This study investigated the effects of knee joint angle on muscle activation, exerted torque, and whether the knee angle affects the muscle activation–torque ratio. Nine healthy adult male participants participated in the study. They performed maximal voluntary isometric contraction (MVIC) at six (80°, 90°, 100°, 110°, 120°, and 130°) different knee joint angles (i.e., angles between the thigh and shin bones). Their maximal torque was assessed utilizing an isokinetic chair, while their muscle activation (root mean square [RMS]) was assessed using an eight-channel single differential surface EMG sensor. For the purposes of the torque–knee angle relationship and muscle activation–knee angle relationship, the torque and RMS were normalized relative to the maximal value obtained by each participant. To evaluate the muscle activation–torque ratio in function of knee angle, RMS was normalized relative to the corresponding torque obtained at each knee angle. Repeated measure analysis of variance was used to investigate the effects of knee angle on muscle activation, torque, and muscle activation–torque ratio. There was a significant effect of knee joint angle on normalized torque (F = 27.521, p < 0.001), while the activation of vastus lateralis and vastus medialis remained unchanged. The changes in knee angle affected the muscle activation–torque ratio of vastus lateralis (Chi-square = 16.246, p = 0.006) but not the vastus medialis. These results suggest that knee joint angles from 80° to 130° provide a stable milieu for muscle electrification, while mechanical factor such as knee joint angle (i.e., lever arm length) affect the torque output when one needs to contract quadriceps maximally during the isometric contraction.

Numerous factors can influence the reliability of the signal obtained by electromyography EMG among which the type of contraction is practically fundamental. This study aimed to investigate intra-and inter-session reliability of EMG for maximal voluntary isometric contraction (MVIC) of the knee extensors at different joint angles. Nine healthy male students from the Faculty of Sport and Physical Education voluntarily joined the experiment. Main characteristics of the subjects were: age 23±1 years, body weight 80.8±7.8 kg and body height 182±7 cm. EMG signal from three surface heads of quadriceps femoris was recorded -vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF). Subjects had to perform 3 MVIC as fast as possible, as strong as possible at 6 different knee joint angles on 2 occasions separated by 7-8 days. The intra-class coefficient of correlation (ICC) was used to identify relative intra-and inter-session reliability, while standard error of measurement (SEM) was used to calculate the absolute reliability of each tested muscle. All muscles showed high intra-session reliability (ICC=0.488-0.988 and SEM=1.38-11.35). VL showed good inter-session reliability for most of the conditions (ICC=0.603-0.948), VM for two knee angles (ICC120°=0.764 and ICC130°=0.788), RF was not reliable for any knee angle. This study indicates that RF does not need to be used in EMG testing in leg extension MVIC due to lack of reliability between two sessions, and If EMG RMS from VL and VM will be tested, knee angle of 120° should be used for the testing.

Th e purpose of this study was to assess the reliability of tests for the assessment of maximal isometric muscle force (F(max)) and the explosive force (viewed through the rate of force development-RFD(max)). Tests were carried out for muscle m. quadriceps femoris, in the open (OKL) and closed (CKC) kinetic chain under 6 diff erent angles in the knee joint, ranging from 80˚-130˚ (with changes of at 10˚, 180˚ represents the fully extended leg). Th e study tested ,, intra-assay "(between 3 attempts within a testing session),, and inter-test" (test-retest) reliability presented through ICC coeffi cients. In addition, diff erences between the results achieved in diff erent angles for the same test, for Fmax and RFDmax were examined by ANOVA with repeated measures. Nine students of FSPE (23.5 ± 1:38 years) performed each three isometric contractions, by taking tasks of: seated leg extension (OKC) and seated leg press (CKC). Tests were carried out in chronological order: OKC1-OKC2, CKC1-CKC2 (Firstly the OKC test, two times in a span of 72 hours, and then the CKC on the same principle). Th e results suggest that the CKC is generally more reliable test, but that the reliability of maximal isometric and explosive force varies depending on the selection of the task / test, articulated joint angle and selecting variables for monitoring ("inter" vs "intra" and "avg " vs " max"). Th e diff erences in the results of monitored variables among the articular angles indicate that in the OKC m. quadriceps femoris behaves in accordance with F-L (force-length) relation, while the mechanical conditions of the bone-joint levers in the CKC are crucial for the expression of muscle force.

Two microsporidia species of the Nosema genus cause nosemosis in the adult honeybee: N. apis and N. ceranae. For diagnostic purposes and the determination of infection level various microscopic and molecular biological methods are used. Th e aim of this research was to compare the reliability of the traditional microscopic assessment and two PCR techniques: simplex- and duplex-PCR. Honey bee samples were taken from 150 colonies. Microscopic examination, performed according to the recommendations of the OIE, revealed Nosema spores in 68.67% samples analysed, whilst with the simplex-PCR method all samples (100.0%) proved positive. On the other hand, duplex-PCR method used for the identifi cation of Nosema species resulted in 84.0% positive samples, all of which were N. ceranae. Our recommendation of the simplex-PCR method for the monitoring of honey bees in fi eld conditions is based on its higher reliability than the microscopic assessment in the detection of low-level infections, as well as its potential for the detection of vegetative Nosema sp. stages; thus the early detection and timely prevention of Nosema infection would be possible. Nosema species identifi cation is simplest and most cost-eff ective if performed with the duplex-PCR analysis. However, the simplex-PCR is more reliable, thus, it is suggested that samples that were negative when assessed with microscopy and duplex-PCR analysis undergo simplex-PCR.