Is the high lactate release during arm exercise due to a low training status?

Summary To determine whether arm lactate release during arm exercise is related to the training status of the arms, seven arm-trained athletes were studied during 30 min of continuous arm exercise (AE) or leg exercise (LE) of increasing intensities corresponding to 30%, 50%, and 80% of peak VO₂ during AE and LE respectively. Blood vessels were catheterized for determination of regional blood flows and substrate exchanges. The respiratory exchange ratio was higher during AE than LE (P<0.01). The arteriovenous oxygen difference, [(A-V)O₂], for the leg during LE was 11–19% higher than the (A-V)O₂ for the arm during AE (P<0.01). At the highest intensity the (A-V)O₂ was 170±6 ml O₂1^-1 during LE, vs. 143 ± 9 during AE (P<0.01). Arm blood flow in relation to limb volume was 56–95% higher during AE (P<0.05). Arterial lactate concentrations were 27–60% higher during AE (P<0.01) and lactate release from the exercising limb was 2–4 times higher (P<0.05) during AE compared to LE. Adrenaline and noradrenaline rose 6- and 21-fold, respectively, during AE and did not differ from corresponding LE values. During AE the (A-V)O₂ difference across the arm, arterial lactate concentration, and arm lactate release were of the same magnitude in arm-trained and relatively less arm-trained subjects. Lactate release in relation to O₂ uptake by the exercising limb was 7–37% lower during AE in arm-trained subjects compared to AE in arm-untrained subjects but was 3–6 times higher than the corresponding relation during LE (P<0.01). We conclude that AE is associated with a larger lactate release compared to LE. This difference is only to a minor extent influenced by intense training of the arms. The high arm vs. leg lactate release appears to be associated with differences in regional circulatory adaptation by the exercising limb.     

Role of leg vasculature in the cardiovascular response to arm work in wheelchair-dependent populations

Summary. To assess the effects of leg vasculature on cardiovascular dynamics during submaximal arm work, oxygen uptake (V?o₂), cardiac output (Q?) and heart rate (HR) were measured during arm-crank ergometry (ACE) at 35 W (45% peak ACE V?o₂) in five able-bodied subjects, five wheelchair-dependent paraplegics, and five wheelchair-dependent bilateral amputees who represented the conditions of active, passive, and absence of leg musculature respectively. Arteriovenous oxygen difference (a—v? O₂) and stroke volume (SV) were calculated from V?o₂, Q? and HR. An index of leg fluid accumulation and leg blood flow was measured in the paraplegics and able-bodied subjects during rest and ACE. V?o₂, Q?, and a-v? O₂ during ACE were not statistically different among the three groups. However, paraplegics exhibited higher HR (P< 0.05) and lower SV (P < 0.06) during exercise compared to both amputees and able-bodied subjects. Greater (P < 0.05) leg fluid accumulation was measured in paraplegics compared to able-bodied subjects, although no statistically significant differences in leg blood flow were observed. Although our results are limited to a small number of subjects, these data suggest that an active muscle pump contributes significantly to elevated venous return and stroke volume during ACE. The legs of the paraplegic appear to act as a reservoir for fluid accumulation which may limit cardiac filling, particularly during moderate arm work to support wheelchair function.     

Metabolism in exercising arm vs. leg muscle

Summary. Arm and leg metabolism were compared by arterial and venous catheterization and blood flow measurements (by dye dilution techniques) in two groups of subjects performing 30-min continuous arm or leg exercise of increasing intensity corresponding to approximately 30, 50 and 80% of max oxygen uptake for arm or leg exercise. The absolute work-loads were 2·5-3 times higher during leg compared to arm exercise. Heart rates were the same in both types of exercise. r-Values were 0·97-1·07 during arm exercise. Arterial noradrenaline and adrenaline levels became higher during leg compared to arm exercise (P< 0·05401). Arterial lactate concentration was 50% higher for arm exercise at the two lower intensities (P< 0·001) and the same at the highest intensity compared to leg exercise. Arm lactate release was three times higher (P< 0·01) or the same as leg lactate output at corresponding exercise intensities. Arm and leg glucose uptake during exercise were of the same magnitude at the lower intensities. In contrast to the leg substrate exchange, arm lactate output was higher than the simultaneous glucose uptake (P< 0·05–0·001), indicating a relatively higher rate of glycogen degradation. In conclusion, exercising arm compared to leg muscles working at the same relative intensities utilize more carbohydrate, mainly muscle glycogen resulting in higher lactate release by the exercising extremity. This cannot solely be explained on the basis of differences in the degree of training and occurs with lower catecholamine levels compared to leg exercise.     

Increased insulin-stimulated glucose uptake by exercised human muscles one day after prolonged physical exercise

We evaluated whether the increased peripheral insulin sensitivity often reported after physical exercise is generalized or limited to the active musculature. Substrate exchange in leg (previously active) and forearm (previously inactive) were measured by catheterization technique basally and during a hyperinsulinaemic euglycaemic clamp (2 mU insulin kg-1 BW min-1) in nine healthy men before and 1 day after 3-h exercise (50% VO2max). One day after exercise basal glucose uptake was unchanged in the leg, while it was decreased in the forearm (-61%, P less than 0.01) compared with the pre-exercise condition. Glucose uptake during hyperinsulinaemia was increased in the leg (+31%, P less than 0.05), but not in the forearm. Basal lactate release by the leg was increased by the exercise, while lactate release by the forearm was decreased, significantly only during the clamp. These results indicate that local and not systemic factors are responsible for the changes in insulin sensitivity observed in the recovery from physical exercise.     

Reproducibility and sensitivity of muscle reoxygenation and oxygen uptake recovery kinetics following running exercise in the field

The purpose of this study was to assess the reliability of postexercise near‐infrared spectroscopy (NIRS)‐derived measurements and their sensitivity to different exercise intensities in the field. Seventeen athletes (24·1 ± 5·6 year) repeated, on three occasions, two 2‐min submaximal shuttle‐runs at 40% and 60% of V_IFT (final speed of the 30–15 intermittent fitness test) and a 50‐m shuttle‐run sprint (Sprint), with (OCC) or without (CON) repeated transient arterial occlusions of the medial gastrocnemius during the postexercise period. NIRS variables (i.e. oxyhaemoglobin [HbO₂], deoxyhaemoglobin [HHb] and their difference [Hb_diff]) were measured continuously for 3 min after each exercise. Half‐recovery (½Rec) and mean response (MRT; monoexponential curve fitting) times of muscle reoxygenation and muscle oxygen uptake () recovery were calculated. Reliability was assessed using the typical error of measurement, expressed as a coefficient of variation (CV). Postexercise recovery of muscle reoxygenation revealed CVs ranging from 16·8% to 37·3%; CV for recovery ranged from 6·2% to 20·9%, with no substantial differences shown between NIRS variables and exercise intensities. While running, intensity did not affect MRT or ½Rec for muscle reoxygenation, and differences were found for recovery (e.g. [Hb_diff]‐ MRT = 28·7 ± 5·2, 34·2 ± 5·1 and 37·3 ± 6·2 s for 40%, 60% and Sprint, respectively, P<0·01). To conclude, the kinetics of postexercise NIRS measurements showed CV values ranging from 6% to 37%, with no substantial differences between exercise intensities or NIRS‐derived variables. However, exercise intensity did influence recovery kinetics, but not that of muscle reoxygenation in an occlusion‐free condition.     

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise

The association between muscle oxygen uptake (VO₂) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one‐legged knee‐extension exercise at variable intensities using positron emission tomography and a‐v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI‐1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI‐2). Muscle perfusion and O₂ delivery during HI‐1 (26 ± 5 and 5·4 ± 1·0 ml 100 g^?1 min^?1) and HI‐2 (28 ± 4 and 5·8 ± 0·7 ml 100 g^?1 min^?1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g^?1 min^?1). Muscle VO₂ was also higher during both HI workloads (HI‐1 3·3 ± 0·4 and HI‐2 4·1 ± 0·6 ml 100 g^?1 min^?1) than LOW (1·4 ± 0·4 ml 100 g^?1 min^?1; P<0·01) and 25% higher during HI‐2 than HI‐1 (P<0·05). O₂ extraction was higher during HI workloads (HI‐1 62 ± 7 and HI‐2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O₂ extraction tended to be higher (P = 0·08) during HI‐2 when compared to HI‐1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one‐legged knee‐extension exercise at variable intensities, skeletal muscle perfusion and O₂ delivery are unchanged between high‐intensity workloads, whereas muscle VO₂ is increased during the second high‐intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O₂ delivery and uptake. We propose that the excess muscle VO₂ during the second high‐intensity workload is derived from working muscle cells.     

Influence of body position on the anginal threshold during leg exercise

Abstract. The circulatory adaptation to leg exercise in the supine and sitting positions with stepwise increased work loads was studied in twelve patients with signs of coronary heart disease. In four patients right heart catheterization was performed. Anginal pain appeared during exercise in both body positions in all patients, but at a lower work load and lower pulmonary oxygen uptake during supine exercise. Heart rate and systolic blood pressure were lower and the systolic ejection period was longer at the occurrence of angina during supine exercise. The calculated pressure-time per minute was significantly lower during exercise in the supine position. Catheterization data suggested a greater rise in left ventricular filling pressure with supine exercise. It is concluded that the differences in work tolerance for the two positions are partly due to a lower mechanical efficiency and may partly be secondary to the augmented venous return and increased left ventricular filling pressure observed during supine exercise. The augmented filling pressure will tend both to increase heart volume—and thereby augment myocardial oxygen requirements—and to compromise coronary perfusion and thus reduce myocardial oxygen supply during supine exercise.     

Atrial natriuretic factor during exercise in male endurance athletes: effect of training

Summary. Nine male endurance runners were evaluated with bicycle exercise testing before a training break of 3 weeks duration, and 0, 2 and 4 weeks after resumption of training to assess the effects of training on resting and exercise plasma atrial natriuretic factor (ANF) measured at 50% and 100% of predetermined maximal workload. Maximal oxygen uptake and lean body mass (LBM) were calculated at each time point. Maximal oxygen uptake decreased during training break, but rose 4 weeks after resumption of training (P<0·01). LBM was unchanged after inactivity, but rose after resumption of training (P<0·01). Plasma ANF at rest did not change throughout the experiment. ANF levels rose after training break at maximal workload (P<0·05), and decreased 4 weeks after resumption of training, but only at submaximal workload (P<0·05). No correlations between systolic blood pressure, mean blood pressure or heart rate and ANF could be demonstrated. These results indicate that the haemodynamic changes associated with endurance training are reflected in plasma ANF levels during exercise, but not at rest. The full adaptation of ANF release to training probably requires more time than the 4 weeks reported for the haemodynamic adjustments.     

Inosine causing insulin release and increased myocardial uptake of carbohydrates relative to free fatty acids in dogs

Summary. The aim of the present study was to determine the effect of i.v. inosine on myocardial substrate uptake and function in the in situ dog heart. Inosine was infused i.v. at a rate of 5 mg kg min^-1 in eight closed-chest pentobarbital anaesthetized dogs. Inosine caused a 46% decrease (P<0.01) in plasma free fatty acids (FFA), a 15% decrease (P<0.05) in plasma glycerol, an 18% decrease (P<0.05) in plasma glucose and a 46% increase (P<0.01) in blood lactate. This was associated with a 55% decrease (P<0.01) in myocardial FFA uptake and a 72% increase in lactate uptake, while glucose uptake remained unchanged. These metabolic changes were associated with a five-fold increase (P<0.05) in arterial insulin. Inosine caused an 18% increase (P<0.01) in myocardial blood flow without changing MVO₂. There was a 33% increase (P<0.01) in LV dP/dt_max, a decrease in LVEDP from 4.9 ± 0.9 (mean ± SEM) to 0.9 ± 0.3 mmHg (P<0.05) and a 24% decrease (P<0.01) in systemic vascular resistance. Inosine caused a transient 38% increase (P<0.05) in pulmonary vascular resistance. In conclusion, in addition to a positive inotropic effect and vascular effects inosine was found to cause release of insulin and to shift myocardial metabolism towards increased uptake of carbohydrates relative to FFA.     

Leg uptake of calcitonin gene‐related peptide during exercise in spinal cord injured humans

Exercise‐induced increases in cardiac output (CO) and oxygen uptake (VO₂) are tightly coupled, as also in absence of central motor activity and neural feedback from skeletal muscle. Neuromodulators of vascular tone and cardiac function – such as calcitonin gene related peptide (CGRP) – may be of importance. Spinal cord injured individuals (six tetraplegic and four paraplegic) performed electrically induced cycling (FES) with their paralyzed lower limbs for 29 ± 2 min to fatigue. Voluntary cycling performed both at VO₂ similar to FES and at maximal exercise in six healthy subjects served as control. In healthy subjects, CGRP in plasma increased only during maximal exercise (33·8 ± 3·1 pmol l^?1 (rest) to 39·5 ± 4·3 (14%, P<0·05)) with a mean extraction over the working leg of 10% (P<0·05). Spinal cord injured individuals had more pronounced increase in plasma CGRP (33·2 ± 3·8 to 46·9 ± 3·6 pmol l^?1, P<0·05), and paraplegic and tetraplegic individuals increased in average by 23% and 52%, respectively, with a 10% leg extraction in both groups (P<0·05). The exercise induced increase in leg blood flow was 10–12 fold in both spinal cord injured and controls at similar VO₂ (P<0·05), whereas CO increased more in the controls than in spinal man. Heart rate (HR) increased more in paraplegic subjects (67 ± 7 to 132 ± 15 bpm) compared with controls and tetraplegics (P<0·05). Mean arterial pressure (MAP) was unchanged during submaximal exercise and increased during maximal exercise in healthy subjects, but decreased during the last 15 min of exercise in the tetraplegics. It is concluded that plasma CGRP increases during exercise, and that it is taken up by contracting skeletal muscle. The study did not allow for a demonstration of the origin of the CGRP, but its release does not require activation of motor centres. Finally, the more marked increase in plasma CGRP and the decrease in blood pressure during exercise in tetraplegic humans may indicate a role of CGRP in regulation of vascular tone during exercise.     

生长抑素与奥曲肽治疗急性胰腺炎的临床疗效观察

目的探讨生长抑素与奥曲肽治疗急性胰腺炎（AP）的临床疗效。方法将67例AP患者随机分成两组,治疗组35例,其中13例重症胰腺炎（SAP）,给予生长抑素治疗。对照组32例,其中11例SAP,给予奥曲肽治疗。观察两组治疗效果及并发症。结果治疗组平均治愈天数为4．6d,转手术1例。对照组平均治愈天数为5．1d,转手术1例,胰源性肺损伤1例。治疗组与对照组疗效相近。结论生长抑素治疗AP与奥曲肽一样效果显著,使AP病程、住院时间缩短,并发症减少,转手术率、病死率降低。     

乌司他丁联合奥曲肽治疗急性重症胰腺炎的临床效果

目的探讨乌司他丁联合奥曲肽治疗急性重症胰腺炎的临床效果。方法选取我院2016年3月至2020年3月收治的96例急性重症胰腺炎患者作为研究对象,按照用药方式的不同将其分为观察组(乌司他丁联合奥曲肽)和对照组(乌司他丁联合生长抑素),各48例。比较两组的治疗效果。结果观察组的胃肠功能恢复时间、体温恢复时间、症状消失时间及住院时间均明显短于对照组(P<0.05)。治疗后,两组的血清AMS、UAMY水平及WBC均降低,且观察组低于对照组,差异具有统计学意义(P<0.05)。治疗后,两组的hs-CRP、IL-6、IL-2水平均降低,IgA、IgG、IgM水平均升高,且观察组优于对照组,差异具有统计学意义(P<0.05)。观察组的不良反应总发生率显著低于对照组(P<0.05)。结论乌司他丁联用奥曲肽能有效缩短急性重症胰腺炎患者的临床症状缓解时间,降低血清AMS和UAMY水平,改善免疫功能,且不良反应少,值得临床推广和应用。     

Experimental and clinical tests of the oxyconsumeter: A new oxygen uptake monitor

Summary The prototype of a microprocessor controlled oxygen uptake monitor oxyconsumeter developed by Draeger-werk AG, Luebeck, FRG, has been tested. The measuring accuracy of this device was assessed with laboratory bench experiments utilizing both the nitrogen dilution technique and the hydrogen combustion technique to simulate oxygen uptake ( O2). The correlation coefficient between the simulated and the measured O2 values was 0.9989 (p<0.05, n=115). The average relative error of the O2 values was –3.32%±3.88% when breathing 21 vol% oxygen and –5.58%±4.53% for 70 vol% oxygen (percent of reading). This was within the range given by the manufacturer (±5% for 21 vol% to <40 vol%, ±10% for 40 vol% to <70 vol%) with few exceptions. Furthermore the oxyconsumeter was used in clinical experiments to determine oxygen uptake during general anaesthesia. Oxygen uptake was monitored using a non-rebreathing system with an externally triggered expiratory valve. The difference between preanaesthetic reference values and values determined during anaesthesia averaged –24.8±20.1 ml/min/m2 oxygen. This average relative change of –16.0±11.5% was statistically significant in 11 of 15 cases (p<0.05).     

吸氧流量及湿化液量与吸氧噪音的关系

目的探讨吸氧时吸氧流量及湿化瓶内湿化液量与吸氧噪音的关系。方法将两套吸氧装置的湿化瓶分别加入1/3、1/2的蒸馏水作为湿化液,分别记录两套吸氧装置在流量为2 L/min、5 L/min时产生的噪音值。结果相同容量湿化液下不同吸氧流量产生的噪音值比较,差异具有统计学意义（均P＜0.01）,具有氧气流量越大噪音越大的趋势;相同吸氧流量下不同容量湿化液吸氧产生的噪音值比较,差异有统计学意义（均P＜0.01）,具有湿化液越多噪音越大的趋势。结论吸氧产生的噪音随着吸氧流量的增大和湿化液的增多而增大,建议在给患者吸氧时湿化瓶内加入蒸馏水的量在1/3和1/2的标记中间或再偏小些。     

A call to action towards an evidence‐based approach to using verbal encouragement during maximal exercise testing

By definition, maximal exercise testing inherently requires participants to give a maximal effort. This is an important practical issue as submaximal efforts can produce invalid test results. Verbal encouragement is commonly used to motivate participants to maintain or increase effort investment during maximal exercise testing. Accordingly, studies have reported significant increases in time to exhaustion of between 8% and 18% during VO_2max and multistage shuttle run tests, and a significant 30·5 m mean increase in 6‐min walk test distance. Significant improvements during shorter tests, such as the Wingate and 2‐min walk tests, have not been observed however. Although participants typically perceive verbal encouragement positively during maximal exercise testing, around one‐third have neutral or negative perceptions. Despite the ubiquity and importance of verbal encouragement during maximal exercise testing, surprisingly little research has investigated the characteristics of effective encouragement with respect to its content, timing and frequency. The only randomized controlled trial to investigate one of these issues observed that verbal encouragement delivered every 20 s increased time to exhaustion during VO_{2 max} testing, but not every 60 or 180 s. Of particular concern is that several exercise testing guidelines have incorporated specific guidelines for the use of verbal encouragement, but not provided any theoretical or empirical justification, presumably because of the limited research to inform practice. Recent empirical research does provide some important insight into participant preference for the content and timing of verbal encouragement during maximal exercise testing; however, much more research is clearly required to establish comprehensive evidence‐based guidelines.     

Exaggerated blood pressure response to exercise: importance of resting blood pressure

Normotensive individuals who exhibit an exaggerated blood pressure (BP) response to exercise have an increased risk of future hypertension. However, previous studies failed to control for resting BP despite the fact that an elevated resting BP in the normotensive range is also a strong predictor of future hypertension. Therefore, we determined whether maximal systolic BP is associated with resting BP. Resting BP was measured in 68 healthy normotensive men on three separate days. The subjects then performed a graded, maximal exercise test on a Monark cycle ergometer. Maximal systolic BP was strongly correlated with resting systolic BP (r = 0·64, P<0·0001). Subjects with elevations in systolic BP during maximal exercise (>220 mmHg) also had higher (P<0·005) resting BP than those without (<220 mmHg). When stepwise regression analyses were performed, systolic BP at rest was a significant independent predictor of maximal systolic BP, explaining over 40% of the variability. These results suggest that exaggerated BP response as a predictor of future hypertension reported in previous studies may be little more than a simple reflection of elevated resting BP. Specifically, these studies should not be interpreted as demonstrating that exercise BP is a better predictor of future hypertension than resting BP alone. In the future, defining the BP `response' to exercise as a change score (i.e. maximal BP minus resting BP) may be advantageous as it permits the effects of exercise to be examined independently of the level of resting BP.     

A study to evaluate the feasibility of an aerobic exercise program in patients with migraine

Objectives.— The aim of this study was to develop and evaluate an exercise program to improve maximum oxygen uptake (VO_{2 max}) in untrained patients with migraine without making their migraines worse.
Patients and methods.— Twenty-six patients were studied at a headache clinic in Sweden. The exercise program, based on indoor cycling, was performed 3 times per week during 12 weeks. VO_{2 max}, migraine status, side effects, and quality of life were evaluated.
Results.— VO_{2 max} increased from 32.9 mL/kg/minute to 36.2 mL/kg/minute ( P  = .044). Quality of life increased and significant improvements in migraine status (attack frequency, symptom intensity, and intake of medicine) were seen. During the 12 weeks of exercise, on one occasion one patient had a migraine attack, which started immediately after training. No other side effects were reported.
Conclusions.— The evaluated exercise program was well tolerated by the patients and improved their VO_{2 max} with no deterioration of migraine status.     

Validation of the acetylene rebreathing method for measurement of cardiac output at rest and during high-intensity exercise

The use of the acetylene rebreathing method to estimate cardiac output (CO) during high-intensity exercise, which may be influenced by recirculation of acetylene, has not been validated. This study was designed to validate the acetylene rebreathing method to measure CO during high-intensity exercise using the direct Fick method. CO was measured at rest and during exercise at 25%, 50%, 75% and 90% of the nine subjects maximum oxygen uptake (VO _2max) by the direct Fick and acetylene rebreathing method. CO measured by the acetylene rebreathing method correlated with work rate (r=0·90, P<0·01) and with oxygen uptake (r=0·94, P<0·01). The correlation coefficient of CO between both methods was r=0·91 (P<0·01). There was no significant difference in CO measured by each method at rest as well as at each work rate. The difference in CO between each method was greater at lower CO than at higher CO. At 90% of VO _2max, the CO measured by acetylene rebreathing was nearly identical to that measured by the Fick method. It can be concluded that acetylene rebreathing for measurement of CO is valid not only at rest but also during exercise, especially during high-intensity exercise.