Prolonged Exercise Test Research Articles

DECREMENTAL RESPONSE ON PROLONGED EXERCISE TEST IN A PATIENT WITH THYROTOXIC PERIODIC PARALYSIS

Paralysis of acute onset often presents a diagnostic challenge for the assessing physician because of a large number of differential diagnosis and overlap of clinical features among them. Thyrotoxic periodic paralysis is an uncommon cause of acute weakness. In addition to serological tests, electromyography findings during prolonged exercise test are very helpful in confirming the diagnosis. Only a few case reports of thyrotoxic periodic paralysis have been published from Middle East and none of them have described this specific electrophysiological data. A man in his 20s presented to us with acute onset weakness in both legs which was evaluated further and found to have hypokalemia. The work up for the etiology revealed thyrotoxic status and a final diagnosis of thyrotoxic periodic paralysis was established. The prolonged exercise test performed in this patient showed typical progressive decremental respsonse with nadir at 40 minutes after the exercise.

Prolonged Exercise Test in Patients With History of Thyrotoxicosis.

Thyrotoxic periodic paralysis is characterized by recurrent episodes of reversible, severe proximal muscle weakness associated with hypokalemia and hyperthyroidism. Prolonged exercise test is an easy, noninvasive method of demonstrating abnormal muscle membrane excitability in periodic paralyses. Although abnormal in thyrotoxic periodic paralysis patients, the effects thyroid hormone levels in non-thyrotoxic periodic paralysis thyrotoxicosis patients have not been well studied. The study aims to evaluate thyrotoxicosis patients (regardless of thyrotoxic periodic paralysis history) with prolonged exercise test and correlate it with their thyroid status. This is a prospective, cross-sectional study of consecutive thyrotoxicosis patients seen at the endocrine clinic of a tertiary medical center. Thyroid status was determined biochemically before prolonged exercise test. Compound muscle action potential (CMAP) amplitudes postexercise were compared against pre-exercise amplitudes and recorded as percentage of mean baseline CMAP amplitude. Comparisons of time-dependent postexercise CMAP amplitudes and mean CMAP amplitude decrement were made between hyperthyroid and nonhyperthyroid groups. Seventy-four patients were recruited, 23 (31%) men, 30 (41%) Chinese, and the mean age was 48.5 ± 16.8 years. Of 74 patients, 32 (43%) were hyperthyroid and 42 (57%) were nonhyperthyroid viz. euthyroid and hypothyroid. Time-dependent CMAP amplitudes from 10 to 45 minutes after exercise were significantly lower in hyperthyroid patients compared with nonhyperthyroid patients (P < 0.01). Mean CMAP amplitude decrement postexercise was significantly greater in hyperthyroid than nonhyperthyroid patients (23.4% ± 11.4% vs. 17.3% ± 10.5%; P = 0.02). Compound muscle action potential amplitude declines on prolonged exercise test were significantly greater in hyperthyroid patients compared with nonhyperthyroid patients. Muscle membrane excitability is highly influenced by thyroid hormone level. Thyrotoxic periodic paralysis occurs from increased levels of thyroid hormone activity in susceptible patients.

Exercise Training Combined with Bifidobacterium longum OLP-01 Supplementation Improves Exercise Physiological Adaption and Performance.

Probiotics exert multiple health benefits, including gastrointestinal health, immunoregulation, and metabolic disease improvement, by modulating microbiota to maintain eubiosis via the hypothalamic–pituitary–adrenal (HPA) and brain–gut–microbiome axes. Physiological fatigue, mental stress, and gastrointestinal discomfort under the demands of athletic performance as well as immunosuppression are common during endurance training and competition. Limited studies investigated the functional effects of probiotic supplementation on endurance training. Bifidobacterium longum subsp. Longum OLP-01 (OLP-01), isolated from an elite Olympic athlete, was combined with a six-week exercise training program with gradually increasing intensity. In this study, Institute of Cancer Research (ICR) mice were assigned to sedentary, exercise, OLP-01, or exercise + OLP-01 groups and administered probiotic and/or treadmill exercise training for six weeks to assess exercise performance, physiological adaption, and related metabolites. The exercise + OLP-01 group demonstrated higher performance in terms of endurance and grip strength, as well as improved fatigue-associated indexes (lactate, ammonia, creatine kinase (CK), lactate dehydrogenase (LDH), and glycogen content), compared with the other groups. OLP-01 supplementation significantly ameliorated inflammation and injury indexes (platelet/lymphocyte ratio (PLR), aminotransferase (AST), and CK) caused by prolonged endurance exercise test. Moreover, acetate, propionate, and butyrate levels were significantly higher in the exercise + OLP-01 group than in the sedentary and OLP-01 groups. Athletes often experience psychological and physiological stress caused by programed intensive exercise, competition, and off-site training, often leading to poor exercise performance and gastrointestinal issues. Functional OLP-01 probiotics are considered to be a nutritional strategy for improving physiological adaption, oxidative stress, inflammation, and energy balance to ensure high physical performance. Based on these results, probiotics combined with exercise training is a potential strategy for ensuring high physical performance of athletes, which should be further investigated through microbiota validation.

Hypokalemic Periodic Paralysis Cases with Substitutions from Arginine to Lysine in the Voltage Sensor

Familial hypokalemic periodic paralysis (HypoPP) is a rare skeletal muscle disease caused by the dysregulation of excitability in salcolemma. HypoPP is characterized by repeated episodic paralytic attacks with hypokalemia and several mutations in CACNA1S gene coding Cav1.1 and SCN4A gene coding Nav1.4 have been identified as causative mutations. Most of the mutations are substitution to non-charged amino acid from the positively charged arginine (R) in segment 4 (S4) of the voltage sensor in either Cav1.1 or Nav1.4. Biophysical experiments demonstrated that the loss of the charge in S4 by the arginine-to-non-charged substitution creates a leak current called “gating pore current”. Since the discovery, “the gating pore current theory” has been suggested as the common pathogenic feature in HypoPP. However, the pathological mechanism from generation of “gating pore current” to paralytic attack is still unknown. In this report, we have identified five cases with an arginine(R)-to-lysine (K) substitution in voltage sensor, which retained positive net charge of S4 ; one is a Japanese boy with R219K mutation in SCN4A gene and the other four are one Japanese man, one French man and two French brothers with R897K mutation in CACNA1S gene. All cases presented typical paralytic episodes with hypokalemia and, in four of five cases, significant decrement in the compound action potential was observed with prolonged exercise test. From Nav1.4-R219K mutant channel expressed in vitro, we measured the ionic current by patch-clamp technique and the gating pore current by cut-open voltage clamp technique. Nav1.4-R219K revealed gating pore current, but the size of the conductance was smaller compared to that observed in other mutant HypoPP-Nav1.4 channels previously reported. Our data might provide a new insight in pathogenic mechanism of HypoPP.

Tissue Blood Volume Parameters Measured by Continuous-Wave and Spatially Resolved NIRS Show Different Changes During Prolonged Cycling Exercise.

Near-infrared spectroscopy (NIRS) shows two types of tissue blood volume (BV) parameters: the total hemoglobin concentration (cHb; assessed by continuous-wave NIRS) and the normalized tissue hemoglobin index (nTHI; evaluated by spatially resolved NIRS). This study was performed to investigate the differences between cHb and nTHI, estimated by calibration using acute reduction of BV at the onset of exercise. Seven active male volunteers (age: 22 ± 4 years) performed a prolonged (60-min) cycling exercise test at 65% or 70% of the peak oxygen uptake. During the tests, cHb and nTHI from the vastus lateralis muscle were monitored. The two parameters were expressed relative to the resting value of 100% and the minimum value of 0% at the onset of exercise. The value of cHb started to increase after arriving at the minimum value and continued until the end of exercise. Similar to cHb, nTHI increased acutely from the lowest level, but the parameter remained almost unchanged from ~5 min throughout the test. Therefore, the two parameters interacted significantly. Moreover, in comparison with the same exercise duration, cHb was significantly higher than nTHI from the 28th min to the end of the test. These results suggest that cHb and nTHI in working muscle are not synchronized during prolonged exercise, especially after ~30 min. The differences between the two BV parameters are likely partly attributable to other factors, such as the increase in skin blood flow.

Prediction of lactate threshold using the modified Conconi test in distance runners.

This study aimed to examine the validity of the modified Conconi test (CT) to predict lactate threshold (LT) during running. Twelve distance runners randomly performed the modified CT and the incremental test in which LT was determined directly by measuring blood lactate (BLa). Mean values of heart rate (HR) and running speed (RS) at heart rate deflection point (HRDP) obtained through the modified CT were compared with those at LT. Subsequently, the runners who showed a HRDP in the modified CT performed a 30-min prolonged exercise test (PET) at a RS corresponding to HRDP. During this test, the kinetics of BLa and HR were analyzed to determine whether a steady state in these variables could be attained. We succeeded in identifying HRDP in nine of our runners, whereas the remaining three runners showed entirely linear HR response. In those nine runners, no significant difference was found between HR and RS at HRDP and those at LT. Significant correlation was found between HR at HRDP and HR at LT (r = 0.84, p = 0.005), but RS at HRDP was not significantly correlated with RS at LT (r = 0.63, p = 0.07). All nine runners were able to complete the PET with steady state conditions being achieved for both BLa and HR. In conclusion, these findings indicate that the modified CT has a potential to be used as an alternative method for assessment of LT in distance runners presenting a HRDP.

Non-dystrophic myotonia: prospective study of objective and patient reported outcomes

Non-dystrophic myotonias are rare diseases caused by mutations in skeletal muscle chloride and sodium ion channels with considerable phenotypic overlap between diseases. Few prospective studies have evaluated the sensitivity of symptoms and signs of myotonia in a large cohort of patients. We performed a prospective observational study of 95 participants with definite or clinically suspected non-dystrophic myotonia recruited from six sites in the USA, UK and Canada between March 2006 and March 2009. We used the common infrastructure and data elements provided by the NIH-funded Rare Disease Clinical Research Network. Outcomes included a standardized symptom interview and physical exam; the Short Form-36 and the Individualized Neuromuscular Quality of Life instruments; electrophysiological short and prolonged exercise tests; manual muscle testing; and a modified get-up-and-go test. Thirty-two participants had chloride channel mutations, 34 had sodium channel mutations, nine had myotonic dystrophy type 2, one had myotonic dystrophy type 1, and 17 had no identified mutation. Phenotype comparisons were restricted to those with sodium channel mutations, chloride channel mutations, and myotonic dystrophy type 2. Muscle stiffness was the most prominent symptom overall, seen in 66.7% to 100% of participants. In comparison with chloride channel mutations, participants with sodium mutations had an earlier age of onset of stiffness (5 years versus 10 years), frequent eye closure myotonia (73.5% versus 25%), more impairment on the Individualized Neuromuscular Quality of Life summary score (20.0 versus 9.44), and paradoxical eye closure myotonia (50% versus 0%). Handgrip myotonia was seen in three-quarters of participants, with warm up of myotonia in 75% chloride channel mutations, but also 35.3% of sodium channel mutations. The short exercise test showed ≥10% decrement in the compound muscle action potential amplitude in 59.3% of chloride channel participants compared with 27.6% of sodium channel participants, which increased post-cooling to 57.6% in sodium channel mutations. In evaluation of patients with clinical and electrical myotonia, despite considerable phenotypic overlap, the presence of eye closure myotonia, paradoxical myotonia, and an increase in short exercise test sensitivity post-cooling suggest sodium channel mutations. Outcomes designed to measure stiffness or the electrophysiological correlates of stiffness may prove useful for future clinical trials, regardless of underlying mutation, and include patient-reported stiffness, bedside manoeuvres to evaluate myotonia, muscle specific quality of life instruments and short exercise testing.

Oral contraception but not menstrual cycle phase is associated with increased free cortisol levels and low hypothalamo-pituitary-adrenal axis reactivity.

In females, estrogen is a potential modulator of cortisol response to stressors. The aim of this study was to determine the influence of menstrual cycle phase, oral contraception (OC) use and exercise training on hypothalamo-pituitary-adrenal (HPA) axis activity and reactivity after physical stress. We investigated the effects of the menstrual cycle and OC use on exhaustive exerciseinduced changes in free salivary cortisol concentrations and free urinary cortisol/cortisone excretion in healthy young women. Twenty-eight women were allocated to an untrained group (no.=16) or a trained group (no.=12), depending on their physical training background. The untrained group was composed of nine OC users (UNTOC+) and seven eumenorrheic women (UNT-OC-) tested in the follicular and luteal phases, while the trained group was entirely composed of OC+ subjects (T-OC+). Three laboratory sessions were conducted in a randomised order: a prolonged exercise test, a short-term exercise test, and a control session. For each session, urine and saliva specimens were collected at rest (09:00 h) and then, 30, 60 and 90 min later. Estradiol fluctuation during the menstrual cycle phase did not alter free cortisol baseline values and responses to exercise. OC use was associated with increased free resting salivary concentrations and urinary cortisol excretion with blunted salivary cortisol response to prolonged exercise stimulation. No training effect was noted. OC but not menstrual cycle phase is associated with increased free cortisol levels and low HPA axis reactivity.

Nandrolone excretion in sedentary vs physically trained young women

We investigated the effects of the menstrual cycle, oral contraception and physical training on exhaustive exercise-induced changes in the excretion of nandrolone metabolites [19-norandrosterone (19-NA), and 19-noretiocholanolone (19-NE)] in young women. Twenty-eight women were allocated to an untrained group (n=16) or a trained group (n=12), depending on their physical training background. The untrained group was composed of nine oral contraceptive users (OC+) and seven eumenorrheic women (OC-), while the trained group was entirely composed of OC+ subjects. Three laboratory sessions were conducted in a randomized order: a prolonged exercise test, a short-term exercise test and a control session. Urine specimens were collected before and 30, 60 and 90 min after the exercise test and at the same times of the day during the control session. Urinary concentrations of nandrolone metabolites were determined by gas chromatography coupled to mass spectrometry. Urinary concentrations of 19-NA and 19-NE ranged from undetectable levels to 1.14 and 0.47 ng/mL, respectively. Nandrolone excretion was not affected by the menstrual cycle phase (early follicular vs mid-luteal), prior physical training, oral contraception or acute physical exercise. Therefore, a urinary concentration of 2 ng/mL of 19-NA appears to be fair as the upper acceptable limit in doping control tests for female athletes.

Exercise Stress Testing in Children with Metabolic or Neuromuscular Disorders

The role of exercise as a diagnostic or therapeutic tool in patients with a metabolic disease (MD) or neuromuscular disorder (NMD) is relatively underresearched. In this paper we describe the metabolic profiles during exercise in 13 children (9 boys, 4 girls, age 5–15 yrs) with a diagnosed MD or NMD. Graded cardiopulmonary exercise tests and/or a 90-min prolonged submaximal exercise test were performed. During exercise, respiratory gas-exchange and heart rate were monitored; blood and urine samples were collected for biochemical analysis at set time points. Several characteristics in our patient group were observed, which reflected the differences in pathophysiology of the various disorders. Metabolic profiles during exercises CPET and PXT seem helpful in the evaluation of patients with a MD or NMD.

1H NMR-based metabolomics approach for exploring urinary metabolome modifications after acute and chronic physical exercise

Metabolomics is a comprehensive method for metabolite assessment that involves measuring the overall metabolic signature of biological samples. We used this approach to investigate biochemical changes due to acute and chronic physical exercise. Twenty-two women using identical oral contraceptives were segregated into an untrained (n = 10) or trained (n = 12) group depending on their physical training background. The subjects performed two exercises in a randomized order: a prolonged exercise test (75% of their VO(2 max) until exhaustion) and a short-term, intensive exercise test (short-term, intensive exercise anaerobic test). Urine specimens were collected before and 30 min after each test. The samples were analyzed by (1)H NMR spectroscopy, and multivariate statistical techniques were utilized to process the data. Distinguishing characteristics were observed only in the urine profiles of specimens collected before vs. 30 min after the short-term, intensive exercise test. The metabolites responsible for such changes were creatinine, lactate, pyruvate, alanine, beta-hydroxybutyrate, acetate, and hypoxanthine. In both groups, the excretion of lactate, pyruvate, alanine, beta-hydroxybutyrate, and hypoxanthine increased similarly after the completion of the short-term, intensive exercise test (p < 0.03). However, acetate excretion increased to a lesser extent in trained than in untrained subjects (p < 0.05). In conclusion, metabolomics is a promising tool in order to gain insight into physiological status and to clarify the changes induced by short-term, intense physical exercise.

Growth Hormone Receptor Antagonist Treatment Reduces Exercise Performance in Young Males

The effects of GH on exercise performance remain unclear. The aim of the study was to examine the effects of GH receptor (GHR) antagonist treatment on exercise performance. Subjects were treated with the GHR antagonist pegvisomant or placebo for 16 d. After the treatment period, they exercised to determine exercise performance and hormonal and metabolic responses. Twenty healthy males participated in the study. Subjects were treated with the GHR antagonist (n = 10; 10 mg/d) or placebo (n = 10). After the treatment period, they performed a maximal oxygen uptake (VO(2 max)) test and a prolonged exercise test, consisting of 60 min of submaximal cycling followed by exercise to fatigue at 90% of VO(2 max). VO(2 max) was measured before and after the treatment period. Hormonal and metabolic responses and time to exhaustion during prolonged exercise were determined. Resting serum IGF-I concentration decreased by 20% in the GHR antagonist-treated group (P < 0.05), whereas no change was observed in the placebo group. Conversely, resting serum GH concentration was significantly higher in the treatment group compared with the placebo group (P < 0.01). VO(2 max) did not change significantly in either group after the treatment period. Time to exhaustion at 90% of VO(2 max) was significantly shorter in the treatment group (P < 0.05). No significant differences were observed between the groups in terms of changes in serum free fatty acids, glycerol, VO(2), or relative fat oxidation. GH might be an important determinant of exercise capacity during prolonged exercise, but GHR antagonist did not alter fat metabolism during exercise.

PO7.8 The Sensitivity of Prolonged Exercise Test in Diagnosis of Thyrotoxic Periodic Paralysis can be Improved by Longer Duration of Exercise: A Case Report

PO7.8 The Sensitivity of Prolonged Exercise Test in Diagnosis of Thyrotoxic Periodic Paralysis can be Improved by Longer Duration of Exercise: A Case Report

Effects of menstrual cycle, oral contraception, and training on exercise-induced changes in circulating DHEA-sulphate and testosterone in young women

The objective of this study was to ascertain the effects of menstrual cycle, oral contraception, and training status on the exercise-induced changes in circulating DHEA-sulphate and testosterone in young women. Twenty-eight healthy women were assigned to an untrained group (n = 16) or a trained group (n = 12) depending on their training background. The untrained group was composed of nine oral contraceptive users (OC+) and seven eumenorrheic women (OC-). The trained group was composed of OC+ subjects only. All the OC+ subjects were taking the same low-dose oral contraception. Three laboratory sessions were organised in a randomised order: a prolonged exercise test until exhaustion, a short-term exhaustive exercise test, and a control session. Blood specimens were collected before, during and after the exercise tests and at the same time of the day during the control session. Basal circulating testosterone was significantly lower in trained as compared to untrained subjects. In all subjects, the prolonged exhaustive exercise induced a significant increase in circulating DHEA-s and testosterone. The short-term exercise induced a significant increase in circulating DHEA-s in untrained eumenorrheic and in trained OC users only. Menstrual phases in OC- did not influence the responses. It was found that exhaustive physical exercise induced an increase in circulating DHEA-s and testosterone in young women. Oral contraception may limit short-term exercise-induced changes.

Muscle membrane excitability after exercise in thyrotoxic periodic paralysis and thyrotoxicosis without periodic paralysis

We evaluated whether the paralytic attacks in thyrotoxic periodic paralysis (TPP) are primarily due to the abnormal excitability of the muscle membrane caused by a preexisting latent abnormality or to the effects of thyroid hormone. The prolonged exercise (PE) test was used to evaluate muscle membrane excitability in 21 patients with TPP and 11 patients with thyrotoxicosis without paralytic attacks (Tw/oPP) in the hyperthyroid state. The PE tests were compared between the hyperthyroid and euthyroid states in five of the TPP and three of the Tw/oPP patients. Compared to 20 healthy subjects, a significant increase in compound muscle action potential (CMAP) amplitudes immediately after exercise and a significant time-dependent gradual decline in CMAP amplitudes starting from 20 min after exercise were observed in the TPP patients. A significant decline in CMAP amplitudes was also observed in the Tw/oPP patients but only at 50 min after exercise. All of the TPP and Tw/oPP patients had a tendency to improve in the euthyroid state; the PE tests remained abnormal only in the TPP patients. Paralytic attacks in TPP patients are due primarily to a preexisting latent abnormal excitability of the muscle membrane, possibly genetic in origin.

Prolonged exercise testing in two children with a mild Multiple Acyl-CoA-Dehydrogenase deficiency

BackgroundMultiple Acyl-CoA-Dehydrogenase deficiency (MADD) is an inherited metabolic disorder characterized by impaired oxidation of fatty acids and some amino acids.MethodsWe were interested whether children with MADD could tolerate a prolonged low-intensity exercise test and if this test could have any additional diagnostic value. Therefore, we performed a maximal exercise test and a low-intensity prolonged exercise test in 2 patients with MADD and in 5 control subjects. During a prolonged exercise test the subjects exercised on a cycle ergometer at a constant workload of 30% of their maximum for 90 minutes and heart rate, oxygen uptake, fuel utilization and changes in relevant blood and urinary parameters were monitored.ResultsThe tests were tolerated well. During the prolonged exercise test the fatty acid oxidation (FAO) was quite low compared to 5 control subjects, while characteristic metabolites of MADD appeared in plasma and urine.ConclusionWe suggest that the prolonged exercise test could be of diagnostic importance and might replace the fasting test as a diagnostic procedure in some cases, particularly in patients with anamnestic signs of intolerance for prolonged exercise.

Pre-exercise antioxidant enzyme activities determine the antioxidant enzyme erythrocyte response to exercise

Free radical production increases during exercise and oxidative damage occurs in several tissues. We examined the effects of three different exercise tests on the pattern of change of erythrocyte enzyme antioxidant activities. The tests were a short maximal exercise test, a submaximal prolonged exercise test and a cycling stage during competition. The participants were amateur and professional cyclists with different training statuses and different basal erythrocyte antioxidant enzyme activities. The maximal test produced no changes in the erythrocyte antioxidant enzyme activities of amateur sportsmen. The submaximal test, performed at 80% of maximal oxygen uptake, decreased erythrocyte catalase (12%), glutathione peroxidase determined with H2O2 (14%) and glutathione reductase (16%); superoxide dismutase activity increased by about 25%. The cycling stage performed by professional cyclists increased erythrocyte catalase (29%) and glutathione reductase (10%) activities. The in vivo changes in glutathione reductase activity were confirmed by in vitro measurements: hydrogen peroxide decreased and the presence of catalase increased the activity of this enzyme. In conclusion, we suggest that the different erythrocyte antioxidant enzyme responses to diverse exercise tests can be explained by the effects of hydrogen peroxide and the superoxide anion on the antioxidant enzyme activities in erythrocytes.

Different effects of exercise tests on the antioxidant enzyme activities in lymphocytes and neutrophils

We have determined the effects of maximal and submaximal cycloergometer tests on the antioxidant enzyme defences of neutrophils and lymphocytes. We also compared the neutrophil and lymphocyte basal enzyme antioxidant activities. A total of 17 well-trained amateur athletes, runners, and cyclists participated in this study. Two tests were performed on an electromagnetic reduction cycloergometer: the maximal exercise test, and the submaximal prolonged exercise test. Blood samples were taken before and after the tests. Basal enzyme activity of superoxide dismutase was higher in lymphocytes but neutrophils presented higher activities of catalase and glutathione peroxidase. The maximal test increased the circulating number of lymphocytes and the activities of catalase and glutathione peroxidase. No changes were observed in lymphocyte number or in lymphocyte antioxidant enzyme activities after the submaximal test. The circulating number of neutrophils increased significantly after the submaximal test. Maximal and submaximal tests decreased the activities of neutrophil glutathione dependent antioxidant enzymes (glutathione peroxidase and glutathione reductase), but no changes were observed in catalase or superoxide dismutase activities after either test. Neither the maximal nor submaximal test produced increases in serum activities of lactate dehydrogenase and creatine kinase (CK).

Electrophysiologie clinique des canalopathies musculaires

Electrodiagnostic testing should always be tailored to the clinical setting; in the muscle channelopathies, provocative tests are essential to demonstrate the modifications of the muscle excitability. When a permanent muscle weakness is present, a post-exercise (or post-tetanic) potentiation should be search to demonstrate a presynaptic neuromuscular channelopathy; when the weakness is fluctuating it is useful to perform repetitive nerve stimulation to see if a decrement is present or if the jitter is prolonged, indicative of a postsynaptic neuromuscular channelopathy; when the weakness is episodic, the prolonged exercise test is the only test to demonstrate the appearance of a late post-exercise decrement (sodium and calcium channelopathies), and when a myotonic reaction is seen to search the myotonic discharges by needle emg. The concomitant presence of myotonic discharges and abnormal decrement of the motor responses during repetitive nerve stimulation train depend on the type of mutations in the chloride gene and the amount of CTG repeats in myotonic dystrophy type 1. In paramyotonia congenita there a prolonged decrement when the tests are carried out with cooling the recorded muscle. Electrophysiological testings appear therefore useful to diagnose muscle channelopathies but also give information about the prognosis of the disorder; they could also be viewed as useful tests to predict response to treatments.

Effect of exercise intensity and training on antioxidants and cholesterol profile in cyclists

The aim of this work was to evaluate the effect of different intensity of exercise and different training status on antioxidants and cholesterol profile in cyclists. 33 male cyclists (17 amateur and 16 professional cyclists) participated in this study. The amateurs all trained 14 ± 1 h each week, and their VO 2 max was 62.5 ± 1.8 ml/Kg.min; the professionals all trained 24 ± 1 h each week, and their VO 2 max was 80.2 ± 1.6 ml/Kg.min. Amateurs were submitted to the maximal and submaximal prolonged exercise tests. Professionals were submitted to a mountain stage (170 km) of cycling competition. Serum lipid and cholesterol profile (triglycerides, total cholesterol, HDL-cholesterol, LDL-cholesterol and VLDL-cholesterol) and plasma antioxidant capacity (ascorbic acid, α-tocopherol, retinol, β-carotene and others) were measured before and after exercise tests. Hematological determinations (number of erythrocytes, hematocrit and hemoglobin concentration) and dietary intake were also measured. No significant differences were observed in basal values (before exercise tests) of amateur and professional cyclists. Negligible differences were found between dietary intake of amateur and professional cyclists, and also the results of hematological values showed there was no effect of degree of hydration or dietary intake on blood levels of studied antioxidant and lipid parameters. An increase in plasma levels of vitamin C, vitamin E, triglycerides and VLDL-cholesterol levels, and also a decrease of β-carotene and LDL-cholesterol. were observed in well-trained professional cyclists after the cycling stage - an endurance exercise - but not in amateur cyclists. Amateur cyclists showed only mild increases in total cholesterol after maximal and submaximal exercise, while a rise in HDL-cholesterol was only observed after maximal exercise; none of these changes were observed in professional cyclists. Plasma levels of antioxidant vitamins and carotenes, and also serum lipids, total cholesterol and lipoprotein-cholesterol showed an overall response to exercise, and their increase and/or decrease must be explained as a consequence of the different training status of sportsmen and intensity and duration of exercise tests.