~10–16% higher in trained leg than control leg. This training response was not significant different between groups. Muscle biopsies of vastus lateralis showed that fibre type composition was not different between trained leg and control leg. Capillary density was 6.5% higher in trained leg than control leg when all groups were pooled. In conclusion, the more fatigable skeletal muscle of CHF patients responds equally to endurance training compared to skeletal muscle of CAD patients and healthy subjects.  相似文献   

The sports performance application of vibration exercise for warm-up,flexibility and sprint speed     

《European Journal of Sport Science》2013,13(3):256-271

Abstract

Since the turn of the 21st century, there has been a resurgence of vibration technology to enhance sport science especially for power and force development. However, vibration exercise has been trialled in other areas that are central to athlete performance such as warm-up, flexibility and sprint speed. Therefore, the aim of this review was to attempt to gain a better understanding of how acute and short-term vibration exercise may impact on warm-up, flexibility and sprint speed. The importance of warming up for sporting performance has been well documented and vibration exercise has the capability to be included or used as a standalone warm-up modality to increase intramuscular temperature at a faster rate compared to other conventional warm-up modalities. However, vibration exercise does not provide any additional neurogenic benefits compared to conventional dynamic and passive warm-up interventions. Vibration exercise appears to be a safe modality that does not produce any adverse affects causing injury or harm and could be used during interval and substitution breaks, as it would incur a low metabolic cost and be time-efficient compared to conventional warm-up modalities. Acute or short-term vibration exercise can enhance flexibility and range of motion without having a detrimental effect on muscle power, however it is less clear which mechanisms may be responsible for this enhancement. It appears that vibration exercise is not capable of improving sprint speed performance; this could be due to the complex and dynamic nature of sprinting where the purported increase in muscle power from vibration exercise is probably lost on repeated actions of high force generation. Vibration exercise is a safe modality that produces no adverse side effects for injury or harm. It has the time-efficient capability of providing coaches, trainers, and exercise specialists with an alternative modality that can be implemented for warm-up and flexibility either in isolation or in conjunction with other conventional training methods.  相似文献   

Inspiratory muscle fatigue in swimmers after a single 200 m swim     

MICHELLE LOMAX  ALISON McCONNELL 《Journal of sports sciences》2013,31(8):659-664

Inspiratory muscle fatigue may occur in as little as 6 min during high-intensity spontaneously breathing exercise. The aims of this study were to determine whether inspiratory muscle fatigue occurs during swimming exercise and whether inspiratory muscle strength differs between the supine and standing body positions. Seven competitive swimmers were recruited to perform a single 200 m front-crawl swim, corresponding to 90-95% of race pace. Inspiratory muscle strength was measured at residual volume using a hand-held mouth pressure meter that measured maximal inspiratory pressure in the upright and supine positions. At baseline, maximal inspiratory pressure in the supine position was significantly lower than maximal inspiratory pressure in the upright position (112±20.4 and 133±16.7 cmH₂O, respectively; P?0.01). Post-exercise maximal inspiratory pressure in the supine position (80±15.7 cmH₂O) was significantly lower than baseline maximal inspiratory pressure in the supine position (P?0.01). The results indicate that a single 200 m front-crawl swim corresponding to 90-95% of race pace was sufficient to induce inspiratory muscle fatigue in less than 2.7 min. Furthermore, although diaphragm muscle length is optimized when supine, our results indicate that the force output of the diaphragm and inspiratory accessory muscles is greater when upright than when supine.  相似文献   

Effects of active,passive or no warm-up on metabolism and performance during high-intensity exercise     

Susan Gray  Myra Nimmo 《Journal of sports sciences》2013,31(9):693-700

The aim of this study was to determine the influence of type of warm-up on metabolism and performance during high-intensity exercise. Eight males performed 30 s of intense exercise at 120% of their maximal power output followed, 1 min later, by a performance cycle to exhaustion, again at 120% of maximal power output. Exercise was preceded by active, passive or no warm-up (control). Muscle temperature, immediately before exercise, was significantly elevated after active and passive warm-ups compared to the control condition (36.9 - 0.18°C, 36.8 - 0.18°C and 33.6 - 0.25°C respectively; mean - sx ) ( P ? 0.05). Total oxygen consumption during the 30 s exercise bout was significantly greater in the active and passive warm-up trials than in the control trial (1017 - 22, 943 - 53 and 838 - 45 ml O 2 respectively). Active warm-up resulted in a blunted blood lactate response during high-intensity exercise compared to the passive and control trials (change = 5.53 - 0.52, 8.09 - 0.57 and 7.90 - 0.38 mmol· l -1 respectively) ( P ? 0.05). There was no difference in exercise time to exhaustion between the active, passive and control trials (43.9 - 4.1, 48.3 - 2.7 and 46.9 - 6.2 s respectively) ( P = 0.69). These results indicate that, although the mechanism by which muscle temperature is elevated influences certain metabolic responses during subsequent high-intensity exercise, cycling performance is not significantly affected.  相似文献   

The effects of plyometric exercise on unilateral balance performance     

Craig Twist  Nigel Gleeson  Roger Eston 《Journal of sports sciences》2013,31(10):1073-1080

Abstract

The purpose of this study was to determine the effects of plyometric exercise on unilateral balance performance. Nine healthy adults performed baseline measurements on the dominant limb that consisted of: a 20-s unilateral stability test on a tilt balance board, where a higher stability index represented deterioration in balance performance; isokinetic plantar flexion torque at 0.52 and 3.14 rad · s^?1; muscle soreness in the calf region; and resting plantar flexion angle. Plyometric exercise consisted of 200 counter-movement jumps designed to elicit symptoms of muscle damage, after which baseline measurements were repeated at 30 min, 24, 48, and 72 h. Perceived muscle soreness of the calf region increased significantly following the plyometric exercise protocol (F_4,32 = 17.24, P < 0.01). Peak torque was significantly reduced after the plyometric exercise protocol (F_4,32 = 7.49, P < 0.05), with greater loss of force at the lower angular velocity (F_4,32 = 3.46, P < 0.05), while resting plantar flexion angle was not significantly altered compared with baseline values (P > 0.05). The stability index was significantly increased (F_4,32 = 3.10, P < 0.05) above baseline (mean 2.3, s = 0.3) at 24 h (3.3, s = 0.4), after which values recovered. These results indicate that there is a latent impairment of balance performance following a bout of plyometric exercise, which has implications for both the use of skill-based activities and for increased injury risk following high-intensity plyometric training.  相似文献   

减量训练通过不同亚型的PI3K对心肌的影响机制     

张军 《成都体育学院学报》2016,(5):107-112

目的：探讨在减量训练过程中，不同亚型的 PI3K 影响心肌的机制。方法：72只雄性 SD大鼠随机分为：3周安静对照组（C3）和3周大运动量训练组（E3）；3天对照组（C4）和3天减量训练组（E4）；6天对照组（C5）和6天减量训练组（E5）；2周对照组（C6）和2周减量训练组（ E6）。3周大运动量训练和2周的减量训练后取左心室肌组织，测定 PI3K p85、PI3K p110α和PI3K p110γ蛋白采用 Western blotting 方法。心肌组织形态学采用 HE 染色在光镜下观察。结果：3周大运动量训练和2周减量训练后，心肌组织形态没有显著变化，未发现心肌组织损伤。6天减量训练后，心肌 PI3K p110α蛋白表达显著增加（P ＜0.05）。2周减量训练后，心肌 PI3K p110α／ PI3K p85显著增加（P ＜0.05）。3周大运动量训练和减量训练后，心肌 PI3K p110γ蛋白表达没有显著变化（P ＞0.05）。结论：本研究制定的运动训练和减量训练方案未造成心肌损伤。减量训练通过不同亚型的PI3K影响心肌。  相似文献   

不同信号调节肌纤维类型转换的研究     

王海 《体育科技》2014,(5):74-75

通过文献综述法对不同信号调节肌纤维类型转换进行综述,结果表明：不同信号调节肌纤维类型转换作用机理是不同的;STIMI、FOXOI调节肌纤维类型转换,不具备导向性;而AIMPI、PGC-IQ促进II型向I型肌纤维转换,具有导向性;但肌纤维类型转换机制尚未阐释清楚还有待进一步进行研究。  相似文献