A bicycle ergometer for investigating the effect of eccentric exercise with arms and legs

Summary An induction clutch is combined with aKrogh's bicycle ergometer. In this way it is possible to transmit known work loads from an electromotor to theKrogh ergometer. The work load can be calibrated by the magnetic brake of theKrogh ergometer and when the direction of revolution is reversed it is possible for the subject to brake the ergometer by either the arms or the legs. It is concluded that the device may be useful in investigating the eccentric dynamic work with arms and legs.     

Reproducibility and validity of the quadriceps muscle integrated electromyogram threshold during incremental cycle ergometry

The principle aims of this research were, firstly, to determine if the relationship between integrated electromyography (iEMG) and exercise intensity was linear or threshold-like, and secondly, to determine if the relationship between iEMG and exercise intensity was repeatable on different test occasions. A group of 20 trained male subjects participated in the study. Each subject completed two incremental exercise tests on a Monark cycle ergometer. The tests were identical and separated from each other by a mean period of 42 (SD 12) h. The EMG signals were recorded from the vastus lateralis, rectus femoris and vastus medialis muscles at each intensity using surface electrodes. The relationship between iEMG and intensity was shown to be linear (r = 0.95 to r = 0.98) with no obvious iEMG thresholds present. The gradients of simple regression lines fitted to the iEMG compared to intensity were not significantly different on the retest occasion (CV 9%–12%). In summary, the findings of this study indicated that, during incremental exercise, the relationship between iEMG of the quadriceps musculature and exercise intensity was linear and not threshold-like. Furthermore, the linear relationship between iEMG and workload was repeatable on different test occasions.     

穴位埋线对专业运动员体能的影响

目的:观察穴位埋线对运动员运动能力的影响,探讨其可能的作用机制。方法:选择在专业训练中经常出现运动性疲劳、体能下降等相关症状的专业运动员,以关元、命门、肾俞、足三里、三阴交为主穴行穴位埋线。对16例国家赛艇女运动员进行6次治疗后测试2000m测功仪成绩,并于治疗前、治疗3次和6次后分别检测血睾酮、血红蛋白水平;将52例省重竞技队、省沙排队男运动员分成埋线组和推拿理疗组,治疗12周后观察两组运动员的中长跑成绩,并于治疗前、治疗12周、6个月和12个月后分别检测其血中睾酮和血红蛋白的含量。结果:①治疗后国家女子赛艇队2000m测功仪成绩明显提高(P<0.01),运动员血睾酮、血红蛋白水平较治疗前均明显提高(P<0.01,P<0.05);②省重竞技队、沙排队埋线组中长跑成绩提高值明显高于对照组(P<0.01),血睾酮和血红蛋白水平也均高于对照组(P<0.05)。结论:穴位埋线可以改善运动员运动性疲劳状况,提高运动员体能,从而提高运动成绩。其作用机制可能与提高血睾酮和血红蛋白水平有关。     

MR-compatible pedal ergometer for reproducible exercising of the human calf muscle

A pneumatic MR-compatible pedal ergometer was designed to perform dynamic contraction exercises of the human calf muscle in a whole-body 3 T MR scanner. The set-up includes sensors for monitoring mechanical parameters, such as pedal angle, cadence as well as applied force and power. Actual parameter values during the exercise were presented to the volunteer as a visual feedback to enable real-time self-adjustment of pedal deflection and cadence to the target reference value. Time-resolved dynamic ³¹P-MR spectroscopic measurements of phosphocreatine (PCr), inorganic phosphate (Pi) and pH were performed in a pilot experiment before, during, and after the exercise by a single volunteer. Two different load strengths were applied in these experiments (15% and 25% of the maximum voluntary contraction, MVC). As expected, mechanical and metabolic parameters differed for the two load levels. Small variations of the cadence, power and metabolic changes (time constants of PCr depletion and Pi accumulation) during the experiments demonstrate a highly reproducible mechanical output by the volunteer mediated by the ergometer.     

Cardiovascular effects in adolescents while they are playing video games: A potential health risk factor?

We analyzed heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), oxygen consumption, and carbon dioxide production in 17 male adolescents during a racing simulation video game (VG) and compared to resting state (RS) and exercise testing (ET) measures. We were able to demonstrate a significant (p<.005) increase from RS to VG concerning HR (+13.1 bpm), SBP (+20.8 mmHg), and DBP (+12.1 mmHg) with SBP and DBP elevations exceeding 2 SD in all children and 14/17 children, respectively. The energy consumption during VG (max 1.71 kcal/min) was unaltered compared to RS and significantly lower compared to ET even at the starting strain of 25 W (1.94 kcal/min). Hemodynamic parameters tested demonstrated lower HR, unchanged SBP, and higher DBP during the VG compared with ET. Comparing all measured parameters it can be said that the relation of blood pressure and energy consumption during VG might not be favorable.     

Ergometry for estimation of mechanical power output in sprinting in humans using a newly developed self-driven treadmill

An evaluation of mechanical power during walking and running in humans was undertaken after developing a specially designed running ergometer (RE) in which the subjects gripped the handlebar in front of them keeping both arms straight and in a horizontal position. Ten subjects participated in comparisons of the mean horizontal pushing force (MF _am) on the handlebar with the mean horizontal ground reaction force (MF _fp) recorded by force platform under the RE during five different constant speeds of walking or running and sprint running with maximal effort. Mechanical power developed during sprint running on the RE was compared with a 50 m sprint. Mean linear velocity (Mv) of the RE belt was recorded by the rotary encoder attached to the axis of the belt. Mean mechanical power calculated from the handlebar setting (MP _am=MF _am × Mv) was compared to that calculated from force platform recordings (MP _fp=MF _fp × Mv). A high test-retest reproducibility was observed for both MF _fp (r=0.889) and MF _am (r=0.783). Larger values for the coefficient of variation for MF _am (11.3%–15.8%) were observed than for MF _fp (3.3%–8.2%). The MP _am, which were obtained from five different constant speeds of walking, running and sprint running were closely correlated to those of MP _fp (y=0.98x − 19.10,r=0.982, P < 0.001). In sprint running, MP _am was 521.7 W (7.67 W · kg⁻¹) and was correlated to the 50 m sprint time (r=−0.683, P < 0.01). It is concluded that the newly developed RE was useful in the estimation of mechanical power output during human locomotion such as when walking, jogging and sprinting. Accepted: 10 October 2000     

Mechanical muscular power output and work during ergometer cycling at different work loads and speeds

Summary The aim of the study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling at different work loads and speeds. Six healthy subjects pedalled a weight-braked cycle ergometer at 0, 120 and 240 W at a constant speed of 60 rpm. The subjects also pedalled at 40, 60, 80 and 100 rpm against the same resistance, giving power outputs of 80, 120, 160 and 200 W respectively. The subjects were filmed with a cine-film camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work for the hip, knee and ankle joint muscles was calculated using a model based upon dynamic mechanics and described elsewhere. The total work during one pedal revolution significantly increased with increased work load but did not increase with increased pedalling rate at the same braking force. The relative proportions of total positive work at the hip, knee and ankle joints were also calculated. Hip and ankle extension work proportionally decreased with increased work load. Pedalling rate did not change the relative proportion of total work at the different joints.     

进驻海拔3680m青年通气无氧阈的初步观察

目的 :观察进驻海拔 3 680m青年的通气无氧阈 ;方法 :受试者坐于踏车功量机上 ,以 60rpm连续蹬车 ,每 3分钟递增 2 5W ,蹬车至力竭时停止 ,用O2 CO2 气体测定仪分析每个负荷最后半分钟的O2 和CO2 ,用心电图机同步记录心率 ,计算肺通气量 ( ·VE)、氧耗量 ( ·VO2 )、二氧化碳产生量 ( ·VCO2 )、呼吸商 (RQ)及氧通气当量 ( ·VE/ ( ·VO2 ) ;结果 :·VE、·VO2 、·VCO2 在功率达 75W时出现明显增加 ;RQ在功率达 75W时出现“拐折点” ;·VE/ ·VO2 在功率达 75W时由下降转向平稳 ;结论 :进驻海拔 3 680m青年通气无氧代谢阈为功率 75W。