Aerobic exercise intensity influences hypotension following concurrent exercise sessions

The study investigated whether resistance and aerobic concurrent exercise (CE) with different intensities influenced postexercise hypotension (PEH). 21 healthy men (20.7±0.7?yr) performed 4 sessions: control [CTL 60?min of rest], and CE1, CE2, and CE3 consisting respectively of 2 sets of 6 exercises at 80% 1RM followed by 30?min of cycle ergometer exercise at 50%, 65%, and 80% of peak oxygen consumption (VO2peak). All sessions lasted approximately 60?min and began with resistance prior to aerobic sessions. Systolic (SBP) and diastolic (DBP) blood pressure (BP) were assessed at baseline and every 10?min during 120-min recovery. The magnitude of SBP decrease was similar after all CE sessions [CE1: 4.2±2.5?mmHg; CE2: 4.8±2.7?mmHg; CE3: 6.0±2.0?mmHg; p=0.06], but the PEH lasted approximately 1?h longer following CE2 and CE3 [120?min] compared to CE1 [60-70?min] (P<0.05). The magnitude of DBP decrease was slightly greater after CE3 and CE2 [2?mmHg] than after CE1 [1?mmHg] (P<0.05), being longer following CE3 [60?min] compared to CE2 and CE1 [40?min] (P<0.05). In conclusion, CE sessions combining resistance and aerobic sessions elicited PEH, especially when the intensity of the aerobic exercise was higher than 65% VO2peak.     

Cardiac output and stroke volume changes with endurance training: the HERITAGE Family Study

PURPOSE: The purpose of this study was to determine the magnitude of changes in cardiac output (Qc), stroke volume (SV), and arterial-mixed venous oxygen difference (a-vO2 diff) during submaximal exercise following a 20-wk endurance training program, with the primary focus on identifying differences in response by race, sex, and age. METHODS: The participants in this study (N = 631) were healthy and previously sedentary men (N = 277) and women (N = 354) of varying age (17-65 yr) and race (blacks, N = 217; whites, N = 414) who had completed the HERITAGE Family Study protocol. After baseline measurements, participants trained on cycle ergometers 3 d x wk(-1) for a total of 60 exercise sessions starting at the HR associated with 55% of maximal oxygen uptake (VO2max) for 30 min/session and building to the HR associated with 75% of VO2max for 50 min/session, which was maintained during the last 6 wk. HR, Qc (CO2 rebreathing), and SV (Qc/HR) were determined in duplicate at 50 W and at 60% of VO2max on two different days both before and after training. RESULTS: After training, there were significant decreases in HR and Qc, and significant increases in SV and a-vO2 diff at 50 W (except for no change in a-vO2 diff in black men). The changes in HR differed by sex and age, and the changes in SV, Qc, and a-vO2 diff differed by race. Qc decreased by 0.6 L x min(-1) at 50 W for the total sample, consistent with the decrease in VO2 at this power output. At 60% of VO2max HR decreased, and SV, Q, and a-VO2 diff increased. There were small differences in response by sex (HR and SV), race (HR), and age (HR and Qc). CONCLUSION: It is concluded that the cardiovascular systems of men and women, blacks and whites, and younger and older subjects are not limited in their ability to adapt to endurance training.     

Maximal oxygen uptake after attenuation of cardiovascular drift during heat stress

INTRODUCTION: Exercise intensity is often regulated in hot conditions by maintaining a constant target heart rate (HR) to counteract increased physiological strain and thereby avoid premature fatigue. It is unknown, however, whether the HR-percent maximal oxygen uptake (%VO2max) relationship is maintained during prolonged exercise in the heat when the rise in HR concomitant with cardiovascular drift (CV drift) is eliminated by lowering exercise intensity. The purpose of this study was to determine if VO2max is reduced when exercise intensity and absolute VO2 are lowered by a magnitude sufficient to reduce CV drift and maintain constant HR during prolonged exercise in the heat, and thereby examine if the HR-%VO2max relationship is preserved. METHODS: Seven men cycled at 60% VO2max in 35 degrees C for 15 min (one trial) and 45 min (two trials) while HR rose over time (HRvar) or remained constant (HRcon). VO2max was measured immediately after the 15 and 45 min trials to correspond with the same time interval in which CV drift occurred. RESULTS: Power output decreased 37%, VO2 decreased 24%, and VO2max decreased 7.5% from 15 to 45 min in HRcon, while HR remained the same. In HRvar, HR increased 13%, SV decreased 10%, and VO2max decreased 15%. DISCUSSION: %VO2max was decreased from approximately 60% to 50% to hold HR constant in these conditions, so the HR-%VO2max relationship was not preserved in the absence of CV drift. Attenuating CV drift by lowering exercise intensity only partially eliminated the reduction in VO2max after prolonged exercise in the heat.     

Rate and amplitude of adaptation to two intensities of exercise in men aged 65-75 yr

PURPOSE: To test the hypothesis that in males aged 65-75 yr when the total amount of work completed is similar in endurance training three times per week for 12 wk at either 50% or 70% peak oxygen uptake (VO2(peak)), there will be no significant difference in time course and amplitude of selected responses. METHODS: Subjects were randomly assigned to three groups: 70% VO2(peak), N = 19; 50% VO2(peak), N = 16; or control group, N = 19. Subjects underwent a maximal cycle exercise test and blood volume (Evans Blue) determination at 0, 4, 8, and 12 wk. A submaximal exercise test (50 W) was conducted at weeks 0 and 12 where cardiac output was determined. The exercise groups maintained the same exercise relative intensity throughout the 12 wk and completed a similar total amount of work. RESULTS: There were significant and similar increases in peak VO2, power and heart rate (HR) for both exercise groups. Linear models best described the time course for peak power and HR in both exercise groups. In the 70% VO2(peak) group, a quadratic model for VO2 and a linear model for VE were the best fit. There were no significant changes in blood or plasma volume for any groups over the 12 wk. Significant increases in stroke volume and significant decreases in HR at 50 W were found in both exercise groups after training. CONCLUSION: Moderate-intensity cycle exercise (50% VO2(peak)) to achieve 180-200 kJ per session, three times a week for 12 wk is a safe and effective stimulus for healthy asymptomatic men aged 65-75 yr to improve functional capacity in a primarily linear manner.     

Cardiovascular responses during upright and semi-recumbent cycle ergometry testing

To compare cardiovascular (CV) responses during cycle ergometry testing, 20 unmedicated mild hypertensive subjects (10 male, 10 female; mean age = 47.9 yr) underwent exercise testing on an upright (UP) cycle and a semi-recumbent (SR) cycle. Tests were administered in counterbalanced order on two separate days. Heart rate (HR), blood pressure (BP), ventilation (VE), and rate pressure product (RPP) were recorded at absolute workloads (1.0 and 1.5 l.min-1) as well as at relative workloads (50, 75, and 90% of VO2 peak). In addition, the CV variables were measured at rest and peak exercise for each position. At absolute submaximal levels, women had higher HR, VE, and RPP values in both positions, reflecting responses at a greater percentage of their maximum exercise capacity. At relative workloads, HRs were significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Men had greater systolic blood pressure (SBP) and RPP in both positions, and RPP was significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Women displayed lower VE at all relative workloads. At peak exercise, subjects achieved significantly higher peak heart rates on the upright cycle (UP = 163 bpm, SR = 157 bpm). The UP cycle was associated with higher levels of peak VO2. The ability to achieve a higher HR and greater VO2 at peak exercise suggests that the UP cycle ergometer may be a preferable mode to the SR ergometer for evaluating maximal exercise performance among patients with mild hypertension.     

Fluid ingestion attenuates the decline in VO2peak associated with cardiovascular drift

INTRODUCTION/PURPOSE: This study investigated whether manipulation of cardiovascular drift (CV drift) by changing exercise duration or by fluid ingestion is associated with altered peak oxygen uptake VO(2peak). METHODS: VO(2peak) was measured in 11 trained men immediately after they cycled at 60% control VO(2max) in 30 degrees C, 40% relative humidity for 15, 60, and 120 min with no fluid (15 NF, 60 NF, 120 NF) or 120 min with fluid (120 F). Stroke volume (SV), heart rate (HR), and related measures were measured in 120 NF and 120 F at 15, 60, and 120 min. RESULTS: Body mass decreased 0.7, 2.3, and 3.7% in 120 F, 60 NF, and 120 NF. SV at the end of submaximal exercise and VO(2peak) measured immediately thereafter were reduced significantly (P < 0.05) from 15-min values in 120 NF (13.8 and 8.7%) but not in 60 NF (4.6 and 1.2%) or 120 F (2.1 and 1.9%). CONCLUSIONS: The progressive decline in SV during prolonged, constant-rate submaximal exercise in a warm environment, reflective of increased cardiovascular strain associated with hyperthermia, dehydration, and other changes that occur over time, reduces VO(2peak). Fluid ingestion improves performance in prolonged exercise, in part, by mitigating the decline in SV and its determinants, and preserving VO(2peak).     

Heart rate and blood pressure changes with endurance training: the HERITAGE Family Study

PURPOSE: The purpose of this study was to determine the magnitude of change in resting and exercise heart rate (HR) and blood pressure (BP), by race, sex, and age, after a 20-wk endurance training program in 507 healthy and previously sedentary subjects from the HERITAGE Family Study. METHODS: After baseline measurements, subjects exercised on cycle ergometers 3 d x wk(-1) for a total of 60 exercise sessions starting at 55% of VO2max for 30 min x session(-1) and building to 75% of VO2max for 50 min x session(-1) for the last 6 wk. HR and BP at rest and during exercise (50 W, 60% of VO2max maximal exercise) were each determined in duplicate on two different days both before and after training (resting values at 24-h and 72-h posttraining). RESULTS: After the period of training, there was a small decrease in resting HR (-2.7 to -4.6 beats x min(-1) across groups at 72-h posttraining), and small changes (i.e., < 3 mm Hg) in resting systolic (SBP), diastolic (DBP), and calculated mean BP (MBP), which varied by race, sex, and age. During exercise at the same absolute work rate (50 W), HR, SBP, DBP, and MBP were all significantly reduced, with greater reductions in HR in women compared with men, and greater reductions in BP in blacks and older subjects compared with whites and younger subjects, respectively. At the same relative work rate (60% VO2max), HR, DBP, and MBP were reduced, but SBP remained unchanged. Blacks had a greater reduction in DBP, but whites had a greater reduction in HR. Finally, at maximal exercise, there was a small decrease in HR, with men and whites decreasing more than women and blacks; an 8 mm Hg increase in SBP, with men increasing more than women; a 4 mm Hg decrease in DBP, with blacks decreasing more than whites; and no change in MBP. CONCLUSION: In conclusion, the reductions in resting HR and BP with training were generally small, but the reductions during exercise were substantial and clinically important, with the older and the black populations experiencing greater reductions.     

Effect of hypervolemia on heart rate during 4 days of prolonged exercises

The aim was to evaluate the cardiodynamic adjustment during 4 days of prolonged exercises and to check if the plasma volume (PV) expansion which is observed generally during such events plays a role in this adaptation. Thirteen subjects exercised 5 hours per day on a cycle ergometer alternately with a treadmill for 4 days (D1 to D4) (6 x 50 min sessions per day). The individual cycle ergometer load and the treadmill speed were unchanged during each exercise session and throughout all the sessions, and corresponded to a moderate exercise intensity: 58 - 63 % of peak oxygen uptake (VO (2)peak). Heart rate (HR) was recorded every 15 s during each exercise session and VO (2) was measured from the expired air at the beginning and the end of each exercise session. Relative PV changes were measured from haematocrit and haemoglobin changes in the morning before the exercise bouts. No significant changes of VO (2) were observed between the first and the last exercise session i. e. for cycling: 2.1 +/- 0.2 l/min and for running: 2.4 +/- 0.3 l/min. Between the first and the last day, HR decreased from 143 to 129 bpm for cycle (p < 0.0001) and from 147 to 137 bpm (p = 0.01) for treadmill. As compared to D1, PV increased gradually from D2 (+ 1.8 % +/- 4.7 %) to D4 (+ 8.5 % +/- 4.7 %). The individual PV increases were significantly correlated with cycling HR decreases from D1 to D4 (r (2) = 0.40, p = 0.02). In conclusion, the 4 days' prolonged exercise induced a HR decrease during submaximal exercise without VO (2) drift. Here we suggested that this HR decline could be in part linked to the transient PV expansion.     

Cardiovascular adjustments to exercise distributed between the upper and lower body

The present study examined the hemodynamic differences between upper- and lower-body exercise where the total power output (PO) was proportionally distributed between the upper and lower body. Six males completed five combinations of arm-leg exercise at maximal and three submaximal intensities. The ratio of arm PO to total PO for each exercise combination was 0, 25, 50, 75, and 100%. At each submaximal intensity, VO2 and cardiac output (Q) were not different (P greater than 0.05) across exercise combinations. Likewise, heart rate (HR) responses were not different for 0, 25, 50, and 75% at level 1 (mean = 102, 102, 106, 106 beats.min-1, respectively), level 2 (mean = 114, 110, 119, 118 beats.min-1, respectively), and level 3 (mean = 127, 124, 132, 131 beats.min-1, respectively). However, HR for 100% (arm-only exercise) tended to be higher than 0% at level 1 (delta HR = 10 beats.min-1; P less than 0.10), level 2 (delta HR = 12 beats.min-1, P less than 0.06) and level 3 (delta HR = 10 beats.min-1; P less than 0.06). At level 1, stroke volume (SV) remained essentially unchanged from 0-75%, while SV at 100% (108 ml) was slightly though not significantly lower (P less than 0.10) than 0% (125 ml). At exercise levels 2 and 3, SV remained unchanged for 0 and 25%; however, SV at 50, 75, and 100% were generally lower (P less than 0.05) compared with 0%. These results indicate that involving the leg musculature to varying degrees during arm-leg exercise attenuates the hemodynamic differences observed during strict upper body versus strict lower body exercise.     

Cardiovascular effects of cadence and workload

Increases in cadence may augment SV during submaximal cycling (> 65 % VO2max) via effects of increased muscle pump activity on preload. At lower workloads (45 - 65 % VO2max), SV tends to plateau, suggesting that effects of increases in cadence on pump activity have little influence on SV. We hypothesized that cadence-induced increases in CO at submaximal workloads, where SV tends to plateau, are due to elevations in HR and/or O2 extraction. SV, CO, HR, VO2, and delta a - vO2 were assessed at 80 and 100 rpm during workloads of 50 % (LO) or 65 % (HI) of VO2max in 11 male cyclists. No changes in SV were seen. CO was higher at 100 rpm in 10 of 11 subjects at LO (18.1 +/- 2.7 vs. 17.2 +/- 2.6 L/min). VO2 at both workloads was greater at 100 than 80 rpm as was HR (LO: 129 +/- 11 vs. 121 +/- 10 beats/min; HI: 146 +/- 13 vs. 139 +/- 14 beats/min) (p < 0.05). delta a - vO2 was greater at HI compared to LO at 80 (15.1 +/- 1.6 vs. 13.6 +/- 1.3 ml) and 100 rpm (16.0 +/- 1.7 vs. 15.1 +/- 1.6 ml) (p < 0.05). Results suggest that increases in O2 demand during low submaximal cycling (50 % VO2max) at high cadences are met by HR-induced increases in CO. At higher workloads (65 % VO2max), inability of higher cadences to increase CO and O2 delivery is offset by greater O2 extraction.     

Competition between internal and external sources of information during exercise: influence on RPE and the impact of the exercise load

BACKGROUND: The purpose of this study was to investigate the influence of the exercise setting on perceived exertion during sustained low and high intensity cycling exercise. METHODS: Thirteen untrained males completed 4 15-min cycling sessions at 50% VO(2peak) and at 80% VO(2peak) under each of the following conditions: control, sensory deprived, video, and music. Ratings of perceived exertion (RPE) from Borg's 6-20 scale and heart rate (HR) were recorded at 5 min intervals during all sessions. RESULTS: RPE increased with exercise duration at both intensities and, as expected, was substantially higher at the harder workload. Exercising to music resulted in significantly lower RPE when compared to all other conditions at both the low and high workloads, while RPE was higher in the sensory deprived condition when compared to the other 3 conditions. However, RPE was similar for the control and video conditions at both workloads. A significant ordinal interaction existed between conditions and exercise duration during the low but not the high workload. While HR was higher for the harder workload and increased during each workload as a function of exercise duration, it was not different among the 4 conditions at either workload. CONCLUSIONS: Varying the type of sensory information available to the exercising individual did influence perceptual responses to the exercise with the degree of influence dependent on the intensity and duration of the exercise. These results are consistent with information processing models that suggest a limited capacity to attend to the information available. The type of information available, the work intensity, and the work duration were important elements influencing perceptual responses to exercise.     

Effect of intensity of aerobic training on VO2max

PURPOSE: To determine whether various intensities of aerobic training differentially affect aerobic capacity as well as resting HR and resting blood pressure (BP). METHODS: Sixty-one health young adult subjects were matched for sex and VO2max and were randomly assigned to a moderate- (50% VO2 reserve (VO2R), vigorous (75% VO2R), near-maximal-intensity (95% VO2R), or a nonexercising control group. Intensity during exercise was controlled by having the subjects maintain target HR based on HR reserve. Exercise volume (and thus energy expenditure) was controlled across the three training groups by varying duration and frequency. Fifty-five subjects completed a 6-wk training protocol on a stationary bicycle ergometer and pre- and posttesting. During the final 4 wk, the moderate-intensity group exercised for 60 min, 4 d.wk the vigorous-intensity group exercised for 40 min, 4 d.wk and the near-maximal-intensity group exercised 3 d.wk performing 5 min at 75% VO2R followed by five intervals of 5 min at 95% VO2R and 5 min at 50% VO2R. RESULTS: VO2max significantly increased in all exercising groups by 7.2, 4.8, and 3.4 mL.min.kg in the near-maximal-, the vigorous-, and the moderate-intensity groups, respectively. Percent increases in the near-maximal- (20.6%), the vigorous- (14.3%), and the moderate-intensity (10.0%) groups were all significantly different from each other (P < 0.05). There were no significant changes in resting HR and BP in any group. CONCLUSION: When volume of exercise is controlled, higher intensities of exercise are more effective for improving VO2max than lower intensities of exercise in healthy, young adults.     

Exercise intensity and blood pressure during sleep

Exercise, of appropriate intensity and duration, could help maintain normotension if post-exercise hypotension persists over subsequent everyday activities. Therefore, we monitored ambulatory blood pressure (BP) for 24 h following four separate exercise bouts which differed in intensity, duration and total work completed. At 08:00 h, six normotensive males completed a no exercise control and, in two further trials, 30 min of cycling at 70 % V O (2 peak) and 40 % V O (2 peak). A fourth trial involved cycling at 40 % V O (2 peak) for a time which equated total work with that in the most intense exercise trial. Between 20 min and 24 h after exercise, ambulatory BP, heart rate (HR) and wrist-activity were compared between trials using general linear models. Participants slept normally at night. Post-exercise changes in BP and HR were not affected by exercise intensity or total work completed from 20 min after exercise until nocturnal sleep-onset (p > 0.21). During sleep, mean arterial BP was lower following exercise at 70 % V O (2 peak) compared to the other trials (p = 0.03), including the 40 % V O (2 peak) trial equated for total work (90 % CI for difference = - 22.1 to - 0.1). We conclude that daytime exercise can elicit a physiologically meaningful lower BP during sleep and exercise intensity is the most important factor in this phenomenon.     

老年渔民肺肿瘤患者术后心肺功能变化的临床研究

目的 研究老年渔民肺肿瘤肺切除患者在静息及运动负荷状态下手术前后的心肺功能变化规律,为放宽老年肺肿瘤患者手术指征提供依据.方法 41例因患肺肿瘤行肺叶切除术的患者分为老年组24例(≥60岁)、中青年组17例(<60岁),分别于术前3～5 d和术后3～6个月在患者日常生活无障碍时,采用心肺功能仪和多普勒超声技术在静息及运动负荷状态下测定心肺功能,指标包括心率(HR)、左心室舒张末期容积(LVEDV)、每搏量(SV)、心输出量(CO)、左心室射血分数(LVEF)、呼吸频率(RR)、潮气量(VT)、每分通气量(VE)和氧摄取量(VO2),并对其结果进行分析比较.结果 所有患者在静息和运动负荷状态下心功能参数LVEDD和SV术后较术前均有明显降低(P<0.01),静息状态下HR、RR、VT手术前后比较差异有统计学意义(P<0.05或P<0.01).进行年龄分组后,两组在静息状态下术后SV、VT均减小,CO、VE、VO2手术前后差异有统计学意义(P<0.01);运动负荷状态下术后两组VO2均减少,但老年组VE减少明显(P<0.01).结论 肺切除术后静息状态时CO和VE分别通过HR和RR的增加得到补偿,保证了氧摄取量,而术后运动负荷状态下CO和VE的减少不能通过HR和RR得到代偿,老年组VO2降低主要是VE减少所致,而中青年组则是由CO减少所致.     

咪达唑仑和丙泊酚全身麻醉药物诱导对高龄患者心功能的影响

目的探讨咪达唑仑与丙泊酚全身麻醉药物诱导对高龄患者心功能的影响。方法将2009年8月—2012年10月期间在我院接受非心脏手术的156例高龄患者采用数字表法随机分为观察组(78例)与对照组(78例),前者接受咪达唑仑全身麻醉,后者接受丙泊酚全身麻醉。分别在麻醉诱导前(T0)、麻醉诱导插管前1 min(T1)、麻醉诱导插管后2 min(T2)、麻醉诱导插管后5 min(T3)、麻醉诱导插管后10 min(T4)等5个时间点监测患者的心率(HR)、每搏输出量(SV)、每分输出量(CO)、平均动脉压(MAP)、外周血管阻力(SVR)、峰值速度(VpK)、净射血时间百分比(ET%)等指标。结果两组患者T0时HR、SV、CO、MAP、SVR、VpK、ET%相比差异无统计学意义(P>0.05)。与对应的T0相比,两组患者在T1～T4时的HR、SV、CO、MAP、SVR、VpK均显著下降(P<0.05),ET%则显著升高(P<0.05)。观察组患者在T1～T4时的HR、SV、CO、MAP、SVR、VpK均显著高于对照组,ET%则显著低于对照组(P<0.05)。结论与丙泊酚相比,咪达唑仑更适用于高龄患者手术过程中的全身麻醉药物诱导。     

Cardiovascular drift is related to reduced maximal oxygen uptake during heat stress

INTRODUCTION/PURPOSE: This study investigated whether the progressive rise in heart rate (HR) and fall in stroke volume (SV) during prolonged, constant-rate, moderate-intensity exercise (cardiovascular drift, CVdrift) in a hot environment is associated with a reduction in VO(2max). METHODS: CVdrift was measured in nine male cyclists between 15 and 45 min of cycling at 60% VO(2max) in 35 degrees C that was immediately followed by measurement of VO(2max). VO(2max) also was measured after 15 min of cycling on a separate day, so that any change in VO(2max) between 15 and 45 min could be associated with the CVdrift that occurred during that time interval. This protocol was performed under one condition in which fluid was ingested and there was no significant body weight change (0.3 +/- 0.4%), and under another in which no fluid was ingested and dehydration occurred (2.5 +/- 1%, P < 0.05). RESULTS: Fluid ingestion did not affect CVdrift or change in VO(2max). A 12% increase in HR (151 +/- 9 vs 169 +/- 10 bpm, P < 0.05) and 16% decrease in SV (120 +/- 12 vs 101 +/- 10 mL.beat(-1), P < 0.05) between 15 and 45 min was accompanied by a 19% decrease in VO(2max) (4.4 +/- 0.6 vs 3.6 +/- 0.4 L.min(-1), P < 0.05) despite attainment of a higher maximal HR (P < 0.05) at 45 min (194 +/- 5 bpm) vs 15 min (191 +/- 5 bpm). Submaximal VO(2) increased only slightly over time, but VO(2max) increased from 63 +/- 5% at 15 min to 78 +/- 8% at 45 min (P < 0.05). CONCLUSION: We conclude CVdrift during 45 min of exercise in the heat is associated with decreased VO(2max) and increased relative metabolic intensity. The results support the validity of using changes in HR to reflect changes in relative metabolic intensity during prolonged exercise in a hot environment in which CVdrift occurs.     

Effect of endurance training on cardiovascular response to static exercise performed with untrained muscles

Eighteen male volunteers (20-23 years) were submitted to 13 weeks of training consisting of 30 min of exercise (at 50%-75% VO2max) on a bicycle ergometer, performed three times a week. Every 4 weeks the heart rate (HR), blood pressure (BP), and systolic time interval (STI) responses to the static handgrip (at 30% MVC) were examined. Before and after 13 weeks of training echocardiograms were recorded in seven subjects at rest and during the handgrip. Significant decreases in HR and BP responses to static exercise were found already after 4 weeks of training. Resting STI and left ventricular dimensions were not affected by training, but during the static exercise the pre-ejection period (PEP) and isovolumic contraction time interval (ICT) at the corresponding HR were significantly shortened after 8 weeks of training. The values of echocardiographic indices of left ventricular function obtained during exercise after training did not differ significantly from those found before training. It is concluded that endurance training of moderate intensity improves cardiac function during static exercise performed with untrained muscles.     

Acute cardiovascular responses to multiple sets of high-velocity resistance exercise in healthy adults

The aim of this study is examining the effects of multiple sets of high-velocity resistance exercise (HVRE) on cardiovascular responses. Fifteen healthy adult men participated in two experimental sessions: one comprised three sets of resistance exercise performed against high-intensity resistance exercise (HIRE) at low velocity and the other three sets of HVRE performed against reduced load at high velocity. Blood pressure (BP), heart rate (HR), stroke volume (SV) and cardiac output (CO) during both sessions were evaluated using impedance electrocardiography. The increases in BP, HR and CO were significantly lowered during HVRE compared with HIRE (p < 0.05). In contrast, there was no significant difference in SV between sessions (p > 0.05). This study suggested that the increases in BP and CO during HVRE were lower than those during HIRE although HVRE required performing fast movement. HVRE might be applied to patients for whom HIRE is contraindicated because of cardiovascular diseases.     

Adaptation to a standardized training program and changes in fitness in a large, heterogeneous population: the HERITAGE Family Study

PURPOSE: This paper describes the variations in response to a standardized, computer-controlled training program. METHODS: Steady-state heart rate (HR) and oxygen intake (VO2) of 614 healthy, sedentary men and women aged 16-65 yr were measured during three cycle ergometer exercise tests. The HR associated with 55, 65, 70, and 75% of each subject's pretraining VO2max was used to prescribe exercise intensity. Subjects exercised three times a week, beginning at a HR associated with 55% VO2max for 30 min. Duration and intensity was gradually increased over 20 wk of training. The duration and HR of each training session were controlled by a computer. RESULTS: Using the linear relationship between HR, VO2 and power output (PO), PO were predicted for each of 60 training sessions at the respective programmed HR. The average ratio of the actual training HR to programmed HR was 0.99. It was hypothesized that participants whose actual training PO exceeded their predicted PO would improve VO2max more than those whose actual PO was less than their predicted PO. Using the ratio of actual/predicted PO determined after the training was over, participants were arbitrarily assigned to three groups: 128 participants had low (LO) ratios (0.65-0.84), 408 had average (AV) ratios (0.85-1.14), and 78 had high (HI) ratios (1.15-1.34). Secondary analysis showed that the training program significantly increased mean VO2max of all three groups. Those who had a smaller increase in training PO (LO) had significantly less increase in VO2max than those with larger increases in PO (HI). CONCLUSION: People who exercise at a HR associated with the same %VO2max can vary substantially in their training PO, in their rate of increase in PO over a 20-wk training program, and in improvement of their VO2max.     

Heart rate recovery from submaximal exercise in boys and girls

PURPOSE: To examine the changes in heart rate (HR) after two different submaximal exercise bouts in boys and girls. METHODS: Eleven boys (10.5 +/- 1.0 yr) and 10 girls (10.8 +/- 0.7 yr) participated in this study. Each child completed an initial graded exercise test to determine peak VO2. On subsequent and separate days, a 5-min submaximal exercise bout on a cycle ergometer was performed. One bout was conducted at 70 W, and the other bout corresponded to an intensity of 85-90% of peak VO2. VO2 and HR were measured during and after (1 min and 3 min). HR recovery responses from each submaximal exercise bout were analyzed using a group by time ANOVA, and Pearson-product correlations were determined between resting HR, peak VO2, and postexercise HR responses. RESULTS: HR in the boys was lower at the end of exercise and the first minute of recovery versus girls but not at the 3rd min of recovery. There were no differences in HR recovery after the relative exercise bout. Resting HR was significantly correlated with postexercise HR from both bouts (r = 0.52-0.69), whereas peak VO2 did not correlate to postexercise HR. ANCOVA using resting HR as the covariate eliminated the gender different noted with the recovery from the 70-W bout. CONCLUSIONS: In summary, postexercise HR responses differed between boys and girls when submaximal exercise was performed at an absolute work rate. When exercise was performed at a relative intensity, HR recovery responses were similar between the two groups. Resting HR appears to account for variations in postexercise HR better than peak VO2.