Strength training and hemodynamic responses to exercise

Sixty-two older adults (68.4±6 years) were randomized into a control group (n=16), low-intensity exercise group (n=22, LEX; 50% 1-repetition maximum; 13 repetitions per exercise), or a high-intensity exercise group (n=24, HEX; 80% 1-repetition maximum; eight repetitions per exercise) group. Subjects trained for 24 weeks, performing 1 set for each of 13 exercises. Subjects performed a graded exercise test (GXT) at baseline and after 24 weeks of strength training. Heart rate, systolic, and diastolic blood pressures were measured at rest, during the GXT and 1, 3, and 5-min post-GXT. Mean arterial pressure was also calculated. Post-training, time to peak systolic and diastolic blood pressures and heart rate was increased in the LEX and HEX groups by 22.9% and 44.5%, respectively (p<0.05). Diastolic blood pressure, heart rate, and mean arterial pressure during the GXT were significantly decreased (p<0.05) in the HEX group following training. Post-GXT heart rate was lower in the HEX and LEX groups compared to control (p<0.05) indicating a more rapid recovery. Resistance exercise prolongs the onset of peak cardiovascular responses, decreases the cardiovascular response to exertion, and improves recovery from maximal exertion.     

Growth hormone responses to repeated bouts of aerobic exercise with different recovery intervals in cyclists

To characterise the specific GH responses to repeated bouts of standardised aerobic exercise in amateur competitive cyclists, 6 volunteers (mean age +/- SE: 28.7 +/- 2.3 yr, range: 18-35 yr) performed two consecutive 30-min cycling sessions at 80% of individual maximal oxygen uptake on three occasions with different time interval between bouts: 2 h (EXP A), 4 h (EXP B) and 6 h (EXP C). Serum GH concentration was determined in blood samples collected at 15-min intervals during exercise and following 1 h of recovery. In EXP A and EXP B, peak GH concentration in response to the second bout was significantly lower (p < 0.01) than that of the first bout, but in EXP C no difference was detected between bouts. Similarly, the average integrated GH concentration (AUC), determined during the exercise period and in the following 1 h of recovery in the course of the second bout, was significantly lower than that observed during the first bout only in EXP A (p < 0.05) and EXP B (p < 0.01) and not in EXP C, so that the second bout AUC of EXP C was significantly higher than that of EXP A (p < 0.01) and EXP B (p < 0.01). It was concluded that GH responses to subsequent bouts of aerobic exercise are dependent on the time interval between the exercise sessions.     

Cardiorespiratory responses to exercise training after orthotopic cardiac transplantation

We have tested the feasibility and effectiveness of a 2 year (average 16 +/- 7 months) walk/jog exercise program on 36 male orthotopic cardiac transplant patients (21 to 57 years old) seen initially 2 to 23 months after surgery. Comparison of initial exercise test results with those in 45 age-matched normal men showed the patients to have a lesser lean body mass (56 +/- 7 vs 63 +/- 8 kg, p less than .001), with a higher resting heart rate (104 +/- 12 vs 77 +/- 14 beats/min, p less than .001) and systolic (138 +/- 16 vs 129 +/- 17 mm Hg, p less than .001) and diastolic (95 +/- 14 vs 84 +/- 10 mm Hg, p less than .001) blood pressures. Peak power output was less than normal (101 +/- 27 vs 219 +/- 41 W, p less than .001), as was peak heart rate (136 +/- 15 vs 176 +/- 13 beats/min, p less than .001), peak oxygen intake (VO2max) (22 +/- 5 vs 34 +/- 6 ml.kg.min-1, p less than .001), and absolute anaerobic threshold (1.18 +/- 0.40 vs 2.04 +/- 0.40 liters.min-1, p less than .001). Peak ventilatory equivalent was higher (48 +/- 9 vs 37 +/- 61.1-1, p less than .001). Cardiac output (Q), as estimated by the CO2 rebreathing method, was slightly above normal at rest (p less than .01), but below normal at two submaximal work rates. The group's average weekly training distance was 24 km, with eight highly compliant patients progressing to 32 km or more weekly. After training, lean tissue increased (+2.4 +/- 3.1 kg, p less than .001), and resting values were reduced for heart rate (-4 +/- 11 beats/min, p less than .05), systolic (-13 +/- 20 mm Hg, p less than .001), and diastolic (-9 +/- 17 mm Hg, p less than .001) blood pressures. There were significant reductions in submaximal values for minute ventilation (VE), ratings of perceived exertion, and diastolic blood pressure at equivalent workloads. Peak values increased for power output (+49 +/- 34 W, p less than .001), VO2max (+4.0 +/- 6.0 ml.kg.min-1, p less than .001), VE (+20 +/- 20 l.min-1, p less than .001), and heart rate (+13 +/- 17 beats/min, p less than .001), and decreased for diastolic blood pressure (-8 +/- 15 mm Hg, p less than .001).(ABSTRACT TRUNCATED AT 400 WORDS)     

Gender-, age-, body composition- and training workload-dependent differences of GH response to a discipline-specific training session in elite athletes: a study on the field

Ninety-nine Italian elite athletes (61 M, 38 F, mean age +/- SE: 24.1 +/- 0.6 yr, age range: 17-47 yr) of different disciplines volunteered to participate in this investigation. Basal GH concentrations were significantly higher (p<0.0001) in females (6.2 +/- 1.1 ng/ml) vs males (1.9 +/- 0.5 ng/ml). Basal GH values were negatively correlated with age and body mass index (BMI); no significant correlation was found between GH and IGF-I levels. Among female athletes, 8/38 had basal GH values higher than 10 ng/ml [2/8 athletes were taking oral contraceptives (OC)], while among males 6/61 had values higher than 5 ng/ml. In females, training sessions significantly increased (p<0.0001) basal GH concentrations (peak GH: 18.5 +/- 1.9 ng/ml), while in males GH responses were lower than in females (11.8 +/- 1.4 ng/ml, vs F: p<0.005). Six out of 38 female and 6/61 male athletes were considered GH hypo-responders (i.e. negative difference between peak GH and basal GH values), the large majority of them being subjects with elevated basal GH concentrations. In responsive athletes, peak GH values occurred immediately at the end of the training session both in males and in females; GH concentrations rapidly declined during recovery. No significant correlations were found between peak GH and age, body weight and BMI in either gender. GH responses were directly related (p<0.001) to the intensity of the workload during the sessions. In conclusion, the present study demonstrates that: 1) some elite athletes had increased GH concentrations before training, which were however associated with normal IGF-I levels; 2) GH peaks after a discipline-specific training session were significantly higher in females than in males performing the same discipline, gender-related differences disappearing when post-exercise total GH outputs (area under the curve) were compared; 3) peak GH values were directly correlated with training workload; 4) GH concentrations rapidly declined during recovery, values at the end of the post-training GH sampling being generally lower than those found in basal condition.     

Physical responses to different modes of interval exercise in patients with chronic heart failure--application to exercise training

METHOD: In exercise training with chronic heart failure patients, workingmuscles should be stressed with high intensity stimuli withoutcausing cardiac overstraining. This is possible using intervalmethod exercise. In this study, three interval exercise modeswith different ratios of work/recovery phases (30/60 s, 15/60s and 10/60 s) and different work rates were compared duringcycle ergometer exercise in heart failure patients. Work ratefor the three interval modes was 50% (30/60 s), 70% (15/60 s)and 80% (10/60 s) of the maximum achieved during a steep ramptest (increments of 25 w/l0s) corresponding to 71, 98 and 111watts on average. Metabolic and cardiac responses to the threeinterval exercises were then examined including catecholaminelevels and perceived exertion. Parameters measured during intervalexercise were compared with an intensity level of 75% peak VO₂,determined during an ordinary ramp exercise test (incrementsof l2·5 W. min^–1). RESULTS: () (1) In all three interval modes, VO₂, ventilation and lactate did not increase significantlyduring the course of exercise. Mean values during the last workphase were between 754 ± 30 and 803 ± 46 ml. min^–1for VO₂, between 26 ± 3 and 28 ± 11. min^–1for ventilation and between 1·24 ±0·14and l·29 ± 0·10 mmol.1^–1 for lactate.(2) In mode 10/60 s, heart rate and systolic blood pressureincreased significantly (82 ± 485 ± 4 beats. min^–1;124 ± 5134 ± 5 mmHg; P<0·05 each), whilein mode 15/60 s catecholamines increased significantly (norepinephrine0·804 ± 0·0891·135 ± 0·094nmol. 1^–1; P<0·008; epinephrine 0·136± 0·012 0 193 ± 0·019 nmol. 1^–1;P<0·005). (3) In all three modes, rating of leg fatigueand dyspnoea increased significantly during exercise but remainedwithin the range of values considered ‘very light to fairlylight’ on the Borg scale. (4) Compared to an intensitylevel of 75% peak VO₂, work rate durrng interval work phaseswas between 143 and 221%, while cardiac stress (rate-pressureproduct) was significantly lower (83–88%). CONCLUSION: All three interval modes resulted in physical response in anacceptable range of values, and thus can be recommended.     

Relationships between adipose tissue and cytokine responses to a randomized controlled exercise training intervention

Adipose-derived cytokines play a prominent role in mediating the metabolic consequences of obesity and excess body fat. Given this, we hypothesized that alterations in adipose tissue stores incurred with exercise training would be reflected in changes in systemic cytokine concentrations. The Studies of Targeted Risk Reduction Intervention through Defined Exercise, where pronounced changes in adipose tissue stores were observed in the absence of significant changes in dietary intake, provided an ideal setting in which to test this hypothesis. Participants were randomized to 6 months of inactivity or one of 3 types of aerobic exercise training regimens: low-amount-moderate-intensity, low-amount-vigorous-intensity, and high-amount-vigorous-intensity. Plasma samples were collected at baseline and 2 weeks after cessation of 6 months of exercise training or inactivity. In 189 participants, concentrations of 17 cytokines were measured using Bio-Plex Cytokine Assays (Bio-Rad, Hercules, CA); 10 additional cytokines were measured in 60 of these subjects. Of all cytokines tested, the only concentration changes that approached statistical significance were those for granulocyte monocyte-colony stimulating factor and vascular endothelial growth factor, which appeared to increase with training in the low-amount-high-intensity group only (P < .05 for both cytokines). No response to exercise training was noted for any additional cytokine in any of the groups. No relationships were observed between changes in cytokine concentrations and changes in fat mass or other measures of body habitus. In contradiction to our hypothesis, despite significant alterations in body composition, exercise training produced limited cytokine responses.     

Effects of exercise training on abnormal ventilatory responses to exercise in patients with chronic heart failure

Patients with chronic heart failure frequently report shortness of breath during daily activities as their primary symptom. In recent years, many efforts have been made by researchers to explain the mechanisms that underlie the characteristic heightened ventilatory response to activity in patients with chronic heart failure. The degree to which the ventilatory response to exercise is heightened parallels the severity of the disease, and measuring the ventilatory gas exchange response to exercise can help quantify the patient's response to therapy. Prior to the 1990s, patients with chronic heart failure were generally discouraged from participating in programs of exercise training. However, in the last decade, studies have demonstrated that exercise training is quite safe for these patients, and a multitude of benefits have been reported. Among the benefits of training are improvements in the abnormal ventilatory response to exercise. Although many mechanisms could potentially explain this response, it appears most likely that this improvement after training is due to a reduction in lactate accumulation and an attenuation of the heightened muscle receptor reflex response that occurs in chronic heart failure. This article reviews the mechanisms of dyspnea in chronic heart failure, along with recent studies assessing the effects of training on abnormal ventilatory responses to exercise in these patients. (c)2000 by CHF, Inc.     

Plasma and urinary GH following a standardized exercise protocol to assess GH production in short children

Plasma and urinary GH responses following acute physical exercise were evaluated in 19 short-statured children (12 males, 7 females, median age: 11.4 yr, age range: 6.1-14.5 yr, Tanner stage I-III, height < or = 3rd centile for age; 7 with familial short stature, FSS; 8 with constitutional growth delay, CGD; 4 with GH deficiency, GHD) and 7 normally growing, age- and sex-matched control children (4 males, 3 females, median age 11.0 yr, range: 7.2-13.1 yr, Tanner stage I-III). All patients and controls underwent a standardized exercise protocol (consisting of jogging up and down a corridor for 15 min, strongly encouraged to produce the maximum possible effort, corresponding to 70-80% of the maximal heart rate) after an overnight fasting. Samples for plasma GH determinations were drawn at 0 time (baseline), at 20 min (5 min after the end of exercise) and at 35 min (after 20 min of rest); urine samples were collected before (0 time) and at 40, 80 and 120 min after exercise. The distance covered by children with GHD during the test was significantly lower (p<0.05) than in the other groups of patients and controls. No differences in the pattern of plasma GH responses after physical exercise were found between children with FSS, CGD and healthy controls, the maximum percent increase (vs baseline) being evident at 20 min (median, FSS: +1125%; CGD: +1271%; controls: +571%). Children with GHD showed a smaller percent increase (+94%) of plasma GH, significantly lower (p<0.01) than those recorded in the other groups. A significant percent increase (p<0.01) of baseline urinary GH following exercise was found in children with FSS (median: +34%), CGD (+18%) and controls (+44%). Children with FSS and CGD showed a gradual increase of urinary GH, reaching the maximum at 80 min, while healthy controls had a more evident and precocious increase (maximum at 40 min). Urinary median GH levels did not change following physical exercise in children with GHD (-5%, not significant). A significant correlation was found between the maximal percent increase (vs baseline) of plasma and urinary GH following physical exercise (r=0.7, p<0.001). In conclusion, our results show that: 1) plasma and urinary GH responses (as well as the distance covered and the number of steps, i.e. the physical performance) to a standardized exercise protocol are similar in children with FSS, CGD and in normal-statured controls, being unable to differentiate among the "normal variants" of growth; 2) children with GHD, unable to accomplish the same performance of the other three groups, show significantly reduced plasma and urinary GH responses following physical exercise. Although the determination of GH responses to pharmacological stimuli remains the definitive tool for the diagnosis of GHD, these preliminary results seem to suggest a potential role of urinary (and plasma) GH response to a standardized exercise protocol as a safe, acceptable first screening test for GH sufficiency also in children, as previously reported in adults.     

Importance of exercise training session duration in the rehabilitation of coronary artery disease patients

BACKGROUND: In cardiac rehabilitation, 40-60-min exercise training sessions are advised. However, because of the increasing coronary artery disease (CAD) prevalence and higher workload for cardiac rehabilitation centres, it remains unclear whether 40-min exercise training sessions are equally effective as 60-min exercise training sessions. DESIGN: Prospective randomized clinical trial. METHODS: One hundred and thirty-four CAD patients were included in a 7-week rehabilitation programme. All patients exercised 3 days per week, at a heart rate corresponding to 65% of baseline peak oxygen uptake (VO2peak). Patients were randomized in two groups: 40 versus 60-min exercise training sessions. Changes of body anthropometrics, resting haemodynamics, exercise capacity and ventilatory threshold, blood plasma lipid profile and C-reactive protein level were assessed. RESULTS: As a result of rehabilitation, exercise capacity, ventilatory threshold, and blood plasma lipid profile improved significantly in the total population (P<0.05), without differences between subgroups (P>0.05). Body weight and waist circumference decreased significantly in total population (P<0.01), but with a greater magnitude in the 40 versus 60-min exercise session group (P<0.05). CONCLUSIONS: In the early rehabilitation of CAD patients, 40-min exercise training sessions seem to be at least as effective for improving body anthropometrics, blood plasma lipid profile and exercise capacity, as compared with 60-min exercise training sessions.     

Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes

BackgroundLow-carbohydrate diets have recently grown in popularity among endurance athletes, yet little is known about the long-term (> 4 wk) performance implications of consuming a low-carbohydrate high fat ketogenic diet (LCKD) in well-trained athletes.MethodsTwenty male endurance-trained athletes (age 33 ± 11 y, body mass 80 ± 11 kg; BMI 24.7 ± 3.1 kg/m²) who habitually consumed a carbohydrate-based diet, self-selected into a high-carbohydrate (HC) group (n = 11, %carbohydrate:protein:fat = 65:14:20), or a LCKD group (n = 9, 6:17:77). Both groups performed the same training intervention (endurance, strength and high intensity interval training (HIIT)). Prior to and following successful completion of 12-weeks of diet and training, participants had their body composition assessed, and completed a 100 km time trial (TT), six second (SS) sprint, and a critical power test (CPT). During post-intervention testing the HC group consumed 30–60 g/h carbohydrate, whereas the LCKD group consumed water, and electrolytes.ResultsThe LCKD group experienced a significantly greater decrease in body mass (HC − 0.8 kg, LCKD − 5.9 kg; P = 0.006, effect size (ES): 0.338) and percentage body fat percentage (HC − 0.7%, LCKD − 5.2%; P = 0.008, ES: 0.346). Fasting serum beta-hydroxybutyrate (βHB) significantly increased from 0.1 at baseline to 0.5 mmol/L in the LCKD group (P = 0.011, ES: 0.403) in week 12. There was no significant change in performance of the 100 km TT between groups (HC − 1.13 min·s, LCKD − 4.07 min·s, P = 0.057, ES: 0.196). SS sprint peak power increased by 0.8 watts per kilogram bodyweight (w/kg) in the LCKD group, versus a − 0.1 w/kg reduction in the HC group (P = 0.025, ES: 0.263). CPT peak power decreased by − 0.7 w/kg in the HC group, and increased by 1.4 w/kg in the LCKD group (P = 0.047, ES: 0.212). Fat oxidation in the LCKD group was significantly greater throughout the 100 km TT.ConclusionsCompared to a HC comparison group, a 12-week period of keto-adaptation and exercise training, enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.     

Growth responses to patterned GH delivery

We have investigated the effects of different patterns of administration of recombinant human growth hormone (rhGH) on weight gain, organ growth, serum GH binding protein (GHBP) and insulin-like growth factor-l (IGF-1) levels in a series of studies using hypophysectomized (Hx) or GH-deficient dwarf (dw/dw) rats. Animals were given rhGH either by subcutaneous (s.c.) injections (1 or 2 per day) or s.c. infusions and rhlGF-1 (2 mg/kg/day) by s.c. infusion. In Hx rats, all rhGH regimes increased body weight, tibial epiphyseal plate width, and organ weights in a dose-related manner. Dwarf rats showed a smaller growth response to rhGH than Hx rats, whereas rhGH induced greater elevations in serum GHBP in drarf rats. Growth responses depended on the pattern of rhGH administration (twice daily injections > continuous infusions > daily injections). The shape of the body growth curves also differed; rhGH injections increased weight gain linearly, whereas infusions gave an initial rapid weight gain which slowed with time (a curvilinear response). For both regimens, tibial epiphyseal plate width increased linearly with rhGH dose but infusions were 5-fold more potent than daily injections. Spleen and thymus weights were markedly increased by rhGH and were also affected by the pattern of GH exposure. At 5 mg rhGH/kg/day, thymus weights were 390±35 mg for injectionsvs. 613 ± 34 mg for infusions (P<0.001) compared with 248 ± 16 mg in vehicle-treated Hx controls. Infusions of rhlGF-1 also stimulated specific organ growth but caused less weight gain. RhlGF-1 additively increased the weight gain caused by rhGH injections but not by rhGH infusions. Circulating IGF-1 and GHBP levels were increased in a dose-dependent manner by rhGH infusion, whereas daily injections were ineffective. Thus, differential organ growth could be related to the higher serum IGF-1 concentrations induced by continuous rhGH administration. These studies show that whole body growth is best maintained by intermittent rhGH exposure, whereas, paradoxically, differential organ growth is most pronounced with continuous rhGH administration.     

DHEA, DHEA-S and cortisol responses to acute exercise in older adults in relation to exercise training status and sex

The aim of the present study was to investigate resting measures of dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEA-S) and cortisol, and the response and recovery of these hormones to acute exercise, in male and female older adults of different exercise training status. Participants were 49 community-dwelling older adults (23 females) aged between 60 and 77 years who were either sedentary (n = 14), moderately active (n = 14) or endurance trained (n = 21). Participants undertook an acute bout of exercise in the form of an incremental submaximal treadmill test. The exercise lasted on average 23 min 49 s (SD = 2 min 8 s) and participants reached 76.5% (SD = 5.44) of the predicted maximal heart rate. Blood samples were collected prior to exercise, immediately, and 1 h post-exercise. DHEA levels significantly increased immediately post-exercise; however, DHEA-S levels only significantly increased in females. Cortisol significantly decreased immediately post-exercise and 1 h post-exercise compared to pre-exercise. There were no significant differences in resting hormone levels or hormonal responses to exercise between training status groups. The findings suggest that exercise can stimulate DHEA production in older adults and that hormonal responses to exercise differ between male and female older adults.     

Blood lipid responses to plant stanol ester supplementation and aerobic exercise training

The purpose of this study was to determine the independent and combined effects of plant stanol ester (PSE) margarine and aerobic exercise on blood lipid concentrations and related intravascular enzymes in 26 healthy sedentary, middle-aged men and postmenopausal women (age, 53 +/- 8 years; body mass index, 27 +/- 1.0, % fat, 28.5 +/- 2). In a stratified double-blind manner, participants were randomly assigned to either a PSE (n = 17) or a placebo (CON, n = 9) margarine group. Participants supplemented their daily diets with 42 g of margarine spread (PSE = 3 g; CON, PSE = 0 g, of approximately equal energy content) for 9 weeks. During the last 4 weeks of margarine supplementation (MS), participants expended 400 kcal on a treadmill 5 d/wk at 65% of VO(2) reserve (2000 kcal/wk). Fasting blood samples were obtained before initiating and after 4 weeks of MS and after exercise training. All blood samples were analyzed for total cholesterol, low-density lipoprotein cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), hepatic lipase, lipoprotein lipase, and cholesterol ester transfer protein activities. Total cholesterol (-10%), low-density lipoprotein cholesterol (-13%), and triglyceride (-18%) concentrations decreased after 4 weeks of MS in the PSE group, but not in the CON group (P < .05 for all). Four weeks of aerobic exercise increased HDL-C by 21% in the CON group (P < .05) and by 4% in the PSE group (P > .05). Total cholesterol-HDL-C ratio decreased significantly (P < .05) in the PSE group, but not in the CON group. No other significant alterations were observed with either PSE or exercise. Our findings suggest that PSE is effective in reducing blood cholesterol concentrations and that exercise can increase HDL-C in middle-aged men and postmenopausal women. Our findings also suggest that PSE supplementation may attenuate the exercise-induced increase in HDL-C.     

Cardiac contributions to exercise training responses in patients with chronic heart failure: a strain imaging study

The improvement of exercise capacity due to exercise training in heart failure has been associated with peripheral adaptation, but the contribution of cardiac responses is less clear. We sought the extent to which the improvement of functional capacity in patients undergoing exercise training for heart failure was related to myocardial performance. Thirty-seven patients (35 men, age 64 +/- 11) with symptomatic heart failure and left ventricular ejection fraction < or = 35% (29 +/- 9%) were studied during a 16-week exercise training program. LV function was assessed by resting and exercise 2D-echocardiography, tissue Doppler derived myocardial strain, and strain rate. Peak oxygen consumption (VO2) and LV function were measured at baseline and follow-up, and the contribution of LV function at baseline and its response to training to the change of each parameter was sought. Baseline peak VO2 (12.4 +/- 4.6) increased by 9% at 8 weeks (13.5 +/- 4.2, P = 0.26), and by 21% at 16 weeks (15.0 +/- 4.9, P < 0.001). Although there were no overall changes in myocardial parameters in this study, change in peak VO2 at 16 weeks was significantly correlated with baseline strain (r = 0.51, P = 0.003) and the improvement of strain at 8 weeks (r = 0.44, P = 0.01), independent of baseline functional capacity and clinical variables. Thus, change in peak VO2 following 16 weeks exercise training is related to myocardial function at baseline.