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At least 811 records · Page 45Linked to original sources
PubMed2002

Effect of eccentric exercise on patients with chronic exertional compartment syndrome.

There are a number of similarities between chronic exertional compartment syndrome (CECS) and the effects of high force eccentric contractions in healthy controls. We hypothesised that CECS patients would be particularly susceptible to pain, fatigue and swelling after eccentric exercise. Ten CECS patients [aged 30.3 (8.0) years, mean (SD)], 7 males) and 14 healthy controls [aged 32.3 (9.0) years, 7 males] performed 40 maximal eccentric contractions of the anterior tibial muscles at an angular velocity of 90(o) s(-1). Maximal voluntary isometric contractions (MVC), force generated by electrical stimulation at 10 Hz and 50 Hz and muscle thickness (measured by real-time ultrasound scanning) were measured before exercise and for 10 min afterwards. Ratings of pain and tenderness were made before exercise, then 24 h and 48 h later. The two groups were comparable for initial isometric strength and muscle size. MVC force immediately after exercise fell to 90 (2.5)% [mean (SEM)] in patients and 86.5 (2.4)% in controls (P<0.0005 for both groups) and had not recovered after 10 min. Preferential loss of force at the low stimulation frequency occurred in both groups to a similar extent (20%, P<0.0005) and continued to decline over 10 min of recovery. There was no significant change in muscle thickness in either group. Only mild pain and tenderness were reported by the controls. The patients showed great individual variation but their mean pain scores were significantly higher during dorsiflexion and palpation (P<0.05) 24 h after exercise. After 48 h the patients reported more pain during dorsiflexion (P=0.005), plantarflexion (P<0.05) and palpation (P<0.05). These results suggest that some, but not all, CECS patients may be more susceptible to the pain associated with eccentric contractions that is thought to be the cause of damage and inflammation of connective tissue.

Adult↗
PubMed2003

Effect of push frequency and strategy variations on economy and perceived exertion during wheelchair propulsion.

Wheelchair locomotion is a cyclical activity and participants are free to select any push frequency-propulsion strategy combination that suits their needs at a given power output. The aim of the study was to examine the physiological effects of varying push frequency and strategy on pushing economy. Twelve male, able-bodied participants completed four, randomly assigned, 5-min bouts of submaximal exercise at 32 W on a wheelchair ergometer. Each bout of exercise combined two different push frequencies (40 and 70 push min(-1)), with one of two different push strategies [synchronous (SYN): both arms pushing together, and asynchronous: one arm applying force to the wheel at a time). Physiological measures included oxygen uptake ( VO(2)), heart rate (HR) and blood lactate [La](b )concentration. Differentiated ratings of perceived exertion (RPE) were also recorded (overall, local and central). Separate ANOVA were used for VO(2), HR, [La](b) and RPE as the dependent variables. Where significant differences were identified, a Bonferroni post hoc test was used. The main effect for push frequency by strategy was significant for VO(2) ( P<0.01). Scrutiny of the HR values showed that the SYN 40 condition was significantly less stressful than all other frequency-strategy combinations ( P<0.01). RPE data supported these findings although they were found to be non-significant. When looking at [La](b,) both of the main effects were also significant showing the concentration was lower on average when the push rate was 40 as opposed to 70 (1.65 vs 2.14 mmol l(-1); P<0.01). This study provides further evidence that a low push frequency provides the most economical form of wheelchair propulsion especially when combined with a SYN strategy.

Adult↗
PubMed2005

Changes of motor drive, cortical arousal and perceived exertion following prolonged cycling to exhaustion.

The aims of this study were to (1) quantify any central fatigue that occurs following prolonged dynamic exercise, i.e. reduced muscle force caused by impaired motor drive from the central nervous system and (2) determine whether decreased cortical arousal, assessed using critical flicker fusion threshold (CFF), occurs and is related to impaired exercise performance. Fifteen healthy men cycled at 70% VO2peak until exhaustion. The peak force of maximum voluntary isometric contractions (MVC) of the quadriceps muscle group was reduced by 30% at exhaustion. The voluntary activation ratio determined using superimposed tetanic stimulation fell from 0.99 to 0.86 at exhaustion. The central fatigue (%) at exhaustion was 33+/-12% (+/- SD) (assessed via the tetanus interpolation technique) and 54+/-32% (assessed via the relative decline of MVC and peak tetanic force) of the total fatigue. The MVC only partially recovered and central fatigue persisted at 30 min post-exercise. CFF increased from 39.2+/-2.3 to 41.8+/-3.5 Hz at exhaustion, but did not correlate with central fatigue. Every subject reached the highest rating of perceived exertion (RPE) at exhaustion of 20 on the Borg scale. The time to exhaustion was related to how quickly the RPE increased and to the ability to sustain exercise at very high RPE. These data suggest that with prolonged cycling: (1) there is considerable and a persistent form of central fatigue, (2) there is an increased level of cortical arousal, and (3) exhaustion is linked to very high subjective RPE.

Adult↗
PubMed2006

Seven days' around the clock exhaustive physical exertion combined with energy depletion and sleep deprivation primes circulating leukocytes.

Both exhaustive physical exertion and starvation have been reported to induce depression of immune function. The aim of the present study was to investigate the inflammatory environment and state of activation and mediator-producing potential of circulating leukocytes during prolonged physical activity with concomitant energy and sleep deprivation. Eight well-trained males were studied during 7 days of semi-continuous physical activity. Sleep was restricted to about 1 h/24 h, energy intake to 1.5- 3.0 MJ/24 h. Blood was drawn at 07.00 A.M.: on days 0, 2, 4, and 7. Plasma levels of inflammation markers were measured. The response of circulating leukocytes to lipopolysaccharide (LPS; 1 microg mL(-1)), and the effect of added hydrocortisone (10 and 100 nmol L(-1)), were measured in the supernatant after 3 h of incubation in an ex vivo whole blood model. Activation of leukocytes steadily increased as measured by plasma matrix metalloproteinase-9, tumour necrosis factor-alpha, interleukin-1beta, and interleukin-6. Inhibitors of systemic inflammation were either unaltered (tissue inhibitor of matrix metalloproteinase-1) or elevated (plasma interleukin-1 receptor antagonist). Cortisol levels increased on days 2 and 4, but thereafter reverted to baseline values. The leukocytes responded to LPS activation with increasing release of inflammatory cytokines throughout the study period. The anti-inflammatory potency of hydrocortisone decreased. Prolonged multifactorial stress thus activated circulating immune cells and primed them for an increased response to a subsequent microbial challenge.

Adult↗
PubMed2001

Is breath-hold time an objective index of exertional dyspnoea in humans?

Since dyspnoeic sensation (delta) increases progressively with work rate (WR) and the duration of a volitional breath-hold (tBH) shortens, we wished to explore whether tBH might correlate sufficiently closely with delta to provide a quantitative and descriptor-free index of respiratory sensation during dynamic exercise. Nine healthy males exercised on a cycle ergometer at a series of constant WRs, above and below the lactate threshold. Ventilatory and gas exchange variables were measured breath-by-breath. At each WR, breath-holds to the limit of tolerance were taken; delta was recorded (visual-analog scale) immediately prior to and throughout each breath-hold. During breath-holds, delta increased with time as a "break-away" monoexponential characteristic, reaching the maximum (100%) at the break-point. Despite end-tidal partial pressure of carbon dioxide at the break-point being higher and end-tidal partial pressure of oxygen being lower with increasing WR, the relationship between WR and tBH declined curvilinearly (i.e. with large falls in tBH occurring in the low WR range, but far smaller reductions at higher WRs). The tBH/minute ventilation relationship had a similar form. The relationship between pre-breath-hold delta and tBH was also complex: the large reductions in tBH in the low WR range were associated with only modest increases in pre-BH delta while, at higher WRs, the progressively smaller decrements in tBH were associated with progressively larger increases in delta. We therefore conclude that breath-hold duration is unlikely to provide a useful correlate of exertional dyspnoea during dynamic exercise. Furthermore, the relative prolongation of tBH at high WRs (accounting for the more-extreme levels of end-tidal gas tensions) may reflect the attention-diverting influence of the exercise per se.

Adult↗
PubMed2001

Reproducibility of blood lactate-anchored ratings of perceived exertion.

This study investigated the reproducibility of blood lactate-anchored ratings of perceived exertion (RPE) in seven women of average, and seven of above average cardiorespiratory fitness, [moderate and high maximal oxygen uptake (Mod VO2max and High VO2max, respectively)]. The subjects completed a series of four exercise tests, comprising a VO2max assessment and three O-grade, velocity-incremental, treadmill-running RPE estimation trials. The results revealed no significant between-group differences in RPE at the blood lactate concentration threshold (LT), and at reference levels of 2, 2.5 or 4 mmol x l(-1) (RPELT, RPE2, RPE2.5 and RPE4, respectively). The RPELT, RPE2, RPE2.5 and RPE4 were characterised by intra-class correlation coefficients of 0.97, 0.97, 0.97, 0.72 and 0.83, 0.96, 0.96, 0.90, in the High VO2max and Mod VO2max groups, respectively. The SEM% (95% confidence limits computed as a percentage of the group mean score) largely mirrored the trend in reliability with the highest values observed for RPELT in the Mod VO2max group and RPE4 in the High VO2max group. The Spearman-Brown prediction equation indicated that fixed blood lactate concentrations of 2, 2.5 and 4 mmol x l(-1) offer acceptable practical utility as potential perceptual anchor points for both groups, requiring one trial only to achieve a measurement error of less than +/- 6%.

Adult↗
PubMed1981

Regional coronary angiographic observations during cold stimulation in patient with exertional chest pain: comparison of diameter responses in normal and fixed stenotic vessels.

In 12 patients with exertional chest pain, coronary angiography was performed and quantitative measurements coronary artery (CA) diameters were made before and during cold stimulation (four normal CA patients and eight fixed CA stenosis patients). The left main CA; proximal, middle and distal anterior descending and circumflex segments; and small intramyocardial CAs (0.4 to 1.0 mm) usually showed only minimal and similar degree of vasoconstriction (average diameter reduction 6%) during cold stimulation in both normals and CA disease (CAD) patients. Magnitude of vasoconstriction differed among some CA segments measured; the left main CA segment (0 +/- 2%, mean +/- SD) usually did not change while distal segments (-10 +/- 10%) usually demonstrated greatest percentage vasoconstriction. Coronary stenoses and CAs filled by collaterals did not demonstrate increased magnitude of vasoconstriction compared to other CAs. Results of other CA segments were also similar comparing patients with and without CAD. The minimal degree of vasoconstriction observed in these CA segments does not appear to account for the large increase in coronary resistance reported during cold stimulation in CAD patients.

Cardiac Catheterization↗
PubMed1983

Hemodynamic effects of felodipine at rest and during exercise in exertional angina pectoris.

To examine the antianginal effects of felodipine, a new calcium antagonist, 8 patients with coronary artery disease and exertional angina pectoris were studied. Hemodynamic measurements were made at rest, during submaximal exercise and during angina-limited exercise before and 30 minutes after oral administration of 0.1 mg/kg of felodipine. Angina pectoris was always prevented after the drug was given and the exercise intensity was increased until recurrence of angina (5 patients) or exhaustion (3 patients). Hemodynamic data were also recorded at this higher exercise capacity. At rest and during submaximal exercise, felodipine increased heart rate and decreased arterial blood pressure and systemic vascular resistance. The prevention of angina pectoris was accompanied by lower mean pulmonary capillary wedge pressure, systemic vascular resistance and ST-segment depression; the pressure-rate product was unchanged. The 20% greater exercise capacity after felodipine was attended by a 20% increase in maximal cardiac output, a 17% increase in maximal heart rate and a 13% increase in maximal pressure-rate product; the maximal arterial blood pressure and ST-segment abnormalities were unchanged and the systemic vascular resistance was lower. The relation between ST-segment depression and the pressure-rate product during exercise was favorably influenced by felodipine. Thus, felodipine is an active antianginal drug; its major mechanism of action is to lower the systemic vascular resistance. The data also suggest that it improves coronary blood flow during exercise.

Aged↗
PubMed1988

Acute effects of felodipine in exertional angina pectoris.

To investigate the antianginal efficacy, duration of action and tolerability of 2 doses of the new calcium antagonist felodipine, 15 patients (14 men and 1 woman, mean age 62 years) with stable exertional angina pectoris and angiographically demonstrated coronary artery disease were randomly given felodipine, 5 and 10 mg, and placebo on 3 different days. A bicycle ergometer exercise test was performed 3 and 10 hours after dosing. In comparison with placebo, felodipine 5 and 10 mg significantly increased resting heart rate and decreased resting systolic and diastolic blood pressure 3 hours after administration (p less than 0.001). Ten hours after administration, only supine systolic blood pressure was still significantly lower (p less than 0.001). Anginal (time to mild chest pain) and ischemic (time to 1 mm ST depression) thresholds, as well as duration of exercise and total work at peak exercise, were higher in comparison with placebo at 3 and 10 hours (p less than 0.001). In comparison with the lower dose, 10 mg felodipine induced a decrease in supine (p less than 0.05) and sitting (p less than 0.01) systolic blood pressure at rest and an increase in total work to anginal threshold (p less than 0.01), as well as in total work and duration of exercise at peak exercise (p less than 0.05). These results suggest that a single administration of felodipine, 5 and 10 mg, may improve exercise capacity over a 10-hour period in patients with stable exercise-induced angina due to atherosclerotic heart disease.

Angina Pectoris↗
PubMed1986

Regional brain blood flow and O2 delivery during severe exertion in the pony.

Regional distribution of brain blood flow (radionuclide labelled 15 microns diameter microspheres) and O2 supply were studied in 11 healthy adult grade ponies at rest and during severe exercise (SE) performed on a treadmill (heart rate = 220 +/- 4 beats X min-1; VO2 = 126 +/- 9 ml X min-1 X kg-1). During SE, the mean aortic pressure increased to 169 +/- 4 mm Hg and the pHa, PaCO2 and PaO2 were 7.213 +/- 0.010, 30 +/- 1 mm Hg and 85 +/- 4 mm Hg, respectively. The hemoglobin concentration increased by 59.6% with SE. Whereas blood flow increased in the cerebellar gray matter (96%), pons (39.5%) and medulla (55.6%), in none of the other brain regions blood flow was different from rest. However, vascular resistance decreased only in the cerebellar cortex. Due to a 58% increment in arterial O2 content with SE, the O2 supply to all regions of the brain increased (P less than 0.01). The latter may be suggestive of an overall increase in brain metabolism during heavy exertion in ponies.

Animals↗
PubMed1987

Regional distribution of brain blood flow during maximal exertion in splenectomized ponies.

It has been reported in exercising ponies that O2 supply to all regions of the brain increased primarily due to a large increment in CaO2 and it was implied that this may reflect a generalized increase in brain metabolism during strenuous exercise. Splenectomy ameliorates the rise in CaO2 observed with exercise in ponies. Thus, the objective of the present study was to examine changes in regional brain blood flow and O2 supply of splenectomized ponies with sub-maximal and maximal exercise and to compare these data with previous observations in normal ponies. It was reasoned that in the absence of a marked rise in CaO2, the brain blood flow of splenectomized ponies would have to increase markedly if brain metabolism also increased with severe exercise. Regional brain blood flow was studied using 15 micron diameter radionuclide labeled microspheres injected into the left atrium during rest (control) and sub-maximal as well as maximal exertion on a treadmill. It was observed that despite marked arterial hypocapnia and acute systemic hypertension which developed during exercise, blood flow as well as O2 supply in the cerebral cortex, caudate nuclei, cerebral white matter, cerebellar white matter, thalamus-hypothalamus, mid-brain, pons and medulla were not different from control values. In the cerebrellar cortex, however, blood flow and O2 supply increased with both work intensities. Thus, it was concluded that in exercising ponies, metabolic O2 requirement increased in the cerebellar cortex but was most likely not different from control (rest) in other regions of the brain.

Animals↗
PubMed1991

Evidence for related myopathies in exertional heat stroke and malignant hyperthermia.

Malignant hyperthermia may be a human stress syndrome, of which heat stroke is one manifestation. Two men in military service who had episodes of exertional heat stroke, and their immediate family members, were tested for susceptibility to malignant hyperthermia by in-vitro contracture tests on skeletal muscle samples. Muscle from both patients had a normal response to caffeine but an abnormal response to halothane. Muscle from the father of one patient had an abnormal response to halothane, and that from the father of the second patient had an abnormal response to ryanodine. The results indicate that clinical heat stroke may be associated with an underlying inherited abnormality of skeletal muscle that is similar, but not identical, to that of malignant hyperthermia.

Adult↗
PubMed1983

Decrease in human voluntary isometric arm strength induced by simultaneous bilateral exertion.

Human voluntary isometric maximum muscle strength during simultaneous bilateral versus separate unilateral elbow extension and flexion was measured. The following results were obtained. (1) Strength was reduced under the condition of simultaneous bilateral exertion of contralateral corresponding muscles as compared to the unilateral condition. (2) The decrease ratio of strength was 24.6 and 18.8% for the right and left for extension and 6.3 and 7.6% for the right and left for flexion. The extension-flexion difference was statistically significant but right-left difference was not significant. (3) Integrated EMG showed the tendency comparable to the strength and high correlation was found between strength and integrated EMG. (4) Decrease ratio was reduced when extension of one arm and flexion of the other arm was simultaneously performed. (5) Possible mechanisms subserving these findings were postulated and discussed.

Adult↗
PubMed1995

On the nature of the link between malignant hyperthermia and exertional heatstroke.

Malignant hyperthermia (MH) is a rare myopathy inducing severe accident when carriers are exposed to triggering agents. MH susceptibility (MHS) is assessed by pharmacological tests performed on muscle strips. Exertional heat stroke (EHS) is a severe accident occurring during long and strenuous exercise. It has been observed that numerous EHS patients are susceptible to MH according to pharmacological tests. Because most of those EHS-MHS subjects were soldiers, we hypothesize that military duty could select subjects with infraclinical myopathy and therefore would increase the MHS:EHS subject ratio.

Animals↗
PubMed1988

Severe metabolic acidosis secondary to exertional hyperlactemia.

A case is presented of severe metabolic acidosis in a previously healthy man. The cause was attributed to lactic acidosis secondary to exertion. Although lactic acid is commonly produced with increased physical activity, it is usually cleared and buffered rapidly. The pathophysiology of lactic acidosis is discussed.

Acidosis, Lactic↗
PubMed2003

Usefulness of B-type natriuretic peptide in hypertensive patients with exertional dyspnea and normal left ventricular ejection fraction and correlation with new echocardiographic indexes of systolic and diastolic function.

B-type natriuretic peptide (BNP) levels increase in systolic heart failure (HF). However, the value of BNP in hypertensive patients with suspected diastolic HF (symptoms suggestive of HF but normal ejection fraction) and its relation to myocardial function in these patients is unclear. We prospectively studied 72 ambulatory hypertensive subjects (40 women, mean age 58 +/- 8 years) with exertional dyspnea and ejection fraction > or =50%. Diastolic function was evaluated with transmitral and pulmonary venous Doppler, mitral annular velocities (pulsed-wave tissue Doppler), and flow propagation velocity (color M-mode). Systolic function was assessed with strain and strain rate derived from color tissue Doppler imaging. BNP was related to myocardial function and the presence or absence of global diastolic dysfunction. By conventional Doppler criteria, 34 patients had normal left ventricular diastolic function and 38 had isolated diastolic dysfunction. BNP values were higher in patients with diastolic dysfunction (46 +/- 48 vs 20 +/- 20 pg/ml, p=0.004) and were related independently to blood pressure, systolic strain rate, left atrial function (p<0.01 for all), and age (p=0.015). Patients with diastolic dysfunction and pseudonormal filling had higher BNP levels compared with impaired relaxation (89 +/- 47 vs 35 +/- 42 pg/ml, p=0.001). However, 79% of patients with diastolic dysfunction had BNP levels within the normal range. We conclude that in ambulatory hypertensive patients with symptoms suggestive of mild HF and normal ejection fraction, BNP is related to atrial and ventricular systolic parameters, blood pressure, and age. Although elevated in the presence of diastolic dysfunction, the BNP level mostly is in the normal range and, therefore, has limited diagnostic value in stable patients with suspected diastolic HF.

Biomarkers↗
PubMed2005

Borg's rating of perceived exertion scales: do the verbal anchors mean the same for different clinical groups?

OBJECTIVE: To examine the interpretation of the verbal anchors used in the Borg rating of perceived exertion (RPE) scales in different clinical groups and a healthy control group. DESIGN: Prospective experimental study. SETTING: Rehabilitation center. PARTICIPANTS: Nineteen subjects with brain injury, 16 with chronic low back pain (CLBP), and 20 healthy controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Subjects used a visual analog scale (VAS) to rate their interpretation of the verbal anchors from the Borg RPE 6-20 and the newer 10-point category ratio scale. RESULTS: All groups placed the verbal anchors in the order that they occur on the scales. There were significant within-group differences ( P >.05) between VAS scores for 4 verbal anchors in the control group, 8 in the CLBP group, and 2 in the brain injury group. There was no significant difference in rating of each verbal anchor between the groups ( P >.05). CONCLUSIONS: All subjects rated the verbal anchors in the order they occur on the scales, but there was less agreement in rating of each verbal anchor among subjects in the brain injury group. Clinicians should consider the possibility of small discrepancies in the meaning of the verbal anchors to subjects, particularly those recovering from brain injury, when they evaluate exercise perceptions.

Adult↗
PubMed2005

Aging of the respiratory system: impact on pulmonary function tests and adaptation to exertion.

Normal aging of the respiratory system is associated with a decrease in static elastic recoil of the lung, in respiratory muscle performance, and in compliance of the chest wall and respiratory system, resulting in increased work of breathing compared with younger subjects and a diminished respiratory reserve in cases of acute illness, such as heart failure, infection, or airway obstruction. In spite of these changes, the respiratory system remains capable of maintaining adequate gas exchange at rest and during exertion during the entire lifespan, with only a slight decrease in Pa(O2) and no significant change in Pa(CO2).

Adaptation, Physiological↗