The incidence of plateau at VO(2max) is affected by a bout of prior-priming exercise

The purpose of this study was to determine the effect of 6 min of prior-priming exercise on the incidence of plateau at VO(2max). Twelve trained cyclists (age, 21 ± 3 years; height, 175·0 ± 8·0 cm; weight, 69·0 ± 10·4 kg; maximal oxygen uptake (VO(2max)), 56·3 ± 6·9 ml kg(-1) min(-1)) completed three incremental tests to volitional exhaustion, which were classified as unprimed (UP), heavy-primed (HP) and severe-primed (SP), at a work rate of 1 W 2 s(-1), from an initial workload of 100 W, for the determination of VO(2max). VO(2max) trial in the HP and SP conditions was preceded by a period of 4-min unloaded cycling followed by a further 6 min of constant load cycling at Δ50% VO(2) gas exchange threshold (GET)-VO(2max) (HP) and Δ75% VO(2) GET-VO(2max) (SP). Expired air was recorded on a breath-by-breath basis during all trials. The criteria adopted for a plateau in VO(2max) was a ΔVO(2) over the final two consecutive 30-s sampling periods ≤ 2·1 ml kg(-1) min(-1). There was a significant increase in plateau responses between the UP (50%) and HP (100%) conditions (P = 0·001) coupled with a significant change in the slope of the regression line during the final 60 s of the VO(2max) test, UP and HP (P = 0·0299) and UP and SP (P = 0·0296). These data suggest that a bout of prior-priming exercise promotes an increased incidence of plateau responses at VO(2max) . It is suggested that future studies address how such an approach can be adopted without prior knowledge of GET.     

Cerebrovascular responses to cold pressor test during static exercise in humans

The purpose of this study was to determine whether exercise modulates the responses of middle cerebral artery blood velocity (MCA V(mean)) and cerebrovascular conductance to sympathetic stimulation (i.e. cold pressor test--CPT). To accomplish this, MCA V(mean) responses were assessed during CPT, static handgrip exercise (HG) at 30% of maximum voluntary contraction and combined condition (HG + CPT), assigned in a counterbalanced order, in eight healthy subjects. Blood pressure (BP), cardiac output (CO) and end-tidal partial pressure of carbon dioxide (PETCO(2)) were also measured non-invasively, and an index of vascular conductance was calculated for MCA (CVCi). BP increased from rest (P < 0·05) during CPT and HG and was additionally augmented during HG + CPT (P < 0·05 versus rest, CPT and HG). Despite the greater augmentation in BP during HG + CPT, MCA V(mean) was similarly increased during both HG (18·5 ± 2%, P < 0·05 versus rest) and combined condition (19·6 ± 2%, P < 0·05 versus rest). MCA V(mean) remained unchanged from rest during CPT only. CVCi was slightly reduced (P < 0·05) from rest during HG but was greatly reduced by CPT (P < 0·05 versus rest). The reduction in CVCi evoked by CPT at rest (-15 ± 2%, P < 0·05 versus rest) was significantly attenuated during HG (-8 ± 2%, P < 0·05 versus CPT). Increases in CO were similar in all trials, and PETCO(2) was unchanged from rest throughout the experiments. In summary, the cerebral conductance index decreases during the cold pressure test while that reduction is smaller when the CPT is conducted during the HG. This was critical for the maintenance of MCA V(mean) during combined condition.     

Effects of exercise training on oxygen uptake kinetic responses in women with type 2 diabetes.

OBJECTIVE: Women with uncomplicated type 2 diabetes have both a decreased maximal oxygen consumption (VO2max) and slowed oxygen uptake (VO2) kinetics at the onset of exercise compared with nondiabetic women. These abnormalities are seen not only at maximal workloads, but also at the onset of low-level exercise. To evaluate the hypothesis that VO2max and VO2 kinetics would improve with exercise training in untrained people with type 2 diabetes, we measured these parameters in premenopausal sedentary women before and after 3 months of supervised exercise training. RESEARCH DESIGN AND METHODS: A total of 8 women with type 2 diabetes, 9 overweight nondiabetic women, and 10 lean nondiabetic women were studied. At baseline and after 3 months of exercise training, subjects underwent bicycle ergometer testing to obtain VO2max and VO2 kinetics data. RESULTS: On entry, women with type 2 diabetes had the lowest VO2max and slowest VO2 kinetics of the three groups. After exercise training, the women with type 2 diabetes improved their VO2max more than the lean and overweight control women: 28 vs. 5 and 8%, respectively (P < 0.05 for the diabetic group vs. both control groups). In the group with diabetes, VO2 kinetics improved by 39 and 22% at 20 and 30 W, respectively. For the control subjects, VO2 kinetics did not improve at any workload in either group. CONCLUSIONS: Despite beginning with the lowest VO2max and slowest VO2 kinetics, subjects with type 2 diabetes benefited more from an exercise training program than did control subjects. These findings suggest that in addition to its known metabolic effects, exercise training in individuals with type 2 diabetes may be an effective therapy to improve the cardiovascular response to exercise and to overcome low-level exercise impairment as reflected by improved VO2max and VO2 kinetics. If the ability to make circulatory adjustments at the beginning of exercise at low workloads is improved by an exercise training program, as suggested by the VO2 kinetics data, the clinical significance of exercise for people with type 2 diabetes is clear.     

Oxygen uptake kinetics during exercise in chronic heart failure: influence of peripheral vascular reserve.

Exercise performance in chronic heart failure is severely impaired, due in part to a peripherally mediated limitation. In addition to impaired maximal exercise capacity, the O(2) uptake (VO(2)) response during submaximal exercise may be affected, with a greater reliance on anaerobiosis leading to early fatigue. However, the response of VO(2) kinetics to submaximal exercise in chronic heart failure has not been studied extensively; in particular, the relationship between oxygen utilization and the peripheral response to exercise has not been studied. The present investigation examined the time-constant (tau, corresponding to 63% of the total response fitted from exercise onset) of the VO(2) kinetics on-response to submaximal exercise and its relationship to maximal peripheral blood flow in patients with chronic heart failure, and compared responses with those in healthy sedentary subjects. Subjects were 10 patients with chronic heart failure (NYHA class II/III). The mean age was 50+/-12 years, with a mean resting left ventricular ejection fraction of 25+/-9%. Controls were 10 age-matched healthy subjects. VO(2(max)) was first determined for all subjects. Repeated transitions from rest to exercise were performed on a cycle ergometer while measuring breath-by-breath responses of VO(2) at a fixed work rate of 50% of VO(2(max)) (heart failure patients and healthy controls) and at a work rate equivalent to the average in heart failure patients (65 W; healthy controls only). On a separate occasion, post-maximal ischaemic exercise calf blood flow was measured (strain-gauge plethysmography).Whereas heart failure subjects displayed a significantly prolonged VO(2) kinetics response at a similar absolute workload (i.e. 65 W), as indicated by a longer tau value (42 s, compared with 22 s in controls; P<0.01), there was no difference in tau at a similar relative work rate [50% of VO(2(max))]. In addition, heart failure subjects demonstrated a lower maximal calf blood flow (P<0.05) than control subjects. These results indicate that patients with heart failure have a prolonged VO(2) kinetics on-response compared with healthy subjects at a similar absolute work rate (i.e. 65 W), but not at a similar relative work rate [50% of VO(2(max))]. Thus, despite a reduced maximal calf blood flow response associated with heart failure, it does not appear that this contributes to an impairment of the submaximal exercise response beyond that explained by a reduced maximal exercise capacity [VO(2(max))].     

计划性锻炼改善血液透析患者运动机能、心理状态及生活质量的护理研究

目的：研究有计划的锻炼对血液透析患者生活质量以及心理状态改善的影响。方法研究共纳入2011年10月～2012年12月在我院接受血液透析并能接受运动试验的62例患者,其中,男38例,女24例,年龄25～53岁,平均年龄（45±7）岁。每次锻炼项目包括跑步机和健身自行车。每次运动时间为60 min ,每周2次（透析当天不进行运动）,一共持续12周。整个计划开始时和结束时测定患者的运动能力,即最大耗氧量和运动耐量。此外,在上述两个时间段使用量表对患者的生活质量和抑郁、焦虑程度作出评估并比较。结果12周的锻炼计划结束后,患者的最大耗氧量由（24．5±4．9） ml/（kg · min）上升到（30．1±5．9） ml/（kg · min）,前后数据比较差异有显著意义（ P＜0．05）。运动耐量时间从开始时的（470±85） s上升到（592±110） s ,计划前运动耐量与计划后运动耐量相比差异有显著意义（P＜0．05）。患者完成运动计划前后测得的抑郁评分和焦虑评分均有所改善。此外,患者的生活质量评分也得到了显著提高。结论有计划的锻炼可以改善血液透析患者的生理机能,消除不良心理状态,提高生活质量,值得在临床护理工作中推广。     

吸入沙美特罗替卡松对中重度慢性阻塞性肺疾病患者运动耐力的影响

目的 通过对吸入沙美特罗替卡松粉(SFC)治疗中重度慢性阻塞性肺疾病(COPD)患者进行研究,探讨吸入糖皮质激素联合长效β2受体激动剂对中重度COPD静息肺功能和运动耐力的影响.方法 选择稳定期的中重度COPD患者53例,随机分为治疗组与对照组.治疗组吸入SFC(每泡含沙美特罗50μg,丙酸氟替卡松250 μg),每日2次,每次1喷,对照组给予一般治疗.24周后,观察患者肺功能(PFT)及心肺运动试验(CPET)各项生理参数指标的变化.结果 试验开始时,治疗组与对照组的PFT参数与CPET参数相比较,无统计学差异.SFC治疗24周后,治疗组的静态肺功能指标显示,患者用力肺活量(FVC)由治疗前(2.5±0.6)L增加至(3.0±0.5)L,第一秒用力呼气量(FEV1)由治疗前(1.1.4±0.4)L增加至(1.3±0.2)L,深吸气量(IC)由治疗前(1.9±O.4)L增加至(2.2±0.5)L,胸廓内气量(ITGV)由治疗前(5.8±0.6)L减低至(5.1±0.7)L,残气量(RV)由治疗前(4.8±0.7)L减低至(4.0±0.8)L,肺总量(TLC)由治疗前(7.6±1.1)L减低至(7.3±1.0)L,差异均有统计学意义;CPET发现,峰值功率(Peak WR)由治疗前(86.2±13.5)watt增加至(91.2±15.1)watt,稍有改善,但无显著的统计学差异;峰值摄氧量(Peak VO2)由治疗前(1341.2±261.4)ml/min增加至(1796.0±282.5)ml/min,峰值公斤摄氧量(Peak VO2/kg)由治疗前(20.7 ±5.0)ml·min-1·kg-1增加至(23.5±4.4)ml·min-1·ks-1,Peak VCO2由治疗前(1671.4±254.3)ml/min增加至(1995.1±241.7)ml/min,峰值氧脉搏(Peak O2 pulse)由治疗前(7.5±2.3)ml/beat增加至(10.9±2.7)ml/beat,峰值通气量(Peak VE)由治疗前(31.2±10.2)L/min增加至(37.2±9.2)L/min,死腔/潮气量(VD/VT)由治疗前(39.4±7.0)%减低至(32.4±6.1)%,二氧化碳通气当量最低值(Lowest VE/VCO2)由治疗前32.5±3.2减低至28.8±2.9;PET中IC改善值与CPET中Peak VO2、Peak VO2/ks、Peak VE、VD/VT、Lowest VE/VCO2:等的改善值有良好的相关性,而FEV1的改善值与上述CPET的参数改善无显著相关.对照组用药前后,患者PFT及CPET各参数无明显的变化.结论 中重度COPD患者的运动耐力显著减低,长期使用SFC后,其气流受限的改善程度有限,峰值运动功率仅有轻微改善,但患者的静息及运动时的肺过度充气状态明显减轻,通气/血流匹配状况明显好转,通气效率得到显著改善,从而提高运动耐受能力.     

体重超标对慢性阻塞性肺疾病患者运动耐量与生存质量的影响

目的探讨慢性阻塞性肺疾病（COPD）患者中体重超标人群与体重正常人群运动耐量及生活质量的差异。方法将入选的113例COPD患者分为三组：正常体重组（43例）,超重组（34例）,肥胖组（36例）。对所有的受试对象进行静息肺功能检查,踏车实验,圣·乔治呼吸问卷评分。采用SPSS13．0统计软件进行分析。结果体重正常组的FEV。／FVC为（47．28±3．82）％,超重组为（52．50±8．23）％,肥胖组为（53．20±8．30）％,三组间比较差异有统计学意义（F=8．76,P〈0．01）;组间比较正常组与超重组、肥胖组间差异均有统计学意义（P〈0．01）,超重组与肥胖组间差异无统计学意义（P〉0．05）;心肺功能运动试验中三组的V02max／kg分别为体重正常组（21．80±3．67）ml·kg^-1·min^-1,超重组（20．19±4．14）ml·kg^-1·min^-1,肥胖组（18．98±3．22）ml·kg^-1·min^-1,差异有统计学意义（F=5．82,P〈0．01）,组问比较正常组与超重组比较差异无统计学意义（P〉0．05）,超重组与肥胖组比较差异无统计学意义（P〉0．05）,正常组与肥胖组比较差异有统计学意义（P〈0．05）;三组间的圣·乔治呼吸问卷评分各项指标与总分差异均无统计学意义（P〉0．05）。结论体重适度增加可提高静息肺通气功能,但明显超出正常水平则会影响患者的运动耐量与运动肺通气。     

心肌病心肺运动负荷研究：室内传导阻滞和舒张充盈功能的影响

目的双心室起搏已经广泛用于心肌病伴有和不伴有QRS间期延长患者,提高运动能力、改善心肺储备功能是双心室起搏的目标。为了提高双心室起搏时QRS间期与舒张功能对PVO2、VE／VCO2斜率等心肺功能的预测性,对心肌病患者静态室内传导阻滞和舒张功能与运动心肺功能相关性变化进行了评价。方法42例心肌病患者（缺血性心肌病11例,扩张型心肌病31例）,其中21例正常组（QRS间期〈120ms）,21例异常组（QRS间期〉120ms）,进行心肺联合运动试验和彩色多普勒超声心动图检查。运动前、运动高峰和运动后分别测定运动耐量、PVO2、AT、VE／VCO2斜率。结果心肌病患者中,异常组短轴内径大于正常组,房室环运动幅度无明显差异,运动PVO2、AT、VE／VCO2斜率明显改变,舒张时间缩短,心电图QRS间期和舒张充盈时间与PVO2、AT及VE／VCO2斜率有显著相关性（P〈0．05）。结论心电图QRS间期和彩色多普勒超声心动图测定的舒张功能与运动PVO2和AT及VE／VCO2斜率相关,心电图QRS间期和舒张功能有助于预测心肌病患者心脏再同步时心肺储备功能。因此,运动心肺功能不但与QRS间期有关,而且与舒张充盈功能有关。当双心室起搏无反应时,改善舒张功能是另一有效途径。     

Importance of AV synchronous pacing during low intensity exercise evaluated by oxygen kinetics

It has been shown that dual chamber pacing with preservation of AV synchrony (DDD) is superior to fixed rate ventricular (VVI) or rate responsive ventricular (VVIR) pacing modes, as evaluated by ventilatory response to exercise. Previous studies have focused on the benefits of maintained AV synchrony at maximal exercise. However, there are limited data comparing O2 kinetics in different pacing modes during low intensity exercise, representing the majority of daily activities. This study aimed to provide an evaluation of different pacing modes using O2 kinetics during low intensity exercise. Nineteen patients (age 61 +/- 18 years) with complete AV block underwent low intensity treadmill exercise (35 W) with simultaneous evaluation of symptoms and O2 kinetics in three pacing modes. The first test was performed in DDD mode followed by a second test in VVIR mode with a programmed heart rate corresponding to the sinus rate during the first test. After 6 minutes of each test, the mode was switched from DDD to VVIR and vice versa. The third test was performed in VVI mode at 70 beats/min. O2 kinetics were defined as O2 deficit (time [rest to steady state] x delta VO2-sigma VO2 [rest to steady state]) and mean response time (MRT) of oxygen consumption (O2 deficit/delta VO2). The O2 deficit was 551 +/- 134 mL in DDD pacing, 634 +/- 139 mL in VVIR pacing, and 648 +/- 179 mL in VVI pacing (P = 0.001). MRT was 49 +/- 7.8 seconds in DDD pacing, 54.7 +/- 9.5 seconds in VVIR pacing, and 57.4 +/- 11.0 seconds in VVI pacing (P = 0.002). Ten (53%) patients developed symptoms during switch from DDD to VVIR mode whereas the switch from VVIR to DDD mode was not perceived by any patient (P < 0.001). In conclusion, our study shows an impact of AV synchronous pacing and heart rate adaptation on O2 kinetics during low intensity exercise that correspond to casual daily life activities. Our observations may have clinical implications for the management of patients with complete AV block.     

Assessment of exercise capacity in women with type 2 diabetes

The primary aim of this study was to compare the maximal oxygen uptake as evaluated from a submaximal exercise test (EVO2peak) to direct measurements of VO2peak during a maximal exercise test as means of monitoring the aerobic endurance capacity in women with type 2 diabetes (T2D). Twenty-seven women with T2D participated in the study. The program consisted of combined group training 1 h twice a week during 12 weeks and walks 1 h per week. EVO2 max was estimated using a submaximal exercise test on a bicycle ergometer ad modum Astrand. VO2peak and maximal work rate were measured using an incremental maximal exercise test on an electrically braked bicycle ergometer at baseline and after 6 and 12 weeks. EVO2peak was higher than VO2peak at baseline and significantly higher at 12 weeks (EVO2peak1.92+/-0.54 l min(-1), VO2peak 1.41+/-0.36, P<0.005). Maximal work rate increased significantly after 12 weeks (12+/-15, P<0.005) compared to baseline. The main finding of this study was that EVO2peak assessed using a submaximal exercise test, systematically overestimated VO2peak. The combined group training increased maximal work rate but not VO2peak. This is likely to reflect peripheral adaptation to exercise and/or improved mechanical efficiency.     

The effect of acute blood-flow-restricted resistance exercise on postexercise blood pressure

Introduction: Blood‐flow‐restricted (BFR) exercise is an emerging type of exercise that may be particularly beneficial to elderly or special populations. These populations may also benefit from reductions in blood pressure (BP). The effect of BFR exercise on postexercise BP has not been examined; this should first be examined in a young, healthy population as a preliminary investigation. Purpose: The main purpose of this study was to determine whether postexercise hypotension (PEH) occurred following low‐intensity [20% 1 repetition maximum (1‐RM)] BFR resistance exercise. A secondary purpose was to compare this response to both a work‐matched low‐intensity (20% 1‐RM) (LI) and a traditional high‐intensity (70% 1‐RM) resistance exercise bout (HI). Methods: In a randomized cross‐over design, ten normotensive, young (18–35 years) men performed one of the three lower‐body resistance exercise bouts (HI, LI or low‐intensity BFR) during separate visits to the laboratory. Brachial BP, cardiac ultrasound and calf blood flow measurements were taken prior to and 30 and 60 min following exercise. Repeated measures analysis of variance (3 × 3; condition × time) was performed on all variables. Results: A significant interaction (P<0·05) was found for brachial systolic blood pressure which decreased following HI only. Significant interactions (P<0·05) were also seen for heart rate, total peripheral resistance and calf vascular resistance. Conclusion: Postexercise hypotension occurred only following HI. Thus, if one is exercising with the intent of lowering BP, HI resistance exercise may be more useful than low‐intensity BFR resistance exercise.     

Sympatho-vagal interaction in the recovery phase of exercise

Reciprocal autonomic regulation occurs during incremental exercise. We hypothesized that sympatho-vagal interplay may become altered after exercise because of the differences in recovery patterns of autonomic arms. The cardiac vagal activity was assessed by measurement of beat-to-beat R-R interval oscillations using a Poincaré plot method (SD1), and muscle sympathetic nervous activity (MSNA) was measured from peroneus nerve by a microneurography technique during and after exercise in 16 healthy subjects. Autonomic regulation was compared between the rest and after exercise (3·5 ± 1·0 min after exercise) at equal heart rates (HR). SD1 was at the equal level at the recovery phase (40 ± 21 ms) compared to the resting condition (38 ± 16 ms, P = ns) at comparable HR (57 ± 10 for both). MSNA was higher at the recovery phase (40 ± 19 burst per 100 heartbeats) than at rest (25 ± 13 burst per 100 heartbeats, P<0·0001). The difference of MSNA activity between rest and late recovery phase had a strong positive correlation with the difference in SD1 (r = 0·78, P<0·001) at equal HRs. Subjects who have a higher sympathetic activity in the recovery phase of exercise have a more augmented cardiac vagal activity resulting in an accentuated sympatho-vagal outflow. The altered autonomic interaction observed here may partly explain the clustering of various cardiovascular events to the recovery phase of exercise.     

Effect of the VO2 time-averaging interval on the reproducibility of VO2max in healthy athletic subjects

AIMS: Limited research has investigated the most appropriate oxygen uptake (VO2) data averaging method to obtain reliable and valid maximal oxygen uptake (VO2max) values. This study investigated the effect of the VO2 time-averaging interval on the reproducibility of VO2max. METHODS AND RESULTS: Twenty-two competitive distance runners (six female) performed two identical incremental treadmill tests to their limit of exercise tolerance separated by at least 48 h. Commencing at 7 km h(-1), running speed was increased by 1 km h(-1) per minute for five stages and 0.5 km h(-1) thereafter. Breath-by-breath VO2 data collected during each incremental test were time-averaged over 10-, 15-, 20-, 30- and 60-s and the highest averaged VO2 value was regarded as VO2max for each time-averaging interval. The VO2max values derived from different VO2 time-averaging intervals were significantly different for the first (F = 39.6; P<0.001) and second (F = 68.9; P<0.001) incremental test. There was a tendency for VO2max to significantly increase as the time-averaging interval became shorter. The reproducibility of VO2max was similar for all five VO2 time-averages, with no significant differences between the within-subject variance (F = 0.4; P = 0.6). CONCLUSION: The results of this study suggests that the reproducibility of VO2max is not affected by the length of the VO2 time-average interval. However, VO2max was significantly altered by changing the VO2 time-averaging interval between 10 and 60 s. Consistency in the VO2 time-averaging interval is therefore an important methodological consideration for repeated determinations of VO2max.     

Guidelines for premeal insulin dose reduction for postprandial exercise of different intensities and durations in type 1 diabetic subjects treated intensively with a basal-bolus insulin regimen (ultralente-lispro)

OBJECTIVE: To evaluate and validate appropriate premeal insulin dose reductions for postprandial exercises of different intensities and durations to minimize the risk of exercise-induced hypoglycemia in type 1 diabetic subjects. RESEARCH DESIGN AND METHODS: Eight male type 1 diabetic patients on a basal-bolus insulin regimen of ultralente (UL) as basal insulin and lispro (LP) as premeal insulin were tested in a randomized, crossover fashion during postprandial exercise at 25% VO2max for 60 min, 50% VO2max for 30 and 60 min, and 75% VOmax for 30 min starting 90 min after a standardized mixed breakfast (600 kcal, 75 g carbohydrates). Each subject served as his own control and was rested after a full dose of insulin LP (LP 100%) and/or 50% (LP 50%) and/or 25% (LP 25%) of the current dose. RESULTS: At all intensities, the full premeal insulin dose was associated with an increased risk of hypoglycemia. At 25% VO2max for 60 min, a 50% reduction in the premeal insulin dose resulted in plasma glucose of -0.62 mmol/l compared with baseline at the end of exercise. At 50% VO2max for 30 and 60 min, 50 and 75% reductions of the premeal insulin dose were associated with plasma glucose of -0.39 and +0.49 mmol/l, respectively, at the end of the exercise. At 75% VO2max, a 75% reduction of the premeal insulin dose was required to achieve appropriate postexercise plasma glucose (+0.71 mmol/l). Such reductions in the premeal insulin dose resulted in a 75% decrease in the incidence of exercise-induced hypoglycemia. CONCLUSIONS In well-controlled type 1 diabetic subjects on intensive insulin therapy with the basal-bolus (UL-LP) insulin regimen, risk of hypoglycemia can be minimized during postprandial exercises of different intensities and different durations by appropriate reduction of premeal insulin LP.     

Dissociated time course recovery between rate of force development and peak torque after eccentric exercise

This study investigated the association between isokinetic peak torque (PT) of quadriceps and the corresponding peak rate of force development (peak RFD) during the recovery of eccentric exercise. Twelve untrained men (aged 21·7 ± 2·3 year) performed 100 maximal eccentric contractions for knee extensors (10 sets of 10 repetitions with a 2-min rest between each set) on isokinetic dynamometer. PT and peak RFD accessed by maximal isokinetic knee concentric contractions at 60° s(-1) were obtained before (baseline) and at 24 and 48 h after eccentric exercise. Indirect markers of muscle damage included delayed onset of muscle soreness (DOMS) and plasma creatine kinase (CK) activity. The eccentric exercise resulted in elevated DOMS and CK compared with baseline values. At 24 h, PT (-15·3%, P = 0·002) and peak RFD (-13·1%, P = 0·03) decreased significantly. At 48 h, PT (-7·9%, P = 0·002) was still decreased but peak RFD have returned to baseline values. Positive correlation was found between PT and peak RFD at baseline (r = 0·62, P = 0·02), 24 h (r = 0·99, P = 0·0001) and 48 h (r = 0·68, P = 0·01) after eccentric exercise. The magnitude of changes (%) in PT and peak RFD from baseline to 24 h (r = 0·68, P = 0·01) and from 24 to 48 h (r = 0·68, P = 0·01) were significantly correlated. It can be concluded that the muscle damage induced by the eccentric exercise affects differently the time course of PT and peak RFD recovery during isokinetic concentric contraction at 60° s(-1). During the recovery from exercise-induced muscle damage, PT and peak RFD are determined but not fully defined by shared putative physiological mechanisms.     

Comparison of carbohydrate-containing and carbohydrate-restricted hypocaloric diets in the treatment of obesity. Endurance and metabolic fuel homeostasis during strenuous exercise.

Eight untrained, obese females (greater than 30% body fat), ages 25-33 yr, were studied before, at 1 wk, and after 6 wk while taking either of two 830-kcal/d diets: carbohydrate-containing (CC) group (n = 4): 35% protein, 29% fat, 36% carbohydrate-restricted (CR) group (n = 4): 35% protein, 64% fat, 1% carbohydrate. Endurance, at approximately 75% of VO2max (maximum oxygen uptake) on a cycle decreased from base line by 50% at 1 and 6 wk in the CR group, but there was no change in the CC group. Preexercise muscle glycogen (vastus lateralis) did not change significantly in the CC group, but was decreased by 49% in the CR group after 1 wk, and by 51% after 6 wk. There was a close correlation between percent decrease in resting muscle glycogen and percent decrease in endurance (r = 0.79, P less than 0.01). The mean fasting and exercise plasma glucose concentration was lower in the CR group than in the CC group after 6 wk, but no subject became hypoglycemic during exercise. Serum FFA, lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, insulin, and glucagon changed similarly in the two groups during exercise at base line, 1 and 6 wk. Glycerol concentration was higher in the CR group during exercise only after 6 wk. Increases in serum lactate concentrations, and a mean exercise respiratory quotient of 0.93 suggested that cycle exercise at approximately 75% VO2max used predominantly glucose as a fuel. Conclusions: Resting muscle glycogen and endurance, during cycle exercise at approximately 75% VO2max, were maintained during a 36% carbohydrate, 830-kcal/d diet. In contrast, significant decreases, occurred in resting muscle glycogen and endurance, during similar exercise, after 6 wk of a 1% carbohydrate, 830-kcal/d diet.     

负荷运动对能量代谢的影响及研究

目的探讨渐增负荷最大运动后的过量氧耗与血乳酸、血糖及氨基酸代谢的变化关系。方法受试者为10名男子健康大学生。采用活动跑台方法进行渐增负荷跑至力竭为止。结果运动结束30min,吸氧量恢复到安静水平时,血乳酸浓度仍比安静时水平高,运动中丙氨酸上升,运动结束30min丙氨酸减少,但并未恢复到安静时的水平。结论过量氧耗除用于血乳酸的消耗外,可能生要用于丙氨酸代谢中的糖新生。     

Maximal oxygen uptake at the same fat-free mass is greater in men than women

Maximal oxygen uptake (VO(2max)) is commonly divided by body mass or fat-free mass (body mass minus fat mass) in order to make it size independent so that comparisons among persons of different size can be made. However, numerous studies have shown that the ratio created is not size-independent. Analysis of covariance (ANCOVA) allows a dependent variable to be compared between groups at a common value of a covariate. The purpose of this study was to compare VO(2max) at the same fat-free mass (FFM) in 230 sedentary subjects (half men) who ranged in age from 20 to 70 years. The subjects underwent maximal cardiopulmonary exercise testing on a cycle ergometer as ventilation and the expired gas fractions were being measured. Two ANCOVA models were evaluated. The dependent variable, fixed factor and covariate(s) in the linear model were VO(2max), sex and FFM, respectively. The corresponding terms in the log-linear model were ln VO(2max), sex, and ln FFM and age. Sex made a significant contribution to both models. In the linear model, the mean VO(2max) at the same FFM was 27% higher in men (2,444 versus 1,929 ml min(-1); P<0.001). In the log-linear model, the corresponding value at the same FFM and age was 32% higher in men (2,368 versus 1,794 ml min(-1); P<0.001). The goodness of fit indices of squared multiple correlation coefficient and standard error of estimate were significantly better for the log-linear model. We conclude that VO(2max) at the same FFM is considerably higher in men than in women who have a sedentary lifestyle.     

Maximal short term exercise capacity in healthy subjects aged 15-70 years

Fifty males and 50 females, 15-71 years of age, exercised maximally for 30 s on an isokinetic ergometer at a pedalling frequency of 60 rev./min. Results were compared with maximal oxygen uptake (VO2 max.) obtained in a progressive incremental exercise test. Total work in 30 s was higher in males than females, declined linearly by about 6% per decade of age (r = -0.65), and was related closely to height (r = 0.75) and to lean thigh volume estimated anthropometrically (r = 0.84). A close association with vital capacity (r = 0.86) was also found that accounted statistically for the combined effects of age and height. The percentage decline in power during 30 s (fatigue index) was lower in subjects reporting greater leisure activity. A close relationship was found between total work in 30 s and VO2max. (r = 0.86), with vital capacity and leisure activity exerting additional influences on VO2max. (P less than 0.001; multiple r = 0.93). The well-established reduction with age in VO2max. is associated with an apparent parallel reduction in the power output capacity of large muscle groups recruited in heavy dynamic leg exercise.