Skeletal muscle pathology in endurance athletes with acquired training intolerance

Background: It is well established that prolonged, exhaustive endurance exercise is capable of inducing skeletal muscle damage and temporary impairment of muscle function. Although skeletal muscle has a remarkable capacity for repair and adaptation, this may be limited, ultimately resulting in an accumulation of chronic skeletal muscle pathology. Case studies have alluded to an association between long term, high volume endurance training and racing, acquired training intolerance, and chronic skeletal muscle pathology.

Objective: To systematically compare the skeletal muscle structural and ultrastructural status of endurance athletes with acquired training intolerance (ATI group) with asymptomatic endurance athletes matched for age and years of endurance training (CON group).

Methods: Histological and electron microscopic analyses were carried out on a biopsy sample of the vastus lateralis from 18 ATI and 17 CON endurance athletes. The presence of structural and ultrastructural disruptions was compared between the two groups of athletes.

Results: Significantly more athletes in the ATI group than in the CON group presented with fibre size variation (15 v 6; p = 0.006), internal nuclei (9 v 2; p = 0.03), and z disc streaming (6 v 0; p = 0.02).

Conclusions: There is an association between increased skeletal muscle disruptions and acquired training intolerance in endurance athletes. Further studies are required to determine the nature of this association and the possible mechanisms involved.

     

Depression and chronic fatigue in athletes.

For the most part, the competitive athlete is a well-adjusted individual who demonstrates considerable vigor and well-being, as well as less depression, anxiety, and fatigue than nonathletic counterparts. The well-trained athlete, however, may also have a personality that is somewhat rigid, strongly goal oriented, and perfectionist. It is not unrealistic to expect that when confronted with diminished performance or success, such an athlete may be compelled to drive himself or herself harder to succeed. Such behavior typically leads to the phenomenon of overtraining, which can express itself in the form of chronic fatigue and depression. There are a number of other organic causes of chronic fatigue and depression, however, which must be excluded by careful evaluation and appropriate diagnostic testing. Although the evaluation of the athlete who presents with chronic fatigue and depression can be somewhat complex, a diagnostic framework has been outlined here to assist the clinician in the assessment of an athlete who presents with such complaints.     

The changes in running performance and maximal oxygen uptake after long-term training in elite athletes

AIM: The relationship between VO2max (mL x kg(-1) x min(-1)) and running performance has been assessed in cross-sectional studies. Follow-up studies of the long-term effects of running training on the changes in performance and VO2max have not been undertaken. METHODS: Twenty-five male endurance-trained (MET) and 8 female endurance-trained (FET) athletes were tracked over 4 years. In each event the athletes were divided into Class A, including half the number of athletes with the best performances, and Class B. VO2max, examined at the end of the competitive season, and the best performance was chosen each year. RESULTS: After 3 years of training, in MET and FET athletes the performance improved by 1.77% and 0.69% (P<0.01 and P=0.579), respectively. In Class A runners, training resulted in non-significant increase in performance (-0.04%) (P=0.982) and in Class B runners, performance increased by 3.16% (P=0.001). In all groups VO(2max) remained essentially unchanged. Longitudinal changes in the VO2max were not related with the changes in running performance in any group. CONCLUSIONS: This study show than in older runners with more years of training, heavy training does not produce improvements in running performance neither changes in the VO2max. It is possible that these elite athletes have reached the plateau in their performance; although unlikely, some improvement in training techniques may happen and break the present limit. In younger runners with less years of training, heavy training produce improvements in running performance without changes in the VO2max. These athletes that had not attained his biological limits at the beginning of study improved the performance in competition and it is quite probable that this improvement be due to training. The changes in performance were not related to changes in VO2max. Consequently, another physiological or psychological variables must be studied by longitudinal form to explain the variability of performance in competition.     

Modelling the relationships between training, anxiety, and fatigue in elite athletes

This study investigated the effects of 40-week training on anxiety and perceived fatigue in four elite triathletes. Anxiety and perceived fatigue were self-reported by the subjects twice a week by the way of a specific questionnaire and were linked by a mathematical model to the training loads calculated from the exercise heart rate. A significant relationship (r=0.32; p<0.001) between the training loads and anxiety was identified using a two-component model: a first, negative (i.e., anxiety decreased) short-term (tau (1)=23 days) function and a second, positive long-term (tau (2)=59 days) function. The relationship between the training loads and perceived fatigue was significant (r=0.30; p<0.001), with one negative function (tau (1)=4 days). This mathematical model can potentially describe the relationships between training loads and anxiety or perceived fatigue and may improve both the adjustment of the duration of tapering and the early detection of staleness.     

Impact of reduced training on performance in endurance athletes.

Many endurance athletes and coaches fear a decrement in physical conditioning and performance if training is reduced for several days or longer. This is largely unfounded. Maximal exercise measures (VO2max, maximal heart rate, maximal speed or workload) are maintained for 10 to 28 days with reductions in weekly training volume of up to 70 to 80%. Blood measures (creatine kinase, haemoglobin, haematocrit, blood volume) change positively or are maintained with 5 to 21 days of reduced training, as are glycogen storage and muscle oxidative capacities. Submaximal or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that exercise frequency is reduced by no more than 20%. Athletic performance is improved or maintained with a 60 to 90% reduction in weekly training volume during a 6 to 21 day reduced training period, primarily due to an enhanced ability to exert muscular power. These findings suggest that endurance athletes should not refrain from reduced training prior to competition in an effort to improve performance, or for recovery from periods of intense training, injury, or staleness.     

Myocardial performance during maximal exercise in adolescents with anorexia nervosa

AIM: To examine cardiac responses and indicators of myocardial function during maximal exercise in adolescent girls with anorexia nervosa. METHODS: Eight girls (mean age 16.3+/-2.7 years) who satisfied criteria for the diagnosis of anorexia nervosa underwent maximal cycle testing. Cardiac stroke volume and peak aortic velocity and mean acceleration of flow (markers of myocardial contractility) were assessed using Doppler echocardiography and compared to healthy control subjects. Gas exchange variables were measured using open circuit spirometry techniques. RESULTS: Resting and maximal heart rates were less in the patients, and maximal oxygen uptake was significantly lower than controls. Maximal stroke index was greater in the patients than controls, with a normal pattern of response to progressive exercise. Peak aortic velocity and mean acceleration of flow were similar in the two groups when adjusted for heart rate. CONCLUSION: Findings of low heart rate and aerobic fitness previously described in patients with anorexia nervosa were confirmed. However, there was no evidence of abnormal myocardial performance during maximal exercise testing.     

Caffeine, maximal power output and fatigue.

The purpose of this investigation was to determine the effects of caffeine ingestion on maximal power output and fatigue during short term, high intensity exercise. Nine adult males performed 15 s maximal exercise bouts 60 min after ingestion of caffeine (7 mg.kg-1) or placebo. Exercise bouts were carried out on a modified cycle ergometer which allowed power output to be computed for each one-half pedal stroke via microcomputer. Peak power output under caffeine conditions was not significantly different from that obtained following placebo ingestion. Similarly, time to peak power, total work, power fatigue index and power fatigue rate did not differ significantly between caffeine and placebo conditions. These results suggest that caffeine ingestion does not increase one's maximal ability to generate power. Further, caffeine does not alter the rate or magnitude of fatigue during high intensity, dynamic exercise.     

The effect of exercise training on salivary immunoglobulin A and cortisol responses to maximal exercise.

The salivary immunoglobulin A (s-IgA) and cortisol responses to maximal exercise were examined in 24 adult males (X +/- SD; 22.1 +/- 3.0 yrs) before and after 10 weeks of run training. The subjects performed an incremental treadmill test to exhaustion and were randomly assigned to one of three groups: control (CON; n = 5), low intensity training (LO; n = 8), or high intensity training (HI; n = 11). Following the ten weeks of training, the subjects performed a second maximal treadmill test. Saliva samples were collected before, as well as immediately and 1 hr following each of the maximal treadmill tests and were analyzed for s-IgA and salivary cortisol. Maximal oxygen consumption (VO2max) increased significantly (p < 0.05) in the LO and HI groups but remained unchanged in the CON group. The s-IgA levels decreased significantly (p < 0.05) immediately post-exercise but returned to pre-exercise levels by one hour recovery. In addition, s-IgA and cortisol levels were not significantly (p > 0.05) correlated at any of the sampling times. These findings indicated that the s-IgA response to maximal exercise was unaffected by moderate (70% of VO2 max) to heavy (86% of VO2max) training (designed to develop cardiorespiratory fitness in healthy non-athletic adults) and independent of salivary cortisol.     

The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes

Background

The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear.

Aims

To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes.

Methods

Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO₂max) = 69.9 (7.9) (mlO₂/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O₂/65% N₂ (nitrox) or 35% O₂/65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3‐min intervals and at fatigue. Oxygen consumption (VO₂) and minute ventilation (V_E) were monitored continuously.

Results

Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO₂max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V_E (157 (24) and 163 (22) l/min). Between‐trial variability in peak power output was less than either VO₂max or maximal V_E.

Conclusion

Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and V_E with a concomitant reduction in VO₂ suggests an improved gas exchange and reduced O₂ cost of ventilation when breathing heliox.Sensations of respiratory discomfort are consciously monitored during exercise,¹ and, at higher workloads, sensations of dyspnoea are closely related to perceived exertion.^2,3 This evidence indicates a potential role for afferent sensory feedback of ventilatory exertion from the respiratory muscles in regulating maximum performance of exercise in humans.⁴ However, the role of perceived respiratory effort in the regulation of maximal performance of exercise remains unclear.⁵Perception of respiratory effort can be manipulated by altering the work of breathing. This effect has traditionally been achieved by either using a pressure‐assisted ventilation (PAV) device, in which a demand valve senses pressure changes at the nose and mouth and reactively assists the breathing,^6,7 or altering the properties of the inspired air so that it is less dense than normal air and therefore reduces the work required to move the air in and out of the lungs.^8,9,10A serious limitation to the PAV method is the potential to disrupt the normal breathing pattern of the subjects, as the novelty of the task requires subjects to “train” to breathe on the apparatus before undergoing testing.⁷ A further limitation is the delayed response time of the demand valve to pressure changes at the mouth.⁷ The result is that the PAV method can only be used effectively during steady‐state exercise and therefore cannot assess the role of ventilatory work or its associated sensations as a factor limiting progressive maximal exercise to exhaustion. Studies have produced mixed results regarding the effects of unloading the work of the respiratory muscles on exercise capacity possibly as a result of these limitations.^6,7By contrast, the performance benefits of breathing a less dense gas have produced more consistent results.^8,10,11,12 However, the increased breathing resistance imposed by the external gas delivery and collection systems used in these studies creates a potential difficulty in differentiating between the effects of the lighter gas on the anatomical respiratory tree and on the external respiratory tubing.^13,14 Furthermore, altering the properties of the inspired air may result in altered ventilatory dynamics. Although some researchers^15,16 have suggested that a less dense carrier gas might increase the alveolar–arterial partial pressure of oxygen (pO₂) gradient, thereby reducing arterial blood oxygen saturation, Nemery et al¹⁷ reported that the physical properties of the inspired gas do not affect ventilatory dynamics. Indeed, more recent studies have found that breathing a helium–oxygen mix improved arterial saturation.^9,18 Therefore, it seems that breathing a less dense gas during high‐intensity exercise may improve alveolar ventilation or the alveolar–arterial O₂ difference or both, thereby enhancing the oxygen content of arterial blood.^5,19To fully elucidate any potential role for the perceived effort of breathing in regulating maximal exercise, the confounding effects of breathing a gas less dense than air need to be considered. Conducting a trial on the performance of exercise in an environment in which “lighter” air is substituted for the ambient air will negate the need for external breathing apparatus, and hence the confounding effects of unloading the added respiratory resistance caused by such an apparatus. Furthermore, any ergogenic benefits derived from improved pulmonary dynamics can be minimised by increasing the fraction of oxygen in the inspired air.¹⁹Young et al²⁰ showed that physically active subjects are able to differentially assess feelings of effort pertaining to the respiratory and cardiovascular systems. Therefore, we aimed to investigate the perceptual and performance effects of breathing a low‐density, hyperoxic gas during a graded maximal exercise test to exhaustion in a young, physically fit population. We hypothesised that breathing a less dense gas would attenuate the perceived effort of breathing and improve incremental exercise time to exhaustion.     

Eryptosis and hemorheological responses to maximal exercise in athletes: Comparison between running and cycling

We compared the effects of cycling and running exercise on hemorheological and hematological properties, as well as eryptosis markers. Seven endurance‐trained subjects randomly performed a progressive and maximal exercise test on a cycle ergometer and a treadmill. Blood was sampled at rest and at the end of the exercise to analyze hematological and blood rheological parameters including hematocrit (Hct), red blood cell (RBC ) deformability, aggregation, and blood viscosity. Hemoglobin saturation (SpO2), blood lactate, and glucose levels were also monitored. Red blood cell oxidative stress, calcium content, and phosphatidylserine exposure were determined by flow cytometry to assess eryptosis level. Cycling exercise increased blood viscosity and RBC aggregation whereas it had no significant effect on RBC deformability. In contrast, blood viscosity remained unchanged and RBC deformability increased with running. The increase in Hct, lactate, and glucose concentrations and the loss of weight at the end of exercise were not different between running and cycling. Eryptosis markers were not affected by exercise. A significant drop in SpO2 was noted during running but not during cycling. Our study showed that a progressive and maximal exercise test conducted on a cycle ergometer increased blood viscosity while the same test conducted on a treadmill did not change this parameter because of different RBC rheological behavior between the 2 tests. We also demonstrated that a short maximal exercise does not alter RBC physiology in trained athletes. We suspect that exercise‐induced hypoxemia occurring during running could be at the origin of the RBC rheological behavior differences with cycling.     

Vigorous exercise training is not associated with prevalence of ventricular arrhythmias in elderly athletes

AIM: Physical activity, when vigorous, is not devoided of arrhythmic risk. Since the risk of developing arrhythmias increase as an otherwise healthy person ages, the question arises as to whether high intensity physical activity could be dangerous in the elderly person. The present study addressed the incidence of arrhythmias in elderly athletes in comparison to age-matched control subjects. METHODS: We studied 49 male athletes engaged in various sport disciplines, mean age 62.3+/-2.3 and 24 sedentary or moderately physically active healthy males, mean age 62.9+/-1.7 years (Controls). All subjects underwent 2-D, M-mode and Doppler echocardiographic examination, resting ECG and exercise stress test followed by 24-hour electrocardiographic monitoring. RESULTS: No pathological findings were detected in both experimental groups at echocardiographic examination. Exercise performance was greater in athletes than controls (206.9+/-5.2 vs 156.3+/-12 watt, p<0.01). During exercise test, no significant between-groups difference was detected in the incidence of ventricular arrhythmias, that is multiple premature ventricular contractions (MPVC), polymorphous premature ventricular contractions (PPVC) and repetitive premature ventricular contractions (RPVC). No subject featured horizontal or downsloping ST segment depression in both groups. At 24-hour electrocardiographic monitoring the incidence of the overall number of premature ventricular contractions was significantly greater in controls than athletes (87.0% vs 63.3%, p<0.05), whereas no significant difference were detected in the incidence of discrete ventricular arrhythmias between athletes (4.1% MPVC, 14.3% PPVC, 8.2% couplets) and controls (0.5% MPVC, 16.7% PPVC, 12.5% couplets). CONCLUSION: These finding indicate that in elderly, otherwise healthy, athletes vigorous training even to competition does not result in a greater incidence of ventricular arrhythmias, although caution should be made for a careful preparticipation evaluation.     

Glycaemic control, muscle glycogen and exercise performance in IDDM athletes on diets of varying carbohydrate content.

The aim of this study was to examine the effects of a high carbohydrate diet on glycaemic control, resting muscle glycogen levels and exercise performance in athletes with insulin dependent diabetes (IDDM). Seven trained (mean +/- S.D., VO2max 50.3 +/- 7.4 ml/kg/min) IDDM males consumed a high carbohydrate diet (HCD) or a normal mixed diet (NMD) for 3 week periods in a randomised crossover trial with a one week wash-out. Carbohydrate provided 59% or 50% of total energy intake, respectively, on the two diets. Fasting plasma lipids, mean blood glucose (over 96 h), fructosamine and muscle glycogen were measured and insulin use recorded. Exercise performance was evaluated by a 15 min time trial following a 50 min pre-loading block. Statistical significance was assessed using two tailed paired Student t-tests. Mean blood glucose was 10% higher on HCD than NMD (p = 0.005), fructosamine levels were 375 +/- 54 and 353 +/- 51 (mol/L on HCD and NMD, resp., p = 0.04) and daily insulin requirements were 15% higher on HCD than NMD (p = 0.02). Fasting blood lipids were similar on the two diets. Muscle glycogen was significantly lower on HCD than NMD (88.2 +/- 19.2 and 95.6 +/- 14.6 mmol/kg ww, respectively, p = 0.02). Exercise completed during the time trial was 6% less on HCD than on NMD (p = 0.007). An increased carbohydrate intake for three weeks, in IDDM athletes, is associated with a deterioration in glycaemic control, increased insulin requirements, decreased muscle glycogen and reduced exercise performance. These data do not support recommendations for IDDM athletes to consume a high carbohydrate diet, at least not when glycaemic control worsens upon following this advice, as was observed in this short-term study.     

Effect of oxygen breathing following submaximal and maximal exercise on recovery and performance.

To determine whether supplemental oxygen following exercise hastens recovery or enhances subsequent performance we evaluated its effectiveness in 13 male athletes. The exercise periods consisted of two 5-min submaximal efforts on a treadmill ergometer followed by a single bout to exhaustion. Intervals of exercise were separated by a 4-min recovery period during which the subject breathed either 1) room air, 2) 100% oxygen, or 3) 2 min of 100% oxygen followed by 2 min of room air on three nonconsecutive days. We found that breathing 100% oxygen produced no significant difference on the recovery kinetics of minute ventilation or heart rate, or improvement in subsequent performance as measured by duration of exercise (3.33 +/- 0.04 min, air vs 3.46 +/- 0.03, oxygen) and peak VO2 (59.9 +/- 2.2 ml.kg-1.min-1, air vs 54.5 +/- 2.2, oxygen). In addition, the perceived magnitude of exertion estimated by the Borg scale was no different during oxygen breathing. These findings offer no support for the use of supplemental oxygen in athletic events requiring short intervals of submaximal or maximal exertion.     

The effects of rear-wheel camber on maximal effort mobility performance in wheelchair athletes

This study examined the effect of rear-wheel camber on maximal effort wheelchair mobility performance. 14 highly trained wheelchair court sport athletes performed a battery of field tests in 4 standardised camber settings (15°, 18°, 20°, 24°) with performance analysed using a velocometer. 20 m sprint times reduced in 18° (5.89±0.47 s, P=0.011) and 20° camber (5.93±0.47 s, P=0.030) compared with 24° (6.05±0.45 s). Large effect sizes revealed that 18° camber enabled greater acceleration over the first 2 (r=0.53, 95% CI=0.004 to 0.239) and 3 (r=0.59, 95% CI=0.017 to 0.170) pushes compared with 24°. Linear mobility times significantly improved (P≤0.05) in 15° (16.08±0.84 s), 18° (16.06±0.97 s) and 20° (16.22±0.84 s) camber compared with 24° (16.62±1.10 s). Although no statistically significant main effect of camber was revealed, large effect sizes (r=0.72, 95% CI=0.066 to 0.250) demonstrated that 18° camber reduced times taken to perform the manoeuvrability drill compared with 15°. It was concluded that 18° camber was the best performing setting investigated given its superior performance for both linear and non-linear aspects of mobility, whereas 24° camber impaired linear performance. This was likely to be due to the greater drag forces experienced. Subsequently, athletes would be recommended to avoid 24° camber and young or inexperienced athletes in particular may benefit from selecting 18° as a starting point due to its favourable performance for all aspects of mobility performance in the current study.     

Influence of exercise training on physiological and performance changes with weight loss in men.

PURPOSE: The purpose of this study was to examine the physiological effects of a weight-loss dietary regimen with or without exercise. METHODS: Thirty-five overweight men were matched and randomly placed into either a control group (C; N = 6) or one of three dietary groups; a diet-only group (D; N = 8), a diet group that performed aerobic exercise three times per week (DE; N = 11); and a diet group that performed both aerobic and strength training three times per week (DES; N = 10). RESULTS: After 12 wk, D, DE, and DES demonstrated a similar and significant (P < or = 0.05) reduction in body mass (-9.64, -8.99, and -9.90 kg, respectively) with fat mass comprising 69, 78, and 97% of the total loss in body mass, respectively. The diet-only group also demonstrated a significant reduction in fat-free mass. Maximum strength, as determined by 1-RM testing in the bench press and squat exercise was significantly increased for DES in both the bench press (+19.6%) and squat exercise (+32.6%). Absolute peak O2 consumption was significantly elevated in DE (+24.8%) and DES (+15.4%). There were no differences in performance during a 30-s Wingate test for the DE and DES, whereas D demonstrated a significant decline in peak and mean power output. Resting metabolic rate (RMR) (kcal x d(-1)) was not significantly different for any of the groups except for the DE group. There were no significant changes in basal concentrations of serum glucose, BUN, cortisol, testosterone, and high density lipoprotein (HDL) cholesterol for any of the groups. Serum total cholesterol and low density lipoprotein (LDL) cholesterol were significantly decreased for all dietary groups. Serum triglycerides were significantly reduced for D and DES at week 6 and remained lower at week 12 for D, while triglycerides returned to baseline values for DES. CONCLUSIONS: These data indicate that a weight-loss dietary regimen in conjunction with aerobic and resistance exercise prevents the normal decline in fat-free mass and muscular power and augments body composition, maximal strength, and maximum oxygen consumption compared with weight-loss induced by diet alone.     

Physiological responses to incremental exercise in patients with chronic fatigue syndrome

PURPOSE: The purpose of this investigation was to characterize the physiological response profiles of patients with chronic fatigue syndrome (CFS), to an incremental exercise test, performed to the limit of tolerance. METHODS: Fifteen patients (12 women and three men) who fulfilled the case definition for chronic fatigue syndrome, and 15 healthy, sedentary, age- and sex-matched controls, performed an incremental progressive all-out treadmill test (cardiopulmonary exercise test). RESULTS: As a group, the CFS patients demonstrated significantly lower cardiovascular as well as ventilatory values at peak exercise, compared with the control group. At similar relative submaximal exercise levels (% peak VO(2)), the CFS patients portrayed response patterns (trending phenomenon) characterized, in most parameters, by similar intercepts, but either lower (VCO(2), HR, O(2pulse), V(E), V(T), PETCO(2)) or higher (B(f), V(E)/VCO(2)) trending kinetics in the CFS compared with the control group. It was found that the primary exercise-related physiological difference between the CFS and the control group was their significantly lower heart rate at any equal relative and at maximal work level. Assuming maximal effort by all (indicated by RER, PETCO(2), and subjective exhaustion), these results could indicate either cardiac or peripheral insufficiency embedded in the pathology of CFS patients. CONCLUSION: We conclude that indexes from cardiopulmonary exercise testing may be used as objective discriminatory indicators for evaluation of patients complaining of chronic fatigue syndrome.     

Effect of 6 d of exercise training on responses to maximal and sub-maximal exercise in middle-aged men

Nine sedentary men (53 +/- 3 yr) were studied before and after 6 d of endurance exercise training to determine the effects on maximal oxygen uptake (VO2max), and on the heart rate, blood pressure, and metabolic responses to a standard bout of steady-state sub-maximal exercise. The subjects exercised approximately 1 h.d-1 at about 68% of VO2max. The 6-d protocol elicited no improvement in VO2max (2.50 +/- 0.14 before vs 2.58 +/- 0.15 l.min-1 after training). Heart rates were significantly lower by 5 to 8 b.min-1, systolic blood pressures were reduced by 16 to 19 mm Hg, and blood lactate concentrations were 25 to 35% less at the same exercise intensities (60, 70, and 80% of VO2max) after 6 d of exercise. Rate pressure product was about 15% lower at the same exercise intensity after 6 d of training (P less than 0.05). The respiratory exchange ratio during submaximal exercise was 0.02 to 0.04 units lower (P less than 0.05; P less than 0.01) after 6 d of exercise, indicating a shift in substrate utilization favoring fat oxidation. These findings suggest that short-term endurance training can induce heart rate, blood pressure, and metabolic adaptations to sub-maximal exercise before there is a significant increase in VO2max in sedentary, middle-aged men who are capable of vigorous exercise.     

Rate and mechanism of maximal oxygen consumption decline with aging: implications for exercise training

Because of the influence of cardiorespiratory fitness on functional independence, quality of life, and cardiovascular disease and all-cause mortality, tremendous interest has been directed towards describing the age-related change in maximal oxygen consumption (VO(2max)). Current evidence supports a 10% per decade decline in VO(2max) in men and women regardless of activity level. High-intensity exercise may reduce this loss by up to 50% in young and middle-aged men, but not older men, if maintained long term. Middle-aged and older women do not appear to be able to reduce loss rates in VO(2max) to less than 10% per decade, which may be related to estrogen status. However, maintaining high-intensity training seems limited to approximately one decade at best and to a select few individuals. While the factors limiting the ability to maintain high-intensity training are not completely known, aging most likely plays a role as studies have demonstrated that training maintenance becomes more difficult with advancing age. Age-related loss of VO(2max) seems to occur in a non-linear fashion in association with declines in physical activity. In sedentary individuals, this non-linear decline generally occurs during the twenties and thirties whereas athletic individuals demonstrate a non-linear decline upon decreasing or ceasing training. Non-linear loss rates are also demonstrated in individuals over the age of 70 years. The decline in VO(2max) seems to be due to both central and peripheral adaptations, primarily reductions in maximal heart rate (HR(max)) and lean body mass (LBM). Exercise training does not influence declines in HR(max), while LBM can be maintained to some degree by exercise. Recommendations for exercise training should include aerobic activities utilising guidelines established by the American College of Sports Medicine for improving CV fitness and health, as well as strength training activities for enhancing LBM.     

Exercise and cognitive performance in chronic fatigue syndrome

PURPOSE: To determine the effect of submaximal steady-state exercise on cognitive performance in patients with chronic fatigue syndrome (CFS) alone, CFS with comorbid fibromyalgia FM (CFS + FM), and sedentary healthy controls (CON). METHODS: Twenty CFS-only patients, 19 CFS + FM, and 26 CON completed a battery of cognitive tests designed to assess speed of information processing, variability, and efficiency. Tests were performed at baseline, immediately before, and twice following 25 min of either cycle ergometry set at 40% of peak oxygen capacity or quiet rest. RESULTS: There were no group differences in average percentage of peak oxygen consumption during exercise (CFS = 45%; CFS + FM = 47%; Control = 43%: P = 0.2). There were no significant effects of acute exercise on cognitive performance for any group. At baseline, one-way ANOVA indicated that CFS patients displayed deficits in speed of processing, performance variability, and task efficiency during several cognitive tests compared with healthy controls. However, the CFS + FM patients were not different than controls. Repeated measures ANOVA indicated that across all tests (pre- and postexercise) CFS, but not CFS + FM, were significantly less consistent (F2,59 = 3.7, P = 0.03) and less efficient (F2,59 = 4.6, P = 0.01) than controls. CONCLUSION: CFS patients without comorbid FM exhibit subtle cognitive deficits in terms of speed, consistency, and efficiency that are not improved or exacerbated by light exercise. Importantly, our data suggest that CFS + FM patients do not exhibit cognitive deficits either pre- or postexercise. These results highlight the importance of disease heterogeneity in studies determining acute exercise and cognitive function in CFS.