Combined effects of whole-body vibration, resistance exercise, and vascular occlusion on skeletal muscle and performance.

The purpose of this study was to evaluate the effects of a new high-intensity training modality comprised of vibration exercise with superimposed resistance exercise and vascular occlusion (vibroX) on skeletal muscle and performance. Young untrained women were randomized to either train in a progressive mode on 3 days per week for 5 weeks ( N=12) or to maintain a sedentary lifestyle ( N=9). VibroX increased peak cycling power (+9%, P=0.001), endurance capacity (+57%, P=0.002), ventilatory threshold (+12%, P<0.001), and end-test torque (+15%, P=0.002) relative to the sedentary group. Training load increased by 84.5% ( P<0.001) after vibroX. The increases were paralleled by increases in myosin heavy chain type 1 vastus lateralis muscle fiber cross-sectional area (+14%, P=0.031) and proportion (+17%, P=0.015), thigh lean mass (+4%, P=0.001), capillary-to-fiber ratio (+14%, P=0.003), and cytochrome c oxidase activity. Conversely, maximal values for oxygen consumption, cardiac output, isokinetic leg extension power and jumping power remained unaffected. Notably, vastus lateralis muscle adaptations were achieved with a very low weekly training volume. We conclude that vibroX quickly increases muscle (fiber) size, capillarization, and oxidative potential, and markedly augments endurance capacity in young women.

Effects of a 12-week intervention period with football and running for habitually active men with mild hypertension.

The present study examined the effect of football (F, n=15) training on the health profile of habitually active 25-45-year-old men with mild hypertension and compared it with running (R, n=15) training and no additional activity (controls, C, n=17). The participants in F and R completed a 1-h training session 2.4 times/week for 12 weeks. Systolic and diastolic blood pressure decreased in all groups but the decrease in diastolic blood pressure in F (-9 +/- 5 (+/- SD) mmHg) was higher than that in C (-4 +/- 6 mmHg). F was as effective as R in decreasing body mass (-1.6 +/- 1.8 vs-1.5 +/- 2.1 kg) and total fat mass (-2.0 +/- 1.5 vs -1.6 +/- 1.5 kg) and in increasing supine heart rate variability, whereas no changes were detected for C. Maximal stroke volume improved in F (+13.1%) as well as in R (+10.1%) compared with C (-4.9%). Total cholesterol decreased in F (5.8 +/- 1.2 to 5.5 +/- 0.9 mmol/L) but was not altered in R and C. We conclude that football training, consisting of high-intensity intermittent exercise, results in positive effects on blood pressure, body composition, stroke volume and supine heart rate variability, and elicits at least the same cardiovascular health benefits as continuous running exercise in habitually active men with mild hypertension.

Reliability of measurements with Innocor during exercise.

Cardiac output represents the primary determinant of cardiovascular function. Therefore, understanding how cardiac output is regulated during exercise is crucial. A recently developed tool for determining cardiac output is the Innocor rebreathing system, which also incorporates an ergospirometry unit. So far, Innocor's test-retest reliability under exercise conditions has not been determined in healthy participants. Therefore, 15 male and 15 female healthy participants [30.6 y (SD 4.5); 68.0 kg (SD 10.5)] performed 2 test sessions, each consisting of 2 graded exercise tests to volitional exhaustion. We determined intra- and inter-session reliability of cardiac output, oxygen consumption, carbon dioxide output, and ventilation at 130 W and at peak exercise. For cardiac output, we found averaged coefficients of variation ranging from 4.3 (intra-session, 130 W) to 10.0% (inter-session, rest). For oxygen consumption, coefficients of variation ranged from 3.4 (intra-session, peak) to 5.7% (inter-session, peak). Coefficients of variation for carbon dioxide output were between 4.4 (intra-session, peak) and 6.6% (inter-session, peak), and for ventilation between 5.1 (intra-session, 130 W) and 7.0% (intra-session, peak). Innocor delivers safe and reliable measurements of cardiac output, gas exchange, and ventilation. Therefore, Innocor can be used to assess these parameters in exercise physiology studies as well as in performance diagnostics.

Creatine feeding does not enhance intramyocellular glycogen concentration during carbohydrate loading: an in vivo study by 31P- and 13C-MRS.

The main aim of this study was to examine the hypothesis that creatine (Cr) feeding enhances myocellular glycogen storage in humans undergoing carbohydrate loading. Twenty trained male subjects were randomly assigned to have their diets supplemented daily with 252 g of glucose polymer (GP) and either 21 g of Cr (CR-GP, n = 10) or placebo (PL-GP, n = 10) for 5 days. Changes in resting myocellular glycogen and phosphocreatine (PCr) were determined with Magnetic Resonance Spectroscopy (13C- and 31P-MRS, respectively). After CR-GP, the levels of intramyocellular glycogen increased from 147 +/- 13 (standard error) mmol x (kg wet weight(-1)) to 172 +/- 13 m mol x (kg wet weight)(-1), while it increased from 134 +/- 17 mmol x (kg wet weight)(-) to 182 +/- 17 mmol x (kg wet weight)(-1) after PL-GP; the increments in intramyocellular glycogen concentrations were not statistically different. The increment in the PCr/ATP ratio after CR-GP (+ 0.20 +/- 0.12) was significantly different compared to PL-GP (- 0.34 +/- 0.16) (p < 0.05). The present results do not support the hypothesis that Cr loading increases muscle glycogen storage.

Respiratory muscle endurance training reduces chronic neck pain: A pilot study.

BACKGROUND: Patients with chronic neck pain show also respiratory dysfunctions. OBJECTIVE: To investigate the effects of respiratory muscle endurance training (RMET) on chronic neck pain. METHODS: In this pilot study (single-subject design: 3 baseline measurements, 4 measurements during RMET), 15 neck patients (49.3 ± 13.7 years; 13 females) conducted 20 sessions of home-based RMET using a SpiroTiger® (normocapnic hyperpnoea). Maximal voluntary ventilation (MVV), maximal inspiratory (Pimax) and expiratory (Pemax) pressure were measured before and after RMET. Neck flexor endurance, cervical and thoracic mobility, forward head posture, chest wall expansion and self-assessed neck disability [Neck Disability Index (NDI), Bournemouth questionnaire] were weekly assessed. Repeated measure ANOVA (Bonferroni correction) compared the first and last baseline and the last measurement after RMET. RESULTS: RMET significantly increased MVV (p= 0.025), Pimax (p= 0.001) and Pemax (p< 0.001). During RMET, neck disability significantly decreased (NDI: p= 0.001; Bournemouth questionnaire: p= 0.002), while neck flexor endurance (p< 0.001) and chest wall expansion (p< 0.001) increased. The changes in respiratory and musculoskeletal parameters did not correlate. CONCLUSIONS: RMET emerged from this pilot study as a feasible and effective therapy for reducing disability in patients with chronic neck pain. The underlying mechanisms, including blood gas analyses, need further investigation in a randomized controlled study.

A fundamental problem in determining functional residual capacity or residual volume.

To measure a lung volume that is not directly accessible, one often follows dilution of a single-gas tracer, present initially only in the lung or in a rebreathing bag. The final volume available to the tracer is assumed to be the sum of the two initial components. Since O2 is taken up and CO2 is eliminated during the few breaths required for mixing, the total volume changes. The error in lung volume due to this volume change can exceed 10%. In this paper we 1) present theoretical and experimental data to demonstrate the effect of CO2 and O2 exchange, 2) introduce a general equation, based on N2 and Ar, which allows one to circumvent the problems created by these fluxes, and 3) show the pitfall of the back-extrapolation approach for a single tracer.

Effect of water immersion on cardiopulmonary physiology at high gravity (+Gz).

We compared the cardiopulmonary physiology of eight subjects exposed to 1, 2, and 3 Gz during immersion (35 degrees C) to the heart level with control dry rides. Immersion should almost cancel the effects of gravity on systemic circulation and should leave the lung alone to gravitational influence. During steady-state breathing we measured ventilation, O2 consumption (VO2), CO2 production, end-tidal PCO2 (PACO2), and heart frequency (fH). Using CO2 rebreathing techniques, we measured cardiac output, functional residual capacity, equivalent lung tissue volume, and mixed venous O2 content, and we calculated arterial PCO2 (PaCO2). As Gz increased, ventilation, fH, and VO2 rose markedly, and PACO2 and PaCO2 decreased greatly in dry ride, but during immersion these variables changed very little in the same direction. Functional residual capacity was lower during immersion and decreased in both the dry and immersed states as Gz increased, probably reflecting closure effects. Cardiac output decreased as Gz increased in dry rides and was elevated and unaffected by Gz during immersion. We conclude that most of the changes we observed during acceleration are due to the effect on the systemic circulation, rather than to the effect on the lung itself.

Respiratory phase detection and delay determination for breath-by-breath analysis.

The delay between air flow and gas concentration signals is generally assumed to be constant within a breath as well as from breath to breath, but it was not possible to examine the constancy of the delay with the delay determination techniques so far available. Thus we developed new methods for respiratory phase detection and delay determination. The presented algorithm for the detection of the start of inspiration and expiration (phase detection) replaces the generally used valve assembly with two pneumotachographs. Now, the pneumotachograph is used in a bidirectional mode, but with a volume criterion for phase detection replacing the less reliable threshold criterion. To measure the delay between flow and gas concentration signals, a test gas is periodically injected as a marker. This test gas contains less N2 than ambient air. Therefore, the delay is determined as time between the moment of injection and the drop of N2. These two methods rendered it possible to examine delay variations and their consequences. The investigation of various breathing patterns demonstrated that the usually assumed errors caused by delay uncertainty are underestimated. We suggest reliance on a breath-by-breath delay determination to account for delay variations.

Rate of erythropoietin formation in humans in response to acute hypobaric hypoxia.

This study was carried out to investigate the early changes in erythropoietin (EPO) formation in humans in response to hypoxia. Six volunteers were exposed to simulated altitudes of 3,000 and 4,000 m in a decompression chamber for 5.5 h. EPO was measured by radioimmunoassay in serum samples withdrawn every 30 min during altitude exposure and also in two subjects after termination of hypoxia (4,000 m). EPO levels during hypoxia were significantly elevated after 114 and 84 min (3,000 and 4,000 m), rising thereafter continuously for the period investigated. Mean values increased from 16.0 to 22.5 mU/ml (3,000 m) and from 16.7 to 28.0 mU/ml (4,000 m). This rise in EPO levels corresponds to 1.8-fold (3,000 m) and 3.0-fold (4,000 m) increases in the calculated production rate of the hormone. After termination of hypoxia, EPO levels continued to rise for approximately 1.5 h and after 3 h declined exponentially with an average half-life time of 5.2 h.

Respiratory muscle fitness and exercise endurance in healthy humans.

New evidence exists that the respiratory muscles may limit exercise performance in healthy humans. Four weeks of isolated respiratory training (30 min normocapnic hyperpnea, 5 d.wk-1 significantly increased the endurance time of respiratory muscles and the endurance time of constant-load bicycle tests in sedentary as well as physically active subjects once respiratory muscles had recovered from the training. Minute ventilation and blood lactate concentration were reduced during post-training exercise. Furthermore, respiratory trained subjects had lost the sensation of breathlessness. Maximal oxygen consumption was not affected by respiratory training. The mechanism by which respiratory training improves overall physical performance is as yet unknown.

Influence of endurance exercise on respiratory muscle performance.

PURPOSE: During high-intensity, exhaustive, constant-load exercise above 85% of maximal oxygen consumption, the diaphragm of healthy subjects can fatigue. Although a decrease in trans-diaphragmatic pressure is the most objective measure of diaphragmatic fatigue, possible extra-diaphragmatic muscle fatigue would not be detected by this method. The aim of the present study was to investigate the impact of exhaustive, constant-load cycling exercise at different intensities on global respiratory performance determined by the time to exhaustion while breathing against a constant resistance. METHODS: Ten healthy, male subjects performed an exhaustive cycling endurance test at 65, 75, 85, and 95% of peak oxygen consumption (VO2peak). Before cycling (to) as well as at 10 min (t10) and 45 min (t45) after cycling, respiratory performance was determined. RESULTS: Breathing endurance was equivalently reduced after exhaustive cycling at either 65% (8.4 +/- 4.1 min [t0] vs 3.9 +/- 2.8 min [t10]), 75% (9.9 +/- 6.1 vs 4.4 +/- 2.8 min), 85% (9.3 +/- 6.0 vs 3.8 +/- 2.9 min), or 95% VO2peak (8.5 +/- 5.1 vs 4.0 +/- 2.5 min) and, therefore, was independent of exercise intensity. CONCLUSION: This result contradicts previous findings, possibly due to the fact that extra-diaphragmatic muscles are tested in addition to the diaphragm during resistive breathing.

Noninvasive measurement of muscle high-energy phosphates and glycogen concentrations in elite soccer players by 31P- and 13C-MRS.

PURPOSE: The purpose of this study was to measure noninvasively the absolute concentrations of muscle adenosine triphosphate [ATP], phosphocreatine [PCr], inorganic phosphate (Pi), and glycogen [Gly] of elite soccer players. METHODS: Magnetic resonance spectroscopy (31P- and 13C-MRS) was used to measure the concentrations of metabolites in the calf muscles of 18 young male players [age = 17.5 +/- 1.0 (SD) yr]. RESULTS: Average muscle [PCr] and [ATP] were 17.8 +/- 3.3 and 6.0 +/- 1.2 mmol x (kg wet weight)(-1), respectively. The ratios of Pi/PCr and PCr/ATP were 0.15 +/- 0.05 and 3.00 +/- 0.26, respectively. The muscle [Gly] was 144 +/- 54 mmol x (kg wet weight)(-1). There was a high correlation (r = 0.93, P < 0.0001) between muscle ATP and PCr concentrations, but there was no correlation between [Gly] and [PCr] or [ATP]. The concentrations of the different metabolites determined in the present study with noninvasive MRS methods were within the ranges of values reported in human muscle from biochemical analysis of muscle biopsies. CONCLUSION: MRS methods can be utilized to assess noninvasively the muscle energetic status of elite soccer players during a soccer season. The high correlation between ATP and PCr might be indicative of fiber type differences in the content of these two metabolites.

Muscle glycogen degradation during simulation of a fatiguing soccer match in elite soccer players examined noninvasively by 13C-MRS.

PURPOSE: The purpose of this research project was to noninvasively determine individual muscle glycogen [Gly] degradation during a test intended to predict individual fatigue in intense soccer matches. METHODS: The [Gly] of the calf muscles of 17 elite soccer players [age = 17.4 +/- 0.8 (SD)] were measured with 13C-MRS before and after an alternating velocity test to exhaustion. Blood samples were taken before and 3 min after the test for determination of blood metabolites. RESULTS: Average muscle [Gly] was 135 +/- 53 mmol x (kg wet weight)(-1) before and 87 +/- 27 mmol x (kg wet weight)(-1) (P < 0.001) after exhaustion (42 +/- 25 min). There was a high correlation (r = 0.87, P < 0.0001) between muscle [Gly] at rest and net muscle [Gly] utilized. There was also a more moderate correlation (r = 0.62, P < 0.01) between net muscle [Gly] used and time to exhaustion during the soccer-specific test. There was some evidence of correlation (r = 0.42, P = 0.09) between resting [Gly] and time to exhaustion. Plasma lactate increased (P < 0.001) from 0.8 +/- 0.4 before the test to 2.5 +/- 1.0 mmol x L(-1) at exhaustion, whereas ammonia was raised (P < 0.0001) from 44.1 +/- 10.3 to 89.7 +/- 14.9 micromol x L(-1). Similarly, plasma free fatty acids were elevated (P < 0.0001) from 148 +/- 106 to 797 +/- 401 micromol x L(-1), and glycerol was increased (P < 0.0001) from 48.3 +/- 17.7 to 182.2 +/- 61.8 micromol x L(-1). Insulin levels (11.9 +/- 3.7 vs 11.7 +/- 4.8 microU x mL(-1)) remained the same. Creatine kinase levels increased (P < 0.0001) from 486 +/- 501 to 640 +/- 548 micromol x L(-1) after the test. CONCLUSIONS: We conclude that exhaustion during soccer-specific performance is related to the capacity to utilize muscle [Gly]. The results underline the importance of dietary counseling (glycogen loading and resynthesis strategies) and proper training to enhance the glycogen levels and glycogenolytic capacity of the players.

[Physiological basis for the measurement of aerobic capacity]. / Physiologische Grundlagen zur Messung der aeroben Leistungsfähigkeit.

Aerobic capacity should be determined from the anaerobic threshold and not from VO2max. The measurement of the anaerobic threshold via heart rate, introduced 1982 by Conconi et al. (3) and meanwhile improved, seems to be of practical value, although a number of fundamental questions remain open. A great advantage is its simple use when compared with the more complicated laboratory methods (respiratory or lactate curves). The determination of the anaerobic threshold based on the heart rate allows, in addition, to optimize the endurance training owing to the help of heart rate control.

Respiratory dysfunction in patients with chronic neck pain - influence of thoracic spine and chest mobility.

Patients with chronic neck pain exhibit various musculoskeletal deficits and respiratory dysfunction. As there is a link between thoracic and cervical spine motion, the aim of this study was to investigate the relationship between thoracic spine and chest mobility with respiratory function and neck disability. Nineteen patients with chronic neck pain (7 male, 46.6 ± 10.5 years) and 19 healthy subjects (7 male, 46.5 ± 9.9 years) participated. Spirometry was conducted to determine maximal voluntary ventilation (MVV), maximal inspiratory (Pimax) and maximal expiratory pressure (Pemax). Thoracic spine mobility was measured using the Spinal Mouse(®). Chest expansion was assessed by subtracting chest circumference during maximal inspiration and expiration. Neck function was investigated by examining range of motion, forward head posture, neck flexor muscle synergy endurance and self-assessment (Neck disability index (NDI)). Correlation analyses and multiple linear regression analyses were conducted using MVV, Pimax and Pemax as independent variables. Thoracic spine mobility during flexion and chest expansion correlated significantly to MVV (r = 0.45 and 0.42), all neck motions (r between 0.39 and 0.59) and neck muscle endurance (rS = 0.36). Pemax and Pimax were related to NDI (r = -0.58 and -0.46). In the regression models, chest expansion was the only significant predictor for MVV, and Pemax was determined by neck muscle endurance. These results suggest that chronic neck pain patients should improve the endurance of the neck flexor muscles and thoracic spine and chest mobility. Additionally, these patients might benefit from respiratory muscle endurance training, possibly by increasing chest mobility and Pemax.

[Nutrition in long physical endurance events]. / Ernährung bei Langzeitausdauerleistungen.

In recent years, there was a trend towards longlasting endurance events. The longer the competitions last, the more important nutrition and fluid replacement will be before, during, and after a race, because an inadequate supply reduces performance. Therefore, we summarize in this review the importance of carbohydrate and fat as well as the substitution of water and electrolytes concerning races of more than 4 hours duration.

The respiratory system as an exercise limiting factor in normal sedentary subjects.

The present study was undertaken to investigate the respiratory system as an exercise limiting factor. Breathing and cycle endurance (i.e. the time until exhaustion at a given performance level) as well as physical working capacity 170 (i.e. the exercise intensity corresponding to a heart rate of 170 beats.min-1 on a cycle ergometer) were determined in four healthy sedentary subjects. Subsequently, the subjects trained their respiratory system for 4 weeks by breathing daily about 90 l.min-1 for 30 min. Otherwise they continued their sedentary lifestyle. Immediately after the respiratory training and 18 months later, all performance tests carried out at the beginning of the study were repeated. The respiratory training increased breathing endurance from 4.2 (SD 1.9) min to 15.3 (SD 3.8) min. Cycle endurance was improved from 26.8 (SD 5.9) min to 40.2 (SD 9.2) min whereas physical working capacity 170 remained essentially the same. During the endurance cycling test in the respiratory untrained state, the subjects continuously increased their ventilation up to hyperventilation [ventilation at exhaustion = 96.9 (SD 23.6) l.min-1] while after the respiratory training they reached a respiratory steady-state without hyperventilation [ventilation at exhaustion = 63.3 (SD 14.5) l.min-1]. The absence of this marked hyperventilation was the cause of the impressive increase of cycle endurance in normal sedentary subjects after respiratory training. The effects gained by the respiratory training were completely lost after 18 months. Our results indicated that the respiratory system was an exercise limiting factor during an endurance test in normal sedentary subjects.

Effects of aerobic and anaerobic training on plasma lipoproteins.

We studied the effects of anaerobic and aerobic training on lipoprotein concentrations in 45 healthy untrained men. Thirty-three subjects exercised four times per week during nine weeks on a bicycle ergometer. Sixteen trained with an intensity above the anaerobic threshold (blood lactate concentration > 4 mmol.l-1) and 17 trained with an intensity below the anaerobic threshold. In addition, twelve subjects served as controls. The calculated caloric expenditure of the two training groups was similar. In all three groups, total cholesterol, total high-density lipoprotein (HDL), HDL subfractions (HDL2, HDL3), and low-density lipoprotein (LDL) were measured. Training had a significant influence on HDL, HDL2, LDL/HDL, HDL2/HDL3, and cholesterol/HDL. With anaerobic training these variables changed in the opposite direction compared with aerobic training which influenced the lipoprotein profile in the desired direction. Cholesterol, HDL3, and LDL did not alter during the nine weeks of training. After nine weeks of training, the higher the blood lactate concentration during exercise (representing training intensity) was, the higher resting LDL/HDL ratio was found. The correlation between these two variables was highly significant. We conclude that training above the anaerobic threshold has no or even negative effects on blood lipoprotein profiles. Therefore, beneficial adaptations in lipoprotein profile must be achieved with moderate training intensities below the anaerobic threshold.

Propranolol and the respiratory, circulatory, and ECG responses to high altitude.

The role of the sympatho-adrenal system in the acute respiratory and cardiovascular responses to high altitude was studies in 20 volunteers during ascent to 6,000 m in a low pressure chamber, once without (control) and once with beta-adrenergic blockade. Special attention was paid to the hypoxia-induced ECG changes. Propranolol lowered the level of hypoxia-induced cardiovascular reactions, whereas it had no effect on hypoxic hyperventilation and alveolar gases. At altitude, ECG changes during myocardial depolarization occurred in both the propranolol and the control groups, probably due to the direct effects of hypoxia. During the repolarization phase, propranolol led to an almost complete abolition of S-T depression and to significant reduction of T wave flattening. The minor but still significant flattening of the T wave as well as the relative (to the heart rate) lengthening of Q-T is probably due to the direct effects of hypoxia. Propranolol abolishes or diminishes the signs of cardiac hypoxia by antagonizing the effects of catecholamine release and/or by reducing myocardial oxygen consumption, thus probable increasing the ability to withstand oxygen-want at altitude.

Influence of breathing frequency and tidal volume on cardiac output.

The aim of our experiment was to investigate the influence of increasing either breathing frequency or tidal volume on cardiac output (Q), in normocapnia. We measured Q with a CO2 rebreathing method in 6 men and 6 women in the sitting and the supine position, imposing different breathing patterns: in one set of experiments tidal volume was kept constant at 1 L while breathing frequency was randomly changed between 20, 30 and 40 breaths/min; in another breathing frequency was kept constant at 30 breaths/min while tidal volume was randomly altered between 1, 1.5 and 2 L. Switching from open circuit breathing to rebreathing (for measurement of Q) required no change in breathing pattern. From the beginning, CO2 was added to the inspired gas to maintain end-tidal FCO2 at 0.054, so as to obtain steady state conditions throughout the measurements. Q rose significantly when tidal volume was increased (938 ml/L rise in tidal volume when sitting, and 743 ml/L when supine). Breathing frequency had an insignificant effect (213 ml/10 breaths frequency increase when sitting and 142 ml/10 breaths when supine). The greater influence of ventilation on Q when sitting than when supine is best explained by the fact that in the latter position venous return is already high. There are no demonstrable differences in this effect between males and females.