Critical Intensity Level Research Articles

Peculiarities of Aerobic Development in Kayak Rowers Preparing for 1000 m Event

Research background and hypothesis. Lithuanian scientific publications mostly deal with kayak rowers’ preparation for 200 and 500 m events, while 1000 m event is hardly analyzed yet. Research aim was to project scientifically based program of kayak rowers’ preparation for 1000 m event, which is to develop aerobic capacity in different mezo-cycles, and to evaluate its efficiency.Research methods. Preparation of kayak doubles crew members was investigated; the athletes were the 5 th place winners of 2013 World Cup II event. The carried out training load for aerobic capacity development was divided into 5 zones of intensity. During training sessions, computer program Garmin Connect measured the distance and speed of a boat, as well as athletes’ heart rate (HR). Athletes’ aerobic capacity at critical intensity level (CIL) and anaerobic threshold (ANT) was established using gas analyser ‘Oxycon Mobile’. Research results. As the research showed, the kayak rowers in mezzo-cycles of both preparatory and competition periods carried out very little training load in the fifth zone of intensity. Considerable is also the fact that during competition period, in mezzo-cycle, the total number of kilometres decreased from 218 to 158 km. Discussion and conclusions. The research demonstrated that training workloads in the first and the second zones for elite kayak rowers preparing for 1000 m event in the first mezzo-cycle of competitive period were diminished comparing to the workload carried out in the preparatory period, while the amount of workload in the fourth zone was considerably increased. Adaptation of the two elite athletes to applied training loads is different, although they were following the same program. Due to this fact, the training process of those athletes is recommended to be given more individual approach, though they are rowing one boat.Keywords: kayak rowing, preparatory and competitive periods, training mezzo-cycles, aerobic capacity.

Intervalinio didelio intensyvumo treniruočių metodo taikymo veiksmingumas didinant baidarininkų aerobinį metabolizmą

Interval training method is used as one of the means of training methods among various other methods, applied for athletes’ training in different sports. H. Reindel, H. Roskamm (1959) were the first having put a highlight on this training method in a scientific literature. In 1960, I. Astrand et al. provided detailed studies on the impact of interval training method on O2 intake (VO2), pulse rate (PR), blood lactate (La) concentration and other physiological processes in athletes’ body when performing different workouts bearing the interval character. H. Reindell et al. (1962) used to analyse the physiological essence of interval workouts and grounded the practical use of them in developing athletes’ aerobic capacity, i.e., ability of muscles to use O2, as well as functional capacity of blood respiratory system. Lately, increased attention was paid to interval workouts when combining intense work of short-term with that of low intensity. However, there is a shortage of investigations dealing with the body changes caused by interval workouts, applied in the process of elite kayak rowers. It is of paramount importance to identify the change of oxygen intake intensity in kayak rowers’ working muscles, as well as the differences of oxygenation in the workouts of different duration and intensity. The aim of the work was to explore and compare the effect of high intensity interval and repeated training workouts on muscles’ aerobic metabolism in elite kayak rowers. Organization and methods of the research. Two elite kayak rowers (aged 29 and 30) participated in the research. After 10 min warming-up, the athletes performed complex exercise, which consisted of repeated 6 min duration work of 80% intensity at second ventilation threshold (2VAT), which was followed by 6 min sitting at rest, and later on they carried out the workout of 6 min duration by the above mentioned intensity. Afterwards, after 6 min rest, they performed the interval workout of 6 min duration with 10 s intense work by 300 W power at the limits of critical intensity level (CIL) when VO2max is reached. Having performed this high intensity workout, the athletes had 30 s rest filled with light work, and after they repeated the workout overcoming the distance of high intensity. After a passive rest of 6 min, the athletes used to twice repeat the work at the same afore indicated intensity. Our research proved it to be effective in elite kayak rowers’ training an application of interval workouts with short (10–20 s) high intensity distances, aimed at the development of muscles aerobic metabolism. Under such conditions, muscles perform great mechanic work without acidifying body. It was found that general O2 consumption of kayak rowers during interval workouts is less comparing to the same work of the same duration by less intensity. VCO2 in exhaled air did not reach VO2 level in any case of the workouts. These indices were greater when performing 6 min duration distances evenly than using interval method. It appears to be purposeful to further investigate effectiveness of interval workouts aiming at expanding the possibilities in elite kayak rowers’ training. Keywords: kayak rowers, aerobic metabolism, muscles oxygenation, interval method. DOI: http://dx.doi.org/10.15823/sm.2018.7

Analysis of the impact of intracellular reactive oxygen species generation on the structural and functional integrity of human spermatozoa: lipid peroxidation, DNA fragmentation and effectiveness of antioxidants.

Exposure of human spermatozoa to nicotinamide adenine dinucleotide phosphate (NADPH) resulted in the dose dependent generation of reactive oxygen species (ROS) which, at a critical level of intensity, induced lipid peroxidation, DNA damage and a dramatic decline of sperm motility. This system was then used as a model for screening the ability of different antioxidants to combat oxidative stress created through the excessive intracellular generation of toxic oxygen products of metabolism. A variety of antioxidants that has previously been shown to be protective against extracellularly derived oxidants (e.g. superoxide dismutase, catalase, vitamin E, hypotaurine) were ineffective in this system. Albumin, however, could provide complete protection against NADPH induced oxidative stress via mechanisms that did not involve the suppression of the lipid peroxidation cascade but rather the inactivation of lipid peroxides generated during this process. Albumin did not protect against DNA damage induced by NADPH but was extremely effective at preventing DNA fragmentation arising from the suppression of glutathione peroxidase activity with mercaptosuccinate. These studies emphasize that the design of clinically effective antioxidant treatments will depend, critically, upon the source of the oxidative stress. For cases involving excessive intracellular ROS generation, albumin appears to be an important means of neutralizing lipid peroxide-mediated damage to the sperm plasma membrane and DNA.

An assessment of the relative importance of the components of CYVADIC in the treatment of soft-tissue sarcomas using regression meta-analysis.

The CYVADIC combination has enjoyed popular medical support for over a decade in the treatment of soft-tissue sarcomas, and there is much documented evidence in the literature of the relative success of this and related regimens. A multivariate regression meta-analysis has been undertaken of the collective experience of this group of regimens, to assess statistically the relative importance of each component of CYVADIC using the intensities of the four components to predict objective tumour response. This analysis demonstrates that the tumour response to a specific regimen may be reasonably predicted from an expression that is highly sensitive to the dacarbazine dose intensity, with a significant additional contribution being introduced by the level of vincristine administered. There is convincing statistical evidence that, when administered as part of a CYVADIC chemotherapeutic regimen, the presence of doxorubicin (with an intensity of about 0.8) will produce a significant optimal effect on tumour responses. In such situations there is no detected significant benefit from increasing the dose of doxorubicin beyond this critical level of intensity. These findings suggest that it is dacarbazine and not, as is customarily argued, doxorubicin that is the most sensitive component in the CYVADIC treatment of soft-tissue sarcomas. The veracity of this conclusion should be tested by prospective studies designed specifically to escalate the intensity of decarbazine treatment, whilst holding the level of doxorubicin at below standard intensity.

The Use of Microprocessor Technology for the Conditional Sampling of Intermittent Ocean Processes

Geophysical signals are often intermittent, having statistics which vary with time. Optimal sampling of these signals requires a so-called “conditional sampling” scheme, a technique which changes the sampling program to match the time scales of the processes of interest. To optimize the limited tape storage capacity of remote oceanographic instruments, a conditional sampling scheme has been implemented using the computational power of microprocessor-controlled instruments, and several deployments have been made with various configurations of the conditional sampling algorithm. This algorithm monitors short-term changes in the energy of an incoming signal within a designated high-frequency band (by digital filtering techniques) and compares the resulting intensity with the longer term statistics of the signal. If the energy exceeds an intensity defined as critical according to some criteria, then an “event” is declared and the data are recorded at a higher than normal rate for the duration of the event. When the statistics of the expected signals are not well known, and criteria cannot be predetermined with confidence, an “adaptive” technique is required whereby the instrument makes an in situ determination of the critical intensity level for each signal based on the statistics of that signal. Several deployments of the conditional sampling instruments have been made which demonstrate the operation of the technique. In Massachusetts Bay, a burst of high-frequency internal wave energy was identified and recorded by the adaptive critical algorithm applied to a moored temperature sensor array. On the northern California shelf, salinity was calculated in situ from moored temperature and conductivity sensors, and the resulting salinity time series conditionally sampled to identify salinity events as separate from temperature or pressure events. Conditional sampling techniques may not be optimum for exploratory work. However, where the processes and expected signals are intermittent and have a specific signature, then the use of a conditional sampling technique can make more efficient use of the limited storage capacity of remote instrumentation.

Some new aspects on damages in the organ of corti after pure tone exposure

(1) The loss of hair cells after pure tone exposure at the critical level of intensity shows an exact correlation to the frequency, the time of sound exposure, and time of recovery as regards the quality and quantity. (2) The total extent of the damage of sensory cells has to be estimated higher than the hair-cell loss as observed under the light microscope. Although an improvement of the function of the organ of Corti was determined electrophysiologically from the 5th to the 10th day of recovery, the hair-cell degeneration was progredient during this period. (3) The hair-cell damage is apically more strongly marked from the area of damage than basically. (4) Depending on the experimental conditions there are considerable degenerative alterations in the nerve fibres and in the connective apparatus of the organ of Corti besides hair-cell losses and damages.

Hair cell damage in the guinea pig due to different kinds of noise.

Guinea pigs were exposed in groups of five animals to intense pure-tones or impulse noise, where either the intensity or the exposure duration was varied. The damage to the inner ear was analysed histologically and the loss of outer hair cells was used as damage parameter. The intensity in the pure-tone experimets was varied from 102 to 120 dB sound pressure level. The hair cell damage was not increasing proportionally over the entire intensity range. Above a certain critical level of intensity the damages started to increase more rapidly. This could be explained by theories stating that different mechanisms are responsible for the damage below and above the critical level. When the animals were exposed to impulse noise and the duration of the exposure was doubled the hair cell damage was also doubled up to an exposure time of 24 hours. At longer durations the increase of the damage seemed to level off. Animals exposed to impulse noise for 6 hours and with an equivalent sound level of 102 dB showed slightly higher mean damages than animals exposed to a corresponding continuous pure-tone. The results indicate that the total energy concept is a too simplified hypothesis concerning inner ear damage.

Pulsating auroral patches exhibiting sudden intensity-dependent spatial expansion

A class of pulsating aurora has been observed in which the repeated spatial expansion of a patch from a small persistent core region is evidently dependent on the attainment of a critical intensity level in this core region. Characteristics of patches exhibiting this behavior are summarized and the phenomenon is discussed in relation to possible triggered instabilities of the precipitating electron beam.

Level of Isometric Strength and Isometric Endurance in Repeated Contractions

Abstract Thirty male subjects were given 20 trials of isometric wrist flexion on each arm. Each trial consisted of 5 sec. of maximum exertion followed by a 30 sec. rest period. Subjects were ranked on the basis of the first two trials for each of the limbs and divided into three groups of 10 subjects each representing high, middle, and low levels of strength. Analysis of variance of the fatigue curve trends suggested that: (a) there is no biologically fixed and constant absolute critical intensity level of isometric muscular tension which occludes intramuscular circulation, and (b) different levels of strength possess dissimilar local circulatory efficiency and/or tolerance to fatigue products.

A Unified Theory for Quantal Responses to Mixtures of Drugs: Competitive Action

Models for quantal responses to drugs acting competitively are considered. The models are derived by taking the model for graded responses developed largely by Gaddum and applying the principle that a quantal response occurs when an underlying graded response reaches a critical level of intensity. Dynamic equilibria, between the drugs and receptors in the tissues of the units of biological material, are assumed. Three cases occur:

CLINICAL STUDIES ON THE ACOUSTIC TRAUMA

The authors examined 101 cases who suffered from the inner ear deafness due to the exposure to intense sound especially from the viewpoint of its occurrence and progress of these cases.First the cases were classified into three groups according to the condition of the occurrence and progression. The deafness occurred very suddenly in 42 cases (first group) and slowly in 47 cases (second group) and the deafness occurred suddenly or slowly and it progressed for a long period after the cessation of the exposure in 12 cases (third group).Between these three groups the clear differences were noted in the clinical picture especially the bilaterality of the impairement, the shape of the audiogram and the grade of the hearing loss. In the first group, many cases showed the unilateral deafness or the bilateral deafness without symmetri- city but in the second and third group the cases showed dominantly the bilateral and symmetrical impairment. In the shape of audiogram, first group cases signify the variety of its appearance but in the second and third group the shapes of the high tone deafness was dominant. Further more from the viewpoint of the grade of the hearing impairment, the first group showed variety of impairment but in the second group most of the cases showed the hearing loss of below the 30 db level as the average of the speech range and in the third group the most cases showed the hearing loss of between 30 to 6C db level.These observations lead the authors to summa-rize the conclusions of this report as follows.(1) Three groups classified by the authors in this paper were assumed as three different manife-stations of three different injuring mechanism of the so-called acoustic trauma.(2) In the first group cases it is assumed that the sound is acting as a force and so it is very adequate to consider that the ear exposed to these intense sounds in accidents will always suffer from inner ear injuries.(3) In the second and third group cases the hereditary vulnerability must play a great role in the occurrence and progression of the deafness.(4) It is logical to assume that the second critical intensity level is the border line of the sound intensity that injures the inner ear as a force. (5) Sometimes the inner ear deafness due to the acoustic trauma will progress after the cessation of the exposure.

Reversible auditory fatigue resulting from exposure to a pure tone. I.

<h3>Introduction</h3> The obvious relationship between noise in industry and occupational deafness has resulted in considerable research being concentrated on the deafening effects of noise as measured by temporary threshold shift. As a result of this approach, the greater emphasis has fallen on the measurement of auditory fatigue resulting from exposure to intense sounds. The crucial question of the critical intensity level in effecting pathological damage to the ear has been answered only vaguely. Estimates of maximum noise levels to which the hearing organ may be exposed before suffering pathological trauma range between 80 and 100 db.^1-5 However, threshold shift has also been demonstrated for exposure to stimuli at low intensities in studies of auditory fatigue resulting from stimulation by pure tones. In recent experimental work on poststimulatory auditory fatigue, a differentiation between deafness due to traumatic stimulation by extremely loud sounds and a decrease in sensitivity due to stimulation