scholarly journals The Coefficient of Variation of Step Time Can Overestimate Gait Abnormality: Test-Retest Reliability of Gait-Related Parameters Obtained with a Tri-Axial Accelerometer in Healthy Subjects

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 577 ◽  
Author(s):  
Shunrou Fujiwara ◽  
Shinpei Sato ◽  
Atsushi Sugawara ◽  
Yasumasa Nishikawa ◽  
Takahiro Koji ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Intraclass Correlation ◽  
Step Length ◽  
Gait Parameter ◽  
Data Set ◽  
Gait Abnormality ◽  
Significant Difference ◽  
Assessment Time ◽  
The Difference ◽  
Gait Abnormalities

The aim of this study was to investigate whether variation in gait-related parameters among healthy participants could help detect gait abnormalities. In total, 36 participants (21 men, 15 women; mean age, 35.7 ± 9.9 years) performed a 10-m walk six times while wearing a tri-axial accelerometer fixed at the L3 level. A second walk was performed ≥1 month after the first (mean interval, 49.6 ± 7.6 days). From each 10-m data set, the following nine gait-related parameters were automatically calculated: assessment time, number of steps, stride time, cadence, ground force reaction, step time, coefficient of variation (CV) of step time, velocity, and step length. Six repeated measurement values were averaged for each gait parameter. In addition, for each gait parameter, the difference between the first and second assessments was statistically examined, and the intraclass correlation coefficient (ICC) was calculated with the level of significance set at p < 0.05. Only the CV of step time showed a significant difference between the first and second assessments (p = 0.0188). The CV of step time also showed the lowest ICC, at <0.50 (0.425), among all parameters. Test–retest results of gait assessment using a tri-axial accelerometer showed sufficient reproducibility in terms of the clinical evaluation of all parameters except the CV of step time.

scholarly journals Validity and reliability of badminton-specific Reactive Agility TestBadmintona özgü geliştirilen Reaktif Çeviklik Testinin geçerlik ve güvenirliği

2018 ◽  
Vol 15 (1) ◽  
pp. 594
Author(s):  
Mehmet Yıldız ◽  
Uğur Fidan
Keyword(s):  
Correlation Coefficient ◽  
Intraclass Correlation Coefficient ◽  
Linear Regression Analysis ◽  
Intraclass Correlation ◽  
T Test ◽  
Validity And Reliability ◽  
Test Protocol ◽  
Significant Difference ◽  
Reactive Agility ◽  
The Difference

Many laboratory and field tests are used in the literature to measure agility. The aim of the present study was to investigate the reliability and validity of a new Reactive Agility Test developed for badminton. A total of fourty male [ 20 elites (age: 20.8 ± 2.98 year, height: 174.55 ± 12.03 cm, weight: 65.70 ± 14.41 kg) and 20 sub-elites (age: 22.20±1,51, height: 170.01 ± 05.80 cm, weight: 62.45 ± 6,45 kg)] badminton players took part in the present study. For validity, the difference and relationship between newly developed reactive agility and planned changing direction tests in terms of elit and sub-elit players was examined. In the reliability measurements of test-retest, The Reactive Agility Test at same route was performed twice. Independent sample t test was carried out in order to detect the difference among the groups in the search for validity. The identification of the relations between the two different tests was performed with linear regression analysis. The reliability of test-retest was tried to be estimated with the coefficient of variances and intraclass correlation coefficient, and the Bland Altman method. In addition, a systematic difference between the test and the retest was estimated with the paired t test. At the end of the study, while there was not a significant difference found in the rates of planned changing direction of the elit and sub-elit players, it was detected that reactive agility rates were better in the elit players (7.14±4.85 sec and 9.87±5.07 sec, respectively). Moreover, a high coefficient determination was revealed between two tests (r2: 0.63, p<0.01). In the comparison of test-retest, a high intraclass correlation coefficient (0.930) and a very low coefficient of variances (4.7) were found. Furthermore, it was observed in the Bland Altman graph that a 95% of concordance range of the data obtained between two measurements was a good and narrow concordance.  In conclusion, it was determined that the new developed badminton specific Reactive Agility Test is a valid and reliable measurement method and it is suggested that this test protocol can be used to enhance and monitor reactive agility ability of badminton players.Extended English summary is in the end of Full Text PDF (TURKISH) file. ÖzetLiteratürde çevikliğin ölçülmesi amacıyla birçok laboratuvar ve saha testi kullanılmaktadır. Bu çalışmanın amacı badminton sporuna göre düzenlenmiş Reaktif Çeviklik Testinin güvenirlik ve geçerliğinin araştırılmasıdır. Araştırmaya toplam kırk erkek [20 elit (yaş: 20,8±2,98 yıl, boy uzunluğu: 174,55±12,03 cm, vücut ağırlığı:65,70±14,41 kg) ve 20 sub-elit (yaş: 22,20±1,51 yıl, boy uzunluğu: 170,01±05,80 cm, vücut ağırlığı:62,45±6,45 kg)] badminton oyuncusu katılmıştır. Geçerlik için yeni geliştirilen reaktif çeviklik ile planlı yön değiştirme testlerinin elit ve sub-elit katılımcılar arasındaki istatistiksel karşılaştırması ve ilişkisi analiz edilmiştir. Test-tekrar test güvenirlik ölçümlerinde aynı rotadaki reaktif çeviklik testi birer gün arayla iki kez uygulanmıştır. Geçerlik çalışmasında gruplar arası farkın belirlenmesi için bağımsız değişken t testi ve testler arası ilişkinin fonksiyonel olarak açıklanması ve bu ilişkinin bir modelle tanımlanması için basit doğrusal regresyon analizi yapılmıştır. Test-tekrar test güvenirliği varyasyon katsayısı, sınıf içi korelasyon katsayısı ve Bland Altman metodu ile kestirim edilmiştir. Ayrıca test- tekrar test arasında sistematik bir farkın olup olmadığı eşleştirilmiş t testi ile sınanmıştır.  Çalışma sonunda elit ve sub-elit oyuncuların planlı yön değiştirme bulguları anlamlı bir fark bulunmazken, reaktif çeviklik derecelerinin elit oyuncularda istatistiksel olarak anlamlı farklı (sırasıyla 7,14±4.85 sn ve 9,87±5,07 sn) şekilde düşük olduğu tespit edilmiştir. Bununla beraber her iki test arasında yüksek düzeyde  bir açıklayıcılık katsayısı tespit (r2: 0,63, p<0.01) edilmiştir. Test- tekrar test karşılaştırılmasında yüksek bir sınıf içi korelasyon katsayısı (0,930) ve çok düşük varyasyon katsayısı (4,7) belirlenmiştir. Ayrıca Bland-Altman grafiğinde iki ölçüm arasında elde edilen tüm verilerin %95 uyum aralığının dar ve iyi bir uyum gösterdiği gözlenmiştir. Sonuç olarak,  badminton sporuna göre düzenlenmiş Reaktif Çeviklik Testinin geçerli ve güvenilir bir ölçüm yöntemi olduğu tespit edilmiştir ve badminton oyuncularının reaktif çeviklik becerilerinin geliştirilmesinde ve gelişimlerinin takibinde kullanılabileceği önerilmektedir. 

Force–Velocity–Power Profile in High-Elite Boulder, Lead, and Speed Climber Competitors

2020 ◽  
Vol 15 (7) ◽  
pp. 1012-1018
Author(s):  
Guillaume Levernier ◽  
Pierre Samozino ◽  
Guillaume Laffaye
Keyword(s):  
External Force ◽  
Coefficient Of Variation ◽  
High Speed ◽  
Intraclass Correlation ◽  
Force Production ◽  
Maximal Velocity ◽  
Mean Power ◽  
Power Profile ◽  
Force Velocity ◽  
The Difference

Purpose: To compare the force-production capacities among boulderers, lead climbers, and speed climbers during a pull-up test using a force–velocity–power profile. Methods: In total, 24 high-elite climbers (11 boulderers, 8 lead climbers, and 5 speed climbers) did 2 pull-ups at different percentages of their body mass (0%, 30%, 45%, 60%, and 70%). Force–velocity–power profile analyses were performed with the use of an accelerometer for each load. The intraclass correlation and coefficients of variation were calculated. A 1-way analysis of variance was performed with a Tukey post hoc test to assess the difference between the groups. Results: Regarding force, the coefficient of variation ranged from 1.00% to 6.18% and the intraclass correlation ranged from .98 to .99. For velocity, the coefficient of variation ranged from 2.75% to 6.62% and the intraclass correlation ranged from .84 to .95. The linear regression slope showed R2 to be between .93 and .99, confirming the high quality of the linear relationship between velocity and the external force produced during a pull-up. Boulderers presented significantly higher (P < .05) maximal power (+22.30% and +26.29%), mean power for the pull-up at body weight (+23.49% and +25.35%), and theoretical maximal velocity at zero force (+23.92% and +21.53%) than lead and speed climbers and a more significant curve increase (+35.21% compared with lead climbers). Conclusions: The reliability of the method was shown to be high. Moreover, boulderers were able to develop an important external force and had the capacity to maintain high speed when force production increased.

scholarly journals A Validated, Automated, 3-Dimensional Method to Reliably Measure Tibial Torsion

2021 ◽  
Vol 49 (3) ◽  
pp. 747-756
Author(s):  
Joanna M. Stephen ◽  
Robert A. Teitge ◽  
Andy Williams ◽  
James D.F. Calder ◽  
Hadi El Daou
Keyword(s):  
Intraclass Correlation ◽  
Ct Scanning ◽  
Tibial Torsion ◽  
Good Reliability ◽  
Automated Method ◽  
Clinical Methods ◽  
Significant Difference ◽  
Mri Scans ◽  
Males And Females ◽  
The Difference

Background: Tibial torsion is a twist in the tibia measured as an angle between a proximal axis line and a distal axis line. Abnormal torsion has been associated with a variety of painful clinical syndromes of the lower limb. Measurements of normal tibial torsion reported by different authors vary by 100% (ranging from 20° to 42°), making it impossible to determine normal and pathological levels. Purpose: To address the problem of unreliable measurements, this study was conducted to define an automated, validated computer method to calculate tibial torsion. Reliability was compared with current clinical methods. The difference between measurements of torsion generated from computed tomography (CT) and magnetic resonance imaging (MRI) scans of the same bone, and between males and females, was assessed. Study Design: Controlled laboratory study. Methods: Previous methods of analyzing tibial torsion were reviewed, and limitations were identified. An automated measurement method to address these limitations was defined. A total of 56 cadaveric and patient tibiae (mean ± SD age, 37 ± 15 years; range, 17-71 years; 28 female) underwent CT scanning, and 3 blinded assessors made torsion measurements by applying 2 current clinical methods and the automated method defined in the present article. Intraclass correlation coefficient (ICC) values were calculated. Further, 12 cadaveric tibiae were scanned by MRI, stripped of tissue, and measured using a structured light (SL) scanner. Differences between torsion values obtained from CT, SL, and MRI scans, and between males and females, were compared using t tests. SPSS was used for all statistical analysis. Results: When the automated method was used, the tibiae had a mean external torsion of 29°± 11° (range, 9°-65). Automated torsion assessment had excellent reliability (ICC, 1), whereas current methods had good reliability (ICC, 0.78-0.81). No significant difference was found between the torsion values calculated from SL and CT ( P = .802), SL and MRI ( P = .708), or MRI and CT scans ( P = .826). Conclusion: The use of software to automatically perform measurements ensures consistency, time efficiency, validity, and accuracy not possible with manual measurements, which are dependent on assessor experience. Clinical Relevance: We recommend that this method be adopted in clinical practice to establish databases of normal and pathological tibial torsion reference values and ultimately guide management of related conditions.

scholarly journals OR23-01 Intrapatient ACTH Variability in Cushing’s Disease: Prognostic Significance

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Reinier Alvarez ◽  
Elizabeth Hogan ◽  
Tianxia Wu ◽  
Constantine A Stratakis ◽  
Lynnette K Nieman ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Cushing’S Disease ◽  
Coefficient Of Variation ◽  
Intraclass Correlation ◽  
Prognostic Significance ◽  
Cushing's Disease ◽  
Serum Cortisol Level ◽  
Data Set ◽  
Specificity And Sensitivity ◽  
Time Point

Abstract Introduction: In patients with Cushing’s Disease (CD), intrapatient variability of hormone measurements creates significant clinical challenges, therefore multiple measurements are recommended.1 Urinary and salivary cortisol variation has been well described. However, intrapatient variation of adrenocorticotropic hormone (ACTH) in CD remains unknown. In CD patients, ACTH levels are inherently elevated from baseline but the coefficient of diurnal variation is reduced.2Additionally, at each diurnal time point, these exists a significant variation around the mean for the ACTH levels. In this study, we first analyzed the intrapatient variablility of ACTH at each diurnal timepoint in patients with CD. CD is primarily a disorder of ACTH excess, and treatment directed at pituitary adenomas would presumably perturb ACTH levels prior to affecting serum or urine cortisol. We hypothesized that the coefficient of variation at each diurnal time-point can help predict remission from CD following surgery. Methods: We conducted a retrospective review of patients (n = 645) who had histopathologically confirmed diagnosis of CD from 2005-2019 (NCT NCT00060541). We selected patients that had ≥ 3 plasma ACTH values over a 7 day span prior to surgical or medical intervention. We grouped the ACTH measurements into morning (AM) and midnight (PM) values to account for diurnal variation in ACTH secretion. We then analyzed post-operative hormone measurements performed every 6 hours prior to administration of replacement corticosteroids. Remission was assigned to patients with nadir serum cortisol level ≤5 mcg/dL within ten days post-operatively3,4. Results: We found 54 patients with multiple PM (n = 27) and AM (n = 41) ACTH measurements within a 7 day span. We found that the median coefficient of variation (CV) of intra-patient variability was 19.7% (N=41) (95% CI:12.5-27.5) for the AM and was 24% (N=27) (95% CI: 9.6-31.8) for the PM. Age, the number of tests, or the length of test period were not correlated with CV or absolute levels of ACTH. The intraclass correlation coefficient (ICC) of the AM data set was 0.59 and the PM data set was 0.79 which demonstrates a good and excellent reliability respectively. We found that that, in general, 30-60% decrease from pre-operative ACTH levels predicted remission from CD. ACTH decrease &gt;50% on POD2 and 3 had 100% specificity and sensitivity in predicting remission. The decrease in ACTH preceded cortisol nadir in 3/10 patients by 24 hours. Conclusion: We found significant intra-patient variability in plasma levels of ACTH at individual diurnal timepoints in CD patients. We also found that the change in ACTH &gt;50% on POD2 or 3 is an excellent predictor of remission from CD.

scholarly journals ASSOCIATION OF BMI ON TEMPORALSPATIAL PARAMETERS OF GAIT IN YOUNG ADULTS

2016 ◽  
Vol 5 (2) ◽  
pp. 49-56
Author(s):  
Nabeel Baig ◽  
Sundus Masood ◽  
Shazia Qudrat ◽  
Asif Ashiq Ali
Keyword(s):  
Young Adults ◽  
Target Population ◽  
Step Length ◽  
Obese Individual ◽  
Normal Weight ◽  
Gait Velocity ◽  
Gait Parameters ◽  
Significant Difference ◽  
The Difference ◽  
Study Participants

OBJECTIVE To study the effects of BMI on temporal-spatial gait parameters in young adults TARGET POPULATION AND SAMPLE SIZE Target population in this study is students. Total 40 students participated in this study. Participants were drawn from College of Physical Therapy. STUDY DESIGN Observational study METHOD 40 young adults both male and female were selected, keeping 10 students in each group of underweight, normal weight, overweight and obese. Each participant was instructed to walk over 20 meters area both indoor and outdoor at their normal pace wearing normal footwear. Step length and cadence were measured and gait velocity of each participant was calculated. Results were compared for both outdoor and indoor walk. RESULT The result of this study revealed statistically no significant differences in the measured variables between four groups, i.e. underweight, normal weight, overweight, and obese young individuals in both outdoor and indoor settings and found significant difference is indoor walk step length and gait velocity. Overweight and obese individuals have shorter step length and gait velocity, underweight individuals walk was better than other groups CONCLUSION The study shows no difference in gait in relation of BMI. There was the difference in step length and gait velocity in overweight and obese individual.

Reliability and Sensitivity of Reaction Time Measurements During Quasi-Realistic Soccer Situations

Motor Control ◽  
2021 ◽  
pp. 1-11
Author(s):  
Lazar Tomic ◽  
Danica Janicijevic ◽  
Aleksandar Nedeljkovic ◽  
Bojan Leontijevic ◽  
Amador García-Ramos
Keyword(s):  
Reaction Time ◽  
Coefficient Of Variation ◽  
Size Range ◽  
High Reliability ◽  
Intraclass Correlation ◽  
Stimulus Presentation ◽  
Soccer Players ◽  
Force Development ◽  
Professional Soccer ◽  
The Difference

Reliability and sensitivity of reaction time (RT) during quasi-realistic soccer situations was explored in 10 professional soccer players (skilled; age = 20.9 ± 3.6 years) and 10 males without soccer experience (nonskilled; age = 23.4 ± 0.5 years). The participants were instructed to react as fast as possible to a stimulus presented via the video-based method while standing on force platforms. RT was computed as the difference between the instant when the rate of force development of any leg reaches 5% of its maximal value and the instant of stimulus presentation. The results revealed acceptable to high reliability of RT (intraclass correlation coefficient median = .90; coefficient of variation ≤ 5.83%), and shorter RT for skilled compared with nonskilled participants in three out of eight comparisons (effect size range = 1.00–1.41). The video-based methods can be confidently used to assess the RT in soccer players.

Assessment of Acidogenicity of Commercially Available Biscuits on Salivary pH - An in vivo Study

2020 ◽  
pp. 139-147
Author(s):  
B. Vivek Babu ◽  
Jayashri Prabakar
Keyword(s):  
Simple Random Sampling ◽  
In Vivo Study ◽  
Data Set ◽  
Group I ◽  
Significant Difference ◽  
Salivary Ph ◽  
The Difference ◽  
Group 2 ◽  
Inorganic Molecules

Saliva is a complex secretion consisting of 99% of water and remaining 1% of organic and inorganic molecules. Sucrose and starches are the predominant dietary carbohydrates in modern societies. Among all the foods consumed by children, chocolates and biscuits are the most common. Therefore this present in vivo study was conducted to assess the acidogenic effect of commercially available biscuits on salivary pH among 10 to 15 years old children. Study Design used in the study was In Vivo clinical study (Pilot Trail). The population collected in the survey was children between the age group of 10 - 15 years old children. 4 Groups were considered and 10 in each group. Group 1: Hide and Seek, Group 2: Good Day, Group 3: Dream and Cream, Group 4: Oreo. Sampling method used in the study was conducted as simple random sampling. Ethical approval of the study was obtained from Saveetha Institutional Review Board. Informed consent of the children were obtained from the parents. Descriptive statistics were expressed by means of mean and standard deviation. Shapiro Wilks test used to test the normality of the data set. Kruskal Wallis test was used to find the difference in mean Salivary pH between the groups and within the groups at Baseline, Immediate and after 15 min, 30 mins. A statistically significant difference in mean Salivary pH was observed between the groups at Immediate and after 30 mins (p<0.05). The mean Salivary pH was significantly dropped in Oreo, Dream cream and Hide & Seek groups at various time-periods. Based on the results of the present study, it can be concluded that maximum drop in mean salivary pH was observed in Group IV followed by Group II and Group I. It was observed that in all the groups, the pH gradually got back to near normal levels due to the buffering mechanism of saliva.

scholarly journals Assessment of pulmonary arterial compliance evaluated using harmonic oscillator kinematics

2017 ◽  
Vol 7 (3) ◽  
pp. 666-673
Author(s):  
Yasunobu Hayabuchi ◽  
Akemi Ono ◽  
Yukako Homma ◽  
Shoji Kagami
Keyword(s):  
Harmonic Oscillator ◽  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Intraclass Correlation ◽  
Resistance Index ◽  
Abdominal Compression ◽  
Windkessel Model ◽  
Significant Difference ◽  
Before And After ◽  
The Difference

We hypothesized that KPA, a harmonic oscillator kinematics-derived spring constant parameter of the pulmonary artery pressure (PAP) profile, reflects PA compliance in pediatric patients. In this prospective study of 33 children (age range = 0.5–20 years) with various cardiac diseases, we assessed the novel parameter designated as KPA calculated using the pressure phase plane and the equation KPA = (dP/dt_max)2/([Pmax – Pmin])/2)2, where dP/dt_max is the peak derivative of PAP, and Pmax – Pmin is the difference between the minimum and maximum PAP. PA compliance was also calculated using two conventional methods: systolic PA compliance (sPAC) was expressed as the stroke volume/Pmax – Pmin; and diastolic PA compliance (dPAC) was determined according to a two-element Windkessel model of PA diastolic pressure decay. In addition, data were recorded during abdominal compression to determine the influence of preload on KPA. A significant correlation was observed between KPA and sPAC (r = 0.52, P = 0.0018), but not dPAC. Significant correlations were also seen with the time constant (τ) of diastolic PAP (r = −0.51, P = 0.0026) and the pulmonary vascular resistance index (r = −0.39, P = 0.0242). No significant difference in KPA was seen between before and after abdominal compression. KPA had a higher intraclass correlation coefficient than other compliance and resistance parameters for both intra-observer and inter-observer variability (0.998 and 0.997, respectively). These results suggest that KPA can provide insight into the underlying mechanisms and facilitate the quantification of PA compliance.

scholarly journals Completeness of the eutherian mammal fossil record and implications for reconstructing mammal evolution through the Cretaceous/Paleogene mass extinction

Paleobiology ◽  
2017 ◽  
Vol 43 (4) ◽  
pp. 521-536 ◽  
Author(s):  
Thomas W. Davies ◽  
Mark A. Bell ◽  
Anjali Goswami ◽  
Thomas J. D. Halliday
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Information Criterion ◽  
Molecular Data ◽  
Tectonic Activity ◽  
Eutherian Mammal ◽  
Geological Time ◽  
Data Set ◽  
Significant Difference ◽  
The Difference

AbstractThere is a well-established discrepancy between paleontological and molecular data regarding the timing of the origin and diversification of placental mammals. Molecular estimates place interordinal diversification dates in the Cretaceous, while no unambiguous crown placental fossils have been found prior to the end-Cretaceous mass extinction. Here, the completeness of the eutherian fossil record through geological time is evaluated to assess the suggestion that a poor fossil record is largely responsible for the difference in estimates of placental origins. The completeness of fossil specimens was measured using the character completeness metric, which quantifies the completeness of fossil taxa as the percentage of phylogenetic characters available to be scored for any given taxon. Our data set comprised 33 published cladistic matrices representing 445 genera, of which 333 were coded at the species level.There was no significant difference in eutherian completeness across the Cretaceous/Paleogene (K/Pg) boundary. This suggests that the lack of placental mammal fossils in the Cretaceous is not due to a poor fossil record but more likely represents a genuine absence of placental mammals in the Cretaceous. This result supports the “explosive model” of early placental evolution, whereby placental mammals originated around the time of the K/Pg boundary and diversified soon after.No correlation was found between the completeness pattern observed in this study and those of previous completeness studies on birds and sauropodomorph dinosaurs, suggesting that different factors affect the preservation of these groups. No correlations were found with various isotope proxy measures, but Akaike information criterion analysis found that eutherian character completeness metric scores were best explained by models involving the marine-carbonate strontium-isotope ratios (87Sr/86Sr), suggesting that tectonic activity might play a role in controlling the completeness of the eutherian fossil record.

scholarly journals use of aspect in Czech L2

2003 ◽  
Vol 29 ◽  
pp. 177-194
Author(s):  
Barbara Schmiedtová
Keyword(s):  
English Learners ◽  
English Learner ◽  
Data Set ◽  
Lexical Meaning ◽  
Imperfective Aspect ◽  
Verbal Prefixes ◽  
Significant Difference ◽  
Verb Forms ◽  
The Difference ◽  
The Right

The focus of the present paper is on the difference between English and German learners‘ use of perfectivity and imperfectivity. The latter is expressed by means of suffixation (suffix -va-). In contrast, perfectivity is encoded either by suffixation (-nou-) or by prefixation (twenty different prefixes that mostly modify not only aspectual but also lexical properties of the verb). In the native Czech data set, there is no significant difference between the number of imperfectively and perfectively marked verb forms. In the English data, imperfectively and perfectively marked verb forms are equally represented as well. However, German learners use significantly more perfective forms than English learners and Czech natives. When encoding perfectivity in Czech, German learners prefer to use prefixes to suffixes. Overall, English learners in comparison to German learners encode more perfectives by means of suffixation than prefixation. These results suggest that German learners of Czech focus on prefixes expressing aspectual and lexical modification of the verb, while English learners rather pay attention to the aspectual opposition between perfective and imperfective. In a more abstract way, the German learner group focuses on the operations carried out on the left side from the verb stem while the English learner group concentrates on the operations performed on the right side qfrom the verb stem. This sensitivity can be to certain degree motivated by the linguistic devices of the corresponding source languages: English learners of Czech use imperfectives mainly because English has marked fully grammatical form for the expression of imperfective aspect – the progressive -ing form. German learners, on the other hand, pay in Czech more attention to the prefixes, which like in German modify the lexical meaning of the verb. In this manner, Czech prefixes used for perfectivization function similar to the German verbal prefixes (such as ab-, ver-) modifying Aktionsart.  

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