Mechanical energetic processes during the giant swing before the Tkatchev exercise

The goal of this study was to examine the possibility of the utilization of high bar and uneven parallel bar elasticity by the gymnasts through muscular work during the giant swing before the Tkatchev exercise on the high bar or uneven parallel bars. The performances were gathered during the Gymnastic World Championship in 1994. The set up consisted of two video cameras (50Hz) and two force measuring bars (500Hz). Twenty giant swings before the Tkatchev exercise, nine giant swings before the Tkatchev exercise after Tkatchev on the high bar and 15 giant swings before the Tkatchev exercise on the uneven parallel bars were analyzed. The giant swings were performed by 20 male and 15 female gymnasts. There are three phases during the giant swing exercise before the Tkatchev in which the systems (high bar-human body) total energy can be changed. During the first phase, energy is transferred from the gymnast's body into the bar. A clearly effective use of the bar's elasticity during the first phase could not be found. During the second phase, energy is transferred from the bar's back into the gymnast's body whose total energy increases. An increase in the energy of the system can only be achieved through muscular work. During the second phase of the various giant swing techniques no significant (p<0.05) difference in the energy increase through muscular work could be found. During the third phase, energy is once again produced by the gymnast through extension at the hip and shoulder joints.     

A mathematical high bar–human body model for analysing and interpreting mechanical-energetic processes on the high bar

The aims of this study were:

1. To study the transfer of energy between the high bar and the gymnast.

2. To develop criteria from the utilisation of high bar elasticity and the utilisation of muscle capacity to assess the effectiveness of a movement solution.

3. To study the influence of varying segment movement upon release parameters.

For these purposes a model of the human body attached to the high bar (high bar–human body model) was developed. The human body was modelled using a 15-segment body system. The joint-beam element method (superelement) was employed for modelling the high bar. A superelement consists of four rigid segments connected by joints (two Cardan joints and one rotational–translational joint) and springs (seven rotation springs and one tension–compression spring). The high bar was modelled using three superelements. The input data required for the high bar–human body model were collected with video-kinematographic (50 Hz) and dynamometric (500 Hz) techniques. Masses and moments of inertia of the 15 segments were calculated using the data from the Zatsiorsky et al. (1984) model. There are two major phases characteristic of the giant swing prior to dismounts from the high bar. In the first phase the gymnast attempts to supply energy to the high bar–human body system through muscle activity and to store this energy in the high bar. The difference between the energy transferred to the high bar and the reduction in the total energy of the body could be adopted as a criterion for the utilisation of high bar elasticity. The energy previously transferred into the high bar is returned to the body during the second phase. An advantageous increase in total body energy at the end of the exercise could only be obtained through muscle energy supply. An index characterising the utilisation of muscle capacity was developed out of the difference between the increase in total body energy and the energy returned from the high bar. A delayed and initially slow but even reduction of hip and shoulder angles provided more advantageous release conditions. The total body energy could be improved by up to 15%, the vertical CM release velocity by up to 10% and the angular momentum by up to 35%.     

Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance.

We investigated the effect of carbohydrate (CHO) ingestion before and during exercise and in combination on glucose kinetics, metabolism and performance in seven trained men, who cycled for 120 min (SS) at approximately 63% of peak power output, followed by a 7 kJ/kg body wt time trial (TT). On four separate occasions, subjects received either a placebo beverage before and during SS (PP); placebo 30 min before and 2 g/kg body wt of CHO in a 6.4% CHO solution throughout SS (PC); 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and placebo throughout SS (CP); or 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and 2 g/kg of CHO in a 6.4% CHO solution throughout SS (CC). Ingestion of CC and CP markedly (>8 mM) increased plasma glucose concentration ([glucose]) compared with PP and PC (5 mM). However, plasma [glucose] fell rapidly at the onset of SS so that after 80 min it was similar (6 mM) between all treatments. After this time, plasma [glucose] declined in both PP and CP (P < 0.05) but was well maintained in both CC and PC. Ingestion of CC and CP increased rates of glucose appearance (R(a)) and disappearance (R(d)) compared with PP and PC at the onset of, and early during, SS (P < 0.05). However, late in SS, both glucose R(a) and R(d) were higher in CC and PC compared with other trials (P < 0.05). Although calculated rates of glucose oxidation were different when comparing the four trials (P < 0.05), total CHO oxidation and total fat oxidation were similar. Despite this, TT was improved in CC and PC compared with PP (P < 0.05). We conclude that 1) preexercise ingestion of CHO improves performance only when CHO ingestion is maintained throughout exercise, and 2) ingestion of CHO during 120 min of cycling improves subsequent TT performance.     

Effect of flywheel-based resistance exercise on processes contributing to muscle atrophy during unloading in adult rats.

Flywheel-based resistance exercise (RE) attenuates muscle atrophy during hindlimb suspension. We have previously shown that protein synthesis is elevated in response to RE, but the effect on protein degradation, cell proliferation, or apoptosis was not investigated. We hypothesized that, in addition to affecting protein synthesis, RE inhibits processes that actively contribute to muscle atrophy during hindlimb suspension. Male rats were housed in regular cages (control), tail suspended for 2 wk (HS), or HS with RE every other day for 2 wk (HSRE). Although RE attenuated soleus muscle atrophy during HS, the observed fivefold elevation in apoptosis and the 53% decrease in cell proliferation observed with HS were unaffected by RE. Expression of genes encoding components of the ubiquitin-proteasome pathway of protein degradation were elevated with HS, including ubiquitin, MAFbx, Murf-1, Nedd4, and XIAP, and proteasome subunits C2 and C9. Total ubiquitinated protein was increased with HS, but proteasome activity was not different from control. RE selectively altered the expression of different components of this pathway: MAFbx, Murf-1, and ubiquitin mRNA abundance were downregulated, whereas C2 and C9 subunits remained elevated. Similarly, Nedd4 and XIAP continued to be upregulated, potentially accounting for the observed augmentation in total ubiquitinated protein with RE. Thus a different constellation of proteins is likely ubiquitinated with RE due to altered ubiquitin ligase composition. In summary, the flywheel-based resistance exercise paradigm used in this study is associated with the inhibition of some mechanisms associated with muscle atrophy, such as the increase in MAFbx and Murf-1, but not with others, such as proteasome subunit remodeling, apoptosis, and decreased proliferation, potentially accounting for the inability to completely restore muscle mass. Identifying specific exercise parameters that affect these latter processes may be useful in designing effective exercise strategies in the elderly or during spaceflight.     

The effects of diet on muscle pH and metabolism during high intensity exercise

Five healthy male subjects exercised for 3 min at a workload equivalent to 100% VO2max on two separate occasions. Each exercise test was performed on an electrically braked cycle ergometer after a four-day period of dietary manipulation. During each of these periods subjects consumed either a low carbohydrate (3 +/- 0%, mean +/- SD), high fat (73 +/- 2%), high protein (24 +/- 3%) diet (FP) or a high carbohydrate (82 +/- 1%), low fat (8 +/- 1%) low protein (10 +/- 1%) diet (CHO). The diets were isoenergetic and were assigned in a randomised manner. Muscle biopsy samples (Vastus lateralis) were taken at rest prior to dietary manipulation, immediately prior to exercise and immediately post-exercise for measurement of pH, glycogen, glucose 6-phosphate, fructose 1,6-diphosphate, triose phosphates, lactate and glutamine content. Blood acid-base status and selected metabolites were measured in arterialised venous samples at rest prior to dietary manipulation, immediately prior to exercise and at pre-determined intervals during the post-exercise period. There was no differences between the two treatments in blood acid-base status at rest prior to dietary manipulation; immediately prior to exercise plasma pH (p less than 0.01), blood PCO2 (p less than 0.01), plasma bicarbonate (p less than 0.001) and blood base-excess (p less than 0.001) values were all lower on the FP treatment. There were no major differences in blood acid-base variables between the two diets during the post-exercise period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma catecholamine and parathyroid hormone responses in cattle during treadmill exercise at simulated high altitude.

When steers were exposed to treadmill exercise at a simulated altitude of 3500 m, plasma concentrations of epinephrine and norepinephrine as well as of parathyroid hormone increased within minutes. Heart rate, erythrocyte number and plasma lactic acid level rose at the same time, whereas plasma free fatty acids showed a later increase. It is concluded, that the elevated parathyroid hormone levels were probably caused by sympathetic stimulation.     

Lipid economy,flight activity and reproductive behaviour in the speckled wood butterfly: on the energetic cost of territory holding

Insect flight is a highly energy demanding type of locomotion. In butterflies, males may locate females by different behavioural tactics. The tactics correspond to different flight types that, in turn, are assumed to reflect different energetic costs. Costs need to be considered to fully understand the pay‐offs of co‐existing alternative tactics relative to the environmental context and the phenotypes of the individuals. We addressed the issue in the speckled wood Pararge aegeria, in which males either adopt a territorial wait‐and‐fight tactic (i.e. territorial perching) in a sunlit patch on the forest floor, or a fly‐and‐search tactic to locate females in a wider area of the forest (i.e. patrolling). Perching corresponds to high frequency of take‐off flights and aerial combats with high levels of manoeuvrability and is assumed to be energetically more costly than longer, continuous flights at lower speed in patrollers. We tested the effect of different flight activity levels and of the behavioural tactics on lipid reserves and lipid use in males by laboratory and outdoor cage experiments. Low‐activity males that had access to honey water were capable of synthesizing lipids; their lipid reserves increased with age. The effect disappeared in males that actively flew in the outdoor cages. Lipid reserves decreased significantly faster in territorial perching males compared to non‐perching males, but resting metabolic rate did not differ between the alternative behavioural tactics. Territorial perching males had larger flight muscle ratio (i.e. thorax/body mass) than non‐perching males. We discuss the evidence of the physiological costs of perching relative to the co‐existence of perching and patrolling tactics.     

Ventilation-perfusion inequality during normoxic and hypoxic exercise in the emu.

Many avian species exhibit an extraordinary ability to exercise under hypoxic condition compared with mammals, and more efficient pulmonary O(2) transport has been hypothesized to contribute to this avian advantage. We studied six emus (Dromaius novaehollandaie, 4-6 mo old, 25-40 kg) at rest and during treadmill exercise in normoxia and hypoxia (inspired O(2) fraction approximately 0.13). The multiple inert gas elimination technique was used to measure ventilation-perfusion (V/Q) distribution of the lung and calculate cardiac output and parabronchial ventilation. In both normoxia and hypoxia, exercise increased arterial Po(2) and decreased arterial Pco(2), reflecting hyperventilation, whereas pH remained unchanged. The V/Q distribution was unimodal, with a log standard deviation of perfusion distribution = 0.60 +/- 0.06 at rest; this did not change significantly with either exercise or hypoxia. Intrapulmonary shunt was <1% of the cardiac output in all conditions. CO(2) elimination was enhanced by hypoxia and exercise, but O(2) exchange was not affected by exercise in normoxia or hypoxia. The stability of V/Q matching under conditions of hypoxia and exercise may be advantageous for birds flying at altitude.     

Influence of breathing pattern on oxygen exchange during hypoxia and exercise.

During hypoxia, arterial oxygen saturation (SaO2) measured by ear oximeter shows cyclic fluctuations which are related to the pattern and rate of breathing. Continuous recordings of SaO2 may be corrected for distortion, due to circulatory transport, to yield approximate values for pulmonary end-capillary saturation (Sc'O2). This permits calculation of the corresponding end-capillary PO2 (Pc'O2). We have used this technique to study the effect of spontaneous and imposed breathing patterns on mean Pc'O2, amplitude of Pc'O2 (delta Pc'O2) and minute ventilation (VE). The studies were conducted during mild hypoxia, at rest and exercise. The amplitude of delta Pc'O2 is inversely related to breathing frequency. When frequency is constant, patterns with with prolonged expiration or end-expiratory pauses produce large delta Pc'O2 and greater VE. This effect is reversed with prolonged inspiration or end-inspiratory pauses. Spontaneous breathing patterns produced smaller delta Pc'O2, with lower VE than imposed patterns. These findings are compatible with animal studies which suggest the magnitude of PaO2 fluctuations produced by the breathing pattern may act as a feedback stimulus to ventilation. The breathing patterns, which are spontaneously chosen, produce the minimum delta Pc'O2 and VE.     

Influence of expiratory loading and hyperinflation on cardiac output during exercise.

Patients with obstructive lung disease are exposed to expiratory loads (ELs) and dynamic hyperinflation as a consequence of expiratory flow limitation. To understand how these alterations in lung mechanics might affect cardiac function, we examined the influence of a 10-cm H2O EL, alone and in combination with voluntary hyperinflation (ELH), on pulmonary pressures [esophageal (Pes) and gastric (Pg)] and cardiac output (CO) in seven healthy subjects. CO was determined by using an acetylene method at rest and at 40 and 70% of peak work. At rest and during exercise, EL resulted in an increase in Pes and Pg (7-18 cm H2O; P < 0.05) and a decrease in CO (from 5.3 +/- 1.8 to 4.5 +/- 1.4, 12.2 +/- 2.2 to 11.2 +/- 2.2, and 16.3 +/- 3.3 to 15.2 +/- 3.2 l/min for rest, 40% peak work, and 70% peak work, respectively; P < 0.05), which remained depressed after an additional 2 min of EL. With ELH, CO increased at rest and both exercise loads (relative to EL only) but remained below control values. The changes in CO were due to a reduction in stroke volume with a tendency for stroke volume to fall further with prolonged EL. There was a negative correlation between CO and the increase in expiratory Pes and Pg with EL (R = -0.58 and -0.60; P < 0.01), whereas the rise in CO with subsequent hyperinflation was related to a more negative Pes (R = 0.72; P < 0.01). In conclusion, EL leads to a reduction in CO, which appears to be primarily related to increases in expiratory abdominal and intrathoracic pressure, whereas ELH resulted in an improved CO, suggesting that lung inflation has little impact on cardiac function.     

Contributions of the individual ankle plantar flexors to support, forward progression and swing initiation during walking.

Walking is a motor task requiring coordination of many muscles. Previous biomechanical studies, based primarily on analyses of the net ankle moment during stance, have concluded different functional roles for the plantar flexors. We hypothesize that some of the disparities in interpretation arise because of the effects of the uniarticular and biarticular muscles that comprise the plantar flexor group have not been separated. Furthermore, we believe that an accurate determination of muscle function requires quantification of the contributions of individual plantar flexor muscles to the energetics of individual body segments. In this study, we examined the individual contributions of the ankle plantar flexors (gastrocnemius (GAS); soleus (SOL)) to the body segment energetics using a musculoskeletal model and optimization framework to generate a forward dynamics simulation of normal walking at 1.5 m/s. At any instant in the gait cycle, the contribution of a muscle to support and forward progression was defined by its contribution to trunk vertical and horizontal acceleration, respectively, and its contribution to swing initiation by the mechanical energy it delivers to the leg in pre-swing (i.e., double-leg stance prior to toe-off). GAS and SOL were both found to provide trunk support during single-leg stance and pre-swing. In early single-leg stance, undergoing eccentric and isometric activity, they accelerate the trunk vertically but decelerate forward trunk progression. In mid single-leg stance, while isometric, GAS delivers energy to the leg while SOL decelerates it, and SOL delivers energy to the trunk while GAS decelerates it. In late single-leg stance through pre-swing, though GAS and SOL both undergo concentric activity and accelerate the trunk forward while decelerating the downward motion of the trunk (i.e., providing forward progression and support), they execute different energetic functions. The energy produced from SOL accelerates the trunk forward, whereas GAS delivers almost all its energy to accelerate the leg to initiate swing. Although GAS and SOL maintain or accelerate forward motion in mid single-leg stance through pre-swing, other muscles acting at the beginning of stance contribute comparably to forward progression. In summary, throughout single-leg stance both SOL and GAS provide vertical support, in mid single-leg stance SOL and GAS have opposite energetic effects on the leg and trunk to ensure support and forward progression of both the leg and trunk, and in pre-swing only GAS contributes to swing initiation.     

Influence of exercise on dilatation of the basilar artery during diabetes mellitus.

Our goal was to examine whether exercise training alleviates impaired nitric oxide synthase (NOS)-dependent dilatation of the basilar artery in Type 1 diabetic rats. To test this hypothesis, we measured in vivo diameter of the basilar artery in sedentary and exercised nondiabetic and diabetic rats in response to NOS-dependent (acetylcholine) and -independent (nitroglycerin) agonists. To determine the potential role for nitric oxide in vasodilatation in sedentary and exercised nondiabetic and diabetic rats, we examined responses after NG-monomethyl-l-arginine (l-NMMA). We found that acetylcholine produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic rats. Acetylcholine produced only minimal vasodilatation in sedentary diabetic rats. However, exercise alleviated impaired acetylcholine-induced vasodilatation in diabetic rats. Nitroglycerin produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic and diabetic rats. l-NMMA produced similar inhibition of acetylcholine-induced dilatation of the basilar artery in sedentary and exercised nondiabetic and diabetic rats. Finally, we found that endothelial NOS (eNOS) protein in the basilar artery was higher in diabetic compared with nondiabetic rats and that exercise increased eNOS protein in the basilar artery of nondiabetic and diabetic rats. We conclude that 1) exercise can alleviate impaired NOS-dependent dilatation of the basilar artery during diabetes mellitus, 2) the synthesis and release of nitric oxide accounts for dilatation of the basilar artery to acetylcholine in sedentary and exercised nondiabetic and diabetic rats, and 3) exercise may exert its affect on cerebrovascular reactivity during diabetes by altering levels of eNOS protein in the basilar artery.     

Changes in the leucocyte count during and after brief intense exercise.

Twelve healthy male volunteers exercised at 200 W on a cycle ergometer for 8 min or until exhausted, if sooner. Retrospectively, subjects fell into two groups. During the last minute of exercise at 200 W, those in group 1 (n = 5) had a mean respiratory exchange ratio (R) of 1.06 (SD 0.01) and were working at a mean of 79% (SD 4%) of their maximum oxygen consumption (VO2max) as measured in a separate incremental load test. For subjects in group 2 (n = 7), R was 1.31 (SD 0.08) and their VO2 was maximal (mean 101%. SD 3%). Plasma lactate, and adrenaline concentrations rose to higher levels during exercise in subjects in group 2 than in those in group 1. At the finish of exercise, the leucocyte count and the plasma lactate concentration immediately began to fall in subjects in group 1 whereas in group 2 subjects both rose for several minutes before falling. Plasma catecholamine concentrations fell rapidly in both groups during recovery.     

Effects of high-cholesterol diet and parallel exercise training on the vascular function of rabbit aortas: a time course study.

It is plausible to assume that exercise training, when applied early enough, can completely correct atherosclerotic defects. Using rabbit aortic specimens, we examined the effects of chronic exercise and high-cholesterol diet feeding on vascular function for different time periods. Male New Zealand White rabbits were divided into four groups: the normal diet groups with or without exercise training and the high-cholesterol diet groups with or without exercise training. Animals in high-cholesterol diet groups were fed 2% cholesterol rabbit chow for 2, 4, or 6 wk. Those in exercise training groups ran on a treadmill at 0.88 km/h for up to 40 min/day, 5 days/wk for the same period of time as the diet feeding. Thoracic aortas were isolated for functional and immunohistochemical analyses. We found that 1). although high-cholesterol diet feeding (>or=2 wk) elevated serum cholesterol levels and impaired acetylcholine-evoked vasorelaxation, only the latter effect was reversed by exercise training; 2). the effects of diet and exercise on acetylcholine-evoked vasorelaxation were mainly due to altered release of nitric oxide and endothelium-derived hyperpolarizing factor; and 3). diet feeding for 4 or 6 wk caused significant lipid deposition and expression of P-selectin, VCAM-1, monocyte chemoattractant protein-1, and inducible nitric oxide synthase, which were largely reduced by exercise training. In conclusion, parallel exercise training almost completely reverses the early-stage endothelial dysfunction caused by high-cholesterol diet feeding.     

飞行对粘虫体内甘油酯积累与咽侧体活性的影响

研究了粘虫Mythimna separata (Walker)成虫飞行对甘油酯的恢复、保幼激素的滴度及飞行肌降解的影响, 结果表明,不同日龄粘虫的飞行活动对其能源物质的积累及保幼激素分泌产生不同的影响。1日龄蛾的飞行对粘虫这两方面产生的影响最大,其飞行个体能源物质的积累明显高于未飞行的对照个体; 3日龄飞行个体的能源物质积累与对照相当; 但5日龄飞行个体则很难达到对照水平。1日龄飞行个体咽侧体活性在36 h后明显高于对照,60 h后已是对照的10倍,108 h达到其峰值; 3日龄飞行个体咽侧体的活性稍高于对照,但差别不显著; 5日龄飞行个体的咽侧体活性则稍低于对照。不同日龄飞行对飞行肌的降解也产生不同的影响。1日龄飞行个体的飞行肌在飞行后6 天已经明显低于对照。3、5日龄的飞行活动对其飞行肌降解的影响不明显。因此推测,粘虫咽侧体活化的关键时期可能在羽化后1～3 天之间。