Analysis Of Intensity Distribution Research Articles

Elevated Aβ aggregates in feces from Alzheimer’s disease patients: a proof-of-concept study

BackgroundMisfolding and aggregation of amyloid β (Aβ), along with neurofibrillary tangles consisting of aggregated Tau species, are pathological hallmarks of Alzheimer’s disease (AD) onset and progression. In this study, we hypothesized the clearance of Aβ aggregates from the brain and body into the gut.MethodsTo investigate this, we used surface-based fluorescence intensity distribution analysis (sFIDA) to determine the Aβ aggregate concentrations in feces from 26 AD patients and 31 healthy controls (HC).ResultsAβ aggregates were detectable in human feces and their concentrations were elevated in AD patients compared to HC (specificity 90.3%, sensitivity 53.8%).ConclusionThus, fecal Aβ aggregates constitute a non-invasive biomarker candidate for diagnosing AD. Whether digestion-resistant Aβ aggregates in feces are secreted via the liver and bile or directly from the enteric neuronal system remains to be elucidated.

IAPP - oligomerisation levels in plasma of people with type 2 diabetes

Islet amyloid polypeptide (IAPP) is co-secreted with insulin from pancreatic ß-cells. Its oligomerisation is regarded as disease driving force in type 2 diabetes (T2D) pathology. Up to now, IAPP oligomers have been detected in affected tissues. IAPP oligomer concentrations in blood have not been analysed so far. Using the IAPP single-oligomer-sensitive and monomer-insensitive surface-based fluorescence intensity distribution analysis (sFIDA) technology, levels of IAPP oligomers in blood plasma from healthy controls and people with T2D in different disease stages where determined. Subsequently, the level of IAPP oligomerisation was introduced as the ratio between the IAPP oligomers determined with sFIDA and the total IAPP concentration determined with ELISA. Highest oligomerisation levels were detected in plasma of people with T2D without late complication and without insulin therapy. Their levels stand out significantly from the control group. Healthy controls presented with the lowest oligomerisation levels in plasma. In people with T2D without complications, IAPP oligomerisation levels correlated with disease duration. The results clearly demonstrate that IAPP oligomerisation in insulin-naïve patients correlates with duration of T2D. Although a correlation per se does not identify, which is cause and what is consequence, this result supports the hypothesis that IAPP aggregation is the driving factor of T2D development and progression. The alternative and conventional hypothesis explains development of T2D with increasing insulin resistance causing exhaustion of pancreatic ß-cells due to over-secretion of insulin, and thus IAPP, too, resulting in subsequent IAPP aggregation and fibril deposition in the pancreas. Further experiments and comparative analyses with primary tissues are warranted.

Two-Temperature Analysis of Intensity Distribution in the Rovibronic Spectra of the CN Radical

Two-Temperature Analysis of Intensity Distribution in the Rovibronic Spectra of the CN Radical

Aβ oligomers peak in early stages of Alzheimer's disease preceding tau pathology.

Soluble amyloid beta (Aβ) oligomers have been suggested as initiating Aβ related neuropathologic change in Alzheimer's disease (AD) but their quantitative distribution and chronological sequence within the AD continuum remain unclear. A total of 526 participants in early clinical stages of AD and controls from a longitudinal cohort were neurobiologically classified for amyloid and tau pathology applying the AT(N) system. Aβ and tau oligomers in the quantified cerebrospinal fluid (CSF) were measured using surface-based fluorescence intensity distribution analysis (sFIDA) technology. Across groups, highest Aβ oligomer levels were found in A+ with subjective cognitive decline and mild cognitive impairment. Aβ oligomers were significantly higher in A+T- compared to A-T- and A+T+. APOEε4 allele carriers showed significantly higher Aβ oligomer levels. No differences in tau oligomers were detected. The accumulation of Aβ oligomers in the CSF peaks early within the AD continuum, preceding tau pathology. Disease-modifying treatments targeting Aβ oligomers might have the highest therapeutic effect in these disease stages. Using surface-based fluorescence intensity distribution analysis (sFIDA) technology, we quantified Aβ oligomers in cerebrospinal fluid (CSF) samples of the DZNE-Longitudinal Cognitive Impairment and Dementia (DELCODE) cohortAβ oligomers were significantly elevated in mild cognitive impairment (MCI)Amyloid-positive subjects in the subjective cognitive decline (SCD) group increased compared to the amyloid-negative control groupInterestingly, levels of Aβ oligomers decrease at advanced stages of the disease (A+T+), which might be explained by altered clearing mechanisms.

Intensity Distribution of Collegiate Cross-Country Competitions.

The primary purpose of the current investigation was to perform an intensity distribution analysis of a collegiate cross-country (CC) competition, with a secondary purpose to compare race times (RT) with modeled performance times (MPT). Participants completed an incremental treadmill test to determine gas exchange threshold (GET), while the three-minute all-out test was conducted on a 400 m outdoor track to determine critical velocity (CV) and D prime (D'). GET and CV were used as physiological markers for the intensity zones based on heart rate (HR) and running velocity (RV), while CV and D' were used to determine modeled performance times. Participants wore a Global Positioning System (GPS) watch and heart rate (HR) monitor during competition races. Statistically, less time was spent in HR Zone 1 (12.1% ± 13.7%) compared to Zones 2 (37.6% ± 30.2%) and 3 (50.3% ± 33.7%), while a statically greater amount of time was spent in RV Zone 2 (75.0% ± 20.7%) compared to Zones 1 (8.4% ± 14.0%) and 3 (16.7% ± 19.1%). RTs (1499.5 ± 248.5 seconds (s)) were statistically slower compared to MPTs (1359.6 ± 192.7 s). The observed differences in time spent in each zone are speculated to be related to the influence of environmental conditions on internal metrics and difference in the kinetics of HR and running velocity. Differences in RTs and MPTs are likely due to the MPT equation modeling all-out performance and not considering race strategies.

An umbrella-inspired snap-on robotic 3D photoacoustic endoscopic probe for augmented intragastric sensing: Proof of concept study

In this paper, we present a novel on-demand modular robotic photoacoustic tomography (PAT) probe integrated into an endoscopic device, potentially for deep intragastric sensing. The proposed solution offers a plug-and-play approach through the use of meso-scale steerable endoscopy and a new ‘snap-on’ 3D robotic PAT probe that can reconfigure the geometry of the intracorporeal light delivery, inspired by an umbrella structure. Specifically, using the limited esophageal access, steerable endoscopy allows navigation and advancement of a distally mounted robotic add-on for PAT that is folded until it reaches the deep-seated gastric lesion. Once the tip is positioned near the lesion site in the gastric cavity, there is ample working space for the robotic probe to adjust its umbrella-like unfolded shape. This allows fine-tuning of the laser delivery orientation of the fiber bundles to achieve the lesion-specific light delivery scheme. This design allows volumetric imaging of the intragastric PAT with enhanced sensitivity. To evaluate the performance of the modular robotic PAT probe, we performed a simulation analysis of the light intensity and ultrasound field distribution. The simulation results show that the robotic probe is feasible for intracorporeal PAT imaging. In addition, we printed a 3D model of a human stomach containing a simulated gastric tumour. Both the phantom and ex vivo experimental results validate the feasibility of the proposed robotic PAT probe.

Disrupted-in-schizophrenia 1 protein aggregates in cerebrospinal fluid are elevated in patients with first-episode psychosis.

The disrupted-in-schizophrenia 1 (DISC1) protein is a key regulator at the intersection of major signaling pathways relevant for adaptive behavior. It is prone to posttranslational changes such as misassembly and aggregation but the significance of such transformations for human mental illness has remained unclear. We aimed to demonstrate the occurrence of DISC1 protein aggregates in patients with first-episode psychosis (FEP). Cerebrospinal fluid samples of patients with FEP (n = 50) and matched healthy controls (HCs; n = 47) were measured by the highly sensitive surface-based fluorescence intensity distribution analysis technology that enables single aggregate detection. We demonstrate that DISC1 protein aggregates are increased in cerebrospinal fluid samples of patients with FEP versus HCs. The concentration was in the low femtomolar range. No correlations were found with specific symptom levels, but the difference was particularly significant in the subset of patients with the diagnoses schizophrenia, unspecified (DSM-IV 295.9) or schizoaffective disorder (DSM-IV 295.70) at 18-month follow-up. DISC1 protein aggregate levels did not significantly change within the 18-month observation interval and were on average higher for individuals carrying the major DISC1 rs821577 allele, before correction. The occurrence of protein aggregates in vivo in patients with psychotic disorders has not been previously reported. It underscores the significance of posttranslational modifications of proteins both as pathogenetic mechanisms and as potential diagnostic markers in these disorders.

Development and Implementation of an Internal Quality Control Sample to Standardize Oligomer-Based Diagnostics of Alzheimer's Disease.

Protein misfolding and aggregation are pathological hallmarks of various neurodegenerative diseases. In Alzheimer's disease (AD), soluble and toxic amyloid-β (Aβ) oligomers are biomarker candidates for diagnostics and drug development. However, accurate quantification of Aβ oligomers in bodily fluids is challenging because extreme sensitivity and specificity are required. We previously introduced surface-based fluorescence intensity distribution analysis (sFIDA) with single-particle sensitivity. In this report, a preparation protocol for a synthetic Aβ oligomer sample was developed. This sample was used for internal quality control (IQC) to improve standardization, quality assurance, and routine application of oligomer-based diagnostic methods. We established an aggregation protocol for Aβ1-42, characterized the oligomers by atomic force microscopy (AFM), and assessed their application in sFIDA. Globular-shaped oligomers with a median size of 2.67 nm were detected by AFM, and sFIDA analysis of the Aβ1-42 oligomers yielded a femtomolar detection limit with high assay selectivity and dilution linearity over 5 log units. Lastly, we implemented a Shewhart chart for monitoring IQC performance over time, which is another important step toward quality assurance of oligomer-based diagnostic methods.

Enhancing Power Transmission Stability of AUV’s Wireless Power Transfer System with Compact Planar Magnetic Coupler

In this paper, a wireless power transfer (WPT) system with a compact planar magnetic coupler for an autonomous underwater vehicle (AUV) is proposed. A passive induction (PI) coil is integrated into the circular transmitter (Tx) coil to build a uniform magnetic field (UMF), which can guarantee the stable output of the WPT system under uncertain radial and axial misalignments for AUV. Based on normalized magnetic induction intensity distribution analysis, a UMF constructing method with a PI coil is given, aiming to eliminate the fluctuation of magnetic field intensity, and the PI coil design principles and flow chart are obtained. The theoretical analysis shows the proposed integrated coil can effectively enhance the radial misalignment tolerance compared with a conventional circular spiral coil. The zero-phase angle (ZPA) input condition can be achieved by adjusting the series capacitor connected with the Tx coil in S-S compensation topology. Experimental results show that the proposed magnetic coupler containing an integrated coil significantly improves the stability of output power and power transfer efficiency within the possible radial and axial misalignments compared with a conventional coupler. It was demonstrated that the output power changes less than 5.5% and the power transfer efficiency maintains at approximately 84.5% in arbitrary radial positions within the possible working region with an axial transfer distance of 50 mm in saltwater.

CBCT Images to an STL Model: Exploring the "Critical Factors" to Binarization Thresholds in STL Data Creation.

In-house fabrication of three-dimensional (3D) models for medical use has become easier in recent years. Cone beam computed tomography (CBCT) images are increasingly used as source data for fabricating osseous 3D models. The creation of a 3D CAD model begins with the segmentation of hard and soft tissues of the DICOM images and the creation of an STL model; however, it can be difficult to determine the binarization threshold in CBCT images. In this study, how the different CBCT scanning and imaging conditions of two different CBCT scanners affect the determination of the binarization threshold was evaluated. The key to efficient STL creation through voxel intensity distribution analysis was then explored. It was found that determination of the binarization threshold is easy for image datasets with a large number of voxels, sharp peak shapes, and narrow intensity distributions. Although the intensity distribution of voxels varied greatly among the image datasets, it was difficult to find correlations between different X-ray tube currents or image reconstruction filters that explained the differences. The objective observation of voxel intensity distribution may contribute to the determination of the binarization threshold for 3D model creation.

Patients with isolated REM-sleep behavior disorder have elevated levels of alpha-synuclein aggregates in stool

Misfolded and aggregated α-synuclein is a neuropathological hallmark of Parkinson’s disease (PD). Thus, α-synuclein aggregates are regarded as a biomarker for the development of diagnostic assays. Quantification of α-synuclein aggregates in body fluids is challenging, and requires highly sensitive and specific assays. Recent studies suggest that α-synuclein aggregates may be shed into stool. We used surface-based fluorescence intensity distribution analysis (sFIDA) to detect and quantify single particles of α-synuclein aggregates in stool of 94 PD patients, 72 isolated rapid eye movement sleep behavior disorder (iRBD) patients, and 51 healthy controls. We measured significantly elevated concentrations of α-synuclein aggregates in stool of iRBD patients versus those of controls (p = 0.024) or PD patients (p < 0.001). Our results show that α-synuclein aggregates are excreted in stool and can be measured using the sFIDA assay, which could support the diagnosis of prodromal synucleinopathies.

Focus in numbers: Characterizing protein oligomerization dynamics at DNA double strand breaks.

During radiotherapy, ionizing radiation (IR) is used to kill cancer cells by directly inducing high levels of genotoxic DNA double-strand breaks (DSB). These breaks are quickly detected and bound by DNA damage sensor proteins that activate a cascade of events leading to the recruitment and accumulation of repair factors (e.g. 53BP1) at sites of damage in dot-like structures called foci. The balance and interplay between the plethora of proteins recruited at the break site determine the choice of the repairing pathway, which can have paramount consequences on cell fate and ultimately in the response to cancer radiotherapy. Indeed, substantial evidence indicates that enhanced DSB repair (DSBR) capacity in individual patients is a major determinant in tumour radioresistance, while both radiosensitivity and the occurrence of radiotherapy-induced secondary cancers, are presumably associated with reduced DSBR function. Therefore, there is a pressing need to better understand the fundamental mechanisms of DSBR, towards improving the clinical management of patients undergoing radiotherapy. While it is clear that DNA repair relies on the balanced contribution of various repair factors, the oligomerization dynamics governing their organization into foci remain largely unknown. Here we combine Spatial Intensity Distribution Analysis (SpIDA) with an automated high-content foci detection algorithm to quantify the number of 53BP1 molecules at DSBR foci in cells challenged with increasing doses of the radiomimetic drug zeocin. Consistently with published data, 53BP1 foci number increases linearly at lower zeocin doses while plateauing at higher DNA damage load (zeocin concentration above 500 μg/mL). At this plateau, despite the availability of a nucleoplasmic protein pool, the number of 53BP1 molecules per focus decreases, suggesting a further not yet clarified layer of dynamic regulation potentially leverageable as therapeutical target.

Innovative Technologies in the Monitoring of the Age-Related Cataract

Literature review is devoted to modern high-technology instrumental methods of the lens evaluation, which have been developed to improve efficiency of the diagnostics and management of cataract in ophthalmological clinical practice. The slit-lamp examination of lens and retroillumination images are used for subjective assessment of cataract according to LOCS III grading system. Currently objective methods of lens evaluation have practical value and provide information about early age-related changes of crystalline lens with the quantitative assessment of the severity of opacities including the optical and ultrasound examinations. Optical methods include densitometry using Scheimpflug images obtained from applications to quantify the localization of lens opacities and their progression rate. Another method is the intensity distribution analysis of the wave front of the optical aberrations according to grading cataract severity with the objective scatter index (OSI) obtained by double-pass technology. Moreover the optical quantitative assessment of lens opacities is carried out by the Shack—Hartmann wave front sensor to identify the grade of nuclear opalescence (N-type) with the Lens Opacities Classification System III. This method is very helpful in nuclear cataract. Swept source optical coherent tomography (SS-OCT) with variable length of wave and high frequency detector is used for the density measurements of nuclear and cortical opacities of lens imaging in micro- and macro dimensional scale. Ultrasound biomicroscopy is the most informative ultrasonic diagnostic method for the evaluation of acoustic density and early age-related changes of lens. Current high-informative methods of quantitative assessment of the optical density of lens are helpful in determination of indications for surgery, the optimization of phacoemulsification settings and prevention of intraoperative complications. The use of high-technologic methods demonstrated the effectiveness of eye drops 0,005 % pirenoxine in early lens opacities management.

GisaxStudio—An Open Platform for Analysis and Simulation of GISAXS from 3D Nanoparticle Lattices

Grazing-incidence small-angle X-ray scattering (GISAXS) is a powerful method for the structural analysis of ordered arrays of nanoparticles, quantum dots, or similar objects. However, for the correct interpretation of the measured GISAXS intensity distributions, a proper data analysis, including a suitable model, is required. Here, we demonstrate a software platform, GisaxStudio, aimed at the analysis and simulation of 2D GISAXS intensity distributions from ordered lattices of different nanoparticles. It contains several models that satisfactorily describe the GISAXS from 3D lattices or crystals of nanoparticles prepared by the self-assembly processes, pre-pattering, or ion-beam interaction with the material within their tracks. It also supports different shapes of nanoparticles, including core-shell structure with the center of core possibly displaced from the center of the shell. The software is very useful for fast and accurate GISAXS data analysis.

Quantitative detection of α-Synuclein and Tau oligomers and other aggregates by digital single particle counting

The pathological hallmark of neurodegenerative diseases is the formation of toxic oligomers by proteins such as alpha-synuclein (aSyn) or microtubule-associated protein tau (Tau). Consequently, such oligomers are promising biomarker candidates for diagnostics as well as drug development. However, measuring oligomers and other aggregates in human biofluids is still challenging as extreme sensitivity and specificity are required. We previously developed surface-based fluorescence intensity distribution analysis (sFIDA) featuring single-particle sensitivity and absolute specificity for aggregates. In this work, we measured aSyn and Tau aggregate concentrations of 237 cerebrospinal fluid (CSF) samples from five cohorts: Parkinson’s disease (PD), dementia with Lewy bodies (DLB), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP), and a neurologically-normal control group. aSyn aggregate concentration discriminates PD and DLB patients from normal controls (sensitivity 73%, specificity 65%, area under the receiver operating curve (AUC) 0.68). Tau aggregates were significantly elevated in PSP patients compared to all other groups (sensitivity 87%, specificity 70%, AUC 0.76). Further, we found a tight correlation between aSyn and Tau aggregate titers among all patient cohorts (Pearson coefficient of correlation r = 0.81). Our results demonstrate that aSyn and Tau aggregate concentrations measured by sFIDA differentiate neurodegenerative disease diagnostic groups. Moreover, sFIDA-based Tau aggregate measurements might be particularly useful in distinguishing PSP from other parkinsonisms. Finally, our findings suggest that sFIDA can improve pre-clinical and clinical studies by identifying those individuals that will most likely respond to compounds designed to eliminate specific oligomers or to prevent their formation.

The analysis of pressure drop, spray angle, and sprinkling intensity distribution in the spray stream produced by the water-foam nozzle

Abstract This paper summarises a series of large-scale fire suppression tests conducted to simulate a fire in the big surface and/or surface sprinkling. The subject of this paper is the research on water spraying with the use of the Turbo Jet 2011 water-foam nozzle manufactured by Supon Białystok. The results discuss the pressure losses caused by the flow through the discharge hose, spray angle, and the intensity of surface sprinkling. The greatest stream ranges and the highest maximum values of the sprinkling intensity were obtained at the capacity of 400 l/min, and a solid spray angle. The smallest values were obtained at 200 l/min, a pressure of 5 bar, and a solid spray angle. The actual pressures taking into account the losses in the hose section were calculated. As for the highest firefighting effectiveness of the stream, the authors recommended the following parameters: semi spray angle, 200 l/min, and 2.5 bar.

Aβ oligomer concentration in mouse and human brain and its drug-induced reduction ex vivo

SummaryThe elimination of amyloid beta (Aβ) oligomers is a promising strategy for therapeutic drug development of Alzheimer’s disease (AD). AD mouse models that develop Aβ pathology have been used to demonstrate in vivo efficacy of compounds that later failed in clinical development. Here, we analyze the concentration and size distribution of Aβ oligomers in different transgenic mouse models of AD and in human brain samples by surface-based fluorescence intensity distribution analysis (sFIDA), a highly sensitive method for detecting and quantitating protein aggregates. We demonstrate dose- and time-dependent oligomer elimination by the compound RD2 in mouse and human AD brain homogenates as sources of native Aβ oligomers. Such ex vivo target engagement analyses with mouse- and human-brain-derived oligomers have the potential to enhance the translational value from pre-clinical proof-of-concept studies to clinical trials.

Increasing the measurement accuracy for wave aberrations of an optical system using the intensity distribution of a focused light beam

Subject of study. A method for enhancing the measurement accuracy for wave aberrations of an optical system by using cross-section images of a focused light beam in the presence of the image’s amplitude distortions is described. Method. The measurement procedure includes determining the wave aberrations of the optical system individually for each of the beam cross-section images recorded at different sides from the focal plane and subsequently averaging the obtained wave aberrations. Main results. The utilized method for obtaining the wave aberrations of an optical system involves analysis and processing of the aberration-distorted intensity distributions in the cross-section images of a focused light beam that are recorded in a plane before and after the focal plane. Noticeably, the presence of intensity nonuniformities in the light beam cross-sections that do not result from the wave aberrations inevitably causes measurement errors. The effect of such amplitude noise on the measurement accuracy can be suppressed manifold by recording and processing an additional image of the beam cross-section positioned at a particularly selected distance on the opposite side to the focusing plane. This is followed by averaging the wave aberrations obtained for each of these images. If the amplitude and aberrational distortions of the intensity distribution have similar profiles in one of the recording planes, they are added, and they increase the degree of nonuniformity of the total intensity distribution. However, the profiles of the amplitude and aberrational distortions of the intensity distribution in the other plane are mutually opposite, which reduces the degree of distribution nonuniformity. This effect allows the measurement errors caused by amplitude noise to be compensated by arithmetically averaging the wave aberrations obtained individually for each image. We demonstrate that the variation in the measured values of the root mean square deviation of the wave front of the beam of up to 20%–30% from the individual measurements of the wave aberrations in the presence of noise can be reduced to several percent using the proposed method. Practical significance. Amplitude distortions in the images of the cross-sections of a beam that are not caused by aberrations are ubiquitous because they are present in, e.g., high-aperture, apodized, or off-axis optical systems. Measurement of the wave aberrations of such optical systems by the standard method using one image of a focused beam does not provide accurate results. The modification of this measurement technique proposed in this paper enables the extension of its application area to the aforementioned systems while maintaining its characteristic measurement accuracy at λ/20.

Initial experience with intensity distribution analysis of hemodynamic parameters in the thoracic aorta using four-dimensional magnetic resonance imaging

The purpose of this study was to investigate whether there were significant differences in the intensity distributions of thoracic aorta hemodynamic parameters between groups with different ejection fractions (EF) using four-dimensional flow magnetic resonance imaging and to investigate the relationships between each parameter.A total of 26 patients, 13 each with EF of >60% and <30%, underwent cardiac four-dimensional flow magnetic resonance imaging (EF >60%: mean age: 54 ± 11.6 years, EF <30%: mean age: 49.2 ± 17.2 years). The thoracic aorta was divided into the proximal and distal ascending aorta (AAo), aortic arch, and the proximal and distal descending aorta, and each section was further divided into the anterior wall, posterior wall, lesser curvature, and greater curvature. The intensity distributions of wall shear stress (WSS), energy loss (EL), and vorticity (Vort) (hemodynamic parameters) and the concordance rates between these distributions were analyzed.The concordance rate between the intensity distributions of EL and Vort was high. Only the intensity distributions of EL and Vort in the distal AAo differed significantly between the groups (P < .001). In the EF >60% group, these intensity distributions showed higher values in the greater curvature of the AAo, whereas in the EF <30% group higher values were seen in the lesser curvature of the AAo.Although there was no significant intergroup difference in the WSS intensity distribution, in the EF <30% group the WSS intensity distribution tended to exhibit higher values in the lesser curvature of the distal AAo, and the WSS intensity distribution values for the greater curvature tended to gradually increase from the arch to the proximal descending aorta.The only significant differences between the EF groups were found in the intensity distributions of EL and Vort in the distal AAo. This suggests that the distributions of atherosclerosis may be EF-dependent.

Retrospective Analysis of Training Intensity Distribution Based on Race Pace Versus Physiological Benchmarks in Highly Trained Sprint Kayakers

BackgroundResearch results on the training intensity distribution (TID) in endurance athletes are equivocal. This non-uniformity appears to be partially founded in the different quantification methods that are implemented. So far, TID research has solely focused on sports involving the lower-body muscles as prime movers (e.g. running). Sprint kayaking imposes high demands on the upper-body endurance capacity of the athlete. As there are structural and physiological differences between upper- and lower-body musculature, TID in kayaking should be different to lower-body dominant sports. Therefore, we aimed to compare the training intensity distribution during an 8-wk macrocycle in a group of highly trained sprint kayakers employing three different methods of training intensity quantification.MethodsHeart rate (HR) and velocity during on-water training of nine highly trained German sprint kayakers were recorded during the final 8 weeks of a competition period leading to the national championships. The fractional analysis of TID was based on three zones (Z) derived from either HR (TIDBla-HR) or velocity (TIDBla-V) based on blood lactate (Bla) concentrations (Z1 ≤ 2.5 mmol L−1 Bla, Z2 = 2.5–4.0 mmol L−1 Bla, Z3 ≥ 4.0 mmol L−1 Bla) of an incremental test or the 1000-m race pace (TIDRace): Z1 ≤ 85% of race pace, Z2 = 86–95% and Z3 ≥ 95%.ResultsTIDBla-V (Z1: 68%, Z2: 14%, Z3: 18%) differed from TIDBla-HR (Z1: 91%, Z2: 6%, Z3: 3%) in each zone (all p < 0.01). TIDRace (Z1: 73%, Z2: 20%, Z3: 7%) differed to Z3 in TIDBla-V (p < 0.01) and all three TIDBla-HR zones (all p < 0.01). Individual analysis revealed ranges of Z1, Z2, Z3 fractions for TIDBla-HR of 85–98%, 2–11% and 0.1–6%. For TIDBla-V, the individual ranges were 41–82% (Z1), 6–30% (Z2) and 8–30% (Z3) and for TIDRace 64–81% (Z1), 14–29% (Z2) and 4–10% (Z3).ConclusionThe results show that the method of training intensity quantification substantially affects the fraction of TID in well-trained sprint kayakers. TIDRace determination shows low interindividual variation compared to the physiologically based TIDBla-HR and TIDBla-V. Depending on the aim of the analysis TIDRace, TIDBla-HR and TIDBla-V have advantages as well as drawbacks and may be implemented in conjunction to maximize adaptation.