Gut Microbiome Fermentation Determines the Efficacy of Exercise for Diabetes Prevention

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人体单臂间歇运动对发汗调定点的影响

本工作系在微小气候相对恒定条件下,对10名健康男青年每人进行四项实验。实验 Ⅰ 为测定双侧腿足浸入43℃水中,诱发左前臂屈侧显现定量汗点时的口腔温度(舌下)阈值,作为发汗调定点参考值(ToSSP);实验 Ⅱ 为 Ⅰ 附加右臂间歇轻负荷运动(77W)时测定 ToSSP,部分对象还记录了皮肤电反应;实验 Ⅲ、Ⅳ 为 Ⅰ、Ⅱ 均附加4.5m/s 气流(22—25℃)直吹头面部,再分别测定 ToSSP。实验 Ⅰ 与 Ⅱ 同体对照22人次,Ⅲ 与 Ⅳ 同体对照24人次。结果表明,实验 Ⅱ、Ⅳ 的 ToSSP 均值及其潜伏期均值分别较 Ⅰ、Ⅲ 者降低(P<0.01)或缩短(P<0.001);Ⅰ、Ⅱ间的 ToSSP 均值差、潜伏期均值差,分别与 Ⅲ、Ⅳ 之间者无显著差异(P>0.2);Ⅱ、Ⅳ 的ToSSP 均值各与其实验开始前的口温均值亦无明显差异(P>0.5)。此结果支持运动时体温调定点下降的论点,并提示在研究体温调定点活动时,以 ToSSP 为指标较用发汗速率为优越,因 ToSSP 不为许多干扰因素所影响。     

Muscular sound and force relationship during isometric contraction in man

The contracting muscle generates a low frequency sound detectable at the belly surface, ranging from 11 to 40 Hz. To study the relationship between the muscular sound and the intensity of the contraction a sound myogram (SMG) was recorded by a contact sensor from the biceps brachii of seven young healthy males performing 4-s isometric contractions from 10% to 100% of the maximal voluntary contraction (MVC), in 10% steps. Simultaneously, the electromyogram (EMG) was recorded as an index of muscle activity. SMG and EMG were integrated by conventional methods (iSMG and iEMG). The relationship between iSMG and iEMG vs MVC% is described by parabolic functions up to 80% and 100% MVC respectively. Beyond 80% MVC the iSMG decreases, being about half of its maximal value at 100% MVC. Our results indicate that the motor unit recruitment and firing rate affect the iSMG and iEMG in the same way up to 80% MVC. From 80% to 100% MVC the high motor units' discharge rate and the muscular stiffness together limit the pressure waves generated by the dimensional changes of the active fibres. The muscular sound seems to reflect the intramuscular visco-elastic characteristics and the motor unit activation pattern of a contracting muscle.     

Comparison of incremental and steady state tests of endurance training

To compare the results obtained by incremental or constant work load exercises in the evaluation of endurance conditioning, a 20-week training programme was performed by 9 healthy human subjects on the bicycle ergometer for 1 h a day, 4 days a week, at 70-80% VO2max. Before and at the end of the training programme, (1) the blood lactate response to a progressive incremental exercise (18 W increments every 2nd min until exhaustion) was used to determine the aerobic and anaerobic thresholds (AeT and AnT respectively). On a different day, (2) blood lactate concentrations were measured during two sessions of constant work load exercises of 20 min duration corresponding to the relative intensities of AeT (1st session) and AnT (2nd session) levels obtained before training. A muscle biopsy was obtained from vastus lateralis at the end of these sessions to determine muscle lactate. AeT and AnT, when expressed as % VO2max, increased with training by 17% (p less than 0.01) and 9% (p less than 0.05) respectively. Constant workload exercise performed at AeT intensity was linked before training (60% VO2max) to a blood lactate steady state (4.8 +/- 1.4 mmol.l-1) whereas, after training, AeT intensity (73% VO2max) led to a blood lactate accumulation of up to 6.6 +/- 1.7 mmol.l-1 without significant modification of muscle lactate (7.6 +/- 3.1 and 8.2 +/- 2.8 mmol.kg-1 wet weight respectively). It is concluded that increase in AeT with training may reflect transient changes linked to lower early blood lactate accumulation during incremental exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

The acute effect of 30 min of moderate exercise on high density lipoprotein cholesterol in untrained middle-aged men

Fifteen middle-aged, untrained (defined as no regular exercise) men (mean age 49.9 years, range 42-67) cycled on a cycle ergometer at 50 rpm for 30 min at an intensity producing 60% predicted maximum heart rate [(fc,max), where fc,max = 220 - age]. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (Tg) concentrations were measured from fasting fingertip capillary blood samples collected at rest, after 15 and 30 min of exercise, and at 15 min post-exercise. The mean HDL-C level increased significantly from the resting level of 0.85 mmol.l-1 to 0.97 mmol.l-1 (P < 0.05) after 15 min of exercise, increased further to 1.08 mmol.l-1 (P < 0.01) after 30 min of exercise and remained elevated at 1.07 mmol.l-1 (P < 0.01) at 15 min post-exercise. These increases represented changes above the mean resting level of 14.1%, 27.1% and 25.9% respectively. The HDL-C/LDL-C ratio increased significantly from a resting ratio of 0.20 to 0.26 after 30 min of exercise (P < 0.01) and to 0.24 at 15 min post-exercise (P < 0.05). The mean Tg level increased significantly from a resting level of 0.88 mmol.l-1 to 1.05 mmol.l-1 after 15 min, and to 1.06 mmol.l-1 after 30 min of exercise (P < 0.05 at each time). The TC/HDL-C ratio decreased significantly (P = 0.05) after 30 min of exercise and at 15 min post-exercise by 18.8% and 14%, respectively. No significant changes were observed in the levels of TC or LDL-C over time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological effects of micropauses in isometric handgrip exercise

The physiological response to continuous and intermittent handgrip exercise was evaluated. Three experiments were performed until exhaustion at 25% of maximal voluntary contraction (MVC): experiment 1, continuous handgrip (CH) (n = 8); experiment 2, intermittent handgrip with 10-s rest pause every 3 min (IH) (n = 8); and experiment 3, as IH but with electrical stimulation (ES) of the forearm extensors in the pauses (IHES) (n = 4). Before, during, and after exercise, recordings were made of heart rate (HR), arterial blood pressure (BP), exercising forearm blood flow, and concentrations of potassium [K+] and lactate [La-] in venous blood from both arms. The electromyogram (EMG) of the exercising forearm extensors and perceived exertion were monitored during exercise. Before and up to 24 h after exercise, observations were made of MVC, of force response to electrical stimulation and of the EMG response to a 10-s test contraction (handgrip) at 25% of the initial MVC. Maximal endurance time (tlim) was significantly longer in IH (23.1 min) than in CH (16.2 min). The ES had no significant effect on tlim. During exercise, no significant differences were seen between CH and IH in blood flow, venous [K+] and [La-], or EMG response. The HR and BP increased at the same rate in CH and IH but, because of the longer duration of IH, the levels at exhaustion were higher in this protocol. The subjects reported less subjective fatigue in IH. During recovery, return to normal MVC was slower after CH (24 h) than after IH (4 h).(ABSTRACT TRUNCATED AT 250 WORDS)     

狗在运动中的肌糖原消耗与无氧阈的关系

本实验测定了5条狗的无氧阈值,运动耐受时间、衰竭时的血乳酸浓度及运动中的肌糖原消耗量。结果如下:无氧阈值,1.与运动耐受时间呈正相关(r=0.947,P<0.02);2.与运动中肌糖原消耗量呈负相关(r=-0.959,P<0.01);3.与衰竭时的血乳酸浓度呈负相关(r=-0.942,P<0.02)。实验结果提示,无氧阈值是反映机体耐力的可靠指标。而运动中肌糖原消耗少,血乳酸积累程度轻,可能是无氧阈值之所以能够反映机体耐力的物质基础。     

A mobile cage facilitates periodic social contact and exercise for singly caged adult Vervet monkeys

Abstract: A mobile exercise cage that expands the quantity and improves the quality of the space available to singly caged adult Vervet monkey males is described. It was easily fitted into an existing caging system and the addition of a resident consort female made it possible for the males to mate and have regular social contact.     

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 ± 0.22 1·min⁻¹ and 171.6 ± 19.2 beats·min⁻¹, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE.     

31P nuclear magnetic resonance study on changes in phosphocreatine and the intracellular pH in rat skeletal muscle during exercise at various inspired oxygen contents

We measured ATP, phosphocreatine (PCr), inorganic phosphate (P_i), and the intracellular pH in rat hindlimb muscles during submaximal isometric exercise with various O₂ deliveries using³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) to evaluate changes in energy metabolism in relation to O₂ availability. Delivery of O₂ to muscles was altered by controlling the fractional concentration of inspired oxygen (F _IO₂) at 0.50, 0.28, 0.21, 0.11 and 0.08 with monitoring partial pressure of oxygen and carbon dioxide, and bicarbonate at the femoral artery. The steady-state ratio of PCr : (PCr + P_i) during exercise decreased as a function ofF _IO₂ even at 0.21. Significant acidification of the intracellular pH during exercise occurred at 0.08F _IO₂. Change in the PCr : (PCr + P_i) ratio demonstrated that the oxidative capacity, i.e. the maximal rate of the oxidative phosphorylation reaction, in muscle was not limited by O₂ delivery at 0.50F _IO₂, but was significantly limited at 0.21F _IO₂ or below. Change in the intracellular pH at 0.08F _IO₂ could be interpreted as an increase in lactate, suggesting activation of glycolysis. Correlation between the PCr : (PCr + P_i) ratio and the intracellular pH revealed the existence of a critical PCr : (PCr + P_i) ratio and pH for glycolysis activation at around 0.4 and 6.7, respectively.