Mechanical properties of the patellar tendon in adults and children

It is not currently known how the mechanical properties of human tendons change with maturation in the two sexes. To address this, the stiffness and Young's modulus of the patellar tendon were measured in men, women, boys and girls (each group, n=10). Patellar tendon force (F_pt) was calculated from the measured joint moment during a ramped voluntary isometric knee extension contraction, the antagonist knee extensor muscle co-activation quantified from its electromyographical activity, and the patellar tendon moment arm measured from magnetic resonance images. Tendon elongation was imaged using the sagittal-plane ultrasound scans throughout the contraction. Tendon cross-sectional area was measured at rest from ultrasound scans in the transverse plane. Maximal F_pt and tendon elongation were (mean±SE) 5453±307 N and 5±0.5 mm for men, 3877±307 N and 4.9±0.6 mm for women, 2017±170 N and 6.2±0.5 mm for boys and 2169±182 N and 5.9±0.7 mm for girls. In all groups, tendon stiffness and Young's modulus were examined at the level that corresponded to the maximal 30% of the weakest participant's F_pt and stress, respectively; these were 925–1321 N and 11.5–16.5 MPa, respectively. Stiffness was 94% greater in men than boys and 84% greater in women than girls (p<0.01), with no differences between men and women, or boys and girls (men 1076±87 N/mm; women 1030±139 N/mm; boys 555±71 N/mm and girls 561.5±57.4 N/mm). Young's modulus was 99% greater in men than boys (p<0.01), and 66% greater in women than girls (p<0.05). There were no differences in modulus between men and women, or boys and girls (men 597±49 MPa; women 549±70 MPa; boys 255±42 MPa and girls 302±33 MPa). These findings indicate that the mechanical stiffness of tendon increases with maturation due to an increased Young's modulus and, in females due to a greater increase in tendon cross-sectional area than tendon length.     

The region-dependent biphasic viscoelastic properties of human temporomandibular joint discs under confined compression

The objective of this study was to determine the biphasic viscoelastic properties of human temporomandibular joint (TMJ) discs, correlate these properties with disc biochemical composition, and examine the relationship between these properties and disc dynamic behavior in confined compression. The equilibrium aggregate modulus (H_A), hydraulic permeability (k), and dynamic modulus were examined between five disc regions. Biochemical assays were conducted to quantify the amount of water, collagen, and glycosaminoglycan (GAG) content in each region. The creep tests showed that the average equilibrium moduli of the intermediate, lateral, and medial regions were significantly higher than for the anterior and posterior regions (69.75±11.47 kPa compared to 22.0±5.15 kPa). Permeability showed the inverse trend with the largest values in the anterior and posterior regions (8.51±1.36×10^?15 m⁴/Ns compared with 3.75±0.72×10^?15 m⁴/Ns). Discs were 74.5% water by wet weight, 62% collagen, and 3.2% GAG by dry weight. Regional variations were only observed for water content which likely results in the regional variation in biphasic mechanical properties. The dynamic modulus of samples during confined compression is related to the aggregate modulus and hydraulic permeability of the tissue. The anterior and posterior regions displayed lower complex moduli over all frequencies (0.01–3 Hz) with average moduli of 171.8–609.3 kPa compared with 454.6–1613.0 kPa for the 3 central regions. The region of the TMJ disc with higher aggregate modulus and lower permeability had higher dynamic modulus. Our results suggested that fluid pressurization plays a significant role in the load support of the TMJ disc under dynamic loading conditions.     

Acute responses of heat acclimatised cyclists to intermittent sprints in temperate and warm conditions

(1) This study describes the performance and the acute physiological responses of heat acclimatised cyclists during three sets of 5×20 s sprints followed by a final sprint to exhaustion in temperate (mean±standard deviation 20.2±0.4°C; 46±2% humidity, 108.5±1.4 kPa water vapour pressure) and in warm conditions (30.5±0.4°C; 47±10% humidity, 206.8±6.4 kPa water vapour pressure). (2) Oxygen consumption was greater in the warm condition and there was no evidence of an increased reliance on anaerobic metabolism as has been reported for submaximal exercise in the heat. (3) Subjects lost 2.1±0.2% of body mass in 53.8±0.2 min during the warm condition. While the duration of the time to exhaustion final sprint was 50±13 s during the warm condition it was 60±7 s for the temperate condition (p=0.020).     

Changes in force and tendinous tissue elongation during the early phase of tetanic summation in in vivo human tibialis anterior muscle

The purpose of this study was to determine the changes that occur in tendinous tissue properties during the early phase of tetanic summation in the in vivo human tibialis anterior muscle (TA). The torque response and tendinous tissue elongation following single stimuli, two-pulse trains, and three-pulse trains were recorded in the TA during isometric contractions. The elongation, compliance, and lengthening velocity of tendinous tissue were determined by real-time ultrasonography. The contribution of the response to the second stimulation (C2) was obtained by subtracting the response to the single stimulation (C1) from the response of doublet. The third contribution (C3) was obtained by subtracting the response to the doublet from that of the triplet. C2 (7.8±0.5 Nm) and C3 (7.3±0.6 Nm) had torque responses significantly higher than C1 (3.6±0.7 Nm). In contrast, the elongations of tendinous tissue for C2 (2.8±0.4 mm) and C3 (1.7±0.2 mm) were significantly lower than for C1 (4.9±0.3 mm), indicating that the summation pattern of tendinous tissue elongation is different from the summation pattern of torque response. In addition, this showed considerable difference both between C1 (0.12±0.01 mm/N; 83±4.6 mm/s) and C2 (0.03±0.005 mm/N; 50±6.3 mm/s) and between C1 and C3 (0.02±0.002 mm/N; 39±6.4 mm/s) in the compliance and lengthening velocity of tendinous tissue. These results suggest that changes in tendinous tissue properties between first and second contraction are related to different summation patterns of force and tendinous tissue elongation during early phase of tetanic summation.     

Cloning,characterization and validation of inosine 5′-monophosphate dehydrogenase of Babesia gibsoni as molecular drug target

The inosine monophosphate dehydrogenase (IMPDH) enzyme has been characterized and validated as a molecular drug target in other apicomplexans but not in the genus Babesia. Subsequently, we cloned and expressed a Babesia gibsoni IMPDH (BgIMPDH) cDNA in Escherichia coli. We also determined the inhibitory effect of mycophenolic acid (MPA) on recombinant BgIMPDH (rBgIMPDH) activity and the Babesia-growths in vitro. The translated BgIMPDH peptide contained thirteen amino acid residues responsible for substrate and cofactor binding in its catalytic domain with Gly374 in BgIMPDH being replaced by Ser388 in mammalian IMPDH. The native BgIMPDH enzyme in the parasite was approximately 54-kDa a mass similar to His-tag rBgIMPDH protein. The K_m values of the rBgIMPDH were 8.18 ± 0.878 (mean ± standard error of the mean) μM and 360.80 ± 43.41 μM for IMP and NAD⁺, respectively. MPA inhibited the rBgIMPDH activity yielding a K_i value of 20.93 ± 1.83 μM with respect to NAD⁺. For Babesia growths, the IC₅₀s were 0.95 ± 0.21 and 2.88 ± 0.49 μM for B. gibsoni and B. bovis, respectively. Therefore, our results suggest that MPA may inhibit the replication of Babesia parasites by targeting IMPDH enzyme of the purine pathway.     

Cryopreservation of sperm of an indigenous endangered fish species Nandus nandus (Hamilton, 1822) for ex-situ conservation

This study dealt with the development of cryopreservation protocol for Nandus nandus, which entailed a number of experiments. Sperm was collected by sacrificing males. The collected sperm was suspended in extenders. Activation of sperm motility was evaluated in different osmolalities of NaCl. Motility of sperm decreased as the osmolality of the extender increased and was completely inhibited at almost 319 mOsmol/kg. To evaluate the toxicity of cryoprotectant, sperm was incubated with DMSO, methanol and ethanol at 5%, 10% and 15% concentrations, respectively, for 5–35 min. Five and ten percent of cryoprotectants produced better motility during 5 and 10 min incubation. Sperm incubated with 15% cryoprotectant seemed to be toxic and this concentration was excluded in the subsequent trials. Three extenders, namely, Alsever’s solution, egg-yolk citrate and urea egg-yolk and three cryoprotectants, DMSO, methanol and ethanol were employed to preserve the sperm. Alsever’s solution with 10% DMSO showed best performance producing 90.0 ± 1.8% and 75.0 ± 2.5% equilibration and post-thaw motility followed by that of 82.5 ± 4.2% and 62.5 ± 5.5% with Alsever’s solution plus methanol, respectively. Between two diluents, sperm preserved with Alsever’s solution plus DMSO produced highest fertilization (76.7 ± 3.3%) and hatching (43.8 ± 7.9%) while fresh sperm yielded 83.3 ± 6.7% and 64.0 ± 10.4% fertilization and hatching, respectively. The protocol developed through the study can be applied for long-term conservation of genetic materials of the endangered fish N. nandus and the cryopreserved sperm can be used in artificial breeding for generating new individuals.     

An effective balancing response to lateral perturbations at pelvis level during slow walking requires control in all three planes of motion

In this study we investigated balancing responses to lateral perturbations during slow walking (0.85 m/s). A group of seven healthy individuals walked on an instrumented treadmill while being perturbed at the level of waist at left heel strike in outward and inward lateral directions. Centre of mass (COM) and centre of pressure (COP), rotation of pelvis around vertical axis, step lengths, step widths and step times were assessed. The results have shown that beside control of COP in lateral direction, facilitated by adequate step widths, control of COP in sagittal direction, slowing down movement of COM was present after commencement of lateral perturbations. Sagittal component of COM was significantly retarded as compared to unperturbed walking for both inward (4.32 ± 1.29 cm) and outward (9.75 ± 2.17 cm) perturbations. This was necessary since after an inward perturbation first step length (0.29 ± 0.04 m compared to 0.52 ± 0.02 m in unperturbed walking) and step time (0.45 ± 0.05 s compared to 0.61 ± 0.04 s in unperturbed walking) were shortened while after an outward perturbation first two step lengths (0.36 ± 0.05 m and 0.32 ± 0.11 m compared to 0.52 ± 0.03 m in unperturbed walking) were shortened that needed to be accommodated by the described modulation of COP in sagittal plane. In addition pronounced pelvis rotation assisted in bringing swing leg to new location. The results of this study show that counteracting lateral perturbations at slow walking requires adequate response in all three planes of motion.     

Demonstration of extended field-of-view ultrasound’s potential to increase the pool of muscles for which in vivo fascicle length is measurable

Static, B-mode ultrasound is the most common method of measuring fascicle length in vivo. However, most forearm muscles have fascicles that are longer than the field-of-view of traditional ultrasound (T-US). As such, little work has been done to quantify in vivo forearm muscle architecture. The extended field-of-view ultrasound (EFOV-US) method, which fits together a sequence of B-mode images taken from a continuous ultrasound scan, facilitates direct measurements of longer, curved fascicles. Here, we test the validity and reliability of the EFOV-US method for obtaining fascicle lengths in the extensor carpi ulnaris (ECU). Fascicle lengths from images of the ECU captured in vivo with EFOV-US were compared to lengths from a well-established method, T-US. Images were collected in a joint posture that shortens the ECU such that entire fascicle lengths were captured within a single T-US image. Resulting measurements were not significantly different (p = 0.18); a Bland-Altman test demonstrated their agreement. A novice sonographer implemented EFOV-US in a phantom and in vivo on the ECU. The novice sonographer’s measurements from the ultrasound phantom indicate that the combined imaging and analysis method is valid (average error = 2.2 ± 1.3 mm) and the in vivo fascicle length measurements demonstrate excellent reliability (ICC = 0.97). To our knowledge, this is the first study to quantify in vivo fascicle lengths of the ECU using any method. The ability to define a muscle’s architecture in vivo using EFOV-US could lead to improvements in diagnosis, model development, surgery guidance, and rehabilitation techniques.     

Impaired action potential conduction at high force levels after eccentric exercise

High-density surface electromyography was used to examine whether gross sarcolemmal function is impaired in m. biceps brachii after intensive eccentric elbow flexor exercise, when measured at wide range of isometric contraction levels.Root mean square (RMS), mean power frequency (MNF) and mean muscle fibre conduction velocity (CV) were calculated before and up to four days post-exercise.Maximal isometric voluntary (MVC) force decreased by 21.3 ± 5.6% two hours after exercise, and by 12.6 ± 11.1% two days post-exercise. CV and MNF decreased both during MVC (CV from 4.1 ± 0.3 m/s to 3.8 ± 0.4 m/s and MNF from 92.6 ± 10 Hz to 85.2 ± 11 Hz) and during electrically evoked maximal M-wave (CV from 4.1 ± 0.3 m/s to 3.0 ± 0.5 m/s and MNF from 97.1 ± 27.2 Hz to 78.0 ± 24.4 Hz) two hours post-exercise. Furthermore, at submaximal isometric force levels, CV and MNF decreased only at higher contraction levels (40%, 50% and 75% of MVC) two hour post-exercise.It can be concluded that intensive exercise can temporarily impair gross sarcolemmal function. In addition, since this only occurred at high force levels, based on Henneman’s size principle, it seems that higher threshold motor units were predominantly affected.     

Chest response assessment of post-mortem swine under blast loadings

To better protect soldiers from blast threat, that principally affect air-filled organs such a lung, it is necessary to develop an adapted injury criterion and, prior to this, to evaluate the response of a biological model against that threat. The objective of this study is to provide some robust data to quantify the chest response of post-mortem swine under blast loadings.7 post-mortem swine (54.5 ± 2.6 kg), placed side-on to the threat and against the ground, were exposed to 5 shock-waves of increasing intensities. Their thorax were instrumented with a piezo-resistive pressure sensor, an accelerometer directly exposed to the shock-wave and a target was mounted on the latter in order to track the chest wall displacement.For incident impulses ranging from 47 kPa ms ± 2% to 173 kPa ms ± 6%, the measured maximum of linear chest wall acceleration (Γmax) goes from 5800 m/s² ± 16% to 41,000 m/s² ± 8%, with a duration of 0.8 ms. Chest wall displacements ranging from 5 mm ± 20% to 20 mm ± 15%, with a duration of 9 ms, are reached. These reproducible data were used to find simple relations (linear, 2nd and 3rd order polynomials) between the kinematic parameters (plus the viscous criterion) and the incident and reflected impulses.Correlating the new reproducible data with the prediction from the Bowen curves showed a lung injury threshold in terms of Γmax similar to that of Cooper (10,000 m/s²). However, the limits defined for the viscous criterion in the automobile field and for non-lethal weapons seems not adapted for the blast threat.     

The role of a cleft upper lip of alpacas in foraging extremely short grasses evaluated by grazing impulse

The role of a cleft upper lip of alpaca (Lama pacos) in foraging short pastures was investigated using biting forces and associated impulses in animal grazing. Three Merino wethers and three castrated alpacas were used. Ten (10L), 20 (20L), 30 (30L), 40 (40L) or 50 (50L) leaves of orchardgrass (Dactylis glomerata) per load cell were offered to animals, and three-directional biting forces were digitally recorded at 5 s⁻¹⁰⁰⁰. From the total biting force/time curve, grazing impulse was calculated, equivalent to the area surrounded by the curve. The grand mean of the number of grazed leaves per bite was 9.8 ± 0.53 in alpaca and 17.9 ± 1.31 in sheep. Remaining leaf length after grazing trial was significantly lower in alpaca than in sheep (11.9 ± 0.19 mm versus 18.5 ± 0.41 mm). Alpaca grazed leaves with significantly lower mean biting force (7.0 ± 0.69 N versus 20.0 ± 1.80 N) and significantly shorter duration time per one biting force (0.11 ± 0.005 s versus 0.18 ± 0.19 s) than sheep. The grand mean of sum of grazing impulse was lower (P < 0.002) in alpaca (2.8 ± 0.42 N s) than in sheep (9.4 ± 1.95 N s). Grazed DM weight increased with increasing leaf densities, but there was no difference between alpaca and sheep. The ratio of DM intake to grazing impulse was significantly higher in alpaca than in sheep (0.18 ± 0.016 g DM/N s versus 0.08 ± 0.010 g DM/N s). The grazing strategy in alpaca seems to be an adaptation for foraging extremely short grasses. Alpacas may push aside cleft upper lips when trying to grasp short leaves, resulting in keeping incisors at lower insertion position near the ground surface.     

The influence of cryopreservation and quick-freezing on the mechanical properties of tendons

In order to maintain their native properties, cryopreserved tendons are usually used in biomechanical research and in transplantation of allogenic tendon grafts. The use of different study protocols leads to controversy in literature and thus complicates the evaluation of the current literature. The aim of this study consisted in examining the influence of different freezing and thawing temperatures on the mechanical properties of tendons. 60 porcine tendons were frozen at either −80 °C or −20 °C for 7 days and thawed at room or body temperature for 240 or 30 min, respectively. A subgroup of ten tendons was quick-frozen with liquid nitrogen (−196 °C) for 2 s before cryopreservation. Biomechanical testing was performed with a material testing machine and included creep, cyclic and load-to-failure tests. The results showed that freezing leads to a reduced creep strain after constant loading and to an increased secant modulus. Freezing temperature of −80 °C increased the secant modulus and decreased the strain at maximum stress, whereas thawing at room temperature reduced the maximum stress, the strain at initial tendon failure and the Young’s Modulus. Quick-freezing led to increased creep strain after constant loading, increased strain at initial failure in the load-to-failure test, and decreased strain at maximum stress. When cryopreserving, tendons for scientific or medical reasons, freezing temperature of −20 °C and thawing temperature of 37.5 °C are recommended to maintain the native properties of tendons. A treatment with liquid nitrogen in the sterilization process of tendon allografts is inadvisable because it alters the tendon properties negatively.     

A comparison of EMG-based muscle fatigue assessments during dynamic contractions

Several EMG-based approaches to muscle fatigue assessment have recently been proposed in the literature. In this work, two multivariate fatigue indices developed by the authors: a generalized mapping index (GMI) and the first component of principal component analysis (PCA) were compared to three univariate indices: Dimitrov’s normalized spectral moments (NSM), Gonzalez-Izal’s waveletbased indices (WI), and Talebinejad’s fractal-based Hurst Exponent (HE). Nine healthy participants completed two repetitions of fatigue tests during isometric, cyclic and random fatiguing contractions of the biceps brachii. The fatigue assessments were evaluated in terms of a modified sensitivity to variability ratio yielding the following scores (mean ± std.dev.): PCA: (12.6 ± 5.6), GMI: (11.5 ± 5.4), NSM: (10.3 ± 5.4), WI: (8.9 ± 4.6), HE: (8.0 ± 3.3). It was shown that PCA statistically outperformed WI and HE (p < 0.01) and that GMI outperformed HE (p < 0.02). There was no statistical difference among NSM, WI and HE (p > 0.2). It was found that taking the natural logarithm of NSM and WI, although reducing the parameters’ sensitivity to fatigue, increased SVR scores by reducing variability.     

The effect of sliding velocity on chondrocytes activity in 3D scaffolds

Sliding motion and shear are important mediators for the synthesis of cartilage matrix and surface molecules. This study investigated the effects of velocity magnitude and motion path on the response of bovine chondrocytes cultured in polyurethane scaffolds and subjected to oscillation against a ceramic ball. In order to vary velocity magnitude, the ball oscillated ±25° at 0.01, 0.1, and 1 Hz to generate 0.28, 2.8, and 28 mm/s, respectively. The median velocity of these ‘open’ motion trajectories was tested against ‘closed’ motion trajectories in that the scaffold oscillated ±20° against the ball at 1 Hz, reaching 2.8 mm/s. Constructs were loaded twice a day for 1 h over 5 days. Gene expression of cartilage oligomeric matrix protein (COMP), proteoglycan 4 (PRG4, lubricin), and hyaluronan synthase 1 (HAS1) and release of COMP, PRG4, and hyaluronan (HA) were analyzed.Velocity magnitude determined both gene expression and release of target molecules. Using regression analysis, there was a positive and significant relationship with all outcome variables. However, only COMP reacted significantly at 0.28 mm/s, while all other measured variables were considerably up-regulated at 28 mm/s. Motion path characteristics affected COMP, but not PRG4 and HAS1/HA.To conclude, velocity magnitude is a critical determinant for cellular responses in tissue engineered cartilage constructs. The motion type also plays a role. However, different molecules are affected in different ways. A molecule specific velocity threshold appears necessary to induce a significant response. This should be considered in further studies investigating the effects of continuous or intermittent motion.     

Biomechanical properties of murine TMJ articular disc and condyle cartilage via AFM-nanoindentation

This study aims to quantify the biomechanical properties of murine temporomandibular joint (TMJ) articular disc and condyle cartilage using AFM-nanoindentation. For skeletally mature, 3-month old mice, the surface of condyle cartilage was found to be significantly stiffer (306 ± 84 kPa, mean ± 95% CI) than those of the superior (85 ± 23 kPa) and inferior (45 ± 12 kPa) sides of the articular disc. On the disc surface, significant heterogeneity was also detected across multiple anatomical sites, with the posterior end being the stiffest and central region being the softest. Using SEM, this study also found that the surfaces of disc are composed of anteroposteriorly oriented collagen fibers, which are sporadically covered by thinner random fibrils. Such fibrous nature results in both an F-D^3/2 indentation response, which is a typical Hertzian response for soft continuum tissue under a spherical tip, and a linear F-D response, which is typical for fibrous tissues, further signifying the high degree of tissue heterogeneity. In comparison, the surface of condyle cartilage is dominated by thinner, randomly oriented collagen fibrils, leading to Hertzian-dominated indentation responses. As the first biomechanical study of murine TMJ, this work will provide a basis for future investigations of TMJ tissue development and osteoarthritis in various murine TMJ models.     

Effect of sucrose on dynamic mechanical characteristics of maize and potato starch films

The dynamic mechanical properties of prepared maize and potato starch films were evaluated for mixtures containing 0%, 10% and 15% (w/w) of sucrose at temperatures ranging from 40.0 to 140.0 °C. The spectra of storage modulus (G′), loss modulus (G″), and loss factor (tan δ) of starch films were acquired. Remarkable reduction in the glass transition temperature of maize and potato starch films was observed with the increasing sucrose content. The spectra of storage modulus (G′), loss modulus (G″), and loss factor (tan δ) were measured for the second and third time after two and seven days, respectively. The peaks of loss factor (tan δ) appeared at 59.81 ± 1.86 °C and 95.96 ± 1.67 °C after two-day-storage, but only one peak appeared at 85.46 ± 5.50 °C after seven days. A shifting trend from higher to lower temperature for loss factor was observed after seven days.     

Preparation and properties of glycerol plasticized-pea starch/zinc oxide-starch bionanocomposites

A bionanocomposite was cast using ZnO nanoparticles stabilized by soluble starch (nano-ZnO) as filler in a glycerol plasticized-pea starch (GPS) matrix. According to the characterization of nano-ZnO particles by Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG) and transmission electron microscopy (TEM), ZnO nanoparitlces (70 wt%) were encapsulated by starch (30 wt%) in nano-ZnO particles of about 10 nm. In GPS/nano-ZnO nanocomposites, loading a low level of nano-ZnO particles improved the pasting viscosity, storage modulus, glass transition temperature and UV absorbance. When the nano-ZnO content varied from 0 to 4 wt%, the tensile yield strength and Young’s modulus increased from 3.94 to 10.80 MPa and from 49.80 to 137.00 MPa, respectively. The water vapor permeability decreased from 4.76 × 10^?10 to 2.18 × 10^?10 g m^?1 s^?1 Pa^?1. The improvement in these properties may be attributed to the interaction between the nano-ZnO filler and GPS matrix.     

Ultrasonographic imaging of the reproductive tract and surgical recovery of oocytes in Cebus apella (capuchin monkeys)

Two-dimensional real-time and Doppler ultrasonography are valuable non-invasive methods to assess reproductive anatomy and physiology. In adult, postpubertal female Cebus apella (capuchin monkeys), the objectives were to determine (1) uterine and ovarian dimensions, ovarian follicular dynamics, day of ovulation, and arterial blood flow of uterus and utero-ovarian ligament during the follicular phase of the menstrual cycle and (2) the number of oocytes aspirated from antral follicles at laparotomy. Based on two-dimensional, transabdominal B-mode ultrasonography, mean (± S.E.M.) length, height, width, and volume of the uterus were 17.9 ± 0.4, 12.4 ± 0.3, 13.6 ± 0.3 mm, and 1.55 ± 0.08 mL, respectively, and of the ovary were 13.4 ± 0.2, 8.2 ± 0.1, 7.7 ± 0.1 mm, and 4.5 ± 0.2 mL. Ovarian follicles were monitored for 6 days before ovulation, which occurred on day 9.3 ± 0.5 (range, days 7–11; day 1 = start of menses), with 10 of 12 ovulations in the right ovary. Diameter and volume of the preovulatory follicle were 10.1 ± 0.2 mm and 0.55 ± 0.03 mL (on the estimated day of ovulation) and of the CL were 8.1 ± 0.4 mm and 0.3 ± 0.05 mL. Resistivity and pulsatility indices were 0.86 ± 0.02 and 2.15 ± 0.11 for uterine arteries, and were 0.69 ± 0.04 and 1.63 ± 0.15 for the utero-ovarian ligament (UOL) artery; just prior to ovulation, both indices peaked (P < 0.05) in the uterine artery ipsilateral to the side of ovulation, but both reached a nadir (P < 0.05) in the UOL artery. In the absence of ovarian stimulation, 31 oocytes (diameter, 137 ± 10 μm) were aspirated (average of 2 oocytes/(female attempt)) on days 5, 7, and 9. In conclusion, transabdominal ultrasonography facilitated assessment of reproductive anatomy and physiology in C. apella adult females. Resistance and pulsatility indices of uterine and UOL arteries changed near the time of ovulation. Dominant follicles were easiest to aspirate at 8–9 mm in diameter (∼day 9), with intact cumulus-oocyte complexes recovered from ovarian follicles 2–9 mm in diameter.     

Acute effect of heel-drop exercise with varying ranges of motion on the gastrocnemius aponeurosis-tendon’s mechanical properties

The objectives of this study was to investigate the acute effects of various magnitudes of tendon strain on the mechanical properties of the human medial gastrocnemius (MG) in vivo during controlled heel-drop exercises. Seven male and seven female volunteers performed two different exercises executed one month apart: one was a heel-drop exercise on a block (HDB), and the other was a heel-drop exercise on level floor (HDL). In each regimen, the subjects completed a session of 150 heel-drop exercises (15 repetitions × 10 sets; with a 30 s rest following each set). Before and immediately after the heel-drop exercise, the ankle plantar flexor torque and elongation of the MG were measured using a combined measurement system of dynamometry and ultrasonography and then the MG tendon strain and stiffness were evaluated in each subject. The tendon stiffness measured prior to the exercises was not significantly different between the two groups 23.7 ± 10.6 N/mm and 24.1 ± 10.0 N/mm for the HDB and HDL, respectively (p > .05). During the heel-drop exercise, it was found that the tendon strain during the heel-drop exercise on a block (8.4 ± 3.7%) was significantly higher than the strain measured on the level floor (5.4 ± 3.8%) (p < .05). In addition, the tendon stiffness following the heel-drop exercise on a block (32.3 ± 12.2 N/mm) was significantly greater than the tendon stiffness measured following the heel-drop exercise on the level floor (25.4 ± 11.4 N/mm) (p < .05). The results of this study suggest that tendon stiffness immediately following a heel-drop exercise depends on the magnitude of tendon strain.